JPS6374070A - Magnetic toner - Google Patents

Abstract

PURPOSE:To enhance development performance by specifying the average particle diameter and the particle diameter distribution of an amorphous fine powder and a proportion of the particles with <=8mum diameters in a magnetic toner high in resistivity, and further, the powder compressibility of the mixture with additives. CONSTITUTION:The particle diameter distribution of the amorphous fine particles containing a magnetic powder in a binder resin is regulated to the range of 5-35mum, and their average particle diameter is controlled to 10-18mum, and further, the proportion of the particles with <=8mum is controlled to 5vol%, thus permitting the obtained toner to be enhanced in powder fluidity, development performance transferability, cleanability, and stability against time lapse, an to prevent the inside of the copying machine from staining, and the additives are added to the surface of the toner and the powder compressibility is controlled to 25-40%, thus permitting the fluidity of the magnetic toner to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner for use in electrophotography, electrostatic recording, electrostatic printing, etc., and particularly to a high-resistance magnetic toner.

Conventionally, electrostatic WI formed on a photoreceptor or an electrostatic recording medium
Develop the moat using a one-component developer. A so-called -component development method is known.

This -component development method is a method of developing using a magnetic toner containing magnetic powder in a binder resin without using a carrier, and in particular, a method of developing using a magnetic brush developing method is typical.

This magnetic brush development method uses the magnetism of toner to form a magnetic brush of toner on a magnetic roll or the like to convey the toner, and develops the electrostatic latent image on the photoconductive photoreceptor with the toner brush to form a toner magnetic brush. It is something that gives you an image.

71 as a one-component phenomenon method! Various methods have been proposed, and these can be broadly classified into (1) a method using a magnetic toner with relatively low resistance, and (2) a method using a magnetic toner with a relatively high resistance.

The former induces charges of opposite polarity in a low-resistance magnetic toner according to the charge of an electrostatic latent image, and develops by the competition between electrostatic force and magnetic force. Although this method allows for highly efficient development, toner scattering occurs during electrostatic transfer of a toner image, and the transfer efficiency is also poor. In order to improve this problem, a special transfer paper with high resistance must be used, which is a drawback.

The latter is a method in which high-resistance magnetic toner is developed by imparting a charge of opposite polarity to the latent image to the toner by frictional charging, dielectric polarization, charge injection using an electrode, or the like. When transferring toner images, this method does not require the use of special transfer paper and can perform high-efficiency and good transfer, but because the toner has high resistance, electrostatic aggregation of toner particles occurs. This is likely to occur (and the developed toner image has a strong edge effect (,
In addition, it is easy to cause scumming and unevenness in non-WJ moat areas (poor developability is always a drawback).

Regarding the charging and development mechanism of high-resistance magnetic toner, the surface structure of toner particles and the powder fluidity of toner particles have a large influence on the electrical properties of toner during development and control the development properties. It has been known.

Therefore, studies have been made to overcome the above-mentioned drawbacks of high-resistance magnetic toner by controlling the surface structure and powder fluidity of the toner.

For example, it has been proposed to spheroidize the toner itself, to attach a lubricant to the surface of the toner, and to limit the particle size distribution of the toner to a specific range. However, when performing spheroidization treatment or fixing lubricant,
Because hot air and solvents are used, toner particles tend to stick to each other, only the surface of the toner particles tends to change in quality, residual solvent remains, and the surface treatment time is long, and the toner particles stick together and become large particles. This method has a disadvantage in that it requires steps such as removing the toner particles and completely removing the residual solvent.

Therefore, the first object of the present invention is to manufacture a magnetic toner with good developability by controlling the particle size distribution, shape and surface structure of the toner particles, and further adjusting the electrical properties of the toner particles. It is to provide.

A second object of the present invention is to provide a magnetic toner with good powder fluidity.

A third object of the present invention is to provide a magnetic toner that exhibits good transferability to any photoreceptor.

A fourth object of the present invention is to provide a magnetic toner that is stable against the environment.

A fifth object of the present invention is to provide a magnetic toner that provides stable image quality regardless of whether the process speed is high or low.

