JPH02287362A - Magnetic toner and developing method using the toner - Google Patents

Abstract

PURPOSE:To obtain images particularly stable under a low humidity without being affected by environment of a temp., humidity, etc., by specifying the content and volume average particle grain size of the magnetic toner particles of the magnetic toner contg. a magnetic material adsorbed with a specific compd. on the surface. CONSTITUTION:The magnetic toner having the magnetic material adsorbed with the binder resin and sorbitan fatty acid ester, the ethylene oxide addition product of the sorbitan fatty acid ester or the mixture composed thereof is formed. The magnetic toner particles having <=5mum grain size are incorporated at >=12 number % therein; the magnetic toner particles having 8 to 12.7mum grain size are incorporated at <=33 number % therein and the magnetic toner particle having >=16mum grain size are incorporated at <=2vol.% therein. The volume average particle grain size of the magnetic toner is specified to 4 to 10mum. The electrostatic charge stable even in the low-humidity environment is maintained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner for developing electrostatic latent images in electrophotography, electrostatic recording, etc., and a developing method using the toner.

[Prior Art] Conventionally, two-component toners using a carrier and one-component toners containing a magnetic component are known as dry toners used in electrophotography and the like.

- component magnetic toner has the advantage that the developing device can be simplified,
It has been widely used because it is easy to maintain.

Generally, the following method is used to produce magnetic toner.

The magnetic material, binder resin, charge control agent, etc. are mixed uniformly using a mixer such as a ball mill or Henschel mixer, and then melted and kneaded using a kneader such as a roll mill, extruder, or kneader to thoroughly incorporate each component. disperse. Thereafter, it is finely pulverized using a jet mill or the like, and then classified using an air classifier or the like to obtain a magnetic toner.

In addition, in order to improve the dispersion of the magnetic material in the binder resin,
Methods have been proposed in which the surface of a magnetic material is treated with various substances for the purpose of increasing the compatibility of the magnetic material with an organic material.

For example, JP-A-53-137148 discloses fatty acids and their derivatives, JP-A-53-81125 discloses polymeric materials, and JP-A-54-127329 discloses silane coupling agents. JP-A-55-28019 discloses a titanium coupling agent. These materials are excellent in improving compatibility.

However, in magnetic toner, the magnetic material is exposed to some extent on the surface of the toner and discharges the excessive 1F charge, thereby playing a role in adjusting the amount of charge to a proper level. Therefore, when using a magnetic material treated as described above, the hydrophilicity of the surface of the magnetic material is lost and the polarization becomes large, inhibiting the release of charge, causing the toner to become overcharged and scattering onto the image. Roughness may occur. In addition, the reflection force on the developing sleeve becomes strong, which may cause a decrease in density or cause unevenness in the sleeve coat. This phenomenon becomes more noticeable under low humidity conditions or in high-speed machines, and it is inevitable that image defects will occur.

On the other hand, various magnetic materials are manufactured in order to obtain the desired magnetic properties, electrical properties, and powder properties, but some of them do not release enough charge, and compared to the above example, There are many magnetic materials that cause image defects, albeit to a lesser extent.

In addition, as a method for improving the dispersion of magnetic materials, JP-A-58
-125749, JP 59-1213544, JP 59-125747, JP 59-
125748, JP 59-125749, JP 59-125750, JP 61-59
No. 349 discloses a surfactant. These materials are excellent in improving compatibility, have stable charging properties even under low humidity, and give good images. However,
Although it is moisture resistant in the sense that it does not undergo irreversible changes under high humidity conditions, it tends to release more charge 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, their uses have expanded to a wide variety of uses, and demands on their image quality have become stricter. When copying images such as general documents and books, it is required to reproduce extremely finely and faithfully, without being crushed or cut off, even down to the minute characters. Particularly, when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, fine line reproducibility is generally poor, and the sharpness of the line image is still not sufficient. In recent years, in image forming devices such as electrophotographic printers that use digital image signals, latent images are formed by dots with a constant potential, and solid areas, halftone areas, and light areas have a high dot density. It is expressed by changing. However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, it is said that the gradation of the toner image that corresponds to the ratio of the dot density between the black and white areas of the digital latent image cannot be obtained. There is a problem. Furthermore, if you want to reduce the dot size and improve the resolution to improve the image quality,
The reproducibility of latent images formed from minute dots becomes more difficult, and images tend to have poor resolution and gradation, and lack sharpness.

In addition, although the image quality is good initially, as copying or printing continues, the image quality may deteriorate. This phenomenon is thought to occur because, as copying or printing continues, only toner particles that are easily developed are consumed first, and toner particles that are less developable accumulate and remain in the developing machine.

Up to now, several developers have been proposed for the purpose of improving image quality. Japanese Patent Publication No. 51-3244
The publication proposes a non-magnetic toner intended to improve image quality by regulating particle size distribution. In the toner,
The toner mainly has a particle size of 8 to 12 μm, which is relatively coarse, and according to the studies of the present inventors, it is difficult to uniformly “glue” the latent image with this particle size, and toner with a particle size of 5 μm or less is 30% by number or less, and 20am or more is 5% by number or less, which means that the particle size distribution is broad, which also tends to reduce uniformity. In order to form clear images using such coarse toner particles and a toner with a broad particle size distribution, it is necessary to layer the toner particles thickly to fill the gaps between the toner particles and reduce the apparent appearance. There is also the problem that it is necessary to increase the image density, and the amount of toner consumption necessary to achieve a predetermined image density increases.

Furthermore, in JP-A-54-72054, a non-magnetic toner having a sharper distribution than the former is proposed, but the particle size of medium weight particles is coarse, 8.5 to 11.0 μm, and There is still room for improvement as a toner in terms of resolution.

In JP-A No. 58-129437, the average particle size is 6 to 6.
10 um, and a non-magnetic toner in which the maximum number of particles is 5 to 8 μm has been proposed, but the number of particles of 5 μm or less is 15%.
There is a tendency for images with less sharpness to be formed.

