JPH0876401A - Developing method - Google Patents

Abstract

PURPOSE: To provide a developing method using a toner that contains no electrostatic charge control agent being mainly attributable to a spent at time of copying, according to this method, the toner is sufficient enough in electrifiability, no scattering at time of copying, adequate enough in trabsfer efficiency, thereby stably securing a required density copied picture for hours, and further such a fact that some filming is produced in an organic sensitizer is made reducible. CONSTITUTION: This is a method of developing a static charge latent image formed on an organic sensitizer with a binary system developer containing a magnetic carrier and a toner. This toner contains fixing resin and toner grains containing magnetic powder dispersed in the resin. The fixing resin is composed of a composition containing resin with an anionic polar group. The magnetic powder is contained in the toner grains at the rate from 0.1 to 5 pt.wt. to 100 pt.wt. of the fixing resin. An extractant at a time when the toner is extracted by methanol has no absorption peak substantially in a range of 350nm from 280, and its adsorbance is substantially zero in a range of 700nm from 400.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for developing an electrostatic latent image formed on an organic photoreceptor with a two-component developer containing at least a magnetic carrier and a toner, and more specifically, The present invention relates to a developing method suitable for use in an electrophotographic image forming apparatus such as an electrostatic copying machine, a plain paper facsimile, and a laser beam printer, which effectively prevents toner contamination on the surface of an organic photoreceptor.

[0002]

2. Description of the Related Art An organic photoconductor is used as a photoconductor of an image forming apparatus using electrophotography, such as a copying machine, a plain paper facsimile or a laser printer. This is because the organic photoconductor has advantages such as being cheaper than the inorganic photoconductor using selenium or amorphous silicon, having high productivity, and being non-polluting.

By the way, in the electrophotographic image forming apparatus, a two-component developer is used as one of the developers for developing the electrostatic latent image on the photosensitive member. 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 salt dyes containing a metal such as chromium (for example, azo dyes) and oxycarboxylic acid metal complex salts (for example, salicylic acid metal complex salts) 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 complex salts.
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, a toner component adheres to the surface of the carrier due to the use of the toner for a long time, so that the charged state of the carrier surface becomes similar to the charged state of the toner particle surface. As a result, there is also a drawback that toner scattering occurs and transfer efficiency decreases.

Further, since the surface of the organic photoconductor is formed of the resin composition, the so-called filming phenomenon, in which the toner components adhere to the surface of the photoconductor due to the rubbing force with the toner during development, tends to occur. In particular, when the above-mentioned metal complex salt is used as the charge control agent, the metal complex salt is exposed on the toner surface, so that the filming by the metal complex salt tends to contaminate the surface of the photoreceptor.
When the contamination with the metal complex salt progresses, the charging characteristics of the photoconductor deteriorate, and a good copy image cannot be obtained.

[0008]

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 developing method capable of preventing the organic photoreceptor from being contaminated (filming) with a metal complex salt since it does not contain a charge control agent at all.

Another object of the present invention is that the toner has a good charging performance even though it does not contain a charge control agent at all, so that an image having less toner scattering and excellent image quality can be transferred efficiently. Another object of the present invention is to provide a developing method capable of stably forming over a long period of time.

Still another object of the present invention is to provide a developing method which does not cause spent even when used for a long period of time and, as a result, maintains good image quality and stable transfer efficiency.

[0011]

The present invention is a method for developing an electrostatic latent image formed on an organic photoreceptor with a two-component developer containing at least a magnetic carrier and a toner. The toner contains a fixing resin and toner particles containing magnetic powder dispersed in the resin, and the fixing resin is a composition containing a resin having an anionic polar group. The toner is 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, and the extraction liquid when the toner is extracted with methanol is substantially in the region of 280 to 350 nm. Has no absorption peak, and the absorbance in the region of 400 to 700 nm is substantially zero, whereby the above object is achieved.

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.
Spacer particles of μm are attached.

In a preferred embodiment, the organic photoreceptor is a positive charging type single layer organic photoreceptor.

[0014]

The toner used in the present invention does not contain any charge control agent such as an azo dye or a metal complex salt of oxycarboxylic acid. Therefore, as described later, since the spent due to the charge control agent is not generated, it is possible to perform copying with high image quality for a long period of time, and it is possible to effectively prevent contamination on the surface of the photoconductor.

Further, when the toner having the spacer particles is used, the contact between the toner particles and the OPC photoreceptor is reduced, so that the adhesion of the toner resin composition other than CCA to the OPC surface can be effectively eliminated. .

Since this toner does not contain any 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, in the toner used in the present invention, these compounds are not detected by a chemical reaction. Alternatively, no absorption peaks due to these compounds are detected in the organic solvent extract of the toner used in the present invention. For example, when the toner is extracted with an organic solvent, for example, methanol, the extract contains 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 is detected at all in an extract obtained by extracting 0.1 g of toner with 50 ml of methanol, or even if it is detected, the absorbance at the peak position is 0.05. It means the following. 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 toner used in the present invention, the instability of the charge amount due to the absence of the charge control agent is compensated for 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, if necessary, by attaching spacer particles having a predetermined particle size to the surface of the toner particles,
The transfer efficiency from the photoconductor to the transfer paper is improved.

The above will be described in detail below.

The absorbance curve of the methanol extract of the toner used in the present invention at 200 to 700 nm is shown in FIG. As shown in this curve, this extract does not have any peaks attributed to each charge control agent. That is 2
It has substantially no absorption peak in the region of 80 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 chromium complex salt dye as the charge control agent is 400 to 700 nm, especially 550 to 57 nm.
Has a peak in the region of 0 nm (FIG. 2), and
The absorbance curve of a methanol extract of a toner containing a salicylic acid metal complex salt as a charge control agent is 280 to 350 nm.
Has a peak in the region of the range (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 at a considerably high concentration on the surface of the toner particles. is there.

The carrier of the developer whose chargeability of the carrier becomes insufficient due to the generation of spent is extracted with methanol,
When the absorbance at 400 to 700 nm is examined, a peak due to the charge control agent is observed in that region. For example, a toner containing an azo chromium complex salt dye, the absorbance curve of which is shown in FIG. 2, is used for a long time,
FIG. 4 shows the absorbance curve of the methanol extract of the carrier when the spent was generated. In FIG. 4, a peak is recognized at the same position as that of the charge control agent in FIG. Conventionally, the spent was considered to occur because the resin for fixing the toner adheres to the surface of the carrier to form a resin film, but due to the above fact, one of the main causes of the spent is the charge control agent. It was found that there is a transition from the toner particles to the carrier surface.

The inventors further conducted the following experiment in order 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 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 carrier surface by the spent. The weight of the deposit is a percentage of the total weight of the carrier having the deposit and is shown in FIG. 5 as the percentage of spent. Further, FIG. 6 shows the relationship between the elapsed time and the toner charge amount. Further, the same measurement was performed for the developer containing the toner having the toner particles not containing the charge control agent and the carrier. The results are also shown in FIGS. 5 and 6. In FIGS. 5 and 6, the black circle plots show the measured values of the toner containing the charge control agent, and the white circle plots show the measured values of the toner without the charge control agent. From FIGS. 5 and 6, it can be seen that the toner containing the charge control agent has more deposits on the carrier surface 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 surface of the carrier was measured by the spent, and this was plotted on the abscissa (shown as the amount of spent), and the amount of the charge control agent in the toner component was plotted on the ordinate. The graph is shown in FIG. 7. 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. It can be seen from FIG. 7 that a large amount of the charge control agent is deposited and adheres to the carrier surface in the initial stage of using the developer. In FIG. 7, the measured value approaches the calculated value indicated by the dotted line as the amount of spent increases.
This is because this is the result of an experiment in a closed system in which toner is not replenished, and when toner is replaced in the copying machine, the difference between the two is considered to widen.

Further, in order to investigate the relationship between the components constituting the toner particles and the spent, the inventors mixed a carrier with a charge control agent, a fixing resin, carbon black as a colorant, and a wax. -The weight of the deposits on the carrier surface generated over time when stirring was 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 carrier surface.

