JPH05303238A - Carrier for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To ensure excellent heat resistance, environmental resistance and electrostatic charge stability, to prevent toner fog and to enable the formation of a fine-grained image by forming coating layers of a thermosetting resin on the surfaces of the core particles of a carrier and incorporating an electric conductive filler into the outermost parts of the coating layers. CONSTITUTION:The core material of a carrier is coated with a coating layer of a thermosetting resin and a surface-treated electric conductive filler is incorporated into the outermost part of the coating layer. A resin which cures by heating, e.g. silicone resin or epoxy resin may be used as the thermosetting resin and the core particles of the carrier are preferably coated with 0.5-10wt.% of the thermosetting resin basing on the amt. of the core particles. Magnetic powder may be used as the electric conductive filler. The thermosetting resin contributes toward improving the heat resistance and durability of the carrier and the electric conductive filler contributes toward improving the environmental stability of the carrier, especially the electrostatic charge stability at high temp. and humidity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin-coated carrier used as a developer in combination with a toner.

[0002]

2. Description of the Related Art Conventionally, as an electrostatic latent image developing method for electrophotography, by mixing an insulating non-magnetic toner and carrier particles, the toner is triboelectrically charged, and a developer is conveyed to cause electrostatic latent image development. A two-component developing method is known in which the image is contacted with an image and developed.

The granular carrier used in such a two-component developing system prevents the filming of the toner on the surface of the carrier, the formation of a uniform carrier surface, the prevention of surface oxidation, the prevention of deterioration of moisture sensitivity and the life of the developer. For the purpose of extension, protection from scratches or abrasion by the carrier of the photoconductor, control of charge polarity or adjustment of charge amount, etc., it is usually coated with a suitable resin material (for example, JP-A-58-108548).

It is known that a thermosetting resin is used as one of such resin materials, but it still has a problem in durability or heat resistance, and the toner is spent on the carrier surface, and As a result, there is a problem that the charge amount becomes unstable and toner fogging occurs. Furthermore, it is necessary to improve the environmental resistance. Particularly in a high temperature and high humidity environment, a good image can be obtained at the initial stage, but as printing is performed, the charge amount decreases, toner fog and carrier stripes occur, and the image quality of the copied image deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and is capable of forming a textured image which is excellent in heat resistance, environment resistance and charge stability and is free from toner fog. The purpose is to provide a surface-treated carrier.

[0006]

SUMMARY OF THE INVENTION The present invention is characterized in that a carrier core particle surface has a coating layer of a thermosetting resin, and an outermost shell coating layer portion contains a conductive filler. For carriers.

The carrier of the present invention comprises at least a carrier core material, a thermosetting resin coating layer for coating the core material, and a surface-treated conductive material contained in the outermost shell of the thermosetting resin coating layer. Made of filler.

The coating of the thermosetting resin contributes to the improvement of heat resistance and durability of the carrier, and the addition of the conductive filler greatly contributes to the environmental stability of the carrier, especially the charging stability under high temperature and high humidity. .. As a result, the carrier of the present invention can form an image excellent in texture without toner fog or the like.

The core material of the carrier is at least 20 μ from the viewpoint of preventing carrier adhesion (scattering) to the electrostatic latent image carrier.
Use a size of m (average particle size), and at the most 100 points from the viewpoint of preventing deterioration of image quality such as occurrence of carrier stripes etc.
Use the μm one. Specific materials include those known as two-component carriers for electrophotography, for example, metals such as ferrite, magnetite, iron, nickel and cobalt,
These metals and zinc, antimony, aluminum, lead,
Alloys and mixtures with metals such as tin, bismuth, beryllium, manganese, selenium, tungsten, zirconium and vanadium, metal oxides such as iron oxide, titanium oxide and magnesium oxide, nitrides such as chromium nitride and vanadium nitride, silicon carbide , Mixtures with carbides such as tungsten carbide and ferromagnetic ferrites, and mixtures thereof can be applied.

