JPH0876479A - Binary system developer - Google Patents

Abstract

PURPOSE: To provide a developer which contain specific toner and specific carrier so as to have a satisfactory charge ability without a charge control agent, which scatters little toner and which gives an excellent image quality. CONSTITUTION: A binary system developer is composed of carrier and toner containing toner particles which in turn contain fixing resin and magnetic powder dispersed in the resin. The fixing resin is a composition containing resin having. a monomeric material and a polymeric material which contain therein anionic polar groups, respectively, the acid value of the monomeric material is lower than that of the polymeric material. The magnetic powder is contained by 0.1 to 5 weight parts with respect to 100 weight parts of the fixing resin. The carrier particles contain thermoplastic resin and high resistance magnetic powder dispersed in the resin, having a volumetric reference mean particle size of 50 to 150-μm. The thermoplastic resin is a composition containing having a cationic polar group. The high resistance magnetic powder has a specific resistance of higher than 1×10<5> Ωcm, and is contained by 60 to 90 weight parts in the carrier particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer, and more specifically, it has good transfer efficiency and can reproduce a desired density for a long time even if a charge control agent is not contained in the toner. The present invention relates to a long-life two-component developer capable of obtaining an image, which is preferably used in an electrophotographic image forming apparatus such as an electrostatic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a two-component developer is used as one of the developers for developing an electrostatic latent image on a photoconductor. This two-component developer contains a toner containing a coloring agent such as carbon black and a fixing resin, and a magnetic carrier containing iron powder, ferrite particles and the like.

During development, the toner and carrier are mixed to charge the toner to a predetermined polarity, and then the mixture is conveyed to the photoconductor in the form of a magnetic brush. The photoconductor is rubbed by this magnetic brush, and toner adheres to the electrostatic latent image on the surface of the photoconductor. A charge control agent is generally contained in the toner particles in order to make the amount of toner adhered constant and give a predetermined charge amount to the toner in order to provide a stable image. Negative charge control agents such as metal-containing complex dyes containing a metal such as chromium (eg, azo dyes) and oxycarboxylic acid metal complexes (eg, salicylic acid metal complexes) are used for negatively chargeable toners. No. 3-67268), and positively chargeable toners use oil-soluble dyes such as nigrosine and positive charge control agents such as amine-based control agents (JP-A-56-56).
106249).

The charge control agents that have been conventionally used are often compounds containing heavy metals such as chromium-containing complexes.
When using these compounds, compounds that have passed various toxicity tests and safety tests are selected from the viewpoint of environmental safety. However, even if there is no problem in safety as a compound or in the form of being contained in the toner,
It would be more desirable to avoid the use of charge control agents containing these heavy metals. Further, since the charge control agent has a higher unit price than the fixing resin and the colorant such as carbon black, which are the materials constituting the toner, it increases the unit price of the toner despite the content rate of about several percent.
Therefore, there is a demand for the development of a toner containing no charge control agent containing such a heavy metal.

Further, in the conventional toner, the toner component adheres to the particle surface of the carrier due to long-term use, so that the charged state of the particle surface of the carrier is similar to the charged state of the toner particle surface. come. As a result, there is also a drawback that toner scattering occurs and transfer efficiency decreases.

[0006]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object thereof is to:
It is an object of the present invention to provide a two-component developer in which the toner does not scatter and the image quality is excellent because the toner has good charging performance even though it does not contain any charge control agent. Another object of the present invention is to provide a two-component type developer which does not cause spent even after long-term use and, as a result, maintains good image quality and has stable transfer efficiency.

[0007]

The present invention is a two-component developer comprising a toner and a carrier; the toner comprises toner particles; the toner particles are a fixing resin, and in the resin. The fixing resin is a composition containing a resin having a low molecular weight substance having an anionic polar group and a polymer having a high molecular weight substance having an anionic polar group; and the acid value of the low molecular weight substance is high. Smaller than the acid number of the molecular body; the magnetic powder is
The toner particles are contained in the toner particles in a ratio of 0.1 to 5 parts by weight with respect to 100 parts by weight of the fixing resin; particles of the carrier are a thermoplastic resin and a high-resistivity magnetic material dispersed in the thermoplastic resin. It contains powder and its volume average particle size is 50
To 150 μm, and the thermoplastic resin is a resin composition containing a resin having a cationic polar group; and
The high resistance magnetic powder has a specific resistance of 1 × 10 ⁵ Ω · cm or more and is contained in the carrier particles in a proportion of 60 to 90% by weight;

In a preferred embodiment, the extraction liquid when the toner is extracted with methanol is 280 to 350.
has substantially no absorption peak in the nm region, and 40
The absorbance in the region of 0 to 700 nm is substantially zero.

In a preferred embodiment, the acid value of the low molecular weight substance is 3 to 15, and the acid value of the high molecular weight substance is 6 to 25. The acid value ratio of is from 1: 1.2 to 1: 8.

In a preferred embodiment, the magnetic powder is 0.5 to 3 with respect to 100 parts by weight of the fixing resin.
It is contained in a ratio of parts by weight.

In a preferred embodiment, the toner particles have a volume-based average particle diameter of 5 to 15 μm, and the toner particles have a volume-based average particle diameter of 0.05 to 1.0 μm.
m spacer particles are attached.

[0012]

The two-component developer of the present invention does not contain any charge control agent such as an azo dye or a metal complex of oxycarboxylic acid. Therefore, as will be described later, the spent due to the charge control agent is not generated, so that high-quality image copying can be performed for a long time. Since the toner in the developer contains no charge control agent, such a charge control agent, that is, a dye-based compound, is not detected from the toner by any chemical or physical means. For example, these compounds are not detected by a chemical reaction in the toner used in the developer of the present invention. Alternatively, absorption peaks due to these compounds are not detected at all in the organic solvent extract of the toner used in the developer of the present invention. For example, when the toner used in the developer of the present invention is extracted with an organic solvent, for example, methanol, the extract liquid is 280-35.
It has substantially no absorption peak in the region of 0 nm, and 40
The absorbance in the region of 0 to 700 nm is substantially zero. Here, “having substantially no absorption peak” means that no absorption peak was detected in the extract obtained by extracting 0.1 g of toner with 50 ml of methanol, or even if it was detected, the absorbance at the peak position was 0. It means less than or equal to 05. Similarly, that the absorbance is substantially zero means that the absorbance of the extract obtained by extracting 0.1 g of the toner with 50 ml of methanol is not more than 0.05.

