JP2736995B2 - Magnetic toner and developing method using the toner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image in electrophotography, electrostatic recording, and the like, and a developing method using the toner.

[Prior Art] Conventionally, as a dry toner used for electrophotography and the like, a two-component toner using a carrier and a one-component toner containing a magnetic component have been known. One-component magnetic toners have been widely used because the developing device can be simplified and maintenance is easy.

Generally, the following method is used in manufacturing a magnetic toner.

The magnetic material, binder resin, charge control agent, etc. are uniformly mixed with a mixer such as a ball mill or Henschel mixer, and then melt-kneaded using a kneader such as a roll mill, extruder, kneader, etc., and the components are sufficiently dispersed. Let it. Thereafter, the powder is finely pulverized with a jet mill or the like and classified using an air classifier or the like to obtain a magnetic toner.

Further, in order to improve the dispersion of the magnetic substance in the binder resin, there has been proposed a method of treating the surface of the magnetic substance with various substances for the purpose of increasing the compatibility of the magnetic substance with organic substances. For example, JP-A-53-137148 discloses fatty acids and derivatives thereof, and JP-A-53-81125 discloses polymer materials,
JP-A-54-127329 discloses a silane coupling agent,
JP-A-55-28019 discloses a titanium coupling agent. These are excellent in improving the compatibility.

However, in the magnetic toner, the magnetic material is exposed to the toner surface to a certain extent and releases an excessively charged electric charge, thereby playing a role of adjusting the charge amount to an appropriate amount. Therefore, when the magnetic material treated as described above is used, the hydrophilicity of the magnetic material surface is lost, the polarization is increased, the release of electric charge is inhibited, the toner becomes excessively charged, the toner scatters on the image, and the roughness is reduced. May occur. Further, there is a possibility that the reflection force on the developing sleeve becomes strong, causing a decrease in density, or an unevenness in the sleeve coat. This phenomenon becomes remarkable in low-humidity and high-speed machines, and it is inevitable that image defects occur.

On the other hand, various magnetic materials are manufactured to obtain desired magnetic characteristics, electrical characteristics, and powder characteristics, but some of them do not discharge electric charges sufficiently. Although the degree is lighter, there are many magnetic substances that cause image defects.

Further, as a method for improving the dispersion of a magnetic material,
JP-A-125749, JP-A-59-126544, JP-A-59-125
No. 747, JP-A-59-125748, JP-A-59-125749
JP-A-59-125750 and JP-A-61-59349 disclose surfactants. These things are
It is excellent in improving the compatibility, and even under low humidity, the chargeability is stable and a good image is provided. However, although it has moisture resistance in that it does not undergo irreversible changes under high humidity, it tends to increase the release of electric charges and often causes a decrease in concentration.

On the other hand, in recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, the uses thereof have also been diversified, and requirements for image quality have become strict. 2. Description of the Related Art In copying images such as ordinary documents and books, it is required to reproduce very finely and faithfully without crushing or breaking even fine characters. In particular, when the latent image on the photoreceptor of the image forming apparatus is a line image having a size of 100 μm or less, thin line reproducibility is generally poor, and the sharpness of the line image is not yet sufficient. Recently, in an image forming apparatus such as an electrophotographic printer using a digital image signal, a latent image is formed by collecting dots of a constant potential, and a solid portion, a halftone portion, and a light portion have a dot density. Is expressed by changing However, in a state where the toner particles do not adhere to the dots and the toner particles protrude from the dots, it is not possible to obtain the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image. There is a problem. Further, when the resolution is improved by reducing the dot size in order to improve the image quality, the reproducibility of a latent image formed from minute dots becomes more difficult, and the resolution and gradation are poor. Images tend to be poor.

Although the image quality is good at the beginning, the image quality may deteriorate while copying or printing out is continued. It is considered that this phenomenon occurs because only toner particles which are easily developed are consumed first while copying or printing is continued, and toner particles having poor developability accumulate and remain in the developing machine.

Heretofore, some developers have been proposed for the purpose of improving image quality. JP-A-51-3244 proposes a non-magnetic toner intended to improve image quality by regulating the particle size distribution. In the toner, 8 to
The main component is a toner having a particle size of 12 μm, which is relatively coarse. According to the study of the present inventors, it is difficult to achieve “density” on a latent image with a particle size of 30 μm.
The characteristic that the particle size distribution is not more than 5% by number is not more than 20% and the particle size distribution is broad, which tends to lower the uniformity. In order to form a clear image using such a coarse toner particle and a toner having a broad particle size distribution, it is necessary to fill the gap between the toner particles by thickly overlapping the toner particles. There is also a problem that it is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density increases.

Japanese Patent Application Laid-Open No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former, but the size of particles having an intermediate weight is as coarse as 8.5 to 11.0 μm, and high resolution is obtained. However, there is still room for improvement as a toner.

JP-A-58-129437 discloses that the average particle size is 6 to 10 μm.
Non-magnetic toners having the largest number of particles of 5 to 8 μm have been proposed, but the number of particles of 5 μm or less is as small as 15% by number or less, and an image lacking sharpness tends to be formed.

According to the study of the present inventors, it has been found that toner particles having a size of 5 μm or less clearly reproduce the outline of the latent image and have a main function of dense toner adhesion to the entire latent image. Particularly, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contoured edge portion has a stronger electric field strength than the inside, and the sharpness of the image quality is determined by the quality of the toner particles collected in this portion. According to the study of the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality.

However, by reducing the particle size of the toner, the unit surface area per unit weight of the toner particles is increased, so that the charge amount per toner particle is increased. Therefore, as the particle size is reduced, the amount of charge of the magnetic toner due to frictional charging increases, and the magnetic toner gradually becomes excessively charged.

Therefore, simply reducing the particle size of the conventionally used magnetic toner tends to be excessively charged, and when used under low humidity, the charge amount further increases, and the fog increases, It may scatter and cause a decrease in image density. Even a magnetic toner having a small and uniform particle diameter, which is advantageous for sleeve coat unevenness, may cause sleeve coat unevenness under severe use conditions. Further, in order to reduce the particle size, it is required to further improve the dispersibility of the magnetic substance.