According to studies conducted by the present inventors, it has been found that toner particles of 5 μm or less have the main function of clearly reproducing the outline of a latent image and densely applying the toner to the entire latent image.

In particular, in the electrostatic latent image on the photoreceptor, the electric field strength is higher at the edge part than the inside due to the concentration of electric lines of force.
The quality of the toner particles that collect in this area determines the sharpness of the image quality. According to studies conducted by 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 increases, so the amount of charge per toner particle light increases. Therefore,
As the particle size of the magnetic toner is reduced, the amount of charge due to frictional electrification increases, and the magnetic toner gradually becomes overcharged.

Therefore, simply reducing the particle size of conventionally used magnetic toner tends to result in excessive charging, and when used in low humidity conditions, the amount of charging increases further, resulting in increased fogging, roughness, and scattering. , may cause a decrease in image density. Further, even if the toner coat is thin and uniform, and the magnetic toner has a small particle size, which is advantageous against sleeve coat unevenness, sleeve coat unevenness may occur under severe usage conditions. Further, in order to reduce the particle size, further improvement in the dispersibility of the magnetic material is required.

In view of the above, there is a need for a toner that provides good images under any environment. In other words, there is a need for a magnetic toner in which a magnetic material having desired characteristics is well dispersed in a binder resin, the amount of charge can be effectively adjusted, the reproducibility of a latent image is excellent, and an image with high resolution is produced.

[Problems to be Solved by the Invention] An object of the present invention is to provide a toner that is not affected by the environment such as temperature and humidity and provides a stable image particularly under low humidity.

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

Still another object is to provide a toner that has good dispersion of magnetic material in resin, has excellent durability, and consistently provides fog-free images even after long-term continuous use. .

Still another object is to provide a magnetic toner that does not impede the fixing properties and anti-offset properties of the binder resin.

[Means and effects for solving the problem] As a result of intensive research for the above-mentioned purpose, the inventors of the present invention have devised a method to create a magnetic toner having a specific particle size distribution using a magnetic material with a specific compound adsorbed on its surface. It has been found that the toner can be stabilized in its chargeability, the magnetic material can be dispersed well in the resin, and it has excellent environmental stability and durability. The magnetic toner of the present invention is based on the above findings, and more specifically, it contains a binder resin and a sorbitan fatty acid ester.

It is characterized in that its main component is a magnetic material adsorbed with an ethylene oxide adduct of sorbitan fatty acid ester or a mixture thereof.

Furthermore, the present invention provides a magnetic toner having a small amount of both a binder resin and a magnetic material, which contains 12% or more by number of magnetic toner particles having a particle size of 5 μm or less, and 8 to 12.7 μm.
Magnetic toner particles having a particle size of 1 μm are contained in an amount of 33% or less by number, magnetic toner particles having a particle size of 6 μm or more are contained in an amount of 2.0% by volume or less, and the volume average particle size of the magnetic toner is 4 to 4% by volume. f) μm.

The present invention will be explained in more detail below. In the following description, "%" and "part" expressed as quantitative ratios are based on weight unless otherwise specified.

In the magnetic toner of the present invention, a magnetic material on which a compound represented by the formula (1) is adsorbed is used.

These compounds consist of an alkyl group serving as a hydrophobic group, a hydroxyl group serving as a parent group, and an ether bond, and are represented by the following formula.

1 0 - A' represents the real number of . jSpecifically, the following compounds may be mentioned.

Sorbitan monolaurate (1 Sorbitan monostearate (2 Sorbitan monooleate (3) Sorbitan tristearate (4 Sorbitan sesquioleate (5 Sorbitan trioleate (6 Sorbitan monolaurate ethylene oxide 6 moles) Adduct (7) Sorbitan monostearate ethylene oxide 4 mole adduct (8) Sorbitan monobalmitate ester ethylene oxide 8 mole adduct
(9) Sorbitan monooleate ethylene oxide 10 mole adduct (
lO) Sorbitan sesquistearate ethylene oxide 14 mole adduct (11) Sorbitan tristearate ethylene oxide 4120
Molar adducts (12) Generally, many compounds are known to exhibit hydrophilicity and hydrophobicity, but when adsorbed to a magnetic material, many of them fail to release an effective charge and become overcharged or absorb moisture. This causes extremely excessive discharge of charge, resulting in significant charging deficiency.

In the compound of the present invention, the parent group hydroxyl group and ether bond facilitate adsorption onto a magnetic material. It is also believed that these functional groups suppress the polarization of the surface of the magnetic material and supplement effective charge release.

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 etc. is improved,
It is believed that this improves the dispersibility of the magnetic material in the toner and also suppresses significant moisture absorption.

Magnetic toner containing a magnetic substance that has adsorbed these compounds does not absorb a lot of moisture, but under high humidity conditions, charge release increases and the magnetic toner may not be able to maintain good developability. Charging failure may occur, resulting in a decrease in image density. However, by making the magnetic toner containing the magnetic material, which is a feature of the present invention, have the particle size distribution described below, the above drawbacks can be overcome and the objects of the present invention can be achieved. That is, by defining the magnetic toner in the particle size distribution of the present invention, the amount of charge is increased, and the friction with the triboelectric charge imparting member is increased, the charging ability of the magnetic toner is improved, and the effect of the magnetic material used in the present invention is enhanced. It is something that makes it noticeable. Further, since reducing the particle size of the magnetic toner tends to result in excessive charging, the magnetic material of the present invention plays a role in controlling the amount of charge of the magnetic toner. In other words, the magnetic material of the present invention is suitable for use in magnetic toner with small particle size.

On the other hand, regarding the particle size, the magnetic toner of the present invention has a particle size of 5 μm.
One of the characteristics is that magnetic toner particles having a particle size of m or less account for 12% or more by number. Conventionally, in magnetic toner, it is difficult to control the amount of charge of magnetic toner particles of 5 μm or less, and the charge tends to be excessively charged. For this reason, toner particles of 5 μm or less have a strong reflection force on the developing sleeve, etc., and stick to the sleeve surface, inhibiting the frictional charging of other particles, generating toner particles with insufficient charging, and causing roughness and density reduction. It was thought that it was necessary to proactively reduce the risk of cancer.