In the two-component developer of the present invention, the instability of the charge amount due to the fact that the toner does not contain the above charge control agent is compensated by the following matters. The first is to use a resin having an anionic polar group as the fixing resin in the toner particles, and the second is to contain the magnetic powder in a predetermined ratio in the toner particles. Further, in the present invention, the fixing resin is composed of a composition containing a resin having a low molecular weight substance having an anionic polar group and a polymer having a high molecular weight substance, and the acid value in the low molecular weight substance is By setting it smaller than the price,
The charging failure of the toner can be further reduced. Further, if necessary, spacer particles having a predetermined particle diameter are attached to the surfaces of the toner particles, so that the transfer efficiency from the photoconductor onto the transfer paper is enhanced.

The particles of the carrier contained in the developer of the present invention contain a thermoplastic resin and a magnetic powder dispersed in the thermoplastic resin, so that the mixing and stirring property of the developer and the transporting property of the magnetic brush are carried out. -The characteristics of the rubbing force of the magnetic brush are improved. Further, by using a high resistance magnetic powder, carrier adhesion due to induced charges is prevented.

The above will be described in detail below.

FIG. 1 shows the absorbance curve of the methanol extract of the toner used in the developer of the present invention at 200 to 700 nm. As shown in this curve, this extract does not have any peaks attributed to each charge control agent.
That is, it has substantially no absorption peak in the region of 280 to 350 nm, and the absorbance in the region of 400 to 700 nm is substantially zero. On the other hand, the absorbance curve of the methanol extract of the toner containing the azo-type chromium metal complex salt dye as the charge control agent is 400 to 700 nm, especially 5
The toner has a peak in the range of 50 to 570 nm (FIG. 2), and the absorption curve of the methanol extract of the toner containing the salicylic acid metal complex as the charge control agent is 28.
It has a peak in the region of 0 to 350 nm (FIG. 3).

The absorption due to the charge control agent is observed in the methanol extract of the toner containing the above charge control agent because the charge control agent is present on the surface of the toner particles in a considerably high concentration. is there.

When a ferrite carrier of a conventional developer in which the chargeability of the carrier became insufficient due to the generation of spent was extracted with methanol and the absorbance at 400 to 700 nm was examined, it was attributed to the charge control agent in that region. A peak is observed. For example, FIG. 2 shows the absorbance curve of the methanol extract of the carrier when a toner containing the azo chromium complex salt dye is used for a long time and a spent occurs, the absorbance curve of which is shown in FIG.
In FIG. 4, a peak is recognized at the same position as that of the charge control agent in FIG. In the past, the spent
It was thought that the resin for fixing the toner adheres to the surface of the particles of the carrier to form a resin film, but due to the above fact, one of the main causes of the spent generation is that the toner particles of the charge control agent It was found that the carrier was transferred to the particle surface.

The inventors further conducted the following experiment to investigate the relationship between the charge control agent and the spent. First, a toner having toner particles containing an azo chromium complex salt dye at a ratio of 1.5 wt% as a charge control agent was mixed with a ferrite carrier to obtain a developer. FIG. 5 shows the relationship between the elapsed time when the operation of mixing and stirring the toner of the developer and the carrier is continued and the weight of the deposit adhered to the particle surface of the carrier by the spent. The weight of the deposits is shown in FIG. 5 as the percentage of spent relative to the total weight of the carrier having the deposits. Further, FIG. 6 shows the relationship between the elapsed time and the toner charge amount. Further, the same measurement was performed for a developer containing a toner having toner particles not containing the above charge control agent and a ferrite carrier.
The results are also shown in FIGS. 5 and 6. 5 and 6
In the above, the black circle plot shows the measured value of the toner containing the charge control agent, and the white circle plot shows the measured value of the toner not having the charge control agent. From FIGS. 5 and 6, it can be seen that the toner containing the charge control agent has a larger amount of deposits on the particle surface of the carrier due to the spent and the degree of decrease in the charge amount is larger than that of the toner containing no charge control agent.

The weight of the toner component adhering to the particle surface of the ferrite carrier was measured with a spent toner,
FIG. 7 shows a graph in which this is plotted on the abscissa (shown as the amount of spent) and the amount of the charge control agent in the toner component is plotted on the ordinate. The dotted line shows the amount of the charge control agent when it is assumed that the toner component attached by the spent is the same as the component forming the toner particles. From FIG.
A large amount of charge control agent is deposited in the early stage of using the developer,
It can be seen that the particles adhere to the particle surface of the carrier. In FIG. 7, the reason why the measured value approaches the calculated value indicated by the dotted line with the increase in the amount of spent is that this is an experimental result in a closed system without toner replenishment. If there is a replacement, the difference between the two will be further widened.

Further, in order to investigate the relationship between the components constituting the toner particles and the spent toner, the present inventors have used a ferrite carrier and a charge control agent, a fixing resin, carbon black as a colorant, and wax. The weight of the deposits on the particle surface of the carrier produced by the passage of time after mixing and stirring were measured. FIG. 8 shows the result. In FIG. 8, the white circles show the results when the test was conducted using the charge control agent, the black circles the carbon black, the squares the fixing resin, and the triangles the wax. It can be seen from FIG. 8 that the charge control agent is most likely to cause the spent to adhere to the surface of the particles of the carrier.

From the above facts, the charging failure due to the spent of the conventional two-component magnetic developer is explained as follows. First, as shown in the upper part of FIG. 9, in the initial stage of use of the developer, the carrier particles 1 are positively charged and the toner 2 is negatively charged, and the toner exists as the negative polarity toner 21. When this developer is used, the toner component containing the charge control agent as a main component in the toner particles adheres to the surface of the carrier particles 1. Since the deposit 201 formed by this spent is negatively charged, the toner having a positive charge with respect to the deposit 201, that is, the opposite polarity toner 22 is formed. This reverse polarity toner 2
Since the particles 2 are formed on the surface of the particles 1 of the carrier, toner scattering occurs and the transfer efficiency decreases.

The above results are all results using a ferrite carrier. In the case of a binder type carrier, which is a type in which magnetic powder is dispersed in a resin medium, analyzing the cause of the spent by the above extraction experiment can detect the extract from the resin medium in addition to the spent. Although it is not possible, it is considered that the same phenomenon is occurring, and it is considered that the charge control agent causes the spent even in the case of the binder type carrier.

As described above, the charge control agent is
Since it may contain a heavy metal, it is preferable not to contain it. Further, as described above, it is a main cause of spent, causing toner scattering, lowering of transfer efficiency, and the like. Therefore, the toner used in the developer of the present invention In, the charge control agent is not contained at all.

The instability of the charge amount due to not containing the charge control agent, mainly the lack of the charge amount, is due to the use of the fixing resin having an anionic polar group in the toner as described above. Will be supplemented. Since the fixing resin itself is provided with a negative charge by the anionic polar group, the insufficient charge amount of the toner particles is compensated. Since this polar group exists by binding to the skeleton of the resin itself, it does not migrate to the particle surface of the carrier like a charge control agent and cause spent. However, conversely, the chargeability near the surface of the toner particles is
Since it is not so large, the coupling between the toner particles and the carrier particles by the Coulomb force in the magnetic brush at the time of development is insufficient. Therefore, when high-speed copying is performed, the bondability between the carrier particles and the particles is weak, and the toner scattering is not sufficiently suppressed. Contamination of the inside of the copying machine due to toner scattering,
There is a drawback that so-called fog occurs in the image of the copy.

