JPH08328300A - Developing method - Google Patents

Abstract

PURPOSE: To make it possible to stabilize the electrostatic charge performance of a toner over a long period of time, to extend the life of the toner and carrier, to secure the toner electrostatic charge quantity sufficient for development, to effectively prevent the contamination of an org. photoreceptor surface with the toner and to effectively prevent filming. CONSTITUTION: This method comprises developing the electrostatic charge image formed on the org. photoreceptor by using a two-component type developer contg. at least the magnetic carrier and toner. The toner which contains a fixing resin and toner particles contg. carbon black dispersed in this resin and does not contain a charge control agent, is used. The fixing resin consists of a compsn. contg. a resin having a free or neutralized anionic polar group. The carbon black which has pH of <7 and has (7-pH) /(specific surface area (m<2> /g)) within in a range of 0.010 to 0.050, is used.

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 charge image formed on an organic photoreceptor with a two-component developer containing a magnetic carrier and a toner. The present invention relates to a developing method in which toner contamination on the surface of a photoconductor is effectively prevented.

[0002]

2. Description of the Related Art Organic photoconductors are widely used as photoconductors for electrophotographic image forming apparatuses such as copying machines, facsimiles, and laser printers. This organic photoconductor is cheaper than inorganic photoconductors such as selenium and amorphous silicon, and has advantages such as high productivity and no pollution.

A so-called two-component magnetic developer is widely used as a developer for developing an electrostatic latent image formed on a photoconductor. This two-component magnetic developer is iron powder,
It is composed of a magnetic carrier composed of ferrite particles and the like, and a toner in which a colorant such as carbon black is dispersed in a fixing resin.

At the time of development, by mixing the magnetic carrier and toner, the toner particles are charged to a constant polarity, and the mixture is conveyed to the photoconductor in the form of a magnetic brush, and the surface of the photoconductor is magnetically brushed. Rubbing is performed to cause the charged toner to adhere to and be held on the electrostatic latent image on the surface of the photoconductor to form a visible image. In order to form a stable image with a constant amount of toner attached to the latent image, it is common to mix a charge control agent in the toner particles so that a constant charge amount is given to the toner. is there. For example, negative charge toners use negative charge control agents such as metal-containing complex salt dyes and metal complexes of oxycarboxylic acid (for example, JP-A-3-67268), and positive charge toners use oil-soluble dyes such as nigrosine. Positive charge control agents such as amine-based control agents and the like (for example, JP-A-56-106249) are used.

[0005]

By the way, the charge control agents that have been conventionally used are mostly compounds containing heavy metals such as chromium-containing complex salts, and from the viewpoint of environmental safety,
If possible, it is desirable to avoid using such a charge control agent. In addition, the charge control agent is more expensive than a coloring resin such as a fixing resin or carbon black, which is a constituent material of the toner, and increases the unit price of the toner despite the content rate of about several percent. Thus, development of a toner containing no charge control agent is desired.

Further, in the toner used in the conventional two-component type developer, a so-called spent that the toner adheres to the carrier surface is generated by long-term use, so that the charge state of the carrier surface is charged on the toner particle surface. It resembles the state. As a result, there is a problem in that toner scattering occurs and transfer efficiency decreases.

Further, when the electrostatic latent image formed on the organic photoconductor is developed by using a two-component developer, the surface of the organic photoconductor is formed of a resin composition, and therefore, at the time of development. There is also a problem that so-called filming development easily occurs, in which the toner component adheres to the surface of the photoconductor due to the rubbing of the toner. 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 photoconductor. When such contamination with the metal complex salt progresses, the charging characteristics of the organic photoconductor are deteriorated, and it becomes difficult to obtain a good copied image.

Therefore, an object of the present invention is to develop an electrostatic latent image formed on the surface of an organic photoconductor by magnetic brush development using a two-component developer, and to develop an organic compound containing a toner component such as a metal complex salt. It is an object of the present invention to provide a developing method capable of effectively preventing contamination on the surface of a photoconductor.

Another object of the present invention is to impart good chargeability to the toner even though the toner particles do not contain a migrating charge control agent, reduce toner scattering, and provide excellent image quality. Another object of the present invention is to provide a developing method capable of forming a stable image with high transfer efficiency over a long period of time.

Another object of the present invention is to provide a developing method capable of stably forming a good image for a long period without generating a spent even during a long period of development.

[0011]

According to the present invention, there is provided a method of developing an electrostatic charge image formed on an organic photoconductor by using a two-component developer containing at least a magnetic carrier and a toner. And the toner contains a fixing resin and toner particles containing carbon black dispersed in the resin, and the fixing resin contains a resin having a free or neutralized anionic polar group. The carbon black has a pH of less than 7 and a (7-pH) / specific surface area (m ² / g) in the range of 0.010 to 0.050, and is based on the fixing resin medium. 4 to 15% by weight
A developing method is provided, which is characterized in that the developing method is incorporated.

[0012]

The present inventors have found the following interesting facts in the course of repeated research to prevent toner spent generation.

FIG. 1 of the accompanying drawings shows that of a conventional two-component magnetic developer toner used for developing a positively charged image, a toner containing a chromium complex salt dye (2: 1 type) as a charge control agent is methanol. Extraction liquid wavelength of 200 to 700n
2 is a light absorption curve at m and has a peak in a wavelength range of 400 to 700 nm, and FIG. 2 shows a wavelength 2 of a methanol extract of a toner using a salicylic acid metal complex as a charge control agent.
It is an absorbance curve from 00 to 700 nm and has a wavelength of 280
It has a peak in the region of ˜350 nm.

