JPH04116567A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To obtain the developer which does not flaw the surface of a photosensitive body and does not generate a cleaning defect by constituting the developer of a negatively charged magnetic toner contg. <=70wt.% magnetic powder treated with a surface treating agent consisting of a silane coupling agent, titanium coupling agent or negatively charged polymer and a magnetic carrier. CONSTITUTION:The developer is constituted of the negatively charged magnetic toner which is higher in the triboelectrostatic charge quantity measured by a blow off method to a negative side than -50muc/g and contains <=70wt.% mag netic powder treated with the surface treating agent consisting of the silane coupling agent, the titanium coupling agent or the negatively charged polymer and the magnetic carrier. Namely, the magnetic powder having the specific triboelectrostatic charge quantity is incorporated into the magnetic toner by the surface treating agent and, therefore, the adhesion of the magnetic powder eliminated at the time of production of the magnetic toner to the surface of the magnetic toner is prevented. The electrophotographic developer which obviates ground fogging, the splashing of the magnetic toner to printing image parts, the flawing of the surface of the photosensitive body, and the cleaning defect is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic developer used for developing electrostatic latent images formed by electrophotography, electrostatic recording, electrostatic printing, etc. Regarding.

[Conventional technology]

Conventionally, there have been two types of development methods used in image forming devices such as copying machines and printers: a one-component development method that uses only magnetic toner, and a two-component development method that uses a mixture of non-magnetic toner and carrier, which is magnetic particles, as a developer. Are known.

Since there is no carrier in the one-component development method, toner density control is not required (and a device to detect toner density is not required for this purpose. However, since the developer consists only of toner, toner aggregation may occur. I had a problem.

In addition, if the magnetic toner has a low resistance, there is a problem that the transfer efficiency is poor and the transferred image is distorted.If the magnetic toner has a high resistance, the magnetic toner is developed into an electrostatic latent image on the photoreceptor and transferred onto the transfer sheet. There has been a problem in that the edges of the line image become rough or smudge because the induced charges remain in the development area on the photoreceptor even after the line image has been developed. In addition, the doctor gap, which regulates the spikes of magnetic toner on the surface of the developing roll, and the developing gap, which is the distance between the developing roll and the photoreceptor, must both be set to extremely small values of around 0.1 to 0.2 m. Therefore, high processing accuracy of the device is required for the doctor gap and the development gap.

On the other hand, in the two-component development method, there is no need to reduce the values of the doctor gap and development gap in the -component development method. Toner density control was required.

Therefore, in order to improve the problems of the magnetic toner and two-component developer used in the conventional one-component development method, we developed a magnetic toner containing dispersed magnetic powder and a magnetic carrier as a developer with excellent developability and transferability. A developer consisting of a mixture of

However, the conventionally proposed developer comprising a magnetic toner and a magnetic carrier is still insufficient in practical use, and has the following problems. In other words, magnetic toner is generally produced by melting, kneading, and then crushing and classifying the desired materials. Normally, all of the magnetic powder in magnetic toner manufactured by this manufacturing method would not be contained in the magnetic toner. must be maintained. However, with conventional magnetic toners, a part of the magnetic powder is detached from the kneaded material during the pulverization process, and the detached magnetic powder becomes charged during the pulverization and classification process, causing a large amount to adhere to the surface of the magnetic toner due to electrostatic force. It was happening.

If magnetic toner with magnetic powder attached to the surface is used as a developer by mixing it with a magnetic carrier, it may cause smearing, scattering of magnetic toner on the image area, scratches on the surface of the photoreceptor, and poor cleaning. was causing problems.

[Problem to be solved by the invention]

The present invention was made in view of the problems of conventional electrophotographic developers consisting of magnetic toner and magnetic carrier, and it prevents detached magnetic powder from adhering to the magnetic toner.
It is an object of the present invention to provide a developer which is free from ground blur, scattering of magnetic toner on image areas, scratches on the surface of a photoreceptor, and poor cleaning.

[Means to solve the problem]

In the present invention, the amount of triboelectric charge measured by the blow-off method is -
70% by weight of magnetic powder that is higher on the negative side than 50pc/g and has been treated with a surface treatment agent consisting of a silane coupling agent, a titanium-based camping agent, or a negatively charged polymer.
This is an electrophotographic developer characterized by comprising a negatively charged magnetic toner and a magnetic carrier as described below.

The present invention will be explained in detail below.

The magnetic powder used in the present invention includes metals such as cobalt, iron, and nickel, aluminum, cobalt, copper, iron, nickel,
Magnesium, tin, zinc, gold, silver, selenium, titanium,
Tungsten, zirconium, alloys of other metals, metal oxides such as aluminum oxide, iron oxide, nickel oxide, ferromagnetic ferrite, magnetite, or mixtures thereof, and the surface of the magnetic powder is treated with a surface treatment agent. be.

