JP2002214847A - Image forming method - Google Patents

Abstract

(57) [Problem] To provide an image forming method which is excellent in fine line reproducibility, has high image quality without toner fog and carrier adhesion, and has a long life of an image carrier and a developer. The image bearing member has a surface resistance of 1 × 10 ¹⁰ to 1 × 10 ^16.
Ωcm, the magnetic carrier has a carrier core particle and a resin coating layer composed of at least two or more layers laminated thereon, the carrier core particle is a ferrite particle, and a lowermost layer of the resin coating layer of the magnetic carrier. Is a thermosetting resin containing metal oxide fine particles, and the upper layer is a thermosetting resin coated by a polymerization method, and the magnetic carrier has a number average particle size of 5 to 100 μm, The cumulative value of distribution having a diameter equal to or less than half the average particle diameter is 10% by number or less, and in the developing step, the developer magnetic brush composed of the two-component developer carried on the developer carrier is used. An image forming method is performed in which an alternating electric field is applied while contacting the image carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic carrier used as a developer for developing an electrostatic image in electrophotography, electrostatic recording and the like, and a two-component developer containing the carrier and a toner. It is about.

[0002]

BACKGROUND OF THE INVENTION US Patent No. 2,297,691
Various methods are described in JP-B-42-23910 and JP-B-43-24748. In each of these methods, an electrostatic latent image is formed by irradiating a photoconductive layer with a light image corresponding to a document, and then a color called a toner having the opposite polarity is formed on the electrostatic latent image. The electrostatic latent image is formed by forming a toner image by adhering fine powder, developed and, if necessary, transferred to a transfer material such as paper, and then fixed by heat, pressure or solvent vapor. A copy or printout is obtained.

In the process of developing the electrostatic latent image, an image is formed on the charged toner particles on the electrostatic latent image on the image carrier by utilizing the electrostatic interaction of the electrostatic latent image. . In general, among the methods for developing such an electrostatic latent image using toner, a two-component developer in which toner is dispersed in a medium called a carrier is particularly suitable for a full-color copying machine and a full-color printer in which particularly high image quality is required. Used.

In recent years, with the development of multimedia, computer image processing, and the like, a means for outputting a higher definition full-color image has been demanded. For this purpose, full-color copy images and print-out images have higher quality,
Efforts are being made to achieve high definition and high quality even to the image level of silver halide photography. In response to these demands, studies are being made from a process and material perspective.

The two-component developing method described above also includes a contact two-component developing method in which the developer magnetic brush performs development while rubbing the surface of the image carrier, and a non-contact type in which the developer magnetic brush does not contact the image carrier. It is classified into a two-component developing method. Non-contact two-component development has the advantage that the so-called carrier adhesion phenomenon in which carriers adhere to the image carrier does not easily occur, but in order to obtain a high-definition full-color image as described above, excellent fine line reproducibility and sufficient Contact two-component development that provides an image density is preferably used.

Further, when a developing bias is applied from the developer carrying member to the electrostatic latent image side, a method of superimposing an AC bias on a DC bias is more preferably used for high image quality.

There is also a method of improving the image quality by reducing the particle size of the toner or the carrier or densifying the developer magnetic brush. JP-A-59-104663 describes a method of using a magnetic carrier having a small saturation magnetization to densify a developer magnetic brush and achieve high image quality. This can also be expected to extend the life of the developer in order to reduce the magnetic share between the carriers or the toner.

However, in the method for achieving high image quality as described above, that is, in the contact two-component AC developing system, the reduction in the particle diameter of the carrier and the reduction in the magnetic force of the carrier are required for the image carrier. There is a difficulty in putting the carrier into practical use in order to easily cause a so-called carrier attachment phenomenon in which the carrier is attached.

[0009] On the other hand, from the viewpoint of multiple copy and printout, and from the viewpoint of ecology, it is desired to extend the life of the electrophotographic apparatus including the developer and the image carrier.

Conventionally, as an image carrier, a CdS-resin dispersion system, a ZnS-resin dispersion system, a Se evaporation system, a Se-Te evaporation system, a Se-As evaporation system, an OPC (organic photoconductor), and an a- There is a photoreceptor of Si type or the like, which is practically used.

[0011] Of these, OPC is the most popular,
Since the surface is made of resin, the durability is not yet enough.
On the other hand, a-Si type photoreceptors have extremely high surface hardness (Vickers hardness of 1000 or more), and have deterioration resistance, abrasion resistance, scratch resistance, impact resistance, etc. as compared with other photoreceptors. It is extremely excellent.

However, the a-Si type photoreceptor has a surface resistance of approximately 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm, which is relatively lower than other photoreceptors. When an image is formed by using an image carrier having such a low-resistance surface, a conventional two-component contact developing process as described above and an AC developing bias are applied to achieve high image quality. When using iron powder carrier or magnetic carrier made of ferrite coated with resin for developer, toner fog occurs, especially when using low magnetic force carrier to improve developer life, carrier adhesion occurs. There's a problem.

[0013] Also, in JP-A-11-24322,
From the viewpoints of extending the life of the developer and adhering the carrier, the surface treatment agent layer having an amino group on the surface of the magnetic particles to control the carrier resistance and the toner charge amount, and further comprises an inorganic substance and a cured phenol resin. A magnetic carrier having a three-layer structure has been proposed. However, magnetic particles that become carrier cores are surface-treated with a coupling agent and a resin layer is provided on the carrier. Coating unevenness tends to occur on the resin layer, and therefore charge injection occurs when a developing bias voltage is applied. May cause carrier adhesion.

On the other hand, before an electrostatic latent image is formed on the image carrier, a process called so-called primary charging for uniformly charging the entire surface of the image carrier is performed. So-called corona chargers using corona discharge have been used. However, in recent years, contact charging devices have been put to practical use instead. This aims at low ozone, low power, and downsizing of the apparatus, and a conductive roller or a magnetic brush roller is used as a charging member. As a charging method, in order to perform contact charging smoothly and uniformly and without being affected by environmental fluctuations, a voltage in which an AC component is superimposed is applied to the charging member as described in JP-A-63-149669. It is desirable to do.

In such a contact charging device as well, the essential charging mechanism uses a discharge phenomenon from the charging member to the image carrier, so that generation of ozone is inevitable.
Further, the voltage applied to the charging member needs to be at least a value equal to or higher than the desired image carrier surface potential.
When charging is performed using the C component, there are problems such as generation of vibration and abnormal noise due to an electric field, and deterioration of the surface of the image carrier due to discharge.

In order to solve such a problem, charging by direct injection of charges into the image carrier is desired. In order to inject electric charge directly into the surface of the image carrier, a method of charging the electric charge to the trap level of the electric charge present on the surface of the image carrier by using a charging member having a low resistance value and applying a long charging time is used. is there. However, in such a charging method, it is premised that the specific resistance of the charging member is very low, that is, less than 1 × 10 ³ Ωcm, and a large charge leak occurs due to a scratch or a pinhole generated on the surface of the image carrier. There is such a problem. Also, the time required for performing sufficient charging is not at a practical level.

Japanese Patent Application Laid-Open No. 6-39221 discloses a method in which a charge injection layer is provided on the surface of an image bearing member and charges are injected into the charge injection layer by a contact charging member. This makes it possible to solve the above-mentioned various problems in the contact charging device.

As the charging member used in the contact charging device as described above, a magnetic brush roller which can make a large contact nip with the image carrier and can uniformly contact the surface of the image carrier is particularly preferably used.

In a contact charging device using a magnetic brush roller, it is necessary that the individual magnetic particles constituting the magnetic brush contact each other to form a conductive path, and the charge flowing through the conductive path causes the surface of the image carrier to be charged. charging,
It is charged, but when impurities are mixed in the magnetic brush,
There is a problem that the charging characteristics change. For example, when a relatively large amount of toner particles or the like is mixed into the magnetic brush for some reason, such a problem may be realized. Recently, a cleaner-less process has been proposed in which the waste toner recovery portion is omitted in order to realize a reduction in the size of the entire apparatus and simplification of maintenance. The remaining toner is mixed with a high probability in the magnetic brush without being cleaned.

Further, by using the above-described contact two-component developing process and the AC developing bias for high image quality,
When a magnetic carrier with a low-resistance core resin-coated such as a conventional iron powder carrier or ferrite carrier with a core resistance of 1 × 10 ⁹ Ωcm or less is used as a developer, carrier adhesion and toner fog occur. And these toners,
When the developing magnetic carrier is mixed into the contact charging member, the contact charging ability may be insufficient.

Japanese Patent Application Laid-Open No. Hei 6-222676 discloses an image forming apparatus using a contact charging process of a charged magnetic brush, in which the resistance of a magnetic carrier used for a developer is higher than that of magnetic particles used for a charged magnetic brush. It has been proposed to use a common AC voltage power supply for development.However, particularly when a contact two-component development process is used, the resistance is controlled by changing the ferrite particle coating material described in the specification. However, when it is used as a magnetic particle for a charged magnetic brush and a magnetic carrier for a two-component developer, it is not possible to achieve high-quality full-color images.

For the reasons described above, an image forming method which can achieve low ozone generation using a contact two-component AC developing process which is excellent in fine line reproducibility and obtains a full-color image with high image density has been practically used. Not converted.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a highly durable image carrier and an image forming method capable of obtaining a toner image excellent in fine line reproducibility. It is in.

It is a further object of the present invention to provide an image forming method capable of obtaining a high quality toner image without toner fog.

An object of the present invention is to provide an image forming method which solves the above-mentioned problems, and in particular, provides an image forming method using a two-component developer and a contact charging process.

An object of the present invention is to provide an image forming method in which the generation of ozone is suppressed and no carrier adheres, and a high-quality toner image excellent in fine line reproducibility can be obtained.