According to these results, all the extract liquids showed a characteristic absorption peak based on the charge control agent, which means that the surface of the toner particles contained the charge control agent in a considerably high concentration. ing.

On the other hand, in FIG. 3, the toner used in the measurement of FIG. 1 was used as a two-component magnetic developer, and the carrier in which charging failure was caused by the spent was similarly extracted with methanol. The absorbance curve at 200 to 700 nm is measured, and the wavelength is 400 to 70.
It has a peak in the region of 0 nm.

According to the measurement results, the charge control agent adheres to and deposits on the carrier surface in a high concentration, and the charging failure due to the spent is not the mere filming of the carrier surface due to the toner resin, which has been considered in the past. The surprising fact of migration of the control agent to the carrier surface was revealed.

This fact will become more apparent with reference to FIGS. 4 and 5. FIGS. 4 and 5 show the mixing time and the spent amount when a mixture of a toner containing a positive or negative charge control agent and a magnetic carrier and a mixture of a toner containing no charge control agent and a magnetic carrier were mixed. And the relationship between the mixing time and the charge amount are plotted. From these results, it becomes clear that in the case of containing the charge control agent, the amount of spent increases as the mixing time increases, and the decrease in the amount of charge increases.

Further, FIG. 6 shows the relationship between the amount of spent spent carrier and the charge control agent in the spent toner, and the dotted line in FIG. 6 indicates the predicted value calculated from the toner prescription. It is a plot. According to this result, it becomes clear that the charge control agent is selectively transferred to and adheres to the carrier surface in the early stage of spent generation. Incidentally, in the result of FIG. 6, the reason why the charge control agent amount is close to the predicted value from the composition with the increase of the spent amount is the result of the above-mentioned mixed system in the closed system without toner replenishment. Therefore, when the toner is replaced in the copying machine, it can be expected that the difference due to the presence or absence of the charge control agent is further widened.

Furthermore, FIG. 7 shows the relationship between the mixing time and the amount of spent when the individual components in the toner are mixed with the magnetic carrier. According to this result, it was clarified that the charge control agent is a component that easily migrates to the carrier surface among the respective components in the toner and easily causes spent.

From the above, the charging failure due to the spent generation in the conventional two-component magnetic developer is as shown in the explanatory view of FIG.
Also, as the toner is negatively charged, the spent layer is negatively charged as the spent is formed by the selective transfer of the antistatic agent to the carrier surface, and a positive polarity opposite polarity toner is formed. Can possibly be explained.

In the present invention, in order to prevent the transfer of the charge control agent to the surface of the magnetic carrier, the addition or blending of the transfer charge control agent to the toner particles is stopped. Along with this,
As shown in the absorbance curve of FIG. 9, the negatively chargeable toner of the present invention has a substantially zero absorbance at a wavelength of 400 to 700 nm even when extracted with methanol. Of course, the toner of the present invention does not have a positive charge control agent such as a salicylic acid metal complex, and therefore does not have a peak of absorbance at a wavelength of 280 to 350 nm of the methanol extract. In the present specification, the absorbance being substantially zero means that an absorption peak in the above wavelength region is not 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 that peak is detected. Is less than or equal to 0.05.

By the way, as shown in FIG. 5, the toner containing no charge control agent is inadequate in charge amount as compared with the toner containing the charge control agent. In the present invention,
In order to prevent this, a copolymer resin composition having an anionic polar group is used as the fixing resin medium, and carbon black as a colorant having a pH on the acidic side is used. By using such a fixing resin medium and carbon black, the amount of toner charge required for development can be obtained.

That is, the anionic polar group contained in the fixing resin medium imparts negative charge controllability to the toner, and since this polar group is present in the molecular skeleton of the resin, it does not act as a charge control agent. Thus, it does not migrate to the particle surface of the carrier and cause spent. The fixing resin medium used in the present invention has an acid value in relation to having an anionic polar group as described above,
The acid value is preferably in the range of 4 to 30. That is, when the acid value is greater than 30, the amount of anionic groups increases, so that the toner itself has high hygroscopicity, and stable triboelectric charging tends to be difficult. When the acid value is lower than 4, the amount of anionic groups is small, and it may be difficult to secure a sufficient toner charge amount for development. The anionic polar group may be present in the free acid form, or may be present in the form of a metal salt such as sodium salt, that is, in a neutralized form, and the acid value is the free acid form. Measured at. That is, in the present invention, the acid value is a value measured in the form of a free acid by hydrolyzing at least a part of the anionic polar group when it exists in a neutralized state. .

According to the present invention, as described above,
As carbon black as a colorant, the pH is on the acidic side (that is, less than 7), and (7-pH) / specific surface area (m
It is important to use a ratio of ² / g) in the range of 0.010 to 0.050. Generally, carbon black has a pH of about 8 and is biased toward neutral or alkaline side. In addition, in order to control the conductivity, carbon black that is acid-treated to have a pH of less than 7 is also known. In the present invention, carbon black having a pH of less than 7 is selectively used, but this does not mean that carbon black whose conductivity is controlled is used.

According to the study by the present inventors, it was confirmed that when the carbon black and the magnetic carrier were mixed and stirred, the carbon black was negatively charged. That is, in the present invention, by using the carbon black which has been treated with an acid and has a pH of less than 7, the negative chargeability of the fixing resin medium having the anionic polar group is reinforced, and the negative charge control agent is used. It is possible to effectively prevent the deterioration of the charging property due to the unblended.

