JP2663020B2 - Electrostatic image developer and electrostatic image developing method - Google Patents

Description

The present invention relates to an electrostatic image used for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, or the like. The present invention relates to a developer, and an electrostatic image developing method for developing an electrostatic latent image formed on the surface of a photoconductor made of an organic photoconductive semiconductor using the electrostatic image developer. The present invention relates to an electrostatic image developer and an electrostatic image developing method suitable for developing a negative electrostatic latent image formed on the surface of a photoconductor made of a conductive semiconductor.

[Prior Art] In general, in electrophotography, after a uniform electrostatic charge is applied to a photoreceptor having a photosensitive layer made of a photoconductive material, image exposure is performed to form an electrostatic latent on the surface of the photoreceptor. An image is formed, and the electrostatic latent image is developed with a developer to form a toner image. The obtained toner image is transferred onto a transfer material such as paper, and then fixed by heating or pressing to form a copied image.

Examples of the photoconductive material used for forming the photosensitive layer of the photoconductor include inorganic photoconductive materials such as selenium, zinc oxide, and cadmium sulfide; and organic photoconductive materials such as polyvinyl carbazole or other high molecular weight compounds or low molecular weight compounds. And the like are known.

Of these, an organic photoreceptor having a photosensitive layer formed of a polymer photoconductive material represented by polyvinyl carbazole has a better film-forming property than an inorganic photoreceptor, so that the photoreceptor can be manufactured at low cost. And has the advantage of not being toxic to the human body, and has been attracting attention in recent years. On the other hand, the sensitivity is low, and the durability is inferior because it is easily deteriorated early in the corona charging step or the exposure step. ,
In addition, the sensitivity or charge retention ability is liable to change depending on the environmental conditions, so that it is still inferior to a photoreceptor having a photosensitive layer made of an inorganic photoconductive material, and the development of a high-performance photoconductive material is desired. I have.

On the other hand, in order to overcome the above problems, it has recently been proposed to use a low molecular weight organic photoconductive material. Since a low-molecular-weight organic photoconductive material generally has good dispersibility in a binder resin, the resulting photosensitive layer has the organic photoconductive material uniformly dispersed in fine particles, and as a result, the sensitivity is reduced. A relatively high photoreceptor can be obtained, and a photosensitive layer is formed by dispersing an organic photoconductive material in a binder resin, so that a film forming property is improved, and therefore, a photoreceptor is manufactured with high productivity. In addition, there are many types of low molecular weight photoconductive materials that can be used, and therefore, by using a suitably selected low molecular weight photoconductive material, it is possible to obtain a photoconductor having better performance than before. It is possible. in this way,
An organic photoreceptor having a photosensitive layer formed of a low molecular weight organic photoconductive material is more preferable than a conventional photoreceptor.

However, since the organic photoconductive material usually shows photoconductivity due to the movement of a positive charge, the organic photoconductive material is formed on the surface of an organic photoreceptor having a photosensitive layer formed of the organic photoconductive material. It is preferable that the polarity of the electrostatic latent image is negative. In order to develop a negative electrostatic latent image, it is necessary to use a developer having a positively charged toner.

However, in the case of a photoreceptor having a photosensitive layer made of selenium or the like, which has been widely used in the past, the polarity of the electrostatic latent image formed on the surface thereof is positive. A developer having a negatively charged toner is used, and therefore, research and development of a developer having a negatively charged toner has been performed considerably. However, as described above, a positively charged developer used for developing an organic photoreceptor is used. Research and development of a developer having a toner has been delayed, and a developer having a sufficiently positively charged toner has not been obtained.

On the other hand, as a method for developing an electrostatic latent image, a wet development method and a dry development method are known. The former wet developing method has a problem of emitting a bad smell because a liquid developer is used,
Another problem is that high energy is required to dry the transfer material and high-speed copying is difficult. The latter dry developing method does not have such a problem and can be preferably used as a method for developing an electrostatic latent image.

As a developer used in the dry development method, a so-called one-component developer composed of only a magnetic toner containing a magnetic substance and a so-called two-component developer composed of a non-magnetic toner containing no magnetic substance and a magnetic carrier are used. A system developer is known.