As the thermosetting resin with which the carrier core material is coated, what is known as a resin which is cured (insolubilized) when heated can be applied. For example, a silicone resin, an epoxy resin, an alkyd resin, a phenol-formaldehyde resin, a urea-formaldehyde resin, a melamine-formaldehyde resin, a resin obtained by curing an acrylic polyol with an isocyanate, a resin obtained by curing a polyester polyol with an isocyanate, or an acrylic polyol having a melamine. And a resin obtained by curing acrylic acid with melamine. Moreover, you may use combining the monomer which is a structural component of thermosetting resin. In addition, any thermoplastic resin that is cured by crosslinking and has heat resistance is included in the thermosetting resin of the present invention. In particular, when the constituent resin of the toner used in combination with the carrier is composed of a polyester-based resin, the toner is negatively charged, and in order to make the carrier more positively charged,
It is preferable to use a thermosetting acrylic resin. The thermosetting acrylic resin is obtained by crosslinking at least one acrylic monomer or a copolymer obtained by polymerizing an acrylic monomer and a styrene monomer with a melamine compound or an isocyanate compound. Is. Examples of acrylic monomers include alkyl methacrylates such as methyl methacrylate, butyl methacrylate, octyl methacrylate, and stearyl methacrylate; ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, etc. Acrylic acid alkyl esters; acrylonitrile, acrylamide; or amino group-containing vinyl monomers such as methacrylic acid dimethylaminoethyl ester, methacrylic acid diethylaminoethyl ester, acrylic acid dimethylaminoethyl ester, dimethylaminopropylmethacrylic acid amide, etc. In addition, styrene, α-methylstyrene, vinyltoluene, p-ethylstyrene and the like can be used as the styrene-based monomer.

In the present invention, the thermosetting resin as described above is used in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, more preferably 2 to 3% by weight, based on the carrier core particles. Cover the carrier. If it is less than 0.5% by weight, the core material cannot be uniformly coated and the environmental resistance is deteriorated. If it is more than 10% by weight, the particle size becomes too large and the image quality deteriorates. This is because it occurs.

The outermost shell layer of the carrier-covered thermosetting resin layer contains a surface-treated conductive filler. When the conductive filler is contained in the entire carrier coating layer, the resistance of the carrier becomes low and the carrier is likely to adhere to the photoreceptor. By containing a conductive filler in the outermost shell layer, the problem of carrier charge accumulation can be solved without lowering the resistance of the carrier itself. The conductive filler has an electric resistance (specific resistance) of 1
It is possible to use a filler having a density of 0 ¹⁰ Ω · cm or less, such as magnetic powder (ferrite, magnetite), Ni.
O, CrO ₂ , MnO ₂ , conductive ZnO, conductive carbon black and the like can be used. In particular, it is desirable to use ferrite as a conductive filler in a carrier for negatively chargeable toner in terms of its chargeability.

The conductive filler is surface-treated. The filler-containing carrier is in a state where the filler on the carrier surface is easily released or detached due to mechanical stress during crushing of the coating resin after the thermosetting treatment. By subjecting the conductive filler to the surface treatment in advance according to the present invention, the hydrophobic property or the binding property with the coating resin is improved, so that the filler is fixed without being detached from the carrier surface.
In this way, by reducing the release of filler,
Less damage to the photoconductor and longer life. In particular, with a full-color image, an image without color turbidity can be obtained without impairing the color tone of the toner. Further, in the resin solution at the time of resin coating, since the aggregation of the fillers is prevented,
Alternatively, since the compatibility of the filler with the binder resin and the solvent is improved, the dispersibility is improved, and the filler can be uniformly present on the carrier surface. In this way, since the filler is evenly distributed on the carrier surface, water resistance,
It becomes excellent in environmental resistance, the toner is developed uniformly, and an image with good texture can be obtained.

There are two types of surface treatments, liquid treatment and fine powder treatment. Below, the method of surface-treating by liquid treatment is demonstrated first. The liquid treatment is a treatment of the surface of the conductive filler with a coupling agent, silicone oil or an organic acid.

