JPH0786698B2 - Electrophotographic developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic developer used for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like. Regarding

[Conventional technology]

Conventionally, as a developing method in an image forming apparatus such as a copying machine and a printer, there are a one-component developing method using only a magnetic toner and a two-component developing method using a mixture of a non-magnetic toner and a carrier which is a magnetic particle as a developer. Are known.

In the one-component developing method, since there is no carrier, it is not necessary to control the toner density, and therefore a device for detecting the toner density is not necessary. However, since the developer is composed of only toner, there is a problem that toner aggregation occurs. Further, when the magnetic toner has a low resistance, there is a problem that the transfer efficiency is poor and the transferred image is disturbed, and when the magnetic toner has a high resistance, the magnetic toner is developed into an electrostatic latent image on the photoconductor and transferred onto the transfer sheet. There is a problem that the edges of the line image are roughened or bleeding occurs due to the residual electric charges induced in the developing area on the photoconductor even after the removal. Further, the doctor gap for controlling the bristling of the magnetic toner on the surface of the developing roll and the developing gap, which is the distance between the developing roll and the photoconductor, both have to be set to an extremely small value of around 0.1 to 0.2 mm. High processing accuracy of the device was required for the doctor gap and the development gap.

On the other hand, the two-component developing method does not require a smaller doctor gap and developing gap value than the one-component developing method. Therefore, a high processing accuracy of the apparatus for the doctor gap and the developing gap is not required, but the toner in the developer is not required. Concentration control was needed.

Therefore, in order to improve the problems of the magnetic toner and the two-component developer used in the conventional one-component developing method, a magnetic toner containing magnetic powder dispersed therein and a magnetic carrier are used as a developer having excellent developability and transferability. A developer composed 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. That is, a magnetic toner is generally produced by melt-kneading a desired material and then pulverizing and classifying, and originally, the magnetic powder of the magnetic toner produced by such a production method is all contained in the magnetic toner. Must be However, in the conventional magnetic toner, a part of the magnetic powder is desorbed from the kneaded product during the pulverization process, and the desorbed magnetic powder is charged during the pulverization and classification process and a large amount is attached to the surface of the magnetic toner by electrostatic force. It was happening.
When magnetic toner with magnetic powder adhered to the surface is mixed with a magnetic carrier and used as a developer, background fog, scattering of magnetic toner to image area, scratch on photoconductor surface, cleaning failure Was causing problems.

[Problems to be solved by the device]

The present invention has been made in view of the problems of the conventional electrophotographic developer comprising a magnetic toner and a magnetic carrier, which prevents detached magnetic powder from adhering to the magnetic toner, and has a background fog. It is an object of the present invention to provide a developer which is free from magnetic toner scattering on image areas, scratches on the surface of a photoreceptor, and cleaning failure.

[Means for Solving the Problems]

In the present invention, the triboelectric charge amount measured by the blow-off method is −
Negatively chargeable magnetic toner having a magnetic powder higher than 50 μc / g on the negative side and containing 70% by weight or less of magnetic powder treated with a surface treatment agent composed of a silane coupling agent, a titanium coupling agent or a negatively chargeable polymer. And a magnetic carrier, which is a developer for electrophotography.

Hereinafter, the present invention will be described in detail.

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

As the surface treatment agent, one that makes the triboelectric charge amount of the magnetic powder negatively chargeable, and among silane coupling agents and titanium coupling agents, those having a functional group exhibiting negative chargeability are preferably used. it can. Specifically, γ-chloropropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4 epoxycyclohexyl)
Examples include ethyltrimethoxysilane and alkylchlorotitanium coupling agents.

Further, as another surface treatment agent, there is also a mixture of a negatively chargeable polymer such as a copolymer of vinylidene fluoride and tetrafluoroethylene and a crosslinking agent.

The method of treating the surface of the magnetic powder with the surface treatment agent may be a general method, for example, stirring the magnetic powder and then adding a solution of the surface treatment agent little by little to the treatment, or in a gas phase. Then, there is a method in which the surface treatment agent or its solution is vaporized and sprayed onto the magnetic powder. Further, it is preferable to chemically bond the surface treatment agent so that the surface treatment agent is not removed from the surface of the magnetic powder in the kneading step during the production of the magnetic toner, or to carry out an effect treatment by heat or the like.