In the present invention, the above-mentioned (7-pH) /
The value of the specific surface area is the degree of acid treatment, that is, an index showing the density of acid functional groups present on the surface of carbon black. If this value is smaller than the above range, the negative charging property is not sufficiently reinforced, Inevitably, the chargeability is reduced. On the other hand, when it is larger than the above range, the hygroscopicity of the toner becomes high, and it becomes difficult to secure a stable triboelectric charge amount.

The pH of carbon black was 5 g for a sample.
Can be boiled for 5 minutes in 100 ml of ion-exchanged water, allowed to cool, supplemented with evaporated water and filtered through filter paper, and the filtrate can be measured with a commercially available glass electrode pH meter.

Further, according to the present invention, since the developer in which the above-mentioned toner in which the charge control agent is not mixed is mixed with the magnetic carrier is used, it is rubbed against the surface of the organic photoconductor to be applied to the surface. Even if the formed electrostatic latent image is developed, there is very little tendency to contaminate the surface of the photoconductor, and filming of the organic photoconductor is effectively suppressed to prevent deterioration of the charging property of the organic photoconductor, The shortening of the life of the organic photoreceptor is effectively avoided.

[0029]

Preferred Embodiment of the Invention

(Fixing Resin Medium) The fixing resin of the toner used in the present invention contains a resin having an anionic polar group. In such a resin, examples of the anionic polar group include any polar group such as carboxylic acid, sulfonic acid, and phosphonic acid, and carboxylic acid type is particularly preferable. The copolymer resin having such an anionic polar group is one in which the monomer having the polar group is incorporated into the resin by random copolymerization, block copolymerization, graft copolymerization or the like. Suitable examples of such monomers are as follows.

Examples of the carboxylic acid type include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, maleic acid or fumaric acid. Etc.

Examples of the sulfonic acid type include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.

Examples of the phosphonic acid type include 2-acid phosphoxypropyl methacrylate, 2-acid phosphoxyethyl methacrylate, and 3-chloro-2-acid phosphoxypropyl methacrylate.

These anionic polar group-containing monomer units are neutralized with a free acid or with an alkali metal such as sodium or potassium, an alkaline earth metal such as calcium or magnesium, zinc or the like. It may be incorporated in the form.

The other monomer which is optionally used in combination with the above-mentioned anionic polar group-containing monomer is one in which the resulting polymer has the fixability and the chargeability required for the toner. One kind or a combination of two or more kinds of monomers having a system unsaturated bond is used.

Suitable examples of such a monomer include acrylic acid ester monomers, monovinyl aromatic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, Monoolefin-based monomers and the like. Specifically, the following can be exemplified. still,
In the following description, the lower alkyl group means a group having 5 or less carbon atoms.

Examples of the acrylate monomer include, for example, the following general formula (1): CH ₂ ═C (R ¹ ) —COOR ² (1) In the formula, R ¹ is a hydrogen atom or a lower alkyl group, and R ^{2 is} Is an alkyl group having 11 or less carbon atoms or a hydroxyalkyl group having 11 or less carbon atoms, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate , Phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, butyl δ-hydroxyacrylate, ethyl β-hydroxymethacrylate and the like.

Examples of the monovinyl aromatic monomer include the following general formula (2): CH ₂ ═C (R ³ ) -Φ-R ⁴ (2) In the formula, R ³ is a hydrogen atom, a lower alkyl group or halogen. R ⁴ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, Φ is a phenylene group, a substituent is a lower alkyl group,
Those having a halogen atom, an alkoxy group, an amino group or a nitro group, such as styrene, α
-Methylstyrene, vinyltoluene, α-chlorostyrene, o-, m-, p-chlorostyrene, p-ethylstyrene and the like.

Examples of the other monomers include those represented by the following general formulas (3), (4), (5) or (6). CH ₂ ═CH—OOCR ⁵ (3) In the formula, vinyl ester of R ⁵ is hydrogen atom or lower alkyl group, for example, vinyl formate, vinyl acetate, vinyl propionate and the like.

CH ₂ ═CH—O—R ⁶ (4) In the formula, R ⁶ is an alkyl group having 11 or less carbon atoms, such as vinyl ether such as vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl. Phenyl ether, vinyl cyclohexyl ether, etc.

CH ₂ ═C (R ⁷ ) —C (R ⁸ ) ═CH—R ⁹ (5) In the formula, each of R ⁷ , R ⁸ and R ⁹ is a hydrogen atom, a lower alkyl group or a halogen atom. , Diolefins such as butadiene, isoprene and chloroprene.

CH ₂ ═C (R ¹⁰ ) —R ¹¹ (6) In the formula, each of R ¹⁰ and R ¹¹ is a hydrogen atom or a lower alkyl group, monoolefins such as ethylene, propylene, isobutylene and butene. -1, pentene -1, 4
-Methylpentene-1 etc.

In the present invention, the anionic polar group in the above-mentioned (co) polymer resin is preferably present in an amount such that the fixing resin medium has an acid value of 4 to 30, particularly 5 to 15. is there. In addition, when a part or all of the anionic polar group of the resin is neutralized, a resin having an anionic polar group concentration corresponding to the above acid value including the polar group of the neutralized part It is good to say That is, when the acid value of the fixing resin medium is smaller than the above range, the amount of the anionic polar group is small and the chargeability of the toner is likely to be unsatisfactory,
On the other hand, if it is larger than the above range, the toner becomes sensitive to humidity, which is not preferable. Further, as long as the acid value as the fixing resin medium is within the above range, the (co) polymer resin having the anionic polar group is, for example, at least one of the monomers of the general formulas (1) to (6). It can also be used in the form of a blend with a polymer component obtained by polymerizing the seed.

