JPH05100496A - Magnetic particles and production thereof - Google Patents

Abstract

PURPOSE:To provide homogeneous magnetic particles having excellent flowability, durability, electrostatic chargeability and blocking resistance, ensuring high productivity and compatible with a toner negative polarity when used as a carrier. CONSTITUTION:When magnetic particles are produced by dispersing magnetic powder in resin particles, the resin particles are obtd. by bringing a polymerizable monomer, a silicone compd. having a group capable of reacting with the monomer and a crosslinking agent into a polymn. reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic particles in which magnetic powder is dispersed in resin particles and a method for producing the same, and more specifically, in electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to magnetic particles for developing an electrostatic latent image or a magnetic latent image and a method for producing the same.

[0002]

2. Description of the Related Art Generally, in electrophotography or electrostatic recording, coloring is performed in order to develop an electrostatic latent image formed on a latent image carrier made of a photoconductive photoconductor or a dielectric. A two-component developer composed of fine powder toner and carrier is widely used.

This two-component developer rubs the toner and the carrier by stirring to charge the toner to a specific polarity, and utilizes the electrostatic attraction between the electrostatic charge forming the electrostatic latent image and the toner. Develop by adhering to the latent image carrier.
This two-component developer is characterized in that it is possible to form a sharp visible image because the triboelectric charge control of the toner is relatively easy and the developer can be provided with sufficiently high fluidity.

The properties required for the carrier used in this two-component developer are charging property, impact resistance, abrasion resistance and spent resistance.

However, the carriers currently used are
It does not sufficiently satisfy the above characteristics. For example, conductive carriers such as iron oxide powder are excellent in solid developability but inferior in fine line reproducibility, and it is necessary to include a special charge control agent in the toner in order to extend the life. It has drawbacks such as On the other hand, an insulating carrier having a surface coated with an electrically insulating resin is excellent in life and reproducibility of fine lines, but has a drawback that it is inferior in solid developing property.

For the purpose of improving these drawbacks, a carrier having a small particle size in which magnetic powder is dispersed in a binder resin particle has been proposed, and in order to improve the fluidity of the carrier, JP-A-6-61 has been proposed.
3-30864, JP-A-63-30865, and JP-A-63-58360 propose a carrier in which a fluororesin is added to a binder resin and kneaded.

[0007]

However, in the above magnetic powder-dispersed carrier, since the binder resin and the fluororesin are kneaded, both resins are separated and the added fluororesin is likely to fall off. When the carrier obtained in this manner is used as a developer, the fluidity of the carrier is lowered due to the use, so that the chargeability of the toner becomes low and toner scattering and fog occur. In addition, since the carrier has poor blocking resistance, white streaks are likely to occur in the image. Further, since the toner is spent, the carrier surface is contaminated and the life of the carrier is shortened. Further, since the fluororesin is used, the resulting carrier has a strong charging property and has a negative polarity, which is suitable for a positive polarity toner but not for a negative polarity toner. In addition, a step of kneading the fluororesin with the binder resin is required, which lowers productivity.

The present invention is intended to solve the above-mentioned drawbacks, and its purpose is excellent in fluidity, durability, chargeability, blocking resistance and spent resistance, and is homogeneous and has good productivity. Therefore, when used as a carrier, it is to provide magnetic particles that are compatible with a toner having a negative polarity.

[0009]

The magnetic particles of the present invention are
Magnetic particles in which magnetic powder is dispersed in resin particles,
A resin forming the resin particles, a polymerizable monomer, and a silicone compound having a group capable of reacting with the polymerizable monomer,
It is characterized by containing a polymer comprising a cross-linking agent, whereby the above-mentioned object is achieved.

The method for producing magnetic particles of the present invention is a method for producing magnetic particles in which magnetic powder is dispersed in resin particles, which comprises a polymerizable monomer and a group capable of reacting with the polymerizable monomer. The above-mentioned object can be achieved by carrying out suspension polymerization of a composition containing a silicone compound having a, a cross-linking agent and magnetic powder in an aqueous medium.

Next, the invention will be described in detail.

The polymerizable monomer used in the present invention includes, for example, styrenes such as styrene, chlorostyrene and vinylstyrene: monoolefins such as ethylene, propylene, butylene and isobutylene: vinyl acetate,
Vinyl esters such as propylene vinyl, vinyl benzoate, vinyl butyrate: methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Esters of α-methylene aliphatic monocarboxylic acids such as dodecyl methacrylate: Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether:
Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-
Multivalent such as butanediol, neopentyl glycol, 1,4-butenediol, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropyleneated bisphenol A Alcohol: ethylenediamine, tetramethylenediamine, pentamethylenediamine, piperazine, hexamethylenediamine and other polyvalent amines: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, Cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid and other polycarboxylic acids or their acid anhydrides or esters with lower alcohols: aliphatic, alicyclic, aromatic diisocyanates, etc. It is. In the case of the above-mentioned polyhydric alcohol, polyhydric amine, polyhydric carboxylic acid and diisocyanate, a polymer having a hydroxyl group, an amino group, a carboxyl group and an isocyanate group at substantially both ends is preferable. These compounds may be used alone or in combination of two or more.

The silicone compound having a group capable of reacting with the polymerizable monomer used in the present invention contains an unsaturated bond such as a vinyl group, a hydroxyl group, an amino group, a carboxyl group, a diisocyanate group and an epoxy group. A silicone compound that does A silicone compound having a radically polymerizable vinyl group is particularly preferable. These compounds may be used alone or in combination of two or more.

The content of the silicone compound is preferably 1 to 30% by weight based on the total amount of the polymerizable monomer, the silicone compound and the crosslinking agent. When the content of the silicone compound is less than 1% by weight, the effect of improving fluidity and blocking resistance is poor. On the other hand, when the content of the silicone compound exceeds 30% by weight, the polymerization reactivity may be poor, the copolymerization reaction may not be completed, and the polymerizable monomer or the silicone compound may remain as a monomer. In addition, the resin may cause phase separation, and the characteristics of the magnetic particles may vary.

Examples of the cross-linking agent used in the present invention include divinyl compounds such as divinylbenzene, 1,5-hexadiene-3-yne, hexatriene, divinyl ether and divinyl sulfone; allyl phthalate, 2,6- Diallyl compounds such as diacrylphenol and diallyl carbinol; triallyl compounds, diacrylate compounds,
Triacrylate compounds, dimethacrylate compounds, trimethacrylate compounds, aldehydes, urea derivatives,
Examples thereof include glycols and diisocyanates. These crosslinking agents are appropriately selected depending on the type of polymerizable monomer used.

The amount of the cross-linking agent used is preferably 2 parts by weight or more based on 100 parts by weight of the total amount of the polymerizable monomer, the silicone compound and the cross-linking agent. When the amount of the cross-linking agent used is less than 2 parts by weight, the degree of cross-linking of the resin particles in the magnetic particles is low, and therefore when the magnetic particles are used as a carrier, the blocking resistance may be low.

The magnetic powder used in the present invention is a substance which is extremely strongly magnetized in that direction by a magnetic field, for example,
Metals such as iron, cobalt, nickel: Alloys or compounds containing ferromagnetism elements such as ferrite, magnetite, hematite, etc. such as ferrite, magnetite, hematite: Proper heat treatment without containing ferromagnetic elements An alloy exhibiting ferromagnetism, for example, manganese-
Heusler alloys containing manganese such as copper-aluminum or manganese-copper-tin and copper are listed.
These compounds may be used alone or in combination of two or more.

The amount of the magnetic powder used is preferably 50 to 300 parts by weight based on 100 parts by weight of the total of the polymerizable monomer, the silicone compound and the crosslinking agent. When the amount of the magnetic powder used is less than 50 parts by weight, when the obtained magnetic particles are used as a carrier, the magnetic attraction force of the developing sleeve is weakened, the carrier adheres to the photoconductor, and the developer spills from the developing machine. Is likely to occur. On the other hand, when the amount of the magnetic powder used exceeds 300 parts by weight, the binding effect of the resin cannot be sufficiently obtained and the magnetic particles are cracked. In addition, the dispersion of the contained powder such as magnetic powder may be deteriorated, and a homogeneous resin may not be obtained. The particle size of the magnetic powder is 0.01 to 5
μm is preferred.

The magnetic particles of the present invention may contain additives such as colorants and charge control agents, if necessary.

As the colorant, carbon black,
Aniline Blue, Calco Oil Blue, Chrome Yellow, Ultramarine Blue, DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green, Lamp Black,
Examples include rose bengal. These colorants may be used alone or in combination of two or more.

Examples of the charge control agent include Fettschwarz HBN having a positive triboelectric charging property described in JP-B No. 41-2427, nigrosine soluble in alcohol, Sudan Chief Schwarz BB, Solvent Black 3, Brilliant. Examples thereof include Spirit Schwartz TN, Zavon Schwarz X, quaternary ammonium compounds, Ceres Schwarz (R) G, which has a negative frictional charging property, Chromogen Syubalz ETOO, Azo Oil Black (R), Spiron Black, and Bontron. These charge control agents may be used alone or in combination of two or more.

When the magnetic particles of the present invention are used as the one-component developer for electrophotography, the colorant and the charge control agent are particularly effective.

The gel fraction of the magnetic particles of the present invention in acetone is preferably 95% or more. If the gel fraction in acetone is less than 95%, blocking resistance and fluidity may be reduced.

The glass transition point (Tg) of the magnetic particles of the present invention
Is preferably 0 ° C. or higher. When Tg is less than 0 ° C, blocking resistance and fluidity may be deteriorated.

The endothermic amount at the glass transition point of the magnetic particles of the present invention is preferably 1 J / g or less. When the endothermic amount at the glass transition point exceeds 1 J / g, the magnetic particles are likely to be softened at the glass transition point and carrier blocking may occur in the developing machine.

The volume expansion coefficient of the magnetic particles of the present invention with acetone is preferably 20% or less. When the volumetric expansion coefficient due to acetone exceeds 20%, there is a possibility that carrier cracking, carrier abrasion, magnetic powder falling off, and carrier blocking occur in the developing machine.

The degree of crosslinking of the magnetic particles of the present invention is preferably 4 mol% or more. When the degree of cross-linking is less than 4 mol%, the resin particles in the magnetic particles do not have hardness,
When these magnetic particles are used as a carrier, blocking resistance may be lowered.

The weight-based median diameter of the magnetic particles of the present invention is preferably 30 to 150 μm. If the weight-based median diameter is less than 30 μm, carrier attachment to the photoconductor or carrier drop from the developing machine may occur. On the other hand, when the weight-based median diameter exceeds 150 μm, the image density decreases, fogging occurs, white streaks (brush marks) occur due to scraping of the carrier on the image, and carrier blocking due to deterioration of fluidity occurs. May occur. The shape of the magnetic particles of the present invention is preferably spherical.

The magnetic particles of the present invention include the above polymerizable monomer,
It can be obtained by suspension polymerization of a composition containing the silicone compound, the crosslinking agent, and the magnetic powder in an aqueous medium.

The above-mentioned aqueous medium is usually water containing a small amount of a suspension stabilizer, and may also be a mixed solvent with alcohols and glycols.

If necessary, a polymerization initiator may be used in the above composition, and examples thereof include an azo polymerization initiator and a peroxide polymerization initiator.

A suspension stabilizer may be used in the above polymerization reaction, if necessary, and examples thereof include a surfactant, a poorly water-soluble fine powder, and a water-soluble polymer.

The above polymerization reaction is carried out at a reaction temperature of 60 to 100.
It is preferable to carry out the reaction at a temperature of 3 to 12 hours. The reaction between the polymerizable monomer and the silicone compound can be carried out by copolymerization, addition polymerization or polycondensation, and the polymer composed of the polymerizable monomer is modified with the silicone compound. But it's okay.

Since the magnetic particles of the present invention have excellent fluidity, they are particularly durable and electrostatically charged when used as a binder type carrier even in the fields of electrophotography, electrostatic recording, electrostatic printing and the like. The resulting image has excellent properties and can provide a good image.

[0035]

The magnetic particles of the present invention are formed by dispersing magnetic powder in resin particles obtained by a polymerization reaction of a polymerizable monomer and a silicone compound having a group reactive with the polymerizable monomer. Therefore, the surface energy of the magnetic particles is reduced and the fluidity of the magnetic particles is improved. The silicone compound is
Since it is chemically bonded to the polymerizable monomer, the characteristics of the magnetic particles do not significantly deteriorate with time.

Further, since the resin particles are made of a silicone compound as a material, the triboelectrification property of the obtained magnetic particles becomes positive and can be adapted to the toner of negative polarity.

Further, by using the crosslinking agent, the resin particles are highly crosslinked, and when the magnetic particles are used as a carrier, blocking can be reduced.

[0038]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 Styrene 70 parts by weight Butyl methacrylate 15 parts by weight Radical polymerizable silicone X-22-174D 5 parts by weight (manufactured by Shin-Etsu Silicone Co.) Divinylbenzene 2 parts by weight Diethylene glycol dimethacrylate 8 parts by weight Iron trioxide (BL) -100 Titanium Industry) 100 parts by weight Iron trioxide (BL-100 Titanium Industry) 100 parts by weight Titanate coupling agent (KR-TTS Ajinomoto Co.) 0.5 parts by weight 2,2'-azobis- (2. 4-Dimethylvaleronitrile) 6 parts by weight The above composition was mixed to prepare a composition. The above composition was added to a dispersion liquid obtained by adding 40 parts by weight of tricalcium phosphate and 0.5 part by weight of sodium dodecylbenzenesulfonate to 600 parts by weight of distilled water, and TK-Homomixer (made by Tokushu Kika Kogyo). Using a mixer with a modified high-viscosity leg, the mixture was stirred at 8000 rpm for 12 minutes. The obtained suspension was transferred to a separable flask and heated at 80 ° C under a nitrogen atmosphere.
Polymerization was completed by reacting for 5 hours while stirring at 250 rpm. After completion of the reaction, the polymer is filtered and treated with a dilute acid,
After washing with water, it was dried to obtain carrier particles. The particle size distribution of the obtained carrier particles was such that D50 was 73 μm.

Example 2 The same as Example 1 except that the amount of styrene was 65 parts by weight and the amount of X-22-184C was 10 parts by weight instead of the radically polymerizable silicone X-22-174D. Carrier particles were obtained by the operation of. The particle size distribution of the obtained carrier particles was such that D50 was 71 μm.

Comparative Example 1 Carrier particles were obtained in the same manner as in Example 1 except that the radical polymerizable silicone was not used and butyl methacrylate was 20 parts by weight. The particle size distribution of the obtained carrier particles was such that D50 was 71 μm.

92 parts by weight of the carrier obtained in each of Examples 1 and 2 and Comparative Example 1 and toner (DC-2585)
Toner for Sanda Kogyo) was mixed in an amount of 8 parts by weight to obtain a developer having a toner concentration of 8% by weight. DC-2 with this developer
At 585, a copy test of 20,000 sheets was conducted. The image density and charge amount of the initial developer and the developer after copying 20,000 sheets were measured, and the presence or absence of toner scatter, image white streaks due to carrier blocking, and toner spent were examined. The results are shown in Table 1.
Shown in.

[0043]

[Table 1]

From Table 1, the developers obtained in the Examples have good chargeability and image density even after copying 20,000 sheets, and there is no toner scattering, image white streaks due to carrier blocking, and toner spent formation. I understand.

[0045]

As is clear from the above description, in the present invention, the surface energy of magnetic particles is lowered,
Liquidity is improved. Therefore, when the magnetic particles are used as a binder type carrier, the following advantages are obtained in the repeated image formation. The releasability of the carrier from the photoconductor is improved, and the adhesion of the carrier to the photoconductor can be reduced. Since the chargeability of the carrier becomes good, the image density obtained from the developer using this carrier becomes good. Further, it is possible to prevent fogging and toner scattering. Since the blocking resistance of the carrier is improved, it is possible to prevent white lines from appearing on the image.
Since it is possible to prevent the spent toner, it is possible to prevent the carrier surface from being contaminated. Therefore, the durability of the carrier is improved. Furthermore, since the resin itself is provided with performance, the carrier using this resin becomes homogeneous. Such a carrier can be obtained by a simple process.

Further, since the resin particles are made of a silicone compound as a material, the triboelectric chargeability of the magnetic particles of the present invention has a positive polarity and can be adapted to a negative polarity toner.

Further, by using the crosslinking agent, the resin particles are highly crosslinked, and when the magnetic particles are used as a carrier, blocking can be further reduced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Tokuno 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Mita Industrial Co., Ltd. (72) Inventor Shigeo Yabe 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Issue Mita Industrial Co., Ltd.

Claims (3)

[Claims] 1. A magnetic particle in which magnetic powder is dispersed in a resin particle, wherein the resin forming the resin particle has a polymerizable monomer and a silicone having a group capable of reacting with the polymerizable monomer. Magnetic particles containing a compound and a polymer comprising a crosslinking agent. 2. The magnetic particle according to claim 1, wherein the magnetic particle is a binder type carrier. 3. A method for producing magnetic particles comprising magnetic particles dispersed in resin particles, wherein a polymerizable monomer, a silicone compound having a group capable of reacting with the polymerizable monomer, a cross-linking agent, and a magnetic powder. A method for producing magnetic particles, comprising suspension-polymerizing a composition containing: in an aqueous medium.