JP2002202629A - Magnetic toner, image forming method using the magnetic toner and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic toners which have excellent electrostatic charge uniformity and fixability and make it possible to obtain high-fineness images, an image forming method and a process cartridge. SOLUTION: The carbon element/iron element ratio existing on the surfaces of toner particles of the magnetic toners measured by ESCA is <0.001; the magnetic toners satisfying the relation D/C<=0.02 when the diameter corresponding to the projection area of the magnetic toners is defined as C and the minimum value of the distance between the iron oxide and the surfaces of the toners particles in sectional observation of the magnetic toners using a transmission type electronic microscope(TEM) as D is >=50 number %, the average circularity of the magnetic toners is >=0.970, the peak top of the main peak in the molecular weight distribution measured by gel permeation chromatography(GPC) of the THF soluble component of the magnetic toners exists at a range of a molecular weight 5,000 to 50,000, X calculated by equation (I) is <=1.4 and the toners have fine inorganic powder on the surfaces of the toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner used in a recording method utilizing an electrophotographic method, an electrostatic recording method, a magnetic recording method, a toner jet recording method and the like, and an image forming method. More specifically, the present invention relates to a magnetic toner used for a copying machine, a printer, and a facsimile, which forms a toner image on an electrostatic latent image carrier in advance, and then transfers the image onto a transfer material to form an image. Regarding the cartridge.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. Generally, a photoconductive substance is used, and an electrostatic image carrier (hereinafter referred to as "photoconductor") is used by various means.
An electric latent image is formed thereon, and then the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a transfer material such as paper. A copy is obtained by fixing a toner image thereon.

As a method for visualizing an electric latent image, a cascade developing method, a magnetic brush developing method, a pressure developing method and the like are known.

US Pat. No. 3,909,258 proposes a method of developing using a magnetic toner having electrical conductivity. In this technique, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and the toner is brought into contact with an electrostatic image for development. At this time, in the developing unit, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and electric charges are guided to the toner particles from the sleeve via the conductive path. The toner particles adhere to the image area by the Coulomb force and are developed. This developing method using a conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method.On the other hand, since the toner is conductive, the developed image can be transferred from a recording medium to plain paper or the like. There is a problem that it is difficult to transfer electrostatically to the final supporting member.

As a developing method using a high-resistance magnetic toner capable of electrostatic transfer, there is a developing method utilizing dielectric polarization of toner particles. However, such a method has a problem that the developing speed is essentially low and the density of a developed image is not sufficiently obtained, and is practically difficult.

As another developing method using a high-resistance insulating magnetic toner, toner particles are frictionally charged by friction between the toner particles, friction between the toner particles and a sleeve, and the like, and this is charged to an electrostatic image holding member. A method of developing by contact is known. However, in this method, the number of times of contact between the toner particles and the friction member is small, and the magnetic toner used has a large amount of magnetic material exposed on the surface of the toner particles. There is such a problem.

For example, Japanese Patent Application Laid-Open Nos.
In JP-A-55-18656, for example, a magnetic developer is thinly coated on a developer carrying member, frictionally charged, and then brought close to and in contact with an electrostatic latent image under the action of a magnetic field. A so-called jumping development method has been disclosed. According to this method, it is possible to apply sufficient frictional charging of the developer by applying the magnetic developer thinly on the developer carrier, and to develop the developer without contacting the electrostatic latent image while supporting the developer by magnetic force. Is performed, transfer of the developer to the non-image portion, that is, fogging is suppressed, and a high-definition image can be obtained.

[0008] Such a one-component developing system does not require carrier particles such as glass beads and iron powder as in the two-component developing system, and thus the developing apparatus itself can be reduced in size and weight. Moreover,
In the two-component developing method, since it is necessary to keep the toner concentration in the developer constant, a device for detecting the toner concentration and supplying a necessary amount of toner is required. Therefore, the developing device also becomes large and heavy here. In the one-component developing system, such an apparatus is not required, so that it is preferable because it can be made small and light.

However, the developing method using the insulating magnetic toner has an unstable factor relating to the insulating magnetic toner to be used. The reason for this is that a considerable amount of fine powdered magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. The characteristics of the magnetic toner are changed, and as a result, various characteristics required for the magnetic toner, such as development characteristics and durability of the magnetic toner, are changed or deteriorated.

When the conventional magnetic toner containing a magnetic material is used, the above-mentioned problem is considered to be largely caused by the magnetic material being exposed on the surface of the magnetic toner. That is, by exposing the magnetic fine particles having relatively lower resistance than the resin constituting the toner on the surface of the magnetic toner, the toner charging performance is reduced, the toner fluidity is reduced, and further, the In use, the deterioration of the developer such as a decrease in image density due to the peeling of the magnetic material due to the rubbing between the toner or the regulating member and the occurrence of uneven density called a sleeve ghost are caused.

Conventionally, proposals have been made regarding magnetic iron oxide contained in magnetic toners, but they still have points to be improved.

For example, Japanese Patent Application Laid-Open No. 62-279352 proposes a magnetic toner containing a magnetic iron oxide containing a silicon element. Although such a magnetic iron oxide intentionally causes a silicon element to be present inside the magnetic iron oxide, there is still a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.

Further, Japanese Patent Publication No. 3-9045 proposes that the shape of magnetic iron oxide is controlled to be spherical by adding a silicate. In the magnetic iron oxide obtained by this method, a large amount of silicon element is distributed inside the magnetic iron oxide because silicate is used for controlling the particle shape, and the amount of the silicon element on the surface of the magnetic iron oxide is small, The fluidity of the magnetic toner is improved to some extent due to the high smoothness of the magnetic iron oxide, but the adhesion between the binder resin and the magnetic iron oxide constituting the magnetic toner is insufficient.

In Japanese Patent Application Laid-Open No. 61-34070,
There has been proposed a method for producing ferric oxide by adding a hydrosilosilicate solution during the oxidation reaction to ferric oxide. Although triiron tetroxide according to this method has a Si element near the surface, the Si element exists in a layer near the surface of the triiron tetroxide, and the surface is vulnerable to mechanical shock such as friction. Have a point.

On the other hand, the toner is prepared by melting and mixing a binder resin, a colorant, and the like, uniformly dispersing the mixture, pulverizing the mixture with a fine pulverizer, and classifying with a classifier to obtain a toner having a desired particle size. Pulverization method), but there is a limit to the selection range of materials for reducing the toner particle size. For example, the resin colorant dispersion must be sufficiently brittle and capable of being pulverized with economically available manufacturing equipment. From this request,
In order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed. Particles) are included in this. Further, such a highly brittle material often undergoes further pulverization or pulverization when used as a developing toner in a copying machine or the like.

In the pulverization method, it is difficult to completely and uniformly disperse solid fine particles such as a magnetic powder or a colorant in a resin, and depending on the degree of dispersion, fog increases and image density decreases. Cause. In addition, the grinding method
In essence, the magnetic iron oxide particles are exposed on the surface of the toner, so that there remains a problem in the fluidity of the toner and the charging stability in a severe environment.

That is, in the pulverization method, there is a limit to the fineness of the toner required for high definition and high image quality, and the powder characteristics, particularly, the uniform charging property and fluidity of the toner are significantly attenuated.

In order to overcome the problems of the toner by the pulverization method as described above and to satisfy the above-mentioned requirements, a method of producing a toner by a suspension polymerization method has been proposed.

The toner obtained by suspension polymerization (hereinafter referred to as “polymerized toner”) can be easily made into fine particles. Further, since the obtained toner has a spherical shape, it has excellent fluidity and high image quality. It is advantageous for conversion.

However, when a magnetic material is contained in the polymerized toner, its fluidity and charging characteristics are significantly reduced. This is because the magnetic particles are generally hydrophilic and thus easily exist on the toner surface. To solve this problem, it is important to modify the surface characteristics of the magnetic material.

Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, JP-A-59-200254, JP-A-59-200256,
JP-A-59-200257 and JP-A-59-224102 have proposed various silane coupling agent treatment techniques for magnetic substances.In JP-A-63-250660, silicon element-containing magnetic particles are disclosed. Is disclosed with a silane coupling agent, and JP-A-7-72654 discloses a technique of treating magnetic iron oxide with an alkyltrialkoxysilane.

However, although the dispersibility in the toner is improved to some extent by these treatments, there is a problem that it is difficult to uniformly render the surface of the magnetic material hydrophobic.
Therefore, it is impossible to avoid coalescence of the magnetic substances and generation of magnetic particles that are not hydrophobized, which is insufficient to improve the dispersibility in the toner to a satisfactory level.

Japanese Patent Application Laid-Open No. H11-163873 discusses a special toner in which magnetic particles are contained only in a specific portion inside the particles.
It has already been disclosed in JP-A-7-209904.

However, JP-A-7-209904 does not mention the circularity of the disclosed toner.

Further, the toner configuration disclosed in Japanese Patent Application Laid-Open No. 7-209904 can be summarized as follows. From the structure in which a resin layer free of magnetic particles is formed near the surface of toner particles with a thickness of a certain amount or more. Which consists of
This means that a considerable portion of the toner surface layer portion where no magnetic particles exist is present. However, in other words, when such a developer has a small average particle size of, for example, 10 μm, the volume in which the magnetic particles can exist is small, and thus it is difficult to include a sufficient amount of the magnetic particles. Moreover, in such a developer, the ratio of the surface resin layer in which the magnetic particles are not present differs between the developer particles having a large particle size and the developer particles having a small particle size in the particle size distribution of the developer. Thus, the content of the magnetic substance included therein is different, and the developability and the transferability also differ depending on the particle size of the developer, that is, the selective developability depending on the particle size is easily observed. Therefore, when printing is performed for a long time using a magnetic developer having a non-uniform particle size, particles containing a large amount of magnetic material and difficult to develop, that is, developer particles having a large particle size are likely to remain, and the image density and image quality are reduced, and further, the fixing property is reduced. Also leads to worsening.

On the other hand, LED and laser beam printers have become the mainstream of the printer market in recent years, and the direction of technology has been changed to higher resolution, that is, from 240, 300 dpi to 400, 600, 800 dpi. It is coming. Accordingly, higher definition has been required for the developing system. In addition, the functions of the copiers have also been enhanced, and therefore the digital copying machines are moving toward digitalization. In this direction, a method of forming an electrostatic charge image with a laser is mainly used, so that the direction is also moving toward a high resolution direction. Here, as in the case of a printer, a high-resolution and high-definition developing method has been required, and Japanese Patent Application Laid-Open Nos. 1-112253 and 2-284158 propose toners having a small particle size. However, a toner having a small particle diameter has more difficulty in uniformly dispersing and encapsulating a magnetic powder, and the various problems described above have not been sufficiently solved.

Also, a method of adding inorganic fine particles as an external additive to toner base particles has been proposed and widely used for the purpose of improving the flow characteristics, charging characteristics, etc. of the toner. For example, JP-A-5-66608, JP-A-4-9860 and the like, inorganic fine particles that have been subjected to a hydrophobic treatment or inorganic fine particles that have been subjected to a hydrophobic treatment and then treated with a silicone oil or the like, or -249059, JP-A-4-264453
JP-A-5-346682 discloses a method in which hydrophobically treated inorganic fine particles and silicone oil-treated inorganic fine particles are added in combination. However, these proposals also have room for further improvement in improving the above-mentioned problem when toner particles having a smaller particle size are used to increase the resolution.

In recent years, it has become very important to save space, reduce costs, and reduce power consumption by reducing the size of copiers and printers. It is needed. Along with this, the viscosity of the toner at the time of melting is reduced so that the toner can exhibit sufficient fixability with a low calorie and a low pressure,
It is necessary to increase the area of adhesion to the fixing substrate, and for this purpose, it is required to reduce the Tg and the molecular weight of the binder resin used. However, a toner mainly composed of a soft component has a problem that it is difficult to achieve compatibility with high-temperature offset resistance, and further, there is a problem that developability and storage characteristics are impaired and sticking to a photoreceptor easily occurs.

Various proposals have been made for improving the fixing property since ancient times. For example, in Japanese Patent Publication No. 51-23354,
Polymerization of monomers such as styrene in the presence of a crosslinking agent and a molecular weight modifier to obtain a moderately crosslinked resin, kneading and pulverizing it with carbon black, etc. to improve hot offset resistance and low temperature fixability A pulverized toner has been proposed. Japanese Patent No. 2,681,91 discloses that a styrene-based binder resin containing 10 to 60% by weight of a THF-insoluble component based on the binder resin is melt-kneaded together with a magnetic material, a charge control agent and wax.
A ground pulverized toner is disclosed. According to these publications, the THF insoluble component (crosslinking component) of the binder resin is cut by melt-kneading to produce a high molecular weight component, whereby a toner having improved hot offset resistance and low-temperature fixability can be obtained. . However, as long as the method of thermally and mechanically cutting the insoluble components of the binder resin is used, the soluble component generated by cutting the molecular chain has a considerably wide molecular weight distribution. Therefore, there is almost no effect on the high-temperature offset resistance, and many components having an intermediate molecular weight that hinder the low-temperature fixing property are generated, and it cannot be said that both low-temperature fixing property and high-temperature offset resistance have been achieved.

Japanese Patent Application Laid-Open No. 5-06029 discloses that a crosslinking agent which is crosslinked with a crosslinking agent having two or more vinyl groups and which is kneaded with a binder resin having a carboxyl group and an organometallic compound is heated to knead. Carboxyl groups and metal ions are cross-linked with metal while cutting with force, resulting in 5% or more of 5,000,000 or more components in the molecular weight distribution of the binder resin component.
Thus, a method for producing a pulverized toner having an Mw of 5,000,000 or more is disclosed. According to the publication, a toner having excellent resistance to high-temperature offset can be obtained. However, even in this case, a component having an intermediate molecular weight is inevitably generated, so that there is room for further improvement in low-temperature fixability. Furthermore, the above-listed pulverized toner has a problem that its circularity is low and its transfer efficiency is low.
Since a large amount of magnetic powder is exposed on the surface of the toner particles, there is a problem in fluidity and uniform chargeability of the toner.

On the other hand, in the case of the polymerized toner, unlike the pulverized toner, the toner can be directly produced without a melt-kneading step, so that the insoluble matter (cross-linking component) generated during the polymerization does not cut off, and is extremely resistant. It is excellent in that a toner having a high offset property can be obtained. However, on the other hand, insolubles also have a significant effect on low-temperature fixability, and it is possible to balance low-temperature fixability and high-temperature offset resistance by minimizing insolubles, but further improvements is necessary.

JP-A-11-38678 discloses a molecular weight of 1,000,000
A non-magnetic polymerized toner having 0 to 20% of the above components, 0 to 60% of a THF-insoluble content, and 1 to 60% of the total thereof is disclosed. However, this publication discloses a technique for a non-magnetic toner, and there is room for improvement for a magnetic polymerization toner containing a magnetic powder. In addition, patent 2749
No. 234 discloses a method for producing a magnetic toner in which the wax component in the toner is in a fibrous form.In the publication, a polymerizable crosslinking agent is added to a monomer composition containing magnetic powder, A magnetic polymerization toner is obtained using an azo polymerization initiator.

Japanese Patent No. 2749122 discloses a method of treating a magnetic powder with a polymer having a specific reactive group on the surface thereof. A magnetic polymerized toner is obtained by adding to the monomer composition and using an azo-based polymerization initiator. However, when inferred from the amount of the crosslinking agent added, the type and amount of the polymerization initiator described in these publications, and the polymerization temperature, the THF-insoluble matter is excessively generated, or the intermediate formed due to extremely weak crosslinking. Since the proportion of the component having the molecular weight increases, there is a problem in the fixing property in the case of the magnetic toner containing a large amount of the magnetic powder. Further, the magnetic polymerized toners obtained according to these publications have insufficient hydrophobicity treatment of the magnetic powder used, and have problems in fluidity and charging characteristics.