In the present invention, as the second requirement as described above, the magnetic powder is contained in the toner particles in a predetermined ratio, that is, 0.1 to 5 parts by weight relative to 100 parts by weight of the fixing resin. Incorporation is employed to make up for the shortage of the charge amount of the toner particles. Since the magnetic powder is contained in the toner particles, a magnetic attractive force is generated between the toner particles and the carrier particles. In this way, in addition to the Coulomb force between the toner particles and the particles of the carrier, a magnetic attraction force is generated, so that toner scattering is prevented. Generally, the smaller the amount of charge per toner particle,
Since the number of toner particles attached to a given electrostatic latent image is increased, the apparent development sensitivity is increased.

The content of the magnetic powder in the toner particles is
As described above, the amount is 0.1 to 5 parts by weight per fixing resin. When the content of the magnetic powder is less than 0.1 part by weight, the charge amount of the toner is insufficient as described above, the particles are not sufficiently bonded to the carrier particles, and the toner is easily scattered. That is, there is a drawback that so-called fog occurs in the image of the copy. When the content of the magnetic powder exceeds 5 parts by weight, the binding force between the carrier particles and the toner particles becomes too large, so that the toner does not adhere sufficiently to the electrostatic latent image,
As a result, the image density becomes low.

To date, attempts have been made to incorporate (internally add) magnetic powder into toner particles for the purpose of improving the resolution of images. For example, JP-A-56-1062
No. 49 discloses toner particles containing 10% by weight of ferrite, and JP-A No. 59-162563 discloses toner particles containing 5 to 35% by weight of magnetic fine powder. . However, in either case, the image density of the obtained copy is low because the amount of the magnetic powder is excessive. Japanese Patent Application Laid-Open No. 3-67268 discloses a toner to which magnetic powder is externally added at a ratio of 0.05 to 2% by weight. However, since the magnetic powder is not internally added to the toner particles, it tends to be nonuniformly attached to the surface of the toner particles, and the magnetic attraction between the toner particles and the carrier particles is insufficient. In any of the above-mentioned conventional techniques, since the toner contains the charge control agent, problems such as spent may occur.

Further, in the present invention, the fixing resin is composed of a composition containing a resin having a low molecular weight substance and a high molecular weight substance each having an anionic polar group, and the acid value in the low molecular weight substance is high. By setting the acid value smaller than the acid value in the body, the charging failure of the toner can be further reduced. The detailed reason for this is as follows.

Even in the toner containing no charge control agent, the low molecular weight substance in the fixing resin having the low molecular weight substance and the high molecular weight substance selectively adheres to the particle surface of the carrier based on the analysis result of the deteriorated carrier. It turned out that there are cases. When the low molecular weight substance in the resin has a relatively large amount of acid value component (crosslinking component) which becomes an anionic polar group, the low molecular weight substance adheres to the particle surface of the carrier, which causes friction with the toner. There is a possibility that toner of opposite polarity may be generated by the charging, resulting in defective charging of the toner.

For example, considering the charging series of styrene-acrylic resin, the acrylic acid component tends to be negatively charged. This acrylic acid component is generally used as a fixing resin material for toner, and is included in the low molecular weight material of the fixing resin. When a relatively soft low-molecular substance adheres to the particle surface of the carrier, if many of the adhered components have a strong negative charge tendency, the toner charged by friction with it is oppositely charged (charged to the positive side). It is considered that the charging becomes easier and a charging failure occurs.

For this reason, the acid value of the low molecular weight substance is set lower than that of the high molecular weight substance. In other words, by containing a large amount of non-crosslinking components (groups that are not hydrogen or free acid) in low-molecular weight substances, it is possible to reduce the generation of reverse polarity toner, prevent toner charging defects, and improve durability. can do.

In the present invention, in order to further improve the transfer efficiency of the toner image, spacer particles having a particle diameter of 0.05 to 1.0 μm are preferably attached to the surface of the toner particles. The spacer particles can act as a fluidity improver for the toner particles and form a gap between the photoreceptor and the toner particles when attached to the electrostatic latent image on the photoreceptor. Therefore, even if the charge amount of the toner becomes high due to copying for a long time, the toner can be easily transferred from the surface of the photoconductor, so that the transfer efficiency becomes high. When the spacer particles are the same magnetic powder particles as those internally added to the toner particles, the binding ability between the toner particles and the particles of the carrier becomes higher, and the toner scattering and fog can be further reduced.

Fine particles having a particle diameter of about 0.015 μm have been used as an external additive as a conventional fluidity improver for toner. Such particles form a sufficient gap between the photoreceptor and the toner particles. Therefore, it does not function as the spacer particles for the above purpose.

The particles of the carrier used in the present invention have a structure in which a high resistance magnetic powder is dispersed in a thermoplastic resin, and have a relatively large volume-based average particle diameter of 50 to 150 μm. Since the magnetic powder is dispersed in the particles of the carrier having a relatively large particle size, the magnetic force per particle of the carrier is large, which makes it possible to compensate for the shortage of magnetic force, which is a drawback of conventional carriers of this type. Is. Since the contained magnetic powder has a specific resistance of 1 × 10 ⁵ Ω · cm or more, there is little charge leakage when carrier particles are charged. Therefore, the binding force between the toner particles and the particles of the carrier is strong, and there is no drawback that toner scattering occurs. Since the particles of this carrier are basically a type in which magnetic powder is dispersed in resin, the magnetic force is a little weaker than that of carrier particles made of ordinary ferrite particles, etc. Only. Therefore, the rubbing property with respect to the surface of the photoconductor is good, the surface of the photoconductor is scratched, and the toner image formed on the photoconductor is less disturbed, and so-called white stripes are generated in the image of the obtained copy. Absent. Since the particles of the carrier have a predetermined particle size and do not contain fine particles, the apparent density is low and the particles of the carrier do not aggregate with each other. Therefore, the stirring force required for mixing and stirring the carrier and the toner can be small, and the transportability of the magnetic brush is good.

In the present invention, the chargeability is imparted to the carrier by incorporating the resin having a cationic polar group into the particles of the carrier. As a result, even when this carrier is combined with a toner containing no charge control agent, the chargeability of the toner is significantly improved. As a result, the chargeability of the toner becomes stable. Further, since the conventional charge control agent is not contained, the generation of spent on the particles of the carrier is effectively prevented, so that the life of the developer can be extended.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The preferable modes of the present invention will be described below. Hereinafter, in the present specification, "lower alkyl group"
Is an alkyl group having 1 to 5 carbon atoms.