The surface treatment agent is one that makes the amount of triboelectric charge of the magnetic powder negative, and among silane coupling agents and titanium coupling agents, those having a functional group that exhibits negative chargeability are preferably used. can. Specific examples include T-chloropropyltrimethoxysilane, T-glycidoxypropyltrimethoxysilane, β-(3,4epoxycyclohexyl)ethyltrimethoxysilane, and alkylchlorotitanium coupling agents.

Other surface treatment agents include those in which a negatively charged polymer such as a copolymer of vinylidene fluoride and tetrafluoroethylene is mixed with a crosslinking agent.

The method of treating the surface of magnetic powder with a surface treatment agent is -
This is often done by boat fishing, for example, stirring the magnetic powder and adding a solution of a surface treatment agent little by little to treat it, or vaporizing and blowing a surface treatment agent or its solution onto the magnetic powder in the gas phase. There are ways to attach it. Further, it is preferable to chemically bond the surface treating agent or to perform a hardening treatment using heat or the like so that the surface treating agent is not removed from the surface of the magnetic powder during the kneading process during magnetic toner production.

The amount of triboelectric charge of the magnetic powder treated with the surface treatment agent in the present invention needs to be higher than -50 μc/g on the negative side in order to prevent detached magnetic powder from adhering to the surface of the magnetic toner. . Its mechanism of action is as follows.

In other words, magnetic toner is exposed to high temperature environmental conditions (35°C).
/85%RH) In order to obtain stable triboelectric charging properties, it is common to include a charge control agent. Therefore, we use magnetic powder that has almost the same negative charge characteristics as magnetic toner containing a negatively chargeable charge control agent. This prevents electrostatic adhesion between magnetic toner and magnetic powder.

Incidentally, the magnetic powder that does not adhere to the magnetic toner is collected as fine powder by a bag filter during classification.

If the amount of triboelectric charge is lower than -50 μC nog on the positive side or if it has positive chargeability, the detached magnetic powder will adhere to the magnetic toner, which will worsen ground braking, toner scattering, and scratches on the photoreceptor. .

In the present invention, the amount of triboelectric charge of the magnetic powder is measured by a blow-off method, and specifically, it is measured as follows. First, as the material to which the magnetic powder is triboelectrically charged, ferrite powder whose surface is coated with 1 to 2% by weight of methyl methacrylate polymer is used.

The ferrite powder has an average particle diameter of 45 to 51 μm, a saturation magnetization of 60 to 65 elIlu/g, a residual magnetization and a coercive force of 0, an apparent specific gravity of 2.10 to 2.20 g/cj, and a fluidity of 26. 0 to 30.0 sec150g, current value is 45 to 51 μA, and specifically, the product name F141-300 manufactured by Powdertic Co., Ltd. is used to measure the amount of triboelectric charge of magnetic powder specified in the present invention. applied to.

As a measurement method, the above resin coated ferrite powder 49
Put 1 g of magnetic powder passed through a 200 mesh sieve into a 200 cc glass container and heat at 20-22°C/6.
Leave it in an environment of 0 to 65% for 12 hours or more. Next, after shaking this glass container 200 times by hand, it was stirred for 5 minutes using a constant speed stirrer at 80 rpm, and the amount of frictional charge of the magnetic powder was measured three times using a blow-off measuring device. Let it be the amount of triboelectric charge.

The magnetic toner constituting the present invention can be obtained by tri-blending a binder resin, a colorant, a charge control agent, etc. with the above-mentioned magnetic powder, melting and kneading the mixture, and then crushing and classifying the mixture. in this case,
The content of magnetic powder in the magnetic toner must be 70% by weight or less; if the magnetic powder is contained in an amount greater than 70% by weight, an extremely large amount of magnetic toner will be detached during the production of the magnetic toner, and the magnetic toner will It is not possible to prevent magnetic powder from adhering to the surface of the photoreceptor, resulting in smearing, toner scattering, and damage to the photoreceptor.

As the binder resin, homopolymers of styrene and its substituted products, such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, and copolymers thereof; ;Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid-
Copolymers of styrene and acrylic esters such as n-butyl copolymers; styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-ethyl methacrylate copolymers,
Copolymers of styrene and methacrylic esters such as n-butyl methacrylate copolymers; multi-component copolymers of styrene and acrylic esters and methacrylic esters;
Other styrenes such as styrene-acrylonitrile copolymer, styrene vinyl methyl ether copolymer, styrene butadiene copolymer, styrene vinyl methyl ketone copolymer, styrene acrylonitrile indene copolymer, styrene-maleic acid ester copolymer, etc. and other vinyl monomers; polymethyl methacrylate, polybutyl methacrylate, polyester resin,
Polyvinyl acetate polyester, polyamide resin, epoxy resin, polyvinyl butyral, polyacrylic acid phenol resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin,
Chlorinated paraffin, etc. can be used alone or in combination.

As the coloring agent, for example, the following pigments or dyes can be used. Carbon black, aniline blue (C,1
, N1150405), Calco Oil Blue (C01,
Nazoec Blue 3), Chrome Yellow (C, I.

Nα14090), Ultramarine Blue (C,1, 77103), DuPont Oil Red (C,1, Nα2
6105), Orient Oil Red #330 (C
, 1, Nil 47005), Methylene Blue Chloride (C, 1, Nα52015), Phthalocyanine Blue (C, 1, Nα 74160), Malachite Green Oxalate (C, 1, No, 42000), Lamp Black (C, 1, No. , 77266) , O-
Zubengali (C, I.

Nα45435) and mixtures thereof.

Other examples of charge control agents that can be used include metal-containing complexes of zinc and chromium, chlorinated paraffins, chlorinated polyesters, polyesters with excess acid groups, and sulfonylamines such as copper phthalocyanine.

On the other hand, the magnetic carrier constituting the developer of the present invention is -g
Those used as magnetic carriers for toner can be used. Specifically, iron powder carriers and ferrite carriers can be used, and polyester resins, fluorine resins, and It is also possible to use a resin-coated carrier whose surface is coated with acrylic resin, silicone resin, etc., or a so-called resin carrier obtained by kneading iron powder or ferrite with a binder resin and granulating it.

The developer of the present invention is produced by mixing 10 to 40 parts by weight of toner with 100 parts by weight of the carrier.

〔Example] Next, the present invention will be specifically explained using examples.

Example 1 was mixed, melt-kneaded in a twin-screw kneader, cooled, pulverized and classified to produce fine particles with an average particle diameter of 12 μm. 6% by weight and 0.4% by weight of hydrophobic silica (R-972 manufactured by Aerosil) were mixed using a Henschel mixer to obtain a magnetic toner.

Next, the magnetic toner was mixed with 30% by weight and an average particle size of 501.1 m.
The developer of the present invention was obtained by mixing with 70% by weight of acrylic coated magnetite.

The amount of triboelectric charge measured by the blow-off method of the magnetite a was -150 μc/g.

A commercially available copying machine (JX manufactured by Sharp Co., Ltd.) using the above developer
-9500) and evaluated the printing durability up to 5000 sheets, the image density measured by the Maches reflection densitometer was 1.
The value fluctuates between 3 and 1.35, and the soil strength blur measured by the color difference meter is 0.
．． 4 to 0.6, there was no scattering of magnetic toner to the image area, and no scratches occurred on the photoreceptor. In addition,
In order to confirm the state of adhesion of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after manufacture was observed under an electron microscope, and it was found that there was almost no adhesion of magnetic powder.

Example 2 The method of the present invention was carried out in the same manner as in Example 1 except that magnetite b (EPT-1000 manufactured by Toda Kogyo Co., Ltd., surface-treated with T-glycidoxypropyltrimethoxysilane) was used instead of magnetite a. A developer was obtained. The amount of triboelectric charge measured by the blow-off method of the above magnetite b was -55 μc/g.

A commercially available copying machine (JX manufactured by Sharp Co., Ltd.) using the above developer
-9500) and evaluated printing durability up to 5000 sheets, the image density remained at a value of 1.3 to 1.37, and the ground force blur was 0.4 to 0.5. There was no scattering of magnetic toner on the line areas, and no scratches occurred on the photoreceptor. In order to confirm the adhesion state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after manufacture was observed under an electron microscope, and it was found that there was almost no adhesion of magnetic powder.

Comparative Example 1 A comparative developer was obtained in the same manner as in Example 1, except that magnetite C (EPT-1000 manufactured by Toda Kogyo Co., Ltd., surface-treated with hexamethylene disilazane) was used instead of magnetite a. The amount of triboelectric charge measured by the blow-off method of the above magnetite C was -10 μc/g.

A commercially available copying machine (JX manufactured by Sharp Co., Ltd.) using the above developer
-9500) and evaluated printing durability up to 5000 sheets, the image density remained at a value of 1.25 to 1.3, and the ground force blur was 0.8 to 1.6. There were many scatterings of magnetic toner on the line parts and scratches on the photoreceptor. Furthermore, when the magnetic toner was observed under an electron microscope immediately after production, a large amount of magnetic powder was found to be attached to the surface.

Comparative Example 2 A comparative developer was obtained in the same manner as in Example 1, except that magnetite d (manufactured by Toda Kogyo Co., Ltd., EPT-1000), which had not been surface-treated, was used instead of magnetite a.

The amount of triboelectric charge measured by the blow-off method of the magnetite ld was +65 μc/g.