It is known that a monomer is polymerized in the presence of a chain transfer agent in the production of a resin for a toner in order to improve the low-temperature fixability of the toner. For example, JP-A-58-11955 discloses that a high molecular weight resin is first produced by suspension polymerization of styrene and an acrylic monomer, and then a monomer such as styrene and α-methylstyrene dimer as a chain transfer agent are added. Further, a mixture of a high molecular weight resin and a low molecular weight resin is obtained by performing polymerization. However, the resin produced according to the publication has insufficient high-temperature offset resistance. Further, Japanese Patent No. 2965853 discloses a toner having a small content of fine particles obtained by polymerizing a monomer composition containing a colorant and α-methylstyrene dimer, and then subjecting the resultant to coagulation heat treatment and pulverization. However, since the toner composition does not contain a cross-linking agent in the monomer composition, it does not contain any insoluble components or high molecular weight components, which causes a problem in high-temperature offset resistance. Further, JP-A-9-230628 discloses that a composition comprising a coloring agent, a wax and a monomer is polymerized by an emulsion polymerization method in the presence of a chain transfer agent such as t-dodecyl mercaptan or α-methylstyrene dimer, and thereafter, Further, a toner which is aggregated by heating is disclosed, but also has a problem in high-temperature offset resistance because there is no insoluble component.

Conventionally, as an image forming method, an electrostatic recording method,
Many methods such as a magnetic recording method and a toner jet method are known. For example, in electrophotography, an electric latent image is generally formed on a photoconductor using a photoconductive substance as a latent image carrier by various means, and then the latent image is developed with toner. After a toner image is transferred to a recording medium such as paper as needed as a visible image, the toner image is fixed on the recording medium by heat, pressure or the like to obtain an image. Generally, when a toner having a high and uniform charge amount distribution is used, transfer efficiency is high. However, as described above, such a toner has not been obtained with a magnetic toner.

It is said that spherical toner has high transfer efficiency because of its shape. In this regard, JP-A-61-27986
Japanese Patent Application Laid-Open No. 63-235953 proposes a magnetic toner which is made spherical by a mechanical impact force. However, the transfer efficiency of these toners is still insufficient, and further improvement is needed.

On the other hand, such a spherical toner has the advantage that the transfer efficiency is higher than that of the pulverized toner, but also has the property that it is difficult to clean because of the spherical shape.
Furthermore, as described above, the toner particle size is in the direction of smaller particle size, and it is more difficult to completely remove the transfer residual toner. However, by improving the cleaning device, it is possible to suppress toner slippage to a level that does not cause a serious problem, and it is possible to form an image having no practical problem in the conventional image forming method having a corona charging method. It was possible. However, in recent years, primary charging and transfer processes using corona discharge, which have been conventionally used from the viewpoint of environmental protection, have been replaced with primary charging (contact charging) using a photosensitive member contacting member having great advantages such as low ozone and low power. ), The transfer process (contact transfer) is becoming mainstream.

For example, JP-A-63-149669 and JP-A-Hei 2
-123385 has been proposed. These are related to a contact charging method and a contact transfer method, in which a conductive elastic roller is brought into contact with a photoconductor, and the surface of the photoconductor is uniformly charged while applying a voltage to the conductive roller. After obtaining the toner image by the developing process, while pressing another conductive roller to which a voltage is applied to the photoconductor, the transfer material is passed during the pressing, and the toner image on the photoconductor is transferred to the transfer material. A copy image is obtained through a fixing process. However, it has been found that the contact charging method or the contact transfer method has an alarming problem, unlike the case of using corona discharge.

Specifically, in the case of the contact charging method, first, the charging member is pressed against the surface of the photosensitive member with a pressing pressure.
Therefore, it is difficult to maintain sufficient contact between the contact charging member and the photoreceptor due to the presence of the untransferred residual toner, that is, the residual toner after transfer, and the chargeability is deteriorated. Transfer of the toner, that is, fogging is likely to occur. Further, since the toner is accumulated on the charging member, the photosensitive member cannot be uniformly charged, resulting in a decrease in image density and roughness. Further, since the charging member is in pressure contact, toner fusion is likely to occur, and these tendencies become more remarkable as the transfer residual toner increases.

Next, in the case of the contact transfer method, the transfer member is brought into contact with the photoreceptor via the transfer member at the time of transfer, so that the toner image formed on the photoreceptor is transferred to the transfer material. Are pressed against each other, which causes a problem of partial transfer failure called so-called "missing transfer". In addition, as the direction of technology in recent years, a higher resolution and higher definition developing method has been required, and in order to respond to such a demand, the particle diameter of the toner has been reduced, but this has been progressing. As described above, as the toner particle size becomes smaller, the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photoreceptor becomes larger than the Coulomb force applied to the toner particles in the transfer process, and as a result, the transfer residue is reduced. As a result, the amount of toner increases, and the transfer failure tends to be further deteriorated. As described above, in an image forming method using a contact charging method and a contact transfer method, which are very preferable in consideration of the environment, it is desired to develop a magnetic developer having high transferability, excellent charge stability, and less likely to cause toner fusion. It is rare.

[0041]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner which solves the above-mentioned problems of the prior art. That is, an object of the present invention is to provide a magnetic toner which is excellent in charge uniformity and fixability and can obtain a high-definition image, an image forming method using the toner, and a process cartridge. Another object of the present invention is to provide a magnetic toner which is less likely to cause image defects even when used for a long period of time and has excellent transferability, an image forming method using the toner, and a process cartridge.

[0042]

According to the present invention, there is provided a magnetic toner having toner particles containing at least a binder resin component and iron oxide, wherein i) the toner particles have a surface which is measured by X-ray photoelectron spectroscopy. Ratio of the content (B) of the iron element to the content (A) of the existing carbon element (B / A)
Is less than 0.001, and ii) the projected area equivalent diameter of the magnetic toner is C, and the minimum value of the distance between iron oxide and the surface of the toner particles in cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM) is D. The magnetic toner satisfying the relationship of D / C ≦ 0.02 is 50% by number or more, iii) the average circularity of the magnetic toner is 0.970 or more, and iv) a gel of a THF-soluble component of the magnetic toner. In the molecular weight distribution measured by permeation chromatography (GPC),
There is a peak top of the main peak in the molecular weight range of 5,000 to 50,000, and X calculated from the following formula (1) is 1.4 or less;

[0043]

(Equation 2) V) A magnetic toner having an inorganic fine powder on the surface of a toner particle, an image forming method using the toner, and a process cartridge.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <1> Magnetic Toner of the Present Invention The magnetic toner of the present invention has toner particles containing at least a binder resin component and iron oxide.

The present inventors have conducted intensive studies on the uniformity and stabilization of the charging of the magnetic toner so far.
The ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface of the magnetic toner measured by X-ray photoelectron spectroscopy is less than 0.001, and the following formula (2) It has been found that setting the average circularity of the toner to 0.970 or more, which is calculated from the circularity determined by the above, is extremely effective for uniforming and stabilizing the chargeability of the toner, and has reached the present invention. .

[0046]

(Equation 3) (In the formula, L ₀ indicates the peripheral length of a circle having the same projected area as the particle image, and L indicates the peripheral length of the projected image of the particle.) Further, by using the above toner, the toner The photoreceptor is also used in an image forming method that combines a cleaner-less structure and contact charging in which a ghost image is easily generated due to poor collection of a toner, and an image forming method that includes a contact charging step, a one-component non-contact developing step, and a contact transfer step. It has been found that shaving, charging failure and transfer failure are remarkably suppressed, and a high-definition image free from fog and other image defects can be stably obtained even when used for a long period of time.

This has been difficult to achieve with a magnetic toner using magnetic iron oxide which has been generally used in the past.

The reason is that the magnetic iron oxide to be used has not been sufficiently and uniformly hydrophobized.

When a magnetic toner is produced, the dispersibility of the magnetic iron oxide particles in the toner binder resin component can be improved by using magnetic iron oxide whose surface has been hydrophobized. Further, even when a large amount of magnetic iron oxide is exposed on the surface of the toner particles, if the surface of the magnetic iron oxide is uniformly subjected to the hydrophobic treatment, the charging performance of the toner is hardly impaired under any environment.

Therefore, various methods for hydrophobizing the surface of magnetic iron oxide have been proposed. However, with the conventional methods, it is difficult to obtain magnetic iron oxide sufficiently and uniformly hydrophobized. In addition, when a large amount of a treating agent or the like or a highly viscous treating agent or the like is used, although the degree of hydrophobicity is certainly increased, coalescence of particles occurs, and both the hydrophobicity and the dispersibility are not necessarily satisfied. Not achieved.

Generally, the surface of an untreated iron oxide has a hydrophilic property, so that it is necessary to make the hydrophilic iron oxide hydrophobic in order to obtain a hydrophobic iron oxide. According to the method, the uniformity of hydrophobicity is insufficient, and the conventional toner using such iron oxide varies in chargeability depending on humidity and the like, and lacks stability.

On the other hand, the iron oxide used as a magnetic material in the toner of the present invention has a very high level of uniformity of hydrophobicity. In particular,
For example, when hydrophobizing iron oxide, it is an iron oxide obtained by performing a surface treatment while hydrolyzing a coupling agent while dispersing the iron oxide to a primary particle size in an aqueous medium. In the hydrophobic treatment method in an aqueous medium, the coalescence of iron oxide particles is less likely to occur than in a gas phase treatment, and the charge repulsion between the iron oxide particles due to the hydrophobic treatment acts. Since the surface treatment is performed in a substantially primary particle state, high uniformity of hydrophobicity is achieved.

The method of treating the iron oxide surface while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas such as chlorosilanes or silazanes, and furthermore, In the gas phase, iron oxide particles are easily united with each other, and a high-viscosity coupling agent, which has been difficult to treat well, can be used, and the effect of hydrophobization is enormous. Examples of the coupling agent that can be used in the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the following general formula (I).

[0054]

## STR1 R _m SiY _n (I) (wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y is an alkyl group, vinyl group, glycidoxy group, a hydrocarbon group such as methacryl group And n represents an integer of 1 to 3, provided that m + n = 4.) Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane,
Examples include hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane. In particular, the iron oxide is preferably subjected to a hydrophobic treatment in an aqueous medium using an alkyl trialkoxysilane coupling agent represented by the following general formula (II).

[0055]

Embedded image C _p H _{2p + 1} —Si— (OC _q H _{2q + 1} ) ₃ (wherein p represents an integer of 2 to 20 and q represents an integer of 1 to 3) p in the above formula Is smaller than 2, the hydrophobizing treatment is easy, but it may be difficult to impart sufficient hydrophobicity. If p is larger than 20, the hydrophobicity is sufficient, but the iron oxide particles are In some cases, making it difficult to sufficiently disperse the iron oxide particles in the toner.

When q is larger than 3, the reactivity of the silane coupling agent is reduced, and it is difficult to sufficiently perform the hydrophobic treatment.

In particular, alkyl in which p represents an integer of 2 to 20 (more preferably an integer of 3 to 15) and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). It is preferable to use a trialkoxysilane coupling agent.

The treatment amount is based on 100 parts by mass of iron oxide.
The content is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass.

In the present invention, the aqueous medium is a medium containing water as a main component. Specifically, water itself as an aqueous medium, one obtained by adding a small amount of a surfactant to water,
Examples thereof include those obtained by adding a pH adjuster to water and those obtained by adding an organic solvent to water. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass based on water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.

The stirring is performed, for example, by a mixer having a stirring blade (specifically, a high shear mixing device such as an attritor or a TK homomixer) so that the iron oxide particles become primary particles in an aqueous medium. It is good to do enough. Since the surface of the thus obtained iron oxide is uniformly subjected to a hydrophobic treatment, when used as a toner material, the iron oxide has a very good dispersibility in the toner and does not expose from the toner surface. Therefore, by using such iron oxide, X
It is possible to obtain the toner of the present invention in which the ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface of the toner measured by linear photoelectron spectroscopy is less than 0.001. It is possible to achieve uniformity and stabilization of toner charging, and by using this toner,
High image quality and high durability stability can be achieved. Furthermore, (B
When the ratio (A) is less than 0.0005, the chargeability and the stability are further improved.

The iron oxide used as a magnetic material in the toner of the present invention includes phosphorus, cobalt, nickel,
It may contain elements such as copper, magnesium, manganese, aluminum, and silicon, and contains iron tetroxide or γ-iron oxide as a main component, and may be used alone or in combination of two or more. These iron oxides have a BET specific surface area of preferably ² to 30 m ² / g, particularly 3 to 28 m ² / g by the nitrogen adsorption method.
And those having a Mohs' hardness of 5 to 7 are more preferable.

The shape of the iron oxide is octahedron, 6
There are various shapes such as a face, a sphere, a needle, a scale, and the like, and an octahedron, a hexahedron, a sphere, and an amorphous material having a small anisotropy are preferable for increasing the image density. Such a shape can be confirmed by SEM or the like. As the particle size of the iron oxide, in the measurement of the particle size of the particles having a particle size of 0.03 μm or more, the volume average particle size is 0.1 to 0.3 μm, and 0.03 to 0.1 μm particles are 40% by number or less. It is preferred that

When an image is obtained from a magnetic toner using iron oxide having a volume average particle size of less than 0.1 μm, the color of the image shifts to reddish, and the blackness of the image becomes insufficient. It is generally not preferable, for example, the tendency that reddish taste is strongly felt. In addition, since the surface area of the iron oxide increases, the dispersibility decreases, and the energy required during production increases, which is not efficient. Further, the effect of iron oxide as a coloring agent is weakened, and the density of an image may be insufficient, which is not preferable.

On the other hand, if the volume average particle diameter of the iron oxide exceeds 0.3 μm, the mass per particle becomes large, so that there is a high probability that the iron oxide is exposed on the toner surface due to the difference in specific gravity with the binder resin component during production. Undesirably, the possibility of the production equipment becoming worn or the like becoming remarkable increases, and the sedimentation stability of the dispersion decreases.

In the toner, 0.1% of the iron oxide was used.
If the particle size of μm or less exceeds 40% by number, the surface area of iron oxide
Increases, the dispersibility decreases, and aggregates occur in the toner.
And the toner's chargeability is impaired and coloring power is reduced.
To be less than 40% by number
Is preferred. Furthermore, if the number is 30% or less, the tendency
Is more preferable because it becomes smaller. These iron oxides
As for the magnetic characteristics, the saturation magnetization is 10 under a magnetic field of 795.8 kA / m.
~ 200Am ^Two/ kg, remanent magnetization 1-100 Am^Two/ kg, coercive force is 1 ~ 30
What is kA / m is used.

The volume average particle size of iron oxide can be measured using a transmission electron microscope (TEM). In particular,
A transmission electron microscope (T
EM), the diameter of 100 iron oxide particles in the visual field is measured, and the volume average particle diameter is determined.

As a specific observation method using the above-mentioned TEM, as a method for observing, the particles to be observed are sufficiently dispersed in a room-temperature curable epoxy resin, and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. A method of observing an object as a flaky sample using a microtome provided with diamond teeth is exemplified.

The specific surface area is obtained by adsorbing nitrogen gas on the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) according to the BET method and calculating the specific surface area using the BET multipoint method. be able to. The iron oxide used in the toner of the present invention is produced, for example, by the following method.

An aqueous solution containing ferrous hydroxide is prepared by adding an equivalent such as sodium hydroxide to the aqueous ferrous sulfate solution in an amount equivalent to or more than the iron component. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or more (preferably pH 8 to 10), and while the aqueous solution is heated to 70 ° C. or more, an oxidation reaction of ferrous hydroxide is carried out. First, a seed crystal is produced.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate based on the amount of the alkali added previously is added to the slurry-like liquid containing the seed crystals. The reaction of ferrous hydroxide is promoted while blowing air while maintaining the pH of the solution at 6 to 10 to grow magnetic iron oxide particles with the seed crystal as a core. The pH of the solution shifts to the acidic side as the oxidation reaction proceeds, but it is preferable that the pH of the solution is not less than 6. At the end of the oxidation reaction, adjust the pH of the solution, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, mix and stir well, filter, dry, and lightly disintegrate after stirring. By doing so, hydrophobized magnetic iron oxide particles can be obtained. Or,
After completion of the oxidation reaction, the iron oxide particles obtained by washing and filtration are redispersed in another aqueous medium without drying, and the pH of the redispersed liquid is adjusted. A coupling treatment may be performed by adding a ring agent.