(Fixing Resin) The fixing resin contained in the toner particles of the two-component developer of the present invention is a composition containing a resin having a low molecular weight substance and a high molecular weight substance each having an anionic polar group. The acid value of the low molecular weight substance is smaller than that of the high molecular weight substance. Here, the high molecular weight means a resin having a molecular weight of 100,000 or more, and the low molecular weight means a resin.
A resin having a molecular weight of less than 100,000.

The molecular weight peak of the low molecular weight substance is 4,000 to 3
10,000 is preferable. The low molecular weight molecular weight peak is 4,
If it is less than 000, improvement in spent resistance cannot be expected, and durability tends to decrease. If it exceeds 30,000, the pulverizability tends to decrease.

The weight average molecular weight of the resin is 70,000-2.
0,000 is preferable. If it is less than 70,000, the obtained toner is over-pulverized, so that the toner particles are easily broken, and if it exceeds 200,000, the pulverizability of the toner is likely to be deteriorated.

The acid value of the low molecular weight substance is set to be smaller than that of the high molecular weight substance, and particularly, the acid value of the low molecular weight substance is 3 to.
15 is preferable, and the acid value of the polymer is preferably 6 to 25. The ratio of the acid value of the polymer to the acid value of the low molecule is preferably 1: 1.2 to 1: 8. When the acid value of the low molecular weight substance exceeds the above range, and when the ratio of the above acid values is below the above range, poor charging of the toner is likely to occur.

In order to obtain a resin having a low molecular weight substance and a high molecular weight substance, a low molecular weight polymer is prepared as described below,
Then, a monomer for a polymer may be added to this and polymerized, or the separately prepared low-molecular substance and the polymer may be mixed.

The resin used as the fixing resin is preferably a copolymer of a monomer having an anionic polar group and another monomer. For example, it may be a random copolymer, a block copolymer or a graft copolymer of a monomer having an anionic group and another monomer.

Examples of the monomer having an anionic polar group include a monomer having a carboxylic acid group, a sulfonic acid group or a phosphonic acid group, and a monomer having a carboxylic acid group is particularly preferable. As the monomer having a carboxylic acid group, an ethylenically unsaturated carboxylic acid is used, which includes acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, etc., and carboxylic acid such as maleic anhydride. Monomers capable of forming groups or lower alkyl half esters of dicarboxylic acids such as maleic acid and fumaric acid can also be used. Examples of the monomer having a sulfonic acid group include styrenesulfonic acid, 2-acrylamido-
2-methyl propane sulfonic acid etc. are mentioned. Examples of the monomer having a phosphonic acid group include 2-acid phosphoxypropyl methacrylate, 2-acid phosphoxyethyl methacrylate, and 3-chloro-2-acid phosphoxypropyl methacrylate.

These anionic polar group-containing monomers are
It may be a free acid, an alkali metal such as sodium or potassium, an alkaline earth metal such as calcium or magnesium, or a salt such as zinc.

The above-mentioned monomer having an anionic polar group and the other monomer to be polymerized as necessary are selected so that the resulting polymer has the fixability and chargeability required for the toner. , A combination of one or more monomers having an ethylenically unsaturated bond is used. Examples of such monomers include acrylic ester monomers, monovinyl aromatic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers. and so on.

Acrylic ester monomers are represented by the following general formula (I):

[0048]

Embedded image

Here, R ¹ is a hydrogen atom or a lower alkyl group, and R ² is a hydrocarbon group having 11 or less carbon atoms or a hydroxyalkyl group having 11 or less carbon atoms.

Examples of such a monomer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate,
Phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, β-
Examples thereof include ethyl hydroxyacrylate, γ-hydroxyacrylate propyl, δ-hydroxyacrylate and β-hydroxymethacrylate.

Monovinyl aromatic monomers are represented by the following general formula (II):

[0052]

Embedded image

Here, R ³ is a hydrogen atom, a lower alkyl group or a halogen atom, R ⁴ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group or the like, and Φ is a phenylene group. Is.

Examples of such a monomer include styrene and α
-Methylstyrene, vinyltoluene, α-chlorostyrene, o-, m-, or p-chlorostyrene, p-ethylstyrene and the like.

The vinyl ester monomer is represented by the following general formula (III):

[0056]

[Chemical 3]

Here, R ⁵ is a hydrogen atom or a lower alkyl group.

As such a monomer, vinyl formate,
Examples include vinyl acetate and vinyl propionate.

The vinyl ether type monomer is represented by the following general formula (IV):

[0060]

[Chemical 4]

Here, R ⁶ is a monovalent hydrocarbon group having 11 or less carbon atoms.

Examples of such a monomer include vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether and vinyl cyclohexyl ether.

The diolefin monomer is represented by the following general formula (V):

[0064]

[Chemical 5]

Here, R ⁷ , R ⁸ and R ⁹ are each independently a hydrogen atom, a lower alkyl group or a halogen atom.

As such a monomer, butadiene,
Examples include isoprene and chloroprene.

The mono-olefinic monomer is represented by the following general formula (VI):

[0068]

[Chemical 6]

Here, R ¹⁰ and R ¹¹ are each independently a hydrogen atom or a lower alkyl group.

Examples of such a monomer include ethylene, propylene, isobutylene, butene-1, pentene-1,
4-methylpentene-1 and the like.

Specific examples of the resin having an anionic polar group, which is a (co) polymer obtained by polymerizing the above monomers, include styrene-acrylic acid copolymer, styrene-maleic acid copolymer, and ionomer. Resin etc. further,
A polyester resin having an anionic polar group can be used.

When the anionic polar group is present in the form of a free acid, such a resin has an anionic polar group in a ratio such that the acid value is 2 to 30, preferably 5 to 15. Is desirable. When part or all of the anionic polar group is neutralized, it is preferable to have the anionic polar group in such a proportion that it has the above-mentioned acid value when it exists in the form of a free acid. When the acid value of the resin, that is, the concentration of the anionic polar group, is lower than the above range, the chargeability of the toner is insufficient, and when it is higher than the above range, the toner has hygroscopicity, which is preferable. Absent.

A suitable fixing resin contains at least one kind of the above-mentioned monomer having an anionic polar group and the acrylic monomer of the formula (I) as an essential component, and if necessary, the formula Copolymers containing the monomers of formulas (II) to (VI) as optional components are used. Each of the above monomers may be used alone or in combination of two or more in order to prepare the above resin.

As the fixing resin used in the present invention, a resin composition containing the above resin is used.
In addition to the above resin, a polymer having no anionic polar group may be contained. In that case, the content ratio of the anionic polar group in the entire composition is preferably within the above range.

(Method for Producing Resin Used for Fixing Resin) The resin having a low molecular weight substance and a high molecular weight substance used in the present invention can be produced as follows.