It is an object of the present invention to provide an image forming method using a contact-charged magnetic brush, wherein the toner has a high transfer efficiency and has no toner fog.

[0028]

SUMMARY OF THE INVENTION The present invention is as follows. (1) a charging step of applying a voltage to the charging member to charge the image carrier, and a latent image forming step of forming an electrostatic latent image on the charged image carrier by performing image exposure; A developer carrier that carries a two-component developer containing a magnetic carrier and a toner on the surface is disposed to face the image carrier,
A developing step of transferring a toner of the two-component developer to the electrostatic latent image held on the surface of the image carrier to form a toner image, and a transfer step of transferring the toner image to a transfer material. In the image forming method including:
The surface resistance is 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm, the magnetic carrier has carrier core particles and a resin coating layer comprising at least two layers laminated thereon, and the carrier core particles are ferrite particles. The lowermost layer of the resin coating layer of the magnetic carrier is a thermosetting resin containing metal oxide fine particles, and the upper layer is a thermosetting resin coated by a polymerization method, and the magnetic carrier is The number average particle diameter is 5 to 100 μm, the distribution cumulative value of not more than half the number average particle diameter is 10 number% or less, and the developing step is carried on the developer carrying member. An image forming method, wherein an alternating electric field is applied while a developer magnetic brush made of the two-component developer is in contact with the image carrier. (2) The image forming method according to (1), wherein the magnetic carrier has a specific resistance of 1 × 10 ¹² Ωcm or more. (3) The image forming method according to (1) or (2), wherein the image carrier is an amorphous silicon photoconductor. (4) The image forming method according to (1) or (2), wherein the image carrier is a photoconductor whose surface layer is a charge injection layer. (5) The image forming method according to any one of (1) to (4), wherein in the charging step, the charging member is a contact charging member. (6) The image forming method according to (5), wherein the contact charging member is a magnetic brush made of magnetic particles for charging. (7) In the magnetic carrier, the outermost layer of the resin coating layer is a silicone-based resin (1) to (6).
Any one of the image forming methods. (8) The thermosetting resin coated by the polymerization method, which is an upper layer of the lowermost layer in the resin coating layer, contains metal oxide fine particles, (1) to (7). Image forming method. (9) The image forming method according to any one of (1) to (8), wherein the metal oxide fine particles in the resin coating layer are α-Fe ₂ O ₃ and / or magnetite. (10) The image forming method according to any one of (1) to (9), wherein the thermosetting resin of the resin coating layer is a phenol resin. (11) In the facing portion where the direction of rotation of the developer carrier and the direction of rotation of the image carrier are opposed to each other,
Characterized in that they are in counter directions to each other (1)-
The image forming method according to any one of (10) and (10). (12) The toner of the two-component developer has a weight average particle diameter of 1 to 10 μm.
The image forming method according to any one of 1).

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

When the present inventors conducted detailed studies,
As an image carrier, a surface resistance is 1 × 10 such as an amorphous silicon-based image carrier or an image carrier having a charge injection layer.
Using a photoreceptor of ¹⁰ to 1 × 10 ¹⁶ Ωcm, contact two-component system A
In the case of performing development by the C developing method, it has been found that when a conventional iron powder carrier or ferrite carrier is used as a magnetic carrier constituting a two-component developer, carrier adhesion and toner fogging significantly occur.

That is, when an image carrier having a relatively low surface resistance as described above and a developer using a magnetic carrier having a low specific resistance, such as a conventional iron powder carrier or a ferrite carrier, are used in combination, The potential of the electrostatic latent image on the carrier leaks through the magnetic carrier that comes into contact with and rubs, and the potential of the electrostatic latent image changes so as to approach the developing bias potential. The take-off potential decreases, and toner fog occurs. Also, it was found that when a developing bias voltage was applied, electric charges were injected into the magnetic carrier, which caused the carrier to be charged and the carrier to be easily attached at the same time.

Accordingly, it has been found that the use of a high-resistance magnetic carrier is effective in preventing this phenomenon. Specifically, the surface resistance of the image carrier is approximately 1 × 1
In the range of 0 ¹⁰ to 1 × 10 ¹⁶ Ωcm, the effect can be exerted if the specific resistance of the magnetic carrier is 1 × 10 ¹² Ωcm or more.

However, specific resistance like ferrite particles is
In the case of a magnetic carrier prepared by coating a resin with a low resistance of less than 1 × 10 ¹⁰ Ωcm as a core on which a resin is conventionally coated, the resistance is not sufficiently increased with a normal coating amount, and the resistance is reduced. Even if the coating amount is increased to increase the thickness, the portion of the thin coating layer generated by the coating unevenness becomes a leak site of the electric charge, so that it is impossible to prevent carrier adhesion and injection fog.

Therefore, the present inventors have found that even when ferrite particles are used as the core particles of the magnetic carrier, there is no fog,
We have also found a method of increasing the resistance of ferrite carriers that can provide high-quality images without carrier adhesion, and have developed a developer using such a magnetic carrier, and an image carrier having an amorphous silicon-based image carrier or a charge injection layer. The present invention has been achieved by using a combination with an image carrier having a low surface resistance such as the above.

That is, the image forming method of the present invention uses an image carrier having a surface resistance of 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm, and as a magnetic carrier of a developer, carrier core particles and at least two layers thereon. Using a magnetic carrier having a resin coating layer composed of the above laminate, the carrier core particles are ferrite particles, the lowermost layer of the resin coating layer of the magnetic carrier is a thermosetting resin containing metal oxide fine particles, And the upper layer is a thermosetting resin coated by a polymerization method,
The magnetic carrier has a number average particle size of 5 to 100 μm, and a distribution cumulative value of a half or less of the number average particle size is 10 μm or less.
% Or less. The image carrier of the present invention has a surface resistance of 1
There is no particular limitation as long as it is from × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm, but an amorphous silicon-based photoconductor or a photoconductor whose surface layer is a charge injection layer is preferable.

The amorphous silicon-based photoreceptor can be formed by a plasma CVD method using a silane-based source gas and using high frequency or microwave as a decomposition energy source for the source gas. The photoreceptor whose surface layer is a charge injection layer is not particularly limited as long as it has a charge injection layer as the outermost layer of the photoreceptor. It is also preferable that a charge injection prevention layer, a charge generation layer, a charge transport layer and the like are appropriately provided.

As the charge injection layer, a layer in which conductive fine particles are dispersed in an insulating and translucent binder resin to adjust the surface resistance is preferably used. An acrylic resin, a polycarbonate resin, a phenol resin, or the like is used as the insulating and transmissive binder resin. Further, as the conductive fine particles, SnO ₂ fine particles,
Zinc oxide fine particles, titanium oxide fine particles and the like are used.

When a magnetic brush is used as a charging member in the charging step, the charge injection layer is brought into contact with the charged magnetic brush to which a voltage is applied, so that the conductive fine particles are innumerable against the conductive substrate of the image carrier. Exist as independent float electrodes, and an effect of charging a capacitor formed by these float electrodes can be expected. Accordingly, the voltage applied to the contact charging member and the surface potential of the image carrier converge to the same value, and the effect of applying the minimum voltage is also recognized.

The surface resistance of the image carrier used in the present invention is 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm as described above, and more preferably in the range of 1 × 10 ¹² to 1 × 10 ¹⁵ Ωcm. Preferably, there is. When the resistance of the image carrier is less than 1 × 10 ¹⁰ Ωcm,
The charge injected from the charging member is not retained on the surface of the image carrier, and as a result, a phenomenon called image deletion may occur in the electrophotographic process of the reversal developing system. This is especially common under high humidity. The resistance of the image carrier is 1 × 1
If it exceeds ¹⁶ Ωcm, the charge is not sufficiently injected, so that a so-called charged positive ghost in which the toner unnecessarily rides on the poorly charged area of the image carrier may occur.

A method for measuring the surface resistance of the image carrier used in the present invention will be described. A comb-shaped electrode having an effective electrode length of 2 cm and an interelectrode distance of 120 μm was gold-deposited on the surface of the image carrier, and a resistance measurement device (414 manufactured by Hewlett-Packard Company) was used.
(0BpAMATER) and measure by applying a voltage of 100V.

As described above, the resistance of the image carrier is 1 × 1
Even in the range of 0 ¹⁰ to 1 × 10 ¹⁶ Ωcm, charging may not be performed properly if the specific resistance of the charging member is not in an appropriate range. This needs to be adjusted by the configuration of the charging member.For example, when using a charging magnetic brush composed of charging magnetic particles, the charging magnetic brush having a specific resistance of 1 × 10 ⁵ to 1 × 10 ⁸ Ωcm is used. The configured charging magnetic brush shows good charging properties. Particularly preferably, it is 1 × 10 ^{6 to} 5 × 10 ⁷ Ωcm.
In the case of another contact member, for example, a charging roller, the resistance of the conductive layer is preferably 1 × 10 ³ to 1 × 10 ⁹ Ωcm.
As the magnetic particles constituting the charged magnetic brush, for example, a magnetic metal such as iron, cobalt, and nickel, or a compound thereof (an oxide or the like) can be used. These may be coated with an appropriate coat resin, or may be subjected to an oxidation treatment, a reduction treatment, or the like to adjust the specific resistance to the above.

For example, hydrogen-reduced Zn-Cu ferrite, oxidized magnetite, etc. can be used. Also, binder-type magnetic particles in which a magnetic metal oxide and conductive fine particles (for example, titanium oxide, zinc oxide, tin oxide, and the like) are dispersed in a binder resin such as polycarbonate, silicone resin, and acrylic resin; A binder-type magnetic particle coated with an appropriate coat resin can also be used. The magnetic carrier of the two-component type developer used in the present invention has a specific resistance of the magnetic carrier of 1 × 10 ¹² Ωcm or more, and has a resin coating layer comprising a carrier core particle and at least two or more laminated layers thereon. The carrier core particles are ferrite particles, the lowermost layer of the resin coating layer of the magnetic carrier is a thermosetting resin containing metal oxide fine particles, and the upper layer is a thermosetting resin coated by a polymerization method. The magnetic carrier has a number average particle size of 5 to 100 μm, and a distribution cumulative value equal to or less than 1/2 times the number average particle size is 10 number% or less.

The specific resistance of the magnetic carrier is 1 × 10¹²Ωcm or less
Is preferred, more preferably 5 × 10 ¹²~ 1 × 10¹⁵In Ωcm
is there.

The specific resistance of the magnetic carrier or carrier core particles used in the present invention can be measured using a measuring device shown in FIG. The cell E is filled with magnetic carrier or carrier core particles, the electrodes 21 and 22 are arranged so as to be in contact with the filled magnetic carrier or carrier core particles, a voltage is applied between the electrodes, and a current flowing at that time is measured. Then, a method of obtaining the specific resistance is used. The conditions for measuring the specific resistance in the present invention are as follows: the contact area S between the filled magnetic carrier or carrier core particles and the electrode is about 2.3 cm ² , and the thickness d is about 2 m
m, the load of the upper electrode 22 is 180 g, and the measured electric field strength is 5 × 10 ⁴ V / m
And

The carrier core particles of the magnetic carrier used in the present invention include MO.Fe ₂ O ₃ or M
Magnetite and ferrite particles represented by the general formula of Fe ₂ O ₄ can be preferably used. Here, M is a divalent or monovalent metal ion Mn, Fe, Ni, Co, C
u, Mg, Zn, Cd, Li and the like correspond to each other, and M can be used alone or as a plurality of metals. For example, magnetite, gamma iron oxide, Mn-Zn ferrite, Ni-
Zn-based ferrite, Mn-Mg-based ferrite, Ca-M
Iron-based oxides such as g-based ferrite, Li-based ferrite, and Cu-Zn-based ferrite can be given.

The magnetic carrier used in the present invention has a resin coating layer laminated on carrier core particles.
1 from carrier core particles, which is the lowermost layer of the resin coating layer
The layer has a configuration in which metal oxide fine particles are contained in a thermosetting resin, and further has a thermosetting resin layer coated by a polymerization method as a second layer. The second resin coating layer may be made of resin alone, but preferably contains metal oxide fine particles having a high specific resistance such as α-Fe ₂ O ₃ . Since the second layer is formed by a polymerization method, it is preferable to increase the thickness of the coating layer, uniformly coat the coating layer, and further increase the carrier resistance.

In the magnetic carrier used in the present invention, a third layer may be further provided as the outermost layer in the above structure. If a silicone resin is used as the outermost layer resin, toner contamination, abrasion of the resin layer, etc. From the viewpoint of imparting durability to

Specific examples of the thermosetting resin used for the first resin coating layer of the magnetic carrier include, for example,
Phenolic resin, modified phenolic resin, maleic resin,
Alkyd resin, epoxy resin, acrylic resin, unsaturated polyester obtained by polycondensation of maleic anhydride-terephthalic acid-polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine -Guanamine resin, acetoguanamine resin, griptal resin, furan resin, silicone resin, polyimide resin, polyamideimide resin, polyetherimide resin, polyurethane resin and the like. The above-mentioned resins can be used alone or in combination. Further, a thermoplastic resin may be mixed with a curing agent or the like and cured to be used. Among them, it is preferable to use an acrylic resin.

The thermosetting resin used for the second layer includes non-vinyl condensation such as polyester resin, epoxy resin, phenol resin, urea resin, melamine resin, polyurethane resin, polyimide resin, cellulose resin and polyether resin. A system resin can be used. Among them, it is preferable to use a phenol resin.

In the method for producing a magnetic carrier used in the present invention, first, a first resin coating layer is provided on the carrier core particles. As a method, the carrier core particles are put into a mixer having a stirring blade and the like, and a resin solution to be a coating resin layer (hereinafter, referred to as “resin coating solution”) is poured while applying shear stress by the stirring blade, and the mixer is heated. Solvent to gradually evaporate to form a coating layer. In addition, a method in which the coating resin solution is sprayed while floating the carrier core particles using air to form a coating layer on the surface of the carrier core particles gradually, a spray drying method, and the like can be used.

After the first resin coating layer is formed on the carrier by the above method, the resin layer is cured by heat treatment, and the treatment temperature at this time is preferably in the range of 100 to 300 ° C.

The second resin coating layer is a layer coated with a thermosetting resin by a polymerization method. The resin coating layer formed by the polymerization method is excellent in that the carrier core particles can be uniformly coated. Therefore, using the carrier core particles of ferrite particles having a low resistance like the magnetic carrier used in the present invention, the resin coating layer is provided as the first layer as described above, and the resistance is slightly increased. By coating the second layer by a legal method, it is possible to increase the resistance as a magnetic carrier.

As a method for coating the carrier core particles by the polymerization method, for example, when coating with an epoxy resin, bisphenols and epichlorohydrin as starting materials are used, and similarly, when a phenol resin is used, phenols and aldehydes are used. In the case of urea resin, urea and aldehydes are used, and in the case of melamine resin, melamine and aldehydes are used to directly coat by polymerization reaction. As a specific example, when coating with a phenol resin, phenol and formalin in an aqueous medium in the presence of a basic catalyst, put the carrier core particles having the first resin coating layer obtained as described above, the carrier The phenol resin layer, which is the second layer, is formed by advancing the curing by the condensation polymerization reaction of phenol and formalin on the surface of the core particles.

In the production of the magnetic carrier,
It is essential that metal oxide fine particles are dispersed in the first resin coating layer. This is because, when the metal oxide fine particles are put in the first layer, fine irregularities due to the metal oxide fine particles are generated on the particle surface, and it becomes easy to form the second resin coating layer by polymerization. In the second resin coating layer, the dispersion of the metal oxide fine particles is not essential, but it is preferable to disperse the metal oxide particles in that the uniformity of the coating layer and the thickness of the coating layer can be increased to increase the carrier resistance.

[0055] As the metal oxide fine particles dispersed in the first and second layers of the resin coating layer, for example, magnetite represented by the general formula MO · Fe ₂ O ₃ or MFe ₂ O _4, the ferrite preferably Can be used. Al ₂ O ₃ , SiO ₂ , CaO, Ti
O ₂ , V ₂ O ₅ , CrO ₂ , MnO ₂ , α-Fe ₂ O ₃ , γ-
Fe ₂ O ₃ , CoO, NiO, CuO, ZnO, SrO,
Y ₂ O _3, ZrO ₂ system and the like can be used. These metal oxide fine particles are preferably subjected to a lipophilic treatment. That is, when the lipophilic metal oxide fine particles are dispersed in the coating resin, they can be uniformly and densely incorporated into the resin, so that the film quality of the resin layer is improved and This is because the performance as a carrier can be improved.

In the lipophilic treatment, the metal oxide fine particles are treated with a coupling agent such as a silane coupling agent or a titanate coupling agent, or the metal oxide fine particles are dispersed in an aqueous solvent containing a surfactant. There is a method such as making the surface lipophilic.

As the silane coupling agent used herein, those having a hydrophobic group, an amino group or an epoxy group can be used. Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, and vinyltris (β-methoxy) silane. Examples of silane coupling agents having an amino group include γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropylmethyldimethoxy Silane, N
-Phenyl-γ-aminopropyltrimethoxysilane. Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like. .

As the titanate coupling agent, for example, isopropyl triisostearoyl titanate,
Examples thereof include isopropyl tridodecylbenzenesulfonyl titanate and isopropyl tris (dioctyl pyrophosphate) titanate.

As the surfactant, a commercially available surfactant can be used as it is.

The magnetic carrier used in the present invention preferably has a number average particle size of 5 to 100 μm, more preferably 10 to 70 μm. Number average particle size is 5
If it is less than μm, particularly in the case of a contact two-component developing process, such as the image forming method of the present invention, in the case of a developing method using an AC developing bias, the carrier may be a carrier having substantially the same high resistance as described above. In some cases, adhesion cannot be avoided. When the number average particle diameter exceeds 100 μm, a high quality toner image having excellent fine line reproducibility, which is the object of the present invention, may not be obtained.

Further, 1 / (the number average particle diameter of the magnetic carrier)
It is necessary that the cumulative value of the distribution of the double diameter or less is 10% by number or less. If it exceeds 10% by number, especially when the number average particle diameter is 30 μm or less, the finely developed magnetic carrier tends to adhere to the carrier, and the effect of increasing the resistance may be lost. More preferably, the cumulative value of distribution having a diameter equal to or less than 1/2 times the number average particle diameter is 0 to 5% by number.
As a method of controlling the particle size distribution of the magnetic carrier, in addition to a method of removing coarse powder and fine powder by sieving with a mesh screen, a method of removing fine and ultrafine powder of the carrier by air classification after sieving may be mentioned. it can. The method for measuring the particle size of the magnetic carrier in the present invention is as follows. The particle size of the magnetic carrier used in the present invention is randomly determined by a scanning electron microscope (100 to 5,000 times).
300 or more carrier particles having a size of μm or more are extracted, and the particle size of the magnetic carrier is measured using a ferrite diameter in the horizontal direction with an image processing / analysis device Luzex3 manufactured by NIRECO CORPORATION to calculate the number average particle size. Based on the number-based particle size distribution measured under these conditions, the cumulative ratio of the number average particle size smaller than 1/2 times the diameter cumulative distribution is determined, and the cumulative value equal to or smaller than the 1/2 size diameter cumulative distribution is calculated.