From the above, a toner that gives a good image under any environment is required. That is, there is a need for a magnetic toner that can disperse a magnetic material having desired characteristics in a binder resin, can effectively adjust the charge amount, is excellent in reproducibility of a latent image, and gives a high-resolution image.

[Problem to be Solved by the Invention] The object of the present invention is not affected by the environment such as temperature and humidity.
In particular, it is an object of the present invention to provide a toner that provides a stable image under low humidity.

Another object is to provide a toner that realizes high image quality such as high resolution.

Still another object is to provide a toner which makes it possible to disperse a magnetic substance in a resin in a good manner, has excellent durability, and always provides a stable image without fogging even after long-term continuous use. .

Still another object is to provide a magnetic toner which does not impair the fixability and offset resistance of the binder resin.

[Means and Actions for Solving the Problems] As a result of intensive research for the above-described object, the present inventors have found that a magnetic substance having a specific compound adsorbed on its surface is used to make a magnetic toner having a specific particle size distribution. It has been found that the chargeability of the toner is stabilized, the dispersion of the magnetic substance in the resin is improved, and the environmental stability and durability are excellent.

Specifically, the present invention relates to a magnetic toner having at least a magnetic substance having a compound represented by the following general formula (1) adsorbed thereon and a binder resin, wherein magnetic toner particles having a particle diameter of 5 μm or less are used. Magnetic toner particles having a particle size of 8 to 12.7 μm are contained in an amount of 33% by number or less, magnetic toner particles having a particle size of 16 μm or more are contained in an amount of 2% by volume or less. A magnetic toner having a volume average particle size of 4 to 10 μm.

About.

Further, according to the present invention, an electrostatic image holding member for holding an electrostatic charge image on a surface thereof and a toner holding member for holding a magnetic toner on the surface are arranged with a certain gap in a developing section, and the magnetic toner is placed on the toner holding member. The upper part is regulated to a thickness smaller than the gap and transported to the developing unit,
This is a developing method in which the toner is developed while applying an alternating electric field to the toner in the developing section. A magnetic toner having at least a magnetic substance adsorbing a compound represented by the formula and a binder resin, containing at least 12% by number of magnetic toner particles having a particle diameter of 5 μm or less;
33% by number or less of magnetic toner particles having a particle diameter of 12.7 μm, 2% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more, and a volume average particle diameter of the magnetic toner of 4 to 10 μm. The present invention relates to a developing method, wherein the toner is a magnetic toner. Hereinafter, the present invention will be described in more detail. In the following description, "%" and "parts" representing the quantitative ratios are based on weight unless otherwise specified.

In the magnetic toner of the present invention, a magnetic substance having a compound represented by the general formula (1) adsorbed on the surface is used.

These compounds consist of an alkyl group serving as a hydrophobic group and an imidazolinium salt serving as a hydrophilic group. Specifically, the following compounds are exemplified.

In general, many compounds exhibiting hydrophilicity and hydrophobicity are known, but when adsorbed on a magnetic material, many of them do not release effective charges and become overcharged, or absorb moisture excessively and excessively. Emission occurs, and the charge shortage becomes remarkable.

In the compound of the present invention, the imidazolinium salt, which is a hydrophilic group, facilitates adsorption on a magnetic substance. In addition, it is considered that these functional groups suppress the polarization of the surface of the magnetic material and supplement the effective release of electric charge.

On the other hand, since the hydrophobic alkyl group of the compound of the present invention spreads on the surface of the magnetic material, the compatibility with the binder resin and the like is improved, and the dispersibility of the magnetic material in the toner is improved. It is considered that moisture absorption is also suppressed.

Although the magnetic toner containing the magnetic substance adsorbing these compounds does not absorb much moisture, the release of electric charge increases under high humidity, and the magnetic toner may not be able to maintain good developability. Poor charging may result in a decrease in image density. However, the above-mentioned drawbacks can be overcome and the object of the present invention can be achieved by making the magnetic toner containing the magnetic substance characteristic of the present invention have the particle size distribution described below. That is, by defining the magnetic toner in the particle size distribution of the present invention, the charge amount is increased, the friction with the frictional charging member is increased, the magnetic toner charging ability is improved, and the effect of the magnetic material used in the present invention is improved. What makes it noticeable. Further, when the particle diameter of the magnetic toner is reduced, the toner tends to be overcharged. Therefore, the magnetic material of the present invention has a role of controlling the charge amount of the magnetic toner. That is, the magnetic material of the present invention is suitable for use in a magnetic toner having a small particle diameter.

On the other hand, with respect to the particle size, in the magnetic toner of the present invention, 5
One feature is that the number of magnetic toner particles having a particle size of not more than μm is 12% by number or more. Conventionally, in a magnetic toner, it has been difficult to control the charge amount of magnetic toner particles of 5 μm or less, and the charge tends to be excessive. For this reason, the toner particles having a size of 5 μm or less have a strong reflection force on the developing sleeve or the like and are fixed to the surface of the sleeve, thereby inhibiting the triboelectric charging of other particles, generating poorly charged toner particles, sticking, and lowering the density. It was thought that it was necessary to decrease positively.

However, studies by the present inventors have revealed that magnetic toner particles having a size of 5 μm or less are essential components for forming high-quality images.

For example, using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm, the surface potential on the photoreceptor is changed, and from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, and further, a very small amount. A latent image with a changed surface potential on the photoreceptor was developed to a small development potential contrast where only toner particles were developed, and the developed toner particles on the photoreceptor were collected. The toner particle size distribution was measured. It has been found that there are many magnetic toner particles, especially magnetic toner particles of 5 μm or less. That is, when magnetic toner particles having a particle size of 5 μm or less, which are most suitable for development, are smoothly supplied to the development of the latent image on the photoreceptor, the toner is faithful to the latent image and does not protrude from the latent image, and is truly reproducible. And an image excellent in the above is obtained.

The magnetic toner containing the magnetic material of the present invention appropriately controls the charging of the magnetic toner particles of 8 μm or less, particularly 5 μm or less, and effectively exerts the above-described effects.

