JP2003131436A - Carrier for developing electrostatic latent image and electrostatic latent image developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carrier for developing an electrostatic latent image having excellent stable charge applying property to toner and electrostatic latent image developer having the carrier. SOLUTION: The carrier for developing the electrostatic latent image is obtained by forming a coating layer on the surface of a porous carrier core having at least a surface hole. The coating layer has a 1st coating layer coated so that at least part of the surface hole of the porous carrier core may be filled therewith and at least part of the surface of the porous carrier core may be exposed, and a 2nd coating layer coating the exposed part of the porous carrier core and the 1st coating layer. Furthermore, the charge applying property of the 1st coating layer is set to be higher than that of the 2nd coating layer, and the 1st coating layer is coated so that the surface exposing rate of the porous carrier core may be within 2 to 7%. Furthermore, the electrostatic latent image developer includes at least the carrier and toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image carrier used for developing an electrostatic latent image in electrophotography and electrostatic recording, and an electrostatic latent image developer containing the carrier. Regarding

[0002]

2. Description of the Related Art Conventionally, a method of developing an electrostatic latent image has been generally used. At the time of this development, carrier particles called carriers are mixed with toner particles and both are triboelectrically charged with each other to impart an appropriate amount of positive or negative electric charge to the toner. Such a two-component developer is generally required to have long life, that is, stability and maintainability of image quality in continuous development. In order to achieve the above-mentioned long-life property, it is necessary to maintain the charge amount and the developer resistance in an appropriate range between both particles of the toner and the carrier. It is desirable that it does not change even after development processing.

In order to maintain the above-mentioned charge amount and developer resistance, it is necessary to control the abrasion charge characteristics and / or conductivity of the carrier.

Therefore, for example, Japanese Patent Laid-Open No. 11-29593.
JP-A No. 3 and JP-A No. 11-295935 disclose that a polymer or a polymer mixture (1) is contained in at least a part of a surface of a porous carrier core or pores, and is further coated with the polymer or the polymer mixture (2). A carrier characterized by is proposed. This carrier comprises a polymer or polymer mixture contained in the pores (1)
It is described that various combinations of the above with various polymers or polymer mixtures (2) used for coating can prepare carriers with different combinations of triboelectric properties and / or conductivity.

However, even the above-mentioned carrier is still insufficient in the level of control of the triboelectrification characteristics and / or conductivity which have been recently demanded.

For example, the carrier described in JP-A No. 11-295933 has a carrier core total surface area of about 30 to
About 90% is coated with the above-mentioned polymer mixture (1) and the like, and further overcoated with the polymer mixture (2) and the like. Therefore, when the polymer mixture (1) or the like is coated, about 10 to about 70% of the total surface area of the carrier core is exposed, and the polymer mixture (2) or the like is coated thereon. Therefore, the adhesiveness between the polymer mixture (1) and the like and the polymer mixture (2) and the like is higher than that between the polymer mixture (1) and the carrier core, and as a result, the carrier is used for a long time. At this time, if the coating film of the polymer mixture (2) or the like is peeled off due to friction or damage, the coating film of the polymer mixture (1) or the like is also peeled off, and the carrier core surface is exposed. Even if the carrier in which the surface of the carrier core is largely exposed is mixed with the toner, the toner is less likely to be charged, and thus it may be difficult to maintain the stability of the image quality for a long period of time.

The carrier described in Japanese Patent Laid-Open No. 11-295935 has about 50 to about 1 of the pores of the carrier core.
It is coated so that the polymer (1) is contained in 00%, but when the surface exposure ratio of the carrier core is large during the coating, as described above, the polymer (2) is used when the carrier is used for a long time. ) Is peeled off and the polymer (1)
May be peeled off, and as a result, the surface of the carrier core may be exposed and the chargeability of the toner may be reduced. Even when the exposed ratio of the carrier core when coated with the polymer (1) is not large, when the charging ability of the polymer (2) is larger than that of the polymer (1),
When the polymer (2) is peeled off / abraded, the polymer (1) having a low charge imparting ability or the core is exposed, so that stable charge cannot be maintained.