The magnetization strength of the magnetic carrier used in the present invention is such that the magnetization strength (σ 1000) of the magnetic carrier at a magnetic field of 79.6 kA / m (1 k Oersted) is 4000 to 32000 kA / m ^2.
(40 to 320 emu / cm ³ ). When the magnetization intensity (σ1000) is less than 4000 kA / m ² (40 emu / cm ³ ), the magnetic carrier particles may not be sufficiently held by the developer carrier, and the carrier may adhere. When the magnetization intensity (σ1000) exceeds 32000 kA / m ² (320 emu / cm ³ ), the density of the developer magnetic brush becomes coarse, the dot reproducibility deteriorates, and the magnetic share between carriers increases. As a result, the magnetic carrier and the toner after the durability are deteriorated, and the image may be adversely affected.
The magnetic carrier, magnetite represented by the general formula MO · Fe ₂ O ₃ or MFe ₂ O _4, can be preferably used ferrite, wherein M is a divalent or monovalent metal ion, for example Mn, Fe , Ni, Co, Cu, Mg, Zn, Cd, Li, etc., and M is a single metal or a plurality of metals, and the intensity of magnetization can be adjusted by appropriately combining these metals. In the present invention, the intensity of magnetization of the magnetic carrier is defined by a magnetic field of 79.6 kA / m, but when a developer is applied to the image forming apparatus, the magnetic field acting on the developer is applied to the outside of the image forming apparatus. In order to reduce the leakage of the magnetic field or keep the cost of the magnetic field source low, it is set to several tens to one hundred and several tens of kA / m in many commercially available image forming apparatuses. Therefore, in the present invention, a magnetic field of 79.6 kA / m (1 k Oersted) is selected as a representative value of the magnetic field actually acting on the developer in the image forming apparatus, and the magnetic field of 79.6 kA / m is selected.
The magnetization intensity of the magnetic carrier at kA / m was defined. In addition, as a method of charging the image carrier used in the present invention, a method using a corona charger can also be used. More preferably, the charging member is a contact charging member such as a charging fur brush, a magnetic brush, and a resin roller. And a contact charging method using Among them, it is preferable to use a magnetic brush in that more uniform charging and high durability can be achieved.

When a magnetic brush composed of magnetic particles is used for the charging member of the image carrier, it is preferable that the specific resistance of the magnetic particles be 1 × 10 ⁵ to 1 × 10 ⁸ Ωcm as described above. This is considerably lower than the specific resistance of the magnetic carrier of the developer of the present invention, and the magnetic intensity of the magnetic particles used in the charged magnetic brush at a magnetic field of 79.6 kA / m (1 k Oersted) is not sufficiently high. In this case, the magnetic particles tend to adhere to the carrier on the image carrier. For this reason, the magnetic particles used for the charged magnetic brush need at least a higher magnetic force than the magnetic carrier of the developer, and the magnetization intensity at 79.6 kA / m (1 k Oe) is 20,000 kA / m ² (200 emu / cm ³ ). It is preferable that it is above.

The magnetic characteristics of the magnetic carrier and the magnetic particles for charging in the present invention can be measured using an oscillating magnetic field type automatic magnetic characteristics recording device BHV-30 manufactured by Riken Denshi Co., Ltd. The magnetic characteristic value of the magnetic carrier generates an external magnetic field of 79.6 kA / m (1 k Oersted), and the magnetization intensity at that time is obtained. The magnetic carrier is manufactured in a packed state in a cylindrical plastic container so as to be sufficiently dense. In this state, the magnetization moment is measured, and the actual weight when the sample is placed is measured to determine the magnetization intensity (Am ² / kg (emu / g)). Next, the true specific gravity of the carrier particles is determined by a dry automatic densimeter Acupic 1330 (manufactured by Shimadzu Corporation), and the magnetic carrier is obtained by multiplying the magnetization intensity (Am ² / kg (emu / g)) by the true specific gravity. Magnetization strength (kA / m ² (emu / cm ³ ))
Ask for. The magnitude of magnetization of the magnetic particles for charging can also be determined in the same manner. When a magnetic carrier having a relatively low magnetic force is used in the present invention, a developing method in which the rotation of the developer carrier and the rotation of the image carrier are in counter directions to each other can be preferably used. In this method, compared to the developing method in which the rotation of the developer carrier and the rotation of the image carrier are in the forward direction, the amount of the developer magnetic brush contacting a part of the image carrier at the same process speed, That is, since the absolute amount of toner increases, a high-quality image with high image density and no missing dots can be expected.

When using a magnetic carrier having a high magnetic force,
When the contact two-component AC development as in the present invention is performed using a developing method in which the rotation of the developer carrier and the rotation of the image carrier are in counter directions to each other, the rotation of the developer carrier and the rotation of the image carrier are performed. Are compared to the development systems in which
So-called scavenging, in which streaks appear on an image due to a rigid developer magnetic brush, is likely to occur. This is because the developer magnetic brush comes into stronger contact with the latent image and the toner on the latent image. However, when a developing magnetic carrier having a relatively low magnetic force is used as in the image forming method of the present invention, scavenging is unlikely to occur because the developer magnetic brush contacts the image carrier and the toner image relatively softly. .

The developing step in the image forming method of the present invention is a contact two-component AC developing system using a developer magnetic brush, and the alternating electric field applied to the developer magnetic brush is 500 to 5
Preferably it is 000 Hz. The applied alternating electric field is 500
When the frequency is lower than Hz, even if the magnetic carrier has a substantially high resistance as in the present invention, the electric charge may be injected into the image carrier through the magnetic carrier of the developer and adhere to the carrier. The applied alternating electric field is 50
When the frequency exceeds 00 Hz, the toner cannot follow the electric field, and the image quality is likely to deteriorate.

As the alternating electric field applied in the developing step, a conventional sine wave, triangular wave or rectangular wave can be used, but an alternating electric field whose waveform is appropriately controlled can also be used. For example, a first voltage that directs toner from the image carrier to the developer carrier, a second voltage that directs toner from the developer carrier to the image carrier, and a third voltage between the first voltage and the second voltage. An alternating electric field that forms a waveform pattern with a voltage can be used. In such a case, the frequency is in the range of the frequency of the alternating electric field in the present invention for one cycle of the waveform repetition pattern, that is, 500 to 500
Preferably it is 0 Hz.

The toner constituting the two-component developer used in the present invention has a weight average particle size in the range of 1 to 10 μm.
The cumulative distribution value of less than half the diameter of the number average particle diameter (D1) is
It is preferable that the number is not more than 20% by number, and the cumulative distribution value of not less than twice the weight average particle diameter (D4) is not more than 10% by volume. When the toner particle size exceeds 10 μm in weight average particle size, one toner particle for developing a latent image becomes large, so that a high-definition toner image, which is the object of the present invention, tends not to be obtained. More preferably, the weight average particle size is 3 to 8 μm.

A specific example of a method for measuring the particle size of the toner used in the present invention will be described.

To 100 to 150 ml of pure water, 0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added, and 2 to 20 mg of a measurement sample is added thereto. The electrolytic solution in which the sample is suspended is subjected to dispersion treatment with an ultrasonic disperser for 3 minutes, and the particle size distribution and the like are measured using a laser scan particle size distribution analyzer CIS-100 (manufactured by GALAI). In the present invention, particles of 0.5 to 60 μm are measured, and the number average particle diameter and weight average particle diameter measured under these conditions are determined by computer processing.

As the binder resin used for the toner constituting the two-component developer used in the present invention, when a heating / pressing roller fixing device having an oil application device is used, the following binder is used. Use of resin is possible.

For example, homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene and substituted products thereof; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene Copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-
Styrene such as vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Copolymers: polyvinyl chloride, phenolic resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin , Xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin and the like can be used.

In the heat and pressure roller fixing method in which almost no oil is applied, the offset phenomenon in which a part of the toner image on the image carrier is transferred to the roller and the adhesion of the toner to the image carrier are important issues. . These problems must be taken into account at the same time because toners that fix with less heat energy tend to block or cake during storage or in a developer.
Therefore, in the present invention, when using the heat and pressure roller fixing method in which almost no oil is applied, the selection of the binder resin is more important. Preferred binder resins include cross-linked styrene copolymers and cross-linked polyesters. Monomers of the crosslinked styrene copolymer preferably used in the heat and pressure roller fixing method in which almost no oil is applied include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate , Acrylic acid-2
Monocarboxylic acid having a double bond such as ethylhexyl, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide or a substituted product thereof; maleic acid , Maleic acid butyl, methyl maleate, dimethyl maleate and other dicarboxylic acids having a double bond and their substituted products; vinyl chlorides such as vinyl chloride, vinyl acetate and vinyl benzoate; ethylene-based compounds such as ethylene, propylene and butylene Olefins; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl monomers such as vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; It is.

As a crosslinking agent used to obtain a crosslinked styrene copolymer, a compound having two or more polymerizable double bonds is mainly used, and an aromatic divinyl compound such as divinylbenzene or divinylnaphthalene is used. A carboxylic acid ester having two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate;
Divinyl aniline, divinyl ether, divinyl sulfide, divinyl sulfone divinyl compound, a compound having three or more vinyl groups, etc. are used alone or as a mixture. The crosslinking agent is 0.01% based on the binder resin.
From 10 to 10% by mass (preferably 0.05 to 5% by mass) of the binder resin is preferably used at the time of synthesis in view of offset resistance and fixability.