However, according to studies conducted by the present inventors, it has been found that magnetic toner particles of 5 μm or less are an essential component for forming high-quality images.

For example, by 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;
Developing a latent image by changing the surface potential on the photoreceptor, from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, to a small development potential contrast in which only a few toner particles are developed,
When the developed toner particles on the photoreceptor were collected and the I/toner particle size distribution was measured, it was found that there were many magnetic toner particles of 8 μm or less, particularly 5 μm or less. In other words, when magnetic toner particles with a particle size of 5 μm or less, which is suitable for development, are smoothly supplied to develop the latent image on the photoreceptor, the latent image is faithful to the latent image, does not protrude from the latent image, and is truly reproducible. This is an excellent image changer.

The magnetic toner containing the magnetic material of the present invention has a diameter of 8 μm or less,
In particular, the charging of magnetic toner particles of 5 μm or less is appropriately controlled, and the above-mentioned effects are effectively exhibited.

Further, in the magnetic toner of the present invention, 8 to 12.7μ
One of the characteristics is that the number of particles in the range m is 33% or less by number. As mentioned above, this is related to the necessity of the presence of magnetic toner particles with a particle size of 5 μm or less. However, in the latent image itself, the electric field strength at the edges around it is higher than at the center, so that toner particles tend to stick more tightly inside the latent image than at the edges, and the image density may appear thinner. In particular, 5μm
The following magnetic toner particles have a strong tendency to do so.

However, the present inventors have found that this problem can be solved and further clarity can be achieved by containing toner particles in the range of 8 to 12.7 μm in an amount of 33% by number or less. That is, toner particles with a particle size in the range of 8 to 12.7 μm are different from magnetic toner particles with a particle size of 5 μm or less.
This is thought to be because the amount of charge is appropriately controlled, but the toner is supplied to the inner side of the latent image where the electric field strength is lower than the edge area, which compensates for the lack of adhesion of the inner toner particles to the edge area, resulting in uniform development. An image is formed, and as a result, a sharp image with high density and excellent resolution and gradation is provided.

For particles with a particle size of 5 μm or less, if the number % is 12 to 60, the difference between the number % (N) and volume % (V) is N/V = -0,04N + k (however, , 4.5≦≦8.5; 12≦N≦60) It is also preferable that the magnetic toner of the present invention satisfies the following relationships.The magnetic toner of the present invention having a particle size distribution that satisfies this range is more excellent. It is possible to achieve high developability.

While studying the state of particle size distribution of 5 μm or less, the present inventors found that there is a state of existence of fine powder most suitable for achieving the purpose, as shown by the above formula. That is, 1
For a certain value of N (2≦N≦60), a large N/V indicates that particles with a width of 5 μm or less are widely included, and a small N/V indicates that particles with a width of around 5 μm are included. It is understood that this indicates that the existence rate of particles with a diameter of 100% is high, and that there are few particles with a smaller diameter. 82 and further satisfies the above relational expression, good fine line reproducibility and high resolution can be achieved.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 16 μm or more is 2.0% by volume or less, and is as small as possible.

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

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

It is preferable that the magnetic toner particles having a particle size of 5 μm or less account for 12% by number or more of the total number of particles, preferably 12 to 60% by number. When the number of magnetic toner particles with a particle size of 5 μm or less is less than 12%, there are few magnetic toner particles effective for high image quality, and especially as the toner is used for continuous copying or printing, the effective magnetic toner particles become less effective. As the components decrease, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually deteriorates. Moreover, if it exceeds 60% by number, magnetic toner particles tend to aggregate with each other, resulting in toner agglomerates larger than the original particle size, resulting in rough image quality and reduced resolution.
Or, the density difference between the edge part and the inside of the latent image becomes large,
In some cases, the image may appear hollow.

Further, it is preferable that the number of particles in the range of 8 to 12.7 μm is 33% by number or less, and preferably 1 to 33% by number.

When the amount is more than 33% by number, the image quality deteriorates and more development than necessary occurs, that is, too much toner is applied, leading to an increase in toner consumption.

On the other hand, if it is less than 1% by number, it may become difficult to obtain high image density. In addition, between the number% (N%) and 1% by volume (V%) of magnetic toner particles having a particle size of 5 μm or less,
There is a relationship such that N/V=-0.04N+, which indicates a positive number in the range of 4.5≦ and ≦6.5. Preferably 4.5≦≦
It is 6.0. As shown above, 12≦N≦60.

When k<4.5, the number of magnetic toner particles having a particle size smaller than 5.0 μm is small, and the image density, resolution, and sharpness tend to be poor. Conventionally, the presence of fine magnetic toner particles, which were often thought to be unnecessary, is important in development.
It achieves the closest packing of toner and contributes to the formation of uniform images without roughness. In particular, by uniformly filling in thin lines and image contours, visual sharpness is further enhanced. That is, when k<4.5, these properties tend to be inferior due to the lack of this particle size distribution component.

From another point of view, in terms of production, conditions such as classification will become stricter in order to satisfy the condition of k<4.5, which will be disadvantageous in terms of yield and toner cost. Also, k >
8.5, due to the presence of more fine powder than necessary, the particle size distribution becomes unbalanced due to repeated copying.
The degree of aggregation of the toner may increase or frictional charging may not be performed effectively, resulting in poor cleaning or fogging.

Further, the amount of magnetic toner particles having a particle size of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume or less, and still more preferably 0.5% by volume or less. If it is more than 2.0% by volume, not only will it be a hindrance to reproducing fine lines, but also coarse toner particles of 16 μm or more will protrudely exist on the thin layer surface of toner particles developed on the photoreceptor during transfer. Assuming that the delicate adhesion between the photoreceptor and the transfer paper via the toner layer is irregular,
This causes fluctuations in transfer conditions and is a cause of defective transfer images.

Further, the magnetic toner of the present invention cannot sufficiently retain the charge of magnetic toner particles having a diameter of 16 μm or more, resulting in charging failure and fogging in the background area and reversed area.

The volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 μm.
~9μ, and this value cannot be considered separately from each component mentioned above. When the volume average particle diameter is 4 μm or less, the amount of toner on the transfer paper is small in applications with a high image area ratio such as graphic images (
, the problem of low image density is likely to occur. this is,
This is thought to be due to the same reason as the reason why the density inside the edge portion of the latent image decreases as described above. If the volume average particle diameter is 10 μm or more, the resolution is not good, and even if copying is good at the beginning, image quality tends to deteriorate with continued use. Furthermore, image density tends to decrease under high humidity conditions.

The magnetic toner of the present invention, which has a specific particle size distribution, can faithfully reproduce down to the fine lines of the latent image formed on the photoreceptor, and can reproduce halftone dots and digital dot latent images. It provides images with excellent gradation and resolution. Furthermore, it maintains high image quality even when copying or printing is continued, and even in the case of high-density images, it is possible to perform good development with less toner consumption than conventional magnetic toner, making it economical. It also has the advantage of making the main body of a copying machine or printer more compact.

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

Further, since the magnetic toner of the present invention has good dispersion of the magnetic material, it has excellent durability and is also characterized by providing images with very little fog, which is preferable for reducing the toner particle size.

The amount of nosorbitan fatty acid ester of the present invention or its ethylene oxide adduct to be used depends on the binder resin, magnetic material, presence or absence of additives used as necessary, adsorption method to the magnetic material,
It is determined by the toner manufacturing method and is not uniquely limited. The preferred usage amount is magnetic material I
0.01 to 5 parts (more preferably 0.1 to 5 parts) per n part
Part 3). If the amount used is less than 0.01 part, the effect of charge release will not be effective, and if it exceeds 5 parts, the charge will be released excessively, resulting in poor charging under high humidity and a decrease in image density. There is a fear.

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

In order to achieve the same object as the present invention, although the effect is smaller than that of the present invention, it is possible to consider means of increasing the magnetic substance content. In this case, the ratio of magnetic material increases, which has a negative effect on fixing properties and causes low-temperature offset. Another disadvantage is that the organic photoreceptor is easily damaged. Furthermore, the strong magnetic binding force from the toner carrier reduces developability, resulting in image defects such as reduced image density and roughness.
It has the disadvantage of causing deterioration in image quality.

On the other hand, in the magnetic toner of the present invention, charge is effectively discharged, the amount of charge is stable, and fog is extremely low, so that the content of magnetic material can be reduced. Therefore,
The influence of magnetic binding force is reduced, resulting in improved image quality such as higher density, no tailing, better resolution, and no roughness.

Furthermore, in addition to good dispersibility, it is advantageous in fixing properties and low-temperature offset resistance, and can fully demonstrate the performance of the binder resin. Furthermore, since it does not excessively damage the organic photosensitive layer, etc., it is preferably used in models using organic photoreceptors, etc.

The magnetic toner of the present invention exhibits its effects more effectively as the toner particle size is made smaller for the following reasons. For example, in the case of magnetic toner, reducing the particle size has drawbacks such as increased fog and image defects due to excessive charging. In order to solve these drawbacks, measures have been taken to increase the magnetic material content, but this results in the above-mentioned disadvantages.

Furthermore, the smaller the toner particle size, the greater the defects, so the magnetic substance content must be increased, and the disadvantages also become greater. However, in the magnetic toner of the present invention, it is possible to reduce the magnetic substance content, so that the adverse effects can be suppressed. The magnetic toner of the present invention can fully exhibit its effects when the average volume particle size is 10 μm or less, particularly 9 μm or less, and the smaller the particle size, the more effective the effect can be expected.

According to the findings of the present inventors, when the particle size is made smaller or the magnetic material content is reduced, the magnetic brushes on the toner carrier become shorter and denser (even if the toner coat layer becomes thinner, the developing ability decreases). The magnetic toner of the present invention achieves both of these at the same time, resulting in even better image quality. be.

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

In other words, the measuring device is Coulter counter TA.
- An interface (manufactured by Nikkaki) that outputs number distribution 1 volume distribution using type II (manufactured by Coulter) and CX-
1 A personal computer (manufactured by Canon) is connected, and a 1% NaCR aqueous solution is prepared using primary sodium chloride as the electrolyte. As a measurement method, the electrolytic aqueous solution 100-1
50mI! A surfactant, preferably an alkylbenzenesulfonate salt, is added as a dispersant in an amount of 0.1 to 5 mI! In addition,
Furthermore, 2 to 20 mg of the measurement sample is added. The electrolyte in which the sample was suspended was dispersed using an ultrasonic disperser for about 1 to 3 minutes.
The particle size distribution of particles of 2 to 40 .mu. on the basis of number of particles was measured using the Coulter Counter T-II, using a 100 .mu. aperture as the aperture, and the values according to the present invention were determined therefrom.

As the binder resin used in the toner of the present invention, the following binder resins for toners can be used when a heated pressure roller fixing device having an oil coating device is used.

For example, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene: styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer , styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrenic copolymers such as indene copolymers: polyvinyl chloride, phenolic resin, naturally 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, coumaron indene resin, petroleum resin, etc. can be used.

In the heating and pressure roller fixing method that uses almost no oil, 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. That's a problem. Toners that are fixed with less thermal energy usually tend to block or cake during storage or in a developing device, so these problems must also be taken into consideration. The physical properties of the binder resin in the toner are most responsible for these phenomena, but according to the research of the present inventors, reducing the content of magnetic material in the toner causes the toner image to become weaker on the toner image supporting member during fixing. Although the adhesion of the toner to the toner improves, the inherent properties of the binder resin tend to appear, making offset more likely to occur, and blocking or caking may also occur. Therefore, when using the heated pressure roller fixing method in which little oil is applied in the present invention, the selection of the binder resin is more important. Preferred binding materials include crosslinked styrenic copolymers or crosslinked polyesters.

