JPH086307A - Electrophotographic carrier, manufacture thereof, and electrophotographic electrification imparting member - Google Patents

Abstract

PURPOSE:To manufacture an electrophotographic carrier improving the electrification maintenance property, environmental stability, and image quality maintenance property, capable of obtaining the excellent image quality having no density irregularity on an image and no blot on a background, and uniformly and efficiently applied on the surface of a core material and manufacture an electrification imparting member. CONSTITUTION:This coating layer is a thermosetting resin constituted of a condensate made of a guanamine resin of 40wt.% or above, e.g. guanamines, formaldehyde, and alcohols, and the second resin having the functional group capable of being reacted and cross-linked with the guanamine resin. The coating layer is baked, heated to the hardening temperature or above, and hardened on a core material to manufacture an electrophotographic carrier. The core material is coated with a coating resin to manufacture an electrophotographic electrification imparting member.

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 the charging and exposing steps, the electrostatic latent image is developed with a developer containing toner, and the image is visualized through transfer and fixing steps. The developer used here is a two-component developer consisting of toner and carrier,
There is a one-component developer that can be used alone, such as magnetic toner, but in a two-component developer, the carrier shares functions such as stirring, carrying, and charging of the developer, and the functions are separated as the developer. Currently, it is widely used because of its good controllability. In particular, a developer using a resin-coated carrier has excellent charge controllability, and it is relatively easy to improve environmental dependency and temporal stability. As a developing method,
Although the cascade method and the like have been used for a long time, the magnetic brush method using a magnetic roll as a developer carrying carrier is now the mainstream.

In the magnetic brush method using a two-component developer,
There are problems such as a reduction in image density due to charge deterioration of the developer, occurrence of remarkable background stain, image roughness due to carrier adhesion to the image, carrier consumption, and image density unevenness. 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. When the toner concentration is high, background stains tend to occur.

In order to prevent these charge deteriorations, the hardness of the coating resin should be raised to prevent peeling, or the surface energy of the coating resin should be lowered to prevent the toner components from sticking to the carrier coat layer. Efforts have been made to prevent charging deterioration by combining the methods.

For example, a thermoplastic resin having an unreacted hydroxyl group and an alkoxylated melamine are used for the purpose of enhancing adhesion to a core substance and coating strength, and improving fluidity of carrier, moisture resistance and separability from toner. A carrier in which a core substance is coated with a resin component obtained by curing a resin (JP-A-62-26).
2057), a carrier in which a core substance is coated with a resin obtained by crosslinking an acrylic resin and a melamine resin for the purpose of improving durability and environment resistance (see JP-A-2-79862), durability and heat resistance. And a carrier in which a core substance is coated with an acrylic resin cross-linked with a melamine-formaldehyde resin composition for the purpose of improving environmental resistance (JP-A-5-252).
However, there is a problem that a carrier containing a melamine resin causes a large decrease in charge at high temperature and high humidity.

For the purpose of improving the triboelectric charge imparting ability, 0.1 to 2 parts of guanamine, a guanamine derivative or a guanamine-based condensate are added to 100 parts by weight of the coating resin.
A carrier in which a core substance is coated with a coating resin containing 0 part by weight has been proposed (see Japanese Patent Laid-Open No. 60-201360).
However, it was not possible to maintain a sufficient charge amount for a long period of time.

On the other hand, as a coating method for forming a uniform and firm coating on the surface of the core substance, a method has been proposed in which the coating resin and the core substance are mixed in a dry state and then the coating resin is melted to form a coating. However, in view of the recent decrease in the diameter of toner particles for improving the image quality and the lowering of the melting point of toner materials, it cannot be immediately said that the above method also has a sufficient effect.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve the above-mentioned drawbacks and provide an electrophotographic carrier and a method for producing the same, and an electrophotographic charge imparting member having the following features. Is. (1) To improve the image maintainability against changes in charging property due to environmental changes. (2) To improve the background stain when adding toner and extend the life of the developer and the charging member. (3) To prevent the carrier from adhering to ensure stable and high image quality and to suppress the consumption of the carrier. (4) The coating layer should not peel off even after long-term use. (5) To provide a positive charge carrier and a positive charge imparting member for developing an electrostatic charge image, which can provide image quality excellent in solid black and fine line reproducibility. (6) To provide a method for efficiently manufacturing the carrier.