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 1 is 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 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 opposite polarity toner 22 is carrier 1
Since it is formed on the surface, toner scattering occurs, and transfer efficiency decreases.

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

The instability of the charge amount due to the absence of the charge control agent, mainly the lack of the charge amount, is due to the use of a toner having an anionic polar group as the fixing resin 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 being bonded to the skeleton of the resin itself, it does not migrate to the surface of carrier particles like a charge control agent and cause spent. However, conversely, since the charging property of the toner particles near the surface is not so great, the coupling between the toner particles and the carrier by the Coulomb force in the magnetic brush at the time of development is still insufficient. Therefore, when high-speed copying is performed, the bondability with the carrier is weak, and the scattering of toner is not sufficiently suppressed. There is a drawback that the inside of the copying machine is contaminated by the scattering of the toner and so-called fog occurs in the image of the copy.

In the present invention, as a second requirement as described above, the magnetic powder is contained in the toner particles in a predetermined ratio, that is, in a ratio of 0.1 to 5 parts by weight with respect 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 attraction force is generated between the toner particles and the carrier. In this way, in addition to the Coulomb force between the toner particles and the carrier particles, a magnetic attractive force is generated, so that toner scattering is prevented. In general, the smaller the amount of charge per toner particle, the greater the number of toner particles attached to a given electrostatic latent image, and thus the apparent development sensitivity.

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 parts by weight, the charge amount of the toner is insufficient as described above, the toner is not sufficiently bonded to the carrier, and the toner is likely to be 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 and the toner becomes too large, so that the toner does not adhere sufficiently to the electrostatic latent image, resulting in a low image density.

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 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, since the toner does not contain the conventional charge control agent, the surface of the organic photoconductor is less contaminated, the filming of the organic photoconductor is suppressed, and the charging characteristic of the organic photoconductor is suppressed. Can be suppressed.

In the present invention, in order to further enhance the transfer efficiency of the toner image and to further suppress the filming of the organic photoreceptor, it is preferable that the surface of the toner particles be
Spacer particles having a particle diameter of 0.05 to 1.0 μm are attached.

The spacer particles can act as a fluidity improving agent 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 is increased by copying for a long time, the toner can be easily transferred from the surface of the photoconductor, so that the transfer efficiency is increased and the filming of the organic photoconductor can be prevented.

Fine particles having a particle diameter of about 0.015 μm have been used as an external additive as a conventional fluidity improving agent for toner, and 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.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The preferable modes of the present invention will be described below.

(Fixing Resin) The fixing resin contained in the toner particles of the toner used in the present invention is a composition containing a resin having an anionic polar group. Such a resin is obtained by polymerizing a monomer containing a monomer having an anionic polar group, and the obtained resin may be a homopolymer or a copolymer.

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 required 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):

[0043]

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.

In the present specification, the "lower alkyl group" refers to an alkyl group having 1 to 5 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):

[0048]

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):

[0052]

[Chemical 3]

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

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

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

[0056]

[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):

[0060]

[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):

[0064]

[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. Such a resin has an acid value of 2 to 3 when the anionic polar group is present in the form of a free acid.
It is desirable to have an anionic polar group in a ratio of 0, preferably 5 to 15. 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 the above-mentioned monomer having an anionic polar group and at least one kind of the acrylic monomer of the formula (I) as an essential component, and if necessary, the compound of the formula (II ), A copolymer containing the monomer of the formula (VI) as an optional component is used. Each of the above monomers is
One kind or a combination of two or more kinds may be used for preparing 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 in the above range.

(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.
m 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, the toner may scatter during development, or the transfer efficiency may decrease.

(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 which 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, alumina white.

The 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) Toner particles used in the above-mentioned toner are prepared by a general method for producing toner particles,
For example, it can be produced by a pulverizing and classifying method, a melt granulating method, a spray granulating method and a polymerization method, and is usually produced by a pulverizing and classifying method.

For example, the components for forming the toner particles are premixed by a mixer such as a Henschel mixer, then kneaded by using 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 improver 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.

The spacer particles are contained in an amount of not more than 10% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total weight of the toner. If it is excessive, the density of the copied image may be insufficient.

In order to externally add the fluidity improving agent and the spacer particles to the toner particles, for example, the fluidity improving agent 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 present invention is obtained.

(Preparation of Developer) The above toner is mixed with a magnetic carrier to give a two-component developer.

As the magnetic carrier, a ferrite type magnetic carrier is preferably used. Preferably, in addition to Fe, soft ferrite containing at least one kind of metal component selected from the group consisting of Cu, Mg, Mn and Ni, preferably two or more kinds, for example, sintered ferrite of copper-zinc-magnesium ferrite. Particles consisting of are used, especially spherical particles. The surface of the magnetic carrier may not be coated, but in general, it is preferably coated with silicone resin, fluorine resin, epoxy resin, amino resin, urethane resin or the like. The particle size of the magnetic carrier is preferably in the range of 30 to 200 μm, particularly 50 to 150 μm. The saturation magnetization of the carrier is 30 to 70.
It is preferably in the range of emu / g, particularly 45 to 65 emu / g.

The mixing ratio of the magnetic carrier and the toner is generally 98: 2 to 90:10 by weight, particularly 97: 3 to 9 by weight.
A weight ratio of 4: 6 is preferred.

(Image Forming Apparatus) FIG. 10 is a system diagram of the image forming apparatus 11 in which the developing method of the present invention is carried out.

The image forming apparatus 11 includes a rotatable photosensitive drum 13 having a photosensitive layer 12 formed on its surface, a main charger 14 for uniformly applying a predetermined amount of electric charge to the photosensitive layer 12, and a photosensitive layer 12. An optical device 15 for exposing and forming an electrostatic latent image on the photosensitive layer 12, a developing device 16 for developing the electrostatic latent image on the photosensitive layer 12, and a toner image formed on the photosensitive layer 12 are formed. Transfer device 18 for transferring to recording paper 17, cleaning device 19 having a cleaning blade for removing toner remaining on photoconductor drum 13, and photoconductor drum 1
3 to remove the electric charge remaining on the photosensitive drum 13
A static elimination lamp 20 and the like for setting the surface potential of the above to a predetermined uniform potential is provided.

According to such an image forming apparatus 11, after the main charger 14 uniformly applies a predetermined amount of electric charge to the photosensitive layer 12, the optical device 15 irradiates the photosensitive layer 12 with light to expose it. An electrostatic latent image is formed on layer 12. Thereafter, the developing device 16 supplies the toner onto the photosensitive layer 12 to visualize the electrostatic latent image. The toner image on the photosensitive drum 13 is transferred to the recording paper 17 by the transfer device 18. After the transfer, the toner remaining on the photosensitive drum 13 is removed by the cleaning device 19. next,
The static elimination lamp 20 irradiates the photosensitive layer 12 with light,
The charges remaining on the photosensitive layer 12 are removed, and the photosensitive layer 1
The surface potential of 2 is equalized to a predetermined potential. After that, the main charger 14 charges the photosensitive drum 13 again. These series of processes are continuously and repeatedly performed according to the rotation of the photosensitive drum 13.

(Organic Photoreceptor) The developing method of the present invention can be applied to a monolayer-dispersion type electrophotographic photoreceptor for electrophotography and a laminated type organic photoreceptor for electrophotography.

As a single-layer type photoreceptor, as shown in FIG. 11 (a), there is one in which a photosensitive layer 12 in which a charge generating substance is dispersed in a charge transport medium on a base tube 10 is provided. As the laminated type photoreceptor, for example, as shown in FIG. 11B, the charge generation layer (CG) is formed on the surface-treated aluminum base tube 10.
L) 12a is formed and the charge transport layer (CTL) 12b is provided on the charge generation layer 12b, or the charge transport layer is provided on the raw tube, and the charge generation layer is provided on the charge transport layer. There is something. The present invention has significant advantages in the case of a positively chargeable organic single layer photoreceptor.

