JPH03125156A - Toner for electrophotograhy - Google Patents

Abstract

PURPOSE:To obtain the toner which has superior offset resistance, toughness to mechanical wear, and excellent fixing performance by incorporating core toner and coating toner. CONSTITUTION:The toner contains the core toner which contains thermoplastic resin and a coloring agent and the coating toner which contains a toner component for coating the surface of the core toner and wax and the coating toner contains the 1 - 80 wt.% wax. The wax added in the toner becomes low- viscosity liquid immediately when heated and oozes to the toner surface to coat the toner, and consequently the separation between a fixing roller and the toner is increased to improve the adhesion to paper. Consequently, even toner which has low fixing performance, e.g. high-fusion-point toner with superior wear resistance can be improved in offset resistance and fixation to a subject by adding the wax. Further, the wax is mixed only in the coating toner to reduce the amount of the wax and caking, deterioration in flowability and the resulting decrease in electrostatic charging performance, filming on a photosensitive body, etc., at high temperatures are precluded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electrophotographic toner suitable for a heating roller fixing method.

(Prior Art) Generally, by using an electrophotographic copying machine, an electrostatic latent image formed on a photoreceptor drum is made visible using toner, and after this visible image is transferred to transfer paper, it is fixed. A copy image can be obtained by As methods for developing this electrostatic latent image, there are known methods such as a magnetic brush development method, a cascade development method, a fur brush development method, and a powder cloud method, but in these methods, the toner used is Because it is repeatedly subjected to severe mechanical impact, it deteriorates and produces fine toner particles after several thousand times of development. This causes negative effects such as fogging on the image and a reduction in triboelectric charging properties due to the fine toner being fused onto the surface of the carrier.

To prevent such toner deterioration, it is effective to use a resin that is strong against mechanical abrasion, that is, a resin with a large molecular weight, a crosslinked resin, etc., as a binder resin for the toner.

However, these resins generally have a high melting point, high elasticity, and poor affinity with transfer paper. Therefore, when these resins are used as binder resins for toner, it is necessary to efficiently apply a large amount of thermal energy in order to sufficiently fix the toner to the transfer target.

Contact-type heat fixing using a heating roller is well known as a fixing method with good thermal efficiency, and is currently widely used. However, when this heating roller is used, the heating roller comes into direct contact with the toner, so the heating roller
The molten toner adheres to the “surface” and this
A so-called offset phenomenon is likely to occur, which is a phenomenon in which dirt adheres from the heat roller to the subsequent transfer target. In order to prevent this phenomenon, the roller surface should be coated with a material with excellent mold release properties such as fluorine-based resin, silicone, oil, etc. One idea is to prevent toner from adhering to the roller surface. However, 1. These materials have problems in durability and storage stability when used continuously in high-temperature environments.

In addition, in order to sufficiently fix toner containing a resin with a high melting point such as the one mentioned above, it is necessary to raise the temperature of the heating roller, which may cause scorching and curling of the transfer slope. In addition, the material of the fixing device is limited, and a large amount of electric power is required. For this reason, it is desirable that toner for electrophotography be resistant to mechanical abrasion and fused to the subject at a relatively low temperature. In order to be able to fuse at a relatively low temperature, a resin with a small molecular weight may be used, but such a toner has poor abrasion resistance, which contradicts the purpose of preventing deterioration.

Further, toner for electrophotography is generally required to have a low melt viscosity in order to improve fixing properties. The reason for this is that if the melt viscosity of the toner is too high, the affinity of the toner with the support will be poor, and the toner will not be fused to the support, resulting in low-temperature offset and the like. On the other hand, if the melt viscosity of the toner is low, the affinity of the toner to the support is good, but all of the toner τ remains on the heating roller without being fused to the support, resulting in high-temperature offset, etc. There are cases where As described above, it has been difficult to produce an electrophotographic toner with excellent fixing properties without causing the offset phenomenon.

Therefore, in recent years, it has been proposed to add wax to toner to improve offset resistance and compatibility with the subject. However, in order to impart sufficient fixing properties to such toners, an excessive amount of wax is required, resulting in toner caking at high temperatures, a decrease in fluidity and resulting chargeability, and problems with the film on the photoreceptor. This causes harmful effects such as the formation of scratches.

