JPS59223454A - Composition for developer - Google Patents

Abstract

PURPOSE:To provide always high grade image quality with an excellent line image, resolving power, etc. without photographic fogs by constituting a titled compsn. of a magnetic carrier which contains inorg. particles as a core and of which the shell is coated with a polymer contg. magnetic powder and a magnetic toner contg. magnetic powder. CONSTITUTION:This compsn. for a developer consists of a magnetic carrier of which the shell of the inorg. particle core 1 is coated with a polymer 2 contg. magnetic powder 3 and a magnetic toner 4 contg. magnetic powder. The same inorg. powder as the inorg. powder of a carrier for magnetic brush development is usable for the inorg. powder of the core 1. An acrylic resin, fluororesin, etc. are selected for the polymer 2 to meet the electrostatic charge characteristic. The same magnetic powder as the magnetic powder for the core 1 is usable for the powder 3 and is made to have 0.05 to 5mum grain size. The mixing ratio of the polymer 2 and the powder 3 is made 10:90-95:5 by volume. The magnetic carrier prepd. in such a way has >=40emu/g satd. magnetization and 20-200mum average grain size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dry developer for developing electrical latent images in electrophotography, electrostatic recording, electrostatic printing, etc., and relates to a carrier in a two-component dry developer. and related to toner improvements.

Prior Art Methods for forming electrical latent images are well known in the art; for example, in electrophotography, a photoconductor is typically charged and then irradiated with a light image based on the original image. 1. Reduce or eliminate static charges on the irradiated area. Forms an electrostatic latent image.

Methods for developing latent images obtained in this way can be roughly divided into wet developing methods and dry developing methods, but the former has concerns about odor, ease of handling, safety, etc., and in recent years, dry developing methods have been used. It has become mainstream.

Regarding the dry development method, different types of materials and methods have been proposed, but in general, it is often classified into one type, a -component development method and a two-component development method, based on the composition of the i-developing agent. -The component development method basically forms an image using only toner particles. Therefore, toner particles have many advantages, but in order to achieve high image quality, toner particles must satisfy all the various characteristics required in many processes such as charging, transportation, development, transfer, cleaning, and fixing. It is extremely difficult to control physical properties.

On the other hand, the two-component development method is a development method in which carrier particles are mixed in addition to toner particles.

The toner is made of particles in which a colorant, a charge control agent, etc. are added and dispersed in a binder resin, and the average particle size is adjusted to about 10 tim. Further, as the carrier, particles such as glass powder and iron powder are used. In particular, in the case of magnetic push development method,
Magnetic particles such as iron powder or iron oxide powder are used as they are or with the surface coated with a charge control resin, etc., and the average particle size is around 700 μm. Usually, toner particles vi-o, s weight % to left weight % with respect to carrier particles
A two-component developer is obtained by mixing the toner particles to a certain extent. In such a developer, the carrier particles impart a triboelectric charge to the toner particles, and further carry the toner particles on their surface, so that the toner particles are transferred to the latent image area. They share functions such as stably transporting and supplying food. Therefore, it has the advantage that image quality can be easily controlled over a certain range by adjusting not only the physical properties of the toner but also the physical properties of the carrier. However, since it mainly utilizes the triboelectrification phenomenon of toner particles and carrier particles,
The image quality tends to fluctuate due to changes in the mixed concentration of toner and carrier, and environmental changes such as temperature and humidity, and furthermore, the developer deteriorates with repeated use, resulting in a decrease in image quality.

In order to improve and overcome these problems, much research and development has conventionally been carried out regarding carrier materials and toner materials.

For example, Japanese Patent Publication No. Sho S/-7!992 discloses that the particle size of the main body is 5 to 5. Attempts have been made to use a large particle carrier having a particle size Miif of 3 to 10 times that of the toner in combination with a 20 μm toner, and a small particle carrier having a particle size ±5 of the particle size of the toner. The small particle size carrier is comprised in the range of 70 to 3% by weight in the total carrier, and by mixing the two, it is intended to improve gradation reproducibility and extend the life of the developer. In the case of such a developer composition,
It is true that the gradation reproducibility is much improved when using only large-particle carriers, and furthermore, the contamination and deterioration of the carrier due to toner is improved compared to when using only small-particle carriers. A large amount of carrier particles having the same particle size is developed and consumed together with the toner particles, and as a result, it cannot withstand repeated use over a long period of time.