As the charge generating substance contained in the photosensitive layer,
Any organic photoconductive pigment known per se can be used. In particular, phthalocyanine pigments, perylene pigments, quinacridone pigments, pyrantrone pigments, disazo pigments, photoconductive organic pigments such as trisazo pigments alone,
Alternatively, two or more kinds may be used in combination.

As the charge transport medium, a resin medium in which a charge transport substance is dispersed is used. As the charge transport material, any hole transport material or electron transport material known per se is used for the purpose of the present invention.

Examples of suitable hole transport materials are poly-N-vinylcarbazole, phenanthrene, N-ethylcarbazole, 2,5-diphenyl 1,3,4-oxadiazole, 2,5-bis ( 4-diethylaminophenyl)
-1,3,4-oxadiazole, bis-diethylaminophenyl-1,3,6-oxadiazole, 4,4 '
-Bis (diethylamino) -2,2'-dimethyltriphenylmethane, 2,4,5-triaminophenylimidazole, 2,5-bis (4-diethylaminophenyl)
-1,3,4-triazole, 1-phenyl-3- (4
-Diethylaminostyryl) -5- (4-diethylaminophenyl) -2-pyrazoline, p-diethylaminobenzaldehyde- (diphenylhydrazone), 3,3 '
-Dimethyl-N, N, N ', N'-tetrakis-4-methylphenyl (1,1'-biphenyl) -4,4'-diamine or the like, or a combination of a plurality of these.

An example of a suitable electron transport material is 2-nitro-
9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone, 2,
4,5,7-Tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, dinitroanthoquinone, 2,6-dimethyl-2 ',
Any such as 6-ditert-butyldiphenoquinone,
Alternatively, a combination of a plurality of these may be used. Examples of the binder resin include various ones, for example, styrene-based polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic polymers, styrene-acrylic copolymers. Polymer, styrene-vinyl acetate copolymer, polyvinyl chloride,
Vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallylphthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin,
Examples include various polymers such as phenolic resins and photocurable resins such as epoxy acrylate and urethane acrylate. A photoconductive polymer such as poly-N-vinylcarbazole can also be used as the binder resin.

The charge generating substance to be present in the photosensitive layer is suitably in the range of 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, per 100 parts by weight of the binder resin, while the charge transporting material is used. The substance is suitably in the range of 20 to 500 parts by weight, particularly 30 to 200 parts by weight, per 100 parts by weight of the binder resin. The thickness of the photosensitive layer is 10 to 40μ.
m, particularly in the range of 22 to 32 μm is good in view of high surface potential, printing durability and sensitivity.

As the drum base made of metal of the photoconductor drum, an aluminum tube or an aluminum tube subjected to alumite treatment is generally used. The drum substrate is not limited to the above metal, and any material having conductivity may be used. Examples include conductive resins and conductive films.

To form the photosensitive layer, the resin is used as an amide solvent such as N, N-dimethylformamide or N, N-dimethylacetamide; a cyclic ether such as tetrahydrofuran or dioxane; dimethyl sulfoxide; benzene, toluene, xylene or the like. An aromatic solvent; ketones such as methyl ethyl ketone; N-methyl-2-pyrrolidone; phenols such as phenol and cresol; and a solvent such as phenols are dissolved, and the charge generating substance is dispersed in the solvent to obtain a coating composition. This composition is applied to a conductive drum substrate to form a photosensitive layer.

[0099]

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

(Example 1) A. Toner preparation

[0101]

[Table 1]

The above components were melt-kneaded by a twin-screw extruder, then the kneaded product was ground by a jet mill and classified by 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 were added (externally 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 toner was obtained by mixing for 2 minutes with a Henschel mixer.

B. Preparation of Single-Layer Electrophotographic Photoreceptor A photosensitive layer composition having the following composition is dispersed for 2 hours with a paint shaker to prepare a coating solution for a single-layer type photosensitive layer, and the obtained coating solution has an outer diameter. Immersion processing on the surface of a 30 mm aluminum cylinder, drying at 110 ° C. for 30 minutes,
A single-layer type photosensitive layer having a film thickness of 30 μm was formed to obtain a positive charging type electrophotographic photoreceptor.

(Composition of Photosensitive Layer Composition) Bisazo Pigment (Compound Represented by Chemical Formula (1)) 10 parts by Weight 3,3′-Dimethyl-N, N, N ′, N′-tetrakis-4-methyl Phenyl (1,1'-biphenyl) -4,4'-diamine 100 parts by weight 3,3'-dimethyl-5,5'-ditert-butyl-4,4'-diphenoquinone 50 parts by weight Polycarbonate resin 150 parts by weight Department

[0106]

[Chemical 7]

C. Development Each of the toners obtained in the above section A has an average particle size of 100.
A ferrite carrier of μm was added and uniformly mixed to obtain a two-component developer having a toner concentration of 3.5% by weight. Then
The developer was evaluated for each of the following items.

(Example 2) A. Preparation of Toner To the toner particles obtained in Example 1, hydrophobic silica fine particles having an average particle diameter of 0.015 μm were added as a fluidity improving agent at a ratio of 0.3 parts by weight to 100 parts by weight of the toner particles, and Acrylic resin fine particles having an average particle diameter of 0.3 μm were added (externally added) at a ratio of 0.5 part by weight to 100 parts by weight of the toner particles, and mixed by a Henschel mixer for 2 minutes to obtain a toner.

B. Preparation of Single Layer Electrophotographic Photoreceptor A positively charged electrophotographic photoreceptor prepared in the same manner as in Example 1 was used.

C. Development A two-component developer was obtained in the same manner as in Example 1 except that the toner obtained in the above section A was used, and the developer was evaluated for each item in the same manner as in Example 1.

(Comparative Example 1) A. Preparation of Toner 2 parts by weight of an azo chromium complex salt dye as a charge control agent was further added to each component in Table 1, and 100 parts by weight of toner particles of hydrophobic silica fine particles having an average particle diameter of 0.015 μm were used as a fluidity improving agent. Was added (externally added) in an amount of 0.3 parts by weight with respect to, and mixed for 2 minutes with a Henschel mixer to obtain a toner.

B. Preparation of Single Layer Electrophotographic Photoreceptor A positively charged electrophotographic photoreceptor prepared in the same manner as in Example 1 was used.

C. Development A two-component developer was obtained in the same manner as in Example 1 except that the toner obtained in the above section A was used, and the developer was evaluated for each item in the same manner as in Example 1.

[Evaluation of Developing Method] The evaluation method of the present invention will be described below.

The following tests were used with DC-25 manufactured by Mita Kogyo Co., Ltd. equipped with the above-mentioned positively charging type electrophotographic photosensitive member.
This is a device created by modifying 56 to be an experimental machine.

(A) Image Density (ID) 50,000 copies were made using a character original having a black area ratio of 8%. 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.

(B) Fog Density (FD) 50,000 copies were made using a character original having a black area ratio of 8%. 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 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) Charge Amount 50,000 copies were made using a character original having an area ratio of black area of 8%. The charge amount of 200 mg of the developer was measured every 5,000 sheets using a "blow-off powder charge amount measuring device" (manufactured by Toshiba Chemical Co.), and the average value of the charge amount per 1 g of toner was calculated. Table 2 shows the evaluation results.

