JPS5969762A - Magnetic toner composition - Google Patents

Abstract

PURPOSE:To obtain a titled compsn. which has high electric resistivity, is excellent in developability, transferrability, impact resistance, moisture resistance and fluidity, and is uniform without having variance by incorporating a specific binder resin and magnetic material as an essential component. CONSTITUTION:A raw material monomer of a binder resin (e.g.; styrene) and a monomer that can bind chemically with the surface of a magnetic material (e.g.; vinyl trichlorosilane) are copolymerized to obtain a binder resin. Such binder resin and 50-75wt% a magnetic magerial having >=40emu/g saturation magnetization and 0.01-5mu average grain size (e.g.; iron powder) are melted, kneaded and pulverized to obtain a toner. The toner is compounded with a conductivity control agent, chargeability control agent, coloring agent, plasticizer, etc. according to need. The magnetic toner compsn. which does not wear the surface of a photoreceptor, etc. and has good conveyability, cleanability and fixability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner for developing electrical latent images in electrophotography, electrostatic recording, and the like.

The method of forming an electrical latent image is well known. For example, in electrophotography, a photoconductor is usually charged and then a light image of the original image is irradiated to reduce or modify the static charge on the light-irradiated area. Disappear and form a silent [latent image]. Next, this a1 image is developed using a developer called toner. Development methods are broadly divided into methods using wet developers and methods using dry developers; the latter is further divided into two-component development methods that use two types of particles, carrier and toner, and one that uses only toner. It is classified into component phenomenon method.

These developed toner images are transferred to paper or the like as required, and then fixed using heat, solvent, pressure, or the like.

Since the single-component development method that uses only toner does not use a carrier, there is no problem of contamination of carrier particles, that is, deterioration of the developer, there is no need to adjust the mixing ratio of carrier and toner, and there is no need for the developing device. It has many advantages such as simplicity.

There are various forms of this -component development method, and among them, a method of developing with a magnetic brush using magnetic toner is representative. This utilizes the magnetism of the magnetic powder mixed in the toner binding resin to form a toner brush on a magnetic roll, etc. while conveying the toner to the electrostatic latent image area. This phenomenon is caused by the stress imparted to the toner by a droplet, corona charging, friction band, etc.

The magnetic toner used for this purpose contains a considerable amount of magnetic powder in the toner binder resin, but magnetic powder has a hydrophilic surface and generally has poor dispersion in the binder resin, making it difficult to obtain a uniform toner with no variations. It is. In addition, because the bond between the magnetic powder surface and the binder resin is weak, pulverization easily occurs at the interface between the magnetic powder and the binder 1# fat during pulverization using the cross-wire pulverization method, etc. Magnetic powder is easily exposed. Since magnetic powder is concentric or semiconductive, surface exposure of magnetic powder reduces the surface resistivity of the toner particles. Also,
Since the magnetic powder is poorly dispersed in the binder resin and tends to form conductive paths, this results in a low volume resistivity of the toner particles, which in turn lowers the electrical resistivity of the toner. If the electrical resistivity of the toner is low, electrostatic transfer to the current 11!1 plain paper is extremely difficult.

In addition, such magnetic toners have low impact resistance (easily crushed by even the slightest impact), and have poor moisture resistance and fluidity because the hydrophilic magnetic powder protrudes to the surface of the toner particles (and is susceptible to photoreceptors, etc.). Its surface is easily worn, making it difficult to always obtain stable images without being affected by changes over time or changes in the environment.

In addition, when producing magnetic toner by the kneading and pulverization method, the particle size distribution of the pulverized toner is affected by the fact that the dispersibility of the magnetic powder is not good and pulverization easily occurs at the interface between the magnetic powder and the binder resin. It becomes wide. In order to use such toner for months, it is necessary to narrow the particle size distribution by a classification operation, which increases the number of manufacturing steps and reduces the yield, which increases the cost of the magnetic toner.

Conventionally, a method of treating the surface of magnetic powder with a 7-run coupling agent (for example, JP-A-54-84731, JP-A-54-127)
329), a method of treating with a titanate coupling agent (for example, JP-A No. 55-28019), a method of coating with a resin (for example, a method of treating with a lambda surfactant, JP-A-55-11218), etc. This increases the affinity between the magnetic powder and the binder resin, makes the dispersion of the magnetic powder uniform in the binder resin, and further improves the affinity between the magnetic powder and the binder (to prevent crushing at the interface with the sealant). Attempts have been made to improve moisture resistance, electrical properties, etc.

However, these methods did not fully solve the above-mentioned problems. Definitely distributed.

Moisture resistance etc. are improved, but it is theoretically impossible to prevent crushing at the interface between magnetic powder and binder resin, and when surfactants are used, stability over time may be improved. Alternatively, problems arise in environmental stability, and when a low-molecular processing agent such as a silane coupling agent or a titanate coupling agent is used, new problems such as worsening of the blocking resistance of the toner occur.

