JPS60117259A - Positive-electrifiable magnetic material particle - Google Patents

Abstract

PURPOSE:To form positive-electrifiable magnetic material particles by depositing a copolymer of a monomer contg. a specific amino group and vinyl monomer copolymerizable with the monomer on the surface of the magnetic material particles thereby forming a coating layer. CONSTITUTION:A copolymer in which the copolymn. ratio of the unsatd. amide monomer contg. a tertiary amino group as shown in the formula is 0.5-50wt% is dissolved in an org. solvent and after magnetic material particles are dispersed into such soln., org. solvent is dried and evaporated away to form a copolymer layer like a film on the surface of the particles. The positive-electrifiable magnetic material particles produced in such a way are useful as a positive-electrifiable magnetic toner and positive-electrifiable carrier for electrophotographic development. Since said particles have a positive electrifying characteristic, the particles are suitable for an ordinary electrophotographic system in which the surface of a photosensitive body such as a cadmium sulfide photosensitive body or org. photosensitive body is negatively electrified and the copied image having good image quality is obtd. irrespectively of environmental conditions for copying and storage conditions for the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to positively chargeable magnetic particles and a magnetic toner and carrier for electrophotographic development using the magnetic particles.

In recent years, plain paper copies using electrophotography have been widely put into practical use. In the electrophotographic development system described above, the toner is triboelectrically charged by frictional mixing of the carrier and the toner, and the toner is fed onto the photoreceptor using the carrier as a transport medium. There is a method using a one-component developer that feeds toner directly onto the photoreceptor.

The toner of a one-component developer usually contains magnetic particles such as magnetite, and is transported and collected using magnetism.
Also in two-component developers, granular powder containing magnetic particles such as magnetite may be used as a carrier.

On the other hand, toner needs to be adjusted to be positively or negatively charged depending on the type of photoreceptor, and from this point of view, when considering magnetic particles such as magnetite, they have the characteristic of being negatively charged.

The characteristics of such magnetic particles are such that when used in a positively charged magnetic toner, a positively charged portion and a negatively charged portion coexist on the surface of one toner particle due to the presence of the magnetic particles exposed on the toner surface. It is presumed that the charging characteristics of each toner particle differs, and in one-component development systems that use magnetic toner, it is assumed that this is one of the causes of significant abnormalities in the characteristics of copied images depending on environmental conditions. It is desirable that the magnetic particles be positively charged.

In addition, in the two-component phenomenon method, when the toner is negatively charged by imparting positive charging characteristics to the carrier side and mixing it with the toner, it is necessary to positively charge the carrier, and from this point of view, the magnetic material in the carrier It is desirable to have the particles positively charged.

As a result of intensive research aimed at satisfying the above-mentioned demands, the present inventors have finally obtained the positively charged magnetic particles of the present invention.

That is, the present invention has a structure of the general formula (wherein R is hydrogen or an alkyl group, R' is an alkylene group, and R'' is an alkyl group, an alkenyl group, a substituted or unsubstituted benzyl group, or a cyclohexyl group). Monomer (hereinafter referred to as tertiary amino group-containing unsaturated amide)
Positive charging in which a coating layer is formed by depositing a copolymer of 0.5 to 50% by weight and 50 to 99.5% by weight of a vinyl monomer copolymerizable with the monomer on the surface of magnetic particles. The present invention provides a magnetic toner characterized by being a magnetic particle and containing the above-mentioned magnetic particle, and a carrier for electrophotographic development characterized by containing the above-mentioned positively charged magnetic particle.

The magnetic particles serving as the base material of the positively charged magnetic particles of the present invention include ferrites such as magnetite, γ-hematite, magnetite zinc monoxide double oxide, chromium oxide, cobalt-coated iron oxide, and reduced iron powder. Magnetite is particularly preferred from the viewpoint of color tone.