The triboelectric charge amount of the magnetic powder treated with the surface treatment agent in the present invention needs to be higher than -50 μc / g to the negative side in order to prevent the detached magnetic powder from adhering to the surface of the magnetic toner. . The mechanism of action is as follows. That is, for magnetic toner, high temperature and high humidity environment conditions (35 ° C / 85% R
In H), a charge control agent is generally contained in order to obtain stable triboelectric chargeability. Therefore, a magnetic powder having substantially the same negative charging characteristics as the magnetic toner containing the negatively chargeable charge control agent is used, and the magnetic toner and the magnetic powder repel each other in the air flow in the pulverizing and classifying process. The magnetic toner and the magnetic powder are prevented from electrostatically adhering.

The magnetic powder that has not adhered to the magnetic toner is collected as fine powder by a bag filter during classification.

If the amount of triboelectricity is lower than -50 μc / g on the positive side or if it has a positive charging property, the detached magnetic powder adheres to the magnetic toner, causing ground fog, toner scattering, and damage to the photoconductor. .

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

The ferrite powder has an average particle size of 45 to 51 μm, a saturation magnetization of 60 to 65 emu / g, a remanent magnetization and a coercive force of 0, an apparent specific gravity of 2.10 to 2.20 g / cm ³ , and a fluidity of 26.0 to 30.0 sec / 50 g. The current value has a physical property value of 45 to 51 μA. Specifically, the trade name F141-300 manufactured by Powder Tech Co., Ltd. is applied to the measurement of the triboelectric charge amount of the magnetic powder specified in the present invention.

As a measuring method, 49 g of the above resin-coated ferrite powder
And 1g of magnetic powder that passed through a 200-mesh sieve are put in a 200cc glass container and left in an environment of 20-22 ° C / 60-65% for 12 hours or more. Then shake this glass container by hand 200 times, stir for 5 minutes in a constant speed stirrer at 80 rpm, measure the triboelectric charge amount of the magnetic powder three times with a blow-off measuring device, and calculate the average value of the magnetic powder The amount of triboelectric charge.

The magnetic toner constituting the present invention can be obtained by dry blending the above-mentioned magnetic powder with a binder resin, a colorant, a charge control agent, etc., melt-kneading, and then pulverizing and classifying. in this case,
The content of the magnetic powder in the magnetic toner must be 70% by weight or less. If the magnetic powder is contained in an amount of more than 70% by weight, the amount of the magnetic toner detached during the production of the magnetic toner becomes extremely large, and It is impossible to prevent the magnetic powder from adhering to the surface, and the fog on the ground, toner scattering, and scratches on the photoconductor become worse.

Examples of the binder resin include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, and styrene-vinyltoluene copolymer, and homopolymers of substitution products thereof, and copolymers thereof. Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid-
Copolymers of styrene and acrylic ester such as n-butyl copolymers; styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-methacrylic acid-n-butyl copolymers, etc. Copolymer of styrene and methacrylic acid ester; Multi-component copolymer of styrene and acrylic acid ester and methacrylic acid ester; Other styrene-acrylonitrile copolymer, styrene vinyl methyl ether copolymer, styrene butadiene copolymer, Styrene vinyl methyl ketone copolymer, styrene acrylonitrile indene copolymer, styrene-
Styrene-based copolymers of styrene and other vinyl-based monomers such as maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyester resins, polyvinyl acetate polyesters, polyamide resins, epoxy resins, polyvinyl butyral, polyacryl Acid phenol resins, aliphatic or alicyclic hydrocarbon resins, petroleum resins, chlorinated paraffins, etc. can be used alone or in combination.

As the colorant, for example, the following pigments or dyes can be used. Carbon black, aniline blue (CIN
o.50405), Calco Oil Blue (CINo.azoec Blue
3), Chrome Yellow (CINo.14090), Ultramarine Blue (CINo.77103), DuPont Oil Red (CINo.26105), Orient Oil Red # 330 (C.
I.No.47005), Methylene blue chloride (CI No.520
15), Phthalocyanine Blue (CINo.74160), Malachite Green Oxalate (CINo.42000), Lamp Black (CINo.77266), Rose Bengal (CINo.454)
35) and mixtures thereof.