Some of these problems are alleviated somewhat if the magnetic toner contains fewer magnetic particles. However, when the magnetic powder content is reduced, it is difficult to convey the toner well by magnetic coal, and when magnetic roll cleaning is used, there is a drawback that cleaning performance is affected.

In addition, in terms of production, it is necessary to include a step in which the surface of the magnetic powder is previously treated with a silane coupling agent, a titanate coupling agent, a resin, and a surfactant, which makes the toner production process complicated. Note that the method of mixing these compounds when melting and mixing resin and magnetic powder does not increase the number of steps, but the treatment of the surface of the magnetic powder is not substantially sufficient. (An object of the present invention is to provide a magnetic toner composition that solves the above problems.) That is, the first object of the present invention is to provide a magnetic toner composition that has good dispersibility of magnetic powder in a binder resin (to provide a uniform magnetic toner with no variation). It is to provide.

A second object of the present invention is to provide a magnetic toner with high electrical resistivity (good developability and transferability).

A third object of the present invention is to provide a magnetic toner with excellent impact resistance, moisture resistance, and fluidity.

A fourth object of the present invention is to provide a magnetic toner that does not abrade the surface of a photoreceptor or the like.

A fifth object of the present invention is to provide a magnetic toner with good conveyance and cleaning properties.

A sixth object of the present invention is to provide a magnetic toner with good fixability.

An eighth object of the present invention is to provide an inexpensive magnetic toner.

A ninth object of the present invention is to provide a high-magnetic-force magnetic toner with stable characteristics.

A tenth object of the present invention is to provide a magnetic toner with good blocking resistance.

All of the above objects are aimed at providing a magnetic toner containing a binder resin and a magnetic material as essential components, in which the binder resin contains, as a monomer component of its raw material, a component capable of forming a chemical bond with the surface of the magnetic material. This is achieved by using magnetic toner.

The chemical bond in this case may be an ionic bond or a hydrogen bond, but a covalent bond is preferable.

The reactive component capable of forming a chemical bond with the surface of the magnetic material must be copolymerizable with the monomer constituting the raw material of the binding resin and have a group capable of forming a chemical bond with the surface of the magnetic material. Bye.

According to studies conducted by the present inventors, a 7-run coupling agent having a vinyl group showed the best results.

As 7-ran coupling agents having a vinyl group, vinyl trichlorosilane, vinyl triethoxy 7-ran, vinyl tris(β-methoxyethoxy) silane, γ-methacryloxyglobil trimethoxysilane, etc. are known. Either can be used.

The monomer constituting the binder resin may be any monomer as long as it causes a polymerization reaction with the vinyl group of the silane coupling agent, and may include styrene, rostyrene, methylstyrene, styrene derivatives such as vinylphenol, acrylic acid, etc. , methacrylic acid, alkyl acrylate or alkyl methacrylate whose alkyl group has 3 or less carbon atoms, vinyl nologel, allyl alcohol, vinyl acetate, and the like are easy to use.

The resin used in the magnetic toner composition of the present invention can be obtained by copolymerizing one or more of these monomers with a seven-run coupling agent having a vinyl group.

Such a resin does not necessarily need to be used alone as a binder resin for the magnetic toner of the present invention; it can be used in combination with a resin conventionally used in electrophotographic toners and the like.

For example, Evoquin resin, polyester resin, stereo resin, acrylic resin, polyamide resin, petroleum resin, silicone resin, geno resin, olefin resin,
Acrylic acid condensate, vinyl acetate polymer, polyether,
It can be mixed with polyurethanes, paraffin waxes etc. and their corresponding copolymers.

In the present invention, conventionally known magnetic powders are used, such as triiron tetroxide powder, iron sesquioxide powder, Kono(Luto γ-iron sesquioxide powder, chromium dioxide powder, iron powder, chromium powder, di-iron powder, kerosene powder, etc.). can be used.

Their shape is arbitrary. The average particle size is 0.01
Those in the range of ~5μ are easy to use. These magnetic powders may be used singly or in combination with different magnetic substances, shapes, or particle sizes.

Generally, the magnetic powder content of magnetic toner is 3 to the toner weight.
It is 0 to 70 heavy weights. In the present invention, the content of magnetic powder is arbitrary, but to effectively exhibit the characteristics of the present invention, 50 to 75% by weight of magnetic powder with a particle size of 0.1μ to 2μ, more preferably 60 to 70% by weight, is used. Contains i% and sulfide a is 4
0 emu/1 or more, preferably 48 emu/ or more.