Since the former one-component developer does not have a carrier consisting of only magnetic toner, it is used to regulate a slight frictional charging between the toners and a height of the toner and a developing sleeve or a developer layer disposed in a developing device. The toner is charged by friction charging with a regulating blade or the like. As a result, both positively charged toner and negatively charged toner are present, and the amount of frictional charging is small, so development is basically unstable. There is a problem that it is easy to become. Specifically, for example, the toner also adheres to the non-image portion on the photoconductor,
There is a problem that fog occurs in the final fixed image, or the amount of toner adhering to the image portion on the photoreceptor becomes insufficient and the density of the final fixed image decreases.

Further, the magnetic material used in the magnetic toner generally has a hydrophilic property, and the hydrophilic magnetic material is often contained in a state where the surface of the toner particles is exposed to light. Charges are liable to leak, and in a high-humidity atmosphere, in the transfer process, electrostatic transfer to a transfer sheet generally used as a transfer material becomes defective, and the transfer rate of the toner to the transfer sheet becomes low. As a result, there is a problem that the density of the final fixed image is reduced. Further, since the magnetic material used in the magnetic toner usually has a negative chargeability,
It is difficult to charge the magnetic toner positively with an appropriate amount of charge, so there is a large percentage of toner of opposite polarity,
Eventually, there is a problem that the density is reduced in the final fixed image and image unevenness occurs.

On the other hand, the latter two-component developer is composed of a toner and a carrier, and the carrier has a function of charging the toner to a desired polarity. The amount of the triboelectric charge can be imparted to the developer, and it is possible to obtain a developer having a remarkably superior triboelectric property as compared with the above-mentioned one-component developer. In addition, by selecting a carrier having desired characteristics, the charge amount of the toner can be controlled to a considerable extent.

However, in order to obtain a good final fixed image, it is not sufficient that only the triboelectricity of the developer is good, and the particles of the triboelectrically charged developer are aggregated in the developing device. Without being transferred to the developing space in good condition.

That is, in the case of a two-component developer, when the toner is easily aggregated by agglomeration due to electrostatic aggregation, it becomes difficult to disperse the toner particles in the carrier particles at a uniform concentration. The ratio of the toner having a low triboelectric charge decreases due to a decrease in the triboelectric chargeability between the toner and the carrier.
In addition, since a large amount of weakly charged toner is present, the electrostatic adhesion between the toner and the carrier is reduced. Therefore, in the magnetic brush developing method, the toner particles adhered to the carrier particles are rotated while rotating by magnetic force. When transported to the development space, the toner particles are scattered by the centrifugal force of the rotation of the carrier particles, and consequently contaminate various devices such as a charger and an exposure optical system arranged in the copying machine, and finally fix. There is a problem that an image defect such as image unevenness occurs in an image.

In conventional negatively charged toners, silica fine particles having a smaller diameter than the toner particles are mixed with the toner particles so that the silica fine particles adhere to the surface of the toner particles, thereby preventing the toner from clumping. High fluidity has been achieved.

However, conventionally used silica fine particles have a strong negative chargeability. Therefore, when a positively chargeable toner is obtained, if the silica fine particles are mixed with the toner and adhered to the surface of the toner particles, the obtained toner is negatively charged. There is a problem in that the toner is charged, and as a result, it has the same polarity as the negative electrostatic latent image formed on the photoconductor, so that electrostatic development cannot be performed.

Under such circumstances, research and development of positively-chargeable fine particles have recently been promoted, but it has been found that there is a new problem here.

That is, the positively chargeable inorganic fine particles are mixed with the toner and held in a state of being adhered to the toner particles, and are mixed with the carrier particles and agitated, so that the toner has a positive friction. Although a charged charge is applied, the carrier of iron powder particles is used in the conventional two-component developer, so that when the toner and the carrier are stirred in the developing device, the surface of the toner particles The positively charged inorganic fine particles adhered to the surface of the carrier particles are transferred to the surface of the carrier particles by physical or electrostatic adhesion, and the amount of the transfer increases each time the carrier is used repeatedly. As a result, the frictional charging characteristic between the toner and the carrier changes, the amount of the toner having a weak charge increases, and the amount of the toner having the opposite polarity, that is, the negative charge increases. , Fog, a phenomenon in which part of an image is missing (image loss), a phenomenon in which a difference in shading appears in the image (image unevenness), a phenomenon in which the density of the peripheral portion of the image decreases (image blur), and a band-like shading in the image There is a problem that a phenomenon (image blurring) in which the difference appears appears and the image becomes unclear.