Other charge control agents include zinc- and chromium-containing metal complexes, chlorinated paraffins, chlorinated polyesters, polyesters with excess acid groups, and copper phthalocyanine sulfonylamines.

On the other hand, as the magnetic carrier constituting the developer of the present invention, one generally used as a magnetic carrier for toner can be used, and specifically, an iron powder type carrier or a ferrite type carrier can be used, and , A resin-coated carrier whose surface is coated with a polyester resin, a fluorine resin, an acrylic resin, a silicone resin or the like using these as a core substance, or a resin carrier in which iron powder or ferrite is kneaded into a binder resin and granulated. Can also be used.

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

〔Example〕

 Next, the present invention will be specifically described with reference to examples.

Example 1 After mixing, melt-kneading with a twin-screw kneader, cooling, pulverizing and classifying to prepare fine particles having an average particle diameter of 12 μm, and 99.6% by weight of the fine particles of hydrophobic silica (R manufactured by Aerosil Co., Ltd. -972) 0.4 wt% was mixed using a Henschel mixer to obtain a magnetic toner, and then the magnetic toner
30% by weight and 70% by weight of acrylic-coated magnetite having an average particle diameter of 50 μm were mixed to obtain a developer of the present invention. The triboelectric charge amount of the magnetite a measured by the blow-off method was −150 μc / g.

Commercially available copying machine (JX-
9500) and evaluated printing durability up to 5,000 sheets, the image density measured by Macbeth reflection densitometer remained at 1.3-1.35, and the background fog measured by color difference meter was 0.4-0.6. The magnetic toner did not scatter to any part, and the photoreceptor was not scratched. In order to confirm the adhered state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after production was observed with an electron microscope, and it was found that the magnetic powder was hardly adhered.

Example 2 The development of the present invention was performed in the same manner as in Example 1 except that magnetite b (EPT-1000 manufactured by Toda Kogyo Co., Ltd. was surface-treated with γ-glycidoxypropyltrimethoxysilane) was used instead of magnetite a. I got an agent. The triboelectric charge amount of the magnetite b measured by the blow-off method is −55 μc /
It was g.

Commercially available copying machine (JX-
9500) and evaluated the printing durability of up to 5,000 sheets, the image density remained at 1.3 to 1.37 and the background fog was 0.4.
It was ˜0.5, and there was no scattering of the magnetic toner to the image area, and the photoconductor was not scratched. In order to confirm the adhered state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after production was observed with an electron microscope, and it was found that the magnetic powder was hardly adhered.

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., which had been surface-treated with hexamethylene disilazane) was used in place of magnetite a. The triboelectric charge amount of the magnetite c measured by the blow-off method was −10 μc / g.

Commercially available copying machine (JX-
9500) and evaluated the printing durability of up to 5000 sheets, the image density changed from 1.25 to 1.3 and the background fog was 0.8.
It was about 1.6, and there were many scattering of magnetic toner to the image area and scratches on the photoconductor. Further, when the magnetic toner immediately after the production was observed with an electron microscope, many magnetic powders were attached to the surface.

Comparative Example 2 A comparative developer was obtained in the same manner as in Example 1 except that magnetite d (EPT-1000 manufactured by Toda Kogyo KK) was used in place of magnetite a without surface treatment. The triboelectric charge amount of the above magnetite d measured by the blow-off method was +65 μc / g.

Commercially available copying machine (JX-
9500) and evaluated the printing durability of up to 5,000 sheets, the image density changed from 1.25 to 1.3 and the background fog was 1.0.
It was about 1.5, and there were many scatterings of magnetic toner to the image area and scratches on the photoconductor. Further, when the magnetic toner immediately after the production was observed with an electron microscope, many magnetic powders were attached to the surface.