A sixth object of the present invention is to provide a magnetic toner that does not change over time and provides stable image quality.

The object of WJ7 of the present invention is to provide a magnetic toner that can effectively remove residual toner on a photoreceptor.

An eighth object of the present invention is to provide a magnetic toner that is free from contamination by toner particles inside a copying machine.

All of the above objects of the present invention are such that the particle size of the magnetic toner powder is in the range of 5 to 35μ, the average particle size is 10 to 18μ, and the particle size is 8μ or less, which is an amorphous fine powder of 5 volumes or less. This can be achieved by using a magnetic toner made of an additive attached to the surface of this amorphous fine powder. More preferably, the powder resistivity of the amorphous fine powder is 1016 Ωα or more under an electric field of 10 KV/cm, and the compression resistivity is 5 KV/cm.
10140 or more under an electric field of
1015Ω or more under an electric field of 0KV/cm, and compression resistivity is 5Kv/r! This can be achieved by using a magnetic toner that is controlled to 10120 pixels or more under an electric field of n.

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

Since the magnetic toner used in the present invention has high resistance, powder fluidity may be reduced due to electrostatic aggregation of toner particles, etc.
Furthermore, the developed toner image has a strong edge effect, and the non-image CI!
There are problems such as background smudges and uneven development. In order to solve this problem, methods have been proposed such as a method of attaching fine particles as a charge control agent or a fluidizing agent to the toner surface and a method of making toner particles spherical.

However, the use of heat and solvent in the spheroidization process has disadvantages such as adhesion of toner particles and deterioration of toner particles, the need for processes for these processes, and the possibility of aging due to residual solvent. There are negative effects such as things that happen. Furthermore, when adhering an additive as a charge control agent, the surface of the toner particles is too smooth.

Additives tend to stick to the surface of the toner particles (this results in problems such as image quality stains due to free additives, stains inside the machine, and stability when using vinegar.As a solution to this problem, there is a method of fixing the additives to the surface of the toner particles. However, this method requires the use of hot air or the like, which may cause the above-mentioned disadvantages.

On the other hand, if the surface of the amorphous particles has large irregularities, additives tend to be unevenly distributed in the recesses, and additives added as charge control agents have no effect during charge exchange, resulting in poor control of electrical properties and poor charging of toner particles. .

At present, this leads to deterioration in image quality, transferability, and cleaning performance, making it impossible to obtain good image quality. Therefore, it is desirable that the toner particles be fine powders with smooth surfaces and irregular shapes. Especially when two or more materials are dispersed on the particle surface to form the surface,
When toner particles come into contact, frictional electrification occurs between different materials, and some toner particles have charges of opposite signs, causing the toner to become static.
! It becomes easy to aggregate. In order to prevent this, by uniformly adhering conductive or semiconductive fine particles to the surface of the toner particles, charging properties and powder fluidity can be improved. The microparticles used here have a particle size of 10 mm to 30 mm, can have any shape, and are semiconductive or conductive organic materials or inorganic materials that adhere uniformly and in a single layer to the toner particle surface. It is made of materials. Examples include carbon plastic, glue, metal powder,
Metal salts, graphite, graphite heptadide, aluminum oxide, titanium dioxide.

Examples include zinc oxide.

In order to achieve the object of the present invention, it is most convenient to apply K to the toner surface by adhering a conductive powder, especially carbon black, to the toner surface, which is particularly advantageous in the case of a black toner.

The amount added is the amount necessary to adhere the toner particles uniformly and in a single layer on the surface, and depends on the particle size of the additive and toner particles,
Determined from specific gravity. Additives to be attached to the surface of toner particles are not limited to the above-mentioned substances, but may be used to further improve fluidity, developability, transferability, and storage stability, or to add toner particles to the surface of a photoconductor. Other additives may be added in order to prevent filming and improve the cleaning properties of the toner.