(Problems to be Solved by the Invention) Therefore, in order to solve the above-mentioned problems, the present invention solves the problem of toner cake formation at high temperatures caused by adding wax, deterioration of fluidity, and accompanying decrease in chargeability. The purpose of the present invention is to provide an electrophotographic toner that minimizes adverse effects such as the formation of filming on a photoreceptor, has excellent offset resistance, is strong against mechanical abrasion, and has good fixing properties. .

Another object of the present invention is to provide an electrophotographic toner that can produce clear transferred images with less fog.

[Structure of the Invention] (Means for Solving the Problems) The toner of the present invention comprises a core toner containing a thermoplastic resin and a colorant as toner components, and a coating containing the toner components and wax that covers the surface of the core toner. toner, and the wax is contained in the coated toner in an amount of 1 to 80% by weight.

Examples of the wax used in the present invention include low molecular weight polypropylene, low molecular weight polyethylene, and low molecular weight olefin copolymers.

Such waxes may be present in the coated toner in an amount of 1 to 80% by weight.
If it is less than 1% by weight, the fixing properties and anti-offset properties will be insufficient, and if it exceeds 80ffl%,
This tends to cause problems such as caking at high temperatures, decreased fluidity, and formation of filming on the photoreceptor.

Thermoplastic resins include styrene, m-methylstyrene,
0-methylstyrene p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-n-hexylstyrene, p-tert-butylstyrene, p-n-octylstyrene, Styrenes such as p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, acrylic acid , methyl acrylate, ethyl acrylate, butyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate,
Monocarboxylic acids with double bonds such as acrylonitrile and methacrylonitrile and substituted products thereof, vinyl ketones such as vinyl methyl ketone and vinyl exyl ketone,
Homopolymers or copolymers of monomers such as vinyl ethers such as vinyl methyl ether, vinyl ethers, and -thyl, and vinyl esters such as vinyl chloride, vinyl acetate, and vinyl benzoate can be used. Also,
In the present invention, it is particularly preferable to add a crosslinking agent or a chain transfer agent to create branches in the molecule when polymerizing the resin, since this improves the abrasion resistance of the resin.

As the colorant, dyes and pigments commonly used in toners, such as carbon black, nigrosine, phthalocyanine blue, aniline blue, methylene blue, and quinoline yellow, can be used.

Furthermore, in order to improve the fluidity and agglomeration resistance of the colorant particles, hydrophobized colloidal fine particles having the same polarity as the coloring particles, such as colloidal silica, may be added, if necessary.

In order to improve the fluidity of colorant particles and stabilize the amount of charge, in addition to colloidal silica, aluminum oxide, nium oxide, titanium oxide, silicon oxide, zinc oxide, acids, and Inorganic and oxide materials such as magnesium, calcium oxide, tin oxide, indium, cerium oxide, and molybdenum trioxide, and silane coupling agents, titanium coupling agents,
Coupling agents such as coupling agents, inorganic oxides whose surfaces have been treated with silicone, oil, etc., styrenic copolymers such as polystyrene, styrene-butadiene copolymers, styrene-acrylic copolymers, polyethylene and ethereal Fats such as copolymers, polymethylmethac, rylates, etc.
Resin powders such as group or alicyclic copolymers, silicone resins, Te, Freon, etc. - Fine resin powders whose surfaces have been surface-treated with coating agents, silicone oil, etc., magnetic powders such as magnetite, ferrite, etc. May be added.

Note that the charged polarity of the colored particles in the present invention may be positive or negative.

In order to obtain the electrophotographic toner of the present invention, as shown in FIG. 1, the core toner 2 and the coated toner particles 1 are mixed in a weight ratio of 20:1 using a kneading machine such as a V-type blender, KR mixer, OM tizer, etc. After kneading to obtain the preliminary mixture 10, a method such as performing granulation treatment using a hybridizer, an ong mill, or the like is used. In this way, the electrophotographic toner 11 having the coated toner layer 3 is obtained. Furthermore, in addition to the mechanical method described above, electrostatic and thermal methods can also be used.

(Function) When heated, the wax added to the toner instantly turns into a low-viscosity liquid, oozes out onto the toner surface, coats the toner, improves the releasability of the toner from the fixing roller, and improves the adhesion to the paper. It has the function of improving. Therefore, even if the toner has low fixing properties, such as a high melting point toner with excellent abrasion resistance, the anti-offset properties and the fixing properties to the subject can be improved by adding wax. In addition, by mixing wax only in the coated toner, the amount of wax can be reduced to a small amount, which prevents toner caking at high temperatures, deterioration of fluidity and accompanying decrease in chargeability, and formation of filming on the photoreceptor. etc. can be prevented.