In any case, it is important to hydrophobize the untreated iron oxide particles generated in the aqueous solution in the state of a water-containing slurry before passing through a drying step. This is because if untreated iron oxide particles are dried as they are, coalescence due to agglomeration of the particles is inevitable. Even if wet agglomerated treatment is applied to such agglomerated powder, a uniform hydrophobizing treatment is performed. In the toner using such a surface-treated iron oxide, B / A <, which is a feature of the magnetic toner of the present invention, is used.
It is difficult to achieve 0.001.

As the ferrous salt, generally, iron sulfate produced as a by-product in the production of titanium sulfate, iron sulfate produced as a by-product of cleaning the surface of a steel sheet, and iron chloride can be used. is there. The method for producing magnetic iron oxide by the aqueous solution method generally uses an iron concentration of 0.5 to 2 mol / liter based on the prevention of an increase in viscosity during the reaction and the solubility of iron sulfate. Generally, the lower the concentration of iron sulfate, the smaller the particle size of the product tends to be. In addition, in the reaction, as the amount of air is larger and the reaction temperature is lower, the particles are easily atomized.

By using the thus-prepared hydrophobized iron oxide particles for a toner, a toner of the present invention having excellent image characteristics and stability can be obtained.

Incidentally, in Japanese Patent Publication No. 60-3181,
A method for producing a magnetic polymerized toner containing magnetic fine particles whose surface is wet-treated with a silane coupling agent is disclosed.

However, Japanese Patent Publication No. 60-3181 discloses that
The description relates to wet surface treatment of an untreated magnetic substance in a dry powder form with a silane coupling agent.
In such untreated dry magnetic powders, coalescence of particles due to primary aggregation during drying is inevitable, so that it is difficult to uniformly hydrophobize the individual magnetic particles even with a wet surface treatment. . Therefore, even when a polymerized toner is produced using such a surface-treated magnetic material, it is difficult to achieve B / A <0.001 which is a characteristic of the toner according to the present invention.

When the projected area equivalent diameter of the toner is C and the minimum value of the distance between the iron oxide and the surface of the toner particles in cross-sectional observation of the toner using a transmission electron microscope (TEM) is D, C / D ≦ C The number of toners satisfying the relationship of 0.02 is 50
% Is also one of the features of the toner of the present invention.

In the present invention, the number of toners satisfying the relationship of D / C ≦ 0.02 is 50% or more, preferably 65% or more, and more preferably 75% or more.

When the number of toners satisfying the relationship of D / C ≦ 0.02 is 50
%, The magnetic particles do not exist at least outside the boundary of D / C = 0.02 in the majority of toners. Assuming that such particles are spherical, if one toner particle is defined as the entire space, at least the space where iron oxide does not exist is located at least on the surface of the toner particle.
11.5% will be present. In fact, it is clear that the iron oxide is more than 12% because the iron oxide is not uniformly arranged at the closest position so as to form an inner wall inside the toner particle. In the toner composed of such particles, various adverse effects are likely to occur as described above.

In the present invention, specific D by TEM
As a method of measuring / C, a cured product obtained by sufficiently dispersing particles to be observed in a room-temperature curable epoxy resin and then curing in an atmosphere at a temperature of 40 ° C. for 2 days is used as it is.
Alternatively, a method in which the sample is frozen and observed as a flaky sample using a microtome provided with diamond teeth is preferable.

The specific method for determining the ratio of the number of toners is as follows. D / C by TEM
To determine the toner, the equivalent circle diameter is determined from the cross-sectional area in a micrograph, and the value corresponding to the toner included in the range of ± 10% of the number average particle diameter determined by the method described below using a Coulter counter is applicable. Measure the minimum value (D) of the distance between the iron oxide particle surface and the toner particle surface for 100 corresponding toner particles, calculate the D / C, and calculate the ratio of particles having a D / C value of 0.02 or less. I do. The micrograph at this time is preferably at a magnification of 1 to 20,000 times in order to perform highly accurate measurement. In the present invention, for example, a transmission electron microscope (Hitachi H
-600 type) as an apparatus, observed at an acceleration voltage of 100 kV, and observed and measured using a micrograph with a magnification of 10,000 times.

A magnetic toner that satisfies the relationship of B / A <0.001 and satisfies the relationship of D / C ≦ 0.02 and has a toner count of 50% or more includes iron oxide localized on the toner surface, Conversely, instead of a magnetic toner that is extremely encapsulated and unevenly distributed inside the toner, the iron oxide is substantially uniformly dispersed in the magnetic toner while the iron oxide is Magnetic toner whose exposure is suppressed. When the dispersion state of the iron oxide is not uniform, it is difficult to satisfy the requirements of the present invention. Further, if a magnetic toner in which iron oxide is hardly exposed on the surface of the toner particles is used, even in an image forming method in which the magnetic toner is pressed against the surface of the electrostatic image carrier by a charging member, a transfer member, or the like, the electrostatic charge can be reduced. The surface of the image carrier is hardly abraded, and the abrasion of the electrostatic image carrier and the fusion of the toner can be significantly reduced over a long period of time.

The iron oxide used in the magnetic toner of the present invention is:
It is preferably used in an amount of 10 to 200 parts by mass, more preferably 20 to 180 parts by mass, based on 100 parts by mass of the binder resin component. If the amount of the iron oxide is less than 10 parts by mass, the coloring power of the magnetic toner is poor, and it is difficult to suppress fog.
If the amount exceeds 0 parts by mass, the coercive force due to the magnetic force on the toner carrier is increased and the developability is reduced, and not only is it difficult to uniformly disperse the iron oxide in the individual toner particles, but also the fixability is reduced. I will.

Next, the circularity of the toner, which is another feature of the present invention, will be described. In order to reduce the amount of toner attached to the non-image portion on the electrostatic image carrier and the amount of toner remaining after transfer, it is necessary that the chargeability of the toner particles is sufficient and uniform. Further, when a toner having a small particle diameter is used from the viewpoint of improving image quality, the adhesive force of the toner particles increases, so that the shape of the toner particles has a great effect on the toner adhesion to the non-image portion on the electrostatic image carrier. Effect. In other words, the closer the toner particles are spherical and the shape is uniform, the smaller the adhesion area of the particles, the smaller the amount of toner attached to the non-image area on the electrostatic image carrier and the amount of residual toner on the transfer, and high image quality and durability Stability is achieved. In addition, the toner particles according to the present invention have sufficient chargeability, and as described above, the adhesion of the toner particles is reduced, so that the toner particles can be transferred from the electrostatic image carrier to a transfer material such as paper. Transfer efficiency is also greatly improved. This can be said to be an important toner performance for achieving high resolution as well as reproducibility of a minute dot image.

Therefore, if such a magnetic toner is used, the amount of toner remaining after transfer is greatly reduced, so that the amount of toner present at the pressure contact portion between the charging member and the photosensitive member is extremely small.
Also in the image forming method having the contact charging step, it is considered that the scraping of the photoreceptor and the fusion of the toner are prevented, and the image defect is remarkably suppressed. Furthermore, the average circularity is 0.97
Since the toner of 0 or more has almost no edge on the surface,
Since the surface of the photoconductor is not scratched at the pressure contact portion between the charging member and the photoconductor, it is also possible to prevent the surface of the photoconductor from being scraped.

These effects become remarkable even in an image forming method including a contact transfer step in which a dropout during transfer is likely to occur. The magnetic toner of the present invention further improves the image quality, in order to faithfully develop finer latent image dots,
The weight average particle diameter of the magnetic toner is 3 to 10 μm, and further 4 to 8 μm
It is preferably less than. In the case of a magnetic toner having a weight average particle diameter of less than 3 μm, transfer residual toner on the photosensitive member increases due to a decrease in transfer efficiency, and it becomes difficult to maintain uniform charging. Furthermore, in addition to an increase in the surface area of the entire magnetic toner, the fluidity and agitation properties of the powder decrease, and it becomes difficult to uniformly charge the individual toner particles, so that fog and transferability tend to deteriorate. This is not preferable for the magnetic toner used in the present invention, since it tends to cause unevenness of the image. The toner has a weight average particle diameter of 10 μm.
If it exceeds m, scattering is likely to occur in characters and line images, and it is difficult to obtain high resolution. Further, as the resolution of the apparatus becomes higher, the reproduction of one dot tends to be deteriorated for the toner of 8 μm or more. In addition, the magnetic toner according to the present invention is a toner which is measured by a differential scanning calorimeter.
In the curve, 40-110 ° C., more preferably 45
It preferably has an endothermic peak at ~ 90 ° C.

Very fine images can be obtained by using a toner having a weight average particle diameter of 10 μm or less. However, when a toner having a small particle diameter is used, when a transfer material such as paper is used, the gap between paper fibers is reduced. , The heat from the heat fixing roller is insufficiently received, and low-temperature offset is likely to occur.

However, according to the DSC curve of the toner measured by the differential scanning calorimeter, when the temperature is raised, 40 to 110
When the toner is designed so as to have an endothermic peak in the range of ° C., it is possible to prevent abrasion of the photoreceptor while achieving both high resolution and offset resistance. More preferably, it has an endothermic peak in the range of 45 to 90 ° C. when the temperature is raised. If the endothermic peak of the magnetic toner is lower than 40 ° C., there may be a problem in storage stability and chargeability, and if the endothermic peak is higher than 110 ° C., it becomes difficult to prevent abrasion of the photoreceptor. There are cases.

In the DSC curve of the toner measured by the differential scanning calorimeter, the endothermic peak at the temperature rise was 40 to 110 ° C.
There are various methods for expressing in the range of
For example, it can be easily achieved by using a conventionally known wax component described below as a part of a raw material when producing a toner.

The magnetic toner of the present invention comprises a binder resin component 100
It is also one of the preferred usage forms to contain 0.5 to 50 parts by mass of a wax component based on parts by mass. If the content of the wax component is less than 0.5 part by mass, the low-temperature offset suppressing effect is poor, and if it exceeds 50 parts by mass, the long-term storage property is reduced, and the dispersibility of other toner materials is deteriorated,
This leads to deterioration of toner fluidity and deterioration of image characteristics.

Normally, a toner image is transferred onto a transfer material in a transfer step, and then this toner image is fixed on the transfer material by energy such as heat and pressure to obtain a semi-permanent image. As a fixing method at this time, a hot-roll fixing method is generally used, and as described above, a very high-definition image can be obtained by using a toner having a weight average particle diameter of 10 μm or less. When a transfer material such as paper is used, the toner particles having a small diameter enter gaps between fibers of the paper and receive insufficient heat from the heat fixing roller, so that low-temperature offset is likely to occur. However, by including an appropriate amount of a wax component as a release agent in the magnetic toner of the present invention, it is possible to prevent shaving of the photoconductor while achieving both high resolution and offset resistance.

Examples of the wax component usable in the toner of the present invention include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon waxes and their derivatives by Fischer-Tropsch method, Examples include polyolefin wax represented by polyethylene and its derivatives, natural wax such as carnauba wax and candelilla wax and its derivatives, and the like. The derivatives here include oxides, block copolymers with vinyl monomers, and graft-modified products. Furthermore, higher fatty alcohols, stearic acid, fatty acids such as palmitic acid or compounds thereof, acid amide wax,
Ester waxes, ketones, hydrogenated castor oil and derivatives thereof, vegetable waxes and animal waxes can also be used.

Among these wax components, the magnetic toner is represented by a DSC curve measured by a differential scanning calorimeter as follows:
In order to have an endothermic peak in the range of 40 to 110 ° C. when the temperature is raised, it is preferable to use a wax component having a maximum endothermic peak in that range, and use a wax component having a maximum endothermic peak in the range of 45 to 90 ° C. Is more preferred.
When the wax component has the maximum endothermic peak in the above temperature range, the releasability can be effectively exhibited while significantly contributing to low-temperature fixing. If the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the high-temperature offset resistance deteriorates. on the other hand,
If the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high, and low-temperature offset tends to occur, which is not preferable.
Further, when the toner is directly obtained by a polymerization method by performing granulation / polymerization in an aqueous medium, if the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation are not preferred.

The measurement of the endothermic peak temperature of the toner or the wax is performed according to “ASTM D 3418-8”. For the measurement,
For example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, an empty pan is set as a control, and the measurement is performed at a heating rate of 10 ° C./min. Further, the glass transition temperature (Tg) of the binder resin component and the like can be measured by the above-described measuring device.

The magnetic toner of the present invention has a magnetic field of 79.6 kA.
/ m (1000 Oersteds)
It is preferably 10 to 50 Am ² / kg (emu / g). By providing the magnetic force generating means in the developing device, the toner can be prevented from leaking with the magnetic toner, and not only can the toner transport property or stirring property be improved, but also the magnetic force can be applied so that the magnetic force acts on the toner carrier. By providing the generating means, it is easy to prevent the toner from scattering because the magnetic toner forms ears. However, the intensity of magnetization in a magnetic field 79.6 kA / m of the toner is less than 10Am ² / kg, the above effect is not obtained, and the action of magnetic force on the toner carrying member is ears of the toner becomes unstable In addition, image defects such as fogging, image density unevenness, and defective transfer of residual toner due to non-uniform charging of toner are likely to occur.

If the intensity of magnetization of the toner in a magnetic field of 79.6 kA / m is larger than 50 Am ² / kg, when a magnetic force is applied to the toner, the fluidity of the toner is remarkably reduced due to magnetic agglomeration. Fog and image stains are likely to occur.
Incidentally, the intensity of magnetization can be set in the above range by adjusting the content of the iron oxide used. Also,
By having a circularity of 0.970 or more like the toner of the present invention, the spikes of the toner on the toner carrier become thin and dense, so that the charging becomes uniform and the fog is greatly reduced. In the present invention, the magnetization strength of the magnetic toner is measured using a vibration magnetometer VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) at a room temperature of 25 ° C. and an external magnetic field of 79.6 kA / m. The magnetic properties of the above-described iron oxide are measured at a room temperature of 25 ° C. and an external magnetic field of 796 kA / m.

The magnetic toner of the present invention has a TH of magnetic toner.
In the molecular weight distribution measured by gel permeation chromatography (GPC) of the F-soluble matter,
The peak of the main peak is preferably in the range of 5,000 to 50,000, more preferably in the range of 8,000 to 40,000. When the peak top is less than 5000, when the toner particles are produced by polymerization, the viscosity increase of the droplets during polymerization is very small, and the hydrophobized iron oxide tends to be unevenly distributed near the surface of the toner particles. , (B / A) 0.001
In some cases, it may be difficult to set the value to less than. Further, a problem occurs in the storage stability of the toner, and the deterioration of the toner becomes remarkable when a large number of printouts are performed. Conversely, if the peak top exceeds 50,000, there is a problem in low-temperature fixability, and when toner particles are produced by polymerization, the dispersibility of the hydrophobically treated iron oxide due to a sharp increase in the viscosity of the droplets during polymerization. Tends to worsen. In addition, it becomes difficult to make the circularity 0.970 or more.

The main peak having a peak top in the molecular weight range of 5,000 to 50,000 preferably has X calculated by the following formula (1) of 1.4 or less, and particularly preferably has a peak top in the molecular weight range of 8,000 to 40,000. Main peak, and X is 1.1 or less.

[0098]

(Equation 4) The elution time (sec) for molecular weights of 10,000 and 100,000 means
This is a calculated elution time calculated by preparing a calibration curve using standard polystyrene described later and inputting 10,000 and 100,000 to the molecular weight term in the equation of the calibration curve.

In the pulverization method toner, a method in which a high molecular weight component effective for high-temperature offset resistance is produced by kneading a binder resin component containing an insoluble component (crosslinking component) has conventionally been adopted. However, as described above, the polymer produced by cutting the molecular chain by kneading naturally has a broad molecular weight distribution, does not contribute much to the high-temperature offset resistance, and has an intermediate molecular weight component that hinders the low-temperature fixability. In some cases, the toner is produced in a large amount or an excessively low molecular weight component is generated due to excessive cutting during kneading, which may cause a problem of fusion of the toner to a photosensitive member or a sleeve. In the case of a conventional polymerization method toner, it is possible to generate a THF-insoluble component by polymerizing a composition including a colorant, a monomer, and the like in the presence of a crosslinking agent. Unlike the suspension polymerization method, the molecular weight distribution of the binder resin component which is essentially generated is widened, and it is difficult to sharpen the molecular weight distribution of the component soluble in THF by the conventional technique.