Further, when an image is formed many times, the positive chargeability of the toner is remarkably reduced, and as a result, the image density is low and the image becomes unclear at an early stage, and the durability of the developer is low.

In addition, since the toner having a weak charge amount or the toner having the opposite polarity is easily scattered, this causes contamination of the inside of the apparatus,
As a result, there is a problem that the image becomes dirty and the image becomes unclear.

As a method for solving such a drawback, Japanese Patent Application Laid-Open No.
No. 60 as a carrier copper, a carrier consisting of magnetic particles having zinc and iron as essential components, and as a toner,
A method using a toner containing a styrene-acrylic copolymer has been proposed. According to this method, most of the above-mentioned problems can be solved, but when the original having a low image area ratio under low humidity is repeatedly copied for a long period of time, the positively chargeable inorganic fine particles can be solved. Is excessively charged and transferred to the surface of the resin-coated carrier due to electrostatic adhesion, and eventually causes the same problems as described above.

[Problems to be Solved by the Invention] The present invention has been made on the basis of the above-mentioned circumstances, and the objects thereof are as follows: (1) It has good positive chargeability, has a high image density, and has no fog. To provide an electrostatic image developer capable of stably forming an image of good image quality many times. (2) Stable good image regardless of environmental conditions (especially even in a low humidity environment). (3) A negative electrostatic latent image formed on an organic photoconductive photoreceptor can be favorably developed without scattering of toner. An electrostatic image developing method is provided.

[Means and Actions for Solving the Problems] The electrostatic image developer of the present invention comprises a carrier composed of magnetic particles containing copper, zinc and iron as essential components and an acid value of 2
It is characterized by containing a toner containing the following styrene-acrylic copolymer and carbon black treated with an amino-modified silicone oil.

The electrostatic image developing method of the present invention uses the electrostatic image developer to develop a negative electrostatic latent image formed on the surface of a photoconductor made of an organic photoconductive semiconductor by a contact type magnetic brush developing method. It is characterized by the following.

<Carrier> As the magnetic particles, particles made of ferrite containing copper and zinc can be preferably used.
Ferrite is a generic name of magnetic oxides containing iron, and among them, spinel ferrite represented by MO.Fe ₂ O ₃ (M is a divalent metal) can be preferably used. Ferrite has various magnetic properties and triboelectric charging properties by appropriately changing the composition of the contained metal component. Therefore, it is possible to select the ferrite having optimal properties in combination with the toner used in the present invention. . In addition, since ferrite is an oxide, its specific gravity is smaller and lighter than metal powder such as metal iron powder, so that it can be easily mixed and agitated with toner, and therefore the toner concentration in the developer can be easily uniform. As a result, the amount of triboelectric charge of the toner can be stabilized. Ferrite has a specific resistance usually in the range of 10 ³ to 10 ¹² Ωcm, which is higher than the specific resistance of metal powder such as metal iron powder. When applied, excellent developability is obtained.

Ferrite having a saturation magnetization σs of 45 to 75 emu / g in a magnetic field of 1000 Oe can be preferably used, and has a resistivity of 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω · c.
When m and the saturation magnetization s are too small, the carrier is easily developed (transferred together with the toner) on the photoconductor, and the photoconductor, the cleaning blade, the heat roller fixing device, and the like are easily damaged.

On the other hand, when the saturation magnetization σs is excessively large, it is difficult to form a uniform magnetic brush on the developing sleeve when applying the magnetic brush developing method, and as a result, the developability decreases and the image becomes unclear. There is.

The average particle size of the carrier is generally preferably from 30 to 110 μm, more preferably from 35 to 80 μm.
When the average particle size is less than 30 μm, the carrier is easily developed (transferred together with the toner) on the latent image holding member, and the latent image holding member and the cleaning blade are easily damaged. on the other hand,
If the average particle diameter of the carrier is larger than 100 μm, the toner retention ability of the carrier is reduced, and unevenness of a solid image, toner scattering, fogging and the like are liable to occur.