When the pressure fixing method is used, a binder resin for a pressure fixing toner can be used. For example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer,
Examples include an ethylene-vinyl acetate copolymer, an ionomer resin, a styrene-butadiene copolymer, a styrene-isoprene copolymer, a linear saturated polyester, and paraffin.

In the toner constituting the two-component developer used in the present invention, it is preferable that charge controllability is blended (internally added) with toner particles or mixed (externally added) with toner particles. The charge control agent makes it possible to control the optimal charge amount according to the development system. In particular, in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge, and by using the charge control agent As a result of giving an appropriate charge amount from a toner having a small particle size to a toner having a large particle size, efficient development can be performed and a high quality image can be obtained. Examples of the positive charge control agent used in the present invention include a modified product of nigrosine and a fatty acid metal salt; a quaternary ammonium salt such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate; and dibutyltin. Oxides; diorganotin oxides such as dioctyltin oxide and dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate and dicyclohexyltin borate can be used alone or in combination of two or more. Of these, nigrosine,
A charge control agent such as a quaternary ammonium salt is particularly preferably used.

As the negative charge controlling agent used in the present invention, for example, an organometallic complex or a chelate compound is effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-acetylacetonate. There is chromium tert-butylsalicylate. Particularly preferred are acetylacetone metal complexes (including monoalkyl and dialkyl substituents), salicylic acid-based metal complexes (including monoalkyl and dialkyl substituents) or salts,
Particularly, a salicylic acid-based metal complex or a salicylic acid-based metal salt is preferable.

The above-mentioned charge control agent (having no function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is
Specifically, it is preferably 4 μm or less (more preferably 3 μm or less). At the time of internal addition to the toner, such a charge control agent is used in an amount of 0.1 to 20 parts by mass (and more
To 10 parts by mass).

Further, it is preferable to add fine silica powder to the toner constituting the two-component developer used in the present invention. When the toner and the silica fine powder are combined, abrasion is remarkably reduced because the silica fine powder is interposed between the toner particles and the surface of the magnetic carrier or the developer carrier. As a result, the life of the toner and the magnetic carrier and / or the developer carrier can be prolonged, and stable chargeability can be maintained. It can be used as a system developer. In particular, in the case of a toner having a weight average particle size of 10 μm or less, the specific surface area has a weight average particle size of 10 μm.
m, the number of contact between the toner particle surface and the magnetic carrier increases when the toner particles and the magnetic carrier are brought into contact with each other for triboelectric charging because the weight average particle diameter is larger than 10 μm. Abrasion of the toner particles and contamination of the magnetic carrier are apt to occur, but in such a case, it is possible to obtain a good two-component developer by adding the silica fine powder as described above.

As the silica fine powder, any of fine silica powders produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a fine silica powder obtained by a dry method. The dry method referred to here is
For example, a method for producing a fine silica powder produced by vapor phase oxidation of a silicon halide compound.

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

As the silica fine powder here, anhydrous silicon dioxide (colloidal silica); silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate can be applied.

Among the above silica fine powders, the specific surface area by nitrogen adsorption measured by the BET method is 30 m ² / g or more (particularly 50 to 50 m ² / g).
Those within the range of 400 m ² / g) give good results. It is preferable to use 0.01 to 8 parts by mass, preferably 0.1 to 5 parts by mass of the silica fine powder with respect to 100 parts by mass of the toner. The BET specific surface area is determined by a BET multipoint method using a fully automatic gas adsorption amount measuring apparatus: Autosorb 1, manufactured by Yuasa Ionics Co., Ltd., and using nitrogen gas as the adsorption gas. In addition, as pretreatment of a sample, deaeration is performed at a temperature of 50 ° C. for 10 hours. When the toner constituting the two-component developer used in the present invention is used as a positively-charged toner, it is used as a fine silica powder added to prevent toner abrasion, magnetic carrier, and contamination of the developer carrier surface. It is preferable to use positively-charged silica fine powder without deteriorating charging stability, rather than negatively-charged silica fine powder. When used as a negatively chargeable toner, it is preferable to use negatively chargeable silica fine powder for the same reason.

Since the silica fine powder is generally negatively charged, a method for obtaining a positively charged silica fine powder is to use the untreated silica fine powder described above with at least one nitrogen atom in the side chain. There is a method of treating with a silicon oil having an organo group, a method of treating with a nitrogen-containing silane coupling agent, or a method of treating with both.

In the present invention, the positively-charged silica refers to a silica having a positive tribocharge with respect to the iron powder carrier when measured by a blow-off method. The silica fine powder used in the toner constituting the two-component developer used in the present invention is treated with a silane coupling agent as necessary as described above, and further treated with an organosilicon compound or the like for the purpose of hydrophobicity. And may be treated with the following treating agent that reacts or physically adsorbs with the silica fine powder.

Examples of such treating agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethyl Chlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane , Dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldi Siloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 per molecule
Dimethylpolysiloxane having hydroxyl groups bonded to Si per unit, each of which is a terminal unit. These are used alone or as a mixture of two or more. The treating agent is preferably used in an amount of 1 to 40% by mass based on the silica fine powder.

Instead of silica fine powder, a BET specific surface area of 50
Fine titanium oxide powder (TiO ₂ ) of up to 400 m ² / g may be used. Further, a mixed powder of silica fine powder and titanium oxide fine powder may be used.

The toner constituting the two-component developer used in the present invention includes a fine powder of a fluorine-containing polymer (for example, polytetrafluoroethylene, polyvinylidene fluoride or tetrafluoroethylene-vinylidene fluoride copolymer). (Fine powder) can also be added.
In particular, polyvinylidene fluoride fine powder is preferred in terms of fluidity and abrasiveness. The amount added to the toner is 0.01 to
2.0 mass% is preferable, 0.02 to 1.5 mass% is particularly preferable, and 0.02 to 1.0 mass% is more preferable.

In the toner constituting the two-component developer used in the present invention, conventionally known dyes and / or pigments can be used as colorants. For example,
Carbon black, phthalocyanine blue, peacock blue, permanent red, lake red, rhodamine lake, Hanza yellow, permanent yellow, benzidine yellow and the like can be used. As its content, 0.1 to 20 parts by mass relative to 100 parts by mass of the binder resin,
The amount is preferably 0.5 to 20 parts by mass, more preferably 12 parts by mass or less, more preferably 0.5 to 9 parts by mass, in order to improve the transparency of the OHP film on which the toner image is fixed.

The toner constituting the two-component developer used in the present invention includes low molecular weight polyethylene, low molecular weight polypropylene,
It is also a preferred embodiment of the present invention to add 0.5 to 5% by mass of a wax-like substance such as microcrystalline wax, carnauba wax, sasol wax and paraffin wax.

In the toner constituting the two-component developer used in the present invention, other additives may be further used, if necessary.

To prepare the toner constituting the two-component developer used in the present invention, a pulverized product obtained by kneading a thermoplastic resin with a pigment paste as a coloring agent, cooling and kneading the mixture,
The charge control agent, other additives, etc. were sufficiently mixed by a mixer, and then melted, kneaded, and kneaded using a heat kneader such as a heating roll, kneader, or extruder to make the resins compatible with each other. A pigment or dye is dispersed or dissolved therein, and after cooling and solidification, pulverization and strict classification are performed to obtain a toner. The toner can be used as it is as it is, but if necessary, an external additive such as silica fine powder is added to the obtained toner, and the toner and the external additive are mixed using a mixer such as a Henschel mixer. By doing so, a toner can be obtained. Furthermore, as the toner used in the present invention, a toner which is entirely or partially formed by a polymerization method can be used. In the case of such a toner, the residual monomer content is preferably 1000 ppm or less. If there are many components acting as a solvent for the binder resin as well as the monomer in the toner, the fluidity of the toner is lowered to deteriorate the image quality, and the blocking property is lowered. In addition to the performance directly related to the toner, especially when an organic semiconductor is used as the photoconductor, it also accompanies the deterioration phenomenon of the photoconductor such as memory ghost and blurred image other than the fusion phenomenon of the toner on the photoconductor drum. May cause problems. In addition to the matters relating to the performance of the product, there is a problem that the residual monomer component is volatilized at the time of fixing to generate an odor. It is also possible to use a toner in which the toner has a core / shell structure and the shell portion is formed by polymerization.

Needless to say, the function of the core / shell structure can provide anti-blocking properties without impairing the excellent fixing performance of the toner. By providing the above shell layer, magnetic carrier contamination can be significantly reduced. Further, compared to a bulk polymerized toner having no core, polymerizing only the shell portion facilitates removal of residual monomers in a post-treatment step after the polymerization step. When a wax component is used as a core, magnetic carrier contamination can be significantly reduced by providing a shell layer of a resin component on the surface.

The main component of the core portion is preferably a substance having a low softening point, and a compound having a main peak maximum value of 40 to 90 ° C. measured according to ASTM D3418-8 is preferred.
If the maximum peak is less than 40 ° C., the self-cohesive force of the low softening point substance becomes weak, and as a result, the high temperature offset property becomes weak, which is not preferable. On the other hand, if the maximum peak exceeds 90 ° C., the fixing temperature increases, which is not preferable.

Further, in the case of obtaining a toner by a direct polymerization method, since the granulation and polymerization are carried out in an aqueous system, when the temperature of the maximum peak value is high, a substance having a low softening point mainly precipitates during the granulation and the suspension system is formed. It is not preferable because it inhibits.

The temperature of the maximum peak value can be measured using, for example, DSC-7 manufactured by Perkin Elemer Corporation. For example, the temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of the calorific value uses the heat of fusion of indium. For the sample, an aluminum pan is used, an empty pan is set as a control, and the measurement is performed at a heating rate of 10 ° C./min.