The magnetic toner composition of the present invention contains the above-mentioned binder resin and magnetic powder as essential components, but may also contain a conductivity control agent, a charge control agent, a coloring agent, a plasticizer, a blowing agent, etc. as necessary. May be included.

Furthermore, external additives may be used for the purpose of improving the fluidity, developability, or cleaning performance of the toner.

External additives such as long chain fatty acids such as stearic acid and their esters, amides, metal salts, as well as molybdenum disulfide, carbon black, graphite, graphite fluoride, silicon carbide, boron nitride, silica, aluminum oxide. , fine powders of titanium dioxide, salivary lead oxide, etc., fine powders of fluororesins, polynomial aromatic compounds, other waxy substances, crosslinked or non-crosslinked resin fine powders, etc. are known. These external additives may be fixed to the toner particle surface by hot air or the like, if necessary.

When the binder resin of the present invention is used, the reactive rL acid component magnetic powder in the binder resin reacts when the binder resin is melted and kneaded with magnetic powder etc. during the manufacturing process to form a chemical bond. Therefore, in the magnetic toner composition of the present invention, not only does the magnetic powder have good branching properties, but the probability of pulverization at the interface between the magnetic powder and the binder resin is greater (lower) than before, and the magnetic powder is directly attached to the toner particle surface. The powder is never exposed, so even if it contains a high concentration of magnetic powder, a uniform magnetic toner with no variation can be obtained, and the surface of the photoconductor, etc. has excellent impact resistance, moisture resistance, and fluidity. Magnetic toner that does not wear out can be obtained.

Further, since it is possible to contain multi-vertical magnetic powder without impairing the properties as a toner, the conveyance property on a magnetic roll and the cleaning property are improved.

Toners containing magnetic powder in high concentration generally do not have very good heat fixing properties or pressure fixing properties, but the magnetic toner of the present invention has good dispersion of the magnetic powder (furthermore, since it is chemically bonded to the resin, The reason for this is not necessarily clear, perhaps because a suitable viscoelastic reinforcing effect and titanium tropism can be obtained, or because the magnetic powder is not exposed on the surface of the toner particles, but it shows very good fixing properties.

In addition, in the method of fixing using a heated roll, the adhesion of the molten toner to the heated roll was significantly reduced. This is due to the strong bond between the magnetic powder and the resin, which strengthens the elasticity of the molten toner. considered to be a thing.

Furthermore, since the magnetic toner of the present invention has a narrow particle size distribution during pulverization, it does not require a classification operation, or even if a classification operation is required, the yield is very high, making it inexpensive.

Regarding electrical resistivity, as the magnetic powder content increases, the electrical resistivity of the toner usually decreases, approximately 50% by weight ↓ If magnetic powder is included, the electrical resistivity will be reduced to an electric field of 10'V/cW.
1, it becomes 1013 Ωα or less, and electrostatic transfer becomes difficult, especially at high humidity. However, since the magnetic toner composition of the present invention has a high magnetic powder content, it is possible to obtain a toner having a high electrical resistivity of 10130α or more even in a high electric field of 10'V/cM. Generally, such high-resistivity magnetic toners can be easily transferred, but the phenomenon deteriorates, making it difficult to obtain good images. In general, when carrying out one-component development with high resistivity magnetic toner, there are methods based on triboelectric charging, corona charging, high-voltage conduction (induction, injection from electrodes, etc.) to impart a charge to the toner, and The phenomenon method using induced tortoise polarization is adopted. However, it is extremely difficult to provide a sufficient amount of charge necessary for development and to appropriately control the charge distribution, and the Coulomb force of the development region armor is extremely difficult to apply. It is not possible to adjust various forces acting on toner particles, such as polarization force, tearing force, and magnetic force.This results in uneven appearance and contamination of non-planned areas.

The toner of the present invention not only has a high electrical resistivity (it shows good chargeability in any of the development methods mentioned above, but also has good charging properties in any of the above development methods. In particular, it is based on high electric field conductivity under a high electric field of 104 to 105 V/c+++). It is possible to apply a uniform polarity and stable charge of about 5 μC/f or more by conducting charge injection or by injecting a high electric field charge from the band II electrode placed just before the phenomenon region. , it is possible to obtain a clear image without any unevenness or fogging.The reason for this is not necessarily clear, but the composition and structure of the toner particle surface are made uniform, and the macroscopic inside of the toner particle is The dispersion structure and the structure of the interfacial phase between the microscopic magnetic material and the binder resin are significantly different from conventional magnetic toners, and the generation, movement, and trapping of electric charges on the surface and inside of the magnetic toner particles are delicate. It is presumed that this is because it is controlled by

The magnetic toner of the present invention is not necessarily safe to use as a one-component developer (but can be used as a mixture of two or more types of magnetic toner).
Alternatively, it may be used as a component of a developer consisting of a mixture of magnetic toner and non-magnetic toner. In this case, the so-called "
It may have the function of a "toner", or conversely, it may have a so-called "carrier" function whose main purpose is to charge the "toner".