Conventionally, the narrower the particle size distribution of toner particles, the better, from 10μ to
20μ is said to be the best. When the particle size distribution is wide, large particles and small particles aggregate statically, reducing powder fluidity. This is probably because the toner composition is uneven depending on the particle size, so the toner is charged with different signs due to frictional charging, and the small particles are electrostatically attached to the surface of the large particles.
This is thought to be due to a decrease in powder fluidity. Furthermore, during the phenomenon, among small-sized particles.

It is said that a specific particle size is used, and if a magnetic toner with this wide distribution is used for a long time, the particle size distribution will gradually change, resulting in a decrease in image quality, smearing of the non-image area, and damage to the image. Phenomenon such as toner scattering around the area may occur.
It becomes unstable over time.

On the other hand, if a large amount of microparticles is present, toner scatters more easily due to an increase in the number of rotations of the sleeve and/or magnetic roll of the developing machine, making it easier to contaminate the inside of the machine. Fine particles have the disadvantage that they are difficult to clean.Furthermore, it is already known that the presence of a large amount of fine particles deteriorates powder flowability.

In addition, particles with a large particle size hardly contribute to the current Va and remain on the sleeve, resulting in poor image quality and reduced resolution. The reason for this is that when the particle size is large, the magnetic attraction force per toner particle is larger than when the particle size is small, and it tends to remain on the sleeve during development, and the contribution of electrostatic polarization force is large ( The chains formed by toner particles break (().

This is thought to be due to the fact that it tends to remain on the sleeve.

The present inventors investigated magnetic toners with various particle size distributions and found that the particle size was in the range of 5 to 35μ, the average particle size was 10 to 18μ, and the particle size was 8μ or less with a volume of 5 μm or less. It has been discovered that a certain toner has excellent powder fluidity, developability, transferability, cleaning/grindability, and stability over time, and is essential for a magnetic toner that does not contaminate the inside of a machine.

Next, an index showing the fluidity of powder will be explained. Conventionally, the fluidity of powder is often expressed in terms of the angle of repose, but this has problems with reproducibility and accuracy. In the present invention, this problem has been solved by expressing the fluidity of powder in terms of powder compressibility.

Powder compressibility is determined as follows.

First, toner is supplied to a cylindrical container through a decoration, and when it is lightly filled, the apparent density is ρ. seek. Next, while replenishing toner, this container is placed up and down on a measurement stand, the toner is compressed, and the density ρP is determined when the toner is packed to the closest density. Then, C=[(ρ −ρlz)/ρ
, )X100(%), and let C be the powder compressibility. Although the value of powder compressibility generally varies slightly depending on the shape, dimensions, and material of the container used for measurement, the container used in the present invention is a stainless steel cylindrical container with a diameter of 2.81 cW1% and a depth of 4.0 cm. The angle of repose is often used to express the fluidity of powder, but according to experiments by the present inventors, powder compressibility is much better, especially when using a small amount of sample (C reproducibility is good, and its value is It was found that it was easily determined and corresponded very well to fluidity.

Assuming that the range of 25 to 38% of the powder compressibility in the present invention is the angle of repose, it cannot be generalized due to the large error in the measurement of the angle of repose, but according to the measurements made by the present inventors, it is approximately It was 34° to 556°. Powder compressibility of the present invention: 25~
The magnetic toner having a particle diameter of 40 cm has excellent powder fluidity and has no problems in developability. The powder compressibility of the amorphous fine powder of the present invention is 30 to 55%, but by attaching additives to the toner surface, the powder compressibility becomes 25 to 40%.

The high-resistance magnetic toner of the present invention requires that the powder resistivity of the amorphous fine powder be 10,160α or more under an electric field of 10KV/α, and the compression resistivity of 10,140 or more under an electric field of 5KV/cm. . Furthermore, the powder resistivity after adhering additives to the surface of this amorphous fine powder is 1.0 Kv/c!
1015Ω or more under an electric field of 11, and a compression resistivity of 5
It needs to be 1012 Ωm or more under an electric field of KV7.

Observing the movement of the toner when it is conveyed by a magnetic roll and exhibiting the electrostatic m1 phenomenon, the magnetic toner moves violently due to the alternating magnetic field, and furthermore, the toner layer is considerably compressed in the second developing section. I understand what is happening. That is, if the state of the toner before transfer is called a static state, the toner during development can be said to be in an extremely dynamic state.