Tokukai Akira! /-//No. 70 Gθ Publication discloses that by mixing spherical carrier particles and amorphous carrier particles to increase toner supply efficiency, good image quality can be obtained for both line images and solid black images. There are descriptions such as:

Although this is also effective in improving the initial image quality, it does not improve stability against environmental changes or repeated use over a long period of time.

% Kaisho JA-/No. 905g contains a spherical carrier and toner, and a proprietary magnetic toner, which increases the developer's 4-color ratio, prevents hollow images, and improves trapping and development. There is a statement that it aims to extend the life of the agent. But 1. ! J? ,
? & Currently, magnetic toner tends to stick to the photoreceptor at low pressure due to static conduction and charge injection, which tends to cause contamination of non-image areas. Although it is true that the reproduction of a single solid black image is good, secondary problems include deterioration of image quality due to adhesion and scattering of conductive magnetic toner, and environmental and temporal instability.

As mentioned above, conventional developers have had many problems in consistently providing stable high image quality despite environmental changes and repeated use over a long period of time.

Purpose of the invention The purpose of the invention is to solve the problems of conventional developers as described above, and to provide high-quality images with excellent line images, solid black images, gradation reproducibility, resolution, etc., and without fogging. To provide a developer composition that can consistently provide good image quality despite changes in environmental conditions such as temperature and humidity, changes in toner # in summer, repeated use over a long period of time, and changes in development speed. It is to be.

Structure of the Invention The developer composition according to the present invention is characterized by comprising a magnetic carrier comprising inorganic particles as a core whose outer shell is coated with a polymer containing magnetic powder, and a magnetic toner containing magnetic powder. do.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail with reference to non-inventive embodiments with reference to the accompanying drawings.

The accompanying drawings conceptually illustrate the structure of the developer composition according to the present invention. As shown in this figure, the developer composition according to the present invention consists of a magnetic carrier formed by coating the outer shell of an inorganic particle core 1 with a polymer 2 containing magnetic powder 3, and a magnetic toner 4 containing magnetic powder. ing. In the figure, both the carrier and toner are shown as spheres, but in actuality,
It can be either spherical or irregular. However, from the viewpoint of developer transportability, lifespan, etc., a spherical shape or an amorphous shape close to a spherical shape is desirable. Furthermore, it is preferable that the magnetic powder 3 be exposed to the outer surface of the carrier.

As the material for the core 1 of the magnetic carrier, inorganic powders can be used, but materials that are normally used as carriers for magnetic brush development can be used. For example, ferromagnetic metals such as iron, cobalt, and nickel, and their alloys, and oxides such as iron oxide powder and ferrite have an average particle size of 20 to 2008 m1, preferably 50 to A-0 μn.
It can be adjusted to 7 and used.

As the coating material 2 of the carrier core 1, well-known acrylic resins, resins, styrene resins and styrene copolymers, polyamides, olefin resins such as polyethylene, ethylene vinyl acetate copolymers, chlorinated polyolefins, polyesters, polyurethanes, Fluorine fiber resins such as polycarbonate, epoxy resin, silicone resin, polytetrafluoroether, ren, polyvinylidene fluoride, etc. can be selected depending on the charging characteristics.

As the magnetic powder 3 dispersed in these coating polymers 2, the same magnetic particles as those used for the carrier core 1 can be used, but desirably, triiron tetroxide, r-iron sesquioxide,
MnZn ferrite, N1ZIL ferrite), Ba7 ferrite, etc. are preferable. The magnetic powder is adjusted to be a granular or acicular powder with a particle size of aosμm to Sμm1, preferably 0.7μm to 2μm (in the case of needle-like powder, its major axis is Sμm or less).