As the coupling agent, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, a zirco aluminum coupling agent or the like can be used alone or in combination of two or more kinds.

As the silane coupling agent, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, vinyltris (methoxyethoxy) silane, γ-chloropropyltrimethoxysilane, (3,3,3,3). 3-trifluoropropyl) methyldimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane and the like can be mentioned.

Titanium coupling agents include tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, tetraoctylbis (ditridecylphosphite) titanate, isopropyl triisostearoyl titanate, isopropyl. Examples thereof include tridecylbenzenesulfonyl titanate, isopropyl trioctainor titanate, dicumylphenyloxyacetate titanate and the like.

Examples of the aluminum coupling agent include acetoalkoxy aluminum diisopropylate.

Examples of zirco aluminum coupling agents include Cabcomod M, Cabcomod MPG, and Cabcomod MPM manufactured by Cabdon Chemical Company.

As the silicone oil, commercially available products known as silicone can be used. Examples of such materials include L-45 and L-90 manufactured by Nippon Unicar Co., Ltd.
00, L-31, Ocarsil EPS, L-305 or L-
404, L494, or SH2 from Torre Silicone
00, SH556, SH1107, SH3476, SH
3747, SH3748, SH3749 or SH3
771 etc. can be used.

The organic acid may be an aliphatic carboxylic acid having a melting point of 40 ° C. or higher, and examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and the like. Etc. can be used, and stearic acid and palmitic acid are particularly preferable. An aliphatic carboxylic acid having a melting point of lower than 40 ° C. is not preferable because of its meltability, the storage stability of the carrier is poor, and the occurrence of filming on the photoreceptor.

As the surface treatment method of the conductive filler,
The conductive filler can be dispersed in a solution in which the above-mentioned surface treatment agent is dissolved, and the mixture is stirred and mixed at a constant temperature for a predetermined time, and then the filler is separated and removed by a means such as filtration and dried (solution immersion method). As another method, a method in which a solution in which a surface treatment agent is dissolved is sprayed on a conductive filler and dried (spray drying method) can be mentioned.

The solvent used for the above surface treatment is
There is no particular limitation as long as it is inert to the surface treatment agent such as cyclohexane, methyl alcohol, ethyl alcohol, water, toluene, isopropyl alcohol, acetone, benzene, etc. and can be easily removed by drying.

The mixing ratio of the surface treatment agent and the conductive filler in the surface treatment varies depending on the kind of the surface treatment agent to be used, but generally the amount of the coupling agent added to the conductive filler is 0.01 to 30% by weight, preferably 0. .05-2
It is 0% by weight, more preferably 0.1 to 10% by weight.
If the addition amount is less than 0.01% by weight, the effect of the surface treatment according to the present invention cannot be obtained, and if the addition amount is more than 30% by weight, the dispersibility in the coating resin is rather deteriorated and toner scattering becomes a problem.

The surface treating agent is 10 to 80 ° C., preferably 10 to 70 ° C., and more preferably 20 to 60 ° C., although it varies depending on the organic solvent and the surface treating agent used. 8
If the temperature is higher than 0 ° C, the organic solvent will be evaporated and the surface treatment cannot be performed. If the temperature is lower than 10 ° C, the surface treatment cannot be sufficiently performed.

The surface treatment time is 0.01 to 12 hours, preferably 0.1 to 10 hours, more preferably 0.
5 to 5 hours. If it is shorter than 0.01 hours, the surface treatment cannot be sufficiently performed. If it is longer than 12 hours, the organic solvent is evaporated and the surface treatment cannot be performed.

In the spray drying method, the same kind of solution used in the solution dipping method can be used, but within a range of the amount of the surface treatment agent used, a concentration as low as about half the concentration used in the solution dipping method is used. The conditions similar to those of the solution immersion method can be applied except that the solution can be used.

Next, the surface treatment by the fine powder treatment will be described. This treatment is carried out by coating the conductive filler with an inorganic fine powder.