The present inventor focused on the difference in the state of the toner between development and transfer, and investigated resistance control of the magnetic toner. During development, that is, in a dynamic state, the probability of toner particles coming into contact with each other is an order of magnitude higher (and the contact area is also considered to be much larger) than during static transfer.Magnetic toner is a ferromagnetic material. It can be thought of as a composite material of a highly conductive material such as carbon black and a highly insulating material such as a binder resin, but if the concentration and dispersion state of the highly conductive material are appropriately controlled, static In this state, it has a relatively high resistance even under a high electric field, and in a dynamic state where the probability of contact between toner particles and the contact area is large, it is by no means impossible to make it slightly conductive under a high electric field.

The present inventor modeled this static state using the toner powder resistivity, and the dynamic state using the compression resistivity, which is the volume resistivity of a solid sample obtained by pressurizing toner particles. As a result of the study, it was found that the powder resistance of the amorphous fine powder was 10160 or more, and the compression resistivity was 10140σ or more, and the powder resistivity when the additive was attached was 101sΩ or more, and the compression resistivity was 10120 or more. It was confirmed that the above-mentioned materials had a high resistance, but the current permeability was sufficiently satisfactory.

Note that, in general, the compression resistivity always shows a lower value than the powder resistivity.

Conventionally, what has been described as the electrical resistance of magnetic toner corresponds to the powder resistivity in most cases, and this alone cannot sufficiently reflect the resistance during development. Furthermore, a detailed study of charge transfer in high-resistance magnetic toner has revealed that additives attached to the toner surface play an important role. Indirectly, as a method for measuring the charge exchangeability on the toner surface, the present inventors found that it is effective to measure the powder resistivity and compression resistivity in the presence and absence of additives. I discovered that. When the electric resistivity range required by the present invention is not satisfied, for example, when the powder resistivity of amorphous fine powder is 1015Ω, the compression resistivity is 10
When conductive or semiconductive fine powder is applied to the surface of amorphous fine powder, the powder resistivity is 1014.
Below Ωα, the compression resistivity is below 10100α, and the image is severely disturbed during transfer.

Unable to obtain satisfactory image quality. On the other hand, if an insulating additive is attached to the surface of the amorphous fine powder instead of a conductive or semiconductive additive, the powder resistivity becomes 10150 and the compression resistivity becomes 1012Ωα. Block method unevenness and white spots occurred, and high quality images could not be obtained. Furthermore, when similar studies were conducted on amorphous fine powder with a powder resistivity lower than this, the transferability was extremely reduced and unsatisfactory (image quality could not be obtained).

Note that the definition and measurement method of the electrical resistance value in the present invention are as explained below. In the present invention, the resistance value referred to as powder toner resistivity is determined from the value of current flowing between electrodes having a guard electrode and having a diameter of 5 cIn according to JIS K6911. However, the electrodes were made of brass instead of mercury, and highly insulating polytetrafluoroethylene resin was used as the insulator to hold them. Toner powder was uniformly filled between the electrodes to a thickness of 0.12±0.0251, and a load of about 50 fP/c11 was applied to ensure good contact with the electrodes. Thereafter, a DC voltage was applied, the current was measured, and this was converted into specific resistivity. For convenience, the value of the powder resistivity at an electric field of 10 KV/@ is adopted here. This is because the resistance value of high-resistance toner will have a large error when the electric field is lower than this, and the transfer electric field is approximately 10'V/cIn, so 1
This is because the device used in the present invention is filled with toner at a higher density than during transfer, so even an electric field lower than the transfer electric field sufficiently reflects the resistance value of the magnetic toner under the transfer electric field. Furthermore, if the measurement is performed using a higher electric field, some toner materials may generate heat, and there is a concern that the measured values may include noise.