The present inventors have conducted intensive studies on how to sharpen the molecular weight distribution of the THF-soluble component while producing an appropriate amount of the THF-insoluble component, and as a result, under specific polymerization conditions, By combining the raw materials of the above, an insoluble content effective for high-temperature offset resistance is generated, and the X is kept to 1.4 or less, and the peak top of the main peak is kept within a predetermined molecular weight range, whereby the high-temperature offset resistance is reduced. It has been found that, while maintaining the image quality, the low-temperature fixability is excellent, and the uniformity of charging is extremely good.

As long as the value of X falls within 1.4 or less, the effect of the present invention is not adversely affected even if the main peak is slightly tailed toward the high molecular weight side and the low molecular weight side.
The component having a molecular weight of 300,000 or more is less than 20 area%, more preferably less than 10 area%, and the component having a molecular weight of 2,000 to 5,000 is 15 area% with respect to the total area of the soluble component of the binder resin component in the molecular weight distribution measured. If it is less than 10%, more preferably the effect of the present invention will be further exhibited.

The production method preferably used to obtain the magnetic toner of the present invention will be described later. For example, in the case of the polymerization method, a highly surface-treated iron oxide, a wax component,
Easily by granulating a monomer composition containing a cross-linking agent, a chain transfer agent such as α-methylstyrene dimer in an aqueous medium, and performing suspension polymerization using an organic peroxide as a polymerization initiator. Obtainable.

The molecular weight of a component derived from a binder resin component soluble in THF by GPC may be measured as follows.

A solution obtained by dissolving the toner in THF at room temperature for 24 hours is filtered through a solvent-resistant membrane filter having a pore diameter of 0.2 μm to obtain a sample solution, which is measured under the following conditions. In the preparation of the sample, the amount of THF is adjusted so that the concentration of the component soluble in THF is 0.4 to 0.6% by mass.

Apparatus: High-speed GPC HLC8120 GPC (manufactured by Tosoh Corporation) Column: Shodex KF-801, 802, 803, 804, 805, 806,
7 stations of 807 (manufactured by Showa Denko KK) Eluent: THF Flow rate: 1.0 ml / min Oven temperature: 40.0 ° C Sample injection volume: 0.10 ml In calculating the molecular weight of the sample, use standard polystyrene resin (TSK Standard manufactured by Tosoh Corporation). Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20,
F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-50
Use the molecular weight calibration curve created in 0).

The magnetic toner of the present invention preferably contains a moderate amount of a THF-insoluble component (crosslinking component of the binder resin), and the amount thereof is determined by the molecular weight distribution of the THF-soluble component, particularly the ratio of the high-molecular component. Depends on how much is present, but usually 1 to 60% by mass based on the binder resin component,
Preferably it is in the range of 5 to 40% by mass. The measurement of the THF insoluble content is performed as follows.

The toner particles or 1 g of the toner is precisely weighed, charged into a cylindrical filter paper, and subjected to Soxhlet extraction with 200 ml of THF for 20 hours. Thereafter, the cylindrical filter paper is taken out, vacuum-dried at 40 ° C. for 20 hours, and the residue weight is measured to calculate.
At this time, since the toner contains components other than the binder resin component, such as iron oxide, a charge control agent, a wax component, and an external additive, the content of these components and whether they are soluble or insoluble in THF. In consideration of the above, the THF-insoluble content is calculated based on the binder resin component. TH component is a component of the toner other than the binder resin component.
F-soluble components (eg, THF-soluble wax, etc.)
Is used, the content of the component is separately calculated by analysis, and only how much of the binder resin component is T
Convert to whether it is insoluble in HF.

The binder resin component, which is a constituent material of the magnetic toner of the present invention, is preferably mainly composed of a styrene-based resin since the control of the molecular weight distribution is relatively easy. The styrene resin is obtained by polymerizing a monomer containing styrene using a polymerization initiator. That is,
It can be obtained by copolymerizing a styrene monomer and another polymerizable monomer.

The other polymerizable monomer that can be used is not particularly limited, but for example, o-methylstyrene,
Styrene monomers such as m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate Acrylates such as n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate N-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethyl methacrylate Methacrylic acid esters such as aminoethyl; other acrylonitrile, methacrylonitrile, and the like monomers acrylamide. These resins may be used alone or in general as resins having a theoretical glass transition temperature (Tg) of 40 to 70 ° C. as described in the published Polymer Handbook, 2nd edition, III-p139 to 192 (manufactured by John Wiley & Sons). The monomers are used by appropriately mixing. When the theoretical glass transition temperature is lower than 40 ° C., problems tend to occur in terms of storage stability and durability stability of the toner. On the other hand, when the glass transition temperature exceeds 70 ° C., problems may occur in toner fixability.

The polymerization initiator used in the present invention includes:
There are conventionally known azo-based polymerization initiators, organic peroxide-based polymerization initiators, and the like. As the azo-based polymerization initiator, 2,2′-
Azobis- (2,4-dimethylvaleronitrile), 2,
2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-
Examples include azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, and the like. Examples of the organic peroxide-based polymerization initiator include t-butylperoxyacetate, t-butylperoxylaurate, t-butyl peroxypivalate, t-butyl peroxy-2-
Ethyl hexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy neodecanoate, t-
Hexyl peroxy acetate, t-hexyl peroxy laurate, t-hexyl peroxy pivalate, t
-Hexylperoxy-2-ethylhexanoate, t
-Hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylperoxybenzoate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1,1,3,3-
Tetramethylbutyl peroxy neodecanoate, 1-
Cyclohexyl-1-methylethylperoxy neodecanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexa Noate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (Benzoylperoxy) hexane, t-butylperoxy-m-toluoylbenzoate, bis (t-butylperoxy) isophthalate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5 -Trimethylhexanoate, 2, - dimethyl-2,5-bis (m-
Peroxyesters such as toluoylperoxy) hexane; diacyl peroxides such as benzoyl peroxide, lauroyl peroxide and isobutyryl peroxide; diisopropylperoxydicarbonate; bis (4-t-butylcyclohexyl) peroxydicarbonate Peroxydicarbonate,
1,1-di-t-butylperoxycyclohexane,
1,1-di-t-hexylperoxycyclohexane,
Peroxyketals such as 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and 2,2-di-t-butylperoxybutane; di-t-butyl peroxide, dicumylper Dialkyl peroxides such as oxide and t-butylcumyl peroxide; and other examples include t-butylperoxyallyl monocarbonate. If necessary, two or more of these initiators can be used.

Among the above-mentioned polymerization initiators, particularly, organic peroxide-based polymerization initiators cause a hydrogen abstraction (crosslinking) reaction together with the polymerization reaction.
In addition, the toner of the present invention is easily used because it has a strong tendency to reduce the intermediate molecular weight component and is preferably used. In addition, among these organic peroxide-based polymerization initiators, peroxyester, peroxydicarbonate, and diacyl peroxide are preferably used, and when a diacyl peroxide is used, the main peak of a THF-soluble component is particularly increased. Sharpness is preferable because uniform chargeability is further improved.

The polymerization initiator used in the present invention is a monomer
It is preferable to use 0.2 to 20 parts by mass with respect to 100 parts by mass, and when the polymerization reaction is performed with the added amount, the molecular weight is 5,000 to 5,000.
A polymer having a main peak between 0 is obtained, and the desired strength and appropriate melting characteristics can be imparted to the toner.

When an organic peroxide-based polymerization initiator is used in the present invention, its theoretical active oxygen content is 3.0 to 12.0%.
If it is less than 3.0%, a large amount of the polymerization initiator tends to be used, which is economically disadvantageous.If it exceeds 12.0%, it is difficult to handle and control the polymerization reaction. May be.

In the present invention, in order to control the amount of THF-insoluble matter and sharpen the main peak of the binder resin component soluble in THF, a conventionally known chain transfer agent is added to the monomer composition to carry out radical polymerization. Is preferably performed.

Examples of the chain transfer agent which can be used in this case include α-methylstyrene dimer, t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, carbon tetrachloride, carbon tetrabromide and the like. . Of these, chain transfer agents more preferably used are α-methylstyrene dimer, t-dodecyl mercaptan and n-dodecyl mercaptan. α-methylstyrene dimer can make the value of X smaller than thiols such as t-dodecyl mercaptan, and is particularly preferably used. These chain transfer agents can be added before the start of the polymerization or during the polymerization. These chain transfer agents are used in a proportion of generally 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the monomer.

In producing the polymerized toner according to the present invention, a crosslinking agent is added to the monomer composition to control the molecular weight distribution of the binder resin component soluble in THF and to adjust the content of the THF-insoluble component. It is preferably added, and the preferable addition amount is 0.001 to 15% by mass based on the monomer.

The crosslinking agent is not particularly limited as long as it is a compound having two or more polymerizable double bonds in one molecule. Examples thereof include divinylbenzene, divinylnaphthalene, ethylene glycol diacrylate, and ethylene glycol diacrylate. Methacrylate, 1,3-butanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
Pentaerythritol tetraacrylate, diallyl ether, pentaerythritol triacrylate, triallyl ether, divinylaniline, divinylether, divinylsulfide, divinylsulfone, etc. And a cross-linkable polymer such as a butadiene copolymer, which may be used alone or as a mixture.

The toner of the present invention can be produced by a pulverization method. However, in the pulverization method, mechanical, thermal, or some special treatment is performed to make the average circularity of the toner 0.970 or more. Since it is necessary, it is preferable to produce by a suspension polymerization method. Even when a toner is manufactured by suspension polymerization using a normal magnetic material, the magnetic material is unevenly distributed on the toner surface due to poor dispersibility, or the magnetic material is disordered during granulation in an aqueous medium. The toner particles having an average circularity of 0.970 or more were difficult to obtain because of the movement of the particles and the particle shape being distorted by being dragged by it, but the iron oxide used in the present invention is,
Since uniform hydrophobicity is performed at a high level, a toner having an average circularity of 0.970 or more can be easily obtained.

In the present invention, a resin may be added to the monomer composition for polymerization. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups, which cannot be used because monomers dissolve in aqueous suspensions and cause emulsion polymerization due to water solubility. When it is desired to introduce the contained monomer components into the toner, they are formed into a random copolymer, a block copolymer, or a copolymer such as a graft copolymer of these and a vinyl compound such as styrene or ethylene, Alternatively, it can be used in the form of a polycondensate such as polyester and polyamide, and a polyaddition polymer such as polyether and polyimine.

When such a high molecular polymer containing a polar functional group is coexisted in the toner, the above-mentioned wax component is phase-separated, the encapsulation becomes stronger, and the offset resistance, blocking resistance, and low-temperature fixability are excellent. Toner can be obtained. The amount of the resin used, the polymerizable monomer 100
1 to 20 parts by mass relative to parts by mass is preferred. If the amount used is less than 1 part by mass, the effect of addition is small, while if it exceeds 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner. The average molecular weight of the high molecular polymer containing these polar functional groups is preferably 3000 or more. If the molecular weight is less than 3,000, particularly 2,000 or less, the present polymer tends to concentrate near the surface, so that adverse effects on developability, anti-blocking properties and the like are likely to occur, which is not preferable. Further, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. it can.

The toner of the present invention may contain a charge control agent for stabilizing the charge characteristics. As the charge control agent, a known charge control agent can be used, but a charge control agent having a high charging speed and capable of stably maintaining a constant charge amount is particularly preferable. Further, when the toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially having no soluble matter in an aqueous dispersion medium is particularly preferable.
As specific compounds, salicylic acid, alkyl salicylic acid, dialkyl salicylic acid as a negative charge control agent,
Naphthoic acid, a metal compound of an aromatic carboxylic acid such as dicarboxylic acid, a metal salt or a metal complex of an azo dye or an azo pigment, a polymer compound having a sulfonic acid or carboxylic acid group in a side chain, a boron compound, a urea compound, Silicon compounds, calixarenes and the like can be mentioned. Quaternary ammonium salt as a positive charge control agent, a high molecular compound having the quaternary ammonium salt in the side chain, a guanidine compound,
Nigrosine compounds, imidazole compounds, and the like.

These charge control agents include the polymerizable monomer 100
It is preferable to use 0.5 to 10 parts by mass with respect to parts by mass. However, in the magnetic toner of the present invention, the addition of a charge control agent is not essential, and the charge control agent is not necessarily contained in the toner by positively utilizing frictional charging between the layer pressure regulating member of the magnetic toner and the toner carrier. It does not need to be included.

Further, other coloring agents may be used in addition to iron oxide. Coloring materials that can be used in combination include magnetic or non-magnetic inorganic compounds, known dyes and pigments. Specifically, for example, cobalt, ferromagnetic metal particles such as nickel, or chromium, manganese, copper,
Zinc, aluminum, alloys with rare earth elements, hematite, titanium black, nigrosine dye / pigment, carbon black, phthalocyanine. These may also be used after the surface is hydrophobized similarly to iron oxide.

In the production of a magnetic toner by the suspension polymerization method,
In general, the above-mentioned toner composition, i.e., components necessary as toners such as iron oxide, a colorant, a release agent, a plasticizer, a binder resin, a charge control agent, a crosslinking agent, and a chain transfer agent in a polymerizable monomer, Other additives, for example, an organic solvent to be added to reduce the viscosity of the polymer formed in the polymerization reaction, a dispersant and the like are appropriately added, and the mixture is homogenized uniformly with a disperser such as a homogenizer, a ball mill, a colloid mill, and an ultrasonic disperser. The dissolved or dispersed monomer composition is suspended in an aqueous medium containing a dispersion stabilizer.

At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to make the desired toner particle size at once. As for the timing of the addition of the polymerization initiator, it may be added at the same time as the other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Immediately after granulation and before the initiation of the polymerization reaction, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added.

After the granulation, stirring may be carried out using a conventional stirrer to such an extent that the particle state is maintained and the toner particles are prevented from floating and settling.

In the suspension polymerization method of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. Among them, the inorganic dispersants hardly produce ultrafine powder which causes image defects. Since the dispersion stability is obtained due to steric hindrance, the stability is hardly lost even if the reaction temperature is changed, the washing is easy, and the toner is hardly adversely affected. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; calcium metasilicate, calcium sulfate and barium sulfate. Inorganic salts; inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and alumina. These inorganic dispersants, based on 100 parts by weight of the polymerizable monomer, 0.2 to 20
It is preferable to use parts by mass alone or in combination of two or more. When a toner having a finer particle size is desired, for example, when a toner having a weight average particle diameter of 5 μm or less is used, a surfactant of 0.001 to 0.1 parts by mass may be used in combination.

Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,
Examples include sodium oleate, sodium laurate, sodium stearate, and potassium stearate.

When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be formed in an aqueous medium. For example, in the case of calcium phosphate, a water-insoluble calcium phosphate can be produced by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring, whereby more uniform and fine dispersion can be achieved. At this time, a water-soluble sodium chloride salt is simultaneously produced as a by-product, but if the water-soluble salt is present in the aqueous medium, the dissolution of the polymerizable monomer in water is suppressed, and the ultrafine toner due to emulsion polymerization is formed. This is more convenient because it hardly occurs. Since it becomes an obstacle when removing the residual polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or to desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

In the polymerization step, the polymerization temperature is 40 ° C.
As described above, the polymerization is generally carried out at a temperature of 50 to 90 ° C. When the polymerization is carried out in this temperature range, the wax component or the like to be sealed inside is precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, it is possible to raise the reaction temperature to 90 to 150 ° C. at the end of the polymerization reaction.

The toner of the present invention has an inorganic fine powder on the surface of the toner particles. The presence of the inorganic fine powder on the surface of the toner particles of the present invention not only improves the fluidity of the toner, but also makes the chargeability more stable. Examples of the inorganic fine powder include silica fine powder, titanium oxide fine powder, alumina fine powder and the like, and composite oxides thereof. These may be subjected to hydrophobic treatment as necessary. Among these, it is preferable to use silica fine powder, especially silica fine powder that has been subjected to hydrophobic treatment.