Examples of comonomers for styrene monomers in the % copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, Monocarboxylic acids having a double bond such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide, etc. or substituted products thereof; e.g., maleic acid, butyl maleate , methyl maleate, dimethyl maleate, etc., and their substituted dicarboxylic acids; 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 ethers such as vinyl isobutyl ether may be used alone or in combination of two or more.

As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate and ethylene glycol diacrylate. methacrylate, 1,3-butanediol dimethacrylate, etc.
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.

In addition, when using a pressure fixing method, it is possible to use a binder resin for pressure fixing toner, such as polyethylene,
Examples include polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, and paraffin.

The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, maghematite, and ferrite, and iron oxides including other metal oxides; Fe, Go, and Ni.
Metals such as, or these metals and AI, Go
, Cu, Pb, Mg, Nl, Sn, Zn,
Sb, Be.

Bf, Cd, Ca, un, Se, Ti, W
, alloys with metals such as V, and mixtures thereof.

These ferromagnetic materials have an average particle size of about 0.1 to 2μI, and a magnetic property with a coercive force of 2o to 1500 when 6e is applied to 10
e It is desirable to have a saturation magnetization of 50 to 200 emu/g and a residual magnetization of 2 to 2 emu/H.

Further, in the magnetic toner of the present invention, it is preferable that a charge control agent be added internally or externally to the toner. -1 Since the magnetic toner of the present invention stabilizes charging, the charge control agent can be selected from a wide range.

Known positive charge control agents can be used in the present invention, such as nigrosine and its modified products with fatty acid metal salts, quaternary ammonium salts, diorganotin oxides, diorganotin borates, etc. alone or in combination. Can be used in combination. Among these, nigrosine type and quaternary ammonium salts are particularly preferably used.

Furthermore, a monopolymer expressed by the formula 1,000 or a copolymer with a polymerizable monomer such as styrene, acrylic ester, or methacrylic ester as described above can be used as a positive charge control agent. In this case, it also functions as (a part or all of) a binder resin.

On the other hand, known negative charge control agents can be used in the present invention, such as 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 characteristic 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 that has a magnetic field generating means inside for triboelectrification, the number of times the toner particle surface contacts the sleeve increases compared to conventional magnetic toner, and the toner particles Particle wear and sleeve surface contamination are more likely to occur. When the magnetic toner according to the present invention is combined with fine silica powder, wear is significantly reduced due to the presence of the fine silica powder between the toner particles and the sleeve surface. As a result, the lifespan of the magnetic toner and sleeve can be extended, and stable charging properties can also be maintained, making it possible to create a developer with magnetic toner that is even better for long-term use. . Furthermore, the magnetic toner particles having a particle size of 5 μm or less, which play a major role in the present invention, are more effective due to the presence of fine silica 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 produced by a dry method.

The dry method mentioned here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.

SIC! '4+ 2 H2+ 02-5iOz + 4
HClAlso, by using other metal halide compounds such as aluminum chloride or titanium chloride together with silicon halide compounds in this manufacturing process, it is also possible to obtain composite fine powders of silica and other metal oxides. include.

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

For example, the decomposition reaction of sodium silicate with an acid is shown below.

Na, 0-X5iO, +HC4l +H, 0-*SiO
, -nH20+NaCROther methods include decomposition of sodium silicate with ammonia salts or alkali salts, generation of alkaline earth metal silicate from sodium silicate and then decomposition with acid to form silicic acid, method of decomposing sodium silicate solution into ion There are methods such as using exchange resin to produce silicic acid, and using natural silicic acid or silicate.

The silica fine powder mentioned here includes anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate. can.

Among the silica fine powders mentioned above, the specific surface area due to nitrogen adsorption measured by the BET method is 3 om'/g or more (especially 50 to 40 om'/g).
0II12/g) gives good results. Silica fine powder 0.0 per 100 parts by weight of magnetic toner
It is preferable to use 1 to 5 parts by weight, preferably 0.1 to 5 parts by weight.

Further, when the magnetic toner of the present invention is positively chargeable,
As fine silica powder added to prevent toner wear and staining of the sleeve surface, rather than being negatively charged,
It is preferable to use positively charged silica fine powder because charging stability is not impaired.

As a method for obtaining positively chargeable silica fine powder, the above-mentioned untreated fine silica powder is added with at least one nitrogen atom in the side chain.
There is a method of treatment with a silicone oil having more than one organo group, a method of treatment with a nitrogen-containing silane coupling agent, or a method of treatment with both.

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

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

(Space below) (In the formula, R8 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group; i R2 represents an alkylene group or a phenylene group; R5 and R4 represent hydrogen, an alkyl group, or an aryl group; R6 (represents a nitrogen-containing heterocyclic group) The above alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, or may be substituted with halogen or the like within the range that does not impair chargeability. It may have a group.

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

R, -Sl-Yn (R represents an alkoxy group or halogen, Y represents an amino group or an organo group having at least one nitrogen atom, m and n are integers of 1 to 3, and m+n = 4
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. Examples of the nitrogen-containing heterocyclic group include unsaturated heterocyclic groups and saturated heterocyclic groups, and known ones can be used. 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 five-membered ring or a six-membered ring in consideration of stability.

Examples of such treatment agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, mono- Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane.

Dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine.

There are trimethoxysilyl-γ-propylbenzylamine, etc. Furthermore, as the nitrogen-containing heterocycle, those having the above-mentioned structure can be used. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl- γ-propylmorpholine, trimethoxysilyl-γ-
Examples include propylimidazole.

The application amount of these treated positively charged silica fine powders is
0.01 to 100 parts by weight of positively charged magnetic toner
The effect is exhibited when the amount is 8 parts by weight, particularly preferably 0.1
~5! ! It exhibits positive chargeability with excellent stability when added in a certain amount. Regarding the form of addition, the preferred form is 0.1 to 0.1 to 100 parts by weight of positively charged magnetic toner.
It is preferable that 3 parts by weight of the treated silica fine powder be attached to the surface of the toner particles. Note that the untreated fine silica powder described above can also be used in the same amount.