On the other hand, the compression resistivity is determined by molding the toner powder under pressure at room temperature.
After forming a disk-shaped sample with a diameter of 5 cm and a thickness of about 2.5 cM, it was placed in close contact between brass electrodes with a diameter of 3.4 α and a guard electrode, and a DC voltage was applied. The current value is measured and converted into specific resistivity. Pressure molding of disc-shaped samples ranges from about 500 powder/6A to about 1000 K9/c-
d pressure for about 30 seconds.

This was done by applying pressure four times, changing the direction by 90'. The purpose of changing the forming pressure is to keep the porosity to 5 or less so that the resistivity of the compressed toner does not change due to voids in the pressure-molded sample. By molding the soft component (containing magnetic toner) in the binder resin at low pressure and the hard component (containing magnetic toner) by molding the hard component (containing magnetic toner) at high pressure, a sample with a certain amount of voids can be prepared. The pressure required for this was about 500 Kg/c!I to about 1000 Kf/-.The compression resistance defined in the present invention when the void in the pressure-molded sample is 5 or more: $ is the actual body of toner solid. Rather than bond resistivity, it should be referred to as the contact resistance of the toner powder under high filling and high contact conditions, and is considered to be a very effective indicator of the resistance of toner powder aggregates under dynamic conditions. .

For the compression resistivity, the value at an electric field of 5KV10n is adopted. This is due to the problem of errors in low electric fields, similar to the measurement of powder resistivity, and the fact that the current electric field is said to be 10 Kv/cM, but the Although it is not necessarily possible to specify a constant electric field value because there is a distribution in the potential of It was found that measurements could be made with an electric field lower than 104 /cfR. moreover.

As a result of various studies by the inventors, the electric field was 5 Kv/cr.
It was found that R is optimal.

Both powder resistivity and compression resistivity are at a temperature of approximately 25°C.

The volume resistance was calculated from the current value measured 1 minute after voltage application under conditions of approximately 60° humidity.

The magnetic toner of the present invention may be produced by any method, but
As a method for producing a magnetic toner made of amorphous fine powder having the above-mentioned particle size distribution and electrical resistance, internal additives are added as needed to the condensed M'M resin and magnetic powder, and the mixture is melt-kneaded. After cooling, it is mechanically pulverized into an amorphous fine powder.

The pulverization methods can be roughly divided into (1) a method in which the objects to be crushed are made to collide with each other to become fine powder (2)
There are two methods of pulverizing the objects without causing them to collide with each other. The latter pulverization method is preferable for use in the present invention, such as a turbo mill, etc.
Using this method, a finely ground product having a desired particle size distribution can be easily obtained. According to this method, the material to be crushed is crushed in a short bath in order to collide with the blades provided in the crushing chamber that rotate at high speed at a peripheral speed of 60 m/s or more, the walls of the crushing chamber, and the vortices generated inside the crushing chamber. Narrow particle size distribution (,
An irregularly shaped pulverized product with a uniform composition and a relatively smooth surface can be obtained.

The fine powder used as the magnetic toner is classified as necessary to obtain the above-mentioned particle size distribution.

Furthermore, the external additives described above are attached to the surface of this fine powder using Coulomb force, van der Waals force, or the like.

As a method of attaching external additives, this method is used to uniformly disperse external additives on the surface of fine toner powder.

In addition, a method was adopted that does not destroy, adhere, or fuse the fine toner powder. This method uses a stirrer (such as a Henschel mixer) having a stirring blade in a stirring chamber that rotates at a peripheral speed of 25 m/s or more to carry out the treatment in a short time, for example within several tens of seconds. The additive may be fixed to the surface of the toner particles.

The materials used for manufacturing the high-resistance magnetic toner of the present invention will be explained below.

First, the bristled resin material '#+ is not particularly limited, and basically any natural or synthetic resinous substance can be used. In particular, depending on various purposes, magnetic toners using two or more types of resins having incompatible components, magnetic toners having a structure in which a soft fraction is dispersed in a hard component, etc. It is effective as a pressure fixing toner used for fixing onto paper, etc.