The solvent for dissolving both the monomer and the resin (for example, toluene, xylene, etc.) is mixed with the monomer for low molecular weight substance and the polymerization initiator and stirred. This mixed solution was put into a reaction kettle and stirred well with a stirring blade,
Polymerization is performed at 0 to 250 ° C. for 3 to 10 hours, and after degassing and drying of the solution, a low molecular weight polymer is obtained. Next, the monomer for polymer, the polymer of low molecular weight obtained above and the polymerization initiator are mixed and stirred in a solvent capable of dissolving both the monomer and the resin. This mixed solution is put into a reaction kettle and polymerized at 60 to 200 ° C. for 5 to 24 hours while stirring well with a stirring blade. After that, the solution is degassed and dried, and then a polymer having a low molecular weight substance and a high molecular weight substance is obtained. obtain.

(Magnetic Powder) As the magnetic powder contained (internally added) in the toner particles, any of the magnetic powders conventionally used for a one-component magnetic toner can be used. Examples of the material of the magnetic powder include ferrosoferric oxide (F
e ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₂ O ₄ ), iron oxide yttrim (Y ₃ Fe)
₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuFe ₂
O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), iron nickel oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFe)
O ₃ ), iron oxide barium (BaFe ₁₂ O ₁₉ ), iron oxide magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnF
e ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron (F
e), cobalt (Co), nickel (Ni), etc. may be used. A particularly preferred magnetic powder is finely particulate iron trioxide (magnetite). Suitable magnetite has a regular octahedron shape and a particle size of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like. The particle size of the magnetic powder contained in the toner particles is generally 1.0 μm or less, preferably 0.05 to 1.0 μm.

The content of the magnetic powder in the toner particles is
0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the fixing resin.
3 parts by weight. If the amount of the magnetic powder is too small, as described above, toner is scattered during development, resulting in insufficient image density and insufficient fixing effect.

(Compounding Agent in Toner Particles) The toner particles are
As described above, the fixing resin and the magnetic powder are contained as essential components, and if necessary, a compounding agent that can be usually compounded in the toner can be contained.

Examples of the compounding agent include a colorant and a release agent.

As the colorant, for example, the following pigments can be used.

Black pigments Carbon black, acetylene black, lamp black, aniline black.

Body pigments Barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white.

The above-mentioned pigment is contained in the toner particles in an amount of usually 2 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the fixing resin.

As the release agent, various waxes and low molecular weight olefin resins are used. As the olefin resin, polypropylene, polyethylene, propylene-ethylene copolymer and the like can be used, but polypropylene is particularly preferable.

(Preparation of Toner) The toner particles used in the two-component developer of the present invention can be prepared by a general method for producing toner particles, such as a pulverizing and classifying method, a melt granulating method, a spray granulating method and It can be produced by a polymerization method, and is usually produced by a pulverizing and classifying method.

For example, the components for forming the toner particles are premixed with a mixer such as a Henschel mixer, then kneaded with a kneading device such as a twin-screw extruder, cooled, and then pulverized. The toner particles are classified to obtain toner particles. The toner particles preferably have a volume-based average particle diameter (median diameter by Coulter counter) of 5 to 15 μm, particularly 7 to 12 μm.

If necessary, a fluidity improving agent such as hydrophobic vapor phase silica particles may be attached to the surface of the toner particles as an external additive to improve the fluidity of the toner. The particle size of the fluidity improving agent such as silica particles is usually about 0.015 μm in the primary particle size, and the particle size per unit weight of the toner, that is, the total weight of the toner particles and the external additive is 0.1.
It is externally added in an amount of 1 to 2.0% by weight.

Further, in the present invention, preferably, spacer particles having a particle size larger than that of the fluidity improver particles are externally added. As the spacer particles, 0.05 to
Either organic or inorganic inert particles of 1.0 μm, preferably 0.07 to 0.5 μm can be used. Materials for such inert particles include silica, alumina,
Examples thereof include titanium oxide, magnesium carbonate, acrylic resin, styrene resin, magnetic materials and the like. The spacer particles can function as a fluidity improver and also have a function of enhancing transfer efficiency as described above. As the spacer particles, it is generally preferable to use the same magnetic powder as that contained in the toner particles, particularly fine particulate iron trioxide tetraoxide (magnetite) particles. The use of magnetic powder particles as the spacer particles effectively acts on the toner scattering as described above. The spacer particles are 10% by weight or less based on the total weight of the toner, preferably 0.1-10.
%, More preferably 0.1 to 5% by weight. If it is excessive, the density of the copied image will be insufficient.
When magnetic powder is used as the spacer particles, the total amount of the magnetic powder and the magnetic powder contained in the toner particles is preferably 10 parts by weight or less based on 100 parts by weight of the fixing resin. If it is excessive, the image density may be low.

In order to externally add the fluidity improver and the spacer particles to the toner particles, for example, the fluidity improver and the spacer particles are sufficiently mixed, and this mixture is added to the toner particles and sufficiently crushed. Is good. As a result, the spacer particles adhere to the surface of the toner particles. Here, the term "adhesion" refers to either the state of being carried in contact with the surface of a particle or the state of being fixed in a state of being partially driven from the surface of a particle. In this way, the toner used in the developer of the present invention is obtained.

(Carrier Particles) The thermoplastic resin contained in the carrier particles used in the developer of the present invention is a composition containing a resin having a cationic polar group, and is used as a dispersion medium for the high resistance magnetic powder. To be done. Such a resin is obtained by polymerizing a monomer having a cationic polar group, and the obtained resin may be a homopolymer or a copolymer.

The thermoplastic resin is preferably a copolymer of a monomer having a cationic polar group and another monomer (a monomer having no cationic polar group). For example,
It may be a random copolymer, a block copolymer or a graft polymer of a monomer having a cationic polar group and another monomer.

As the monomer having a cationic polar group, there is a monomer having a basic nitrogen-containing group, and the basic nitrogen-containing group is a primary, secondary or tertiary amino group, There are quaternary ammonium group, amide group, imino group, imide group, hydrazino group, guanidino group, amidino group and the like. Monomers having amino groups or quaternary ammonium groups are particularly suitable.

Examples of the above-mentioned monomers include basic nitrogen-containing acrylic monomers and basic nitrogen-containing vinyl monomers. Further, a polymerization initiator having a cationic polar group is selected as a polymerization initiator when (co) polymerizing a monomer having a cationic polar group and / or another monomer to synthesize a resin. It is also possible to introduce a polar polar group into the resin.

The chlorinated nitrogen-containing acrylic monomer is represented by the following general formula (VII):

[0096]

[Chemical 7]

Where R¹²Is a hydrogen atom or a methyl group
Yes, R¹³And R¹⁴Each independently having 2 to 6 carbon atoms
R is a alkylene group, R¹⁵And R¹⁶Are each independently hydrogen
An atom or an alkyl group having 1 to 12 carbon atoms, X is an acid
Elementary atom or = NR^{twenty three}(R ^{twenty three}Is a hydrogen atom or carbon
An alkyl group of the numbers 1 to 12, and p is 0 or 1
Is).

