JPH07160059A - Coated carrier for electrostatic latent image development - Google Patents

Abstract

PURPOSE:To provide a carrier for an electrostatic latent image development, while having stable resistance and electrified capability regardless of use over a long term, and thus capable of stably producing a high quality image without any deterioration of development characteristics over a long term. CONSTITUTION:This carrier has a surface coated layer made of at least resin and a resistance adjusting agent and is characteristic in that the layer is formed to have smaller resistance toward the surface. Another characteristic point is that in case measured electrical field is equal to 5,000V/cm, the resistivity of the coated carrier having the predetermined thickness of a coated layer is between 1 and 10<4> times, compared with the resistivity of a carrier having a coated layer 0.5mum less than the prescribed thickness. Another characteristic point is that carbon black is used as the resistance adjusting agent of the coated layer, and silicone resin is used as resin for forming the layer, while the concentration of a silane coupler and/or organic tin compound solvent has a gradient along the thicknesswise direction of the coated layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component dry developer carrier for visualizing an electrostatic latent image formed by electrophotography, electrostatic recording or electrostatic printing. Is.

[0002]

2. Description of the Related Art Conventionally, a two-component dry developer comprising a mixture of carrier particles and toner particles has been well known. In this two-component dry developer, minute toner particles are held on the surface of a relatively large carrier particle by an electric force generated by friction between the particles, and when the developer approaches an electrostatic latent image, The toner particles are attracted toward the latent image by the electric field formed by the latent image, and this attractive force overcomes the binding force between the toner particles and the carrier particles, so that the toner particles are attracted and adhered onto the electrostatic latent image to form the electrostatic latent image. The image is visualized. Then, the developer is repeatedly used while replenishing the toner consumed in the development. Therefore, the carrier must always tribocharge the toner particles to a desired polarity and to a sufficient amount of charge during long-term use. On the other hand, in the conventional developer, a toner film is likely to be formed on the carrier surface due to collision between particles, collision between particles and a developing device component, and heat generated by these collisions. Since the characteristics deteriorate with the use time, it becomes necessary to replace the entire developer.

In order to prevent the occurrence of spent, there have been proposed methods for coating the surface of a carrier with various resins, but no satisfactory method has been obtained yet. For example,
A carrier coated with a resin such as a styrene-methacrylate copolymer or a styrene homopolymer has excellent charging characteristics, but since the surface tension of the surface is relatively high, it causes spent when used repeatedly, and thus becomes a developer. Life is not that long. Further, the carrier coated with a tetrafluoroethylene polymer has a low surface tension, so that the toner is less likely to be spent, but since the tetrafluoroethylene polymer is located on the most negative side in the triboelectric charging series, It cannot be used when negatively charging the toner.

As a carrier having a low surface tension, a carrier coated with a coating layer containing a silicone resin has been proposed. For example, an unsaturated silicone resin, organosilicone, silanol, etc. are mixed with a styrene-acrylic resin to coat the carrier surface (US Pat. No. 3,562,562).
533); a carrier whose surface is coated with a polyphenylene resin and an organosilicone terpolymer resin (US Pat. No. 3,847,127); styrene-acrylate-
Methacrylate resin, organosilane, silanol,
A carrier whose surface is coated with siloxane or the like (U.S. Pat. No. 3,627,522), a carrier coated with a silicone resin and a nitrogen-containing resin having a positive charging characteristic (JP-A-55-55).
No. 127567); and a carrier whose surface is coated with a modified silicone resin (JP-A-55-157751). Furthermore, JP-A-60-20135
No. 9 discloses a method of forming a coating layer with a silicone resin using an organotin compound as a catalyst in order to prevent the silicone coating layer from being reduced during long-term use and thus changing the charging ability of the silicone-coated carrier. In addition, a method of providing a gradient of the catalyst concentration in the thickness direction of the coating layer has been proposed.

Generally, the resistance of the core material used for the coated carrier is low and the resistance of the material used for the coating layer is high. Therefore, the resistance of the carrier can be adjusted by coating the surface of the carrier. Therefore, in order to adjust the resistance by the thickness of the coating layer, carbon black (JP-A-56-126843) is used in the coating layer.
No. JP-A-62-45984); metal oxides such as tin oxide, titanium oxide and zinc oxide (JP-A-64-35).
No. 561) and the like); and the like, the resistance of the carrier is adjusted by a method of adjusting the resistance of the coating layer to prevent the carrier from adhering to the edge portion of the development area during high bias development, and at the time of low bias development. Methods have been proposed to prevent carriers from adhering to the image area. However, even if the initial carrier resistance is adjusted by such a method, the coating layer will be reduced due to friction and falling off during long-term use.
There remains a problem that the resistance of the carrier gradually decreases and the carrier adheres to the image area.