By forming a continuous phase in the toner composition, the binder resin of magnetic toner for pressure fixing has a hard component that guarantees the toner's crushability, blocking resistance, impact resistance, powder fluidity, etc., and plasticity at room temperature. It is composed of a soft component that is capable of deformation and viscoelastic deformation and imparts pressure-sensitive deformability and adhesiveness to the toner assembly.

Each component is not necessarily limited to one type of resin (and may also be a copolymer having peripheral components).

Next, specific examples of these components will be shown. As the hard component, styrenic polymers obtained by homopolymerization of styrene or its derivatives or copolymerization with other polymerizable monomers, homopolymers of acrylic acid or methacrylic acid, or other polymerizable monomers. Examples include copolymers of alkyl methacrylate or copolymers thereof, polymers of vinyl chlorides or copolymers thereof, polysulfones, polyamides, polyesters, polybonates, and the like.

Soft components include diene polymers such as butadiene and isobray, or copolymers thereof, olefin polymers or copolymers thereof, vinyl acetate polymers or copolymers thereof, alkylene oxide polymers, silicone resins, and urethane. Polymers, polyesters, paraffin waxes, low molecular weight polyethylene, polypropylene, ethylene/vinyl acetate copolymers, ethylene/acrylic acid copolymers, ethylene oxide, organic acid-grafted polyethylene, and other low-molecular-weight crystalline polyolefins alone and in combination. The polymer may be selected from oxides, halides, saponified products, etc. of these, and low molecular weight crystalline polyamides, polyesters, etc.

Further, as the magnetic powder, any material exhibiting mother-sensitivity can be used. Examples include metals such as iron, nickel, cobalt, metal oxides, alloys, etc. In the case of magnetic toner, triiron tetroxide, iron sesquioxide, cobalt-4 added iron oxide, ferrite, nickel powder, etc. are used, and the amount added is determined by the development conditions, the type of magnetic material, and the electrical resistance. However, it is desirable that the amount is in the range of 40 to 70 parts by weight based on 100 parts by weight of the toner composition. The magnetic properties of the magnetic material also vary depending on the amount added and the development method, but the coercive force is 50 to 7000e, and the saturation magnetization is 50 to 2.
00 emu/y can be used. The particle size of the magnetic powder is determined in relation to the particle size of the toner, but for toner with a normal particle size of several tens of microns, the particle size is 0.
01 to 1μ, preferably about 0.05 to 0.5μ is easy to use. Further, the shape of the magnetic powder is not particularly limited. However, in order to achieve the resistance value required in the present invention, it is better to use granular magnetic powder rather than acicular magnetic powder (despite P containing a relatively large amount of magnetic powder, A magnetic toner with high resistance can be obtained.The reason for this is unknown, but due to factors such as the degree of exposure of the magnetic powder to the toner surface and the dispersibility of the magnetic powder within the toner particles, single-grain magnetic powder is better. It is speculated that the conductivity of toner particles can be lowered than that of acicular magnetic powder.Magnetic powder can stabilize the dispersibility in the binder resin and reduce the humidity dependence of the toner. For improvement, etc., the surface may be subjected to lipophilic treatment.

In addition, sublimable and non-sublimable dyes, pigments including extender pigments not intended for coloring, plasticizers, reinforcing agents, deterioration inhibitors, charge polarity control agents, etc. are added to the toner as necessary. can do.

Note that the developer agent of the present invention does not necessarily have to be composed of only one type of toner (it may be a mixture of two or more types of toner), and in some cases, it can be used in combination with carrier particles to form a two-component developer. It can also be used as a toner for heat fixing and flash fixing instead of pressure fixing.Furthermore, it can also be used to develop a latent image in a calm state. It is possible.

The present invention will be explained below with reference to Examples and Comparative Examples.
The invention is not limited by this description.

In addition, all "parts" in the examples mean parts by weight.Example 1 Polystyrene 30 parts Styrene-allyl alcohol copolymer 10 parts Low paper weight polyethylene 10 parts Granular triiron tetroxide
50 parts were mixed into 1 by using a rotor-rotating kneader.
10～! After kneading at 20'0 for 10 minutes, rolling with two rolls, cooling, coarsely pulverizing and finely pulverizing by mechanical pulverizing, and further using an air classifier as necessary, a magnetic toner having the particle size distribution shown in Table 1 was produced as a prototype. . The particle size distribution was measured using Microtrack (manufactured by Northrup & Leeds). When the powder resistivity and pressure wa low resistance were measured, the results were as shown in Table 1.

Carbon black (particle size 2
4 millimicrons, PFI 8.13) was added and mixed and deposited to obtain a cIi toner. The powder resistivity and compression resistance of this magnetic toner, as well as the powder compressibility were measured and the values are shown in Table 1. - Developed using a magnetic roll for the component block method, transferred to plain paper, and applied a linear pressure of 20 Kq/
Pressure fixing was performed using crtr. Table 2 shows the evaluation of the obtained image blur.

Table 2 The fixing properties were almost the same for the seven grades.

Example 2 Low molecular weight polystene 7 20 parts ethylene
Vinyl acetate copolymer 14 parts Ethylene-butadiene-ethylene copolymer 11 parts Granular triiron tetroxide
55 parts were produced in the same manner as in Example 1,
Particles with a particle size of 5μ or less and 35μ or more were removed using an air classifier, and the particles with an average particle size of 14μ and 8μ or less were adjusted to 5 volumes.

The resistivity of this amorphous fine powder was measured.

The powder toner resistivity was 2 x 10" ohms and the compressive resistance was 3 x 10" Qcm. This magnetic toner
When 0.3 parts of carbon black with a particle size of 24 millimicrons and a pH of 864 was mixed and deposited, the resistivity was measured, and the powder resistivity was 9X10'Ωm, and the compression resistivity was 1X1.
It was 0'Ω Sono. Furthermore, when the powder compressibility was measured, a value of 34% was obtained.

This magnetic toner was developed and transferred using the same copying machine as in Example 1 to obtain an image.
Image quality did not deteriorate even after 10,000 copies.

Comparative Example 1 Using the same materials as in Example 1, the same method as in Example 1 was used from mixing to coarse pulverization, followed by fine pulverization using a jet mill. The obtained fine powder has a very wide particle size distribution (5μ
In order to remove the following fine powders and coarse powders of 35 μm or more and obtain an amorphous fine powder having the same particle size distribution as in Example 2, three times as long the classification time as for the fine powder obtained by the mechanical pulverization method was required. The powder resistivity was 9×10”0m, and the compression resistivity was 7×10”Ωd.

Furthermore, the same carbon black was mixed and deposited in the same manner as in Example 2, and the resistivity was measured, and the powder resistivity was 2.
The powder compressibility was 46 cm. It is thought that this is a different method.Using this magnetic toner,
When development and transfer were carried out in the same manner as in Example 2, some unevenness occurred, which was thought to be due to uneven conveyance.

When the shapes of the S-type toners of Example 2 and Comparative Example 1 and the adhesion of additives were observed using an electron microscope, it was found that the toner surface of Comparative Example 1 had considerably thicker unevenness than that of Example 2. (The additive was unevenly distributed in the concave parts, and there were parts of the convex parts where no additive was observed.

Claims (1)

[Claims] 1. In a magnetic toner made of a mixture of an irregularly shaped fine powder containing magnetic powder in a binder resin and an additive attached to the surface of this fine powder, the average particle size of the irregularly shaped fine powder is 10~18μ
and its particle size distribution is 5 to 35μ, with a particle size of 8μ
A magnetic toner characterized in that the amount of the following fine powder is 5% by volume or less, and the powder compressibility of the mixture is 25 to 40%. 2. The amorphous fine powder has a powder resistivity of 10^1^6Ωcm or more under an electric field of 10KV/cm, and 5KV/cm.
The powder resistivity under an electric field of 10^1^4 Ωcm or more is 10^1^4 Ωcm, and the powder resistivity under an electric field of 10 KV/cm is 10^1^5 Ωcm or more and the powder resistivity under an electric field of 5 KV/cm is 10^1^4 Ωcm or more. The magnetic toner according to claim 1, having a compression resistivity of 10^1^2 Ω or more.