[0009]

Means for Solving the Problems The inventors of the present invention have diligently studied a coating resin containing a guanamine resin and a second resin capable of being heat-cured, and as a result, the above-mentioned problems can be solved. The electrophotographic carrier, the manufacturing method thereof, and the electrophotographic charge imparting member that can be completed have been completed. The specific mode is as follows.

(1) In an electrophotographic carrier having a core material provided with a coating layer, the coating layer comprises 40% by weight or more of a guanamine resin and a second resin having a functional group capable of reacting with the guanamine resin. A carrier for electrophotography, which is made of a thermosetting resin.

(2) The electrophotographic carrier according to (2) above, wherein the guanamine resin is a cocondensation product of guanamines, formaldehyde and alcohols.

(3) The electrophotographic carrier according to (2) above, wherein the guanamine resin is a benzoguanamine resin.

(4) Any one of the above (1) to (3), characterized in that the second resin comprises at least one of acrylic resin, polyester resin and alkyd resin.
The electrophotographic carrier according to the item.

(5) The above (1) to (4), wherein a resin for reducing the surface energy is added to the coating resin.
The electrophotographic carrier according to any one of items 1.

(6) The electrophotographic carrier according to any one of the above (1) to (5), characterized in that a resin for adjusting the charge amount is added to the coating resin.

(7) The resin according to any one of the above items (1) to (6) and the core substance are heated and mixed at a temperature lower than the curing temperature of the resin to form a coating layer, and then the coating layer is formed. A method for producing an electrophotographic carrier, which comprises heating the layer to a temperature higher than a baking temperature to cure the layer.

(8) A charge imparting member for electrophotography, comprising a core substance coated with the coating resin according to any one of the above items (1) to (6).

The carriers described in the above items (1) to (6) are suitable for a positively charged carrier for developing an electrostatic image and a positive charging member for developing an electrostatic image.

[0019]

According to the present invention, by using the above-mentioned guanamine resin as the coating resin, the charge maintaining property, the environmental stability and the image quality maintaining property can be greatly improved, and the image is free from uneven density and background stains. An excellent image quality can be provided, and a method for manufacturing a carrier that uniformly and efficiently coats the resin on the surface of the core substance can be provided.

The guanamine resin used in the present invention includes:
Mention may be made of co-condensates of guanamines, formaldehyde and alcohols. Examples of guanamines contained in the molecule include acetoguanamine, benzoguanamine, cyclohexylguanamine, and cyclotetraoxaspiroundecane (CTU) guanamine, but benzoguanamine is most suitable in terms of environmental stability and sustainability of charging. Is.

The content of guanamine resin is 40% by weight or more, preferably 45% by weight or more, based on the total amount of coating resin,
It is more preferably 50% by weight or more and 95% by weight or less, preferably 90% by weight or less. Four
If it is less than 0% by weight, sufficient charge control ability cannot be exhibited for a long time, and if it exceeds 95% by weight,
Sufficient film strength cannot be obtained even by baking and curing.

The second resin which can be heat-cured with the guanamine resin used in the present invention is not particularly limited as long as it has a functional group capable of reacting with the guanamine resin and cross-links, but an acrylic resin, a polyester resin and an alkyd resin can be used. It is particularly preferable in terms of charge controllability and film formation.