Examples of such inorganic fine powder include silica, aluminum silicate, calcium silicate, barium sulfate, zirconium sulfate, aluminum phosphate, zinc oxide, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, calcium carbonate, calcium oxide. , Tungstic acid, cobalt carbonate, zirconium hydroxide, cobalt carbonate, magnesium hydroxide, magnesium carbonate, magnesium fluoride, or a mixture thereof. They are preferably hydrophobized. As for the size, the particle size is 0.01 to 0.5 μm, preferably 0.01 to 0.1 μm. If the particle size is smaller than 0.01 μm, the cohesive force between the fine particles is strong and the conductive filler is nonuniformly surface-treated, so that the effect of the present invention cannot be sufficiently achieved. Also 0.5 μm
If it is larger, the inorganic fine powder is less likely to adhere to the conductive filler, resulting in a non-uniform surface treatment state. Therefore,
The effect of the present invention cannot be sufficiently achieved.

The amount of the inorganic fine powder used is 0.1 to 10% by weight, preferably 0.2 to 5% by weight, based on the conductive filler. If the amount is less than 0.1% by weight, the effect of surface treatment is not obtained. If it exceeds 10% by weight, the amount of addition will be more than that for coating the inorganic fine powder, free powder will be generated, the spent on the photoconductor will be easily generated, and the binding property with the coating resin will be deteriorated.

As a treatment method, a method of simply dry blending a conductive filler and an inorganic fine powder and adhering it to the surface, a method of mechanically driving the surface, and a conductive filler dispersed in a medium such as water are used. A method of adhering the inorganic fine powder to the surface and drying and firing may be applied.

The content of the conductive filler surface-treated as described above should be appropriately selected depending on the kind of the filler, but when ferrite is used, it is 0.01 to 10% by weight based on the carrier core particles. %, Preferably 0.
An amount of 05 to 5% by weight, more preferably 0.1 to 2% by weight may be used. This is because if the content is less than the above range, the effect of the present invention cannot be sufficiently achieved, and if it is more than the above range, the charge amount decreases and toner fog occurs.

To apply the thermosetting resin to the carrier core particles, a resin solution obtained by dissolving the above-mentioned thermosetting resin in a suitable solvent may be used, and a dipping method, a spray drying method or the like may be applied. When using a monomer alone or a mixture of monomers as the thermosetting resin, in order to secure the amount of adhesion to the surface of the core particles, it is necessary to cure the monomer mixture solution to some extent to give viscosity. preferable.

After coating, it is dried and baked if necessary. After the firing, the carrier particles are agglomerated into a bulk, and the bulk is crushed and sieved to obtain a carrier having a desired particle size.

In order to obtain a desired thickness and uniformity of the resin film, the above coating, firing and crushing may be repeated as necessary. It is preferably performed 2 to 3 times. By doing so, the carrier core particles are uniformly coated with the thermosetting resin.

Then, in the final application step, the resin liquid is applied by incorporating the above-mentioned conductive filler. The filler-containing coating layer can be formed with good adhesion on the thermosetting resin coating layer formed in the previous step.

To apply a thermosetting resin containing a conductive filler to the above resin-coated carrier, a predetermined amount of the conductive filler is added to a resin solution prepared by dissolving the above-mentioned thermosetting resin in an appropriate solvent and thoroughly An immersion method, a spray drying method, or the like may be applied using the dispersed resin solution. The conductive filler surface-treated according to the present invention has good dispersibility in a resin solution. Dispersion of the conductive filler in the resin liquid can be more effectively performed by using an ultrasonic homogenizer.
As a result, a uniform dispersion liquid can be obtained in a short time without inclusion of impurities.

After coating, firing and crushing are performed to obtain a carrier having a desired particle size. In the finally obtained carrier of the present invention, the thermal decomposition peak temperature of the coating layer is preferably 275 ° C or higher. When the thermal decomposition peak temperature is lower than 275 ° C, the heat resistance of the carrier is lowered and blocking is likely to occur.
The carrier of the present invention is used as a two-component developer in combination with toner. Hereinafter, the present invention will be described using examples.

Preparation Example of Ferrite Fine Powder 5 g of a silane coupling agent SZ6070 (manufactured by Toray Silicon Co.) is mixed in 250 ml of ethyl alcohol, and T
A K homogenizer (manufactured by Tokushu Koki Co., Ltd.) was stirred for about 10 minutes to uniformly disperse the mixture. 100 g of ferrite fine powder (MFP-2; manufactured by TDK) was added to the obtained dispersion, and the mixture was slowly stirred for 1 hour. After that, it was filtered with a vacuum filter, dried with hot air at 50 to 60 ° C. for 3 hours, and vacuum dried at 50 to 60 ° C. for 5 hours, and then 20 with a TK homogenizer.
The ferrite fine powder according to the present invention was obtained by dispersing at 00 rpm for 5 minutes.

Preparation Example of Ferrite Fine Powder 2 g of titanium coupling agent KR-2S (manufactured by Ajinomoto Co.) was mixed with 300 ml of n-hexane and stirred uniformly for about 10 minutes with a TK homogenizer (manufactured by Tokushu Kiki Co., Ltd.). Dispersed. Fine ferrite powder (MFP-
2; made by TDK) 100 g and slowly stirred for 1 hour. Then, dry with hot air at 50-60 ° C for 3 hours,
After vacuum drying at 50-60 ° C. for 4 hours, it was dispersed by a homogenizer at 2000 rpm for 5 minutes to obtain a ferrite fine powder according to the present invention.

Preparation Example of Ferrite Fine Powder Silicone oil SH556 in 200 ml of toluene
3 g (manufactured by Toray Silicone Co., Ltd.) was mixed and stirred for about 10 minutes with a TK homogenizer (manufactured by Tokushu Koki Co., Ltd.) to uniformly disperse. Fine ferrite powder (MF
P-2; manufactured by TDK), 100 g, and slowly 1
Stir for 5 minutes. Then, it is filtered with a vacuum filter,
After drying with hot air for 3 hours and vacuum drying at 50-60 ° C. for 5 hours, the resultant was dispersed with a TK homogenizer at 2000 rpm for 5 minutes to obtain a fine ferrite powder according to the present invention.

Preparation Example of Ferrite Fine Powder 3 g of stearic acid (first-grade reagent; manufactured by Kanto Chemical Co., Inc.) was mixed in 200 ml of hot ethyl alcohol, and the mixture was uniformly stirred by a TK homogenizer (manufactured by Tokushu Kiki Co., Ltd.) for about 10 minutes. Dispersed. Fine ferrite powder (MFP-
2; made by TDK) 100 g and slowly stirred for 15 minutes. Then, filter with a vacuum filter, and
After drying with hot air for 5 hours and vacuum drying at 50 ° C for 5 hours, TK
Disperse with a homogenizer at 2000 rpm for 5 minutes,
A fine ferrite powder according to the present invention was obtained.

Example of production of fine ferrite powder 100 g of fine ferrite powder (MFP-2; manufactured by TDK)
Hydrophobic silica (R972; manufactured by Nippon Aerosil Co., Ltd.) 0.
5 g was mixed with a Waring blender (manufactured by Waring Blender) at 5000 rpm for 1 minute to obtain a fine ferrite powder having hydrophobic silica adhered to the surface.

Production Example of Ferrite Fine Powder In the production example of ferrite fine powder, hydrophobic silica (R81
2; manufactured by Nippon Aerosil Co., Ltd.), except that 3 g was used to obtain a fine ferrite powder.

Production Example of Ferrite Fine Powder To 100 g of ferrite fine powder (MFP-2), 1 g of hydrophobic titanium oxide (manufactured by Nippon Aerosil Co .; P-25) was added to Mechano Fusion System (manufactured by Hosokawa Micron Corporation) 1000.
After processing for 10 minutes at rpm, fine ferrite powder was obtained.