The inorganic fine powder used in the magnetic toner of the present invention has a number-average particle diameter of 4 to 80 nm and a specific surface area of 30 m ² / g or more by nitrogen adsorption as measured by the BET method, especially 50
Those having a range of 400400 m ² / g are preferable because good results can be obtained. The measurement of the specific surface area is performed in the same manner as for iron oxide.

In the present invention, the method of measuring the number primary average particle diameter of the inorganic fine powder is based on a photograph of the toner enlarged and taken by a scanning electron microscope, and further by an elemental analysis means such as XMA attached to the scanning electron microscope. While comparing the toner photograph mapped with the element contained in the inorganic fine powder, 100 or more primary particles of the inorganic fine powder attached or separated on the toner surface were measured, and the number primary average particle diameter was measured. Can be requested.

The fine silica powder used in the present invention includes both a so-called dry method produced by vapor phase oxidation of a silicon halide and a so-called fumed silica and a so-called wet silica produced from water glass. Although usable, dry silica having few silanol groups on the surface and inside and having no production residue is preferably used. Further, the silica fine powder used in the present invention is preferably subjected to a hydrophobic treatment.

Examples of the silane coupling agent used in the hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyl. Dichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane,
Chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldi Examples include siloxane, 1,3-diphenyltetramethyldisiloxane, and the like. Examples of the organosilicon compound include silicone oil.

The preferred silicone oil is 25 ° C.
The viscosity is about 30 to 1,000 mm ² / s (cSt). For example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil are preferable.

The silicone oil treatment may be carried out by, for example, directly mixing the silica fine powder treated with the silane coupling agent with the silicone oil using a mixer such as a Henschel mixer, or adding the silicone oil to the base silica. A method of injecting oil may be used. Alternatively, it may be prepared by dissolving or dispersing silicone oil in an appropriate solvent, mixing with a base silica fine powder, and removing the solvent.

An external additive other than the fluidity improver may be added to the magnetic toner of the present invention, if necessary.

For example, fine particles having a primary particle size of more than 30 nm (preferably having a BET specific surface area of less than 50 m ² / g), more preferably a primary particle size of 50 nm or more (preferably a BET (Specific surface area is less than 30m ² / g)
It is also a preferred embodiment to further add inorganic fine particles or organic fine particles which are nearly spherical. For example, spherical silica particles, spherical polymethylsilsesquioxane particles,
It is preferable to use spherical resin particles.

Further additives such as lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder; abrasives such as cerium oxide powder, silicon carbide powder, strontium titanate powder; anti-caking Agents; conductivity-imparting agents such as carbon black powder, zinc oxide powder, and tin oxide powder; and small amounts of reverse polarity organic fine particles, inorganic fine particles, and a developing property improver. These additives are also preferably used after the surface thereof is subjected to a hydrophobic treatment.

The above additives are preferably used in an amount of 0.1 to 5 parts by mass (preferably 0.1 to 3 parts by mass) based on 100 parts by mass of the magnetic toner.

In the case of producing the toner of the present invention by a pulverization method, a known method can be used. As a known method, for example, a binder resin described below, the above-described iron oxide, a wax component, a charge control agent, a component necessary as a toner such as a colorant and other additives in some cases, such as a Henschel mixer, a ball mill, etc. After sufficient mixing in a mixer, the mixture is melted and kneaded using a heat kneader such as a heating roll, kneader, extruder, and other toner materials such as iron oxide are mixed while the resins are mutually compatible. After dispersion or dissolution, solidification by cooling, and pulverization, classification, surface treatment is performed as necessary to obtain toner particles, and magnetic toner can be obtained by adding and mixing inorganic fine powders and the like as necessary. . Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-segment classifier from the viewpoint of production efficiency. The pulverizing step can be performed using a known pulverizing device such as a mechanical impact type or a jet type.
In order to obtain a magnetic toner having a specific degree of circularity according to the present invention, it is preferable to further apply heat to pulverize or to perform auxiliary mechanical impact. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method in which the toner particles pass through a hot air flow, or the like may be used.

As a method for applying a mechanical impact force, there is a method using a mechanical impact type pulverizer such as a Kryptron system manufactured by Kawasaki Heavy Industries and a turbo mill manufactured by Turbo Industries. Also, as in devices such as Hosokawa Micron's Mechano-Fusion System and Nara Machinery's Hybridization System, the toner is pressed against the inside of the casing by centrifugal force with the blades rotating at high speed, and the force such as compressive force and frictional force is applied. A method of applying a mechanical impact force to the toner may be used.

When performing a process of applying a mechanical shock,
It is preferable to set the ambient temperature during the process to a temperature near the glass transition point Tg of the toner (that is, a temperature in the range of ± 30 ° C. of the glass transition point Tg) from the viewpoint of prevention of aggregation and productivity. More preferably, the glass transition point Tg of the toner is ±
Performing the treatment at a temperature in the range of 20 ° C. is particularly effective for improving the transfer efficiency.

Further, the toner of the present invention is disclosed in
No. 13945, a method of atomizing a molten mixture into the air using a disk or a multi-fluid nozzle to obtain a spherical toner, or a method of dissolving a monomer into an aqueous organic solvent in which a polymer obtained is insoluble. The toner is manufactured using a dispersion polymerization method of directly producing a toner using an emulsion polymerization method represented by a soap-free polymerization method of producing a toner by directly polymerizing in the presence of a water-soluble polar polymerization initiator. It can also be manufactured by a method.

When the toner of the present invention is produced by a pulverizing method, the binder resin may be, for example, a homopolymer of styrene such as polystyrene and polyvinyltoluene and a substituted product thereof; a styrene-propylene copolymer and a styrene-vinyltoluene copolymer. Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer,
Styrene-vinyl ethyl ether copolymer, styrene-
Styrene-based copolymers such as vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, poly Butyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic resin, rosin, modified rosin,
Tempel resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax,
Carnauba wax or the like can be used alone or in combination.
In particular, styrene-based copolymers and polyester resins are preferred in terms of development characteristics, fixability, and the like. <2> Image Forming Method Using Magnetic Toner of the Present Invention The image forming method of the present invention includes a charging step, an electrostatic latent image forming step, a developing step, and a transferring step. It was used.

Hereinafter, embodiments of the image forming method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. In FIG. 1, a charging roller 11 as a contact charging member is provided around a photosensitive drum 100 as an image carrier.
7. Developing device 140 as developing means, transfer roller 114 as transfer means, cleaner 116, register roller 124
Etc. are provided. Then, the photosensitive drum 100 is charged to -700 V by the charging roller 117. (Applied voltage is AC voltage -2.0 kVpp (Vpp: peak-to-peak potential), DC voltage -700 Vdc). Then, the photosensitive drum 100 is exposed by irradiating the laser beam 123 to the photosensitive drum 100 by the laser generator 121. The electrostatic latent image on the photosensitive drum 100 is developed with a one-component magnetic toner by a developing device 140, and is transferred onto a transfer material by a transfer roller 114 in contact with the photosensitive drum via the transfer material. Transfer material P with toner image
Is conveyed to a fixing device 126 by a conveyor belt 125 or the like and is fixed on the transfer material P. Further, a part of the toner left on the photosensitive drum is removed by a cleaner 116 as a cleaning means.
Cleaning. As shown in FIG. 2, the developing device 140 is made of aluminum,
A cylindrical toner carrier 102 (hereinafter, also referred to as a “developing sleeve”) made of a non-magnetic metal such as stainless steel is provided. A gap between the photosensitive drum 100 and the developing sleeve 102 is a sleeve / photoconductor gap (not shown). It is maintained at about 300 μm by a holding member or the like. This gap can be changed if necessary. In the developing sleeve 102, a magnet roller 104 is fixed and disposed concentrically with the developing sleeve 102. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure. S1 is development, N1 is toner coating amount regulation, S2 is toner take-in / transport,
No. 2 influences the prevention of toner blowing.

The toner is applied to the developing sleeve 102,
Adhered and transported. An elastic blade 103 is provided as a toner layer thickness regulating member that regulates the amount of magnetic toner conveyed, and the amount of toner conveyed to the developing area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. In the developing area, a developing bias of a DC voltage and an AC voltage is applied between the photosensitive drum 100 and the developing sleeve 102, and the toner on the developing sleeve 102 flies on the photosensitive drum 100 in accordance with the electrostatic latent image to form a visible image. Becomes

As an example of a developing method using the toner of the present invention, a system in which the toner carrier and the electrostatic image carrier are not in contact will be described.

In the non-contact developing method, the magnetic toner is applied onto the toner carrier at a thickness smaller than the closest distance (S-D) between the toner carrier and the photosensitive member (electrostatic image carrier). Then, development is performed by applying an alternating electric field. That is, the thickness of the toner layer on the toner carrier is set smaller than the closest gap between the photoconductor and the toner carrier by the layer thickness regulating member that regulates the magnetic toner on the toner carrier. At this time, it is particularly preferable that the layer thickness regulating member that regulates the magnetic toner on the toner carrier is an elastic member and is in contact with the toner carrier via the toner from the viewpoint of uniformly charging the magnetic toner.

Further, the toner carrier is 100
It is preferable that they are installed facing each other with a separation distance of 10001000 μm, and more preferable that they are installed facing each other with a separation distance of 120 to 500 μm. If the separation distance of the toner carrier from the photoconductor is smaller than 100 μm, the change in the development characteristics of the toner with respect to the fluctuation of the separation distance becomes large, so that it is difficult to mass-produce an image forming apparatus satisfying stable image quality. . If the separation distance of the toner carrier from the photoconductor is greater than 1000 μm, the recoverability of the transfer residual toner to the developing device is reduced, and fog due to poor recovery is likely to occur. Further, the ability of the toner to follow the latent image on the photoreceptor is reduced, which tends to cause a reduction in image quality such as a reduction in resolution and a reduction in image density.

In the present invention, 5 to 5
It is preferable that the layers are laminated so as to form a toner layer of 0 g / m ² . If the amount of the toner on the toner carrier is less than 5 g / m ^2, it is difficult to obtain a sufficient image density, and the toner layer becomes uneven due to excessive charging of the toner. If the amount of toner on the toner carrier is more than 50 g / m ² , toner scattering is likely to occur.

The surface roughness Ra (JIS center line average roughness) of the toner carrier used in the present invention is 0.2 to 3.5 μm.
It is preferably in the range of m. When Ra is less than 0.2 μm, the charge amount on the toner carrier increases, and the developability tends to be insufficient. On the other hand, when Ra exceeds 3.5 μm, unevenness in the lamination of the toner on the toner carrier is likely to occur, and the density tends to be uneven on the image. The surface roughness Ra is more preferably in the range of 0.5 to 3.0 μm.

In the present invention, the surface roughness Ra of the toner carrier is measured by a surface roughness measuring device (Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.) based on JIS surface roughness “JIS B 0601”. It corresponds to the center line average roughness measured by using. Specifically, a 2.5 mm portion as the measurement length a is extracted from the roughness curve in the direction of its center line, the center line of the extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is y. = F (x) is a value obtained by the following equation (3) in micrometers (μm).

[0155]

(Equation 5) As the toner carrier having a surface roughness (Ra) in the above range, a conductive cylinder formed of a metal or alloy such as aluminum or stainless steel is preferably used. The conductive cylinder may be formed of a resin composition having sufficient mechanical strength and conductivity, or a conductive rubber roller may be used. Further, the present invention is not limited to the cylindrical shape as described above, and may be in the form of an endless belt that is driven to rotate. Further, a resin layer may be used as a coating layer for these.

The surface roughness (Ra) of the toner carrier in the present invention can be set in the above range by, for example, changing the polishing state of the surface layer of the toner carrier. That is, if the surface of the toner carrier is polished roughly, the surface roughness can be increased, and if the surface is polished finely, the surface roughness can be reduced. In the case where a resin layer is used, conductive fine particles described later are added to the resin layer, and the surface roughness can be adjusted also by the particle size and the amount added.

Further, since the magnetic toner according to the present invention has a high charging ability, it is preferable to control the total charge amount of the toner during development. The surface of the toner carrier according to the present invention is preferably coated with a resin layer in which conductive fine particles and / or a lubricant are dispersed.

As the conductive fine particles contained in the resin layer covering the surface of the toner carrier, conductive metal oxides such as carbon black, graphite, and conductive zinc oxide and metal double oxides may be used alone or in combination of two or more. It is preferable to use them in combination. Examples of the resin in which the conductive fine particles and / or the lubricant are dispersed include a phenol resin, an epoxy resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyolefin resin, a silicone resin, a fluorine resin, and a styrene resin. Known resins such as resins and acrylic resins are used. Particularly, a thermosetting resin or a photocurable resin is preferable.

In the non-contact developing method, it is preferable that the moving speed of the toner carrier that carries the toner in the developing step and conveys it to the developing unit has a speed difference from the moving speed of the photoconductor. By providing such a speed difference, toner particles can be sufficiently supplied from the toner carrying member side to the photosensitive member side, and a good image can be obtained.

In the present invention, the surface of the toner carrier for carrying the toner may move in the same direction as the moving direction of the surface of the image carrier, or may move in the opposite direction. When the moving directions are the same, it is desirable that the ratio is 70% or more with respect to the moving speed of the image carrier.
If it is less than 70%, the image quality may be poor. The higher the moving speed ratio, the larger the amount of toner supplied to the developing site, the more frequently toner is attached to and detached from the latent image, and unnecessary portions are scraped off and added to necessary portions repeatedly. As a result, an image faithful to the latent image can be obtained. Specifically, the moving speed of the surface of the toner carrier is preferably 0.7 to 7.0 times the moving speed of the surface of the image carrier.

In the developing section, an AC electric field is applied to transfer the magnetic toner to an electrostatic latent image and develop the image. The AC electric field at this time has a peak-to-peak electric field strength of at least 3 ×. 10 ⁶ -1 × 10 ⁷ V / m, frequency 100
Preferably it is 50005000 Hz. It is also a preferable embodiment to further superimpose a DC bias.

Next, the charging step will be described. In the present invention, a non-contact charging step such as a charging step using a charging device using corona discharge may be used, but a contact charging method in which a charging member is brought into contact with a photoreceptor is a preferable charging method. In this case, it is preferable to use a charging roller as the contact charging member. As a preferable process condition when the charging roller as shown in FIG. 1 is used, the contact pressure of the roller member is 4.9 to 490 N / m (5 to 500 g / cm), and the DC voltage or the AC voltage is superimposed on the DC voltage. Is used.
When an AC voltage is superimposed on a DC voltage, the AC voltage is preferably 0.5 to 5 kVpp, the AC frequency is 50 to 5 kHz, and the DC voltage is ± 0.2 to ± 5 kV.

Other charging means include a method using a charging blade and a method using a conductive brush. Also when these contact charging means are used, there is an effect that a high voltage becomes unnecessary and generation of ozone is reduced.

[0164] The material of the charging roller and the charging blade as the contact charging member is preferably conductive rubber, and a release coating may be provided on the surface thereof. As the release coating, a nylon resin, PVdF (polyvinylidene fluoride), PVdC (polyvinylidene chloride), or a fluoroacrylic resin can be used.

The hardness of the roller member used as the contact charging member is preferably such that Asker C hardness is 50 degrees or less. If the hardness is too low, the shape is not stable, so that the contact property with the member to be charged is deteriorated, and stable charging property cannot be obtained.
On the other hand, if the hardness is too high, not only is it impossible to secure a charging contact portion with the member to be charged, but also the microscopic contact with the surface of the member to be charged deteriorates. Furthermore, by providing a relative speed difference between the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier, a higher contact can be achieved at the contact portion between the contact charging member and the image carrier. You can get sex.

It is preferable that the contact charging member and the image carrier are moved in opposite directions at the contact portion. For example, it is desirable that the contact charging member be driven to rotate, and that the rotation direction of the contact charging member be rotated in a direction opposite to the moving direction of the surface of the image carrier at the contact portion.

It is possible to move the charging member in the same direction as the moving direction of the surface of the image carrier to give a speed difference. However, the contact charging property depends on the ratio of the peripheral speed of the image carrier to the peripheral speed of the charging member. In order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging member in the forward direction is larger than that in the reverse direction, so that moving the charging member in the reverse direction is advantageous in terms of the rotation speed. It is. The peripheral speed ratio described here can be expressed by the following equation (4).