<Toner> The toner used in the present invention is a toner containing, as a constituent unit, a styrene-acrylic copolymer having an acid value of 2 or less. Basically, it is a particle powder constituted by containing a colorant and other additives in a binder made of the styrene-acrylic copolymer, and the average particle size is usually about 5 to 20 μm. It is preferred that Further, as other additives, for example, a fixing property improving agent, a charge control agent, a cleaning property improving agent and the like can be used.

The styrene-acrylic copolymer is basically,
It is a copolymer obtained from a styrene monomer and an acrylic monomer. The styrenic component can impart favorable releasability to the toner and improve the anti-offset property, and can harden the toner and provide a more favorable positive triboelectric charge due to friction with the carrier. , And as a result, a clear image with good developability and transferability can be obtained. Acrylic acid or an ester thereof and / or methacrylic acid and an ester component thereof can impart good fixability to the toner and form an image having excellent fixing strength.

The styrene-acrylic copolymer has a weight average molecular weight Mw of 50,000 to 1,000,000 and a number average molecular weight Mn of 2,0.
Those having a ratio Mw / Mn in the range of from 6.0 to 60, preferably from 00 to 40,000, can be preferably used.

Specific examples of the styrene monomer that can be used to obtain the styrene-acrylic copolymer include, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n -Decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene and the like. These monomers may be used alone or in combination of two or more.

Further, acrylic components that can be used to obtain the styrene-acrylic copolymer include, for example, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, N-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl methyl acrylate, methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate Alkenyl, dimethylaminoethyl methacrylate, such as diethylaminoethyl methacrylate α-
Methylene aliphatic monocarboxylic acid esters; acrylic acid or methacrylic acid derivatives; and others. These monomers may be used alone or in combination of two or more.

The method for producing the styrene-acrylic copolymer is not particularly limited, and various methods can be used. Specifically, for example, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like can be used.

The styrene-acrylic copolymer used in the present invention has an acid value of 2 or less, preferably 1 or less, particularly preferably 0.5 or less. If the acid value is excessive, the toner tends to be negatively charged, and proper positive chargeability cannot be obtained.

In the toner, any suitable pigment or dye can be used as a colorant. For example, known dyes and pigments such as carbon black, phthalocyanine blue, ultramarine, quinacridone, and benzidine yellow are used.

As charge control agents, amino compounds, quaternary ammonium compounds and organic dyes, particularly basic dyes and salts thereof, benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride,
Nigrosine base, nigrosine hydrochloride, safranin γ and crystal violet may be added.

A wax-like substance such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, carnauba wax, and sazol wax can be added in an amount of about 0.5 to 5% by weight for the purpose of improving the releasability at the time of hot roll fixing.

The configuration of the toner described above is based on the general mixing-
The toner may be used for a pulverized toner, or may be used for a microcapsule toner.

<Carbon Black> As the carbon black constituting one component of the developer in the present invention, those having a particle diameter of 10 to 70 μm can be preferably used, and among them, conductive furnace black and oil furnace black are particularly preferable.

As the silicone oil having an amine in a side chain used for the treatment of the carbon black, a silicone oil containing a structural unit represented by the formula (I) can be used.

(Where R ₁ represents a hydrogen, an alkyl group, an aryl group, or an alkoxyl group, R ₂ represents an alkylene group, or a phenylene group, and R ₃ and R ₄ represent a hydrogen, an alkyl group, or an aryl group However, the above-mentioned alkyl group, aryl group, alkylene group and phenylene group may contain an amine, or may have a substituent such as halogen as long as the chargeability is not impaired.) Among the silicone oils, the amine equivalent (a value obtained by dividing the molecular weight of the silicone oil by the number of amines per molecule by the equivalent per amine (g / eqiv.))
Less than 2000, especially less than 1000 is preferred, 25 ° C
Those having a viscosity of 100 cps or less are suitable for treating carbon black.

The amount of the silicone oil of the present invention to be added to carbon black is preferably 5 to 50 parts by weight with respect to 100 parts by weight of carbon black.

On the other hand, the applied amount of the treated carbon black of the present invention is effective when the amount is 0.01 to 10% by weight, particularly preferably 0.05 to 3% by weight with respect to the developer. A chargeable developer is obtained.

In the present invention, the values of Mw and Mn were calculated from the values measured by gel permeation chromatography. Measurement conditions are as follows: tetrahydrofuran is flowed as a solvent at a temperature of 25 ° C. at a flow rate of 1 ml per minute, and 0.5 ml of a tetrahydrofuran sample solution having a sample concentration of 8 mg / ml is injected. In order to accurately measure the molecular weight region of 10 ³ to 2 × 10 ⁶ , it is preferable to combine a plurality of commercially available polystyrene gel columns, for example, μ-styr manufactured by waters.
agel500,10 ³ , 10 ⁴ , 10 ⁵ combination and Showa Denko shodex
A-802, 803, 804, 805 combination is good. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Che
mical Co. or Toyo Soda Kogyo Co., Ltd. has a molecular weight of 6 × 1
0 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9
It is suitable to use those of × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ and at least about 10 standard polystyrene samples. An RI (refractive index) detector is used as the detector.

In the present invention, the value of the acid value is a value expressed in mg of potassium hydroxide required to neutralize 1 g of a sample, and is measured as follows. 2 g of the soluble component is dissolved in 200 g of a mixed solvent of toluene / ethanol = 2/1, and titrated with a 0.1 N potassium hydroxide solution using phenolphthalein as an indicator.

<Developing Method> Next, the electrostatic image developing method of the present invention will be described.

In the electrostatic image developing method of the present invention, the negative electrostatic latent image formed on the surface of the organic photoreceptor is treated with the specific carrier as described above, the specific toner as described above, and an amino-modified silicone oil-treated carbon. The toner image is formed by developing with a specific electrostatic image developer containing black particles.

Examples of the organic photoreceptor used in the present invention include those using an organic photoconductive polymer such as polyvinyl carbazole and those using a low molecular weight organic photoconductive substance as an insulating polymer as a binder. Of these, a laminated photoreceptor comprising a charge transport layer and a charge generation layer is preferably used in the present invention, but the charge generation layer is preferably an azo pigment such as Sudan Red, Diane Blue, or Dienas Green B, argol yellow, or pyrenequinone. , Quinone pigments such as indanthrene brilliant violet RRP,
Quinocyanine pigments, perylene pigments, indigo, indigo pigments such as thioindigo, bisbenzimidazole pigments such as India First Orange toner, phthalocyanine pigments such as copper phthalocyanine, charge-generating substances such as quinacridone pigments, polyester, polystyrene, polyvinyl butyral, polyvinyl It is formed by dispersing in a binder resin such as pyrrolidone, methylcellulose, polyacrylates, and cellulose esters. Its thickness is 0.
It is preferably about 01 to 1 μ, preferably about 0.05 to 0.5 μ.

In addition, the charge transport layer has an anthracene, pyrene, phenanthrene, polycyclic aromatic compound such as coronene or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiadiazole in the main chain or side chain,
A compound having a nitrogen-containing cyclic compound such as triazole,
It is formed by dissolving a hole transporting substance such as a hydrazone compound in a film-forming resin. This is because the charge transporting substance generally has a low molecular weight and is poor in film forming property by itself. Such resins include polycarbonate, polymethacrylates, polyarylate, polystyrene, polyester, polysulfone, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, and the like. The thickness of the charge transport layer is 5 to 20
μ is preferred. As the resin constituting the surface layer of the photoreceptor such as the charge transport layer, properties such as abrasion resistance and oil lubrication are also important, but are measured by DSC as a resin in order to effectively achieve the object of the present invention. Tg at peak position is 60 ° C
The temperature is preferably 80 ° C. or higher.

 FIG. 1 shows an example of the developing device used in the present invention.