Example 3 After mixing, melt-kneading with a twin-screw kneader, cooling, pulverizing and classifying to prepare fine particles having an average particle diameter of 12 μm, and 99.6% by weight of the fine particles of hydrophobic silica (R manufactured by Aerosil Co., Ltd. −972) 0.4 wt% was mixed using a Henschel mixer to obtain a magnetic toner. Next, the magnetic toner
85% by weight 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. The triboelectric charge amount of the magnetite a measured by the blow-off method was −150 μc / g.

A commercially available printer (manufactured by NEC Corporation) using the above developer
PC-PR406LM) and evaluated the printing durability of up to 5,000 sheets, the image density changed in the range of 1.35 to 1.4, the background fog was 0.3 to 0.5, and the magnetic toner on the image area was There was no scattering, and there was no cleaning failure. In addition,
In order to confirm the adhered state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after production was observed with an electron microscope, and it was found that the magnetic powder was hardly adhered.

Example 4 The present invention was developed in the same manner as in Example 3 except that magnetite b (EPT-100 manufactured by Toda Kogyo Co., Ltd. was surface-treated with γ-glycidoxypropyltrimethoxysilane) was used in place of magnetite a. I got an agent. Magnetite b above
The triboelectric charge amount measured by the blow-off method is -55 μc / g
Met.

A commercially available printer (manufactured by NEC Corporation) using the above developer
(PC-PR406LM) and evaluated printing durability up to 5,000 sheets, the image density changed in the range of 1.35 to 1.37, the background fog was 0.4 to 0.6, and the magnetic toner on the image area was There was no scattering, and there was no cleaning failure. In addition,
In order to confirm the adhered state of the detached magnetic powder to the magnetic toner, the magnetic toner immediately after production was observed with an electron microscope, and it was found that the magnetic powder was hardly adhered.

Comparative Example 3 A comparative developer was obtained in the same manner as in Example 3 except that magnetite c (EPT-100 manufactured by Toda Kogyo Co., Ltd., surface-treated with hexamethylene disilazane) was used instead of magnetite a. The triboelectric charge amount of the magnetite c measured by the blow-off method was −10 μc / g.

A commercially available printer (manufactured by NEC Corporation) using the above developer
PC-PR406LM) and evaluated printing durability up to 5,000 sheets, the image density remained in the range of 1.35 to 1.35, the background fog was 0.4 to 0.6, and the magnetic toner on the image area was There was a lot of splattering, and poor cleaning occurred on 500 sheets. Further, when the magnetic toner immediately after the production was observed with an electron microscope, many magnetic powders were attached to the surface.

Comparative Example 4 A comparative developer was obtained in the same manner as in Example 3 except that magnetite d (EPT-1000 manufactured by Toda Kogyo KK) was used in place of magnetite a instead of surface treatment. The triboelectric charge amount measured by the blow-off method of the magnetite d is +
It was 65 μc / g.

A commercially available printer (manufactured by NEC Corporation) using the above developer
(PC-PR406LM) and evaluated the printing durability of up to 5000 sheets, the image density remained in the range of 1.34 to 1.37, the background fog was 0.4 to 0.6, and the magnetic toner was scattered to the image area. There were many cases and poor cleaning occurred on 250 sheets. Further, when the magnetic toner immediately after the production was observed with an electron microscope, many magnetic powders were attached to the surface.

〔The invention's effect〕

As described above, the present invention contains the magnetic powder having a specific triboelectric charge amount in the magnetic toner by the surface treatment agent.
It is possible to prevent the magnetic powder detached during the production of the magnetic toner from adhering to the surface of the magnetic toner. Therefore, the background fog, the scattering of the magnetic toner to the image area, the scratch on the surface of the photoconductor, and the poor cleaning can be prevented. It is possible to provide a non-electrophotographic developer.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-57-161862 (JP, A) JP-A-57-124356 (JP, A) JP-A-54-84731 (JP, A) JP-A-58- 9153 (JP, A) JP 58-7646 (JP, A) JP 2-284154 (JP, A)

Claims (1)

[Claims] 1. A triboelectric charge amount measured by the blow-off method is higher than -50 μc / g on the negative side and treated with a surface treatment agent comprising a silane coupling agent, a titanium coupling agent or a negatively chargeable polymer. An electrophotographic developer comprising a negatively chargeable magnetic toner containing 70% by weight or less of magnetic powder and a magnetic carrier.