(D) Amount of Adhered Substances on Carrier Surface by Spent A copy is made using a character original having an area ratio of black portion of 8%.
At the time of copying 50,000 sheets, the developer was sampled. The developer was placed on a 400-mesh sieve and sucked from below with a blower to separate the toner from the carrier.
5 g of the carrier remaining on the sieve was put in a beaker, and toluene was further added to the beaker to dissolve the toner component adhering to the surface of the carrier by means of the spent. After that, the toluene solution was discarded while the carrier was attracted from below the beaker with a magnet. This was repeated several times until the toluene became colorless, and then the toluene adhering to the carrier was evaporated in an oven, and the weight of the residue obtained was measured.
The difference between the weight of the carrier initially put in the beaker and the weight after the evaporation of toluene is the amount of the toner component adhering to the carrier surface by the spent (spent amount). The spent amount is represented by mg of the toner component attached to 1 g of the carrier.
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%.
The toner scattering state in the copying machine at the time of copying 50,000 sheets was visually observed and evaluated according to the following criteria. Table 2 shows the evaluation results
Shown in ◯: No toner scatter x: Toner scatter (f) Filming of the organic photoconductor drum The surface of the organic photoconductor at the end of copying 50,000 sheets was visually observed and evaluated according to the following criteria. Table 2 shows the evaluation results. ○: Without filming ×: With filming

[0121]

[Table 2]

[Consideration of Evaluation Results] The toners obtained in Examples 1 and 2 were stable in a very good state even when the image density, fog density and charge amount were copied from the initial stage to 50,000 sheets. . On the other hand, in the toner of Comparative Example 1 in which the toner particles contained the charge control agent, the occurrence of spent and filming, the occurrence of toner scattering due to the decrease of the charge amount, and the increase of fog were observed.

[0123]

According to the present invention, there is provided a developing method using a toner containing no charge control agent, which is a main cause of spent during copying. The toner particles of this toner contain a fixing resin having an anionic polar group, and the toner particles contain magnetic powder at a predetermined ratio. Further, spacer particles having a predetermined particle diameter are attached to the surface of the toner particles as needed. Therefore, the chargeability of the toner is sufficient, the toner does not scatter during copying, the transfer efficiency is sufficient, and a copy image having a required density can be stably obtained for a long time.

Further, in the present invention, since the electrostatic latent image formed on the organic photoconductor is developed using the developer containing the toner having the above-mentioned constitution, the occurrence of filming on the organic photoconductor is suppressed. Therefore, a good copy image can be formed over a long period of time.

Particularly, it is effective in combination with a positive-charge type single-layer organic photoconductor in which the charging property is likely to be affected by contamination of the photoconductor surface.

Such toner is preferably used in an electronic image forming apparatus such as an electrostatic copying machine or a plain paper facsimile.

[Brief description of drawings]

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

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 of a methanol extract of a toner containing a salicylic acid metal complex salt as a charge control agent, 200 to 700 nm.
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.

FIG. 10 is an explanatory diagram showing an example of an image forming apparatus for carrying out the developing method of the present invention.

11 is an enlarged cross-sectional view of an organic photoconductor used in the image forming apparatus shown in FIG.

[Explanation of symbols]

 1 Carrier 2 Toner 22 Reverse Polarity Toner 11 Image Forming Device 12 Photosensitive Layer 13 Photosensitive Drum

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G03G 9/097 15/08 507 L G03G 9/08 321 351 372 374 (72) Inventor Kenbo Kubo Osaka 1-228 Tamatsukuri, Chuo-ku, Mita Industrial Co., Ltd. (72) Inventor Kazuya Nagao Osaka 1-2-2 Tamatsukuri, Chuo-ku, Mita Industrial Co., Ltd. (72) Inventor Asano Terumo Osaka 1-22 Tamatsukuri, Chuo-ku, Yokohama-shi Mita Engineering Co., Ltd.

Claims (3)

[Claims] 1. A method for developing an electrostatic latent image formed on an organic photoreceptor with a two-component developer containing at least a magnetic carrier and a toner, wherein the toner is a fixing resin. And toner particles containing magnetic powder dispersed in the resin, wherein the fixing resin is a composition containing a resin having an anionic polar group, and the magnetic powder is 100 parts by weight of the fixing resin. For 0.
1 to 5 parts by weight is contained in the toner particles, and when the toner is extracted with methanol, the extraction liquid is 280
To 350 nm has substantially no absorption peak,
And the absorbance in the region of 400 to 700 nm is substantially zero. 2. The volume-based average particle diameter of the toner particles is 5
2. The developing method 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. 3. The developing method according to claim 1, wherein the organic photoconductor is a positive charging type single-layer organic photoconductor.