[0168]

## EQU6 ## Peripheral speed ratio (%) = (peripheral speed of charging member / peripheral speed of image carrier) × 100 (4) It is possible to obtain good charging properties only by applying a DC bias to the charging bias applied to the contact charging member. However, an AC voltage (alternating voltage) may be superimposed on a DC voltage as in the device shown in FIG.

The AC voltage at this time is 2 × Vth (Vt
h: It is preferable to have a peak voltage less than (discharge start voltage when DC voltage is applied) (V).

If the peak voltage of the AC voltage applied to the DC voltage is not less than 2 × Vth, the potential on the image carrier may become unstable, which is not preferable. As an AC voltage when applying a bias in which an AC voltage is superimposed on a DC voltage, the AC voltage more preferably has a peak voltage less than Vth. Thereby, the image carrier can be charged without a substantial discharge phenomenon. Next, the transfer step will be described.

In the present invention, a non-contact transfer step such as a transfer step using a transfer device using corona discharge may be used, but preferably, the transfer member is in contact with the photosensitive member via the transfer material. This is a contact transfer method in which transfer is performed by the transfer member.

The contact pressure of the transfer member was a linear pressure of 2.9 N / m.
(3 g / cm) or more, more preferably 1 g / cm or more.
It is 9.6N / m (20g / cm) or more. Linear pressure as contact pressure
If it is less than 2.9 N / m (3 g / cm), the transfer of the transfer material and the occurrence of poor transfer tend to occur, which is not preferable.

As a transfer member in the contact transfer step, an apparatus having a transfer roller or a transfer belt is used. As an example of the transfer roller, at least a core metal and a conductive elastic layer, and the conductive elastic layer has a volume resistance of 10 such as urethane or EPDM in which a conductive material such as carbon is dispersed.
It is made of an elastic material of about ⁶ to 10 ¹⁰ Ωcm, and a transfer bias is applied by a transfer bias power supply.

Next, the photosensitive member used in the present invention will be described below.

As the photosensitive member, a-Se, CdS, Zn
A photosensitive drum or a photosensitive belt having a photoconductive insulating material layer such as O ₂ , OPC (organic photoreceptor) and a-Si is preferably used. In particular, in the present invention, it is preferable to use a photoconductor whose surface is mainly composed of a polymer binder. For example, when a protective film (protective layer) mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or as a charge transport layer of a functionally separated organic photoreceptor, a surface formed of a charge transport material and a resin. There is a case where a layer is provided, and a case where a protective layer mainly composed of a resin is provided on the surface layer. It is preferable that these surface layers (or protective layers) have releasability. As means for actually providing releasability, a resin having a low surface energy is used for the resin itself constituting the film, Add additives that impart water and lipophilicity, disperse materials with high release properties into powder,
And the like. Examples include introducing a functional group such as a fluorine-containing group and a silicone-containing group into the structure of the structural unit of the resin. Examples of additives that impart water repellency and lipophilicity include surfactants. Materials with high mold release properties include
Compounds containing a fluorine atom, that is, polytetrafluoroethylene, polyvinylidene fluoride, and carbon fluoride are exemplified.

By these means, the contact angle of the surface of the photoreceptor with water can be 85 degrees or more, and the transferability of the toner and the durability of the photoreceptor can be further improved. The contact angle of the photoreceptor surface to water is preferably 90 degrees or more. In the present invention, among the above means (1) and (2), it is preferable to disperse the releasable powder such as a fluorine-containing resin in the outermost surface layer as described above. It is particularly preferred to use ethylene.

In order to incorporate these releasable powders on the surface, a layer in which the releasable powder is dispersed in a binder resin is provided on the outermost surface of the photoreceptor, or the photoreceptor itself is coated with the resin. As long as the organic photoreceptor is mainly configured, a release powder may be dispersed in the uppermost layer without providing a new surface layer. The addition amount of the release powder is preferably 1 to 60% by mass, more preferably 2 to 50% by mass, based on the total amount of the surface layer. If the amount of the releasable powder is less than 1% by mass, the effect of improving the transferability of the toner and the durability of the photoreceptor is insufficient. If the amount exceeds 60% by mass, the strength of the protective film is reduced, This is not preferable because the amount of light incident on the body is significantly reduced.

The contact angle was measured using a drop-type contact angle meter (for example, contact angle meter CA-X of Kyowa Interface Science Co., Ltd.) at the place where the free surface of water was in contact with the photoreceptor. And the angle formed by the photoreceptor surface (the angle inside the liquid).

The above measurement is performed at room temperature (about 21 to 25 ° C.). In the present invention, a contact charging method in which the charging means contacts the charging member to the photoreceptor is a preferable charging method. Therefore, providing a protective layer (protective film) on the surface of the photoreceptor has a remarkable effect of improving the durability, and is one of the preferred embodiments.

In the present invention, a contact charging method,
Since it is preferable to apply the contact transfer method, the diameter is 50
A photoreceptor having a small diameter of less than mm is particularly effectively used. That is, when the diameter of the photoreceptor used for image formation is small, the curvature for the same linear pressure is large, and the pressure is likely to be concentrated at the contact portion. Although it is considered that the same phenomenon occurs in the belt photoconductor, the present invention is also effective for an image forming apparatus in which the radius of curvature at the transfer section is 25 mm or less.

One preferred embodiment of the photoreceptor used in the present invention will be described below. Specifically, a laminated photosensitive layer having a structure in which a charge generation layer and a charge transport layer are laminated on a conductive substrate in this order is one of preferred examples.

Examples of the conductive substrate include metals such as aluminum and stainless steel, aluminum alloys, plastics having a coating layer of indium oxide-tin oxide alloy, paper impregnated with conductive particles, plastics, and plastics having a conductive polymer. Are used. On these conductive substrates, the photosensitive layer has improved adhesion, improved coating properties, protection of the substrate, covering of defects on the substrate, improved charge injection from the substrate, and protection against electrical breakdown of the photosensitive layer. An undercoat layer may be provided for the purpose.

The undercoat layer may be made of polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, It is formed of a material such as gelatin, polyurethane, and aluminum oxide. The thickness of the undercoat layer is usually 0.1 to 10 μm, preferably about 0.1 to 3 μm.

The charge generation layer is made of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a polycyclic quinone pigment, a squarylium dye, a pyrylium salt, a thiopyrylium salt, a triphenylmethane dye, selenium,
A charge generating substance such as an inorganic substance such as amorphous silicon is dispersed in a suitable binder resin and coated or formed by vapor deposition. As the binder resin, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin,
Examples include polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicone resin, epoxy resin, and vinyl acetate resin, and a binder resin can be arbitrarily selected from such a wide range of resins. The amount of the binder resin contained in the charge generation layer is preferably 80% by mass or less, more preferably 0 to 60% by mass, based on the whole charge generation layer. The thickness of the charge generation layer is preferably 5 μm or less, and particularly preferably 0.05 to 2 μm.

The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transporting layer is formed by dissolving a charge transporting substance in a solvent together with a binder resin if necessary, and applying the solution. The thickness of the charge generation layer is generally 5 to 40 μm. As the charge transport substance, biphenylene, anthracene, pyrene, a polycyclic aromatic compound having a structure such as phenanthrene in the main chain or a side chain, indole, carbazole, oxadiazole, nitrogen-containing cyclic compound such as pyrazoline, hydrazone compound, Examples include styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

As the binder resin for dispersing these charge transporting substances, polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin,
Examples include resins such as acrylic resins and polyamide resins, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

Further, a protective layer may be further provided as a surface layer. As the resin of the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent of these resins alone or
It can be used in combination of more than one kind.

In addition, conductive fine particles may be dispersed in the resin of the protective layer. Examples of the conductive fine particles include metals and metal oxides, preferably, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide-coated titanium oxide, tin-coated indium oxide, and antimony. Ultrafine particles of coated tin oxide and zirconium oxide may be mentioned. These conductive fine particles may be used alone or in combination of two or more. Generally, when particles are dispersed in the protective layer, it is necessary that the particle diameter of the fine particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed fine particles, and the particles are dispersed in the protective layer in the present invention. The particle size of the conductive fine particles is preferably 0.3 μm or less. The content of the conductive fine particles in the protective layer is preferably from 2 to 90% by mass, more preferably from 5 to 80% by mass, based on the total weight of the protective layer. The thickness of the protective layer is
0.1 to 10 μm is preferable, and 1 to 7 μm is more preferable. The application of the surface layer can be performed by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.

In the present invention, it is preferable that the electrostatic latent image forming step of forming an electrostatic latent image on the charged surface of the image carrier is performed by image exposure means. The image exposure unit for forming an electrostatic latent image is not limited to a laser scanning exposure unit that forms a digital latent image, but may be a normal analog image exposure or another light emitting element such as an LED. It does not matter if an electrostatic latent image corresponding to image information can be formed, such as a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter. <3> Process Cartridge of the Present Invention In the present invention, a toner image is formed by transferring and visualizing an electrostatic latent image formed on an image carrier, and the toner image is transferred to a transfer material. A process cartridge configured to be detachable from an image forming apparatus using the image forming method of the present invention, wherein at least two or more selected from a photosensitive member, a charging unit, and a developing unit Are integrally supported, and the toner is the magnetic toner of the present invention. <4> Method for Measuring Physical Properties Used in the Present Invention Methods for measuring various physical property data in the present invention are described in detail below. (1) Ratio of content (B) of iron element to content (A) of carbon element present on toner surface (B / A) In the present invention, iron relative to content (A) of carbon element present on toner surface Element content (B) ratio (B / A)
Is calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy analysis).

In the present invention, the ESCA apparatus and measurement conditions are as follows. Equipment used: PHI (Physical Electronics Industrie)
s, Inc.) 1600S type X-ray photoelectron spectrometer Measurement conditions: X-ray source MgKα (400 W) Spectral region 800 μmφ In the present invention, PH is determined from the measured peak intensity of each element.
The surface atomic concentration (atomic%) is calculated using the relative sensitivity factor provided by Company I.

A toner was used as a measurement sample. When an external additive was added to the toner, the toner was washed with a solvent that does not dissolve the toner, such as isopropanol, to remove the external additive. The measurement will be performed later. (2) Average circularity of toner The circularity in the present invention is used as a simple method for quantitatively expressing the shape of toner particles. In the present invention, a flow-type particle image analyzer FPIA manufactured by Toa Medical Electronics Co., Ltd. −
The shape of the toner particles is measured using a value of 1000, and the circularity is determined by the following equation (2). Further, as shown by the following equation (5), a value obtained by dividing the measured total circularity of all particles by the total number of particles is defined as an average circularity.

[0192]

(Equation 7)

[0193]

(Equation 8) The measuring device used in the present invention, "FPIA-
After calculating the circularity of each toner particle, in calculating the average circularity, the circularity obtained from the toner particles is changed from 0.400 to 1.000 at intervals of 0.010 to 0.400 or more.
Less than 0.410, 0.410 or more and less than 0.420 ... 0.990 or more and 1.000
A calculation method is used in which the area is divided into 61 divided ranges such as less than and 1.000, and the average circularity is calculated using the center value and frequency of the divided points.

The error between each value of the average circularity calculated by this calculation method and each value of the average circularity calculated by the above-mentioned calculation formula directly using the circularity of each particle is extremely small, and Therefore, in the present invention, the above-described calculation formula that directly uses the circularity of each particle is used in the present invention for data handling reasons such as shortening of calculation time and simplification of calculation formula. Utilizing the concept, a partially modified such calculation method is used.

The circularity in the present invention is an index indicating the degree of unevenness of the toner particles. The circularity is 1.000 when the toner particles are perfectly spherical, and the circularity becomes smaller as the surface shape becomes more complicated. .

As a specific method of measuring the circularity, about 5 mg of a toner is dispersed in 10 ml of water in which about 0.1 mg of a nonionic surfactant is dissolved, a dispersion is prepared, and an ultrasonic wave (20 kHz, 50 kHz) is used.
W) to the dispersion for 5 minutes to increase the concentration of the dispersion to 5,000 to 20,000.
Using the above-mentioned flow type particle image measuring device as 3 pieces / μl, 3
The circularity distribution of particles having a circle equivalent diameter of not less than μm is measured.

The outline of the measurement is described in the catalog of FPIA-1000 (June 1995 version) issued by Toa Medical Electronics Co., Ltd., the operation manual of the measuring apparatus and Japanese Patent Application Laid-Open No. 8-136439. It is as follows.

The sample dispersion liquid is passed through a flow path (spread along the flow direction) of a flat and flat transparent flow cell (thickness: about 200 μm). The strobe and the CC are connected so as to form an optical path that intersects with the thickness of the flow cell.
The D cameras are mounted so as to be located on opposite sides of the flow cell. While the sample dispersion is flowing,
Strobe light is applied at 1/30 second intervals to obtain an image of the toner particles flowing through the flow cell, so that each toner particle is captured as a two-dimensional image having a certain range parallel to the flow cell. The diameter of a circle having the same area is calculated as the equivalent circle diameter from the area of the two-dimensional image of each particle. The circularity of each particle is calculated from the projected area of the two-dimensional image of each toner particle and the perimeter of the projected image using the above-described circularity calculation formula. (3) Particle Size Distribution of Toner A Coulter Counter TA-II type (manufactured by Coulter, Inc.) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number distribution and a volume distribution and a CX-1 personal computer (manufactured by Canon) were used. Connect, electrolyte 1
A 1% NaCl aqueous solution is prepared using graded sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, a surfactant (preferably an alkylbenzene sulfonate) is used as a dispersing agent in 100 to 150 ml of the electrolytic aqueous solution.
Is added, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the volume and number of the toner were measured using the Coulter Counter TA-II, using a 100 μm aperture as the aperture. Calculate the volume distribution and number distribution of particles of 4040 μm. Then the number average particle size (D1)
A weight average diameter D4 based on weight obtained from the volume distribution (the median value of each channel is set as a representative value for each channel), and a weight distribution of 12.7 μm or more based on weight obtained from the volume distribution are obtained.

[0199]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Production Examples and Examples, but this does not limit the present invention in any way. Parts or% described in Examples are parts by mass or% by mass. <1> Production of iron oxide as magnetic material (Production of surface-treated iron oxide 1) A ferrous sulfate aqueous solution is mixed with 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions, and ferrous hydroxide is added. An aqueous solution was prepared.

While maintaining the pH of the aqueous solution at around 9, air was blown therein to carry out an oxidation reaction at 70 ° C. or higher to prepare a slurry liquid for generating seed crystals. Next, an aqueous solution of ferrous sulfate is added to this slurry solution so as to have an equivalent amount of 0.9 to 1.2 equivalents to the initial alkali amount (sodium component of caustic soda). Then, the slurry solution is maintained at pH 8 and oxidized while blowing air. The reaction was promoted, and the magnetic iron oxide particles generated after the oxidation reaction were washed, filtered, and once taken out. At this time, a small amount of a water-containing sample was collected and the water content was measured.