Specific examples of the low softening point substance include paraffin wax, polyolefin wax, Fischer-Tropsch wax, amide wax, higher fatty acid, ester wax, derivatives thereof, and graft / block compounds thereof. .

The low softening point substance is preferably added to the toner in an amount of 5 to 30% by mass. If the addition is less than 5% by mass, it tends to burden the removal of the residual monomers described above. If the addition exceeds 30% by mass, coalescence of toner particles occurs during granulation even in the production method by polymerization. It is easy to produce a product having a wide particle size distribution, which is not suitable for the present invention. Although the toner particles produced by the pulverization method or the polymerization method as described above can be used as they are, it is necessary to use the above-mentioned metal oxide fine powder such as silica fine powder or the organic fine powder such as a fluorine-containing polymer. It is also possible to externally add an appropriate amount of the corresponding type using a mixer such as a Henschel mixer.

[0099]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by the embodiments.

In the examples, the triboelectric charge was determined as follows.

The toner and the carrier have a toner mass of 5% by mass.
And mix for 2 minutes with a Yayoi shaker. This mixed powder (developer) is placed in a metal container equipped with a 635-mesh conductive screen at the bottom, the toner is sucked by a suction machine, and the weight difference between before and after suction is indicated on an electrometer connected to the container. The amount of triboelectric charge of the toner is obtained from the value of the charge amount Q ′ thus obtained. At this time, the suction pressure is 250m
mHg. By this method, the triboelectric charge amount Q of the toner
Is calculated using the following equation.

Q (μC / g) = Q ′ × (W1−W2) ⁻¹ (where W1 is the weight before suction, W2 is the weight after suction, and Q ′ is connected to a metal container. <Example of Toner Production> [Toner Production Example 1]-A polyester resin obtained by condensing 100 parts by mass of propoxylated bisphenol and fumaric acid-C.I. I. Pigment Red 122 4 parts by mass I. Basic Red 12 1 part by mass ・ Chromium complex salt of di-tert-butylsalicylic acid 4 parts by mass After sufficiently premixing, melt kneading, and after cooling, coarsely pulverized to a particle size of about 1 to 2 mm using a hammer mill. did. Next, it was pulverized by a pulverizer using an air jet method. Further, the obtained finely pulverized product was classified using an elbow jet classifier to obtain negatively chargeable magenta toner particles.

A magenta toner was prepared by mixing 100 parts by mass of the above toner particles and 0.8 parts by mass of hydrophobically treated fine titanium oxide powder with a Henschel mixer. The number average particle diameter (D1) of this toner is 6.4 μm, the weight average particle diameter (D4) is 8.5 μm, and is 1/1 of the number average particle diameter (D1).
The cumulative value of distribution below the double diameter was 13.2% by number, and the cumulative value of distribution over twice the diameter of the weight average particle diameter (D4) was 0% by volume. [Toner Production Example 2] In a 2 liter four-necked flask equipped with a high-speed stirrer TK-Homomixer, ion-exchanged water was added.
700 parts by mass and 0.1 mol / l-Na ₃ PO ₄ aqueous solution 430
The rotating speed was adjusted to 12,000 by adding parts by mass, and the mixture was heated to 60 ° C. Here, 1.0 mol / liter-CaCl ₂ aqueous solution 66
Parts by weight are gradually added, and a fine hardly water-soluble dispersant Ca
A dispersion medium system containing ₃ (PO ₄ ) ₂ was prepared.

On the other hand, the dispersoid system is as follows.・ Styrene monomer 160 parts by mass ・ n-butyl acrylate monomer 32 parts by mass ・ C. I. Pigment Red 202 11 parts by mass ・ Saturated polyester 8 parts by mass (terephthalic acid-propylene oxide modified bisphenol A; acid value 15, peak molecular weight 6000) ・ Salicylic acid metal compound 2 parts by mass ・ Compound represented by the following general formula 60 parts by mass ( (Maximum peak value 59.4 ℃)

Embedded image [Wherein, a and b represent an integer of 0 to 4, a + b is 4, R 1 and R 2 represent an organic group having 1 to 40 carbon atoms,
And a group in which the carbon number difference between R ₁ and R ₂ is 10 or more,
n and m each represent an integer of 0 to 15, and n and m do not become 0 at the same time. After the above mixture was dispersed for 3 hours using an attritor, a dispersion to which 10 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was added was poured into a dispersion medium. Then, the mixture was granulated for 15 minutes while maintaining the rotation speed.
Then, the stirrer was changed from a high-speed stirrer to a propeller stirring blade, the internal temperature was raised to 80 ° C., and polymerization was continued at 50 rotations for 10 hours. After the completion of the polymerization, the slurry was cooled and dilute hydrochloric acid was added to remove the dispersant. Further washing and drying were performed. 2% by mass of hydrophobically treated titanium oxide was externally added to the obtained toner particles,
A magenta toner having excellent fluidity was obtained. The number average particle size (D1) of this toner is 5.6 μm, and the weight average particle size (D4) is
6.5 μm, and the cumulative distribution value of less than half the diameter of the number average particle diameter (D1) is 11.5 number%, and the weight average particle diameter (D1)
In 4), the cumulative distribution value of the double diameter or more was 0% by volume.

[0105]

Example 1 <Preparation of Ferrite Carrier Core Particles> Fe ₂ O ₃ = 50 mol%, CuO = 27 mol%, Zn
It was weighed so that O = 23 mol% and mixed using a ball mill. After calcining this, it was pulverized by a ball mill and further granulated by a spray drier. This was sintered to obtain carrier core particles having a number average particle size of 40 μm. Next, after dissolving 10 parts by mass of a phenol resin (trade name: Plyofen (manufactured by Dainippon Ink and Chemicals, Inc.)) in 100 parts by mass of methyl cellosolve, lipophilic with 1.0 part by mass of γ-aminopropyltrimethoxysilane Treated α-Fe ₂ O ₃ fine particles (number average particle size 0.60 μm, specific resistance 2 ×
7 parts by mass of (10 ⁹ Ωcm) were dispersed to prepare a coating resin solution. The method for measuring the particle size of the α-Fe ₂ O ₃ fine particles is described below. The number average particle diameter of the α-Fe ₂ O ₃ fine particles was 5,000 to 5,000 using a transmission electron microscope H-800 manufactured by Hitachi, Ltd.
Using a photographic image magnified 20,000 times, randomly extract 300 or more particles having a particle diameter of 0.01 μm or more, and use an image processing analyzer Luzex3 manufactured by Nireco Co., Ltd. to obtain a metal oxide particle diameter having a horizontal Feret diameter. Measured as
The number average particle diameter is calculated by averaging. Put 1500 parts by mass of the carrier core particles into a mixer having a stirring blade,
The above-mentioned carrier-coated resin solution was poured while applying shearing stress by stirring. Next, the inside of the mixer was heated to evaporate the solvent, thereby coating the carrier core particles with the resin. After heating the obtained carrier particles at 150 ° C. for 2 hours, they are crushed,
Classification was further performed using a 200-mesh sieve to obtain a resin-coated carrier (a). Observation of the surface of the obtained resin-coated carrier (a) with a scanning electron microscope (FE-SEM) revealed that α-
Irregularities due to Fe ₂ O ₃ fine particles were observed, and it was found that the particles were uniformly covered with the resin. When the specific resistance of the resin-coated carrier (a) was measured, it was 2.3 × 10 ¹¹ Ωc
m.

Next, in a four-necked flask, 5 parts by mass of phenol, 7 parts by mass of 37% formalin, 400 parts by mass of the resin-coated carrier (a), and α-lipophilicized α-aminopropyltrimethoxysilane. -20 parts by mass of Fe ₂ O ₃ fine particles, 5 parts by mass of 25% ammonia water, and 418 parts by mass of water were charged,
Raise to 85 ° C over 60 minutes with stirring, then at 85 ° C
Hold for 120 minutes to advance the curing reaction of the phenolic resin,
A phenol resin layer containing α-Fe ₂ O ₃ fine particles was formed on the carrier surface.

Next, the content in the flask was cooled to 30 ° C., 0.5 L of water was added, the supernatant was removed, and the lower layer precipitate was washed with water and air-dried. Next, this was dried under reduced pressure (5 mmHg or less) at a temperature of 150 to 180 ° C. for 2 hours, and then classified with a 200-mesh sieve to obtain a resin-coated carrier (b).

The obtained resin-coated carrier (b) has a number average particle size of 46 μm, and is measured by a scanning electron microscope (FE-SEM).
As a result, irregularities due to α-Fe ₂ O ₃ fine particles were observed, and it was found that the particles were uniformly coated with the resin.

After the resin-coated carrier (b) was cut with a microtome to form a thin piece, the cross-sectional structure of the carrier was observed with a scanning electron microscope (FE-SEM). As a result, two layers were formed on the surface of the ferrite core particles. A resin layer containing α-Fe ₂ O ₃ fine particles was observed.

When the specific resistance of the resin-coated carrier (b) was measured, it was 3.8 × 10 ¹⁴ Ωcm. <Magnetic particles for contact charging magnetic brush> (Core particles) 200 parts by mass of hydrogen-reduced Zn-Cu ferrite (number average particle size 40.0 μm, specific resistance 5 × 10 ⁶ Ωcm) (coat resin solution) 1.0% by mass of polycarbonate Epoxy-modified silicone resin 1.0 parts by mass-Conductive titanium oxide 4.0 parts by mass-Tetrafluoroethylene resin particles (0.25 μm) 0.2 parts by mass-Xylene solution 14.0 parts by mass Each formulation of the above coating resin solution was mixed with glass beads. The mixture was dispersed with a paint shaker for 2 hours to prepare a coat resin solution. This was coated on the above-mentioned core particles using a spray-type fluidized-bed dryer and Spiracoater (manufactured by Okada Seiko Co., Ltd.), and dried at 150 ° C. for 1 hour. The specific resistance of the obtained magnetic particles for contact charging magnetic brush was 8.9 × 10 ⁶ Ωcm, and the number average particle diameter was 40.1 μm. Magnetization strength at 79.6 kA / m (1 k Oersted) (σ1000) = 25030 kA / m ² (250.3 emu / c
m ³ ) (the true specific gravity of the magnetic particles is 5.02 g / cm ³ ).