Further, in Japanese Patent Laid-Open No. 5-72815,
There has been proposed a carrier characterized in that an intermediate layer having a high charge imparting property is provided on a carrier core material, and a release coating layer is provided on the intermediate layer. It is described that the use of the above carrier exposes the intermediate layer having a high charge imparting ability due to abrasion of the coat layer, and as a result, the charge maintaining property is good.

However, when the coating layer is peeled off due to the stress in the developing machine and the intermediate layer is exposed, the carrier shows too high electrification, so that the charge imparting ability cannot be maintained for a long time.

[0010]

In the above-mentioned prior art, it is difficult to completely satisfy the required characteristics of the carrier required in recent years, and there is a problem that still needs to be improved. Is desired.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a carrier for developing an electrostatic latent image using a porous core excellent in stable charge imparting property of toner and the carrier. An electrostatic latent image developer containing the same is provided.

[0012]

In order to achieve the above object, the electrostatic latent image developing carrier of the present invention is an electrostatic latent image developing device in which a coating layer is formed on a porous carrier core having at least surface holes. Carrier, wherein the coating layer is a first coating layer filled in at least a part of the surface pores of the porous carrier core and coated so as to expose at least a part of the surface of the porous carrier core. And a second coating layer that covers the exposed portion of the porous carrier core and the first coating layer, the first coating layer having a higher charge imparting property than the second coating layer. However, the first coating layer is characterized in that the porous carrier core is coated with the surface exposure rate of the porous carrier core in the range of 2 to 7%.

Since the porous carrier core is coated with the first coating layer at a ratio shown by the core surface exposure rate, the adhesion surface area between the first coating layer and the porous carrier core is smaller than that of the conventional one. Since it is large, the adhesiveness between the first coating layer and the porous carrier core is higher than the adhesiveness between the first coating layer and the second coating layer. Therefore, even if the second coating layer peels off when the carrier is used for a long time, the first coating layer can remain on the carrier core. On the other hand, even if the second coating layer is peeled off when the carrier is used for a long time, the first coating layer has higher charge imparting property than the second coating layer, but only the first coating layer has high chargeability. By exhibiting the balance between the first coating layer and the surface of the carrier core as shown in the above-mentioned exposure ratio, the toner exhibits an appropriate charge amount and can maintain stable toner chargeability for a long time.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below.

<Electrostatic Latent Image Developing Carrier> The electrostatic latent image developing carrier (hereinafter referred to as “carrier”) of the embodiment of the present invention has a coating layer formed on a porous carrier core having at least surface pores. It is a carrier for electrostatic latent image development. The coating layer is a first coating layer that is filled in at least a part of the surface pores of the porous carrier core and is coated so as to expose at least a part of the surface of the porous carrier core, and the porous layer. A second coating layer that covers the exposed portion of the permeable carrier core and the first coating layer.
Furthermore, the first coating layer has a higher charge imparting property than the second coating layer, and the first coating layer has a surface exposure rate of the porous carrier core in the range of 2 to 7%. The porous carrier core is coated.

The carrier of the present embodiment will be described in detail below.

<Carrier Core> The term “porosity” of the porous carrier core means that it has, for example, a foam-like structure or a large number of pores. The porous carrier core has not only surface pores but also internal pores. You may have. The porous carrier core of the present invention has a BET specific surface area of about 1000 to about 5.
Refers to a core that is 000 cm ² / g. Examples of the carrier core include magnetic metals such as iron, steel, nickel and cobalt, oxides such as ferrite and magnetite. The average particle size of the carrier core is generally 10
One having a size of μm to 500 μm is used, preferably 30 μm
The thickness of m to 100 μm is used.

<Coating Layer> Further, the following polymer compounds are appropriately selected and sequentially coated so that the first coating layer has a higher charge imparting property than the second coating layer.

The first coating layer is coated so that the surface exposure rate of the porous carrier core is in the range of 2 to 7%, preferably 3 to 4%. When the surface exposure rate of the core is less than 2%, when the second coating layer is peeled off due to abrasion or destruction due to long-term use of the carrier, the carrier having a higher charge imparting property than the carrier core surface is exposed. Since the degree of exposure of the coating layer No. 1 becomes large, the charge of the entire carrier becomes too high. On the other hand, if the surface exposure rate of the carrier core exceeds 7%, the degree of exposure of the first coating layer decreases as compared to the degree of exposure of the surface of the carrier core when the second coating layer is peeled off by use as described above. As a result, the charge of the entire carrier becomes low, and as a result, the period for maintaining stable charge imparting property becomes short.

In the present embodiment, the surface exposure rate of the carrier core is obtained by [atomic% of Fe when the carrier core is coated with the first coating layer] / [atomic% of Fe of the carrier core], For example, it can be measured and calculated by the following measuring machine and conditions.

Measuring instrument: JPS-9000MX manufactured by JEOL Ltd. Conditions: measurement intensity; 10.0 kV 20 mV Source; MgKa Fe atomic%; The percentage of iron atoms of all elements having an atomic number of 3 or more is determined. In the examples described later, the surface exposure rate of the carrier core was measured using the same measuring machine and conditions as above.

When the first coating layer contains a polymer compound containing a nitrogen atom, the concentration of nitrogen atoms having the triboelectrification control function in the first coating layer is 5 to 100 ppm with respect to the weight of the carrier core. Yes, preferably 20-4
It is 5 ppm. If the nitrogen atom concentration is less than 5 ppm with respect to the carrier core weight, the chargeability may decrease, while if the nitrogen atom concentration exceeds 100 ppm with respect to the carrier core weight, the chargeability of the carrier is too high. May have. Examples of the method for measuring the nitrogen atom concentration include organic elemental analysis. As an apparatus used for the organic elemental analysis method, a chemiluminescence-type total elemental analysis apparatus can be used as an apparatus for measuring the concentration of only nitrogen atoms. Further, an oxygen circulating combustion type nitrogen carbon analyzer or the like can be used.

The polymer compound used in the first coating layer and the second coating layer is, for example, urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, phenol resin, epoxy resin, silicone resin. , Polyolefin resins such as polyethylene, polypropylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resins, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinylcarbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate. Copolymer; Styrene-acrylic acid copolymer; Polyacrylonitrile, polyvinylcarbazole, polyurethane; Amino resin, polymethylmethacrylate, fluororesin, polystyrene Down rubber, butyl rubber, butadiene rubber, nitrile rubber, ethylene-propylene rubber, Hypalon, acrylic rubber, urethane rubber, silicone rubber, fluorinated rubber, or mixtures thereof.

Further, the polymer compound used in the second coating layer for the purpose of suppressing the spent on the carrier has a critical surface tension of 35 dyn / cm or less, more preferably 30 d.
It is desirable to use a polymer compound having a yn / cm or less. Examples of the polymer compound having a critical surface tension of 35 dyn / cm or less that gives the above-mentioned low energy surface (that is, toner is hard to adhere) include, for example, straight silicone resin having an organosiloxane bond or its modified product, polyvinyl fluoride. (Critical surface tension: γc = 28
dyn / cm), polyvinylidene fluoride (γc = 25d
yn / cm), polytrifluoroethylene (γc = 22
dyn / cm), polytetrafluoroethylene (γc =
18 dyn / cm), polyhexafluoropropylene (γc = 16 dyn / cm), a copolymer of vinylidene fluoride and an acrylic monomer, a copolymer of vinylidene fluoride and vinyl fluoride, tetra Examples include high molecular compounds such as fluoroterpolymers such as terpolymers of fluoroethylene and vinylidene fluoride and non-fluorinated monomers, and it is particularly preferable that the fluororesin is contained, but the present invention is not limited thereto. Not a thing.

The first coating layer and the second coating layer may optionally contain conductive components or additives such as carbon black, metal oxides, metals or mixtures thereof. More specifically, examples of the conductive component include metals such as gold, silver, and copper, carbon black, semiconductive oxides such as titanium oxide and zinc oxide, titanium oxide, zinc oxide, barium sulfate, and boron. Examples thereof include aluminum oxide, potassium titanate powder and the like whose surface is covered with tin oxide, carbon black, or a metal. Further, carbon black is more preferable in terms of production stability, cost, and good conductivity. The type of carbon black is not particularly limited and known ones can be used, but the DBP oil absorption is 50 to 250 ml / 1, which has particularly good production stability.
Carbon black in the range of 00 g is preferred. Specifically, for example, Vulcan XC-72 (manufactured by Cabot), KETJEN black EC (LIONNAK)
UZO), TOKABLACK 5500, 450
0 (manufactured by Tokai Carbon Co., Ltd.), CONDUCTEX
975 (manufactured by COLUMBTIAN CARBON),
Conductive carbon black such as Printex L (manufactured by Degussa), conductive graphite such as EXP-1 Power (manufactured by Ogasawara Corp.), and other powders such as conductive zinc oxide and T-1 (manufactured by Mitsubishi Materials).
Oxide, SE surface-treated with antimony etc.
-0326 (manufactured by BASF) and the like, such as ferrosoferric oxide powder. The particle size of these conductive materials is 0.01 to 5 μm.
m is desirable.

The total content of the first and second coating layers is about 1 to about 7% by weight of the carrier core. The content of the conductive component is about 1 to about 60% by weight of the first coating layer or the second coating layer.

As the method for forming the second coating layer on the surface of the carrier core, for example, a dipping method in which powder of the carrier core is immersed in a solution for forming the coating layer, or a solution for forming the coating layer in the carrier core is used. Spraying method that sprays on the surface of, the fluidized bed method that sprays the coating layer forming solution while the carrier core is suspended by fluidized air, the carrier core and the coating layer forming solution are mixed in a kneader coater, and the solvent is removed A wet coating method such as a kneader coater method, a dry coating method in which a core material (carrier core) and a film forming material are mixed in a gas phase and heated and melted with almost no solvent to form a resin film. To be

The above method can also be used as a method of filling the inner holes and / or surface holes of the carrier core with the first coating layer.

In the present embodiment, when the polymer compound used for the first coating layer is soluble in the solvent, the dry coating method using almost no solvent for the second coating layer is particularly preferable. When the polymer compound of the first coating layer is insoluble in the solvent, the second coating layer may be wet coating method or dry coating method. The solvent used for the coating liquid for forming the coating layer in the case of using the wet coating method or the filling method is the above-mentioned first and second solvents.
It is not particularly limited as long as it dissolves the polymer compound used in the coating layer of, for example, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane. Any kind can be used.

<Electrostatic Latent Image Developer> The electrostatic latent image developer of the present invention (hereinafter referred to as “developer”) comprises at least toner and the above carrier.

As the pigment or colorant of the toner particles used in the above developer, carbon black, nigrosine,
Aniline blue, calcoil blue, chrome yellow,
Ultramarine Blue, DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 122, C.I.
I. Pigment Red 57: 1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 12,
C. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 3 and the like can be illustrated as a typical example.

Further, a binder may be added to the developer. Examples of the binder include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyl acetate,
Vinyl propionate, vinyl benzoate, vinyl acetate and other vinyl esters, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate , A-methylene aliphatic monocarboxylic acid ester such as dodecyl methacrylate, vinyl ether such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, homopolymer such as vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. Or a copolymer can be mentioned, and as a particularly typical binder, polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer,
Styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer,
Examples thereof include polyethylene and polypropylene.
Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin and waxes can be mentioned. Among these, particularly effective when polyester is used as a binder resin, for example,
A linear polyester resin composed of a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components is preferable. Further, the softening point is 90 to 150 ° C., the glass transition point is 5
A binder resin having 0 to 70 ° C., a number average molecular weight of 2000 to 6000, a weight average molecular weight of 8000 to 150,000, an acid value of 5 to 30, and a hydroxyl value of 5 to 40 can be particularly preferably used.

Further, the toner used in this embodiment can be prepared by a known method. Toner particles (particularly toner resin particles) and pigment particles or colorants are melt-mixed and then mechanically ground (kneading and pulverization), other emulsion aggregate spray drying, melt dispersion, dispersion polymerization and suspension polymerization, There are methods such as emulsion polymerization. However, it is not limited to these. Further, the above toner particles may optionally contain known additives such as a charge control agent and a fixing aid. In the developer of the present invention, for example, the total weight% of the polymer compound in the first coating layer and the second coating layer with respect to the carrier core particles is kept constant, and the ratio of the polymer compound used in the first and second coating layers is set. Alternatively, by changing the resin type, the triboelectrification characteristics can be changed while keeping the conductivity and the magnetic characteristics constant. Similarly, by changing the total weight% of both polymer compounds to the carrier core while keeping the ratio of the polymer compounds used in the first and second coating layers constant, the triboelectrification value is constant and the conductivity is constant. It is possible to prepare a developer composition having a changed value.

[0034]

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

The carrier core surface exposure rate in the following examples and comparative examples is measured by the above-mentioned measuring instrument “JPS-90”.
00MX "(manufactured by JEOL Ltd.) and the above-mentioned conditions. Further, the method for measuring the concentration of nitrogen atoms contained in the first coating layer in the carrier of the example and the comparative example is the oxygen circulation combustion method automatic high sensitivity NC-ANALYZER Sumigraph NC-901 manufactured by Sumika Chemical Analysis Service Co., Ltd.
Was performed using.

Synthesis Example 1. Cotton-like polyester resin (cotton-like polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol; glass transition temperature Tg = 62 ° C., number average molecular weight M)
n = 4000, weight average molecular weight Mw = 35000, acid value = 12, hydroxyl value = 25) 97 parts by weight, and a mixture of magenta pigment (CI Pigment Red 57) 3 parts by weight is kneaded in an extruder and jetted. After pulverizing with a mill, they were dispersed with a wind-powered classifier to obtain magenta toner particles having an average particle size of 8 μm. R972 is added to these magenta toner particles.
(Silica; manufactured by Nippon Aerosil Co., Ltd.) 0.4 wt% was added to a Henschel mixer to obtain a magenta toner (toner A).

<Evaluation Method> The following examples and comparative examples are
It evaluated by the following evaluation methods.

The magenta toner obtained in Synthesis Example 1 and the electrostatic charge image developer obtained by mixing the following carrier were used in an electrophotographic copying machine (DC1250, Fuji Xerox Co., Ltd.) at medium temperature. Humid environment (22 ℃, 55RH%)
I did a copy test. Fog and background stains were visually observed after copying 10 sheets, copying 3000 sheets, and copying 10,000 sheets. As for the image density, a chart in which halftone and solid images are mixed is used, and after copying 10 sheets, 300
After 0 copies, 10000 copies were visually observed. As the charge amount, CSG (charge spectrograph) was taken, and the CSG was image-analyzed to measure the charge amount.

Example 1. Ferrite with internal pores and surface pores (35 μm, BET specific surface area = 3420 cm ² /
g) is a carrier core, and the carrier core 100 is placed in the hole.
1.2 parts by weight of a polyamide-imide resin (-24.5 μC / g) as a first coating layer, based on parts by weight, was mechanically filled with an attritor to give a proper share, and the carrier core was first filled. Of the coating layer. At this time, the carrier core surface exposure ratio was 5.0%, and the nitrogen atom concentration contained in the polyamide-imide resin of the first coating layer was 30 ppm with respect to the carrier core weight. Then the first
2 parts by weight of methyldimethylsilicone resin (-22.5 μC / g) was dispersed in toluene as the second coating layer, and the resin dispersion was spray coated using a fluid coating device. After that, heat treatment was performed in a fluidized tank at 250 ° C. for about 30 minutes, and the entire surface was covered by curing to obtain a carrier (specific gravity 3.0).
Further, the printing durability of the magenta developer obtained by mixing the magenta toner (toner A) with the carrier of Example 1 was evaluated under the above evaluation conditions. As a result, fog, background stain and image density were obtained even after copying 10,000 sheets. A stable image was obtained without any fluctuation. Further, the image density was stable and there was no problem. Further, the charge amount of the toner was −18 μC / g even after 100000 sheets with respect to −20 μC / g, and the change in the charge amount was small.

Example 2. 0.2 parts by weight of an epoxy resin as a binder and 0.1 parts by weight of carbon black as a conductive agent were added to 1 part by weight of a methyldimethylsilicone resin (-
22.5 μC / g) mixed and dispersed in methyl ethyl ketone, and 100 parts by weight of a ferrite core (50 μm, BET specific surface area = 2820 cm ² / g) having internal pores and surface pores in the first coating layer dispersion. Was filled in the hole by dipping, and the carrier core was coated with the first coating layer. At this time, the carrier core surface exposure rate is 3.
It was 2%. Then, 2 parts by weight of a methyl acrylate resin (-18.0 μC / g) was dispersed in toluene as a second coating layer on the first coating layer, and the resin dispersion was applied to a fluid coating device. After spray-coating using, the mixture was heat-treated in a fluidized tank at 250 ° C. for about 30 minutes and cured to coat the entire surface to obtain a carrier (specific gravity 2.9). Further, the printing durability of the magenta developer obtained by mixing the magenta toner (toner A) and the carrier of Example 2 was evaluated under the above evaluation conditions, and the same results as in Example 1 were shown. The toner charge is -22
-21 μC / g after 100,000 sheets against μC / g
The change in the charge amount was smaller than that in Example 1.

Comparative Example 1. (When the carrier core surface exposure rate is too small) A ferrite core having internal holes and surface holes as a carrier core (35 μm, BET specific surface area = 3420 cm ² /
g) 1 part by weight of a polyamide-imide resin (-24.5 parts) in which 100 parts by weight is dispersed in ethanol as the first coating layer.
Coated by dipping in μC / g). At this time, the carrier core surface exposure ratio was 1.2%, and the nitrogen atom concentration contained in the polyamide-imide resin of the first coating layer with respect to the carrier core weight was 35 ppm. Then, the first coating layer was coated, and the second coating layer was methyldimethylsilicone resin (-22.5 μC /
g) 1 part by weight of the resin is dispersed in toluene, and the resin dispersion is spray-coated using a fluid coating device.
Heat treatment was performed in a fluidized tank at 250 ° C. for about 30 minutes, and the entire surface was covered by curing to obtain a carrier (specific gravity 3.4). Further, a magenta developer obtained by mixing the magenta toner (toner A) used in Example 1 and the carrier of Comparative Example 1 was evaluated under the above evaluation conditions, and as a result, 30
Clouds were generated at the point after copying 00 sheets, and stains and fog in the copying machine were noticeable. In addition, the density unevenness was also noticeable with respect to the image density (3000 at the initial −20 μC / g).
After the printing, -11 μC / g).

Comparative Example 2. (When the carrier core surface exposure rate is too large) Ferrite core (35 μm, BET
Specific surface area = 3420 cm ² / g) 100 parts by weight
The coating layer was coated by immersing it in 1 part by weight of a polyamideimide resin (-24.5 μC / g) dispersed in ethanol. At this time, the carrier core surface exposure rate is 1
The concentration was 0.2%, and the nitrogen atom concentration contained in the polyamide-imide resin of the first coating layer was 7 ppm based on the weight of the carrier core. Then, 1 part by weight of methyldimethylsilicone resin (-22.5 μC / g) was dispersed in toluene as the second coating layer on the first coating layer, and the resin dispersion was applied to a fluid coating device. After spray-coating with the composition, heat treatment was carried out at 250 ° C. for about 30 minutes in a fluidized tank, and the entire surface was coated by curing to obtain a carrier (specific gravity 3.4). Further, the magenta developer obtained by mixing the magenta toner (toner A) used in Example 1 and the carrier of Comparative Example 2 was evaluated under the above conditions, and as a result, the cloud was formed after copying 10,000 sheets. Occurred, and fog and background stain were conspicuous (initial −20 μC / g
-12 μC / g after 10,000 sheets.

Comparative Example 3. (Charging property: first coating layer <
Second coating layer) Ferrite core (35 μm, BET) as carrier core
Specific surface area = 3420 cm ² / g) 100 parts by weight
The coating layer was prepared by immersing it in 1 part by weight of methyldimethylsilicone resin (-22.5 μC / g) dispersed in ethanol. The carrier core surface exposure ratio at this time was 4.2%. Then, 1 part by weight of a polyamide-imide resin (-24.5 μC / g) was dispersed in toluene as a second coating layer on the first coating layer, and the resin dispersion was used with a fluid coating device. After spray-coating, a heat treatment was performed in a fluidized tank at 250 ° C. for about 30 minutes, and the entire surface was covered by curing to obtain a carrier (specific gravity 3.4). Further, the magenta developer obtained by mixing the magenta toner (toner A) used in Example 1 and the carrier of Comparative Example 3 was evaluated under the above evaluation conditions, and as a result, it was clouded after copying 10,000 sheets. Fogging and ground stains were noticeable (initial −20 μC
/ G, -5 μC / g after 10,000 sheets).

Comparative Example 4. (Using non-porous carrier core
If) Ferrite core as carrier core (35μm, BET
Specific surface area = 830 cm ²/ G) 100 parts by weight of the first
1 part polyamide dispersed in ethanol as coating layer
By immersing in imide resin (-24.5 μC / g)
Coated. At this time, the carrier core surface exposure rate is 1.
1% of the first coating layer relative to the weight of the carrier core
The nitrogen atom concentration contained in the polyamide-imide resin is 33.
It was ppm. The first coating layer is then coated
A methyl dimethyl silicone resin as the second coating layer
Disperse 1 part by weight of (-22.5 μC / g) in toluene.
The resin dispersion using a fluid coating device.
After pre-coating, flow tank at 250 ℃ for about 30 minutes
The entire surface is covered by heat treatment and curing
A carrier was obtained (specific gravity 3.4). Further, used in Example 1.
Magenta toner (toner A) and carrier of Comparative Example 4
The evaluation of the magenta developer obtained by mixing
As a result of the above, the cloud was
It occurred, and stains and fog inside the copying machine were noticeable. Well
In addition, the density unevenness was also noticeable in the image density (initial-2
0 μC / g, -12 μC / g after 3000 sheets
g).

In all the above examples, the triboelectrification value in the parentheses was obtained by mechanically sharing an appropriate share of the resin described in the parentheses with an attritor to obtain ferrite particles (35 μm).
Coated carrier (the average thickness of the resin coating layer is 0.8
μm). It is a value measured by the above method with respect to 100 parts by weight of the developer mixed with 6 parts by weight of the magenta toner of Synthesis Example 1.

[0046]

The developer containing the carrier for developing an electrostatic latent image of the present invention has a long life which can stably maintain the carrier resistance and the charge amount from the initial use to the long term, and also has the productivity. It is a good one. Further, the electrostatic latent image developer of the present invention is particularly suitable for application to a color developer such as a full color compatible developer.

Claims (3)

[Claims] 1. A carrier for electrostatic latent image development having a coating layer formed on the surface of a porous carrier core having at least surface pores, wherein the coating layer is at least one of the surface pores of the porous carrier core. A first coating layer that is filled in a portion to cover at least a part of the surface of the porous carrier core, and a coating portion that covers the exposed portion of the porous carrier core and the first coating layer. Two coating layers, the first coating layer has a higher charge imparting property than the second coating layer, and the first coating layer has a surface exposure ratio of 2 to 2 of the porous carrier core. A carrier for electrostatic latent image development, characterized in that the porous carrier core is coated in a range of 7%. 2. The first coating layer contains a polymer compound containing a nitrogen atom, and the concentration of nitrogen atoms contained in the first coating layer is 5 to 5 with respect to the weight of the porous carrier core.
The carrier for developing an electrostatic latent image according to claim 1, wherein the carrier is 100 ppm. 3. An electrostatic latent image developer comprising at least a toner and a carrier, wherein the carrier is the electrostatic latent image developing carrier according to claim 1 or 2. Electrostatic latent image developer.