The size of the magnetic particles is usually preferably 1 μm or less and a specific surface area of 1 to 100 m 2 /g from the viewpoint of dispersibility and magnetic properties.

A component of the copolymer that coats the magnetic particles described above is a general formula (wherein R is hydrogen or an alkyl group with C=1 to 20, R'
is a C=1-20 alkylene group, R'' is a C=1-20 alkyl group, a C=1-20 alkenyl group, benzyl group, substituted (alkyl or halogen) benzyl group, C=1-20
Examples of monomers having a structure of 20 cycloalkyl groups include dimethylaminoethyl acrylamide, dimethylaminoethyl methacrylamide, diethylaminoethyl acrylamide, diethylaminoethyl methacrylamide, dimethylaminopropylacrylamide, dimethylaminopropyl methacrylamide, diethylaminopropyl Acrylamide, dimethylaminobutylacrylamide, methylbenzylaminoethylacrylamide, dimethylaminoethylmethylacrylamide, etc. are used.

In addition to the tertiary amino group-containing unsaturated amides specified in the present invention, examples of monomers containing a tertiary amino group include (meth) such as dimethylaminoethyl methacrylate, etc.
There is an acrylic acid ester-based substituent, and it is said that it is possible to impart positive chargeability, but it has a drawback that the chargeability changes over time due to its high hydrolyzability, so it is not suitable for the purpose of the present invention. I can't.

Monomers copolymerizable with the tertiary amino group-containing unsaturated amide monomer of the present invention include styrene, vinyltoluene,
Aromatic vinyl monomers such as α-methylstyrene and para-methylstyrene; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (meth)acrylate
Butyl acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, oleyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, (meth)acrylate (Meth)acrylic acid esters such as hydroxyethyl acid, hydroxypropyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, glycidyl (meth)acrylate; dimethyl fumarate, fumaric acid Esters of unsaturated dibasic acids such as dibutyl, monomethyl fumarate, monobutyl fumarate, dimethyl itaconate, dibutyl itaconate, dioctyl itaconate, monomethyl itaconate, monobutyl itaconate; vinyl esters such as vinyl acetate, vinyl propionate, etc. There are unsaturated nitriles such as acrylonitrile and methacrylonitrile, and these can be used alone or in combination. Further, it is also possible to copolymerize and use unsaturated carboxylic acids such as methacrylic acid, acrylic acid, and itaconic acid within a range that does not inhibit the positive chargeability that is the object of the present invention. Further, it is also possible to use monomers having two or more double bonds, such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and the like.

The copolymerization ratio of the tertiary amino group-containing unsaturated amide monomer in the above copolymer is 0.5 to 50% by weight. If it is less than 0.5% by weight, it is difficult to impart positive chargeability to the magnetic particles, which is the objective of the present invention, and if it exceeds 50% by weight, the hygroscopicity of the surface of the magnetic particles increases, possibly resulting in a decrease in the amount of charge. It is undesirable because the stability over time decreases, especially 2-
20% by weight is preferred. In addition. The remaining copolymerizable vinyl monomers are selected from one or more of the above-mentioned monomers, and aromatic vinyl monomers and (meth)acrylic acid esters are particularly preferred. preferable.

The above copolymers include peroxides, versalphates,
It is usually obtained by polymerization by methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization in the presence of a radical generator such as azonitrile.

In the present invention, the thus obtained copolymer is applied to magnetic particles such as those described above, and the surfaces of the particles are coated with the copolymer layer.

Any method can be used to coat the particle surface, but the following method is common, for example.

The first method is to dissolve the copolymer in a soluble organic solvent, disperse the magnetic particles in the solution, and then remove the organic solvent by drying and volatilizing it to form a copolymer layer on the particle surface. This is a method of forming a coating.

In the second method, magnetic particles are dispersed in an organic solvent, the above monomer is added, and the magnetic particles are polymerized while being dispersed, and then the organic solvent is removed in the same manner as in the first method. , which is also a method of forming a copolymer coating layer.

The third method is to mix the copolymer in a molten state without containing a solvent with magnetic particles, and similarly coat the particle surface with the molten copolymer.

The fourth method is disclosed in Japanese Patent Application No. 58-115148 by the present inventors.
As proposed in this issue, magnetic particles are dispersed in water, the monomers mentioned above are added and polymerized on the particle surface, and the water is removed by drying.

Although the purpose of the present invention can be achieved by any of the methods, the fourth method is particularly preferred from the viewpoint of coating the copolymer more uniformly and firmly on the surface of the magnetic particles, and from the viewpoint of operational safety in the coating process. preferable.

The amount of copolymer deposited on the magnetic particles (coating layer amount) is:
0.5-25% by weight is common. If it is less than 0.5% by weight, it is not sufficient to impart positive chargeability, and if it exceeds 25% by weight, the magnetic particles may aggregate due to the adhesive action of the copolymer. The dispersibility of the body particles becomes insufficient. In addition, the amount of coating is preferably 2 to 15% by weight.

The positively chargeable magnetic particles of the present invention obtained as described above are useful as positively chargeable magnetic toners and positively chargeable carriers for electrophotographic development.

The positively charged magnetic toner of the present invention is produced by a method known per se using the positively charged magnetic particles of the present invention. That is, styrene copolymer resin, acrylic copolymer resin,
A thermoplastic binder such as polyester resin, epoxy resin, styrene-butadiene copolymer resin, polyolefin resin, wax, and the positively charged magnetic particles of the present invention,
Furthermore, if necessary, colorants such as carbon black, charge control agents such as nigrosine that further impart positive chargeability to the toner, waxes that adjust release properties and fluidity, low-molecular polyolefins, fatty acid esters, fatty acid amides, An auxiliary agent such as a fatty acid metal salt may be kneaded in a molten state, cooled, and then finely pulverized, and a fraction having a particle size of usually 5 to 20 μm is selected to obtain a magnetic toner. The content of magnetic particles in the magnetic toner is generally 20 to 60% by weight.

Since the magnetic toner of the present invention has positive chargeability, it is suitable for ordinary electrophotographic systems in which the surface of a photoreceptor such as a sulfurized domium photoreceptor or an organic photoreceptor is negatively charged. This method has the advantage that the quality of the obtained copy is not easily affected even if the copying environment conditions and toner storage conditions change.

Further, the magnetic particles of the present invention are also useful as carriers for electrophotographic development.

The carrier is also manufactured by a method known per se, and includes, for example, styrene copolymer resin, acrylic copolymer resin, polyester resin, polycarbonate resin, polyamide resin, polyurethane resin, polyether sulfone resin, polyester sulfone resin, A thermoplastic resin such as a polyetheretherketone resin and the magnetic particles of the present invention are melt-mixed, and after cooling, the average particle size is usually 20 to 100.
It is obtained by pulverizing it to about 0 μm. The content of the magnetic particles in the carrier is generally 30 to 80% by weight.

The carrier has a positive charging property, and when mixed with the toner and rubbed, it imparts a negative charging property to the toner, and the electrostatic latent image that is positively charged on the surface, for example, the electrostatic latent image on the surface of a photoreceptor represented by selenium. It plays the role of supplying toner to the image and can provide high-quality copied images. By using the carrier of the present invention, there is no need to add a strongly negatively charged charge control agent to the toner, and there is also the effect that toner adhesion deterioration is less likely to occur when repeatedly used compared to carriers such as iron powder. is played.