[0006]

SUMMARY OF THE INVENTION The present invention has a close relationship between the life of the developer and the resistance and charging ability of the carrier. Therefore, even if the developer is used for a long period of time, the resistance and charging ability of the carrier always remain constant. It is an object of the present invention to provide a highly durable carrier for a developer which is stable and therefore can stably form a high quality image without deteriorating the developing characteristics.

[0007]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, in a coated carrier having a coating layer composed of at least a resin and a resistance control agent on the surface, the specific resistance of the coating layer is formed so as to become lower as the surface of the coating layer. A carrier for developing an electrostatic latent image is provided. Further, according to the present invention, in the above-mentioned coated carrier, the measured electric field is 5,000 V / c.
In the case of m, the specific resistance of the coated carrier having the coating layer of the predetermined thickness is 1 to 10 ⁴ times the specific resistance of the coated carrier having the coating layer of 0.5 μm thinner than the predetermined thickness. A coated carrier for developing an electrostatic latent image is provided. Note that the specific resistance of the coated carrier is the specific resistance when the aggregate of coated carriers is handled as a homogeneous block, so even if the material of the coating layer is homogeneous in all coating layers, the film thickness of the coating layer The specific resistance value measured by fluctuates.

Further, according to the present invention, there is provided the above coated carrier for developing an electrostatic latent image, wherein the resistance adjusting agent of the coating layer is carbon black. Furthermore,
According to the present invention, in the above-mentioned coated carrier using carbon black as a resistance adjusting agent, the coating layer is formed of a silicone resin containing a silane coupling agent, and the concentration of the silane coupling agent becomes higher as the surface of the coating layer increases. A coated carrier for developing an electrostatic latent image, characterized in that the concentration of the organotin compound for a catalyst which is formed and / or may be contained has a concentration gradient in the thickness direction of the coating layer. Provided. That is, in the carrier of the present invention, a resin film having a high resistance is formed in the vicinity of the core material of the coating layer with almost no addition of the resistance adjusting agent. The basic idea is to lower the resistance.
Further, a silicone resin is used for the coating layer, and the amount of the silane coupling agent added when forming the coating layer with the resin and the amount of the organotin compound catalyst used for forming the coating layer are adjusted. The resistance of the carrier does not change even when the coating layer is worn over a long period of time, and at the same time, the charging characteristics such as the triboelectric charge amount of the toner do not change.

Next, the difference in specific resistance between the carrier of the present invention and the conventional coated carrier will be described with reference to the drawings. FIG. 1 schematically shows the specific resistance of the coating layer of the carrier of the present invention and the conventional coated carrier. Although the specific resistance of the coating layer is constant in the conventional product, the specific resistance of the coating layer of the carrier of the present invention is constant. It can be seen that the resistance is lower on the outer surface of the layer. FIG. 2 schematically shows the specific resistances of the carrier of the present invention and the conventional coated carrier. In the conventional product, the specific resistance of the coated carrier aggregate sharply decreases as the coating layer becomes thinner, and therefore the predetermined film thickness is obtained. It can be seen that the resistivity of the coated carrier having a thinner coating layer of 0.5 μm is several orders of magnitude lower than that of the conventional product.

As described above, in the carrier of the present invention, the specific resistance of the coating layer is as low as that of the surface, so that even if the coating layer is worn and thinned, the specific resistance does not decrease as compared with the conventional product. Then, when the measured electric field is 5,000 V / cm, the specific resistance of the carrier having the coating layer having a predetermined thickness is at least one time that of the case where the coating layer having a thickness of 0.5 μm is thinner than the coating layer. The specific resistance of the coating layer may be adjusted so as to be 10 ⁴ times or less, preferably 1 time or more and 10 ² times or less. The reason why the measured electric field is specified is that the specific resistance of the high-resistance powder easily depends on the electric field. The carrier of the present invention is a method of gradually changing the type and amount of the resistance adjusting agent of each layer in a coating layer having a multilayer structure, or a method of continuously changing the type and amount of the resistance adjusting agent in a single film during coating. The latter is preferred. Further, in the present invention, a conductive material such as carbon black or metal oxide is used as the resistance adjusting agent, but the former which is effective in a small amount is preferable. Then, a coating layer forming liquid in which one or more of the resistance modifiers are dispersed may be used to form a coating layer on the carrier surface by a spraying method, a dipping method, or the like.

In the carrier of the present invention, when the coating layer is made of a silicone resin, the surface energy is lowered and the spent toner is suppressed. Further, when the resistance adjusting agent is added to the coating layer, a silane coupling agent is added to perform stable fine dispersion of the resistance adjusting agent. Therefore,
When the amount of the resistance adjusting agent is increased on the surface, it is desirable to increase the amount of the silane coupling agent on the surface according to the amount of the resistance adjusting agent. By doing so, fine dispersion of the resistance adjusting agent is more stable. And the charging ability is stabilized. Further, when the coating layer contains a resistance adjusting agent, the larger the amount thereof is, the lower the resistance of the coating layer is, so that the absolute value of the charging ability becomes smaller. However, when the coating layer is made of a silicone resin containing a silane coupling agent, the absolute value of the charging ability can be adjusted by changing the amount of the organotin compound catalyst. This is because the free silane coupling agent changes the chargeability of the carrier, and the silane coupling agent that has reacted with the silicone resin does not affect the chargeability of the carrier. Is reduced. Therefore, in a developer comprising an aminosilane coupling agent and a negatively chargeable toner, which increase the positive chargeability of the carrier, the negative chargeability is improved by increasing the amount of the catalyst, and when the toner is combined with the negatively chargeable toner, the amount of the catalyst is decreased. Positive charging property increases. On the other hand, when a chlorosilane coupling agent that increases the antistatic property of the carrier is used, the opposite result is obtained. Therefore, the chargeability can be stabilized by changing the amount of catalyst depending on the chargeability of the toner used and the type of silane coupling agent.

As described above, the coating layer of the carrier of the present invention has a specific resistance changed stepwise or continuously. In the coating layer having a multi-layered structure, the kind and amount of the resistance adjusting agent are changed so that the surface layer has a stepwise change. The coating layer is formed to have low resistance. In addition, when continuously changing the resistance in a single film, after starting coating layer formation using a coating layer forming liquid in which a low-efficiency resistance adjusting agent is dispersed, high concentration resistance adjustment is performed during coating layer formation. The coating layer may be formed by a method such as gradually adding a liquid containing the agent to the coating layer forming liquid, thereby gradually increasing the concentration of the resistance adjusting agent in the forming liquid. In this case, the resistance adjusting agent may be used alone or in combination of two or more kinds, or an additive such as a dispersion aid of the resistance adjusting agent may be added. When a silicone resin containing a silane coupling agent or an organotin compound catalyst is used as the coating layer forming material, the concentration of the silane coupling agent or the organotin compound catalyst may have a gradient.

Resins suitable for forming the coating layer of the carrier of the present invention include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polyacrylates such as polystyrene and polymethylmethacrylate, polyacrylonitrile and polyvinyl acetate. Polyvinyl and polyvinylidene resins such as polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; copolymers such as vinyl chloride-vinyl acetate copolymers and styrene-acrylic acid copolymers; organo Silicone resin composed of siloxane bond or its modified resin (for example, modified resin by alkyd resin, polyester resin, epoxy resin, polyurethane, etc.); polytetrachloroethylene , Polyvinyl fluoride, polyvinylidene fluoride, chloro tri full Lol ethylene and fluorine resins, polyamides, polyesters, polyurethanes, polycarbonates; -; epoxy resins such as urea amino resins such as formaldehyde resin. The resin preferable from the viewpoint of preventing spent of the toner is a silicone resin or its modified resin or a fluororesin, and the former is particularly preferable.

Known silicone resins are used for forming the coating layer, and straight silicones having an organosiloxane bond represented by the following formula (I) and modified silicone resins modified with alkyd, polyester, epoxy, urethane and the like are particularly preferable. preferable.

[Chemical 1]

R ₁ in the above formula (I) represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, and R ₂ and R ₃ may be the same or different, but these are hydrogen atoms, An alkoxy group having 1 to 4 carbon atoms, a phenol group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms or an alkenyloxy group, a hydroxy group, a carboxyl group, an epoxy ring, a glycidyl group or a group represented by the following formula (II): It represents.

[Chemical 2] R ₄ , R ₅ , R ₆ and R ₇ in the above formulas (I) and (II) may be the same or different, but these are a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms or an alkoxy group. Represents a group, an alkenyl group having 2 to 4 carbon atoms or an alkenyloxy group, or a phenyl group, k, l, m, n, o,
p represents an integer of 1 or more.

Each of the above-mentioned substituents may be unsubstituted or may have a substituent such as an amino group, a hydroxy group, a carboxyl group, a mercapto group, an alkyl group, a phenyl group, an epoxy ring, a glycidyl group and a halogen atom. Good. The trade names of the coating layer-forming silicone resin described above are as follows. That is, commercial products of straight silicone resin are KR271 and KR125 manufactured by Shin-Etsu Chemical Co., Ltd., SR2411, SR2405 manufactured by Toray Dow Corning Silicone Co., Ltd., and commercial products of modified silicone resin are KR206 (Shin-Etsu Chemical Co., Ltd.). Alkyd modified), KR5208 (acrylic modified), ES1
001N (epoxy modified) and KR305 (urethane modified), SR2 made by Toray Dow Corning Silicone
115 (epoxy modified) and SR2110 (alkyd modified).

The silane coupling agent used in the present invention is r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane. , N-β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxy Silane, vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammoni Mukuroraido, r- chloropropyl methyl dimethoxy silane, methyl trichlorosilane, dimethyl dichlorosilane, trimethylchlorosilane (manufactured by Toray Silicone Co.), allyl triethoxysilane, 3-aminopropyl methyl diethoxy silane,
Examples thereof include 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyldisilazane, methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (above, manufactured by Chisso Corporation).

The amount of the silane coupling agent added is preferably 0.1 to 10% by weight based on the solid content of the silicone resin.
When the content of the silane coupling agent is less than 0.1% by weight, the effect is not exerted, so that the adhesion between the core particles and the resistance control agent and the silicone coating layer decreases, and the coating is performed during long-term use. Layers fall out. In addition, the content is 10% by weight
If it exceeds, the spent resistance of the silicone resin is lowered, and the toner becomes spent during a long period of use.

In the present invention, when the coating layer is formed of a silicone resin containing a silane coupling agent, it is preferable to use an organotin compound as a catalyst for the reaction between the silicone resin and the silane coupling agent. The catalyst is effective in promoting the reaction between the hydrocarbon group hydrogen of the silicone resin and the silane coupling agent. The addition amount of the organotin compound is 1 to 100 times, preferably 2 to 50 times the addition amount of the silane coupling agent, and if the addition amount is too small, the addition effect is not exhibited, and if it is too large, the silicone resin original Since the performance is not exhibited, the spent resistance is lowered. Further, by changing the concentration of the organotin compound catalyst in the thickness direction of the coating layer as described above, it is possible to balance the chargeability adjustment by the catalyst and the chargeability reduction due to the progress of spent.
As a result, the chargeability of the coated carrier can be stably maintained for a long period of time, and the charge amount can be changed by changing the catalyst addition amount. Table 1 shows specific examples of the organotin compound described in detail above.

[0020]

[Table 1]

The core particles used in the present invention may be existing magnetic materials, such as iron, cobalt and other ferromagnetic metals; magnetite,
Iron oxide such as hematite and ferrite; various alloys and compounds; resin core particles in which fine powders of these magnetic materials are dispersed in a binder resin; Of these, the use of resin core particles is particularly preferable because the image quality is improved. The resin core particles are produced by the following method, but are not limited thereto. (1) The thermoplastic resin and the magnetic fine powder are melted and kneaded, and then pulverized and appropriately classified. If it is further treated with hot air, it can be made spherical. (2) After the thermosetting resin and the magnetic fine powder are melted and kneaded, a curing agent is added and the mixture is thermally cured, and the obtained cured product is pulverized and classified. (3) After the binder resin and the magnetic fine powder are melted and kneaded, the kneaded product is sprayed in a relatively low temperature air flow without being solidified to be cooled and solidified. (4) The thermosetting resin is dissolved in a solvent, the magnetic fine powder is dispersed, spray-granulated and dried, and then heat-cured and classified. (5) Phenols and aldehydes are reacted and hardened in an aqueous medium in the presence of a magnetic fine powder, a suspension stabilizer and a base catalyst. That is, it is manufactured by a reaction method.

As the toner constituting the developer together with the electrostatic latent image developing carrier of the present invention, those manufactured by a known method may be used. Specifically, a binder resin, a colorant,
A mixture consisting of a polarity control agent and any additives added as necessary is melted and kneaded in a hot roll mill and then cooled.
It is obtained by solidifying, crushing and classifying this. As the above-mentioned polarity controlling agent, known ones may be used, such as metal complex salts of monoazo dyes; nitrohumic acid and its salts; metal complexes of salicylic acid, naphthoic acid and various dicarboxylic acids with cobalt, chromium, iron and the like; amino compounds; Quaternary ammonium compounds and organic dyes are used. The amount of the polarity control agent used is not uniquely determined because it is determined by the type of the binder resin, the presence and amount of the additive, the toner manufacturing method including the dispersion method, etc. 0.
The range of 1 to 20 parts by weight is preferable. If the amount is less than 0.1 parts by weight, the toner charge amount is insufficient, which is not practical. If the amount is more than 20 parts by weight, the electrostatic charge force between the toner and the carrier increases because the toner charge amount is excessive. As a result, the fluidity of the developer is lowered and the image density is lowered.

As the binder resin, all known products can be used. For example, polystyrene, poly-p-chlorostyrene, styrene monomer such as polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-acrylic acid Methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer , Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer,
Styrene-based copolymers such as styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate; polybutyl methacrylate; polyvinyl chloride; polyvinyl acetate; polyethylene; polypropylene Polyester; Polyurethane; Polyamide; Epoxy resin; Polyvinyl butyral; Polyacrylic acid resin; Rosin; Modified rosin;
Terpene resin; Phenolic resin; Aliphatic hydrocarbon resin;
Aromatic petroleum resin; chlorinated paraffin; paraffin wax, etc. may be used alone or in combination. Then, when the polyester resin is used as a binder resin, a toner for a developer that does not have a vinyl matte fusion property and does not lose the original color of the color toner can be obtained.

The existing colorants may also be used. Black colorants include carbon black, aniline black, furnace black and lamp black, and cyan colorants include phthalocyanine blue, Victoria blue, methyl violet and aniline. Blue, ultramarine blue, etc. can be used. Further, magenta colorants include rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake, and the like, and yellow colorants include chrome yellow, benzidine yellow, hansa yellow,
Naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used. As additives to the toner, lubricants such as Teflon and zinc stearate, abrasives such as cerium oxide and silicon carbide, fluidity imparting agents such as colloidal silica and aluminum oxide, anti-caking agents, carbon black and tin oxide, etc. There are conductivity-imparting agents, fixing aids such as low molecular weight polyolefins, and the like. The amount of the carrier and toner of the present invention used is preferably such that the toner particles adhere to the surface of the carrier particles and occupy 30 to 90% of the surface area thereof.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. All the following parts are parts by weight.

[Toner Production Example 1] Styrene-acrylic resin (Haimer 70: Sanyo Chemical Co., Ltd.) 90 parts Carbon black (# 44: Mitsubishi Kasei Co., Ltd.) 8 parts Metal-containing azo dye (S-34: Orient Chemical Co., Ltd.) 2 parts) The mixture having the above formulation was kneaded with a hot roll at 120 ° C., cooled and solidified, and then the kneaded product was pulverized and classified by a jet mill to obtain a negatively chargeable toner a having an average particle diameter of 10 μm. [Toner Production Example 2] Styrene-acrylic resin (Haimer 70: Sanyo Kasei Co., Ltd.) 90 parts Carbon black (# 44: Mitsubishi Kasei Co., Ltd.) 8 parts Nigrosine dye (Nigrosine EX: Orient Chemical Co., Ltd.) 2 parts The above formulation The mixture was kneaded with a hot roll at 120 ° C., cooled and solidified, and then the kneaded product was pulverized and classified by a jet mill to obtain a positively chargeable toner b having an average particle size of 10 μm.

Example 1 Composition of coating layer forming liquid 1 Acrylic resin (BR-83: manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts Titanium oxide (ECT-52: manufactured by Titanium Industry Co., Ltd.) 8 parts Coating layer forming liquid 2 Composition Acrylic resin (BR-83: manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts Titanium oxide (ECT-52: manufactured by Titanium Industry Co., Ltd.) 12 parts Stirring and mixing of the above two kinds of coating layer forming liquid preparation mixtures with a homomixer Thus, coating layer forming liquids 1 and 2 were obtained.

Separately, 1,000 g of ferrite core particles having an average particle size of 100 μm was prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, coating layer forming liquid 2
Was supplied from tank B to tank A at a speed of 2.5 g / min, and 100 g of coating layer forming liquid 2 was supplied (time required: 40
Formation of the coating layer was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 1 having a coating layer with a film thickness of 1 μm. A coated carrier having a coating layer having a dry film thickness of 0.5 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Example 2 Composition of coating layer forming liquid 1 Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts Toluene 100 parts Titanium oxide (ECT-52: manufactured by Titanium Industry Co., Ltd.) 8 parts Silane cup Ring agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 part Organic tin compound (dibutyltin diacetate) 2 parts Composition of coating layer forming liquid 2 Silicone resin (SR-2411: Toray Dow Corning) -Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot Co.) 4 parts Silane coupling agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 parts Organotin compound (Dibutyltin diacetate) 2 parts The above two types of coating layers The liquid preparation for mixture stirred and mixed by a homo mixer to obtain a coating layer-forming solution 1 and 2.

Separately, 1,000 g of ferrite core particles having an average particle size of 100 μm were prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, coating layer forming liquid 2
Was supplied from tank B to tank A at a speed of 2.5 g / min, and 100 g of coating layer forming liquid 2 was supplied (time required: 40
Formation of the coating layer was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 2 having a coating layer having a thickness of 1.1 μm. A coated carrier having a coating layer having a dry film thickness of 0.6 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Example 3 Composition of coating layer forming liquid 1 Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot Corporation) 2 parts Silane coupling Agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 part Organic tin compound (dibutyltin diacetate) 2 parts Composition of coating layer forming liquid 2 Silicone resin (SR-2411: Toray Dow Corning. Silicone) 100 parts Toluene 100 parts Carbon black (BP-2000: made by Cabot) 4 parts Silane coupling agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 parts Organotin compound ( Dibutyltin diacetate) 2 parts The Kutsugaeso forming liquid preparative mixture was stirred and mixed by a homo mixer to obtain a coating layer-forming solution 1 and 2.

Separately, 1,000 g of ferrite core particles having an average particle size of 100 μm were prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, coating layer forming liquid 2
Was supplied from tank B to tank A at a speed of 2.5 g / min, and 100 g of coating layer forming liquid 2 was supplied (time required: 40
Formation of the coating layer was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 3 having a coating layer having a film thickness of 1.0 μm. A coated carrier having a coating layer having a dry film thickness of 0.5 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Example 4 Composition of coating layer forming liquid 1 Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot Co.) 2 parts Silane coupling Agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.1 part Organic tin compound (dibutyltin diacetate) 2 parts Composition of coating layer forming liquid 2 Silicone resin (SR-2411: Toray Dow Corning. Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: made by Cabot Co.) 4 parts Silane coupling agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.6 parts Organotin compound ( Dibutyltin diacetate) 2 parts The Kutsugaeso forming liquid preparative mixture was stirred and mixed by a homo mixer to obtain a coating layer-forming solution 1 and 2.

Separately, 1,000 g of ferrite core particles having an average particle size of 90 μm were prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, the coating layer forming liquid 2 was supplied from the tank B to the tank A at a speed of 2.5 g / min, and 100 g of the coating layer forming liquid 2 was supplied (time required: 40 minutes).
The coating layer formation was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 4 having a coating layer having a film thickness of 1.1 μm. A coated carrier having a coating layer having a dry film thickness of 0.6 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Example 5 Composition of coating layer forming liquid 1 Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot Co.) 2 parts Silane coupling Agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 part Organic tin compound (dibutyltin diacetate) 1 part Composition of coating layer forming liquid 2 Silicone resin (SR-2411: Toray Dow Corning Silicone) 100 parts Toluene 100 parts Carbon black (BP-2000: made by Cabot) 4 parts Silane coupling agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 parts Organotin compound ( Dibutyltin diacetate) 4 parts The Kutsugaeso forming liquid preparative mixture was stirred and mixed by a homo mixer to obtain a coating layer-forming solution 1 and 2.

Separately, 1,000 g of ferrite core particles having an average particle size of 100 μm was prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, coating layer forming liquid 2
Was supplied from tank B to tank A at a speed of 2.5 g / min, and 100 g of coating layer forming liquid 2 was supplied (time required: 40
Formation of the coating layer was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 5 having a coating layer having a thickness of 1.0 μm. A coated carrier having a coating layer having a dry film thickness of 0.5 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Example 6 Composition of coating layer forming liquid 1 Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot) 2 parts Silane coupling Agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.1 part Organic tin compound (dibutyltin diacetate) 3.5 parts Composition of coating layer forming liquid 2 Silicone resin (SR-2411: Toray Dowkoh) Ning Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: Cabot Co.) 4 parts Silane coupling agent [r- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.6 parts Organotin Compound (dibutyltin diacetate) 1.5 parts Above The type of coating layer forming solution preparation for mixture stirred and mixed by a homo mixer to obtain a coating layer-forming solution 1 and 2.

Separately, 1,000 g of ferrite core particles having an average particle size of 90 μm were prepared and a coated carrier was prepared using a fluidized bed type coating layer forming apparatus. That is, 100 g of the coating layer forming liquid 1 was put in the tank A and supplied to the above ferrite core particles at a speed of 5 g / min while stirring to start coating of the ferrite core particles. Immediately after the start, the coating layer forming liquid 2 was supplied from the tank B to the tank A at a speed of 2.5 g / min, and 100 g of the coating layer forming liquid 2 was supplied (time required: 40 minutes).
The coating layer formation was completed. After the formation of the coating layer, the ferrite core particles having the coating layer formed thereon were dried to obtain a coated carrier of Example 6 having a coating layer having a thickness of 1.0 μm. A coated carrier having a coating layer having a dry film thickness of 0.5 μm was sampled during the formation of the coating layer using the fluidized bed type coating layer forming apparatus.

Comparative Example 1 Composition of coating layer forming liquid Acrylic resin (BR-83: manufactured by Mitsubishi Rayon Co., Ltd.) 100 parts Toluene 100 parts Titanium oxide (ECT-52: manufactured by Titanium Industry Co., Ltd.) 15 parts A mixture of the above composition was homomixed. After preparing a coating layer forming liquid by mixing with 200 g of the ferrite core particles having an average particle diameter of 100 μm and stirring 200 g of the coating layer forming liquid with a fluidized bed type coating layer forming device. To form a coating layer, and the resulting fine particles were dried to obtain a coated carrier of Comparative Example 1 having a coating layer having a thickness of 1.0 μm. During the formation of the coating layer, a dry film thickness of 0.
A coated carrier having a coating layer of 5 μm was taken.

Comparative Example 2 Composition of coating layer forming liquid Silicone resin (SR-2411: manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts Toluene 100 parts Carbon black (BP-2000: manufactured by Cabot Co.) 3 parts Silane coupling agent [R- (2-aminoethyl) aminopropylmethyltrimethoxysilane] 0.2 part Organotin compound (dibutyltin diacetate) 2 parts The mixture having the above composition is mixed with a homomixer to prepare a coating layer forming liquid, which is then flowed. Using a floor type coating layer forming apparatus, 200 g of the coating layer forming liquid was supplied to 1,000 g of magnetite core particles having an average particle diameter of 90 μm at a speed of 5 g / min while stirring to form a coating layer. The fine particles thus obtained were dried to obtain a coated carrier of Comparative Example 2 having a coating layer having a film thickness of 1.1 μm. During the formation of the coating layer, a dry film thickness of 0.
A coated carrier having a coating layer of 5 μm was taken.

Table 2 shows the composition of the coating layer forming liquid used in Examples 1 to 6 and Comparative Examples 1 and 2. In addition, the coated carrier of the example is 100 g in 100 g of the coating layer forming liquid 1.
g of the coating layer forming liquid 2 is gradually added to change the composition of the forming liquid over time, and the total amount of 200 g of the coating layer forming liquid is coated on 1,000 g of the core particles. The coated carrier of the comparative example is formed by coating 200 g of a coating layer forming liquid having a constant composition on 1,000 g of core particles. In addition, Examples 1 to 1
6, a carrier having a coating layer with a predetermined film thickness shown in Comparative Examples 1 and 2, and 0.5 than the predetermined film thickness of each carrier.
Table 3 shows the specific resistance of the coated carrier having a thin coating layer of μm. The specific resistance was measured by filling a cell with an electrode area of 10 cm ² and a distance between electrodes of 2 mm with a carrier and applying a DC voltage of 1,000.
When V is applied (measured electric field; 1,000 V / 2 mm =
The value is 5,000 V / cm).

[0044]

[Table 2]

[0045]

[Table 3]

3 parts of the toner particles a were added to 97 parts of the carriers of Examples 1 to 5 and Comparative Examples 1 and 2, and the resulting mixture was ball milled to 30 parts.
A minute amount was mixed to prepare a developer. Further, toner particles b were added to the carriers of Example 6 and Comparative Example 2 to prepare a developer under the same conditions. A copying experiment was conducted using a copying machine FT-6960L manufactured by Ricoh Co., Ltd. as a developer using the toner particles a, and a copying machine FT-3350 as a developer using the toner particles b. In both machines, when the measured electric field is 5,000 V / cm and the specific resistance of the carrier is 1 × 10 ⁸ to 10 ⁹ Ωcm or less, the carrier development increases and the life of the developer ends.
Measured electric field of carrier is 5,000V / cm as actual life
Copying was repeated until the specific resistance at that time reached 5 × 10 ⁸ Ωcm, and the number of copies, image density, halftone reproducibility and film thickness up to that point were evaluated. The results are shown in Table 4. The specific resistance referred to here is the specific resistance in a state in which the coating layer of the carrier has deteriorated after being used for a long period of time.

[0047]

[Table 4]

In Table 4, the image densities were measured at 20 φ measuring points arranged at the upper, central and lower parts of the image, and the image densities at a total of 9 points were measured by a Macbeth reflection densitometer, and the average value thereof was obtained. It was obtained from. For the halftone reproducibility, a gray scale (No. Q-13) manufactured by Kodak Co. was copied, and the number of possible gradations was expressed as follows. ⊚; ≧ 13, ∘; 10 to 12, Δ: 6 to 2, ×;
≦ 5 Further, although the charge amount and the film thickness are described in duplicate in Table 4, the carrier in which the coating layer is partially formed is sampled in the manufacturing process of the coated carrier as described above, and This is because we evaluated two different types of carriers. The number of copies, the image density, and the halftone reproducibility show the data when the carrier with the thicker film thickness is used.

Comparing the coated carrier of the present invention with that of the comparative example, in the former case, even if a part of the coating layer falls off,
It can be seen from Table 3 that although the specific resistance value is about / 10 ² , the carrier of the comparative example has a specific resistance of 1/10 ⁵ or less. The rate of decrease in the specific resistance value due to partial removal of the coating layer depends on various factors such as the type of resin for forming the coating layer and the type of resistance adjusting agent, but the silicone resin, the silane coupling agent, and the carbon black. It can be said that the coating layer formed of the organic tin compound catalyst has many advantages, and is particularly effective when the surface concentration of the silane coupling agent is high (comparison between Examples 4 and 3). Further, it can be seen that the effect is exhibited even when the catalyst concentration is changed in the thickness direction (comparison between Examples 5 and 6 and 3). The carrier of Example 2 in which carbon black was mainly used as the resistance adjusting agent in the surface layer and the resistance adjusting agent mainly containing titanium oxide was used in the portion close to the core particles, the fluctuation range of the specific resistance value was It is noteworthy that particularly excellent results are shown in terms of the above points. However, considering the obtained image density and halftone reproducibility, the carriers of Examples 5 and 6 are particularly preferable. Silane coupling agent and /
Alternatively, it is a carrier having a concentration of the organotin compound catalyst.

[0050]

INDUSTRIAL APPLICABILITY The coated carrier of the present invention in which the resistance of the coating layer is as low as that on the surface of the coating layer, particularly the developer using the coated carrier using carbon black as the resistance adjusting agent, can be used for a long period of time. Since the carrier resistance is stable, high-quality images can be continuously obtained for a long period of time. Also, silicone resin is used for the coating layer forming resin,
In the coating layer in which a silane coupling agent and an organotin compound catalyst are coexistent and a concentration odor is added to these additives, the charging characteristics of the carrier (for example,
The amount of triboelectrification of the toner) can be prevented from changing, and a stable high-quality image can be obtained for a long period of time without degrading the developing characteristics.

[Brief description of drawings]

FIG. 1 schematically shows the specific resistances of the coating layers of the carrier of the present invention and a conventional coated carrier.

FIG. 2 schematically shows the specific resistance of the carrier of the present invention and the conventional coated carrier.

Claims (5)

[Claims] 1. A coated carrier having a coating layer comprising at least a resin and a resistance modifier on the surface, wherein the specific resistance of the coating layer is lower than that of the surface of the coating layer. Coated carrier for developing an electrostatic latent image. 2. The specific resistance of a coated carrier having a coating layer of a predetermined thickness when the measured electric field is 5,000 V / cm,
The coated carrier for developing an electrostatic latent image according to claim 1, which has a specific resistance of 1 to 10 ⁴ times the specific resistance of a coated carrier having a coating layer thinner than a predetermined film thickness by 0.5 μm. 3. The coated carrier for developing an electrostatic latent image according to claim 1, wherein the resistance adjusting agent of the coating layer is carbon black. 4. The coating layer resin is formed of a silicone resin containing a silane coupling agent, and the concentration of the silane coupling agent in the coating layer is higher on the surface of the coating layer. A coated carrier for developing an electrostatic latent image of. 5. The coating layer resin is formed of a silicone resin containing a silane coupling agent with an organotin compound as a catalyst, and the concentration of the catalyst has a concentration gradient in the thickness direction of the coating layer. The coated carrier for developing an electrostatic latent image according to claim 3.