Furthermore, the silica fine powder used in the present invention may be treated with a silane coupling agent, a treatment agent such as silicone oil or an organosilicon compound for the purpose of hydrophobization, or a combination of various treatment agents, if necessary. It may be treated with the above-mentioned treatment agent that reacts with or physically adsorbs the silica fine powder. Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, tritylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, and benzyldimethylchlorosilane. , bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyl Dimethoxysilane, diphenyljethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, l,3-diphenyltetramethyldisiloxane, and having 2 to 12 siloxitin units per molecule, with terminal SL for each unit located
There are dimethylpolysiloxanes containing hydroxyl groups bonded to .

Further, silicone oil is generally represented by the following formula.

Preferred silicone oils have a viscosity of approximately 5 to 5000 centistokes at 25°C, such as methyl silicone oil.

Preferred are dimethyl silicone oil, phenylmethyl silicone oil, chlorphenylmethyl silicone oil, alkyl-modified silicone oil, fatty acid-modified silicone oil, polyoxyalkylene-modified silicone oil, and the like. These are 11m or 2f! Used in mixtures of one or more.

Further, in the present invention, it is preferable to add fine powders of fluorine-containing polymers, such as polytetrafluoroethylene, polyvinylidene fluoride, etc., and fine powders of tetrafluoroethylene-vinylidene fluoride copolymers. Particularly, polyvinylidene fluoride fine powder is preferable from the viewpoint of fluidity and abrasiveness, and the amount added to the toner is 0.
．． 01-2, Owt%, particularly 0.02-L, Owt% is preferred.

In particular, in magnetic toners that combine fine silica powder with the above-mentioned fine powders, for reasons that are not clear, the state of the silica adhered to the toner is stabilized, and for example, the adhered silica is released from the toner, causing the toner to become The effect on wear and sleeve staining does not decrease, and
It is possible to further increase charging stability.

The magnetic toner of the present invention may be mixed with additives as required. Examples of other additives include lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, and aluminum oxide. There are fluidity imparting agents and anti-caking agents.

In addition, in order to improve mold releasability during hot roll fixing, waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax, paraffin wax, etc.
It is also one of the preferred embodiments of the present invention to add about 5 wt% of the toner to the magnetic toner.

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

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

However, with this method, the effect may be reduced or excessive moisture absorption may occur due to penetration into the binder resin or excessive exposure of the parent wood group.

There is also a possibility that the adsorption will not be carried out effectively on the surface of the magnetic material.

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

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

(3) A wet method in which the compound used in the present invention and the magnetic substance are dispersed and adsorbed in water or an organic solvent, followed by filtration and drying.

A dry method is a simple method, but a wet method is better in order to achieve more uniform adsorption on the surface of a magnetic material, and a method using water as a solvent is the best method due to safety and ease of production. This is the preferred method.

In manufacturing the toner according to the present invention, the toner constituent materials as described above are thoroughly mixed using a ball mill or other mixer, then thoroughly kneaded using a hot kneader such as a hot roll kneader-extruder, and after cooling and solidifying, It is preferable to obtain the toner by mvi crushing and classification; another method is to obtain the toner by dispersing the constituent materials in a binder resin solution and then spray drying; Polymerization toner production method in which a monomer is mixed with a predetermined material to form an emulsified suspension and then polymerized to obtain a toner; or in so-called microcapsule toners consisting of a core material and a shell material, the core material or shell material ,
Or a method of containing a predetermined material in both of these.
The following methods can be applied.

Furthermore, the magnetic toner according to the present invention can be produced by sufficiently mixing desired additives with a mixer such as a Henschel mixer, if necessary.

The magnetic toner of the present invention can be produced by electrophotography, electrophotography, etc. by conventionally known means.
All of them can be used for one-component development for visualizing electrostatic images in electrostatic recording, electrostatic printing, etc.

The magnetic toner of the present invention is preferably applied to an image forming method in which a latent image is developed while flying the toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoreceptor. A triboelectric charge is imparted by contact with the sleeve surface and coated in a thin layer on the sleeve surface. The thickness of the thin layer of magnetic toner is formed to be thinner than the gap between the photoreceptor and the sleeve in the development area. When developing a latent image on the photoreceptor, it is preferable to apply an alternating electric field between the photoreceptor and the sleeve and cause the magnetic toner having triboelectric charges to fly from the sleeve to the photoreceptor.

Examples of the alternating electric field include a pulsed electric field, an alternating current bias, or a combination of alternating current and direct current bias.

On the other hand, as a method for uniformly coating the magnetic toner on the toner carrier (sleeve), by using a method in which the surface is made into a rough surface with a specific unevenness by sandblasting with irregularly shaped particles, It is possible to provide an excellent developing device that can maintain a good toner coating state over a long period of time, with uniformity and no unevenness on the surface of the toner carrier. The target surface has numerous fine incisions or protrusions arranged in random directions.

However, in a developing device using a toner carrier having such a specific surface condition, depending on the applied magnetic toner,
Components in the toner tend to adhere to the surface, causing so-called contamination of the surface of the toner carrier. As a result, the density of the initial image decreases, and if the contamination progresses due to durability, the image deteriorates over the period of the toner carrier. A mortar drop occurs.

This is because components in the toner adhere to the slopes of the convex portions and concave portions of the surface of the toner carrier, resulting in poor charging of the magnetic toner particles and a decrease in the amount of charge in the toner layer.

In general, the components in magnetic toner consist of materials such as a magnetic binder resin, a charge control agent, and a release agent.The materials are designed to prevent contamination of the surface of the toner carrier. The current situation is that the selection of options is restricted.

Furthermore, if the surface of the toner carrier is smooth or has a specific unevenness formed by a plurality of spherical trace depressions, no matter what kind of material the magnetic toner is applied to, the toner will not be applied to the surface. Components become difficult to adhere to, and contamination can be prevented or reduced over a long period of time.

However, in terms of the ability to uniformly coat a toner carrier with magnetic toner, a toner carrier having a surface with specific irregularities formed by spherical trace depressions is difficult to achieve because of the ability to uniformly coat a toner carrier with magnetic toner. Although it is inferior under certain environments to a toner carrier having an uneven surface with incisions or protrusions in random directions, it is superior to a toner carrier having a completely smooth surface.