In the present invention, a suitable copolymer resin contains, as an essential component, an anionic polar group-containing monomer and one or more of the acrylic monomers of the formula (1). Copolymer resins containing the monomers of formulas (2) to (6) can be mentioned, and the most preferable one is styrene-acrylic copolymer resin.

Further, in the present invention, the above-mentioned fixing resin medium has a weight average molecular weight of 70,000 to 200,000, particularly 80,000 to 150,000 in order to secure a certain pulverizability and granulation. Is preferred.

(Carbon Black) In the present invention, the carbon black dispersed in the fixing resin medium has a pH of less than 7, preferably 2 to 5, and (7-pH) / specific surface area. (M ² / g) is 0.0
As long as it is in the range of 10 to 0.050, particularly 0.015 to 0.040, any one can be used, but in general, furnace black is used, and the above treatment is carried out by acid treatment. Those adjusted to have a pH value satisfying the above conditions are preferable. Acid treatment
For example, it can be carried out by using an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or the like, and an organic acid such as acetic acid, citric acid, propionic acid, benzoic acid, salicylic acid, toluenesulfonic acid, etc. An acidic group such as a group is introduced to reinforce the negative chargeability of the toner. Further, the amount of acid used for the treatment is extremely small, as is clear from the above pH conditions, so that this does not adversely affect the electrical characteristics of the toner.

The specific surface area of such carbon black is usually 50 m ² / g or more, particularly 100 to 300.
It is preferably in the range of m ² / g from the viewpoint of dispersibility in the resin. Such carbon black is contained in the fixing resin medium in an amount of 4 to 15% by weight, particularly 6 to 1% by weight.
It is compounded in an amount of 2% by weight. If the blending amount is less than the above range, the negative chargeability of the toner becomes unsatisfactory and fogging and the like are likely to occur. If it is used in a larger amount than the above range, the fixability of the toner will deteriorate.

(Other compounding agents) In the toner used in the present invention, in addition to the above carbon black, various toner compounding agents known per se, for example, extender pigments, except that a charge control agent is not compounded, are used. A release agent or the like can be dispersed and compounded in the fixing resin medium.

Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Such pigments are used in an amount of 2 to 20 parts by weight, especially 5 to 15 parts by weight, per 100 parts by weight of the fixing resin medium.

Examples of the releasing agent include various waxes and low molecular weight olefin resins such as polypropylene, polyethylene and propylene-ethylene copolymer, and polypropylene is particularly preferable. Such a releasing agent is generally used in 100 parts by weight of the resin medium.
It is added in an amount of 0.1 to 10 parts by weight. As a result, the offset resistance at the time of heat fixing can be improved, and the spent resistance of the toner can be further improved.

In the present invention, in addition to the above-mentioned respective compounding agents, for example, magnetic powder may be dispersed and compounded in the fixing resin medium. By blending such magnetic powder, the toner particles in the magnetic brush at the time of development are held by the carrier not only by the Coulomb force but also by the magnetic attraction force, so that the toner scattering can be prevented more reliably, and the toner of the copying machine can be more reliably prevented. It is extremely preferable from the viewpoint of preventing toner contamination and fogging of copied materials. Such advantages are required as the copying speed increases. The addition of such magnetic powder also has the advantages that the amount of charge per toner particle can be reduced, the development sensitivity can be improved, and a high-density image can be obtained.

Examples of such magnetic powder include magnetic powders conventionally used in magnetic toners, such as ferric tetroxide (Fe ₃ O).
₄ ), ferric oxide (γ-Fe ₂ O ₃ ), zinc iron oxide (Z
nFe ₂ O ₄ ), yttrium iron oxide (Y ₃ Fe
₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron oxide copper (CuF)
e 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 (Mn
Fe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni),
Etc. can be mentioned. A particularly suitable magnetic powder is fine particle triiron trioxide (magnetite). The preferred 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 above-mentioned amount of the magnetic powder compounded is the resin medium 10
It may be as small as 0.1 to 5 parts by weight, especially 0.5 to 3.0 parts by weight, per 0 parts by weight. Conventionally, the magnetic toner used for the one-component magnetic developer uses the magnetic powder in an amount of more than 10 parts by weight per 100 parts by weight of the resin medium, but the amount of the magnetic powder used above is considerably smaller than this. With such a small amount of internal addition, it is possible to form a high-density image while preventing toner scattering.

(Toner) The toner used in the present invention can be produced by a known method such as a pulverizing and classifying method, a melt granulating method, a spray granulating method and a polymerization method, but the pulverizing and classifying method is generally used. . That is, the above-mentioned fixing resin medium and various toner compounding agents are pre-mixed with a mixer such as a Henschel mixer, and then kneaded using a kneading device such as a twin-screw extruder, and after cooling the kneaded composition, It is crushed and classified to obtain a toner.
The particle size of the toner is preferably such that the volume-based average particle size (median size by Coulter counter) is in the range of 5 to 15 μm, particularly 7 to 12 μm.

If necessary, a fluidity improving agent such as hydrophobic vapor phase silica can be externally attached to the surface of the toner particles to improve the fluidity of the toner. Such a fluidity improver is usually an extremely fine powder having a primary particle size of about 0.005 to 0.050 μm, and is based on the total weight of the toner (that is, the total amount of the above-mentioned toner particles and external additives). It is preferable to add externally in an amount of 0.1 to 2.0% by weight.