The mixing ratio of the coating polymer 2 and the magnetic powder 3 is 10: by volume.
9θ~q1. li', preferably 3θ near 0 to 90
: Adjust to 10. If the amount of coating polymer 2 is too small, it will naturally not be possible to form a stable coating on the surface of core 1.
Conversely, if the amount of coating polymer is too large, it is difficult to control the electrical and magnetic properties of the carrier particles. magnetic powder 3
In order to control the dispersion state of the magnetic powder in the coating polymer 2 and form a stable coating with strong mechanical strength, the surface of the magnetic powder is coated with a silane coupling agent to control the electrical properties of the surface. , a titanate coupling agent, a higher fatty acid, a derivative thereof, or the like.Furthermore, a reactive group may be provided in the coating polymer and bonded to the surface of the magnetic powder.

Furthermore, in addition to the magnetic powder, additives such as dyes and pigments and surfactants may be mixed into the coating polymer as needed.

The material to be drawn having the above-mentioned structure can be dissolved and dispersed in an organic solvent, coated on the core particles as an aqueous emulsion dispersion and dried, or deposited on the core particles as a powder. Then, a stable repeat can be formed on the core particle by a method such as sintering. Although it is preferable that the coating is applied uniformly over the entire surface of the core particle, there is some effect even if the coating is partially applied. Furthermore, it is desirable to use these magnetic powders 3 in a state in which they are exposed in an uneven manner on the outer surface of the object M2.

The magnetic carrier prepared in this way has a saturation magnetization of '
A Oernu / g or more, preferably u '70
Near spherical particles with an average particle size of emu/g or more and an average particle diameter of λθ to λθθ-m1, preferably 30 to /SOμtn are desired.

In addition, the magnetic carrier〇 electrical resistivity is the coating polymer 2
It can be adjusted depending on the amount of magnetic powder inside, but /θ6~10"
Qm, H"!L< is preferably /θ8 to 10'40cIJL.

As the magnetic toner 4, a material composition conventionally used as a magnetic toner may be used. Binder resins for magnetic toner include styrene resins, acrylic resins, olefin resins such as polyethylene, diene resins such as butadiene and imprene, polyesters, epoxy resins, fluorine resins, silicone resins, and phenolic resins. ,
Petroleum resins, synthetic resins such as polyurethane, and natural resin-like materials can be used. The magnetic powder for the magnetic toner can be the same as that used in the carrier core and coating polymer, but preferably triiron tetroxide, Mn;! n ferrite, NlZn ferrite,
Ban elite etc. are good. These magnetic powders have particle sizes θ, θ
Preferably, it is adjusted to a granular or acicular powder with a size of 0.17 to 7.0 μm.
In the case of acicular powder, its major axis f: 2.0/J m or less). In addition, carbon black is used as a charge control agent.
Quaternary ammonium salts, organic complexes, etc. can be used. Additionally, additives such as surfactants, reinforcing fillers, plasticizers, dispersion inhibitors, and blowing agents can be added to the above-mentioned binder resin material as necessary.

Furthermore, in addition to the magnetic toner, the developer composition of the present invention further improves the fluidity, development, transferability, and storage stability of the developer. In order to prevent filming and improve the cleaning properties of the developer, long chain fatty acids such as stearic acid and their derivatives, carbon black, graphite, graphite heptadide, boron nitride, silica, aluminum oxide, titanium dioxide,
Fine powder materials such as fine powder of zinc oxide, fine resin powder of fluororesin, olefin resin, etc. may be added. These additives are preferably added to the magnetic toner in an amount ranging from O, OS to 0% by weight.

The magnetic toner thus prepared has a saturation magnetization of 3
emu/g or A Oemu/g % Preferably, /! ; emu / g to g θemu /
g, average particle size ~20μm1 preferably 70~/S
It is desirable to use it in the μm range. In addition, the electrical resistivity of magnetic toner is determined by the amount of magnetic powder in the toner and external additives.
For example, it can be adjusted with carbon black, etc., but 109
From Ω to /θ16Ω, preferably from 1013 Ωα to /θ15Ωα.

Although there is no clear answer as to why the developer composition of the present invention configured as described above is able to stably provide better fr and image quality than conventional ones, it is as follows. It can be inferred that

The magnetic carrier used in the present invention has an insulating charge control resin and a semiconductive magnetic powder with relatively low electrical resistivity on its outermost surface. Fine control of characteristics can be easily performed and high image quality with excellent gradation reproducibility can be obtained. In addition, the exposure of the magnetic powder 3 increases the substantial charging surface area and has the effect of promoting charge conversion, which is thought to improve the poor charging efficiency in the ability to carry and transport toner particles. Also,
Since the toner is a high-resistance magnetic toner, it is thought that it suppresses contamination inside the machine due to toner cloud and the occurrence of ground cover in the background area.