On the other hand, by using an uninvented magnetic toner in a toner carrier having a surface with spherical trace depressions, it is possible to prevent the toner coating layer from becoming excessively thick, and toner carriers with a smooth surface without toner coating unevenness occur. Even the body can be uniformly coated with toner over a long period of time. As a result, it is possible to obtain clear, high-quality images with high image density, excellent fine line reproducibility and gradation, and no fog over a long period of time.

The present invention will be described in detail below, and the toner carrier will hereinafter be referred to as a sleeve.

When the sleeve of the present invention has a surface with an uneven surface formed by a plurality of spherical trace depressions, a blasting method using regular particles can be used to obtain the surface condition. As the regular particles, for example, various rigid spheres such as metals such as stainless steel, aluminum, steel, nickel, and brass, ceramics, plastics, and glass beads having a specific particle size can be used. By blasting the sleeve surface using regular particles having a specific particle size, it is possible to form a plurality of spherical trace depressions with approximately the same diameter R.

In the present invention, the diameter R of the plurality of spherical trace depressions on the sleeve surface is preferably 20 to 250 μm, and the diameter R is 20 μm.
If it is less than m, contamination by components in the magnetic toner increases, which is not preferable. Therefore, it is preferable that the regular particles used during the blasting treatment of the sleeve surface have a diameter of 20 to 250 μm. In addition, in the present invention, the pitch P of the unevenness on the sleeve surface and the surface roughness d are measured using a microsurface roughness meter (sold by Tiller-Hopson, Koita Research Institute, etc.).
The surface roughness d is based on JIS 10-point average roughness (RZ) rJIs B 0IiOIJ. Also, the pitch P is 0.1 for the convex part or the concave parts on both sides.
Items with a height of μ or more are counted as one mountain and have a standard length of 0.
．． It was determined as follows based on the number of peaks within 25 mm.

Number of mountains (μ) included in 250 (μ)/250 (μ)
) In the present invention, the pitch P of the unevenness on the sleeve surface is
The value of P is preferably 2 to 100μ, and if P is less than 2μ, contamination of the sleeve due to components in the magnetic toner increases, which is not preferred. In addition, the surface roughness d of the unevenness on the sleeve surface is 0.1
~5 μm is preferable, and if d is 5 μm or more, unevenness may occur in a method in which development is performed by applying an alternating voltage between the sleeve and the latent image holder to cause magnetic toner to fly from the sleeve side to the latent image surface. This is not preferable because the electric field tends to concentrate in some areas and cause image disturbance.

In the present invention, fine line reproducibility was measured by the following method. In other words, an image of an original manuscript with thin lines exactly 100μI wide, copied under appropriate copying conditions, was used as the sample for measurement, and a Luzex 450 particle analyzer was used as the measurement device.The line width was measured using an indicator from the enlarged monitor image. At this time, since the line width measurement position has irregularities in the width direction of the fine line image of the toner, the average line width of the irregularities is taken as the measurement point. From this, the value (%) of fine line reproducibility is calculated using the following formula.

In the present invention, resolution was measured by the following method. In other words, it is a pattern consisting of five thin lines with equal line width and spacing, and f2.8.3.2.3.6 between 1 mm.
．． 4. Find the original image that appears to have 1 or 8.0 lines. The original manuscript with these 10 types of line images was copied under appropriate copying conditions, and the images were observed with a magnifying glass.
) is taken as the value of resolution.

The larger this number, the higher the resolution.

[Examples] The present invention will be explained in more detail below with reference to Examples, but these are not intended to limit the present invention in any way. All parts in the following formulations are parts by weight. Examples of manufacturing the magnetic material used in the present invention are shown below.

Magnetic material A (magnetic iron oxide) was added to 1 OIL of a 1.2 g/R aqueous solution of Compound (7) so that the slurry concentration was 93.5 g/i), and after stirring for 1 hour, it was separated into furnaces. Then, magnetic material B was obtained by heating and drying at 120°C.

At this time, the amount of compound (7) adsorbed was 1.0 parts per 100 parts of the magnetic material.

1 or 2 g of compound (8) instead of compound (7)
Magnetic material C was obtained in the same manner as in Production Example 1, except that the aqueous solution of No. 12 was used.

The adsorption amount of compound (8) is 0.9 per 100 parts of magnetic material.
It was a department.

1.5 g of compound (2) instead of wild-growing compound (8)
A magnetic material was obtained in the same manner as in Production Example 1 except that an aqueous solution of R was used.

The adsorption amount of compound (2) is 1.2 per 100 parts of magnetic material.
It was a department.

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

The adsorption amount of compound (7) is 1.0 per 100 parts of magnetic material.
It was a department.

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

In addition, when applying 10 KOe of magnetic material A, the magnetic property is a coercive force of 13
30e, saturation magnetization 83.7 parts mu/g, residual magnetization 12
．． 5 parts mu/g. The average particle size is 0.15 μm.

The magnetic material E has a coercive force of 630 e and a saturation magnetization of 91, respectively.
．． 8 parts mu/g, and residual magnetization 6.4 parts mu/g.

The average particle size is 0.20μ.

Magnetic material B (compound (7) adsorption amount 1.0%) 80 parts Unbalanced molecular weight ethylene-propylene copolymer 4 parts Nigrosine dye 2 parts The above materials were premixed in a Henschel mixer, and then mixed in an extruder heated to 150°C. After kneading and cooling, the mixture was coarsely pulverized using a cutter mill, pulverized using a pulverizer using a jet stream, and further classified using an air classifier to obtain a classified powder having an average volume particle size of 8.3 μm. The particle size distribution is shown in Table 1. This classified powder 1
00 parts positively charged hydrophobic colloidal silica (BET 2
00m''/g) were thoroughly mixed in a Henschel mixer to obtain a magnetic toner. Table 2 shows the results of copying 5,000 sheets with roughening, a dimple diameter of 53 to 62 μm, an uneven pitch of 30 μm, and a surface roughness of 2 μm.