The specific resistance and the number average particle diameter of the magnetic particles for the contact charging magnetic brush and the core particles used here were measured in the same manner as in the above-mentioned method for measuring the characteristics of the magnetic carrier for development.

Resin-coated carrier (b) and toner production example 1
Was mixed with the magenta toner described in (1) so that the toner concentration became 6% by mass to prepare a developer. The triboelectric charge of the toner was -27.3 μC / g.

An image was formed from this developer using a modified full-color laser copying machine CLC-500 manufactured by Canon. FIG. 1 is a schematic diagram showing the periphery of the developing section. The distance A between the developer carrying member (developing sleeve) 1 and the developer regulating member (magnetic blade) 8 of the full color laser copying machine made by Canon is 600 μm, and the distance between the developing sleeve 1 and the image carrying member (photosensitive drum) 2 B was 400 μm. At this time, the developing nip C was 5 mm.

The peripheral speed ratio between the developing sleeve 1 and the photosensitive drum 2 is 2.2: 1, the traveling directions are counter directions to each other as shown in FIG.
The magnetic field was 79.6 kA / m (1 k Oersted), and the developing conditions were such that the alternating electric field was 1800 V having a waveform as shown in FIG. 2 and the frequency was 3000 Hz, and the developing bias was -300 V. . A dark brush potential (Vd) of the photosensitive drum was 400 V and a bright potential (VL) was 50 V using a magnetic brush type contact charging member. The voltage applied to the contact charging member 3 was a DC bias of -560V.

As the photosensitive drum 2, a negatively chargeable amorphous silicon photosensitive member having a diameter of 80 mm was used. The surface resistance of this photosensitive drum was 2.5 × 10 ¹³ Ωcm. An image was formed under the above development conditions. As a result, an excellent image having very fine line reproducibility and a high solid image density was obtained. Further, no image disturbance and toner fogging in the image area and the non-image area due to carrier adhesion were observed. Also, 10
When the endurance of image output for 10,000 sheets was performed, there was no change in the triboelectric charge amount of the toner at the initial stage, and there was no change or deterioration of the image.

Table 1 shows the results of Example 1. Table 1 also shows the results of the following Examples and Comparative Examples.

[0117]

[Table 1]

[0118]

Comparative Example 1 Using the resin-coated carrier (a) produced in Example 1 and the toner of Toner Production Example 1, an image output durability test was performed in the same manner as in Example 1. As a result, the image density changed from 1.35 to 1.45 from the initial stage to a slightly lower density range. In addition, disturbance of the image area due to carrier adhesion and toner fogging in the non-image area were observed, and reproducibility of fine lines was insufficient.

[0119]

[Comparative Example 2] In a four-necked flask, 5 parts by mass of phenol, 3
Α-F lipophilized with 7 parts by weight of 7% formalin, 400 parts by weight of ferrite core particles prepared in the same manner as in Example 1, and 2 parts by weight of γ-aminopropyltrimethoxysilane.
e ₂ O ₃ fine particles 20 mass parts, 25% ammonia water 5 mass parts, water 4
After charging 18 parts by mass, the temperature was raised to 85 ° C. over 60 minutes with stirring, and then maintained at 85 ° C. for 120 minutes to promote the curing reaction of the phenolic resin, containing α-Fe ₂ O ₃ fine particles on the carrier surface. A phenolic resin layer was formed.

Next, the content in the flask was cooled to 30 ° C., 0.5 L of water was added, the supernatant was removed, and the precipitate in the lower layer was washed with water and air-dried. Next, this was dried at 150 to 180 ° C. under reduced pressure (5 mmHg or less) to obtain a resin-coated carrier (c).

The obtained resin-coated carrier (c) had a number average particle size of 40 μm and was measured by a scanning electron microscope (FE-SEM).
As a result, it was found that the core surface was almost completely exposed only by being slightly covered with the resin. The specific resistance of the resin-coated carrier (c) was measured and found to be 3.6 × 10 ¹⁰ Ωcm.

Next, the resin-coated carrier (c) and the magenta toner described in Toner Production Example 1 were mixed at a toner concentration of 6
The developer was prepared by mixing so as to be in a mass%. At this time, the triboelectric charge of the toner was -28.8 μC / g. An image output durability test was performed using this developer in a modified full color laser copying machine CLC-500 made by Canon in the same manner as in Example 1. As a result, the image density was 1.
The density range was slightly lower from 40 to 1.45.In the halftone area, coarseness was observed from the beginning, and toner fog was observed in the white background of the image. .

[0123]

Example 2 Straight silicone resin (TSR144, manufactured by Toshiba Silicone Co., Ltd.) was diluted with toluene and the solid content of the resin was reduced.
A 5% by weight carrier resin coating solution was prepared. Next, 1000 parts by mass of the resin-coated carrier (b) obtained in Example 1 was put into a mixer having stirring blades, and 100 ml of the above-mentioned carrier-coated resin solution was poured while applying shear stress by stirring. Next, the inside of the mixer was heated to evaporate the solvent to complete the resin coating treatment. The obtained carrier particles were heat-treated at 150 ° C. for 2 hours, crushed, and classified with a 200-mesh sieve to obtain a resin-coated carrier (d). When the specific resistance of the obtained resin-coated carrier (d) was measured, it was 5.5 × 10
It was ¹⁵ Ωcm. Observation of the surface of the obtained resin-coated carrier (d) with a scanning electron microscope (FE-SEM) revealed that the carrier was uniformly coated with the resin.

The carrier was cut with a microtome to form a thin section, and the cross section of the carrier was observed with a scanning electron microscope (FE-SEM). As a result, a resin coating containing two layers of α-Fe ₂ O ₃ fine particles was observed. One more resin coating layer was observed on the layer.

An image output evaluation test was carried out in the same manner as in Example 1 using the magnetic carrier (d) and the toner of Production Example 1. As a result, similar to Example 1, the image density changed from 1.49 to 1.56 from the initial stage to 100,000 sheets, and a good image without carrier adhesion and toner fog was obtained. Also from the beginning 10
Up to 10,000 sheets, the halftone area was free of roughness and an image with excellent fine line reproducibility was obtained.

[0126]

[Comparative Example 3] Straight silicone resin (TSR144, manufactured by Toshiba Silicone Co., Ltd.) was diluted with toluene and the solid content of the resin was reduced.
A 5% by weight carrier resin coating solution was prepared. Next, 1000 parts by mass of the ferrite core particles used in Example 1 were put into a mixer having a stirring blade, and 200 ml of the above carrier coating resin solution was poured while applying a shearing stress by stirring. Next, the inside of the mixer was heated to evaporate the solvent to complete the resin coating treatment. The obtained carrier particles were heat-treated at 150 ° C. for 2 hours, crushed, and classified with a 200-mesh sieve to obtain a resin-coated carrier (e). When the specific resistance of the obtained resin-coated carrier (e) was measured, it was 7.2 × 10 ¹² Ωcm. Observation of the surface of the obtained resin-coated carrier (e) with a scanning electron microscope (FE-SEM) revealed that the resin coating was uneven and the ferrite core surface was exposed in some places.

Next, the above resin-coated carrier (e) and the magenta toner described in Toner Production Example 1 have a toner concentration of
A developer was prepared by mixing so as to be 6% by mass. At this time, the triboelectric charge of the toner was -23.9 μC / g. An image output durability test was performed using this developer in a modified full-color laser copying machine CLC-500 made by Canon in the same manner as in Example 1. As a result, the image density was in a sufficiently high range of 1.55 to 1.61 from the initial stage to 100,000 sheets, but roughness was observed in the halftone region from the beginning, and toner fogging was observed on the white background of the image. Was observed, and as the durability increased, the roughness and toner fog worsened.

[0128]

Example 3 Resin-coated carrier (d) used in Example 2
A developer was prepared in the same manner as in Example 1 using the polymerized toner of Toner Production Example 2 and. At this time, the triboelectric charge of the toner was -24.8 μC / g. An image output durability test was performed in the same manner as in Example 1. As a result, excellent halftone and fine line reproducibility were obtained from the initial stage to 100,000 sheets, and the solid image density was 1.57 at the initial stage and 1.55 even after 100,000. Even when 100,000 sheets of images were output from the beginning, toner scattering and fogging were not observed on the images.

[0129]

Comparative Example 4 Resin-Coated Carrier (c) Used in Comparative Example 2
A developer was prepared in the same manner as in Example 1 using the toner of Example 2 and the toner of Production Example 2, and an image output durability test was performed in the same manner as in Example 1. As a result, coarseness was observed in the halftone from the beginning, the reproducibility of fine lines was also insufficient, and toner fogging was observed. Also, solid images are initially 1.40, 10
An image with a slightly lighter density of 1.47 was obtained after 10,000.