According to a preferred embodiment of the present invention, together with the fluidity improver, the particle size larger than that of the fluidity improver is 0.0.
Spacer particles having a particle size of 5 to 1.0 μm, particularly 0.07 to 0.5 μm are externally added to the toner particles. That is, by externally adding such spacer particles, the bond between the toner image and the latent image on the surface of the photoconductor is weakened so that the toner image can be easily peeled off. The transfer efficiency can be improved.

As the spacer particles, organic or inorganic inert particles having the above particle size can be used. Specific examples of such inert fixed particles include silica, alumina, titanium oxide, magnesium carbonate, acrylic resin powder, styrene resin powder, and magnetic powder, but in general, the above-mentioned magnetic powder, particularly fine particles. Preference is given to using ferrosoferric oxide (magnetite). This is because the magnetic powder existing on the surface of the toner particles also effectively acts on the toner scattering. Such spacer particles may be externally added in an amount of 10% by weight or less, preferably 0.1 to 10% by weight, and most preferably 0.1 to 5% by weight based on the total weight of the toner. When used in excess of this, the image density is reduced. When magnetic powder is used as the spacer particles, when the magnetic powder is internally added to the toner particles, the total amount of the magnetic powder and the internally added magnetic powder is 10% by weight or less based on the fixing resin medium. Is good. This is because, if this total amount becomes excessive, the image density will also decrease.

When the fluidity-improving agent and the spacer particles are externally added to the toner, the fluidity-improving agent and the spacer particles are preliminarily intimately mixed under a pulverizing condition, and this mixture is added to the toner to thoroughly disintegrate the toner. Good to do. As a result, these external additives adhere to the surface of the toner particles, that is, are held in contact with the surface of the toner particles or fixed in a state where they are partially driven into the surface of the particles.

(Magnetic Carrier) As the magnetic carrier particles used in combination with the above-mentioned toner, those known per se can be used, but the following formula (7): MOFe ₂ O ₃ (7) is preferable. In the formula, M is Cu, Zn, Fe, Ba, Ni, Mg, M
a magnetite (M = F) which is at least one metal selected from the group consisting of n, Al and Co.
e), ferrite (M is other than Fe), and among them, M is at least one of Cu, Zn, Mg, Mn, and Ni, preferably a soft ferrite containing two or more, for example, copper-zinc-magnesium ferrite. Sintered ferrite particles, especially spherical particles are preferred.

Since these magnetic carrier particles show little change in electrical resistance due to environmental changes or changes over time, they exhibit stable charging properties, and the magnetic brush has soft ears.
It is advantageous in that it does not generate white streaks such as a trace of a magnetic brush on the formed image. The average particle size of the magnetic carrier is generally 30 to 200 μm.
, Especially 50 to 150 μm, and the saturation magnetization is 30 to 70 emu / g, especially 45 to 65
emu / g and volume resistivity of 10 ^{5 to} 10 ⁹ Ω · c
m, especially in the range of 10 ^{6 to} 10 ⁸ Ω · cm.

Further, the magnetic carrier particles can be used by coating them with various kinds of thermoplastic resins or thermosetting resins with the core as a core. For example, as the thermoplastic resin, there is a thermoplastic acrylic resin, a thermoplastic styrene-acrylic resin, a polyester resin, a polyamide resin, an olefin copolymer resin, or the like, and as the thermosetting resin, a modified or unmodified silicone resin, Examples include thermosetting acrylic resin, thermosetting styrene-acrylic resin, phenol resin, urethane resin, thermosetting polyester resin, epoxy resin, amino resin, fluororesin, and melamine resin. With such a resin coat, the occurrence of spent can be more effectively avoided. Generally speaking, the amount of resin coating is preferably 0.001 to 2.5 parts by weight, and more preferably 0.005 to 2.0 parts by weight, based on 100 parts by weight of the core particles.

In the present invention, it is preferable to introduce a cationic polar group into the above coating resin. That is, by providing the resin coating layer having a cationic polar group, the positive charging property of the carrier is improved, and thus the negative charging property of the toner can be further improved. Such cationic polar groups include basic nitrogen-containing groups such as primary, secondary or tertiary amino groups, quaternary ammonium groups, amide groups, imino groups, imide groups, hydrazino groups,
Typical examples are guanidino group and amidino group, and amino group and quaternary ammonium group are particularly preferable.

The introduction of the cationic polar group may be carried out, for example, by producing the resin using the above-mentioned monomer having a cationic group as a monomer component, and by using a silane coupling agent having a cationic group. It can also be introduced by subjecting the resin to a surface treatment. As such a silane coupling agent, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N- Phenyl-γ-aminopropyltrimethoxysilane and the like. Furthermore, the cationic polar group can be introduced into the resin by synthesizing the above coated resin by polymerization using a polymerization initiator having a cationic polar group such as an amidine type azobis compound. The amount of these cationic polar groups is generally in the range of 0.1 to 2000 mmol, particularly 0.5 to 1500 mmol, per 100 g of resin.

It is of course possible to add various additives known per se, such as silica, alumina, carbon black, fatty acid metal salts, silane coupling agents and silicone oil, to the resin coating layer, if necessary. Is.

The resin coating of the carrier particles to be the core is
It can be carried out by a method known per se, for example, by dissolving the above-mentioned coat resin in a suitable solvent and using this resin solution, a dipping method, a spray method, a fluidized bed method, a moving bed method, a rolling bed method, etc. Thus, resin coating can be performed. When the thermosetting resin is coated, the resin may be cured by heating or the like after the coating is performed by the above method using a solution of an uncured resin or an oligomer.

In the present invention, it is also possible to use a binder type carrier formed by dispersing magnetic powder in a binder resin. As such a magnetic powder, the above-mentioned magnetic powder, particularly magnetite, can be preferably used, and the particle size thereof is 2.0 μm or less, particularly 0.05 to 1.0 μm.
It should be in the range of. This magnetic powder is a binder resin 100
150 to 900 parts by weight, especially 250 to 6 parts by weight
It is preferably used in an amount of 00 parts by weight.

As the binder resin, a thermoplastic resin,
Examples of thermosetting resins in the form of uncured or initial condensate, such as vinyl aromatic resins such as polystyrene, acrylic resins, polyvinyl acetal resins, polyester resins, epoxy resins, phenol resins, petroleum resins, polyolefin resins, etc. it can. Among these, styrene resins, acrylic resins, and styrene-acrylic copolymer resins are preferable.

The binder type carrier may be blended with auxiliaries known per se, such as carbon black for controlling electric resistance, dispersants, dispersion auxiliaries, charge control agents of low molecular weight or high molecular weight. it can. Similarly to the above, a cationic polar group may be introduced to enhance the positive charging property of the carrier and improve the negative charging property of the toner. Even in such a binder type carrier, the average particle size and the like are preferably in the same range as the above-mentioned carrier.

(Two-Component Magnetic Developer) The toner of the present invention is used as a magnetic developer by being mixed with the above-mentioned various magnetic carriers, and the mixing ratio of these carriers and the toner is generally 98. : 2 to 90:10 weight ratio, especially 97: 3 to 94: 6 weight ratio.

(Organic Photoreceptor) The development using the above-mentioned developer is applied to the development of the electrostatic latent image formed on the organic photoreceptor. Such organic photoreceptors include a single layer dispersion type and a laminated type.

As the single-layer dispersion type organic photoreceptor, for example, as shown in FIG. 10A, a photosensitive layer 12 in which a charge generating substance is dispersed in a charge transport medium is provided on a conductive tube 10. The ones are typical. Also, as a laminated type photoreceptor,
As shown in FIG. 10B, a charge generation layer (CGL) 12a is formed on the conductive tube 10, and the charge generation layer 12a is formed.
It is typical that the charge transport layer 12b is provided on the top. On the contrary, there is also one in which a charge transport layer is provided on the base tube 10 and a charge generation layer is provided on this charge transport layer. Any of these organophotoreceptors can be used in the present invention.

As the charge generating substance contained in the above-mentioned photosensitive layer, any organic photoconductive pigment known per se can be used. For example, photoconductive organic pigments such as phthalocyanine pigments, perylene pigments, quinacridone pigments, pyranthrone pigments, disazo pigments and trisazo pigments can be used alone or in combination of two or more kinds.

As the charge transport medium, a resin medium in which a charge transport substance is dispersed is used. As the charge transport substance, any hole transport substance or electron transport substance known per se is used. obtain.

Examples of suitable hole transport materials include 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 etc. can be illustrated.

Examples of suitable electron-transporting substances are 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, dinitroanthraquinone, 2,6-dimethyl-2 ', 6-ditert-butyldiphenoquinone Etc. can be illustrated.

Various resins can be used as the resin medium in which the above-mentioned respective agents are dispersed. For example, a styrene polymer, an acrylic polymer, a styrene-acrylic polymer,
Ethylene-vinyl acetate copolymer, polypropylene, olefin polymers such as ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin,
Polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin,
Various polymers such as polyvinyl butyral resin, polyether resin, and phenol resin, and photocurable resins such as epoxy acrylate can be used alone or in combination of two or more. Particularly suitable resins are styrene polymers, acrylic polymers, styrene-acrylic polymers, polyesters, alkyd resins, polycarbonates, polyarylates and the like.

The charge-generating substance to be present in the photosensitive layer is 0.1 to 50 parts by weight, especially 0.1 to 100 parts by weight of the binder resin.
It may be in the range of 5 to 30 parts by weight, while the charge transport material may be 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 preferably in the range of 10 to 40 μm, particularly 22 to 32 μm in view of high surface potential, printing durability and sensitivity.

As the conductive base pipe 10, an aluminum base pipe or an alumite-processed base pipe is generally used. Of course, the material is not limited to aluminum as long as it has conductivity, and a conductive resin or a conductive film can be used.

The photosensitive layer is formed by using a resin in a suitable solvent, for example, an amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide; a cyclic ether such as tetrahydrofuran or dioxane; dimethyl sulfoxide; benzene, toluene, An aromatic solvent such as xylene; a ketone solvent such as methyl ethyl ketone; N-methyl-2-pyrrolidone; a phenol solvent such as phenol or cresol; and a charge generating substance or the like dispersed therein to form a coating composition. It can be carried out by preparing, coating on a conductive drum-shaped substrate such as an aluminum tube, and drying.

(Image Forming Apparatus) In FIG. 11 showing an image forming apparatus for suitably carrying out the developing method of the present invention, this apparatus (indicated by 11 as a whole) has a rotatable photosensitive layer 12 formed on its surface. Organic photoconductor drum 13, photosensitive layer 1
2, a main charger 14 for uniformly applying a predetermined amount of electric charge to 2,
Optical device 15 for imagewise exposing photosensitive layer 12 to form an electrostatic latent image on the layer, developing device 16 for developing the electrostatic latent image to form a toner image, toner image formed Transfer device 18 for transferring the toner onto the recording paper 17, and a cleaning device 1 for removing the toner remaining on the photosensitive drum 13.
9 and a charge eliminating lamp 20 for removing charges remaining on the photosensitive drum 13 and setting the surface potential of the photosensitive drum 13 to a predetermined uniform potential.