Quaternary ammonium salts of the above compound (VII) can also be used.

Examples of such a monomer include the following compounds: dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, dibutylaminoethyl. Methacrylate, dimethylaminopropyl methacrylamide, N, N-dimethylaminoethyl-N'-aminoethyl methacrylate, 3-acrylamido-3,3-dimethylpropyldimethylamine, and quaternary ammonium salts thereof.

The basic nitrogen-containing vinyl monomer includes the following compounds: diallyldimethylammonium chloride, vinyltrimethylammonium chloride, N-.
Vinylcarbazole, 2-vinylimidazole, N-vinylpyrrole, N-vinylindole, N-vinylpyrrolidone, vinylpyridinium salt.

Examples of the polymerization initiator having a cationic polar group include azoamidine or azoamide compounds, which are represented by the following general formula (VIII): azoamidine or azoamide compounds:

[0102]

Embedded image

Here, R ¹⁷ and R ¹⁸ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group (having 1 to 1 carbon atoms).
2) or an alkenyl group (having 2 to 10 carbon atoms), or a substituted or unsubstituted aryl group (having 6 to 14 carbon atoms), and R ¹⁹ or R ²⁰ are each independently a hydrogen atom, or
A substituted or unsubstituted alkyl group (having 1 to 12 carbon atoms), Y ¹ is an oxygen atom or ═N—R ²¹ (R ²¹ is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms), and Y ¹ Is =
In the case of N—R ²¹ , R ²¹ and R ¹⁷ may be linked to each other to form a substituted or unsubstituted alkylene group, Y ² is an oxygen atom or ═N—R ²² (R ²² is a hydrogen atom. Or carbon number 1
An 12 alkyl group), when Y ² is = N-R ²² is coupled and the R ²² and R ^18, may form a substituted or unsubstituted alkylene group.

Examples of such a monomer include the following compounds: 2,2'-azobis (2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2'-azobis {N- (4 -Chlorophenyl) -2-methyl} propionamidine) dihydrochloride, 2,2'-azobis {N-
(4-Hydroxyphenyl) -2-methyl} propionamidine) dihydrochloride, 2,2′-azobis {N- (4-
Aminophenyl) -2-methyl} propionamidine)
Dihydrochloride, 2,2′-azobis {2-methyl-N- (phenylmethyl) propionamidine} dihydrochloride, 2,
2'-azobis (2-methyl-N-propenylpropionamidine) dihydrochloride, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 2,2'-azobis {N- (2-hydroxyethyl) ) -2-Methyl} propionamidine) dihydrochloride, 2,2′-azobis {2-
(5-Methyl-2-imidazolin-2-yl) propane} dihydrochloride, 2,2′-azobis {2- (2-imidazolin-2-yl) propane} dihydrochloride, 2,2′-azobis { 2- (4,5,6,7-tetrahydro-1H-
1,3-diazepin-2-yl) propane} dihydrochloride,
2,2'-azobis {2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane} dihydrochloride, 2,
2'-azobis {2- (5-hydroxy-3,4,5,5
6-tetrahydropyrimidin-2-yl) propane} 2
Hydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis {2- (2-imidazoline- 2-yl) propane}, 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide},
2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide},
2,2'-azobis {2-methyl-N- [2-hydroxyethyl] propionamide}, 2,2'-azobis {2-methylpropionamide} dihydrate.

The above-mentioned monomer having a cationic polar group and the other monomer to be polymerized as required are selected so that the resulting polymer has the durability and chargeability required for the carrier. , A combination of one or more monomers having an ethylenically unsaturated bond is used. As such a monomer, the same acrylic ester-based monomer, monovinyl aromatic-based monomer, vinyl ester-based monomer, vinyl ether-based monomer that can be used for the preparation of the fixing resin, Any of diolefin-based monomers, mono-olefin-based monomers and the like can be used. Each of the above monomers may be used alone or in combination of two or more in order to prepare a resin having a cationic polar group. Specific examples of the resin having a cationic polar group include a styrene-acrylic copolymer having an amino group and a styrene-acrylic copolymer having an amide group.

The thermoplastic resin having a cationic polar group obtained by (co) polymerization of the above-mentioned monomers is
The cationic polar group is contained in g in an amount of 2 to 50 mmol, preferably 10 to 30 mmol.

When the concentration of the above cationic polar group is lower than the above range, the chargeability of the toner is insufficient. On the contrary, when the concentration is higher than the above range, the carrier has hygroscopicity and the toner is sufficiently charged. Performance cannot be added. Furthermore, the particles of the carrier easily aggregate.

The carrier resin used in the present invention includes
A resin composition containing the above resin is used, and in this composition, in addition to the above resin, a polymer having no cationic polar group may be contained. In that case, the content ratio of the cationic polar group in the entire composition is preferably in the above range.

(High Resistance Magnetic Powder) As the high resistance magnetic powder contained in the carrier particles, any of the magnetic powders used in the above toner can be used, but the specific resistance thereof is 1 × 10 ⁵ Ω · It should be at least cm. The specific resistance is preferably 1 × 10 ⁶ to 10 ⁷ Ω · cm
High resistance magnetic powders of

A preferred material for the high resistance magnetic powder is ferrite, and since ferrite usually has a specific resistance within the above range, it should be used without any special treatment after being crushed and classified as described later. Is possible. If, for example, ferrosoferric oxide (magnetite) is used as the material of the high resistance magnetic powder, its specific resistance is 10 ³ Ω · cm.
The specific resistance is adjusted to the above range by using, for example, surface oxidization treatment after grinding, removal of contaminant ions, and the like. The magnetic powder can be surface-treated with a silane coupling agent, a titanium-based coupling agent, or the like as long as the specific resistance is within the above range, whereby the dispersibility in the resin can be improved. The volume-based average particle diameter of the high resistance magnetic powder contained in the carrier particles is generally 2.0 μm or less, preferably 0.05 to 1.0 μm. If the particle size is larger than this range, it may be difficult to adjust the particle size of the carrier particles containing such magnetic powder to the above-mentioned preferred range.

(Preparation of Carrier) The particles of the carrier used in the two-component developer of the present invention are obtained by uniformly kneading the above-mentioned thermoplastic resin and magnetic powder under heating, pulverizing and classifying to remove fine powder. Is prepared. The high resistance magnetic powder is 60 to 90% by weight based on the weight of the entire carrier,
It is preferably kneaded in a proportion of 70 to 85% by weight. The particles of the obtained carrier generally have a volume-based average particle size of 5
Range of 0 to 150 μm, preferably 70 to 120 μm
It is manufactured by adjusting so as to fall within the range. Since the granular magnetic carrier thus obtained has a low density and a magnetic force of the magnetic brush is small, the mixing and stirring property and the transportability of the magnetic brush are good, and the magnetic brush slides on the photoconductor during development. The rubbing force is also eased, there are few restrictions on the apparatus, and it is extremely advantageous in obtaining an image of good quality. Further, there is almost no aggregation of particles of the magnetic carrier or adhesion to the surface of the photoconductor.