In order to confirm the effectiveness of the developer composition of this invention, development was carried out using various developer compositions prepared, and the following results were obtained.

〔Example/〕

Menal methacrylate resin 3 parts triiron tetroxide (average particle size 0.3 μm) left part toluene
70 parts were mixed to prepare a composite coating material, and the present coating material was further mixed (mixed with 300 parts of spherical iron powder with an average particle size of gOμm, heated and dried,
A carrier A whose surface was coated with a composite coating material was obtained. When this carrier A was observed using a scanning electron microscope, it was confirmed that the coverage was good and smooth, and that the triiron tetroxide powder formed an uneven surface.

Furthermore, 70 parts of polyester resin, 2S parts of magnetic powder, and S part of Carpon Thick were melted, mixed, and crushed to obtain an average particle size of 3μ.
A toner Ai was obtained which was prepared by mixing θ and G weight percentages with respect to the colloidal silica toner. The aforementioned carrier A and toner A were mixed to form a developer.

[Example 2] Ferrite (average particle size gθμm) 00 parts Polyvinylidene fluoride powder 5 parts Muferite powder (
Average particle size 0. Sμm) were mixed to obtain carrier B after sintering.

Furthermore, 75 parts of styrene punal methacrylate, 20 parts of triiron tetroxide (average particle size 0.3 μm), and 3 parts of carbon black.
1 part and 2 parts of a quaternary ammonium salt were melt mixed and pulverized to obtain a toner B'fI having an average particle size of 3 μm. The aforementioned carrier B and toner B were mixed to form a developer.

[Comparative example/]

Toner C was prepared by melting, kneading, and pulverizing 90 parts of polyester resin and 10 seconds of carbon black to obtain a toner with an average particle size of 3 μm, and further mixing and adjusting 0.3 parts by weight of colloidal silica with respect to the toner, [Example/ ] was mixed with carrier A used in ) to prepare a developer.

[Comparative example]

The iron oxide powder was removed from the base covering material used in [Example/], and only the methyl methacrylate resin was used with an average particle size of gθμ.
A carrier C was prepared by coating spherical iron powder of 100 m, and a developer was prepared by mixing this carrier C with the toner 8 used in [Example/].

[Comparative Example 3] The carrier C used in [Comparative Example λ] and the toner C used in [Comparative Example/] were mixed and adjusted to form a developer.

[Comparative example]

The spherical iron powder with an average particle diameter of gOμm used in [Example/] was not treated as it was and was used as Carrier 〇. This carrier D
A developer was prepared by mixing and adjusting the toner A used in [Example/].

The results of image quality evaluation performed on a 23θO copying machine manufactured by Fuji Xerox Co., Ltd. using the developers of each side described above are summarized in the following table. Note that in [Example C], ZnO was used as the photoreceptor, and good image quality was obtained. t'fc,, in the table, a double circle means that the quality or characteristic was very good and rare, - a double circle means that they were good, a triangle sign means that the quality or characteristic was very good and rare; It means that they were not in good condition.

I Effect of the invention Examples according to the present invention in the above table /, C and comparative examples /,
As is clear from a comparison of the properties of the developer composition of the present invention,
It has better gradation reproducibility than conventional ones, and
It is also excellent in that there is no background dirt or contamination inside the machine.

Furthermore, the developer composition according to the invention has environmental stability,
It also has excellent stability when burning and toner concentration dependence.

[Brief explanation of drawings]

The accompanying drawings are conceptual diagrams showing the structure of the developer composition of the present invention. 1... Inorganic particle core, 2... Polymer, 3
...Magnetic powder, 4...Magnetic toner

Claims (1)

[Claims] A developer composition comprising: a magnetic carrier comprising inorganic particles as a core whose outer shell is coated with a polymer containing magnetic powder; and a magnetic toner containing magnetic powder.