As is clear from Table 2, images with excellent resolution and fine line reproducibility were obtained. Also 15℃, 10%RH132.5℃
Similarly good results were obtained under 85% RH.

The 1F charge amount of the toner on the toner carrier during the test is +7~
+9 nc/cm”.

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

Example 2 80 parts of magnetic substance C was used instead of magnetic substance B used in Example 1, and hydrophobic colloidal silica (BET 300m"7g) was used.
A toner was obtained in the same manner as in Example 1, except that 0.5 part of the toner was used.

The particle size distribution of the classified powder is shown in Table 1.

Table 2 shows the results of a copying test similar to that in Example 1. As shown in Table 2, high quality images faithful to the original were obtained. Furthermore, the temperature was 15°C and 10% RH.

Similar good results were obtained at 32.5° C. and 85% RH.

The amount of charge of the toner on the toner carrier during the test ranged from +6 to
It was stable within the range of +10 nc/cm''.

Example 3 90 parts of magnetic material was used instead of magnetic material B used in Example 1, and positively charged hydrophobic silica (BET 20 on 2, 7 g
) is set to 0.7 parts, and the rest are examples! A toner was obtained in the same manner as above.

The particle size distribution of the classified powder is shown in Table 1.

Table 2 shows the results of the copying test conducted in the same manner as in Example 1. As is clear from Table 2, images with excellent resolution were obtained. Also, 15℃, 10%RH.

Similarly good results were obtained at 32.5° C. and 85% R).

The charge amount of the toner on the toner carrier during the test was +8~
+1ine/cm2.

Cross-linked polyester resin (M w = 300,000) too
Part Magnetic substance F 70 parts Unbalanced molecular weight ethylene-propylene copolymer 3 parts 3.5-di-
2 parts of t-butylsalicylic acid chromium complex A classified powder was obtained in the same manner as in Example 1 using the above materials, and 0.6 part of hydrophobic colloidal silica (BET 300 m2/g) was added externally.

The particle size distribution of the classified powder is shown in Table 1.

This toner is applied to a commercially available electrophotographic copying machine (product name NP-75).
Table 2 shows the results of a 5,000-sheet copying test using No. 50, manufactured by Canon (the roughness of the developing sleeve was an irregular sandblasting process). As is clear from Table 2, images with excellent image quality and toner consumption were obtained.

Also, 15℃, 10%R)l, 32.5℃, 85%R
Similar results were obtained under H. The charge amount of the toner on the toner carrier during the test was -7 to -10 nc/cm2.

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

Table 1 shows the particle size distribution of the classified powder, and Table 2 shows the results of a copying test conducted in the same manner as in Example 1. As is clear from Table 2, good results were obtained. However, 15℃
, 10%R)I, a good image was obtained initially, but as the number of copies increased, the image became slightly rough, fog increased, and the density decreased (1.35 → 1.15).
.

At this time, the amount of charge of the toner on the toner carrier is +16
It was nc/cm2.

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

The particle size distribution of the classified powder is shown in Table 1, and examples! Table 2 shows the results of a copy test conducted in the same manner as above. As shown in Table 2, good results were obtained, but compared to Example 1, trailing and roughness were slightly more common. Further, although there was no problem in practical use, the fixing performance was somewhat poor, and there were many scratches on the photosensitive drum, which began to appear on the images after 5,000 copies were printed.

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

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

There were no problems with image density or fog, but image quality such as resolution and fine line reproducibility was poor.

In addition, the image density is low at 32.5℃ and 85%RH, especially at the initial stage (1.03 to 1.11), and solid black is 0.
．． It was as low as 95.

The initial charge amount of the toner on the toner carrier is +4.
Onc/cm".

Comparative Example 4 A toner was obtained in the same manner as in Example 1, except that 60 parts of magnetic substance A was used instead of magnetic substance B.

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

There was no problem with image density, but there was a lot of fogging, solid black areas were rough, and image quality such as resolution and fine line reproducibility was poor.
Toner consumption was also high. In addition, sleeve coat unevenness was observed in the non-image area.

(The following is a blank space) [Effects of the Invention] The present invention is a magnetic toner that has been subjected to the above magnetic surface treatment and has a specific particle size distribution, and therefore exhibits the following excellent effects. .

)1) Maintains stable charge even in low humidity environments.

1) It is not affected by temperature or humidity, and provides stable images with fine line reproducibility and high resolution.

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

;4) Provides high image density with low consumption.

;5) The magnetic material is well dispersed in the binder resin, has excellent durability, and always provides stable images without fog.

:6) Fully exhibits the performance of the binder resin without adversely affecting fixing properties and anti-offset properties.

Claims (4)

[Claims] (1) A magnetic toner having at least a magnetic material adsorbing a binder resin and a sorbitan fatty acid ester, an ethylene oxide adduct of a sorbitan fatty acid ester, or a mixture thereof, wherein the magnetic toner particles have a particle size of 5 μm or less. % by number or more, 33% by number or less of magnetic toner particles having a particle size of 8 to 12.7 μm, and 2% by volume or less of magnetic toner particles having a particle size of 16 μm or more. Volume average particle size is 4~
A magnetic toner characterized by having a diameter of 10 μm. (2) An electrostatic image carrier that holds an electrostatic image on its surface and a toner carrier that carries the magnetic toner on its surface according to claim (1) are arranged with a certain gap in the developing section, and the magnetic toner is A developing method characterized in that the toner is regulated to a thickness thinner than the gap on a toner carrier and transported to a developing section, and the toner is developed in the developing section while applying an alternating electric field to the toner. (3) The developing method according to claim (2), wherein the toner carrier has a surface that is smooth or has an uneven surface formed by a plurality of spherical trace depressions by blasting with regular particles. (4) The surface of the toner carrier has a spherical trace depression with a diameter R=
20 to 250 μm, uneven pitch P = 2 to 100 μm,
4. The developing method according to claim 3, wherein the surface roughness d is 0.1 to 5 μm.