As mentioned above, the positively charged magnetic particles of the present invention are extremely useful in applications such as magnetic toners and carriers,
Further, the magnetic toner and carrier containing the positively charged magnetic particles of the present invention exhibit extremely excellent performance for electrophotography.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 100 ml of deionized water was added to a reactor equipped with a reflux condenser and a stirrer.
0 parts by weight and magnetite (specific surface area 11 m2/g) 1
00 parts by weight was charged, the temperature was raised to 70°C with stirring, 5 parts by weight of ammonium persulfate was added, and then monomers consisting of the parts by weight listed in experiment numbers (1) to (10) in Table 1 were added. Each of the mixtures was added dropwise over 1 hour and stirred at the same temperature for an additional 3 hours, followed by filtration, washing with water, and drying to obtain magnetic particle samples (1) to (10) of the present invention. Each magnetic particle was subjected to elemental analysis, and the amount of copolymer deposited was estimated from the carbon atom analysis value, and the results are also listed in Table 1.

In addition, iron powder carrier (EFVI manufactured by Nippon Tetsuko Co., Ltd.) 9
5 parts by weight of each magnetic powder was mixed with 5 parts by weight of each magnetic powder, and the amount of charge was measured at 20°C and 60% relative humidity using a frictional electrification blow-off charge measuring device.
After being left in an environment with relative humidity of 95% for 48 hours, the amount of charge was measured in the same manner, and the results are also listed in Table 1.

As a result of the measurement, the magnetic particles of the present invention exhibited positive chargeability, and the attenuation of the positive chargeability was small even under high humidity.

Comparative Example 1 Regarding the magnetite itself used as a raw material in Example 1, the amount of charge was measured in the same manner as in Example 1, and the results are listed in sample number (11) in Table 1.

Comparative Example 2 A comparative example was prepared in which each part by weight of the monomer listed in the experiment number in Table 1 was used in place of the monomer listed in Example 1, and coated with a polymer in exactly the same manner as in Example 1. Magnetic particle sample (
12) to (13) were produced.

The amount of polymer deposited and the monomer were measured in the same manner as in Example 1, and the results are also listed in Table 1.

Example 2 Magnetic particles 4 of the present invention having each sample number described in Example 1
5 parts by weight, 50 parts by weight of styrene-n-butyl methacrylate copolymer resin (copolymerization composition; 70% by weight: 30% by weight, number average molecular weight 15,000), 2 parts by weight of carbon black, 2 parts by weight of polypropylene wax, and 1 part by weight of nigrosine. The mixture was melt-kneaded in a hot roll mill, pulverized in a jet mill, and then air classified to collect particles of 8 to 15 μm to obtain magnetic toner samples (1) to (10), respectively.

Regarding each magnetic toner sample, in the same manner as in Example 1, the amount of charge was measured initially and when left in a high humidity environment. The measurement results are listed in Table 2. Each magnetic toner exhibited positive chargeability, and the attenuation of the charge amount was small even in a high humidity environment.

In addition, each magnetic toner kept in a high humidity environment was copied using an electrophotographic copying machine using a cadmium sulfide photoreceptor, and the state of capri (stains due to toner adhesion to non-image areas) in non-image areas was examined. The results are also listed in Table 2. It can be seen that when each of the magnetic toners of the present invention is used, good copy image quality can be obtained with less fog in non-image areas.

Comparative Example 3 Magnetic particles with sample numbers (11) to (14) described in Comparative Examples 1 and 2 were used instead of magnetic particles of the present invention with sample numbers (1) to (10), and other magnetic particles were used. Each magnetic toner sample was manufactured and evaluated in exactly the same manner as in Example 2.

The evaluation results are listed in Table 2.

Table 2 Example 3 50 parts by weight of magnetic particles of sample number (4) described in Example 1 and polystyrene resin (number average molecular weight 65,000)
After melt-kneading and pelletizing 50 parts by weight using an extruder, pulverization using a ball mill, and 30 parts by weight using a wire mesh classifier.
The carrier of the present invention was prepared by removing particles below 0 mesh and above 150 mesh.

On the other hand, styrene, butyl methacrylate, methacrylic acid (
Example 93 parts by weight of a copolymer having a copolymer composition of 70% by weight: 28% by weight: 2% by weight, number average molecular weight 17,000), 5 parts by weight of carbon black, and 2 parts by weight of polypropylene wax were melt-mixed. A two-component toner was produced in the same manner as in Example 2.

