JPH0442233A - Conductive fine particle developer - Google Patents

Abstract

PURPOSE:To obtain the developer formed by a conductive fine particle toner having excellent fine line reproducibility, gradation characteristic, etc., for developing electrostatic latent images by mixing a specific toner and specific magnetic particles, thereby constituting the developer. CONSTITUTION:This developer is obtd. by mixing the toner having 0.5 to 5mum average grain size based on weight (average grain size) and about <= 1X10<10>OMEGAcm specific volume resistivity. The toner is obtd. by adding coloring agents, conduc tive particles, and other necessary fine particles, etc., to a binder resin, dissolv ing and kneading the mixture to disperse these components into the binder resin and adjusting the mixture to a desired grain size distribution by grinding and classifying after cooling. The magnetic particles may be the particles of magnetic materials, such as various kinds of magnetites, ferrites and hematites, themselves or may be the particles formed by dissolving and kneading the fine particles of these magnetic particles in and with a thermoplastic resin and grinding the mixture. Printed matter having high fineness and high grada tion characteristic is obtd. in this way.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides improvements in fine line reproducibility, gradation, etc. for developing electrostatic images in electrophotography, electrostatic recording, etc. This invention relates to a developer using an excellent conductive fine particle toner.

(Prior Art) Currently, the mainstream method for developing electrostatic images, such as electrophotography and electrostatic recording, which is widely used in copying machines, printers, etc., is dry development. is powder toner. There are two types of powder toner: insulating toner and conductive toner. Conductive toner has the following features compared to insulating toner.

■Since it does not utilize static charges caused by frictional charging, it can eliminate the effects of humidity.

2. Since the charge on the toner can be selected by the charge induced by the electrostatic latent image or by an arbitrary bias voltage, it is possible to perform more quantitative development than toner development using triboelectric charging, which improves halftone reproduction and dark areas. You can obtain images with excellent reproduction.

3. It becomes possible to select from a wider range of toner components such as resins, pigments, and additives.

4. Since a uniform charge can be applied to the toner, an image with excellent resolution and less background smudge can be obtained.

5. Since a frictional charging mechanism is unnecessary, the structure of the developing device is simplified and can be made smaller.

6. Both normal development and reverse development can be performed with the same toner.

7. Since the toner is conductive, it is easy to clean without static electricity.

8. Since it is only necessary to bring the conductive toner layer into contact with each other, development can be performed without toner scattering.

9. Toner fluidity is good, and agglomeration and bronking inside the developing device, clogging of the toner replenishing section, etc. are unlikely to occur.

On the other hand, toner is required to faithfully reproduce the electrostatic latent image, and for this purpose, the average particle size of toner must be small,
It is also necessary that the particle size distribution be uniform.

However, as the average particle size of the toner is reduced, the fluidity of the conductive toner as a powder deteriorates significantly, and when the average particle size is less than 5 μm, problems such as agglomeration and blocking occur inside the developing device. Something happened. In addition, conductive toner is generally developed using a magnetic l-component method, or
If fine toner with a weight-based average particle size of 5 μm or less is used in this method, close-packing occurs on the magnetic sleeve, resulting in significant toner aggregation, and no magnetic blur occurs, so it cannot be used for magnetic brush development. .

(Problems to be Solved by the Invention) The present invention solves the problem of agglomeration and blocking inside the developing device.
This makes it possible to obtain images with excellent fine line reproducibility, gradation, etc. using conductive toner with a weight-based average particle diameter of 5 μm or less, which could not be used due to poor magnetic brush formation. .

[Structure of the invention]

(Means for Solving the Problems) The present invention has a weight-based average particle size (hereinafter sometimes simply referred to as average particle size) of 0.5 μm to 5 μm and a volume resistivity of about l.
The present invention relates to a conductive fine particle developer characterized in that it is a mixture of a toner having a diameter of 1010 Ωcm or less and magnetic particles having a weight-based average particle diameter of 5 to 200 times that of the toner.

A typical method for obtaining the toner of the present invention is a pulverization method in which dyes, pigments, magnetic powders, etc. are melted in a binder resin, dispersed by kneading, mechanically pulverized after cooling, and then classified. . Further, it can also be produced by a production method other than pulverization, such as a spray drying method, an emulsion polymerization method, a suspension polymerization method, etc. The crusher used to obtain toner by the crushing method is preferably a jet mill that uses the pressure of compressed air, such as an air suction type, an air flow collision type, or a collision plate collision type, but other methods include a swing hammer. A high-speed rotating mill that uses impact, shearing, or grinding force, such as a mill, pin mill, turbo type mill, or centrifugal classification mill, may also be used.

The bread ider resin used in the above-mentioned pulverization method contains a thermoplastic resin having an Izod impact value of 5 kg cm/cm or less, in an amount of 70% or more of the total binder component, preferably 9096 or more. If less than this,
It is difficult to obtain fine particle toner by pulverization. The thermoplastic resin having an Izot impact value of 1.5 kg am/cnr or less may be selected from, for example, styrene resins, epoxy resins, rosin-modified polyester resins, thermoplastic phenolic resins, and the like. In order to improve the fixing properties and offset resistance of thermoplastic resins with an Izot impact value of 1.5 kgcm/c and below, acrylic resins, polyamide resins, polyvinyl acetate resins, hydrocarbon resins, petroleum resins, Chlorinated paraffin etc. and various waxes etc. can be blended.

The toner of the present invention contains various magnetic powders such as magnetite, ferrite, and hematite, charge control agents and dispersion aids such as metal-containing dyes, nigrosine dyes, and amine compounds, colorants, and dispersion aids.
It can be kneaded into a thermoplastic resin together with a charge control agent and the like.

In the present invention, carbon black is used as the colorant in the case of a black toner. In addition to carbon black, colorants include zinc white, yellow iron oxide, Hansa yellow disazo yellow, quinoline yellow, permanent yellow, permanent red, red iron, Lysole red, Wochan red calcium salt, Wochan I knot manganese salt, and pyrazolone red. Pigments or oil-soluble dyes such as Lake Red C, Lake Red D, Brilliant Carmine 6B, Brilliant Carmine 3B, Prussian Blue, Phthalocyanine Blue, and Titanium Oxide can be used.

When using a coloring agent other than carbon black, various metal oxides or simple metals such as tin oxide, zinc oxide, copper oxide, etc. are used in combination as the conductive substance. It is preferable that these conductive substances have an average primary particle diameter of about 0.3 μm or less.

The toner of the present invention is produced by adding a colorant, conductive particles, and other necessary fine particles to the binder resin, dispersing these components in the binder by melt mixing, cooling, crushing, and classifying to obtain a desired particle size distribution. It can be prepared and obtained. The average particle size of the toner is 0.5 μm to 5 μm, and substantially does not contain particles larger than 10 μm.

The conductive toner of the present invention has a volume resistivity of approximately 1×100Ω.
It is necessary that it be less than cm. The volume resistivity is measured by pressurizing toner with a strong pressure of 200 kg/cnf or more to produce a pellet, applying a voltage to both ends of the pellet, and calculating from the current value. If the volume resistivity of the toner exceeds about 1 x 10 Ωcm, it is not preferable because the advantages of the conductive toner are lost.

The developer of the present invention contains magnetic powder inside and is developed using a magnetic brush. In order to prevent agglomeration in the magnetic sleeve, magnetic particles having an average particle diameter of 1 to 5 times, preferably 10 times, more preferably 30 to 200 times, are mixed. If it is less than 5 times, it is not preferable because the magnetic particles cannot hold the toner particles on their surfaces, so that some of the toner particles coagulate with each other, and furthermore, the fluidity of the mixture deteriorates.

Examples of magnetic particles include particles of magnetic substances such as various magnetites, ferrites, hematites, etc., or particles obtained by melting and kneading fine powder of magnetic particles into a thermoplastic resin and pulverizing the particles. good.

In the former case, the spherical or amorphous magnetic particles may be used as they are, but their surfaces may also be coated with silicone resin, fluororesin, acrylic resin, or the like. Coating methods include heating or dissolving the resin in a solvent and then spraying it in a fluidized bath, and dipping coating.

In addition, in the case of magnetic particles obtained by melt-kneading fine magnetic particles into a thermoplastic resin and pulverizing them, the amount of magnetic material is 20 to 80% by weight of the whole.
6, preferably 40 to 70 weight 96. In addition, the volume resistivity of magnetic particles is approximately 1×1
It is desirable that the resistance is 0.010 Ωcm or more. If it is less than this, the force to restrain the magnetic particles or toner may be insufficient, resulting in toner scattering.

The mixing ratio of the toner to the magnetic particles is 0.1 to 10% by weight96, preferably 0.1 to 5% by weight96 to the toner to the magnetic particles.
It is 6. If the weight exceeds 10% by weight, the magnetic particles will not be able to completely hold the toner, even if it is a fine particle, and the toner will separate or aggregate together, and if it is less than 0.1% by weight, the toner will Since the amount is insufficient, it becomes impossible to obtain a sufficient image density of the printed matter.

The developer of the present invention is held in a sleeve or the like having a magnetic pole therein, and is visualized by bringing it into contact with an electrostatic charge image.

Either the toner must adhere to the electrostatic image or the magnetic particles must continue to remain on the sleeve. For this reason, the magnetic particles must have sufficient magnetic force (saturation magnetization) so as not to adhere to the electrostatic charge image, and the saturation magnetization is 20 emu/
It is desirable that the value be greater than g. The consumed 1.sup. is detected by, for example, a known magnetic sensor, image density sensor, etc., and mixed and supplied by a stirring mechanism.

(Functions and Effects of the Invention) For insulating toner, a developer mixed with magnetic particles having an average particle diameter of five times or more the toner is generally used.

In this method, the toner is held on the magnetic particles by the electrostatic charge of the insulating toner and the Coulomb force between the magnetic particles.

On the other hand, even if this method is applied to conventionally known conductive toner with a relatively large average particle size, the toner and magnetic particles may be separated because there is almost no attraction between them. Although this was completely unsuitable, it was found that when the average particle size of the conductive toner was 5 μm or less, particularly 3 μm or less, the toner was well retained on the magnetic particles and could be used as a mixture. The details of this holding force are not clear, but it decreases significantly as the toner particle size decreases, probably due to the influence of forces that separate toner and magnetic particles such as gravity and centrifugal force, whereas electrostatic force and van der Waals force decrease significantly as the toner particle size decreases. This is thought to be due to the relative increase in the influence of the binding force between the toner and the magnetic particles.

According to the present invention, it is now possible to use toner with an average particle size of 5 μm or less, which was previously unavailable due to problems such as agglomeration and blocking inside the developing device, and poor formation of magnetic brushes, resulting in high definition and high gradation. It is now possible to obtain printed matter.

The toner of the present invention may be a non-magnetic conductive toner,
Color development, which was extremely difficult with conventional development using conductive toner, has become easier.

(Example) The present invention will be explained below with reference to Examples. The middle part of the example shows parts by weight.

Example 1 After premixing raw materials according to the following recipe, they were melted and kneaded in a kneader, cooled, pulverized in a jet mill, and fine powder was cut in an air classifier to obtain a weight-based average particle size of 2, Toner particles of 8 μm were obtained. The average particle size based on the amount of N was measured using a Coulter Counter (trade name: TA-TI, manufactured by Coulter Electric Co., Ltd.). Further, when the volume resistivity was measured, it was found to be 5×10 4 Ωcm.

I-ner formulation: Polystyrene resin (trade name Niregit 5-94, manufactured by Sanyo Chemical Industries, Ltd.: Izosoto impact value 0.5 kg-cm/c
d or less) 67.5 parts carbon black (product name: MA-8, manufactured by Mitsubishi Chemical Industries @) 12.5 parts triiron tetroxide (product name: MG-WMK, manufactured by Mitsui Kinzoku Kogyo ■)
Visual observation using an electron microscope revealed that the toner particles thus obtained had an irregular shape with many corners. In addition, toner aggregation is severe and the diameter of 1
There were many aggregates of ~2. Therefore, 0 parts of this toner was added to 100 parts of spherical ferrite particles whose surfaces were coated with silicone resin having a weight-based average particle diameter of approximately 90 μm.
．． 8 parts were added and thoroughly mixed using a shaker. When the thus obtained developer was visually observed using an electron microscope, it was found that the toner was uniformly held in the spherical ferrite particles. When this developer was used in a commercially available copying machine using a two-component developer and transferred onto electrostatic recording paper, very good images were obtained.

The volume resistivity was measured as follows.

A commercially available tablet molding machine for measuring infrared absorption spectra (inner cross section of molding is a circle with a diameter of 20+++ m) was preheated to 23°C.
Approximately 0.8 g of toner that had been left in a high temperature and high humidity tank at 5096 RH for 24 hours was added, and a hydraulic press was used to press the toner to 400 kg/c.
A cylindrical pellet with a thickness of about 2 mm and a diameter of 20 mm at both ends was prepared by applying pressure with nf.

A diameter of 10 m is placed in the center of both circular end faces of this pellet.
A silver paste was applied to the main electrode of the main electrode, and one end was placed on the gland. Next, a guard electrode with one end grounded was provided along the outer periphery of the pellet. DC 1 to main electrode
A voltage of 00 V was applied, the current flowing between the main electrodes was directly read with an ammeter, and the volume resistivity was calculated from the value at the stable stage using the following formula.

Volume resistivity = (resistance value
A toner having an average particle size of 4.7 μm was obtained.

Toner formulation Rosin modified polyester resin (Product name: KR445, manufactured by Arayo Kagaku Kogyo ■: Izod impact value), Okg・CM
/ c) 80 parts conductive tin oxide (trade name T-1, made by Mitsubishi Metals)) 15 parts Phthalocyanine blue (trade name Rionol Blue SM)
(manufactured by Toyo Ink Seisaku@)) 5 parts The volume resistivity of the toner particles was 2×10 7 Ωcm. This toner had extremely good fluidity even as it was, or was mixed with spherical ferrite particles in the same manner as in Example 1.
When we conducted a similar printing test, we were able to obtain good images.

Example 3 In Example 1, particles obtained by the following method were used instead of spherical ferrite particles. The raw materials were premixed based on the following recipe, melted and kneaded in a kneader, and then ground in a jet mill to obtain amorphous particles having a weight-based average particle diameter of about 40 μm.

Polyester resin (Tufton NE382, Kao (manufactured by Sakaki))
45 parts triiron tetroxide (same as in Example 2) 55 parts A printing test was conducted using this in the same manner as in Example 1, and similarly good images were obtained.

Example 4 A spherical toner having an average particle size of 3.5 μm was obtained by a suspension polymerization method. The prescription is as follows.

Copolymer consisting of styrene 80 ffl amount 06 and butyl methacrylate 20 weight 96 parts 70 parts carbon black (same as Example 2) 10 parts triiron tetroxide (trade name: EPT-1000, manufactured by Toda Kogyo ■)
20 parts volume resistivity is 3X105Ωcm
There was. Although this toner was spherical in shape, some soft aggregation occurred. Weight-based average particle size 120μ
When mixed with spherical magnetite particles coated with a fluorine acrylic resin and subjected to the same printing test as in Example 1, a good image could be obtained.

Example 5 The toner obtained in Example 1 had a weight-based average particle size of 40 μm.
spherical ferrite particles coated with m fluorine-acrylic resin were mixed. When the thus obtained developer was visually observed using an electron microscope, it was found that the toner was well preserved in the spherical ferrite particles, or that some of the toner had aggregated due to the slightly small size of the ferrite particles.
When a printing test was conducted in the same manner as in Example 1, a good image was obtained.

Example 6 The toner obtained in Example 1 had a weight-based average particle size of 90 μm.
Spherical ferrite particles without resin coating were mixed. Visual observation of the obtained developer using an electron microscope revealed that the toner was well retained in the spherical ferrite particles. However, when a printing test was conducted in the same manner as in Example 1, it was found that either a good image was obtained or that the toner was scattered because the force of the spherical ferrite particles to restrain the toner was slightly insufficient. When the number of rotations of the magnetic sleeve was reduced, the scattering was resolved.

Comparative Example 1 A toner was produced in the same manner as in Example 1 using the following formulation.

Rosin-modified polyester resin (same as Example 2) 93 parts Carphone black (same as Example 2) 2 parts Triiron tetroxide (
Same as Example 2) 5 parts The toner particles thus obtained had an average particle size of 4.5 μm. Volume resistivity is 1
It was over 0.015ΩCm.

This insulating I-ner had extremely poor fluidity and could not be used as a 1-ner as it was.

Comparative Example 2 1.0 part of the toner obtained in Example 2 was added to 100 parts of amorphous ferrite particles having an average particle size of 15 μm, and the mixture was thoroughly mixed using a shaker. When the thus obtained developer was visually observed using an electron microscope, it was found that the amorphous ferrite particles could not fully hold the toner and some of the toner agglomerated, making it unsuitable.

Comparative example 3

Claims (1)

[Claims] 1. Mix a toner with a volume resistivity of about 1×10^1^0 Ωcm or less and a weight-based average particle size of 0.5 μm to 5 μm, and magnetic particles whose weight-based average particle size is 5 to 200 times that of the above toner. A conductive fine particle developer characterized by: