JPS60192959A - Dry developer - Google Patents

Abstract

PURPOSE:To obtain a developer superior in image quality, stable in image quality against change of circumstance, nd superior in durability by triboelectrifying a toner and a carrier in the same polarity and reverse in polarity to an electrostatic latent image. CONSTITUTION:A dry developer consists of insulating magnetic carrier particles contg. a magnetic material in a resin and having an average particle diameter of <=100mum, and insulating magnetic toner particles contg. a magnetic material in a resin and having an average particle diameter of <=30mum. Both toner and carrier particles are triboelectrified in the same polarity but reverse in polarity to an electrostatic latent image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a developer that visualizes electrostatic latent images in electrophotography, electrostatic recording, etc., and further enables electrostatic transfer. 2. Description of the Related Art Structure and Problems of Conventional Wax Conventional Examples Magnetic brush development using a two-component developer is generally well known as a method for visualizing electrostatic latent images in electrophotography, electrostatic recording, and the like.

A two-component developer consists of a toner consisting mainly of resin, carbon, charge suppressant, etc., and carrier particles such as ferromagnetic material, such as iron powder, which triboelectrically charges the toner and carries it to the latent image on the photoreceptor. It is a mixture of When this developer is held on the surface of a non-magnetic sleeve containing a built-in magnet, a developer brush is formed by the magnetic field and rubs against the latent image on the photoreceptor.

The image is visualized using toner that has an opposite charge to the photoreceptor. In such a two-component developer, each toner particle is sufficiently charged due to frictional electrification with the carrier particle and has the same polarity, so stable image quality can be obtained, and furthermore, the insulating property Therefore, it also has excellent transfer characteristics. On the other hand, the average particle size of carrier particles is 100 to 200μ
m is very large compared to the average particle diameter of toner particles of 10 μm, and it is necessary to reduce the toner concentration in order to sufficiently triboelectrically charge the toner particles. This triboelectric charging phenomenon occurs when the surfaces of two types of substances come into contact with each other, so if the toner concentration is high and exceeds the amount of adhesion to the carrier surface, the triboelectrification of both becomes insufficient, causing toner scattering and non-contamination. This causes fog in the image area. Generally, this toner concentration is about 3 to 7%, and if the toner concentration changes, the effect on the image density is significant, so it is necessary to always keep the toner concentration constant or mix the toner carrier uniformly. It is necessary to provide the developing device in the developing device, which makes the developing device complicated and large. In addition, since carrier particles such as iron powder and ferrite particles are hard, they can easily damage the photoreceptor, and cause toner filming on the carrier surface, which can disrupt the balance between the charge amount of toner and carrier.
The problem of image density reduction is also likely to occur. This shortens the lifespan of the developer and shortens the maintenance cycle.In high-speed machines, this apparently extends the lifespan.

There is a drawback that the amount of developer must be increased.

Furthermore, in terms of image quality, developer blur/
As soon as brush marks appear, fine line images become distorted, and solid black images tend to have edge effects.

It is not suitable for copying photographs or paintings because it has poor reproduction of halftones.

On the other hand, a one-component insulating magnetic toner in which the toner particles contain a magnetic substance and does not require carrier particles has been proposed as a developer capable of electrostatic transfer, and has been partially put into practical use. This -component magnetic toner does not easily produce edge effects on solid black images, and since it does not use gearia particles, it does not require a toner density control mechanism, is easy to maintain, and has advantages such as fewer six-shots. have.

However, there is no carrier, which is a clear object of triboelectrification, and these include the sleeve, blade, surface of the photoreceptor, and each toner particle with which the toner particles come into contact. To this end,
Although each toner particle is charged, the polarity and amount of charge are insufficient, and they are easily affected by the environment.

Image quality is unstable.

In order to solve these problems, a developer has recently been devised in which two types of insulating magnetic particles having different triboelectric properties are mixed and one is used as a toner particle and the other as a carrier particle. In this developer, both toner particles and carrier particles contain a magnetic material in the resin, and the average particle diameter of the toner particles is about IQ//m, and the average particle diameter of the carrier particles is 2Q to 60/1. Compared to conventional two-component developers, the carrier particles are finer and the density is lower, so the critical toner density is larger and the image quality changes less due to changes in toner density. However, reducing the average particle size of this insulating magnetic carrier is difficult because of the potential of opposite polarity that occurs around one image area when the electrostatic latent image on the photoreceptor is visualized.
It has the disadvantage that it is prone to the phenomenon of so-called carrier sticking, and is particularly susceptible to changes in the environment. Furthermore, this phenomenon is accentuated when a bias is used during development to eliminate fog. Therefore, in order to obtain high-quality images, it is necessary to develop a durable developer that does not cause carrier adhesion even when using an insulating magnetic carrier with a small average particle size and does not deteriorate due to environmental changes. desired.