In FIG. 1, reference numeral 1 denotes an organic photoreceptor, 2 denotes a developing sleeve, which is made of a nonmagnetic material such as aluminum, for example, and has a multipolar magnet 3 disposed therein.
By rotating at least one of the sleeve 2 and the multipolar magnet 3, the developer 4 is transported in the direction of the arrow,
The developer 4 is regulated by the blade 5 to form a developer layer 6. Due to the magnetic force of the multipolar magnet, the developer layer 6 is in a state in which the developing particles stand in a brush shape (magnetic brush). The developer layer 6 on this sleeve is a developing section,
It is set so as to contact the photoconductor 1. A DC or AC bias voltage may be applied between the sleeve 2 and the photoconductor 1. Reference numeral 7 denotes a cleaning blade, which is used to scrape and remove the developer remaining on the developing sleeve 2 after development. Reference numeral 8 denotes a developer accommodating portion, and 9 denotes a stirring screw, and the toner and the carrier constituting the developer 4 are uniformly mixed. Of the developer 4, the carrier is used repeatedly, whereas the toner is consumed every time the toner is developed. Therefore, new toner is supplied from the toner hopper 10 through the mesh toner supply opening 12 by the toner conveying member 11. The developer is supplied to the developer container 8.

FIG. 2 shows an example of a specific image forming apparatus which can be used when forming an image by applying the developer and the developing method of the present invention, but this does not limit the present invention at all.

A process for forming an electrostatic latent image on the photoconductor 1 will be described. The primary charger 29 to form a is not latent image formed on the photosensitive member 1 by the irradiation with the reflected light I _A lens group 26 and reflecting mirrors 25 and the document 21 after charging the photosensitive member 1 with a halogen lamp 24.

The latent image thus formed is simultaneously developed by the developing device 31 using the above-described developing process, and is visualized. Photoconductor 1
The toner image formed thereon is transferred to a transfer material 38 by an electrostatic transfer separation charger 35, and then the transfer material 38 is separated from the photoreceptor 1 and fixed to a fixing device.
Fix at 37 to obtain an image. The photoreceptor 1 cleans the transfer residual toner with a blade cleaner 33 and performs a pre-exposure lamp.
Static electricity is removed at 28 and used repeatedly.

As described above, according to the image forming means, the amino-modified silicone oil-treated carbon black particles impart a suitable release property to the developer, and also prevent the developer from being excessively charged, Low physical adhesion of developer to organic photoreceptor surface. For this reason, in the transfer step, good transfer can be performed by the electrostatic transfer means, and a clear image with high image density and no image unevenness can be reliably formed.

In addition, since the transferability of the developer is good, the amount of the developer remaining on the organic photoreceptor after the transfer step becomes small. Therefore, in the cleaning step, the remaining developer is easily cleaned, The presence of the modified silicone oil-treated carbon black particles reduces the adhesion of the developer to the surface of the organic photoreceptor for the same reason as described above, so that the developer can be easily cleaned.

In addition, since the cleaning property of the developer is good, good cleaning can be achieved in a state in which the pressure of the cleaning blade against the organic photoreceptor is small, so that the surface of the organic photoreceptor is worn by the cleaning blade. As a result, the characteristics of the organic photoconductor are prevented from being deteriorated at an early stage, and the service life of the organic photoconductor can be significantly prolonged.

In the fixing step, the amino-modified silicone oil-treated carbon black particles are interposed between the surface of the molten developer and the heat roller, so that a releasing effect can be obtained. Due to the property, the charging of the surface of the fixing roller to the negative polarity is prevented, so that the transfer of the developer to the heat roller is prevented, and as a result, the image stain due to the offset development can be prevented.

[Example] Example 1 The mixture was melted and kneaded in a twin-screw rudder heated to 150 ° C and then cooled.
The material was coarsely crushed to a degree passing through a 1 mm wire mesh, and then finely crushed to about 10 μm by a wind crusher / jet mill. This finely pulverized product was classified by an air classifier Alpine 100MZR classifier so that the volume average particle diameter became 11 to 13 μm, to prepare a positively charged black powder.

On the other hand, while stirring vigorously 100 parts by weight of conductive furnace black having a particle size of about 30 mμ, the amine equivalents 700, 25
A liquid obtained by diluting 15 parts by weight of a silicone oil having an amine in a side chain having a particle size of 50 cps at a temperature of 50 ° C. 4 times with xylene is sprayed. Further, the temperature of the stirring tank is raised to about 280 ° C. while the stirring is continued, and is maintained for 2 hours. Thereafter, the mixture was cooled to obtain an amino-modified silicone oil-treated carbon black.

0.8 w of the above treated carbon black in the black powder
t% was added to obtain a toner.

Copper: zinc ferrite (Cu: Zn: Fe = 2) with an average particle size of 70 μm
0:20:60 (molar ratio), 100 parts by weight of electric resistance 5 × 10 ⁸ ohm · cm) and 6 parts by weight of the toner were mixed to prepare a developer.

This developer was applied to a color developing device of a copying machine NP-3725 (manufactured by Canon Inc.). In a normal environment, a clear image without fog was obtained, and the image reflection density was as high as 1.40.

In addition, to examine the durability of the developer under low humidity, 20
When 100,000 copies were repeatedly made using a 2% original image area original in an environment of 5 ° C and 5% RH, an image with the same high quality and high image density as the initial one was obtained. No toner scattering inside, poor cleaning, stain on the fixing roller, stain on the image due to offset, etc. did not occur at all.

Further, even under a high temperature and high humidity environment (30 ° C., 90 RH%), a clear image without fog was obtained, and the image reflection density was as high as 1.36.

In addition, good transferability was exhibited under any environment, and no image dropping and scattering of line drawings were observed.

Comparative Example 1 A developer was obtained in the same manner as in Example 1, except that the amino-modified silicone oil-treated silica black treated in the same manner was used instead of the amino-modified silicone oil-treated carbon black of Example 1. This developer was evaluated in the same manner as in Example 1.

Although there was no problem in a normal environment, in a repeated copying test in a low humidity environment, the image density was lowered after about 30,000 sheets, and fogging and toner scattering occurred.

Example 2 100 parts by weight of oil furnace black having a particle size of about 20 mμ were treated in the same manner as in Example 1 with 20 parts by weight of a silicone oil having an amine equivalent of 1100 and a viscosity of 65 cps at 25 ° C. having an amine in the side chain. .

A developer was obtained in the same manner as in Example 1, except that the above treated carbon black was used instead of the treated carbon black used in Example 1. When this developer was evaluated in the same manner as in Example 1, good results were obtained as in Example 1.

Example 3 100 parts by weight of oil furnace black having a particle diameter of about 60 mμ were treated in the same manner as in Example 1 by using 20 parts by weight of a silicone oil having an amine equivalent of 500 and a viscosity of 25 cps at 25 ° C. having an amine in a side chain. .

A developer was obtained in the same manner as in Example 1, except that the above treated carbon black was used instead of the treated carbon black used in Example 1. When this developer was evaluated in the same manner as in Example 1, good results were obtained as in Example 1.

Example 4 As a carrier, copper / zinc ferrite having an average particle size of 60 μm (Cu: Zn: Fe = 25: 15: 60 (molar ratio), electric resistance = 2 × 10
^A developer was obtained in the same manner as in Example 1, except that ⁸ ohm · cm) was used. When this developer was evaluated in the same manner as in Example 1, good results similar to those in Example 1 were obtained.

[Effects of the Invention] According to the electrostatic image developer of the present invention, a toner containing a carrier composed of magnetic particles containing copper, zinc and iron as essential components and a specific copolymer, and an amino-modified silicone Since it contains oil-treated carbon black, the synergistic action of these makes it possible to reliably impart a positive and proper amount of triboelectric charge to the toner,
As a result, it is possible to stably form an image with high image density and good image quality without fog many times. In addition, since good positive triboelectricity of the toner can be obtained stably without being affected by environmental conditions, images having high image density and good image quality without fog can be obtained many times even under high humidity environment conditions. It can be formed stably.

Further, even when a document having a low image area ratio is repeatedly copied for a long period of time under a low-humidity environment, an image with high image density and good image quality without fog can be stably formed many times.

That is, since the acid value of the styrene-acrylic copolymer contained in the toner is 2 or less, the tendency of the toner to have a negative charge is small, and the toner has good positive frictional charge.

Further, since the styrene-acrylic copolymer contained in the toner generally has hard properties, the physical adhesion of the toner is small, and as a result, the toner can be sufficiently uniformly dispersed and mixed in the carrier. , A stable triboelectric charge can be provided with a high probability.

Further, since the toner contains a styrene-acrylic copolymer, the carbon black particles treated with the amino-modified silicone oil have high adhesion to the toner particles. The carbon black particles treated with the modified silicone oil are stably held by the toner particles, and the toner exhibits excellent triboelectric charging properties stably.

As described above, the toner has a positive triboelectric charging property, and the electrostatic image developer contains carbon black particles treated with an amino-modified silicone oil. Become good. Furthermore, since the particles treated with amino-modified silicone oil are carbon black, the surface of the particles is low even when the electrical resistance is low and the original image with a low image area ratio is repeatedly charged and copied under excessively low humidity conditions. In this case, the excess charge generated is not accumulated, and the proper charge amount is maintained. Therefore, the carbon black particles treated with the amino-modified silicone oil continue to be stably held on the surface of the toner particles. Also, the charge amount of the toner itself is stably maintained at an appropriate value.

Moreover, since the carrier is composed of magnetic particles containing copper, zinc and iron as essential components, the fluidity and surface properties of the carrier particles are improved, and therefore, the carbon black treated with the amino-modified silicone oil adheres to the carrier particles. Is less likely to occur, and the toner substance is less likely to adhere to the carrier particles. As a result, a good positive triboelectric charging property of the toner is stably exhibited for a long period of time.

In addition, the carrier composed of magnetic particles containing copper, zinc and iron as essential components has a stable triboelectrification property even when environmental conditions change, so that the toner is stable to toner even under high humidity environmental conditions. A triboelectric charge can be imparted, and an excellent developer with little environmental dependency can be obtained.

Further, since the electrostatic image developer of the present invention is formed by combining a specific carrier, a specific toner and specific fine particles, it is possible to immediately apply an appropriate triboelectric charge to the toner by a slight stirring in a developing device. Therefore, even when an image is formed intermittently, a good image can be formed without fogging or deterioration in image quality caused by insufficient toner charge.

According to the electrostatic image developing method of the present invention, a negative magnetic layer formed on the surface of an organic photoconductor, that is, a photoconductor made of an organic photoconductive semiconductor by a contact-type magnetic brush developing method using the specific developer as described above. The negative electrostatic latent image formed on the organic photoreceptor is prevented from scattering toner particles without deteriorating the advantage of the organic photoreceptor that the production cost is low and there is no toxicity. Good development can be achieved without such a problem. That is, since the specific developer has an excellent positive charging property, the specific developer is positively charged with an appropriate charge amount, so that the carrier particles and the toner particles form a uniform brush on the developing sleeve. The developer layer (magnetic brush) of such a form is carried in a lined thin layer form, and the developer layer (magnetic brush) of such a form is stably conveyed to the developing space while maintaining such form. Generation can be prevented.

In addition, the presence of carbon black particles treated with an amino-modified silicone oil imparts excellent fluidity to the developer, so that a uniform and uniform magnetic brush can be formed on the developing sleeve. Good development can be achieved using the brush development method.

After all, according to the developer and the developing method of the present invention, fogging does not occur, and image unevenness, image blur, image blur,
It is possible to stably form a clear, high-quality image without image blurring many times without being affected by environmental conditions.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a developing device used in the present invention, and FIG. 2 is an example of an image forming device that can be used when forming an image by applying the developer and the developing method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1 ... Organic photoreceptor, 2 ... Developing sleeve 3 ... Multipolar magnet, 4 ... Developer 5 ... Regulator blade, 6 ... Developer layer 21 ... Document 33 ... Blade cleaner 35 ... Static Electrotransfer separation zone electricity 37 .... Heat roller fuser

Continuation of front page (56) References JP-A-62-182759 (JP, A) JP-A-55-26518 (JP, A) JP-A-2-219063 (JP, A) JP-A-63-71862 (JP, A) JP-A-63-174060 (JP, A) JP-A-63-169658 (JP, A) JP-A-62-52564 (JP, A) JP-A-61-2755863 (JP, A) 63-169660 (JP, A)

Claims (2)

(57) [Claims] 1. A treatment comprising a carrier comprising magnetic particles containing copper, zinc and iron as essential components, a toner containing a styrene-acrylic copolymer having an acid value of 2 or less, and an amino-modified silicone oil. An electrostatic image developer characterized in that the developer comprises a carbon black. 2. An electrostatic image developer according to claim 1, wherein
An electrostatic image developing method comprising developing a negative electrostatic latent image formed on the surface of a photoconductor made of an organic photoconductive semiconductor by a contact type magnetic brush developing method.