It may also be used as a two-component developer. Also, by utilizing its magnetism, it can of course be used as an agent for producing a magnetic AF phenomenon.

In the magnetic toner composition of the present invention, the electric resistivity is determined by placing the toner as a powder between electrodes with a diameter of 50 mm and a diameter of 200 mm.
10 with a load of f/- and a distance of about 1 between the electrodes.
Apply a voltage of 00 V and calculate the current value for 1 minute after applying the voltage as IO.
' It is converted into electrical resistivity in an electric field of V/cyn.

As mentioned above, silane coupling agents are conventionally used, but in this case, the plan coupling agent chemically bonds to the surface of the magnetic material, but there is a gap between the resin and the silane coupling agent. There is only affinity and no chemical bond ().

In other words, in the conventional method, a chemical bond cannot be formed between the surface of the magnetic material and the resin, but in the present invention, a chemical bond can be formed between the surface of the magnetic material and the resin, which makes a big difference in the effect. It has emerged.

In the case of conventional toner compositions in which the 7-rank coupling agent merely covers the surface of the magnetic powder and is chemically bonded, the magnetic powder surface itself is not exposed to the toner surface, but there is a bond between the 7-rank coupling agent and the resin. becomes the grinding interface, and the magnetic powder covered with the silane coupling agent is exposed. For this reason, breakdown occurs during transfer under a high electric field, making it impossible to perform transfer that maintains high resistance. In addition, the photoreceptor is abraded due to the magnetic powder trapped in the silane coupling agent. On the other hand, when the toner composition of the present invention has a three-dimensional chemical bond between the surface of the magnetic powder, the silane coupling agent, and the resin, the pulverized interface is in the oil layer, and the magnetic powder is It is not exposed to the toner surface, and high resistance is maintained even during transfer in a high I field, allowing good transfer. Furthermore, the classification efficiency of the toner is increased by 2, and the fluidity, moisture resistance, and impact resistance are further improved. In contrast to conventional toner compositions in which there is no bond between the silane coupling agent and the resin, the blocking resistance deteriorates, the toner composition of the present invention with three-dimensional bonding improves the blocking resistance. .

The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In addition, the parts shown in the following examples mean heavy liquid parts unless otherwise specified.

Examples and Comparative Examples 90 parts of styrene, 5 parts of methyl methacrylate, 7 parts of vinyltriethoxylate, and 5 parts of norane were polymerized to obtain a copolymer resin having an IT average molecular weight of 30,000 and a number average molecular weight of 5,000. 100 parts of this resin and triiron tetroxide (
150 parts of EPT-500 (manufactured by Toda Kogyo) were melt-kneaded for 10 minutes using a rotor-rotating mixer, cooled, and crushed.
It was pulverized to 14 to 15 μm using a jet pulverizer. 5 more
Particles with a particle size of 40μ or more are both in one layer! Air classification was performed so that the particle size was t% or less and the average particle size was 15μ. Furthermore, 0.00% per 100 parts of this toner.
5 parts of carbon black were mixed in a V-type blender to obtain a toner (Toner A).

For comparison, 90 parts of styrene and 5 parts of methyl methacrylate were polymerized to obtain a copolymer resin having a weight average molecular weight of 30,000 and a number average molecular weight of 5,000, and using this resin, Toner B and Toner C in Section F were prepared. did.

Toner B was prepared by melting and kneading the above resin (95 parts vinyltriethokinosilane 5 parts triiron tetroxide (Toda Kogyo gEPT-500) 150 parts for 10 minutes in a rotor-rotating kneader, and using the same trowel as for Toner A). did.

Toner Ckl Migami f4F2 resin 100 parts triiron tetroxide (Fgetsu Kogyo 1 building EPT-500) 15
0 part was melted and mixed in a σ-tar rotary kneader IC,
Thereafter, it was prepared in the same manner as Toner A.

- A component developer and a magnetic roll cleaner were installed in a Seiko photocopying machine (Fuji Xerox 2300), and copies were made using these toners for evaluation. The results are shown in Table 1 along with data on classification yield, electrical resistivity, and blocking resistance.

Blocking resistance was determined by leaving the sample in an environment at 50° C. for 1 hour and examining the presence or absence of blockade.

Claims (1)

[Scope of Claims] 1. In a magnetic toner composition containing a binder resin and a magnetic material as essential components, the binder resin is a copolymer containing a monomer component that can chemically bond to the surface of the magnetic material. A magnetic toner composition characterized by: 2. Claim 1, wherein the monomer component capable of chemically bonding to the surface of the magnetic material is a vinyl-substituted 7-run coupling agent.
The magnetic I-ner composition described in 1.