A commercially available copying machine (JX manufactured by Sharp Co., Ltd.) using the above developer
-9500) and evaluated the printing durability up to 5000 sheets, the image density remained at a value of 1.25 to 1.3, and the soil blur was 1.0 to 1.5. There was a lot of magnetic toner scattering and scratches on the photoreceptor. Furthermore, when the magnetic toner was observed under an electron microscope immediately after production, a large amount of magnetic powder was found to be attached to the surface.

Example 3 was mixed, melt-kneaded in a twin-screw kneader, cooled, pulverized and classified to produce fine particles with an average particle diameter of 12 μm, and hydrophobic silica was added to 99.6% by weight of the fine particles. (R-972 manufactured by Aerosil) 0.4% by weight was mixed using a Henschel mixer to obtain a magnetic toner. Next, 85% by weight of the magnetic toner and 15% by weight of acrylic coated magnetite having an average particle diameter of 50 μm were mixed to obtain a developer of the present invention.

Incidentally, the amount of triboelectric charge measured by the blow-off method of the above magnet tie a) was -150 μc/g.

When the above developer was installed in a commercially available printer (NEC PC-PR406LM) and the printing durability was evaluated for up to 5000 sheets, the image density remained at a value of 1.35 to 1.4. The soil strength was 0.3 to 0.5, there was no scattering of magnetic toner on the image area, and there were no cleaning defects. In order to confirm the adhesion state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after production was observed under an electron microscope, and no magnetic powder was found to be attached.

Example 4 Development of the present invention was carried out in the same manner as in Example 3, except that magnetite b (EPT-1000 manufactured by Toda Kogyo Co., Ltd., surface-treated with T-glycidoxypropyltrimethoxysilane) was used instead of magnetite a. obtained the drug. The amount of triboelectric charge measured by the blow-off method of the above magnetite b was -55 μc/g.

When the above developer was installed in a commercially available printer (NEC PC-PR406LM) and the printing durability was evaluated for up to 5000 sheets, the image density was 1.35 to 1.37.
The ground force blur was 0.4 to 0.6, there was no scattering of magnetic toner on the image area, and there were no cleaning defects. In order to confirm the adhesion state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after manufacture was observed under an electron microscope, and it was found that there was almost no adhesion of magnetic powder.

Comparative Example 3 A comparative developer was obtained in the same manner as in Example 3, except that magnetite C (EPT-1000 manufactured by Toda Kogyo Co., Ltd., surface-treated with hexamethylene disilazane) was used instead of magnetite a. . The amount of triboelectric charge measured by the blow-off method of the above Magnetite C was -10 pc/g. Using the above developer, it was installed in a commercially available printer (PC-PR406LM manufactured by NEC Corporation), and it could withstand up to 5000 sheets. When we performed printing evaluation, the image density was 1.35 to 1.35.
The ground force blur was 0.4 to 0.6, there was a lot of magnetic toner scattering on the image area, and cleaning failures occurred after 500 sheets. Furthermore, when the magnetic toner was observed under an electron microscope immediately after production, a large amount of magnetic powder was found to be attached to the surface.

Comparative Example 4 A comparative developer was obtained in the same manner as in Example 3, except that magnetite d (manufactured by Toda Kogyo Co., Ltd., EPT-1000) without surface treatment was used instead of magnetite a. The amount of triboelectric charge measured by the blow-off method of the above magnetite d was +65 μc/g.

When the above developer was installed in a commercially available printer (NEC PC-PR406LM) and the printing durability was evaluated for up to 5000 sheets, the image density was 1.34 to 1°37.
The ground force blur was 0.4 to 0.6, there was a lot of magnetic toner scattering on the image area, and cleaning failures occurred after 250 sheets. Furthermore, when the magnetic toner was observed under an electron microscope immediately after production, a large amount of magnetic powder was found to be attached to the surface.

〔Effect of the invention〕

As described above, in the present invention, since magnetic powder having a specific amount of triboelectric charge is contained in a magnetic toner using a surface treatment agent,
It is possible to prevent the magnetic powder detached during the production of magnetic toner from adhering to the surface of the magnetic toner, thereby preventing ground force blur, scattering of magnetic toner on the image area, scratches on the photoreceptor surface, and poor cleaning. It is possible to provide an electrophotographic developer that is

hand Continued Supplementary Positive book Heisei 3 years January 30th

Claims (1)

[Claims] The amount of triboelectric charge measured by the blow-off method is -50μc/
Negatively chargeable magnetic toner containing 70% by weight or less of magnetic powder treated with a surface treatment agent consisting of a silane coupling agent, a titanium coupling agent, or a negatively chargeable polymer, which is higher on the negative side than g, and magnetic An electrophotographic developer characterized by comprising a carrier.