That is, the above-mentioned developer is filled in the developing device 16, and the main charger 14 uniformly applies a predetermined amount of electric charge to the photosensitive layer 12, and then the optical device 15 is used to apply the photosensitive layer 1.
Reflected light from a document (not shown) is irradiated onto the image forming device 2 to form an electrostatic latent image on the photosensitive layer 12. The electrostatic latent image is developed by rubbing against the developer in the developing device 16 to form a visible toner 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 erased, and the photosensitive layer 1
The surface potential of 2 is equalized to a predetermined potential. On the other hand, the recording paper 17 on which the toner image is transferred is introduced into a fixing device (not shown), and the toner image is fixed by heat or the like,
This completes one cycle of image formation. These series of steps are performed according to the rotation of the photosensitive drum 13.

[0081]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

(Evaluation of Image) The following items were evaluated using the developers and the organic photoconductors prepared in the following Examples and Comparative Examples.

(A) Image density (ID): 50,000 copies were made using a character original having an area ratio of black area of 8%.
The density of the black solid part of the sampled image was measured every 5,000 sheets using a reflection densitometer (model number "TC-6D" manufactured by Tokyo Denshoku Co., Ltd.). The original used for sampling every 5,000 sheets has an area ratio of black portions including black solid portions of 15%.

(B) Fogging Density (FD) 50,000 copies were made using a character original having an area ratio of black area of 8%. The density of the black solid part of the sampled image was measured every 5,000 sheets using the same reflection densitometer as described above. The difference between this measurement value and the measurement value obtained by measuring the paper base paper before copying with a reflection densitometer was calculated, and the maximum value was calculated as the fog density (F.
D. ). Note that the original used to sample every 5,000 sheets has an area ratio of black areas including solid black areas of 15
%belongs to.

(C) Transfer efficiency: The amount of toner in the toner hopper before the start of copying and the amount 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 to obtain the amount of toner collected.
From these values, the transfer efficiency of toner was calculated by the following formula. The copy original used for copying was a character original having a black area ratio of 8%. Transfer efficiency (%) = [(A−B) / A] × 100 In the formula, A represents the toner consumption amount and B represents the toner recovery amount.

(D) Charge Amount 50,000 copies were made using a character original having an area ratio of black area of 8%. 200 mg of developer for every 5,000 copies
Was measured using a blow-off powder charge amount measuring device (manufactured by Toshiba Chemical Co., Ltd.) and shown as an average value of charge amount per 1 g of toner.

(E) Spent amount Copying is performed using a character original having an area ratio of black portion of 8%,
The developer was sampled when 50,000 sheets were copied.
This developer is placed on a 400-mesh screen and sucked from below by a blower to separate the toner from the carrier. 5 g of the carrier remaining on the sieve is put into a beaker, and toluene is further added to the beaker, and spent to dissolve the toner adhering to the surface of the carrier. Then, the toluene solution is dropped from under the beaker while the carrier is attracted by the magnet.
After repeating this several times until the toluene becomes colorless, the toluene is dried in an oven and the weight is measured. The difference between the weight put in the beaker and the weight after drying is the amount of spent. The amount of spent is expressed in mg of spent toner attached to 1 g of carrier.

(F) Toner Scattering Copying was performed using a character original having an area ratio of the black portion of 8%.
At the time of copying 50,000 sheets, the toner scattering state in the copying machine was visually observed and evaluated according to the following criteria. ○: No toner scattering ×: Toner scattering

(G) Filming of Organic Photoreceptor 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. ○: Without filming ×: With filming

Example 1 A copolymer resin containing units of styrene, butyl methacrylate and acrylic acid in a weight ratio of 70: 27: 3 is used as a fixing resin. This fixing resin has an acid value of 7 and a weight average molecular weight of 100,000.

The following components: 100 parts by weight of the fixing resin above 8 parts by weight of carbon black [pH: 3.5, (7-pH) / specific surface area (m ² / g):
0.025, acid treatment with nitric acid] 2 parts by weight of magnetite (magnetic powder) was melt-kneaded by a twin-screw extruder, and then this kneaded material was pulverized by a jet mill and classified by an air classifier to have a size of 10.0 μm.
Particles were obtained. To 100 parts by weight of the particles, 0.3 part by weight of hydrophobic silica fine particles having an average particle diameter of 0.015 μm was externally added as a fluidity improving agent and mixed by a Henschel mixer to obtain a toner.

The surface-treated toner particles and the average particle size of 100
Toner concentration of 3.5
A weight% two-component developer was obtained.

A single-layer type photosensitive layer of the following composition (film thickness 30 μm
Was formed on an aluminum drum having an outer diameter of 30 mm to prepare an organic photoconductor drum.

Photosensitive layer composition: Bisazo pigment represented by the following chemical formula: 10 parts by weight 3,3′-dimethyl-N, N, N ′, N′-tetrakis-4-methylphenyl (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

[0095]

Embedded image

FIG. 11 with this organic photosensitive drum mounted.
Copier "DC-" manufactured by Sanda Kogyo Co., Ltd.
Copying was carried out using the above-obtained developer using a "4086" modified machine, and evaluation was made for each item described above. The results are shown in Table 1.

Example 2 A toner was prepared in the same manner as in Example 1 except that 0.5 part by weight of acrylic resin particles having an average particle size of 0.3 μm was further added as spacer particles. A copying experiment was conducted in the same manner as in Example 1 except that this toner was used, and the results are shown in Table 1.