Purpose of the Invention The purpose of the present invention is to provide excellent image quality, stable image quality against environmental changes, excellent durability, electrostatic transfer, and visualization of electrostatic latent images. The object of the present invention is to provide a possible dry type developer.

Structure of the Invention The dry developer of the present invention contains insulating magnetic carrier particles containing a magnetic substance in a resin and having an average particle size of 10Q/1 m or less;
A dry developer consisting of insulating magnetic toner particles containing a magnetic substance in a resin and having an average particle size of 30 μm or less, in which the toner and carrier have the same polarity and rub against the electrostatic latent image with opposite polarity. This dry developer is characterized by being electrically charged.This dry developer allows electrostatic latent images to be visualized with excellent image quality, and there is little change in image quality due to environmental changes, making it easy to visualize. The formed toner image can be electrostatically transferred and has excellent durability. In particular, in the dry developer of the present invention, the average particle size of the insulating magnetic carrier can be reduced in order to improve image quality.

In that case, the general problem is that the carrier adheres to a potential area that is opposite in polarity to the image area that occurs around the electrostatic latent image on the photoreceptor. Although it is remarkable, this problem has been solved by making the gear rear and toner have the same polarity as in the present invention. This effect is particularly significant when a bias potential is used on the sleeve to eliminate fog.

Description of Examples Next, the materials, manufacturing method, and specific examples of the developer of the present invention will be described.

Resin components useful for development according to the present invention include styrene, vinyl chloride, methyl acrylate, methyl methacrylate,
Homopolymers made of monomers such as vinyl methyl ether, acrylonitrile, vinyl methyl keto 7, etc., copolymers or mixtures of two or more of these monomers, or partially modified with various substituents. including.

Fine particulate magnetic materials include alloys or compounds containing ferromagnetic elements such as ferrite, magnetite, iron, cobalt, and nickel.

Some examples include alloys such as manganese-copper-aluminum, manganese-copper-tin, or chromium dioxide, which exhibit ferromagnetic properties through appropriate heat treatment.

Any suitable pigments or dyes can be used as colorants and charge control agents. Examples include, but are not limited to, carbon blank, aniline glue, phthalonoamine blue, Kayaset black T-2, Spironbranok, nicrosine base, and nigrosine hydrochloride.

The amount of magnetic material added is desirably 5 to 50 parts by weight in the case of toner particles, and 5 to 80 parts by weight in the case of carrier particles.

In addition, pigments are included in the toner particles, if necessary.

A charge suppressing agent, a mold release agent, etc. are added.

When producing the toner particles and carrier particles of the developer of the present invention, conventional toner production methods can be applied.

For example, resin components, particulate magnetic materials, and.

Other additives are premixed using a super mixer, etc., and each component is mixed and dispersed uniformly, and then kneaded and melted using a twin screw extruder, cooled, and pulverized. The pulverized material is classified to obtain the desired particle size.

As for toner particles, more favorable charging properties and fluidity can be obtained by surface coating with fine particles of inorganic and organic compounds.

It is desirable that the toner particles and carrier particles thus obtained have an insulating property of 1012 Ω·Clzl or more.

Next, the toner particles and carrier particles produced as described above are mixed in a desired ratio to form the developer of the present invention. The mixing method may be any suitable method.

A magnetic brush development method is most suitable for development using the developer of the present invention. In particular, it is effective to use a developing device that has a structure in which a magnet roll, which is made up of a collection of multiple magnets arranged with different polarities in sequence, is covered with a sleeve made of a non-magnetic material. . In this case, the sleeve is fixed and the internal magnet roll is rotated.

There are three methods: a method in which the sleeve is rotated while the -0 magnet roll is fixed, and a method in which both are rotated, and the developer of the present invention can be used in either method.

During development, the sleeve described above is grounded, but a bias voltage can also be applied to it.・Kuiasumi pressure is effective for removing capri, but in order to obtain high quality images with good halftone reproducibility, it is necessary to use resin magnetic carrier at 20%
The resin magnetic carrier used in the present invention has the problem that carrier adhesion is likely to occur when the size is as small as ~60 μm.

By giving it triboelectricity of the same polarity as the toner,
Eliminates carrier adhesion.

Next, details and effects of the present invention will be explained using specific examples. Note that the amount added in this example is expressed by weight.

The charging characteristics were measured and evaluated using a blow-off charge measuring device (MODELTB-20 manufactured by Toshiba Chemical Corporation).
The test was conducted under the following conditions.

Sample: Approximately 200 nlf/, carrier iron dioxide powder (N
A, C-Ql), blow pressure approximately 1. o kg/ct
! r, mesh-3US 400M,.

Regarding the image quality when using the developer of the present invention,
A copy image was created using an electrostatic copying device and evaluated. The photoreceptor is selenium and an organic photoreceptor, and electrostatic latent images of positive and negative polarity are created, and the sleeve is rotated at a speed of 130-1 and the stone a-roll is 1300p for both rotational development, and a bias voltage is applied to the sleeve. Development and electrostatic transfer were performed by applying 60 to 200V. The paper feed speed is 140 f/sec.

[Example 1] "MD-193" (styrene-acrylic resin.

(manufactured by Sekisui Chemical Co., Ltd.) Section 70 and “EPT-600”
(Manufactured by Magnetite Toda Kogyo Co., Ltd.) with Section 25.

[Viscol 550Pj (manufactured by Sanyo Chemical Co., Ltd.) 2%
Gron-based charge system (foundation) for "Bondrono N-o7"
(manufactured by Orient Chemical Co., Ltd.) in a super mixer, and then kneaded in a twin-screw extruder. After cooling,
A magnetic powder having a particle size of approximately 5 to 26 μm is prepared by pulverization and classification, and this magnetic powder is coated with [F0ZIL RA7200HJ].
(Fine silicon dioxide 1 manufactured by Nippon Aerosil Co., Ltd.) o,
6% of the mixture was mixed and surface coated using a shaker to obtain toner particles. The amount of charge was +12 μC/gr'c.

1-Mn-549j (amine-modified styrene-acrylic resin, manufactured by Sekisui Chemical Co., Ltd.) 75% and [EPT-60
Mix with 0J25% and form approximately 1° to 40 μm in the same manner as above.
Magnetic powder with a particle size was prepared and bound with carrier particles. The amount of charge was +2.5 μc/f/−C.

The obtained toner particles and carrier particles were mixed at a ratio of 1:3 and developed. Images transferred and fixed onto plain paper using the above-mentioned copying device using the negatively charged organic photoreceptor have high density, no carrier adhesion or edge effects, and no intermediate tones,
Also, solid black is well reproduced. Further, no capri was observed, the image was clear, and no image disturbance due to transfer was observed. Regarding the above characteristics, stable results were obtained even in an environment with a temperature of 18 to 35° C. and a humidity of 30 to 90 SRH.

[Example 2] "XPA-sslJ (styrene-acrylic resin.

(manufactured by Mitsui Toatsu Co., Ltd.) 75% and “EPT-500J2
3 and Spiron Plank TRHJ (manufactured by Hodogaya Chemical Co., Ltd.) 2 were mixed to obtain a powder with a particle size of approximately 6 to 2571 m in the same manner as in Example 1, and to this powder, [ Aerosil R972j (manufactured by Nippon Aerosil Co., Ltd.) o, 5
% to form toner particles. The amount of charge was -251tc/9.

"xpA-rstslJ 25% and "PP-7J (
75% of manganese-ferrite (manufactured by Kanto Denka Co., Ltd.) was mixed, and gearia particles having a diameter of about 16 to 45 μm were obtained in the same manner. The amount of charge is -3μC/I! Met. Evaluation was carried out using a copying machine that used a positively charged selenium photoreceptor as in the example, and similarly good images were obtained and it was stable under various environmental conditions.

[Comparative Example 1] The toner particles of Example 1 and the carrier particles of Example 2 were mixed in a ratio of 1:1.
When the images were evaluated using the copying machine of Example 1, carrier adhesion occurred, especially when eso%RH
This was noticeable at low humidity.

Effects of the Invention As is clear from the above description, the dry developer of the present invention contains insulating magnetic carrier particles containing a magnetic material in a resin and having an average particle size of 100/Zm or less, and a magnetic material in the resin. and insulating magnetic toner particles with an average particle size of 3 Q 71 m or less, the toner and carrier having the same polarity and being tribo-electrified to the opposite polarity with respect to the electrostatic latent image. According to this, even if the average particle size of the resin magnetic carrier is reduced in order to increase the critical toner concentration,
Electrostatic latent images can be visualized with excellent image quality without carrier adhesion. Moreover, there is virtually no need to control toner density, the image quality is stable, there is little change in image quality due to environmental changes, and the developed toner image can be electrostatically transferred, which is an excellent effect. . These effects combine the advantages of conventional one-component and two-component developers. Furthermore, organic photoreceptors suitable for creating electrostatic latent images of negative polarity are flexible and can be supplied at relatively low prices, making it easier to reduce the price of electrophotographic copying devices. The effect of doing so can be obtained.

Claims (1)

[Claims] Insulating magnetic carrier particles containing a magnetic substance in a resin and having an average particle size of 10Q/Zm or less; and insulating magnetic toner particles containing a magnetic substance in a resin and having an average particle size of 3'01 tm or less. A dry type developer characterized in that the toner and carrier have the same polarity and are triboelectrically charged to the opposite polarity with respect to the electrostatic latent image.