Next, after re-dispersing this water-containing sample in another aqueous medium without drying, the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n-
C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ ) to 100 parts of magnetic iron oxide
1.6 parts (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample) was added, and a coupling treatment was performed. The resulting hydrophobic iron oxide particles were washed, filtered, and dried by a conventional method, and then slightly aggregated particles were crushed to obtain surface-treated iron oxide 1. Incidentally, the volume average particle size of the surface-treated iron oxide 1 was 0.18 μm. (Production of surface-treated iron oxide 2) The oxidation reaction proceeds in the same manner as the production of surface-treated iron oxide 1, and the magnetic iron oxide particles generated after the oxidation reaction are washed, filtered, dried without surface treatment, and dried.
The agglomerated particles were crushed to obtain iron oxide particles. After the iron oxide particles are redispersed in another aqueous medium, the pH of the redispersed liquid is adjusted to about 6, and the silane coupling agent (nC ₁₀ H ₂₁ Si (OCH ₃ )) is stirred with sufficient stirring. ₃ ) was added to 3.2 parts of iron oxide particles per 100 parts to perform a coupling treatment. The generated hydrophobized iron oxide particles are washed, filtered, and dried by a conventional method, and then the aggregated particles are crushed,
Surface-treated iron oxide 2 was obtained. Incidentally, the volume average particle size of the surface-treated iron oxide 2 was 0.18 μm. (Production of surface-treated iron oxide 3) Surface-treated iron oxide 3 was obtained in the same manner as in the production of surface-treated iron oxide 1, except that the addition amount of the silane coupling agent was changed to 0.7 part. (Production of surface-treated iron oxide 4) Surface-treated iron oxide 4 was obtained in the same manner as in the production of surface-treated iron oxide 1, except that the amount of the silane coupling agent was changed to 0.3 part. (Production of surface-treated iron oxide 5) Polyvinyl alcohol (PVA-205, Kuraray Co., Ltd.) was placed in a flask equipped with a stirrer, an inert gas introduction pipe, a reflux condenser, and a thermometer.
200 parts of deionized water in which 0.1 part was dissolved. A preliminarily prepared mixture of 97.5 parts of styrene and 2.5 parts of glycidyl methacrylate in which 8 parts of benzoyl peroxide was dissolved in a polymerizable monomer was charged and stirred at high speed to form a uniform suspension. Then, the mixture was heated to 80 ° C. while blowing in nitrogen gas, and the polymerization reaction was performed by continuing stirring at this temperature for 5 hours. Thereafter, filtration, washing with water, and drying were performed to obtain a resin containing an epoxy group.

On the other hand, the oxidation reaction proceeds in the same manner as in the production of the surface-treated iron oxide 1, and the magnetic iron oxide particles formed after the oxidation reaction are washed, filtered, dried without surface treatment, and the aggregated particles are removed. Was crushed to obtain untreated iron oxide particles. 80 parts of the untreated iron oxide particles and the resin 20 containing the epoxy group
The mixture was kneaded with a Labo Plastomill at 180 ° C. and 100 rpm for 30 minutes to react the epoxy group-containing resin with the untreated iron oxide particles. After cooling, it was pulverized to obtain surface-treated iron oxide 5. <2> Production of magnetic toner (Production of magnetic toner A) 1.0M in 292 parts of ion-exchanged water
After adding 46 parts of -Na ₃ PO ₄ aqueous solution and heating to 70 ° C, 1.
67M of 0M-CaCl ₂ aqueous solution is gradually added to Ca ₃ (PO
₄ ) An aqueous medium containing ₂ was obtained.

Next, 83 parts of styrene, 17 parts of n-butyl acrylate, 0.6 part of divinylbenzene (purity 55%), saturated polyester resin (terephthalic acid / bisphenol A-
Condensates with EO and PO adducts, Mp 11000, Tg 69 ° C, acid value 12 mg KOH / g) 5 parts, negative charge control agent (monoazo dye-based Fe compound) 2 parts, α-methylstyrene dimer 2
And 1100 parts of the surface-treated iron oxide were uniformly dispersed and mixed using an attritor (Mitsui Miike Kakoki Co., Ltd.) to obtain a monomer composition.

This monomer composition was heated to 70 ° C., and 12 parts of an ester wax having an endothermic peak temperature of 80 ° C. in a DSC curve was added and mixed, and 5 parts of benzoyl peroxide as a polymerization initiator was added thereto. Was added.

The above monomer composition was put into the aqueous medium, and the mixture was stirred at 70 ° C. under a N ₂ atmosphere at 10,000 rpm for 10 minutes using a TK type homomixer (Tokusai Kika Kogyo Co., Ltd.). Granulated. 70 ° C while stirring with paddle stirring blades
For 24 hours. Thereafter, the suspension was cooled, and then dilute hydrochloric acid was added to dissolve calcium phosphate as a dispersion stabilizer, and filtration and washing were repeated to obtain toner particles. When the THF insoluble content of the toner particles was measured, it was 20% based on the binder resin component.

100 parts of the toner particles and 1.5 parts of a hydrophobic silica fine powder having a number average primary particle diameter of 10 nm, the surface of which was treated with hexamethyldisilazane and then treated with silicone oil, were mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) )) To prepare Magnetic Toner A. Table 2 shows the physical properties of Magnetic Toner A. Table 1 shows the raw materials used.

[0207]

[Table 1]

[0208]

[Table 2] (Production of Magnetic Toner B) A magnetic toner B was prepared in the same manner as in the production of the magnetic toner A except that the surface-treated iron oxide 2 was used instead of the surface-treated iron oxide 1. Table 2 shows the physical properties of Magnetic Toner B. (Production of Magnetic Toner C) A magnetic toner C was prepared in the same manner as in the production of the magnetic toner A, except that the surface-treated iron oxide 3 was used instead of the surface-treated iron oxide 1. Table 2 shows the physical properties of Magnetic Toner C. (Production of Magnetic Toner D) An unsaturated polyester resin (fumaric acid / bisphenol A-
Condensate with PO adduct, Mp10000, Tg65 ° C, acid value 12mg
Magnetic toner D was prepared in the same manner as in the production of magnetic toner A, except that 2.3 parts (KOH / g) were used. Table 2 shows the physical properties of Magnetic Toner D. The toner particles are THF
When the insoluble content was measured, it was 35% based on the binder resin component.
%Met. (Production of Magnetic Toner E) A magnetic toner E was prepared in the same manner as in the production of the magnetic toner A, except that 2 parts of t-dodecyl mercaptan was added instead of the α-methylstyrene dimer. Table 2 shows the physical properties of the magnetic toner E. The THF insoluble content of the toner particles was measured and found to be 20% based on the binder resin component. (Production of Magnetic Toner F) A magnetic toner F was prepared in the same manner as in the production of the magnetic toner A, except that t-butylperoxy-2-ethylhexanoate was used instead of benzoyl peroxide. Table 2 shows the physical properties of Magnetic Toner F. The THF insoluble content of the toner particles was measured and found to be 30% based on the binder resin component. (Production of Magnetic Toner G) 100 parts of the toner particles produced in the production of the magnetic toner A and 1.5 parts of hydrophobic silica fine powder having a hexamethyldisilazane-treated number average primary particle diameter of 10 nm were mixed with a Henschel mixer. Magnetic toner G was prepared. Table 2 shows the physical properties of Magnetic Toner G. (Production of Magnetic Toner H) The amount of ester wax used was reduced to 51
A magnetic toner H was obtained in the same manner as in the production of the magnetic toner A except that the toner was used as a part. Table 2 shows the physical properties of Magnetic Toner H. (Production of Magnetic Toner I)
Magnetic toner I was obtained in the same manner as in the production of magnetic toner A except that the amount was changed to 4 parts. Table 2 shows the physical properties of Magnetic Toner I. (Production of magnetic toner J) DS instead of ester wax
Magnetic toner J was obtained in the same manner as in the production of magnetic toner A, except that 12 parts of a low molecular weight polyethylene wax having an endothermic peak temperature of 112 ° C. in C was used. Table 2 shows the physical properties of Magnetic Toner J. (Production of Magnetic Toner K) A comparative magnetic toner K was obtained in the same manner as in the production of the magnetic toner A except that the surface-treated iron oxide 4 was used instead of the surface-treated iron oxide 1. Table 2 shows the physical properties of Comparative Magnetic Toner K. (Production of Magnetic Toner L) A comparative magnetic toner L was obtained in the same manner as in the production of the magnetic toner A except that 120 parts of the surface-treated iron oxide 5 was used instead of the surface-treated iron oxide 1. Table 2 shows the physical properties of Comparative Magnetic Toner L.

(Production of Magnetic Toner M) Ion-exchanged water 730
46 parts of a 1.0 M-Na ₃ PO ₄ aqueous solution was added to the mixture and heated to 60 ° C., and 67 parts of a 1.0 M-CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) _2. Was.

Next, 80 parts of styrene, 20 parts of n-butyl acrylate, 0.6 parts of divinylbenzene, 1 part of a negative charge control agent (monoazo dye-based Fe compound), and 5120 parts of surface-treated iron oxide were used in an attritor. And uniformly mixed and dispersed.

Next, this dispersion was heated to 60 ° C., and 12 parts of an ester wax having an endothermic peak temperature of 80 ° C. in DSC was added thereto and mixed.
2'-azobis (2,4-dimethylvaleronitrile)
(V65) 3 parts and 2,2′-azobisisobutyronitrile (AIBN) 4 parts were added to obtain a monomer composition.

[0212] The aqueous medium of the above monomer composition was charged in, and stirred 60 ° C., 10 min at 10,000rpm at TK homomixer under N ₂ atmosphere and granulated. Thereafter, the mixture was reacted at 60 ° C. for 10 hours while stirring with a paddle stirring blade.

After the completion of the reaction, the suspension was cooled, adjusted to pH 1.0 with dilute hydrochloric acid, and stirred for 1 hour. Then filtration,
After drying, a toner having a weight average particle size of 7.0 μm was obtained.

A magnetic toner M for comparison was prepared by mixing 100 parts of the toner particles and 1.5 parts of the hydrophobic silica fine powder used in the production of the magnetic toner A with a Henschel mixer. Table 2 shows the physical properties of Comparative Magnetic Toner M. The measurement of THF-insoluble content of the toner particles showed that the content was 65% based on the binder resin component. (Production of magnetic toner N) PO adduct of bisphenol A
369.5 g, 146.4 g of an EO adduct of bisphenol A, 126.0 g of terephthalic acid, 40.2 g of dodecenylsuccinic acid, and 77.7 g of trimellitic anhydride were placed in a glass four-necked flask, and a thermometer, a stainless steel stirring rod, a condenser, and A nitrogen inlet tube was attached, and the reaction was performed at 220 ° C. under a nitrogen stream in a mantle heater. The degree of polymerization was monitored from the softening point according to ASTM E28-67, and the reaction was terminated when the softening point reached 110 ° C. Next, styrene 65 parts, 2-ethylhexyl acrylate 35 parts, divinylbenzene 0.8 parts
10 parts of the polyester resin synthesized above and 3.5 parts of 2,2'-azobisisobutyronitrile were added to 5 parts of the surface-treated iron oxide 5 and 120 parts of the surface-treated iron oxide.
For 5 hours to obtain a polymerizable monomer composition. Then, 212.3 parts of the polymerizable monomer composition was added to 650 parts of an aqueous colloid solution of 4% tricalcium phosphate prepared in advance in a 2 liter glass separable flask,
Granulation was performed at 10,000 rpm for 2 minutes at room temperature using a TK homomixer.

Next, a four-neck glass lid was attached, a reflux condenser, a thermometer, a nitrogen inlet tube, and a stainless steel stirring rod were attached, and the flask was set in an electric heating mantle heater. While continuing to stir under nitrogen, the temperature was raised to 85 ° C. as the first polymerization,
The reaction was carried out for 0 hour to obtain seed particles. This was cooled to room temperature to obtain precursor particles. Next, 13 parts of styrene, 7 parts of 2-ethylhexyl acrylate, 0.4 parts of 2,2′-azobisisobutyronitrile (AIBN) prepared by an ultrasonic oscillator in an aqueous suspension of the precursor particles, Divinylbenzene 0.2
40.7 parts of a water emulsion consisting of 2 parts, 0.1 part of sodium lauryl sulfate and 20 parts of water was added dropwise to swell the precursor particles.

Thereafter, the temperature was raised to 85 ° C. as a second stage polymerization while stirring under nitrogen, and the reaction was carried out for 10 hours.
After cooling, the dispersion medium was dissolved in a 10% hydrochloric acid aqueous solution, filtered, washed with water, air-dried, dried at 45 ° C. for 12 hours under reduced pressure at 20 mmHg, and classified by an air classifier to obtain a toner having a weight average particle diameter of 7.8 μm. Particles were obtained. When the THF-insoluble content of the toner particles was measured, it was 35% based on the binder resin component.

Magnetic toner N was prepared by mixing 100 parts of the toner particles and 1.5 parts of the hydrophobic silica fine powder used in the production of magnetic toner A with a Henschel mixer. Table 2 shows the physical properties of the magnetic toner N. (Production of Magnetic Toner O) The toner particles L obtained in the production of the magnetic toner L were melt-kneaded with a biaxial extruder heated to 160 ° C. Thereafter, the cooled kneaded material was coarsely pulverized by a hammer mill, and the coarsely pulverized material was finely pulverized by a jet mill.
Further, the obtained pulverized product was classified. When the insoluble matter in THF was measured for this classified powder, it was 0% based on the binder resin component.

A magnetic toner O was prepared by mixing 100 parts of the classified powder and 1.5 parts of the hydrophobic silica fine powder used in the production of the magnetic toner A with a Henschel mixer. Table 2 shows the physical properties of Magnetic Toner O. (Production of Magnetic Toner P) The classified powder obtained in the production of the magnetic toner O was subjected to a surface modification (sphericalization) treatment by mechanical impact to obtain toner particles. 100 parts of the toner particles and 1.5 parts of the hydrophobic silica fine powder used in the production of the magnetic toner A were mixed with a Henschel mixer to prepare a magnetic toner P. Table 2 shows the physical properties of the magnetic toner P. (Production of Magnetic Toner Q) 200 parts of xylene was placed in a reaction vessel and heated to reflux temperature. A mixture of 83 parts of styrene, 17 parts of n-butyl acrylate, and 2.0 parts of di-tert-butyl peroxide was added dropwise, and the solution polymerization was completed in 7 hours under xylene reflux, and xylene was distilled off. A low molecular weight resin was obtained.

On the other hand, 83 parts of styrene and n-
17 parts of butyl acrylate, 0.5 parts of divinylbenzene, 0.2 parts of polyvinyl alcohol, 200 parts of water, and 0.3 parts of benzoyl peroxide were mixed and suspended and dispersed. The above suspension and dispersion solution was heated and maintained at 80 ° C. for 24 hours under a nitrogen atmosphere. After cooling, the solution was filtered, washed with water and dried to obtain particles of a high molecular weight resin. The THF insoluble content of the resin particles was measured and found to be 73%.

Next, 40 parts of high molecular weight resin particles, 60 parts of low molecular weight resin, 2 parts of negative charge control agent (monoazo dye-based Fe compound), 120 parts of surface-treated iron oxide 5, 120 parts of maximum endothermic peak
12 parts of ester wax at a temperature of 160 ° C. were mixed in a blender, and the mixture was melted and kneaded with a twin-screw extruder heated to 160 ° C. The cooled kneaded material was roughly pulverized with a hammer mill, and the coarsely pulverized material was finely pulverized with a jet mill. Crushed. Next, the obtained particles were subjected to a surface modification (sphericalization) treatment, and then classified. The THF insoluble content of this classified powder was measured and found to be 2% based on the binder resin component.

Further, 100 parts of the classified powder and 1.5 parts of the hydrophobic silica fine powder used in the production of the magnetic toner A were mixed with a Henschel mixer to prepare a magnetic toner Q. Table 2 shows the physical properties of the magnetic toner Q. (Production of Magnetic Toner R) Ethylene glycol dimethacrylate 1.2 parts, n-dodecyl mercaptan 1.1
Parts, styrene 83 parts, n-butyl acrylate 17 parts, azobisisobutyronitrile 2.4 parts, polyvinyl alcohol 0.2 parts and water 200 parts were mixed and suspended and dispersed. The above suspension and dispersion solution was heated and maintained at 90 ° C. for 10 hours under a nitrogen atmosphere. After cooling, the suspension was filtered, washed with water and dried to obtain particles of a high molecular weight resin. The THF insoluble content of the resin particles was measured and found to be 25%.

Next, 100 parts of high-molecular-weight resin particles, 2 parts of a negative charge control agent (monoazo dye-based Fe compound), 120 parts of surface-treated iron oxide, and 12 parts of ester wax having a maximum endothermic peak of 80 ° C. were mixed in a blender. The mixture was melted and kneaded with a biaxial extruder heated to 160 ° C., and the cooled kneaded material was coarsely pulverized by a hammer mill, and the coarsely pulverized material was finely pulverized by a jet mill. Next, the obtained particles were subjected to a surface modification (sphericalization) treatment, and then classified. The THF insoluble content of this classified powder was measured and found to be 1% based on the binder resin component. Further, 100 parts by weight of the classified powder and 1.5 parts of the hydrophobic silica fine powder used in the production of the magnetic toner A were dry-mixed with a Henschel mixer to prepare a magnetic toner R. Table 2 shows the physical properties of the magnetic toner R. <3> Production of Photoconductor (Production of Photoconductor 1) As a photoconductor, an Al cylinder having a diameter of 30 mm was used as a conductive substrate. On this, layers having the following structures were sequentially laminated by dip coating to prepare a photoreceptor. (1) Conductive coating layer: mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin. 15μ thickness
m. (2) Undercoat layer: mainly composed of modified nylon and copolymerized nylon. The thickness is 0.6 μm. (3) Charge generation layer: mainly composed of an azo pigment having absorption in a long wavelength region dispersed in a polyvinyl butyral resin. The thickness is 0.6 μm. (4) Charge transport layer: mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (Molecular weight of 20,000 according to Ostwald viscosity method) at a mass ratio of 8:10, and a polytetrafluoroethylene powder ( 10% by mass based on the total solid content, and uniformly dispersed. 25 μm thick. The contact angle with water was 95 degrees. In addition, the measurement of the contact angle used pure water, and the apparatus used Kyowa Interface Science Co., Ltd. contact angle meter CA-X type.

[0223]

Examples 1 to 10 and Comparative Examples 1 to 8 LBP-1760 was modified and used as the image forming apparatus shown in FIG. An organic photoconductor (OPC) drum was used as the electrostatic image carrier. A rubber roller charger coated with nylon resin and dispersed with conductive carbon as a primary charging member is brought into contact with the photoreceptor (contact pressure 60 g / cm), and a voltage obtained by superimposing an AC voltage of 2.0 kVpp on a DC voltage of -700 Vdc. To uniformly charge the photoreceptor. Following the primary charging, an electrostatic latent image is formed by exposing the image portion with a laser beam. At this time, the dark portion potential Vd = −70
0 V and the light portion potential VL = −150 V.

The gap between the photosensitive drum and the developing sleeve is 290
μm, and a layer thickness of about 7 μ
m, using a developing sleeve in which a resin layer with a JIS center line average roughness (Ra) of 1.0 μm is formed on a 16 mm diameter aluminum cylinder whose surface is blasted, a developing magnetic pole of 90 mT (900 gauss), and a toner layer thickness regulating member As thickness 1.0mm, free length 1.0
mm silicone rubber blade was contacted with a linear pressure of 29.4 N / m (30 g / cm).・ 100 parts of phenolic resin ・ 90 parts of graphite (particle size: about 7 μm) ・ 10 parts of carbon black Then, as a developing bias, DC bias component Vdc =
-500V, superimposed AC bias component Vp-p = 1600V, f = 20
00 Hz was used. The peripheral speed of the developing sleeve is 110% of the peripheral speed (99 mm / se) of the peripheral speed of the photoconductor (90 mm / sec) in the forward direction.
c). As a transfer member, a transfer roller (made of ethylene-propylene rubber in which conductive carbon is dispersed, a volume resistance value of the conductive elastic layer of 10 ⁸ Ωcm, a surface rubber hardness of 24 mm,
Diameter 20mm, contact pressure 59 N / m (60g / cm)) and photoconductor peripheral speed (90mm
/ sec), and the transfer bias was DC 1.5 kV. As a fixing method, an LBP-1760 fixing device that does not have an oil application function and that performs heating and pressure fixing by a heater via a film was used. At this time, a pressure roller having a surface layer of a fluororesin was used, and the diameter of the roller was 30 mm. The fixing temperature was set at 180 ° C., and the nip width was set at 6 mm. Using magnetic toners A to R as toners, an image output test was performed on 100 sheets each under normal temperature, normal humidity (25 ° C., 60% RH) and low temperature, low humidity (10 ° C., 15% RH) environment. . Note that 75 g / m ² paper was used as the transfer material. The evaluation of the magnetic toners A to R was performed as follows. [Evaluation of printout image] 1) Image density The 50th printout image under normal temperature and normal humidity was measured by a Macbeth reflection densitometer RD918 (manufactured by Macbeth) with respect to the printout image of a white background portion where the original density was 0.00. The concentration was measured. A: Very good (1.40 or more) B: Good (1.35 or more, less than 1.40) C: Normal (1.00 or more, less than 1.35) D: Bad (less than 1.00) 2) Fog 100th printout under low temperature and low humidity The fog density (%) of each image was calculated from the difference between the whiteness of the white background portion and the whiteness of the transfer paper, and the image fog was evaluated. In addition, the fog density was measured by "Reflectometer" (manufactured by Tokyo Denshoku Co., Ltd.). A: Very good (less than 1.5%) B: Good (1.5% or more, less than 2.5%) C: Normal (2.5% or more, less than 4.0%) D: Bad (4.0% or more) 3) Transferability Solid black image formation The transfer residual toner on the photoreceptor at the time is stripped by taping with Mylar tape, and from the Macbeth concentration of the stripped Mylar tape stuck on paper,
The evaluation was made by subtracting the Macbeth density from the paper with only Mylar tape attached. A: Very good (less than 0.05) B: Good (more than 0.05 to less than 0.1) C: Normal (more than 0.1 to less than 0.2) D: Bad (more than 0.2) 4) Fixability Second print under low temperature and low humidity About the out image,
A fixed image was rubbed with a soft thin paper while applying a load of 50 g / cm ² , and the reduction in image density (%) before and after rubbing was evaluated. A: less than 5% B: 5% or more, less than 10% C: 10% or more, less than 20% D: 20% or more [Evaluation of matching with image forming apparatus] 1) Matching with photoreceptor After completion of printout test, The occurrence of scratches on the photoreceptor drum surface and adhesion of residual toner and the effect on printout images were visually evaluated. A: Not generated B: Slight scratch generation C: Sticking or scratching D: Lots of sticking 2) Matching with the fixing device After the printout test, scratches on the fixing film surface and fixing of residual toner Was visually evaluated. A: Not generated B: Slightly adhered C: Adhered or flawed D: Excessively adhered The results obtained are shown in Table 3.

[0225]

[Table 3]

[Detailed Description of the Invention] According to the present invention, it is possible to provide a magnetic toner which is excellent in charging uniformity and fixing property and can obtain a high definition image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus for performing an image forming method of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus for performing the image forming method of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 photosensitive drum 102 developing sleeve (toner carrier) 104 magnet roller 114 transfer roller 116 cleaner 117 charging roller (contact charging member) 121 laser generator 124 register roller 125 transport belt 126 fixing device 140 developing device

────────────────────────────────────────────────── ─── front page continued (51) Int.Cl. ⁷ identifications FI theme coat Bu (reference) G03G 15/02 101 G03G 15/08 501Z 15/06 101 501D 15/08 501 504A 504Z 504 506A 9/08 101 506 302 325 384 (72) Inventor Takeshi Kaburagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Keiji Kawamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ryoichi Fujita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Michihisa Magome 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tatsuya Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo F-ter in Canon Inc. (Reference) 2H003 AA01 BB11 CC04 CC05 DD03 2H005 AA01 AA02 AA03 AA06 AA08 AA15 AB02 AB06 CA03 CA04 CA12 CA14 CA26 CA30 CB03 CB07 CB13 EA03 EA05 EA06 EA07 FA06 2H073 AA01 BA04 BA13 AD02 AD17 AD13 FA02

Claims (42)

[Claims] 1. A magnetic toner having toner particles containing at least a binder resin component and iron oxide,
i) the ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the surface of the toner particles measured by X-ray photoelectron spectroscopy is less than 0.001,
i) When the projected area equivalent diameter of the magnetic toner is C and the minimum value of the distance between the iron oxide and the surface of the toner particles in cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM) is D, 50 magnetic toners satisfying the relationship of C ≦ 0.02
Iii) the average circularity of the magnetic toner is
0.970 or more, and iv) In a molecular weight cloth measured by gel permeation chromatography (GPC) of a THF soluble portion of the magnetic toner, there is a peak top of a main peak in a molecular weight range of 5,000 to 50,000, and the following formula (1) ) Is less than or equal to 1.4, and V) A magnetic toner comprising an inorganic fine powder on the surface of a toner particle. 2. The magnetic toner according to claim 1, wherein the ratio (B / A) is less than 0.0005. 3. A toner satisfying the relationship of D / C ≦ 0.02 is 65 toners.
The magnetic toner according to claim 1, wherein the number is at least several percent. 4. A toner satisfying the relationship of D / C ≦ 0.02 is 75%.
The magnetic toner according to claim 1, wherein the number is at least several percent. 5. The toner according to claim 1, wherein the magnetic toner has a DSC curve measured by a differential scanning calorimeter.
The magnetic toner according to any one of claims 1 to 4, wherein the magnetic toner has an endothermic peak in a range of from about 110C to about 110C. 6. The toner according to claim 1, wherein said magnetic toner has a toner DSC curve measured by a differential scanning calorimeter.
The magnetic toner according to any one of claims 1 to 4, wherein the magnetic toner has an endothermic peak in the range of -90 ° C. 7. The endothermic peak according to the differential thermal analysis is derived from a wax component.
3. The magnetic toner according to item 1. 8. The magnetic toner according to claim 1, wherein the magnetic toner contains 0.5 to 50 parts by mass of a wax component based on 100 parts by mass of the binder resin component. . 9. GPC of the soluble matter in THF of the magnetic toner
In the molecular weight distribution measured by the above, the components having a molecular weight of 300,000 or more are less than 20 area% and the components having a molecular weight of 2000 to 5000 are less than 15 area% with respect to the total area of the soluble components derived from the binder resin component. The magnetic toner according to any one of claims 1 to 8, wherein 10. The GP soluble in THF of said magnetic toner.
In the molecular weight distribution measured by C, the components having a molecular weight of 300,000 or more are less than 10 area% and the components having a molecular weight of 2000 to 5000 are less than 10 area% based on the total area of the soluble component derived from the binder resin component. The magnetic toner according to claim 1, wherein: 11. A GP soluble in THF of said magnetic toner.
In the molecular weight distribution measured by C, the molecular weight is 8000-40.
000 has a peak top of the main peak, and the X is 1.1 or less.
The magnetic toner according to any one of the above. 12. The binder resin component according to claim 1, wherein the binder resin component contains at least a polymer obtained by polymerizing a monomer containing at least a styrene monomer using an organic peroxide. The magnetic toner according to any one of the above. 13. The magnetic toner according to claim 12, wherein the organic peroxide is diacyl peroxide. 14. The binder resin component according to claim 1, wherein the binder resin component includes a resin cross-linked by a cross-linking agent having two or more polymerizable double bonds in one molecule. The magnetic toner according to claim 1. 15. The binder resin according to claim 1, wherein the binder component resin contains a polymer obtained by radical polymerization of a monomer in the presence of a chain transfer agent. Item 6. The magnetic toner according to item 1. 16. The magnetic toner according to claim 15, wherein the chain transfer agent is an α-methylstyrene dimer. 17. The magnetic toner according to claim 1, wherein the iron oxide has been subjected to a surface hydrophobic treatment with a coupling agent in an aqueous medium. 18. The method according to claim 18, wherein the toner particles include a monomer, a crosslinking agent,
The toner particles are obtained by subjecting a monomer composition containing at least a hydrophobized iron oxide, a wax component, and a chain transfer agent to suspension polymerization in an aqueous medium using a polymerization initiator. The magnetic toner according to claim 1, wherein: 19. The magnetic toner according to claim 1, wherein the inorganic fine powder has a number average primary particle diameter of 4 to 80 nm. 20. The inorganic fine powder is at least one kind of inorganic fine powder selected from silica, titanium oxide and alumina having a number average primary particle diameter of 4 to 80 nm or a composite oxide thereof. 20. The magnetic toner according to any one of 1 to 19. 21. The magnetic toner according to claim 1, wherein the inorganic fine powder has been subjected to a hydrophobic treatment. 22. The magnetic toner according to claim 1, wherein the inorganic fine powder has been subjected to a hydrophobic treatment with at least silicone oil. 23. The magnetic toner according to claim 1, wherein the inorganic fine powder is treated with at least a silane compound and silicone oil. 24. A charging step of applying a voltage to a charging member to charge the image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the charged image carrier, and An image carrier that holds an image on the surface and a toner carrier that carries the magnetic toner on the surface are arranged facing each other to form a development area, and the magnetic toner is applied to the electrostatic latent image in the development area. The method includes a developing step of forming a toner image on an image carrier by transferring the image, and a transfer step of electrostatically transferring the toner image formed on the image carrier to a transfer material. An image forming method for forming an image, wherein the toner is the magnetic toner according to any one of claims 1 to 23. 25. The charging step, wherein the charging member is a contact charging member that contacts the image carrier by forming a contact portion,
The image forming method according to claim 24, further comprising a step of charging the image carrier by applying a voltage to the contact charging member. 26. The charging step, wherein the moving speed of the surface of the contact charging member forming the contact portion and the moving speed of the surface of the image carrier have a relative speed difference, and the image carrier is charged. 26. The process of claim 24 or 25,
2. The image forming method according to 1., 27. The method according to claim 24, wherein the charging step is a step of charging the image carrier while the contact charging member and the image carrier move in directions opposite to each other. 3. The image forming method according to 1., 28. The charging step, wherein the contact charging member is a roller member having Asker C hardness of 50 degrees or less, and the image carrier is charged by applying a voltage to the roller member. The image forming method according to any one of claims 24 to 27. 29. The charging step in which a DC voltage or an AC voltage having a peak-to-peak voltage of less than 2 × Vth (Vth: discharge start voltage in applying a DC voltage) (V) is superimposed on the DC voltage on the contact charging member. The image forming method according to any one of claims 24 to 28, further comprising a step of charging the image carrier by applying a voltage. 30. The charging step in which the image carrier is charged by applying a DC voltage to the contact charging member or a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage less than Vth (V) on the DC voltage. The image forming method according to any one of claims 24 to 28, which is a process. 31. The image forming method according to claim 24, wherein the image carrier is a photoconductor using a photoconductive substance. 32. The image forming method according to claim 24, wherein in the electrostatic latent image forming step, an electrostatic latent image is formed on an image carrier by image exposure. 33. The method according to claim 24, wherein in the developing step, the moving speed of the toner carrier surface in the developing area is 0.7 to 7.0 times the moving speed of the image carrier surface. An image forming method according to any one of the preceding claims. 34. The image forming method according to claim 24, wherein in the developing step, the surface roughness (Ra) of the toner carrier is 0.2 to 3.5 μm. 35. The method according to claim 24, wherein in the developing step, the toner carried on the toner carrier is a toner layer of 5 to 50 g / m ² . Image forming method. 36. In the developing step, the amount of toner carried on the toner carrier is regulated by a toner layer thickness regulating member disposed in contact with the toner carrier. 35. The image forming method according to any one of 35. 37. The image forming method according to claim 36, wherein the toner layer thickness regulating member is an elastic member. 38. In the developing step, the toner carried on the toner carrier has a thickness smaller than a gap between the image carrier and the toner carrier.
The image forming method according to any one of items 37 to 37. 39. The image forming apparatus according to claim 24, wherein in the developing step, the image bearing member and the toner bearing member are arranged so as to face each other with a certain gap therebetween, and the gap is 100 to 1000 μm. 39. The image forming method according to any one of items 38 to 38. 40. The developing step, wherein at least an AC electric field is applied as a developing bias between the toner carrier and the image carrier to develop an electrostatic latent image on the image carrier with toner. AC electric field the image forming method according to any one of claims 24 to 39, which is a ^{3 × 10 6 ~1 × 10 7} V / m, frequency 100~5000Hz electric field intensity of peak-to-peak . 41. The transfer step, wherein the transfer member is in contact with the image carrier via the transfer material at the time of transfer, and the toner image on the image carrier is transferred to the transfer material. The image forming method according to any one of claims 24 to 40. 42. An image forming apparatus for forming an image by forming a toner image by transferring and visualizing an electrostatic latent image formed on an image carrier by transferring toner, and transferring the toner image to a transfer material. A process cartridge configured to be detachable from the image carrier, an image carrier, charging means for charging the image carrier to a predetermined potential, and transferring toner to an electrostatic latent image formed on the photoconductor. At least two or more selected from a developing unit that visualizes the toner and forms a toner image are integrally supported, and the toner is the magnetic toner according to any one of claims 1 to 23. Characteristic process cartridge.