(Comparative Example 1) As carbon black, p
H = 9, (7-pH ) / specific surface area ^{(m 2 / g) = -} 0.
A toner was prepared in exactly the same manner as in Example 1 except that 013 which was not treated with an acid was used. A copying experiment was conducted in the same manner as in Example 1 except that this toner was used,
The results are shown in Table 1.

Comparative Example 2 A styrene-acrylic copolymer resin (acid value: 0) containing styrene and butyl methacrylate units in a weight ratio of 70:30 was used as a fixing resin. A toner was prepared in the same manner as in Example 1. A copying experiment was conducted in the same manner as in Example 1 except that this toner was used, and the results are shown in Table 1.

(Comparative Example 3) A toner was prepared in the same manner as in Example 1 except that 2 parts by weight of an azo chromium complex salt dye was blended per 100 parts by weight of the fixing resin as a charge control agent.
A copying experiment was conducted in the same manner as in Example 1 except that this toner was used, and the results are shown in Table 1.

[0101]

[Table 1]

The spacer particles used in Example 2 were
The charge control agent used in Comparative Example 3 was an azo-type chromium complex salt dye, which was an acrylic resin of 3 μm. All uncoated ferrite is used as the carrier. I
D, FD, charge amount and transfer efficiency are shown as an average of 50,000 sheets.

As is clear from the results of Table 1, Examples 1 to 1
In the development of No. 2, toner scattering was effectively prevented and the transfer efficiency was good, but in Comparative Example 1, toner scattering and a decrease in transfer efficiency were observed, and in Comparative Example 2, a decrease in transfer efficiency was observed. In Example 3, filming was recognized together with toner scattering and reduction in transfer efficiency.

[0104]

According to the present invention, a copolymer resin having an anionic polar group is used as a fixing resin medium,
PH as carbon black to be dispersed in resin medium
Is less than 7 and the ratio of (7-pH) / specific surface area is 0.01
By developing with a two-component developer containing a toner in which 0 to 0.050 is dispersed, the charging performance of the toner can be stabilized for a long period of time, and the life of the toner and the carrier is extended. Can be converted. Further, although the toner is not blended with a negative charge control agent, it is possible to secure a sufficient toner charge amount for development. Further, according to the developing method of the present invention, toner contamination on the surface of the organic photoreceptor is effectively prevented and filming is effectively prevented, so that stable development can be performed for a long period of time.

[Brief description of drawings]

Figure 1: Chromium complex salt dye (2: 1 type) as charge control agent
3 is an absorbance curve at a wavelength of 200 to 700 nm of an extraction liquid obtained by extracting a toner containing a toner with methanol.

FIG. 2 Wavelength 200 to 700 nm of a methanol extract of toner using a salicylic acid metal complex as a charge control agent.
It is an absorbance curve in.

FIG. 3 is a diagram showing the carrier used in the measurement of FIG. 1 as a two-component magnetic developer, and a carrier in which a charging failure has occurred due to spent is similarly extracted with methanol, and the absorbance of this extract at a wavelength of 200 to 700 nm. It is the graph which measured the curve.

FIG. 4 is a graph plotting the relationship between the mixing time and the amount of charge when a mixture of a toner containing a positive charge control agent and a magnetic carrier and a mixture of a toner containing no charge control agent and a magnetic carrier are mixed. Is.

FIG. 5 is a graph plotting the relationship between the mixing time and the charge amount when a mixture of a toner containing a negative charge control agent and a magnetic carrier and a mixture of a toner not containing a charge control agent and a magnetic carrier are mixed. Is.

FIG. 6 is a graph showing the relationship between the amount of spent spent carrier and the amount of charge control agent in spent toner.

FIG. 7 is a graph showing the relationship between the mixing time and the charge amount when the individual components in the toner are mixed with the magnetic carrier.

FIG. 8 is an explanatory diagram illustrating the occurrence of charging failure due to spent generation in a conventional two-component magnetic developer.

FIG. 9 is an absorbance curve at a wavelength of 200 to 700 nm in an extract obtained by extracting the negatively chargeable toner of the present invention with methanol.

FIG. 10 is a diagram showing a typical layer structure of an organic photoreceptor used in the present invention.

FIG. 11 is a diagram showing an example of an image forming apparatus for suitably implementing the developing method of the present invention.

Front page continuation (72) Inventor Asano Terumichi 1-22 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Co., Ltd. (72) Hideaki Kawada 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Engineering Incorporated (72) Inventor Tadao Sumiyoshi 1-22 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Tomohide Iida 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. Within

Claims (5)

[Claims] 1. An electrostatic charge image formed on an organic photoreceptor,
A method of developing using a two-component developer containing at least a magnetic carrier and a toner, wherein the toner contains a fixing resin and toner particles containing carbon black dispersed in the resin, The fixing resin is a composition containing a resin having a free or neutralized anionic polar group, and the carbon black has a pH of less than 7 and (7-p
H) / specific surface area (m ² / g) is 0.010 to 0.05
0 to 4 and 1 to 4 per fixing resin medium
A developing method characterized in that it is blended in an amount of 5% by weight. 2. The developing method according to claim 1, wherein the extract obtained by extracting the toner with methanol has a substantially zero absorbance in the wavelength region of 400 to 700 nm and no absorption peak in the region of 280 to 350 nm. 3. The developing method according to claim 1, wherein the fixing resin medium has an acid value of anionic polar groups measured in the form of a free acid in the range of 4 to 30. 4. The developing method according to claim 1, wherein 0.1 to 5 parts by weight of magnetic powder is dispersed in the fixing resin per 100 parts by weight of the resin. 5. 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.