(Preparation of Developer) The two-component developer of the present invention is prepared by mixing the above toner and the above carrier. The mixing ratio of carrier and toner is generally 98: 2 to
A weight ratio of 90:10, particularly a weight ratio of 97: 3 to 92: 8 is preferable.

Copying can be carried out by a general electrostatographic copying method using the developer of the present invention. For example, after uniformly charging the photoconductive layer on the photoreceptor, imagewise exposure is performed to form an electrostatic latent image, and then a magnetic brush of a two-component magnetic developer is brought into contact with the photoreceptor to form the electrostatic latent image. Can be easily developed. The toner image formed by the development is transferred onto a transfer paper to form a transfer image, and the transfer image is fused and pressure-bonded with a heat roll to fix the image.

[0114]

EXAMPLES The present invention will be described with reference to examples.

(Example 1) A. Preparation of Fixing Resin 3 parts by weight of methacrylic acid, 17 parts by weight of butyl acrylate, 80 parts by weight of styrene, and a polymerization initiator were mixed in a soluble solvent and stirred. The obtained mixed solution was put into a reaction kettle and sufficiently stirred with stirring blades to carry out polymerization at 160 ° C./6 hours, and then the solution was degassed and dried to obtain a low molecular weight polymer.

Next, 10 parts by weight of methacrylic acid, 20 parts by weight of butyl acrylate, 70 parts by weight of styrene, a polymerization initiator, a soluble solvent and the low molecular weight polymer 10 obtained above.
0 parts by weight were mixed and stirred. The obtained mixed solution was put into a reaction kettle and polymerized at 90 ° C./17 hours while stirring well with a stirring blade, and then the solution was degassed and dried to obtain a polymer having a low molecular weight substance and a high molecular weight substance. .

The acid value ratio of the low molecular weight material and the high molecular weight material in the obtained resin (acid value of the high molecular weight material / acid value of the low molecular weight material) was 15 /
It was 5.

The acid value is measured by dissolving the obtained toner in a solvent (for example, a mixed solvent of methanol and THF). Next, after removing carbon black, wax and the like with a centrifuge, low molecular weight substances and high molecular weight substances were separated and the acid value of each was measured.

B. Preparation of Toner (Composition of Toner Particles) Fixing Resin: Resin Obtained in Section A 100 Parts by Weight Colorant: Carbon Black 10 Parts by Weight Magnetic Powder: Magnetite 2 Parts by Weight The above components are melted by a twin-screw extruder. After kneading, the kneaded material was pulverized with a jet mill and classified with an air classifier to obtain toner particles having an average particle size of 10.0 μm.

Hydrophobic silica fine particles having an average particle diameter of 0.015 μm are added to the toner particles at a ratio of 0.3 parts by weight to 100 parts by weight of the toner particles, and the average particle diameter is 0. Alumina fine particles of 0.3 μm were added (externally added) at a ratio of 0.6 parts by weight to 100 parts by weight of the toner particles, and mixed by a Henschel mixer for 2 minutes,
Toner was obtained.

C. Carrier preparation

[0122]

[Table 1]

The components shown in Table 1 were melt-kneaded by a twin-screw extruder, and then the kneaded product was crushed by a jet mill and subjected to wind and sieving to obtain carrier particles having an average particle size of 80.5 μm.

D. Preparation of Developer The above toner and carrier were uniformly mixed to obtain a two-component developer having a toner concentration of 5% by weight.

(Comparative Example 1) As a magnetic powder, a specific resistance of 7.
A developer was obtained in the same manner as in Example 1 except that 5 × 10 ³ Ω · cm magnetite was used.

Comparative Example 2 A styrene-acrylic copolymer having no amino group in the resin (a copolymer of styrene and butyl methacrylate at a weight ratio of 70:30) was used as the resin. A developer was obtained in the same manner as in Example 1.

[Evaluation of Developer] The developers of Examples and Comparative Examples were evaluated for the following items. What was used for the test was an electronic copying machine (trade name "DC-468" manufactured by Sanda Kogyo Co., Ltd.
5)) modified machine (a modified copying machine for easily sampling the evaluation sample).

(A) Transfer Efficiency The amount of toner in the toner hopper before the start of copying and the amount of toner in the toner hopper after copying a predetermined number of sheets were measured, and the toner consumption amount was calculated from the difference. On the other hand, the amount of toner collected in the cleaning process during the copying of a predetermined number of sheets was measured and used as the toner recovery amount. From these values,
The transfer efficiency of the toner was calculated by the following formula (i). The original used for copying here is a character original having a black area ratio of 8%. This evaluation was carried out in order to carry out each evaluation test under item (b).

[0129]

[Equation 1]

(B) Image Density (ID) Copying is performed using a character original having an area ratio of black portion of 8%,
Copying was continued until the transfer efficiency was less than 70%. The density of the black solid portion in the copied image was measured every 5,000 sheets using a reflection densitometer (model number "TC-6D" manufactured by Tokyo Denshoku Co., Ltd.), and the average value was taken as the image density (ID). . Here, the document used for sampling every 5,000 sheets is a document in which the area ratio of the black portion including the black solid portion is 15%. Table 2 shows the evaluation results.

(C) Fog Density (FD) Copying was performed using a character original having an area ratio of black portion of 8%.
Copying was continued until the transfer efficiency was less than 70%. The density of the non-image area in the copied image was measured every 5,000 sheets using a reflection densitometer (model number "TC-6D" manufactured by Tokyo Denshoku Co., Ltd.). The difference between the measured value and the value of the reflection density obtained by measuring the paper (base paper) before copying with a reflection densitometer was calculated, and the maximum value was defined as the fog density (FD). Here, the document used for sampling on 5,000 sheets is a document in which the area ratio of black portions including black solid portions is 15%. Table 2 shows the evaluation results.

(D) Resolution Copying is performed using a character original having an area ratio of black area of 8%.
At the time of copying 50,000 sheets (at that time when the transfer efficiency has become less than 70%), the prescribed chart original (an original using a plurality of patterns in which a predetermined number of parallel straight lines are drawn per 1 mm) Was copied, and the copied image was visually judged. Table 2 shows the evaluation results.

(E) Toner Scattering Copying is performed using a character original having an area ratio of the black portion of 8%.
Copying was continued until the transfer efficiency was less than 70%. At this time, the toner scattering state in the copying machine was visually observed and evaluated according to the following criteria. ◯: No toner scatter x: Toner scatter is shown in Table 2.