[0046] Production Example of Preparation ferrite fine powder of the fine ferrite fine, hydrophobic aluminum oxide; was replaced by (RX-C produced by Nippon Aerosil Co., Ltd.) 2 g is performed in the same manner to obtain a ferrite powder.

Example 1 80 parts by weight of a styrene-acrylic copolymer (1.5: 7: 1.0: 0.5) consisting of styrene, methyl methacrylate, 2-hydroxyethyl acrylate and methacrylic acid and butylated melamine. 20 parts by weight of the resin was diluted with toluene to prepare a styrene acrylic resin solution having a solid ratio of 2% by weight.

Fired ferrite powder (F-300;
Average particle size: 50 μm, bulk density: 2.53 g / cm ³ ; manufactured by Powder Tech Co., Ltd., and the styrene acrylic resin solution is used in a spiral coater (Okada Seiko Co., Ltd.) so that the coating resin amount to the core material is about 1% by weight. (Manufactured by the company) and dried. The obtained carrier was baked by leaving it at 170 ° C. for 2 hours in a hot air circulation type open. After cooling, the ferrite powder bulk was crushed using a sieve shaker equipped with screen meshes of 210 μm and 90 μm to obtain resin-coated ferrite powder. The ferrite powder was subjected to the above-mentioned coating firing and crushing three more times to obtain a resin-coated carrier.

Then, 30% by weight of ferrite fine powder added to the resin solid content of the styrene acrylic resin solution was sufficiently dispersed with an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd.) to obtain ferrite filler-dispersed styrene. An acrylic resin solution was prepared.

Using the above resin-coated carrier as a core material,
The ferrite filler-dispersed styrene-acrylic resin solution was applied by the same spira coater (made by Okada Seiko Co., Ltd.) so that the coating resin amount with respect to the core material was about 1% by weight, dried, and further heated at 170 ° C. in a hot air circulation oven. It was left to burn for 2 hours. Next, after cooling, 210 μm to 90 μm
Using a sieve shaker equipped with the screen mesh of No. 1, was crushed to obtain a resin carrier containing a ferrite filler.

The average particle size of the obtained carrier is 55 μm.
m, resin coverage (Rc) 3.83%, thermal decomposition temperature 280
℃, electrical resistance was 4 × 10 ¹⁰ Ωcm ・

The coating resin amount (Rc) was determined as follows. Resin coated carrier about 5g, weight W _{0 in} advance
(g) is placed in a precisely weighed 10 cc magnetic crucible, and the total weight W ₁ (g) is precisely weighed. The crucible is placed in a muffle furnace, heated to 900 ° C. at a speed of 15 ° C./min, left at 900 ° C. for 3 hours to burn the coating resin, and then allowed to cool to room temperature. Immediately after reaching the room temperature, the weight W ₂ (g) of the crucible containing the carrier is precisely weighed. Amount of coating resin
(Rc) is calculated by the following formula.

[Equation 1]

The carrier particle size was measured by using a laser diffraction type particle size distribution analyzer manufactured by Microtrac.

The carrier bulk density was measured in accordance with JISZ 2504 using a bulk specific gravity measuring instrument manufactured by Kurachi Scientific Instruments Co., Ltd.

The thermal decomposition peak temperature was determined from the DSC curve by a thermal analyzer (Seiko Denshi Co., SSS-5000).

Example 2 The same procedure as in Example 1 was carried out except that 100% by weight of ferrite fine powder was used with respect to the resin solid content of the styrene-acrylic resin solution, and a ferrite-filler-containing resin-coated carrier was prepared. Obtained. The obtained carrier has an average particle size of 56 μm, a resin coating amount Rc of 3.80% by weight, a thermal decomposition temperature of 280 ° C., and an electric resistance of 3 × 10 ¹⁰ Ω.
It was cm.

Example 3 Example 1 was repeated except that the fine ferrite powder was 50% by weight based on the resin solid content of the styrene-acrylic resin solution and the coating resin amount was about 0.5% by weight based on the carrier core particles. The same operation as in Example 1 was performed to obtain a ferrite filler-containing resin-coated carrier. The obtained carrier had an average particle diameter of 53 μm, a resin coating amount Rc of 3.45% by weight, a thermal decomposition temperature of 283 ° C., and an electric resistance of 2 × 10 ¹⁰ Ω · cm.

Example 4 A ferrite-filler-containing resin-coated carrier was prepared in the same manner as in Example 1 except that the fine ferrite powder was 50% by weight with respect to the resin solid content of the styrene-acrylic resin solution. Obtained. The obtained carrier has an average particle diameter of 56 μm, a resin coating amount Rc of 3.80% by weight, a thermal decomposition temperature of 280 ° C., and an electric resistance of 4 × 10 ¹⁰ Ω.
It was cm.

Comparative Example 1 The same fired ferrite powder (F-30 as in Example 1) was used as the core material.
0; average particle size: 45 μm, bulk density: 2.50 g / cm ³ : manufactured by Powdertec Co., Ltd., and the same ferrite filler-dispersed styrene acrylic resin solution as in Example 1 was used, and the coating resin amount for the core material was about 2% by weight. Spiral coater to be%
(Made by Okada Seiko Co., Ltd.) and dried. The obtained carrier was left in a hot air circulation oven at 160 ° C. for 2 hours for firing. After cooling, open the bulk of ferrite powder 21
It was crushed by using a sieve shaker equipped with 0 μm and 90 μm screen mesh to obtain a ferrite filler-containing resin-coated carrier. The obtained carrier had an average particle size of 47 μm, a coating resin amount (Rc) of 1.90%, a thermal decomposition peak temperature of 245 ° C., and an electric resistance of about 5 × 10 ⁹ Ωcm. The manufacturing conditions and various physical properties of the carrier obtained above are summarized in Table 1.

[0060]

[Table 1]

Example 5 A resin-coated carrier containing a ferrite filler was obtained in the same manner as in Example 1 except that the ferrite fine powder was added in place of the ferrite fine powder.

Example 6 A resin-coated carrier containing a ferrite filler was obtained in the same manner as in Example 2 except that the ferrite fine powder was added in place of the ferrite fine powder.

Example 7 A ferrite-filler-containing resin-coated carrier was obtained in the same manner as in Example 3 except that ferrite fine powder was added instead of the ferrite fine powder in Example 3.

Example 8 A resin-coated carrier containing a ferrite filler was obtained in the same manner as in Example 4 except that the ferrite fine powder was added in place of the ferrite fine powder. The manufacturing conditions and various physical properties of the carriers obtained in Examples 5 to 8 are summarized in Table 2 above.

[0065]

[Table 2]

Production of toner ( production of binder resin: vinyl-modified polyester resin) Polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane 68 parts by weight, isophthalic acid 16 parts by weight, terephthalic acid 16 parts by weight Parts, 0.3 parts by weight of maleic anhydride, and 0.06 parts by weight of dibutyltin oxide were charged in a flask, and the reaction was continuously taken out at 230 ° C. for 24 hours under a nitrogen atmosphere to obtain a polyester resin containing an unsaturated polyester. .. The weight average molecular weight of the obtained polyester resin was 10,600.

50 parts by weight of this polyester resin and 50 parts by weight of xylene were charged into a flask and dissolved. Raise the temperature until xylene is refluxed, and add styrene 1 under xylene reflux.
A solution prepared by dissolving 0.4 parts by weight of azobisisobutyronitrile in 3 parts by weight and 2 parts by weight of methyl methacrylate was added dropwise under a nitrogen atmosphere in about 30 minutes. After dropping, the mixture was kept warm for 3 hours, and xylene was distilled under reduced pressure, and then the resin was taken out to obtain a binder resin having a weight average molecular weight of 13,100, a melt viscosity at 100 ° C. of 6 × 10 ⁴ poise and a glass transition temperature of 63 ° C.

However, the melt viscosity is a value measured by using a Shimadzu Flow Tester CFT-500 under the conditions of a nozzle diameter of 1 mm, a nozzle length of 1 mm, a load of 3 kg and a heating rate of 3 ° C./min.

Parts by weight: styrene acrylic modified polyester resin obtained above 100: carbon black MA # 8 (manufactured by Mitsubishi Kasei) 3 charge control agent (Bontron E-84, manufactured by Orient Chemical Co.) 3 The mixture was thoroughly mixed with a mixer, kneaded with a twin-screw extruder, and then cooled. The mixture was coarsely pulverized with a feather mill, and then a jet pulverizer and an air classifier were used to obtain particles having a particle size of 5 to 25 μm (average particle size 10.5 μm).

Next, hydrophobic titanium (manufactured by Nippon Aerosil Co., Ltd .:
1.0 wt% of T-805 and 0.2 wt% of hydrophobic silica (H2000 / 4 manufactured by Wacker Co.) were added and mixed with a Henschel mixer to obtain a toner.

[Evaluation of Carrier] Toner 8 produced above
Parts by weight and each carrier 9 of Examples 1 to 8 and Comparative Example 1
A developer was prepared by mixing 2 parts by weight. CF-
70 (made by Minolta Camera Co., Ltd.)
5000 copies were made in an environment of 0 ° C. and 85%, printing durability was evaluated, and the results are shown in Tables 3 and 4.

[0072]

[Table 3]

[0073]

[Table 4]

The evaluation of each item in the above table was carried out as follows. (Charge amount) According to a film charge measuring method (toner concentration 8% by weight)

(Fog on Image) As described above, images were printed using the above copying machine in the combination of various toners and carriers. Regarding the fog on the image, the toner fog on the white background image was evaluated and ranked. △
It is practically usable with a rank or higher, but ◯ or higher is desirable.

(Heat resistance) 10 g of carrier was put in a container and
After being left in an oven at 0 ° C. for 1 hour, the presence or absence of carrier aggregation after cooling was determined and ranked as follows. ○: No aggregation △: Aggregation, but easy loosening (lower limit of practical use) ×: Large aggregation and not loosening (impractical use)

(Environmental fluctuation of charging) Developer at 10 ° C., 15%
The amount of charge (Q _LL ) after storage for 24 hours in
The amount of charge (Q _HH ) after storage for 24 hours in an environment of 85 ° C and 85% is calculated, and the difference ΔQ; ΔQ = Q _LL -Q _HH (μC / g) is calculated and ranked as follows. By doing so, the environmental change in charging was evaluated. The following results are summarized in Table 1 below. X indicates that there are large environmental fluctuations and it is not practical,
A value of Δ or more indicates practical use, but a value of O or more indicates desirable.

(Texture on the image) Regarding the texture on the image,
The texture on the half image was evaluated and ranked. △
It is practically usable with a rank or higher, but ◯ or higher is desirable.

(Spent Amount) The spent toner amount is determined by sampling the developer, separating the developer into a toner and a carrier by a blow-off method, immersing about 1.00 g of the isolated carrier in 20 ml of ethanol for 2 hours, and then filtering. The absorbance of the filtrate at 500 nm is measured with a spectrophotometer.
Separately from this, a calibration curve is obtained for the dye component in the toner, and the amount of the dye in the toner eluted from the previous absorbance at 500 nm is calculated. From this value and the ratio of the dye contained in the toner, the amount of spent toner (mg / carrier 1 g) is obtained as the amount of toner fixed to the carrier.

(Toner Scattering Amount) It was determined by the amount of toner drop when the film charge amount was measured.

[0081]

INDUSTRIAL APPLICABILITY The carrier of the present invention is excellent in heat resistance and durability, has little environmental change, and is free from toner fog even under high temperature and high humidity, and can form an excellent copy image with fine texture.

Claims (1)

[Claims] 1. A carrier for developing an electrostatic charge image, comprising a coating layer of a thermosetting resin on the surface of carrier core particles, and a surface-treated conductive filler contained in the outermost shell coating layer portion. ..