[0130]

Example 4 In a three-necked flask, 5.4 parts by mass of melamine, 37
% Formalin 10.5 parts by mass, 18 parts by mass of α-Fe ₂ O ₃ fine particles lipophilized with 2 parts by mass of γ-aminopropyltrimethoxysilane, 230 parts by mass of resin-coated carrier (a), 0.35 part by mass of calcium fluoride And 200 parts by mass of water, the pH of the solution was adjusted to 8.5 with stirring, the temperature was raised to 85 ° C. in 40 minutes, and the mixture was reacted at the same temperature for 15 minutes. Next, the content was cooled to 30 ° C., 30 parts by mass of a 5% ammonium chloride solution was added, the temperature was raised to 85 ° C. in 60 minutes, and the mixture was reacted and cured at the same temperature for 90 minutes.

Next, the content in the flask was cooled to 30 ° C.
It was transferred to a beaker, washed several times with water, and air-dried. Next, this was dried at 100 to 150 ° C. under reduced pressure (5 mmHg) to perform coating with a melamine resin. Resin-coated carrier (f) coated with the obtained melamine resin
As a result of measuring the magnetic force of the carrier, the amount of the melamine resin was 1.4% by mass. Observation of the obtained resin-coated carrier (f) with a scanning electron microscope (FE-SEM) revealed that the surface was uniformly coated.

Next, a straight silicone resin (TTSR14)
4, Toshiba Silicone Co., Ltd.) was diluted with toluene to prepare a carrier resin coating solution having a resin solid content concentration of 5% by mass.
Next, 1000 parts by mass of the obtained resin-coated carrier (f) was put into a mixer having stirring blades, and 100 ml of the above-mentioned carrier-coated resin solution was poured while applying shear stress by stirring. Next, the inside of the mixer was heated to evaporate the solvent to complete the resin coating treatment.

The obtained carrier particles were heat-treated at 150 ° C. for 2 hours, crushed, and classified with a 200-mesh sieve to obtain a resin-coated carrier (g). The specific resistance of the resin-coated carrier (g) was measured and found to be 2.7 × 10 ¹⁵ Ωcm. Further, the surface of the resin-coated carrier (g) was observed with a scanning electron microscope (FE-SEM), and it was found that the carrier was uniformly coated with the resin.

The carrier was cut with a microtome to form a thin section, and the cross section of the carrier was observed with a scanning electron microscope (FE-SEM). As a result, a resin coating containing two layers of α-Fe ₂ O ₃ fine particles was obtained. One more resin coating layer was observed on the layer.

Using the resin-coated carrier (g) and the toner of Production Example 1, a developer was prepared in the same manner as in Example 1, and an image output evaluation test was performed. As a result, the image density from the initial stage to 100,000 sheets was 1.52 to 1.
57, a good image without carrier adhesion and toner fog was obtained. In addition, from the initial stage to 100,000 sheets, the halftone area was free from roughness and an image with excellent fine line reproducibility was obtained.

[0136]

Embodiment 5 A photosensitive drum made of aluminum having a diameter of 80 was used.
An OPC photosensitive member having the following five functional layers on a drum of mm was prepared.

The first layer is an undercoat layer, the second layer is a positive charge injection preventing layer, the third layer is a charge generation layer, the fourth layer is a charge transport layer, and the fifth layer is a charge injection layer from the aluminum drum side. Layer. This charge injection layer is made of a photocurable acrylic resin made of Sn.
O ₂ ultra-fine particles, and further dispersed ethylene tetrafluoride resin particles for uniform charging by increasing the contact time between the contact charging member and the photosensitive member. Specifically, antimony is doped to reduce the number-average particle diameter of the resistance to about 0.1.
70% by mass of SnO ₂ particles of 03 μm with respect to the resin, 20% by mass of ethylene tetrafluoride resin particles having a number average particle size of 0.25 μm, and 1.2% by mass of a dispersant. The surface resistance of this photosensitive drum was 5.8 × 10 ¹² Ωcm. An image endurance test was performed in the same manner as in Example 1 except that the above-mentioned photosensitive drum was used in place of the amorphous silicon drum. As a result, very excellent fine line reproducibility,
An excellent image having a high solid image density was obtained. further,
No image disturbance or toner fogging in the image area and the non-image area due to carrier adhesion was observed.

[0138]

Example 6 An image was formed and a durability test was carried out in the same manner as in Example 3 except that the photosensitive drum produced in Example 5 was used. As a result, an excellent image having a very fine line reproducibility and a high solid image density was obtained. Further, no image disturbance and toner fogging in the image area and the non-image area due to carrier adhesion were observed.

Incidentally, in the present invention, the image evaluation described in the examples was performed as follows. (1) Image density: Image density was measured by Macbeth color checker RD-12 manufactured by Macbeth equipped with SPI filter.
55 was used as a measure of the relative density of the image formed on plain paper. (2) Line reproducibility: visually evaluated with reference to the original image and the standard sample. (3) Carrier adhesion: A solid white image is formed, and the portion of the photosensitive drum between the developing section and the cleaner section is sampled by adhering a transparent adhesive tape onto a photosensitive drum of 5 cm × 5 cm. The number of attached magnetic carrier particles is counted, and the number of attached carriers per 1 cm ² is calculated. Excellent: less than 10 pieces / cm ² Good: less than 10-20 pieces / cm ² Acceptable: less than 20-50 pieces / cm ² Somewhat bad: less than 50-100 pieces / cm ² Bad: more than 100 pieces / cm ² (4) Fog: average reflectance Dr of plain paper before image output
(%) Is Densitometer TC-6M manufactured by Tokyo Denshoku Co., Ltd.
Measured by C. On the other hand, a solid white image was formed on plain paper, and the reflectance Ds (%) of the solid white image was measured. Fog (%) is calculated from the following equation.

Fog (%) = Dr (%)-Ds (%) Excellent: less than 1.0 (%) Good: less than 1.0 to 1.5 (%) Acceptable: less than 1.5 to 2.0 (%) Slightly worse: 2.0 to 3.0 (%) ) Less than bad: 3.0 (%) or more

[0141]

According to the present invention, in an image forming method using an image bearing member composed of an amorphous silicon photosensitive member having a low surface resistance or a photosensitive member having a charge injection layer, the resistance is substantially increased. Performs contact two-component AC development using a magnetic carrier that is excellent in fine line reproducibility, achieves high image quality without toner fogging and carrier adhesion, and extends the life of the image carrier and developer. can do.

[Brief description of the drawings]

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

FIG. 2 shows a developing bias waveform used in an embodiment of the present invention.

FIG. 3 is a schematic view of an apparatus for measuring a specific resistance of a carrier, a carrier core, and a metal oxide according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing sleeve (developer carrier) 2 photosensitive drum (image carrier) 3 contact charging member 4 transfer drum 5 exposure means 6 cleaner 7 transfer material 21 lower electrode 22 upper electrode 23 insulator 24 ammeter 25 voltmeter 26 constant voltage Device 27 Carrier 28 Guide ring d Sample thickness E Resistance measurement cell

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/02 101 G03G 9/10 351 15/08 501 311 352 361 (72) Inventor Yuzo Tokunaga Ota, Tokyo 3-30-2 Kumoshita Maruko F-term (reference) in Canon Inc. 2H003 BB11 CC04 2H005 BA06 BA07 BA11 BA15 CA12 CA15 CB03 CB04 EA01 EA05 FA02 2H068 DA02 DA17 2H077 AD02 AD06 DB12 DB14 EA03

Claims (12)

[Claims] 1. A charging step of applying a voltage to a charging member to charge an image carrier, and a latent image forming step of forming an electrostatic latent image on the charged image carrier by performing image exposure. And a developer carrier that carries a two-component developer containing a magnetic carrier and a toner on the surface thereof is disposed to face the image carrier, and the toner of the two-component developer is placed on the surface of the image carrier. A developing step of forming a toner image by transferring to the held electrostatic latent image; and a transfer step of transferring the toner image to a transfer material, wherein the image carrier has a surface resistance of 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ωcm, wherein the magnetic carrier has carrier core particles and a resin coating layer composed of at least two or more laminated layers thereon, wherein the carrier core particles are ferrite particles, Of the resin coating layer of the magnetic carrier The lower layer is a thermosetting resin containing metal oxide fine particles, and the upper layer is a thermosetting resin coated by a polymerization method.The magnetic carrier has a number average particle size of 5 to 100 μm, The cumulative distribution value of the number average particle diameter of 1/2 or less is 10
% Or less, and the developing step is performed by applying an alternating electric field while contacting a developer magnetic brush made of the two-component developer carried on the developer carrier with the image carrier. An image forming method comprising: 2. The magnetic carrier has a specific resistance of 1 × 10 ¹²
2. The image forming method according to claim 1, wherein the value is Ωcm or more. 3. The image forming method according to claim 1, wherein the image carrier is an amorphous silicon photoconductor. 4. The image forming method according to claim 1, wherein the image carrier is a photoconductor whose surface layer is a charge injection layer. 5. The image forming method according to claim 1, wherein in the charging step, the charging member is a contact charging member. 6. The image forming method according to claim 5, wherein the contact charging member is a magnetic brush made of magnetic particles for charging. 7. The image forming method according to claim 1, wherein the outermost layer of the resin coating layer of the magnetic carrier is a silicone resin. 8. The image according to claim 1, wherein the thermosetting resin coated by the polymerization method in the resin coating layer contains metal oxide fine particles. Forming method. 9. The metal oxide in the resin coating layer
The particles are α-Fe _TwoO_ThreeAnd / or magnetite
The method according to any one of claims 1 to 8, wherein
Image forming method. 10. The image forming method according to claim 1, wherein the thermosetting resin of the resin coating layer is a phenol resin. 11. The image forming apparatus according to claim 1, wherein the direction of rotation of the developer carrier and the direction of rotation of the image carrier are counter directions to each other at opposing portions disposed opposite to each other. The image forming method according to any one of the above. 12. The image forming method according to claim 1, wherein the toner of the two-component developer has a weight average particle diameter of 1 to 10 μm.