(F) Carrier Adhesion Carrier adhesion was evaluated by visually observing the number of carrier particles adhering to one image of a mesh of 25 mm square and 0.5 mm intervals, and was less than 1 (○),
The evaluation was made in three grades of 1 to 3 (Δ) and 3 or more (x).
Table 2 shows the evaluation results.

(G) Durability The toner transfer efficiency was calculated from the toner consumption amount after copying 10,000 sheets and the collected toner amount. The durability was defined as the number of sheets when the transfer efficiency became less than 70% for the first time.
Table 2 shows the evaluation results.

[0136]

[Table 2]

[Consideration of Evaluation Results] The developer obtained in Example 1 had durability of 120,000 sheets without toner scattering and carrier adhesion until the end of copying. On the other hand, the developer of Comparative Example 1 using the carrier made of magnetite having a specific resistance of 7.5 × 10 ³ Ω · cm,
Adhesion of carriers was recognized by the induced charge. The developer of Comparative Example 2 using a resin having no amino group caused toner scattering due to insufficient charging ability on the carrier side.

[0138]

According to the present invention, there is provided a two-component developer containing no charge control agent, which is a main cause of spent when copying. The toner particles of the toner contained in this developer contain a fixing resin having an anionic polar group, and the toner particles contain magnetic powder at a predetermined ratio. Further according to the invention,
The acid value of the low molecular weight substance constituting the resin is set to be lower than that of the high molecular weight substance, and a large amount of the non-crosslinking component is contained in the low molecular weight substance. As a result, it is possible to reduce the adhesion of low molecular weight substances to the carrier and prevent the generation of toner of the opposite polarity, and it is possible to further improve the durability. The particles of the carrier contained in this developer have a structure in which a high resistance magnetic powder is dispersed in a thermoplastic resin and have a relatively large particle diameter. If necessary, spacer particles having a predetermined particle size are attached to the surface of the toner particles of the developer. The toner and the carrier of the developer of the present invention have sufficient chargeability, and the toner particles and the carrier particles are also sufficiently bonded. Therefore, no spent is generated during copying and toner is not scattered. The force required for mixing and stirring the developer is small, the transportability of the magnetic brush is excellent, and the rubbing property with respect to the photoconductor is also eased. There is almost no aggregation of particles of the magnetic carrier or adhesion to the surface of the photoconductor. Further, the transfer efficiency is sufficient, the heat fixing property is excellent, and a copy image having a required density can be stably obtained for a long time. Such a two-component developer is preferably used in electronic image forming apparatuses such as electrostatic copying machines and laser beam printers.

[Brief description of drawings]

FIG. 1 is a graph showing the absorbance of a methanol extract of a toner used in a developer of the present invention at wavelengths of 200 to 700 nm.

FIG. 2 is a wavelength of 200 to 700 n of a methanol extract of a toner containing an azo chromium complex salt dye as a charge control agent.
It is a graph which shows the light absorbency in m.

FIG. 3 Wavelength 200 to 700 nm of a methanol extract of a toner containing a salicylic acid metal complex as a charge control agent.
It is a graph which shows the light absorbency in.

FIG. 4 is a schematic diagram of a carrier containing a toner containing an azo chromium complex salt dye as a charge control agent used in a two-component magnetic developer. 200-700 nm
It is a graph when the light absorbency in is measured.

FIG. 5 shows the mixing / stirring time when the operation of mixing / stirring the toner containing the charge control agent and the magnetic carrier or the mixing / stirring of the toner not containing the charge control agent and the magnetic carrier is continued. It is a graph which shows the relationship with a spent rate.

FIG. 6 shows the mixing / stirring time when the operation of mixing / stirring the toner containing the charge control agent and the magnetic carrier or the mixing / stirring of the toner not containing the charge control agent and the magnetic carrier is continued. It is a graph which shows the relationship with a charge amount.

FIG. 7 is a graph showing the relationship between the amount of the adhering substance of the carrier to which the toner component is attached due to the spent and the amount of the charge control agent in the toner that causes the spent.

FIG. 8 is a graph showing the relationship between the amount of spent and the mixing / stirring time when the operation of mixing / stirring each of the components in the toner and the magnetic carrier is continued.

FIG. 9 is an explanatory diagram illustrating occurrence of charging failure due to spent in a conventional two-component magnetic developer.

[Explanation of symbols]

 1 Carrier Particles 2 Toner 22 Reverse Toner

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 9/107 G03G 9/08 325 372 374 9/10 331 (72) Inventor Akihiko Kawatani Central Osaka 1-28 Takumazo, Mita Kogyo Co., Ltd. (72) Inventor Yoshitake Shimizu Chuo-ku, Osaka 1-28 Tamatsukuri Co., Ltd. (32) Inventor Hirano Nobuhiro Hirano Chuo-ku, Osaka 1-22 Tamatsukuri Mita Industrial Co., Ltd.

Claims (5)

[Claims] 1. A two-component developer containing a toner and a carrier, wherein the toner contains toner particles, and the toner particles contain a fixing resin and a magnetic powder dispersed in the resin. The fixing resin is a composition containing a resin having a low molecular weight substance having an anionic polar group and a polymer having a high molecular weight substance, and the acid value of the low molecular weight substance is higher than the acid value of the high molecular weight substance. And the magnetic powder is less than 0.1% with respect to 100 parts by weight of the fixing resin.
The carrier particles are contained in the toner particles in an amount of 1 to 5 parts by weight, and the carrier particles contain a thermoplastic resin and a high-resistivity magnetic powder dispersed in the thermoplastic resin. 50 to 150 μm, the thermoplastic resin is a resin composition containing a resin having a cationic polar group, and the high resistance magnetic powder has a specific resistance of 1 × 10 ⁵ Ω · cm or more. A two-component developer, which is contained in the carrier particles in an amount of 60 to 90% by weight. 2. The extract obtained by extracting the toner with methanol has substantially no absorption peak in the region of 280 to 350 nm, and the absorbance in the region of 400 to 700 nm is substantially zero. The developer according to claim 1. 3. The acid value of the low molecular weight substance is 3 to 15, the acid value of the high molecular weight substance is 6 to 25, and the ratio of the acid value of the high molecular weight substance to the acid value of the low molecular weight substance. The developer according to claim 1, wherein the ratio is 1: 1.2 to 1: 8. 4. The fixing resin 100 comprises the magnetic powder.
The developer according to claim 1, which is contained in a ratio of 0.5 to 3 parts by weight with respect to parts by weight. 5. The volume-based average particle diameter of the toner particles is 5
2. The developer according to claim 1, wherein spacer particles having a volume-based average particle diameter of 0.05 to 1.0 μm are attached to the surface of the toner particles.