(Example) EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Softening point: 140°C, 100 parts by weight of cross-linked styrene-acrylic copolymer resin (thermoplastic resin), 6 parts by weight of carbon black MA-600 (manufactured by Mitsubishi Kasei - colorant), and 5-34 (Orient) 2 parts by weight of chemical observation (dye) were mixed and heated at about 130°C for 30 minutes using a pressure kneader.
After kneading for a minute, it is coarsely crushed and further
It was finely pulverized using a classifier (manufactured by Nippon Pneumatic), and a core toner having a 50% average volume particle size of 8.0 μm was obtained by wind classification. Next, 100 ffiffi parts of styrene-acrylic copolymer resin (crosslinked type), 50 parts of low molecular weight polypropylene Hymer 550P (manufactured by Kochu Kasei; wax)
6 parts by weight of carbon black MA-600 (manufactured by Mitsubishi Kasei ■) and S-34 (manufactured by Orient Chemical ■) were mixed, mixed and finely pulverized in the same manner as the core toner,
A coated toner having a 50% average volume particle size of 3 μm was obtained by wind classification.

Thereafter, the core toner and the coated toner were prepared in a weight ratio of 10=1 using a V-type blender for 60 minutes.

The obtained premix was passed through a Hosokawa Micron type Ong Mill A.
Fusion and granulation were performed using M-35 under the conditions of a rotor rotation speed of 1800 rpm and an inner rotation speed of 700 rpm.
A toner for electrophotography was obtained. This electrophotographic toner was mixed with Nippon Iron Powder Ferrite Carrier F-150 and toner specific density 4.
% to obtain a developer.

An image evaluation test was conducted using the obtained developer. The occurrence of fog and the decrease in image density were evaluated after continuous copying of 200,000 copies using a Toshiba Copying Machine RheoDry BD-9110. As a result, good images were obtained with little occurrence of fog or decrease in image density. The fixability was measured by rubbing a cloth under a load back and forth over the copied image, and expressing the ratio of image density before and after rubbing as a percentage. The results are shown in Table 1.

Example 2 An electrophotographic toner was obtained in the same manner as in Example 1, except that a styrene-acrylic copolymer resin (softening point: 150°C) having a higher molecular weight than that used in Example 1 was used. A developer was obtained. An image evaluation test was conducted using this developer. The results are shown in Table 1.

Comparative Example 1 Styrene-acrylic copolymer resin (softening point 140°C, crosslinked type) 100 parts by weight, Hymer 550P 4
Parts by weight, parts by weight of MA-6006, and 2 parts by weight of 5-34 were mixed, kneaded for 30 minutes at about 130°C using a pressure kneader, and then 50% average volume particle size of 12.0μ using a hammer mill.
A toner was obtained by finely pulverizing and classifying the powder to give a particle size of m. A developer was obtained using the obtained toner, and an image evaluation test was conducted.

The results are shown in Table 1.

Comparative Example 2 A toner was obtained in the same manner as in Comparative Example 1, except that 15 parts by weight of Hymer 550P, which is a wax component, was mixed. A developer was obtained using the obtained toner, and an image evaluation test was conducted. The results are shown in Table 1.

In the table, O indicates good, Δ indicates slightly poor, and X indicates poor.

As is clear from the table, when the toner of the present invention is used, good images without fogging can be obtained, and the fixing properties and offset temperature values are also good. However, as shown in Comparative Examples 1 and 2, wax If it is attached internally, the stability of death is poor.

[Effects of the Invention] As explained above, according to the present invention, toner cake formation at high temperatures caused by adding a large amount of wax,
It minimizes adverse effects such as deterioration of fluidity and accompanying decrease in chargeability, and the formation of filming on the photoreceptor, and has excellent offset resistance, strong resistance to mechanical abrasion, and good fixing properties. It is possible to provide a toner for electrophotography. Further, when the toner of the present invention is used, a clear transferred image with less fog can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a toner coating process according to an embodiment of the present invention. 1... Coated toner particles, 2... Core toner 3...
Covering toner layer, 10...prefr! Mixture, 11...
Toner for electrophotography

Claims (1)

[Claims] A core toner containing a thermoplastic resin and a colorant as toner components, and a coated toner containing the toner components and wax that covers the surface of the core toner, and the wax is contained in the coated toner in an amount of 1 to 80% by weight. An electrophotographic toner characterized by: