JPH07248652A - Electrophotographic carrier, manufacture thereof, and electrification applying member - Google Patents

Abstract

PURPOSE:To improve the electrification maintaining property and image quality maintaining property of a carrier and an electrification applying member and obtain excellent image quality having no density irregularity and backing stain of image by containing a specific polyamide resin as a cover resin. CONSTITUTION:A polyamide resin having the melting point in the range of 100-270 deg.C and the melt viscosity in the range of 10<2>-10<3> poise is contained in the electrophotographic carrier coated with a resin on a core material as the cover resin. Any resin containing the amide group in the principal chain may be used for the polyamide resin, and nylon-6, nylon-6,6, nylon-6,10, nylon-11, and nylon-12 can be used. The polyamide resin converting partial or all amide- bound hydrogen into alkoxyalkyl due to its alcohol solubility is on the market, however, it is not preferable because of its inferiority in heat resistance, film strength, and electrification characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier used for developing an electrostatic charge image formed by an electrophotographic method, an electrostatic recording method or the like with a two-component developer, a method for producing the same and an electrophotographic carrier. The present invention relates to a charging member.

[0002]

2. Description of the Related Art A method of visualizing image information through an electrostatic charge image such as an electrophotographic method is currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on a photoconductor in a charging and exposing process, and the electrostatic latent image is developed with a developer containing toner,
It is visualized through the transfer and fixing steps. The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer such as a magnetic toner which is used alone as a toner. , The functions such as charging are shared, and the functions are separated as a developer, so that the developer can be easily designed and is widely used at present.

In particular, a developer using a carrier coated with a resin is excellent in charge controllability, and it is relatively easy to improve environmental dependency, stability over time, and the like. Further, as a developing method, a cascade method has been used for a long time, but at present, a magnetic brush method using a magnetic roll as a developer carrying carrier is mainly used.

In the magnetic brush method using a two-component developer,
There are problems such as a decrease in image density due to charge deterioration of the developer, a remarkable background stain, a rough image due to carrier adhesion to the image, carrier consumption, and uneven image density. The charge deterioration of the developer is apt to occur due to the adhesion of the toner component to the carrier coat layer or the peeling of the coat, and when the coat layer becomes non-uniform, the toner may be deteriorated when the environment changes such as humidity and temperature. At the time of addition, when the toner concentration is high, background stains tend to occur.

In order to prevent these charge deteriorations, the hardness of the coating resin is increased to suppress the peeling, or the surface energy of the coating resin is reduced to prevent the toner component from sticking to the carrier coat layer. Has been proposed.

On the other hand, a polyamide resin has been considered as a carrier coating resin having high wear resistance and elasticity.
Generally, polyamide resins have poor solubility in solvents and it is difficult to uniformly coat the carrier core material. Therefore, a carrier in which a core material is coated with a solution containing an alcohol-soluble polyamide resin as a coating resin (JP-A-1-
118150, JP-A-1-118151,
(See JP-A-4-188160) or a carrier in which polyamide particles are mixed with core particles and the resin is melted by a hot kneader to coat the core particles (JP-A-49-49).
No. 115549) is proposed.

[0007]

However, when the alcohol solubilization treatment is carried out, the film-forming property and film strength of the polyamide resin,
Since the abrasion resistance is deteriorated and the above polyamide resin is difficult to be pulverized, it is difficult to form a uniform coat layer even by the dry mixing and melt coating method, and the above polyamide resin is hygroscopic. Therefore, there was a problem such as lack of environmental stability of charging. In general, the dry mixing melt coating method is an effective method for forming a uniform coating layer, but in recent years, there is a tendency for the toner particles to have a smaller diameter and the toner material to have a lower melting point for improving image quality. There is a situation in which it is not possible to manufacture a carrier having sufficient characteristics only by adopting this method.

Therefore, the present invention solves the above problems,
The present invention aims to provide an electrophotographic carrier, a method for manufacturing the same, and a charging member having the following features. Improving image quality maintenance due to changes in charging properties due to environmental changes, and using coating resin with excellent abrasion resistance to ensure uniform coating layer retention and improve charging stability. An image with black solids and fine lines that improves background stains, extends the life of the developer and charge imparting member, prevents carrier adhesion and ensures stable high image quality, and suppresses carrier consumption. Reproducibility is excellent, and by selecting a coating resin that does not require pulverization treatment, it is possible to form a uniform coating layer by the dry mixing melt coating method.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to a coating resin that makes it possible to form a uniform coating film by taking advantage of the characteristics of a polyamide resin, and as a result, have a specific melting point and melt viscosity and are insoluble in alcohol. The present invention was completed by making it possible to provide an electrophotographic carrier and an electrophotographic charge-giving member having the above-mentioned properties by using the polyamide resin described in 1. The specific aspects of the present invention are as follows.

(1) In an electrophotographic carrier comprising a core material coated with a resin, the coating resin has a melting point of 100.
A carrier for electrophotography, which contains a polyamide resin in the range of ˜270 ° C. and having a melt viscosity in the range of 10 ² to 10 ³ poise at a temperature 30 ° C. higher than the melting point.

(2) A method for producing a carrier for electrophotography, characterized in that in the process of dry-mixing the coating resin powder and the core particles, the coating resin is heated to a temperature equal to or higher than the melting point to coat the core particles. . (3) A method for producing an electrophotographic carrier, which comprises dry-mixing the coating resin powder and the core particles at room temperature and then heating the coating resin powder to a temperature equal to or higher than the melting point of the coating resin to coat the core particles. (4) After heating the core particles above the melting point of the coating resin,
A method for producing an electrophotographic carrier, which comprises adding and mixing the coating resin to coat the surface of the core particles with the resin.

(5) To the carrier particles obtained by the manufacturing method of (2) to (4), another resin that melts at a temperature lower than the melting point of the polyamide resin is added and mixed, and only the other resin is melted. A method for producing an electrophotographic carrier, characterized in that the surface of the carrier particles is coated with another resin to form a multilayer carrier. (6) An electrophotographic carrier characterized by forming a multilayer carrier by solution-coating another resin dissolved in a solvent on the surface of carrier particles obtained by the manufacturing method according to the above (2) to (4). Production method.

(7) In the electrification-imparting member for electrophotography, which is coated with a resin, the coating resin has a melting point of 100 to
A charge imparting member for electrophotography, comprising a polyamide resin in the range of 270 ° C. and having a melt viscosity in the range of 10 ² to 10 ³ poise at a temperature 30 ° C. higher than the melting point.

[0014]

The polyamide resin used in the present invention has a melting point of 1
0 to 270 ° C, preferably 120 to 265 ° C, more preferably 130 to 265 ° C, from the melting point to 30
The melt viscosity at a temperature higher by ℃ is 10 ² to 10 ³ poise,
Preferably 2 × 10 ^{2 to} 9 × 10 ² , more preferably 3
Those in the range of × 10 ^{2 to} 8.5 × 10 ² are suitable. When the melting point is lower than 100 ° C, the fluidization of the carrier is deteriorated by heat in an actual machine, and when it exceeds 270 ° C, the polyamide resin is decomposed during melting in the manufacturing process. Further, if the melt viscosity is less than 10 ² poise, the molecular weight of the polyamide resin becomes too small, and sufficient coating strength cannot be obtained at the time of coating. If it exceeds 10 ³ poise, the viscosity at the time of heating and melting becomes too high, resulting in a uniform coating. It becomes difficult to form a simple coating. These physical properties can be obtained by adjusting the molecular weight or the degree of polymerization.

The above polyamide resin may be any resin containing an amide group in the main chain, and nylon-6, nylon-6,6, nylon-6,10, nylon-11, nylon-12, etc. may be used. You can A polyamide resin in which some or all of the amide bond hydrogens are alkoxyalkylated for the purpose of solubilizing alcohol is commercially available, but it is not preferable because it is inferior in heat resistance, coating strength, and charging property.

The coating resin used in the present invention may be the above-mentioned polyamide resin alone, or may be used as a mixture with another resin. Other resins include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethylene, monochloroethylene, copolymers of vinyl-based fluorine-containing monomers such as trifluoroethylene; styrene, chlorostyrene, methylstyrene, etc. Styrenes; α-methylene aliphatic monocarboxylic acids such as methyl methacrylate, methyl acrylate, propyl acrylate, lauryl acrylate, methacrylic acid, acrylic acid, butyl methacrylate, butyl acrylate, 2 ethylhexyl acrylate, ethyl methacrylate; dimethylaminoethyl methacrylate, etc. Nitrogen-containing acrylics; Nitriles such as acrylonitrile and methacrylonitrile; Vinyl pyridines such as 2 vinyl pyridine and 4 vinyl pyridine; Vinyl Ether compounds;
Vinyl ketones; olefins such as ethylene, propylene and butadiene; homopolymers or copolymers of silicons such as methyl silicon and methyl phenyl silicon can be used, and polyesters containing bisphenol, glycol and the like. Can also be used.

The total amount of the coating resin is 0.1 to 10% by weight, preferably 1.0 to 7.0% by weight, more preferably 1.5 to 6.0% by weight, based on the carrier. But,
It is suitable for achieving both image quality, secondary obstacles, and chargeability. The content of the above polyamide resin in the coating resin is in the range of 5 to 100% by weight, preferably 10 to 100% by weight, and more preferably 20 to 100% by weight. It is suitable for raising the charge and improving the environmental stability. The polyamide resin can be added in the form of granules, powder or pellets.

As the core particles used in the present invention, particles having a substantially spherical shape such as ferrite particles and granulated magnetite particles having a controllable surface property are suitable, and an average particle diameter of 20 to 120 μm. Ranges are preferred.

Further, as the charge-imparting member of the present invention, the surface of a metal sleeve, a blade or the like can be coated with the above coating resin and used.

In the method for producing a carrier of the present invention, the coating resin powder containing the polyamide resin and the core particles are mixed without using a solvent, and then the mixture is heated to a temperature not lower than the melting point of the coating resin and kneaded to obtain a coating. The resin is melted to coat the core particles, and a heating kneader, a heating Henschel mixer, a UM mixer, a planetary mixer or the like can be used as a manufacturing apparatus.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner is a binder resin in which a colorant or the like is dispersed. Examples of the binder resin used for the toner include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and methacryl. Α-methylene aliphatic monocarboxylic acid esters such as methyl acidate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; 2-vinylpyridine, Vinyl pyridines such as 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; ethylene, propylene ,
Polymers of monomers such as unsaturated hydrocarbons such as isoprene and butadiene and halides thereof, halogenated unsaturated hydrocarbons such as chloroprene, or copolymers obtained by combining two or more of these monomers Polymers and mixtures thereof, and non-vinyl condensation resins such as rosin-modified phenol formalin resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin and polyether resin, or these and vinyl resins And a mixture thereof.

The colorant used in the toner may be carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue or a mixture thereof.

As the toner component other than the colorant, there are a charge control agent, an offset preventive agent, a fluidity improving agent and the like, and a magnetic fine powder may be contained if necessary. The particle size of the toner tends to be small and the image quality tends to be small, and it is preferable that the toner has an average diameter of about 5 to 12 microns, particularly 5 to 10 microns.

[0024]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. In the examples, “part” means part by weight. Also,
The melting point is measured by a differential scanning calorimeter DSC-5 manufactured by Shimadzu Corporation.
Further, the melt viscosity was measured by using a flow tester CFT-500C manufactured by Shimadzu Corporation with a die having a diameter of 0.5 mm at a load of 20 kgf and a heating rate of 3 ° C./min. The peeling of the resin on the carrier surface was the result of observation with an SEM (scanning electron microscope).

Example 1 1000 parts of Cu-Zn ferrite (manufactured by Powdertec, average particle size: 50 μ) and 30 parts of nylon-6 powder (melting point viscosity: 225 ° C., 255 ° C. 8 × 10 ² poise) 1 with a heater
After mixing for 5 minutes at room temperature in an L small kneader, the heat medium temperature was raised to 260 ° C., and the mixture was stirred and kneaded for 40 minutes.
The heater was turned off and the mixture was cooled for 50 minutes while stirring. Then, it was sieved with a 105 μ sieve to obtain a carrier.

Example 2 1000 parts of Cu—Zn ferrite (Powdertec, average particle size: 50 μ) was heated in a 1 L small kneader equipped with a heater at a heating medium temperature of 220 ° C.
Nylon-12 pellets (melting point: 175 ° C., melt viscosity at 206 ° C .: 5 × 10
⁽² poise) 30 parts, and after stirring and kneading for 40 minutes,
The heater was turned off and the mixture was cooled for 50 minutes while stirring. Then, it was sieved with a 105 μ sieve to obtain a carrier.

Example 3 1000 parts of magnetite core (average particle size 50 μ) and nylon-6,6 powder (melting point 2
Melt viscosity at 65 ° C. and 295 ° C. 7 × 10 ² poise)
After mixing 10 parts in a 1 L small kneader equipped with a heater and a pressure reducing device at room temperature and atmospheric pressure for 5 minutes, the heat medium temperature was raised to 300 ° C. and the mixture was stirred and kneaded for 40 minutes, and then,
The heater was turned off and the mixture was cooled for 50 minutes while stirring. Then, 20 parts of methyl methacrylate resin and 50 parts of toluene
After adding 0 part and mixing and dissolving at room temperature and atmospheric pressure for 15 minutes, the solvent toluene was distilled off by heating under reduced pressure with stirring. Then, it was sieved with a 105 μ sieve to obtain a carrier.

[Comparative Example 1] 1000 parts of Cu-Zn ferrite (manufactured by Powdertec, average particle size: 50 µ) and nylon-6 powder (melting point: 225 ° C, 255 ° C: melt viscosity 5)
A carrier was obtained in the same manner as in Example 1 except that 30 parts of (× 10 ³ poise) was used.

[Comparative Example 2] 1000 parts of Cu-Zn ferrite (manufactured by Powdertec, average particle size: 50 µ) and methoxymethylated nylon-6 powder (methoxymethylation rate: 35 m)
ol%, melting point 225 ° C., melt viscosity at 255 ° C. 7 ×
A carrier was obtained in the same manner as in Example 1 using 10 parts of 10 ³ poise).

(Toner Production Example 1) 87 parts of a binder resin (styrene-n-butyl methacrylate), 8 parts of carbon black (BPL made by Cabot), 1 part of a charge control agent (TRH made by Hodogaya Chemical Co., Ltd.), and polypropylene wax ( An average particle size of 7.
5 μm of toner particles were obtained. Colloidal silica (R972 made by Nippon Aerosil) 1 is used for 100 parts of the toner particles.
Parts were added and mixed with a Henschel mixer to obtain a toner for evaluation.

(Image quality evaluation test) A developer was prepared by mixing the above-mentioned toner with the carrier obtained in Examples 1, 2 and 3 and Comparative Examples 1 and 2 so that the toner concentration was 5%. An image quality evaluation test was carried out on these developers using a modified machine of Fuji Xerox 5039. As shown in Table 1, the carriers of Examples 1, 2 and 3 had good image quality stability and peeling of the coating agent. It turns out that it is excellent. Comparative Example 2
With respect to the developer using the carrier No. 1, the image quality maintenance test for 100,000 copies was omitted because the coating state of the carrier was poor and the image quality deteriorated from the beginning.

[0032]

[Table 1]

Example 4 Nylon-6 powder (melting point 22
Melt viscosity 8 × 10 ² poise at 5 ° C. and 255 ° C.) was melted at 260 ° C., and dipping was performed on the surface of a stainless steel developing roll sleeve for a laser printer 4105 manufactured by Fuji Xerox Co., Ltd. to form a film of 50 g / m ² on the sleeve. Formed.

Comparative Example 3 A stainless developing roller sleeve for a laser printer 4105 manufactured by Fuji Xerox Co., Ltd. was used as it was.

(Production Example 2 of toner) 44 parts of binder resin (styrene-n-butyl methacrylate), 50 parts of magnetite powder (EPT-1000 manufactured by Toda Kogyo Co., Ltd.), 2 parts of charge control agent (TRH manufactured by Hodogaya Chemical Co., Ltd.), Further, 4 parts of polypropylene wax (660P manufactured by Sanyo Kasei) was used to obtain toner particles having an average particle size of 9.0 μ by a kneading and pulverizing method. To 100 parts of the toner particles, 0.8 part of colloidal silica (R972 manufactured by Nippon Aerosil) was added and mixed with a Henschel mixer to obtain a toner for evaluation.

(Image Quality Evaluation Test) The developing roll sleeves obtained in Example 4 and Comparative Example 3 were mounted on a Fuji Xerox laser printer 4105, and an image quality evaluation test was conducted using the toner of Toner Production Example 2. As shown in Table 2,
It can be seen that the developing roll sleeve of Example 4 is superior in image quality stability.

[0037]

[Table 2]

[0038]

According to the present invention, by adopting the above-mentioned constitution, it is possible to greatly improve the charge maintaining property and the image quality maintaining property of the carrier and the charge imparting member, and there is no uneven density or scumming on the image. It is now possible to obtain excellent image quality. In particular, when a carrier is produced by the dry mixing and melt coating method using the above polyamide resin, it becomes possible to uniformly and efficiently produce the resin coating on the surface of the core particles.

Claims (3)

[Claims] 1. An electrophotographic carrier comprising a core material coated with a resin, wherein the coating resin has a melting point of 100 to 100.
A carrier for electrophotography, comprising a polyamide resin in the range of 270 ° C. and having a melt viscosity in the range of 10 ² to 10 ³ poise at a temperature 30 ° C. higher than the melting point. 2. A process of dry mixing the coating resin powder containing the polyamide resin according to claim 1 and core particles,
A method of manufacturing a carrier for electrophotography, comprising heating the coating resin to a temperature equal to or higher than a melting point to coat the core particles. 3. An electrophotographic charge imparting member coated with a resin, wherein the coating resin has a melting point of 100 to 2
A charging member for electrophotography, comprising a polyamide resin in the range of 70 ° C. and having a melt viscosity in the range of 10 ² to 10 ³ poise at a temperature higher than the melting point by 30 ° C.