95 parts by weight of the above carrier and 5 parts by weight of the above toner were mixed, and the initial charge amount and the charge amount after being left in a high humidity environment were measured in the same manner as in Example 1. As a result, each was -16.6 μc.
/g and -16.3 μc/g, the toner could be sufficiently negatively charged, and there was only a slight change in the amount of charge in a high humidity environment. That is, it was found that the carrier has positive chargeability.

Furthermore, as a result of evaluating copied images using an electrophotographic copying machine using a selenium photoreceptor, it was found that even after mixing the above toner and carrier and leaving the mixture under high humidity under the same conditions as in Example 1,
A high-quality copy image without fogging was obtained. Note that the above carrier and toner mixture are sealed in a glass container,
Although mixing was carried out in a shaker for 480 hours, no fusion of the toner to the carrier surface was observed by microscopic observation, and the amount of charge of the toner was 14.9 μc/g.

Comparative Example 4 A comparative carrier was produced in the same manner as in Example 3, except that untreated magnetite of sample number (11) was used instead of the magnetic particles of sample number (4) in example 3. .

Using the toner described in Example 3, the toner charge amount was measured in the same manner, and the initial charge amount was -3.2 μc/g.
After being left in a high-humidity environment, the toner exhibited slight negative chargeability at -2.4 μc/g, but in the evaluation of copied images such as in Example 3, the contrast between image and non-image areas was low, probably due to the small amount of charge. It was extremely poor, and when trying to increase the image density, a significant fogging phenomenon occurred.

Comparative Example 5 5 parts by weight of the toner described in Example 3 and 95 parts by weight of an iron powder-based carrier (manufactured by Nippon Iron Powder Co., Ltd., trade name EFVI) were mixed,
As a result of measuring the charge amount of the toner in the same manner as in the example, the initial charge amount -10.9μc/g after being left in a high humidity environment -7.8μ
c/g showed negative charging, but in the same evaluation of copied images as in Example 3, fogging occurred.

Further, when the above-mentioned mixture of toner and carrier was mixed for a long time in the same manner as in Example 3 and observed under a microscope, it was found that the adhesion of the toner to the carrier surface was remarkable and the toner charge amount was 4.5 μc/g. .

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] (1) Monomer having the structure of the general formula (wherein R represents hydrogen or an alkyl group, R' represents an alkylene group, and R'' represents an alkyl group, an alkenyl group, a substituted or unsubstituted benzyl group, or a cyclohexyl group) A copolymer of 0.5 to 50% by weight of a vinyl monomer and 50 to 99.5% by weight of a vinyl monomer copolymerizable with the monomer was deposited on the surface of the magnetic particles to form a coating layer. Positively charged magnetic particles. (2) Monomer 0 having the structure of the general formula (wherein R is hydrogen or an alkyl group, R' is an alkylene group, and R'' is an alkyl group, an alkenyl group, a substituted or unsubstituted benzyl group, or a cyclohexyl group) .5 to 50% by weight and 50 to 99.5% by weight of a vinyl monomer that is copolymerizable with the monomer, and a positive charging property in which a coating layer is formed by depositing a copolymer on the surface of magnetic particles. A magnetic toner for electrophotographic development containing magnetic particles. (3) Monomer 0 having the structure of the general formula (wherein R is hydrogen or an alkyl group, R' is an alkylene group, and R'' is an alkyl group, an alkenyl group, a substituted or unsubstituted benzyl group, or a cyclohexyl group) .5 to 50% by weight and 50 to 99.5% by weight of a vinyl monomer that is copolymerizable with the monomer, and a positive charging property in which a coating layer is formed by depositing a copolymer on the surface of magnetic particles. A carrier for electrophotographic development containing magnetic particles.