Further, in the magnetic toner of the present invention, 8 to 12.7 μm
One of the features is that the number of particles in the range is 33% by number or less. This is related to the need for the presence of magnetic toner particles having a particle size of 5 μm or less, as described above. The magnetic toner particles having a particle size of 5 μm or less strictly cover the latent image and have an ability to faithfully reproduce the latent image. However, in the latent image itself, the electric field strength of the peripheral edge portion is higher than that of the central portion, so that the inside of the latent image has a smaller toner particle glue than the edge portion,
The image density may appear faint. In particular, magnetic toner particles of 5 μm or less have a strong tendency. However, the present inventors have solved this problem by including 33% by number or less of toner particles in the range of 8 to 12.7 μm,
It was found that it could be made clearer. That is, 8 to 1
It is considered that the toner particles having a particle size of 2.7 μm have a moderately controlled charge amount with respect to the magnetic toner particles having a particle size of 5 μm or less. To form a uniform developed image by compensating for the small amount of toner particles on the inner side with respect to the edge portion. As a result, a sharp image with high resolution and excellent gradation is provided at a high density. Is what is done.

In the case of particles having a particle diameter of 5 μm or less, if the number is 12 to 60% by number, N / V = −0.04N + k (provided that 4.5 ≦ It is also preferred that the magnetic toner of the present invention satisfies the following relationship: k ≦ 6.5; 12 ≦ N ≦ 60). The magnetic toner of the present invention having a particle size distribution satisfying this range can achieve more excellent developability.

The present inventors have studied the state of the particle size distribution of 5 μm or less and found that there is a state of existence of the fine powder most suitable for achieving the object as shown by the above formula. That is,
For a certain N value of 12 ≦ N ≦ 60, a large N / V indicates that the particles widely include particles of 5 μm or less, and a small N / V indicates that the particles have a particle diameter of about 5 μm. It is understood that the abundance of particles is high, indicating that there are few particles with a particle size smaller than that, and when N is in the range of 12 to 60, the value of N / V is in the range of 2.1 to 5.82. If the above relational expression is further satisfied, good fine line reproducibility and high resolution can be achieved.

Further, for magnetic toner particles having a particle size of 16 μm or more, the content is preferably set to 2.0% by volume or less, and as small as possible.

The magnetic toner of the present invention solves the problems of the magnetic substance used in the present invention, and can withstand recent severe demands for high image quality.

 The configuration of the present invention will be described in more detail.

The number of magnetic toner particles having a particle size of 5 μm or less is preferably 12% by number or more of the total number of particles, and more preferably 12 to 60% by number. When the number of magnetic toner particles having a particle diameter of 5 μm or less is less than 12% by number, the number of magnetic toner particles effective for high image quality is small.
In particular, as the toner is used by continuing to copy or print out, the effective magnetic toner particle component decreases, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually decreases. Come.
On the other hand, if the content exceeds 60% by number, the 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, or an edge portion of the latent image. In some cases, the density difference between the image and the inside becomes large, and the image may be slightly hollow.

The number of particles in the range of 8 to 12.7 μm is preferably 33% by number or less, more preferably 1 to 33% by number. If the content is more than 33% by number, the image quality is deteriorated, and the development is performed more than necessary, that is, the toner is excessively applied, thereby increasing the toner consumption. On the other hand, if it is less than 1% by number, it may be difficult to obtain a high image density. The number% (N%) and the volume% of the magnetic toner particles having a particle size of 5 μm or less
(V%), there is a relationship of N / V = −0.04N + k, and 4.
Indicates a positive number in the range of 5 ≦ k ≦ 6.5. Preferably 4.5 ≦ k ≦
6.0. As indicated above, 12 ≦ N ≦ 60.

When k <4.5, the number of magnetic toner particles having a particle diameter smaller than 5.0 μm is small, and the image density, resolution, and sharpness tend to be poor. The appropriate presence of fine magnetic toner particles, which was conventionally considered unnecessary, contributes to the closest packing of the toner in development and contributes to the formation of a uniform image without roughness. In particular, by uniformly filling the fine lines and the contours of the image, the sharpness is further enhanced visually. That is, when k <4.5, these properties tend to be inferior due to the lack of the particle size distribution component.

From another point of view, in terms of production, the conditions such as classification tend to be strict to satisfy the condition of k <4.5, which is disadvantageous in terms of yield and toner cost. Also, k> 6.5
Then, due to the presence of more fine powder than necessary, the balance of the particle size distribution is disrupted as the copying is continued, and the degree of aggregation of the toner is increased, and the triboelectric charging is not effectively performed, resulting in poor cleaning and fogging. Sometimes.

The content of the magnetic toner particles having a particle diameter of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume.
Or less, more preferably 0.5% by volume or less.
When the content is more than 2.0% by volume, not only does it hinder the reproduction of fine lines, but also in the transfer, coarse toner particles of 16 μm or more protrude from the thin layer surface of the toner particles developed on the photoreceptor. The delicate state of contact between the photoreceptor and the transfer paper via the layer is made irregular, causing fluctuations in the transfer conditions and causing poor transfer images.

In addition, the magnetic toner of the present invention cannot sufficiently maintain the charge of the magnetic toner particles having a size of 16 μm or more, resulting in poor charging and fogging of the background portion and the reversal portion.

The volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 to 10 μm.
.About.9 .mu.m, and this value cannot be considered separately from the components described above. If the volume average particle size is less than 4 μm, the amount of toner applied on the transfer paper is small for applications having a high image area ratio such as graphic images,
The problem of low image density is likely to occur. This is considered to be due to the same reason as described above for lowering the density inside the edge portion of the latent image. Volume average particle size
If it exceeds 10 μm, the resolution is not good at the above, and the image quality is liable to deteriorate at the beginning of copying, if it is used at best. Further, the image density tends to decrease under high humidity.

The magnetic toner of the present invention having a specific particle size distribution can faithfully reproduce even a fine line of a latent image formed on a photoreceptor, and reproduces a dot latent image such as a halftone dot and a digital image. And an image excellent in gradation and resolution. Furthermore, high image quality can be maintained even when copying or printing out is continued, and even in the case of high-density images, good development can be performed with less toner consumption than conventional magnetic toners. Also, there is an advantage in downsizing the copying machine or the printer body.

As described above, the magnetic toner of the present invention uses a magnetic substance to which a specific substance is adsorbed, and has a specific particle size distribution, thereby stabilizing chargeability, and being excellent in environmental stability and durability. I found

Further, since the magnetic toner of the present invention has a good dispersion of a magnetic substance, it is excellent in durability and gives an image with very little fog, which is preferable for decreasing the toner particle size.

The amount of the compound of the general formula (1) used in the present invention is determined by the binder resin, the magnetic substance, the presence or absence of additives used as necessary, the method of adsorption to the magnetic substance, and the method of producing the toner. However, it is not limited uniquely. The preferred amount is in the range of 0.01 to 5 parts (more preferably 0.1 to 3 parts) based on 100 parts of the magnetic material. When the amount used is less than 0.01 part, the effect of charge release is not effectively exhibited, and when the amount is more than 5 parts, the charge release becomes excessive, poor charging under high humidity may cause a decrease in image density. is there.

The amount of the magnetic material of the present invention contained in the toner is 20 to 150 parts, preferably 40 to 120 parts, per 100 parts of the resin component.

Although it is smaller than the effect of the present invention, in order to achieve the same object as the present invention, means for increasing the content of the magnetic substance may be considered. In this case, since the ratio of the magnetic material is increased, the fixing property is adversely affected, and there is a disadvantage that a low-temperature offset occurs. There is also a disadvantage that the organic photoreceptor is easily damaged. Further, there is a drawback that the toner is strongly subjected to the magnetic restraining force and the developability is reduced, thereby causing image defects such as a decrease in image density and roughness, and a deterioration in image quality.

On the other hand, the magnetic toner of the present invention effectively releases electric charges, has a stable charge amount, and has a very small fog, so that the magnetic material content can be reduced. Therefore, the effect of the magnetic binding force is reduced, and the image quality can be improved, such as high density, no tailing, good resolution, and no roughness. In addition to good dispersibility, fixability,
This is advantageous for low-temperature offset resistance, and allows the performance of the binder resin to be sufficiently exhibited. Further, since the organic photosensitive layer and the like are not excessively damaged, it is preferably used for a model using an organic photosensitive member and the like.

The magnetic toner of the present invention exerts its effects more effectively as the toner particle diameter is reduced for the following reasons.
For example, in the case of a magnetic toner, when the particle size is reduced, there are disadvantages such as an increase in fog and image defects due to excessive charging. In order to solve such a drawback, a measure for increasing the content of the magnetic substance is taken, but the above-mentioned adverse effects are caused. Further, as the particle size of the toner becomes smaller, the defect becomes larger. Therefore, the content of the magnetic material must be increased, and the harmful effects become larger. However, since the magnetic toner of the present invention can reduce the content of the magnetic substance, the adverse effects can be suppressed. The effect of the magnetic toner of the present invention can be sufficiently exhibited when the average volume particle diameter is 10 μm or less, particularly 9 μm or less, and the effect can be expected to increase as the particle diameter decreases.

According to the knowledge of the present inventors, when the particle diameter is reduced or the content of the magnetic substance is reduced, the magnetic brush on the toner carrier becomes short and dense. (Large) High-precision development is performed, and since the latent image reproducibility is excellent, high image quality can be obtained. The magnetic toner of the present invention can achieve both of these at the same time, so that a better image quality can be obtained.

Although the particle size distribution of the toner can be measured by various methods, in the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-II type (manufactured by Coulter, Inc.) is connected to an interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution, and a CX-1 personal computer (manufactured by Canon). Prepare a% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
Dispersion treatment for minutes, and the Coulter Counter TA-II
According to the mold, the particle size distribution of particles of 2 to 40 μ was measured on the basis of the number, using a 100 μ aperture as the aperture, and then the value according to the present invention was determined.

As a binder resin used in the toner of 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, polystyrene, poly-p-chlorostyrene,
Styrenes such as polyvinyltoluene and their substituted homopolymers; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene -Methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone Styrene-based copolymers such as copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally-modified phenolic resins, and natural-resin-modified malees Acid resin, Acrylic Resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethane, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resin, coumarone-indene resins, and petroleum resins.

In the heat and pressure roller fixing method in which almost no oil is applied, the so-called 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. Toners that fix with less heat energy tend to block or cake during storage or in a developing unit, and these problems must also be considered at the same time. The physical properties of the binder resin in the toner are most greatly involved in these phenomena. However, according to the study of the present inventors, when the content of the magnetic substance in the toner is reduced, the toner image supporting member is fixed at the time of fixing. Although the adhesiveness of the toner to the toner becomes better, the inherent properties of the binder resin tend to appear, offset tends to occur, and blocking or caking may occur. 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 binders include crosslinked styrenic copolymers or crosslinked polyesters.

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

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene, or the like; for example, ethylene glycol diacrylate, ethylene glycol diacrylate, or the like. Double bonds such as methacrylate, 1,3-butanediol dimethacrylate
Carboxylic acid esters having two or more compounds; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups are used alone or as a mixture.

When a 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, ethylene-vinyl acetate copolymer can be used. Coalescent, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

As a magnetic material contained in the magnetic toner of the present invention, magnetite, maghematite, iron oxides such as ferrite,
And iron oxides containing other metal oxides; metals such as Fe, Co, Ni, or these metals and Al, Co, Cu, Pb, Mg, Ni, Sn, Z
Examples include alloys with metals such as n, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, and V, and mixtures thereof.

It is desirable that these ferromagnetic materials have an average particle diameter of about 0.1 to 2 μm, a magnetic property at 10 Ke applied of a coercive force of 20 to 150 e, a saturation magnetization of 50 to 200 emu / g, and a residual magnetization of 2 to 20 emu / g.

In the magnetic toner of the present invention, it is preferable to use a charge control agent internally or externally added to the toner. On the other hand, since the magnetic toner of the present invention stabilizes the charge, the selection range of the charge control agent is wide. As the positive charge control agent used in the present invention, known agents can be used.For example, nigrosine and a modified product thereof with a fatty acid metal salt, a quaternary ammonium salt,
Diorganotin oxide, diorganotin borate and the like can be used alone or in combination of two or more. Of these, nigrosine and quaternary ammonium salts are particularly preferably used.

Also, the general formula Monomers of monomers represented by, or copolymers with polymerizable monomers such as styrene, acrylates, and methacrylates as described above can be used as the positive charge control agent. It also has a function as (part of or all of) the resin.

On the other hand, as the negative charge control agent used in the present invention, known agents can be used. For example, carboxylic acid derivatives and metal salts thereof, alkoxylates, organometallic complexes, chelate compounds and the like can be used alone or in combination of two or more. . Among these, acetylacetone metal complexes, salicylic acid metal complexes, and monoazo metal complexes are particularly preferably used.

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. A magnetic toner having a particle size distribution as a feature of the present invention has a larger specific surface area than conventional toners. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means inside due to triboelectric charging, the number of times of contact between the surface of the toner particles and the sleeve increases compared to conventional magnetic toner, and the toner Abrasion of particles and contamination of the sleeve surface are likely to occur. When the magnetic toner according to the present invention is combined with silica fine powder, wear is significantly reduced because the silica fine powder is interposed between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be prolonged, and a stable chargeability can be maintained, and a developer having a magnetic toner that is more excellent for long-term use can be obtained. further,
The magnetic toner particles having a particle size of 5 μm or less, which play a major role in the present invention, exhibit more effects in the presence of the silica fine powder, and can stably provide high-quality images.

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

The dry method referred to here is a method for producing silica fine powder generated by vapor phase oxidation of a silicon halide. For example, in a method utilizing the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen-hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl Also, in this manufacturing process, by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide, a composite fine powder of silica and another metal compound is obtained. Is also possible and encompasses them.

On the other hand, as a method for producing the silica fine powder used in the present invention by a wet method, various conventionally known methods can be applied. For example, the decomposition of sodium silicate with an acid is represented by the following general reaction formula.

Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl In addition, decomposition of sodium silicate with ammonium salts or alkali salts, formation of alkaline earth metal silicate from sodium silicate, and decomposition with acid Silicate, a method in which a sodium silicate solution is converted into silicate using an ion exchange resin, a method in which natural silicate or silicate is used, and the like.

Silica such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate, etc. can be applied to the silica fine powder here, in addition to anhydrous silicon dioxide (silica).

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

Further, when the magnetic toner of the present invention is positively chargeable, the silica fine powder to be added for preventing abrasion of the toner and preventing the surface of the sleeve from being stained may be more positively chargeable silica than negatively chargeable. The use of fine powder is preferred without impairing the charging stability.

As a method of obtaining the positively chargeable silica fine powder, a method of treating the untreated fine silica powder with a silicon oil having an organo group having at least one nitrogen atom in a side chain, or a nitrogen-containing silane cup There is a method of treating with a ring agent or a method of treating with both.

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

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

(Wherein R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represent a hydrogen, an alkyl group, or an aryl group; ₅ represents a nitrogen-containing heterocyclic group) The above alkyl group,
The aryl group, alkylene group and phenylene group may have an organo group having a nitrogen atom, or may have a substituent such as halogen as long as the chargeability is not impaired.

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

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

Examples of the saturated heterocyclic group include the following.

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

Examples of such treating agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-
γ-propylphenylamine, trimethoxysilyl-γ
-Propylbenzylamine and the like, and the nitrogen-containing heterocycle may have the structure described above. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, And trimethoxysilyl-γ-propylimidazole.

The applied amount of these treated positively charged silica fine powders is 0.01 to 8 with respect to 100 parts by weight of the positively charged magnetic toner.
The effect is exhibited when the amount is by weight, and particularly preferably 0.1 to 5 parts by weight.
Positive chargeability with excellent stability when added in parts by weight. In a preferred embodiment, the addition form is such that 0.1 to 3 parts by weight of the treated silica fine powder is attached to the surface of the toner particles based on 100 parts by weight of the positively charged magnetic toner. The untreated silica fine powder described above can be used in the same application amount.

Further, the silica fine powder used in the present invention is treated with a silane coupling agent, a treating agent such as silicon oil or an organosilicon compound for the purpose of hydrophobizing, if necessary, or a combination of various treating agents. It may be treated with the treating agent that reacts or physically adsorbs with the silica fine powder.
Examples of such a treating agent include hexamethyldisilazane, trimethylsilane, tritylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and bensyldimethylchlorosilane. , Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyl Dimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-di Examples include phenyltetramethyldisiloxane and dimethylpolysiloxane having from 2 to 12 siloxane units per molecule, with each terminal unit containing one hydroxyl group bonded to Si.

The silicone oil is generally represented by the following formula.

Preferred silicone oils are those having a viscosity of about 5 to 5000 cSt at 25 ° C. For example, methyl silicone oil, dimethyl silicone oil, phenylmethyl silicone oil, chlorophenylmethyl silicone oil, alkyl-modified silicone oil, and fatty acid-modified silicone oil And polyoxyalkylene-modified silicone oils. These are used alone or as a mixture of two or more.

Further, in the present invention, fine powder of a fluorine-containing polymer,
For example, it is preferable to add fine powder of polytetrafluoroethylene, polyvinylidene fluoride or the like and a tetrafluoroethylene-vinylidene fluoride copolymer. In particular, polyvinylidene fluoride fine powder is preferred in terms of fluidity and abrasiveness. The amount added to the toner is 0.
01 to 2.0 wt%, particularly preferably 0.02 to 1.0 wt%.

In particular, in the magnetic toner in which the silica fine powder and the above fine powder are combined, the reason is not clear, but stabilizes the state of silica attached to the toner, for example, the attached silica is released from the toner, The effect on abrasion and sleeve fouling is not reduced, and the charging stability can be further increased.

The magnetic toner of the present invention may optionally contain additives. Other additives include lubricants such as, for example, zinc stearate, abrasives such as cerium oxide and silicon carbide, or fluidity-imparting agents such as, for example, aluminum oxide, and anti-caking agents.

Further, in order to improve the releasability at the time of hot roll fixing, a wax-like substance such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, sasol wax, paraffin wax, etc.
Addition of about 5 wt% to the magnetic toner is also a preferred embodiment of the present invention.

In the present invention, as a method for adsorbing the compound used in the present invention on a magnetic material, there are the following methods.

(1) A method in which each component of the toner is added when mixed, and is adsorbed on the surface of the magnetic material during mixing and kneading.

However, in this method, the effect may be reduced or excessive moisture absorption may occur due to permeation into the binder resin or excessive exposure of the hydrophilic group.

In addition, there is a possibility that adsorption is not effectively performed on the surface of the magnetic body.

Therefore, in order to efficiently adsorb to the magnetic material and to effectively achieve the object of the present invention, it is preferable to previously adsorb to the magnetic material, and the following methods are available.

(2) A dry method in which a compound used in the present invention is added to a magnetic substance, and then mixed and adsorbed by a Henschel mixer or a fret mill.

(3) A wet method in which the compound used in the present invention and a magnetic substance are dispersed and adsorbed in water or an organic solvent, and then dried and dried.

A simple method is a dry method, but
In order to make the magnetic substance surface more uniformly adsorbed, a wet method is excellent, and a method using water as a solvent is most preferable from the viewpoint of safety and ease of production.

In producing the toner according to the present invention, the above-mentioned toner constituent materials are sufficiently mixed by a ball mill or other mixer, then kneaded well using a hot kneader of a hot roll kneader or an extruder, and cooled and solidified. , Mechanical pulverization, a method of obtaining a toner by classification, is preferred,
Another method is to obtain a toner by dispersing the constituent materials in a binder resin solution and then spray-drying; or a method of mixing a predetermined material with a monomer to form the binder resin and emulsifying a suspension. And then polymerizing the toner to obtain a toner; or a method in which a so-called microcapsule toner comprising a core material and a shell material contains a predetermined material in the core material, the shell material, or both. Method can be applied.

Further, if necessary, the desired additives are sufficiently mixed by a mixer such as a Henschel mixer to produce the magnetic toner according to the present invention.

The magnetic toner of the present invention can be all used by a conventionally known means for one-component development for visualizing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing and the like.

The magnetic toner of the present invention is preferably applied to an image forming method of developing a latent image while flying toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoconductor. That is, the magnetic toner is provided with a triboelectric charge mainly by contact with the surface of the sleeve, and is coated in a thin layer on the surface of the sleeve. The thickness of the thin layer of the magnetic toner is formed to be smaller than the gap between the photosensitive member and the sleeve in the developing area. When developing the latent image on the photoconductor, it is preferable to fly the magnetic toner having triboelectric charge from the sleeve to the photoconductor while applying an alternating electric field between the photoconductor and the sleeve.

Examples of the alternating electric field include a pulsed electric field, an AC bias, and a combination of an AC and a DC bias.

On the other hand, as a method of uniformly coating the magnetic toner on the toner carrier (sleeve), the surface is sandblasted with irregularly shaped particles to form a rough surface having a specific unevenness, thereby using a method. An excellent developing device that can maintain a good toner coated state over a long period of time without any uniform unevenness on the surface of the toner carrier can be provided. The intended surface is one in which countless fine cuts or projections are formed in random directions.

However, in a developing device using a toner carrier having such a specific surface state, depending on the magnetic toner to be applied, components in the toner are likely to adhere to the surface, so-called contamination on the surface of the toner carrier occurs. As a result, when the density of the initial image is reduced and the contamination is further advanced due to the durability, the image blank is generated in the toner carrier cycle.

This is due to the fact that the components in the toner adhere to the slopes and recesses of the convex portions on the surface of the toner carrier, resulting in poor charging of the magnetic toner particles and a decrease in the charge amount of the toner layer.

Generally, the components in the magnetic toner are composed of materials such as a binder resin magnetic material, a charge control agent, and a release agent. The material is designed so as to prevent contamination on the surface of the material carrier. Currently, the choice is limited.

In the case where the surface of the toner carrier is smooth or has specific irregularities formed by a plurality of spherical trace depressions, the toner may be applied to the surface even if a magnetic toner composed of any material is applied. Components are less likely to adhere, and contamination can be prevented or reduced over a long period of time.

However, as a performance of uniformly coating the toner carrier with the magnetic toner, the toner carrier having a surface on which specific irregularities due to the spherical trace depression are formed,
Compared to a toner carrier having a smooth surface, it is inferior to a toner carrier having an irregular surface with a myriad of fine notches or projections in random directions by sandblasting with irregular shaped particles. Is better.

On the other hand, by using the magnetic toner of the present invention for a toner carrier having a surface with a spherical trace depression, the toner coat layer is prevented from being excessively thick, and the toner carrier having a smooth surface without toner coat unevenness is generated. The toner can be uniformly coated on the body for a long period of time.
Therefore, as a result, it is possible to obtain a clear, high-quality image with high image density, excellent fine line reproducibility and gradation, and no fog over a long period of time.

Hereinafter, the present invention will be specifically described. Hereinafter, the toner carrier is referred to as a sleeve.

In the case where the sleeve in the present invention has a surface having irregularities formed by a plurality of spherical trace depressions, a blasting method using fixed particles can be used as a method for obtaining the surface state. As the shaped particles, for example, various hard spheres such as stainless steel, aluminum, steel, nickel, brass, and other metals having a specific particle size, ceramics, plastics, and glass beads can be used. By blasting the surface of the sleeve with the regular particles having a specific particle diameter, a plurality of spherical trace depressions having substantially the same diameter R can be formed.

In the present invention, the diameter R of the plurality of spherical trace depressions on the sleeve surface is preferably from 20 to 250 μm, and if the diameter R is less than 20 μm, contamination by components in the magnetic toner is undesirably increased. Therefore, it is preferable that the particles having a diameter of 20 to 250 μm are also used in the blasting of the sleeve surface. Further, in the present invention, the pitch P and the surface roughness d of the unevenness of the sleeve surface are measured by measuring the surface of the sleeve using a fine surface roughness meter (a sales agency, Tiller Hopson Co., Ltd., Kosaka Laboratory, etc.), and the surface roughness is measured. D is JIS 10 point average roughness (RZ)
This is based on “JIS B 0601”. The pitch P is determined as follows by counting the peaks having a height of 0.1 μm or more with respect to the convex portion or the concave portions on both sides as one peak and calculating the number of peaks within the reference length of 0.25 mm as follows. It is.

The number of peaks included in 250 (μm) / 250 (μm) In the present invention, the pitch P of the irregularities on the sleeve surface is:
When P is less than 2 μm, sleeve contamination due to components in the magnetic toner is undesirably increased. The surface roughness d of the irregularities on the sleeve surface is 0.1
When d exceeds 5 μm, an alternating voltage is applied between the sleeve and the latent image holding member to cause the magnetic toner to fly from the sleeve side to the latent image surface to perform development. This is not preferable because the electric field tends to be disturbed due to the concentration of the electric field on the uneven portion.

In the present invention, fine line reproducibility was measured by the following method. That is, an image obtained by copying an original original of a fine line accurately having a width of 100 μm under appropriate copying conditions is used as a measurement sample, and using a Luzex 450 particle analyzer as a measuring device, a line width is determined by an indicator from an enlarged monitor image. Measurement. At this time, since the line width measurement position has irregularities in the width direction of the thin line image of the toner, the average line width of the irregularities is used as the measurement point. From this, the value (%) of the fine line reproducibility is calculated by the following equation.

In the present invention, the resolution was measured by the following method. That is, a pattern consisting of five thin lines with the same line width and spacing, and 2.8, 3.2, 3.6, 4.0, 4.5, 5.0,
Create an original image that is drawn as if there were 5.6, 6.3, 7.1 or 8.0 lines. Observe an image obtained by copying the original manuscript with these 10 line images under appropriate copying conditions with a magnifying glass, and determine the resolution value with the number of images (lines / mm) in which fine lines are clearly separated. I do.

 The larger this number is, the higher the resolution is.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples.
This does not limit the invention in any way. All parts in the following formulations are parts by weight. Hereinafter, a production example of the magnetic material used in the present invention will be described.

Production Example 1 A magnetic substance A (magnetic iron oxide) was added to 10 l of an aqueous solution of compound (5) at a concentration of 93.5 g / l in 1.0 g / l of an aqueous solution of 1.0 g / l. And dried by heating to obtain a magnetic material B.

At this time, the adsorption amount of the compound (5) was 0.8 part with respect to 100 parts of the magnetic substance.

Production Example 2 A magnetic material C was obtained in the same manner as in Production Example 1, except that a 1.0 g / l aqueous solution of the compound (6) was used instead of the compound (5).

The amount of adsorption of the compound (6) was 0.8 part with respect to 100 parts of the magnetic substance.

Production Example 3 A magnetic substance D was obtained in the same manner as in Production Example 1, except that a 1.2 g / l aqueous solution of the compound (11) was used instead of the compound (6).

The adsorption amount of the compound (11) was 1.0 part with respect to 100 parts of the magnetic substance.

Production Example 4 A magnetic material F was obtained in the same manner as in Production Example 1, except that a magnetic material E (magnetic iron oxide) was used instead of the magnetic material A.

The amount of adsorption of the compound (5) was 0.8 part with respect to 100 parts of the magnetic substance.

Since the compound of the present invention is distributed at a constant concentration in the solvent, the amount of adsorption is determined by the original solution concentration of the compound and the slurry concentration of the magnetic substance.

When 10 Ke is applied to the magnetic material A, the magnetic properties are 133.
e, the saturation magnetization is 83.7 emu / g, and the residual magnetization is 12.5 emu / g. The average particle size is 0.15 μm.

The magnetic material E has a coercive force of 63 e, a saturation magnetization of 91.8 emu / g,
The residual magnetization is 6.4 emu / g. The average particle size is 0.20 μm.

Example 1 After premixing the above materials with a Henschel mixer, 15
The mixture was kneaded with an extruder heated to 0 ° C, cooled, coarsely pulverized with a cutter mill, pulverized using a fine pulverizer using a jet stream, and further classified using an air classifier to obtain an average volume particle size of 8.24 μm. A classified powder was obtained. No. 1 for particle size distribution
It is shown in the table. To 100 parts of the classified powder, 0.6 part of positively charged hydrophobic colloidal silica (BET 200 m ^{2 /} g) was sufficiently mixed with a Henschel mixer to obtain a magnetic toner. 5000 sheets of the obtained magnetic toner were copied with a commercially available electrophotographic copying machine (trade name: NP-1215, manufactured by Canon Inc., roughness of developing sleeve, diameter of dents 53 to 62 μm, pitch of unevenness 30 μm, surface roughness 2 μm) The results are shown in Table 2.

As is apparent from Table 2, an image having excellent resolution and fine line reproducibility was obtained. Similarly, good results were obtained at 15 ° C., 10% RH, and 32.5 ° C., 85% RH.

The charge amount of the toner on the toner carrier during the test is from +9 to
+11 nc / cm ² .

In the present invention, the charge amount of the toner layer per unit area on the carrier was determined by using a so-called suction Faraday cage method. In this suction-type Faraday cage method, the outer cylinder is pressed against a toner carrier to suck all the toner on a certain area on the carrier, collected by a filter of the inner cylinder, and the toner carrier is increased from the weight increase of the filter. The weight of the toner layer per unit area above can be calculated. At the same time, the charge amount per unit area on the toner carrier can be determined by measuring the charge amount accumulated in the inner cylinder electrostatically shielded from the outside.

Example 2 A toner was produced in the same manner as in Example 1, except that 80 parts of the magnetic substance C was used instead of the magnetic substance B used in Example 1, and 0.5 parts of hydrophobic colloidal silica (BET 300 m ² / g) was used. I got

 Table 1 shows the particle size distribution of the classified powder.

The result of the same copying test as in Example 1 was
It is shown in the table. As shown in Table 2, high quality images faithful to the original were obtained. Similarly, good results were obtained at 15 ° C., 10% RH, and 32.5 ° C., 85% RH.

The charge amount of the toner on the toner carrier during the test was +8
It was stable within the range of ~ + 11 nc / cm ² .

Example 3 A method similar to that of Example 1 except that 90 parts of magnetic substance D was used instead of magnetic substance B used in Example 1, and 0.7 part of positively charged hydrophobic silica (BET 200 m ² / g) was used. As a result, a toner was obtained.

 Table 1 shows the particle size distribution of the classified powder.

Table 2 shows the results of the copy test performed in the same manner as in Example 1. As is clear from Table 2, an image having excellent resolution was obtained. Similarly, good results were obtained at 15 ° C., 10% RH, and 32.5 ° C., 85% RH.

The charge amount of the toner on the toner carrier during the test was +8.
＋+ 9 nc / cm ² .

Example 4 Using the above materials, a classified powder was obtained in the same manner as in Example 1,
0.6 part of hydrophobic colloidal silica (BET 300 m ² / g) was externally added.

 Table 1 shows the particle size distribution of the classified powder.

This toner was purchased from a commercially available electrophotographic copier (product name: NP-7550,
Table 2 shows the results of a 5,000-sheet copy test performed using Canon's developing sleeve with irregular sandblasting. As is clear from Table 2, an image having excellent image quality and toner consumption was obtained.

Similar results were obtained at 15 ° C., 10% RH, and 32.5 ° C., 85% RH. Incidentally charge amount of the toner on the toner carrying member in the test was -7~-12nc / cm ^2.

Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that 80 parts of the magnetic material A was used instead of the magnetic material B.

Table 1 shows the particle size distribution of the classified powder, and Table 2 shows the results of the copy test in the same manner as in Example 1. As is clear from Table 2, good results were obtained. However 15
At 10 ° C. and 10% RH, good images were obtained at the beginning, but as the number of copies increased, the images became slightly rough, fog increased, and the density decreased (1,35 → 1.15).

At this time, the charge amount of the toner on the toner carrier is +16 nc.
/ cm ² .

Comparative Example 2 A toner was obtained in the same manner as in Example 1, except that 100 parts of the magnetic material A was used instead of the magnetic material B.

Table 1 shows the particle size distribution of the classified powder, and Table 2 shows the results of the copy test in the same manner as in Example 1. As shown in Table 2, good results were obtained, but tailing and roughness were slightly more than in Example 1. Although there was no problem in practical use, the fixability was slightly inferior, and many scratches were observed on the photosensitive drum, and began to appear on the image at 5000 sheets.

Comparative Example 3 A toner was obtained in the same manner as in Example 1, except that the magnetic material B used in Example 1 was changed to 50 parts.

Table 1 shows the particle size distribution of the classified powder, and Table 2 shows the results of the copy test in the same manner as in Example 1.

Although there was no problem with image density and fog, image quality such as resolution and fine line reproducibility was inferior.

At 32.5 ° C. and 85% RH, the image density was low, especially at the beginning (1.15 to 1.23), and the solid black was as low as 1.07.

The initial charge amount of the toner on the toner carrier is + 4.3n.
c / cm ² .

Comparative Example 4 A toner was obtained in the same manner as in Example 1, except that the magnetic material A was replaced with 60 parts of the magnetic material A.

Table 1 shows the particle size distribution of the classified powder, and Table 2 shows the results of the copy test in the same manner as in Example 1.

Although there was no problem in image density, there were many fogs, solid black portions were rough, image quality such as resolution and fine line reproducibility were inferior, and toner consumption was large. In addition, sleeve coat unevenness was observed in the non-image area.

[Effects of the Invention] The present invention is a magnetic toner which has been subjected to the above-described magnetic material surface treatment and has a specific particle size distribution, and therefore exhibits the following excellent effects.

(1) Stable charging is maintained even in a low humidity environment.

(2) An image which is stable and is excellent in fine line reproducibility and resolution without being affected by temperature and humidity.

(3) It has excellent durability and maintains an initial high image quality even after long-term use.

(5) Provide high image density with small consumption.

(5) Dispersion of the magnetic material in the binder resin is improved, the durability is excellent, and an image without fogging is always stably provided.

(6) The performance of the binder resin is sufficiently exhibited without adversely affecting the fixing property and the offset resistance.

Claims (4)

(57) [Claims] 1. A magnetic toner having at least a magnetic substance adsorbing a compound represented by the following general formula (1) and a binder resin, wherein at least 12% by number of magnetic toner particles having a particle diameter of 5 μm or less are contained. 33% by number or less of magnetic toner particles having a particle diameter of 8 to 12.7 μm, 2% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more, and the volume average particle diameter of the magnetic toner is A magnetic toner having a thickness of 4 to 10 μm. 2. An image forming apparatus according to claim 1, wherein an electrostatic image holding member for holding the electrostatic image on the surface and a toner holding member for holding the magnetic toner on the surface are arranged at a predetermined gap in the developing section. This is a developing method in which the toner is conveyed to the developing unit while being regulated to a thickness smaller than the gap, and is developed while applying an alternating electric field to the toner in the developing unit. A magnetic toner having at least a magnetic substance adsorbing a compound represented by the formula and a binder resin, containing 12% by number or more of magnetic toner particles having a particle diameter of 5 μm or less;
Magnetic toner particles having a particle diameter of 12.7 μm are contained in 33% by number or less, magnetic toner particles having a particle diameter of 16 μm or more are contained in 2% by volume or less, and the volume average particle diameter of the magnetic toner is 4 to 10 μm. A developing method characterized by being a certain magnetic toner. 3. The toner carrier according to claim 2, wherein the toner carrier has a surface on which irregularities formed by a plurality of spherical trace depressions are formed by blasting with smooth or regular particles.
The developing method described in the above. 4. The surface of the toner carrier, wherein the spherical trace depressions have a diameter R = 20 to 250 μm, a pitch P of irregularities = 20 to 100 μm, and a surface roughness d = 0.1 to 5 μm. The developing method described in the above.