As the coating resin used in the present invention, a third resin may be mixed and used for the purpose of reducing the surface energy and adjusting the charge amount. As the third resin, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethylene,
Polymers of fluorine-containing monomers such as monochloroethylene, trifluoroethylene and perfluoroalkyl acrylate; styrenes such as styrene, chlorostyrene and methylstyrene; methyl methacrylate, methyl acrylate, propyl acrylate, lauryl acrylate, methacrylic acid, acrylic acid, Α-methylene aliphatic monocarboxylic acids such as butyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, and ethyl methacrylate; nitrogen-containing aliphatic monocarboxylic acids such as dimethylaminoethyl methacrylate; nitriles such as acrylonitrile and methacrylonitrile; 2- Vinyl pyridines such as vinyl pyridine and 4-vinyl pyridine; vinyl ethers; vinyl ketones: olefins such as ethylene, propylene and butadiene; Rushirikon can be used homopolymers or copolymers such as silicone such as methyl phenyl silicone. Further, polyesters containing bisphenol, glycol and the like can also be used.

As the magnetic core substance, particles having a substantially spherical shape such as ordinary ferrite particles and granulated magnetite and having a controllable surface property can be used. As the surface property control means, raw material particles can be used. There are diameters and firing conditions. The particle size of the core particles is usually in the range of 20 to 120 μm.

The total amount of the coating resin is 0.1 to 10% by weight, preferably 1.0 to 7% by weight, and more preferably 1.5 to 6% by weight, based on the carrier. It is suitable from the standpoint of ensuring the charging property, secondary obstacle, and ensuring the charging property. Further, in the charging member, the surface of the metal sleeve or the blade can be coated with the above coating resin.

In the method for producing a carrier of the present invention, the coating resin and the core particles are heated and mixed at a temperature not higher than the curing temperature without using a solvent to form a coating layer, and then the baking temperature of the coating resin is higher than the curing temperature. It is heated to a temperature to cure the coating resin and coat the core particles. As a manufacturing device, a heating type kneader, a heating type Henschel mixer, a UM mixer, a planetary mixer, or the like can be used.

The coating resin may be added to the core material after being mixed with the core material at room temperature and then heated to a temperature above the melting start point, or only the core material may be heated to a temperature above the melting point. The particles coated by the above method can be used as a carrier as they are, but further, they may be melt-coated with another resin or may be used as a multi-layer carrier by coating another resin dissolved in a solvent by a solution coating method. It is possible.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner is obtained by dispersing a colorant in a binder resin. Examples of the binder resin used in the toner include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, n (meth) acrylate.
-Propyl, α-methylene aliphatic monocarboxylic acid esters such as lauryl (meth) acrylate and 2-ethylhexyl (meth) acrylate; Vinyl nitriles such as (meth) acrylonitrile; 2-vinylpyridine, 4-vinylpyridine Vinyl pyridines such as vinyl methyl ether, vinyl isobutyl ether and other vinyl ethers; vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone and other vinyl ketones: ethylene, propylene,
Polymers of monomers such as unsaturated hydrocarbons such as isoprene and butadiene and their halides, halogenated unsaturated hydrocarbons such as chloroprene, or copolymers obtained by combining two or more of these monomers Polymers, further mixtures thereof, non-vinyl condensation resins such as rosin-modified phenol formalin resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, or these and the above A mixture with a vinyl resin can be mentioned.

As the colorant used for the toner, carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue,
Mention may be made of methylene blue, rose bengal, phthalocyanine blue or mixtures thereof.

As the toner component other than the colorant, there are a charge control agent, an anti-offset agent, a fluidity improver and the like, and a magnetic fine powder may be contained if necessary. Further, a fluidizing agent such as silica, titania, or alumina, or an external additive such as a cleaning aid or a transfer aid such as polystyrene fine particles, polymethylmethacrylate fine particles, or polyvinylidene fluoride fine particles can be used. In particular, hydrophobic silica having a primary average particle size of 5 to 30 nm is preferably used. As internal additives, charge control agents such as salicylic acid metal salts, metal-containing azo compounds, nigrosine, and quaternary ammonium salts, and other known offset preventing agents such as low molecular weight polypropylene, low molecular weight polyethylene, and wax are known. Ingredients can be added. A low molecular weight polypropylene having a weight average molecular weight of 500 to 5000 is preferable. The smaller the toner particle size, the higher the image quality.
.About.12 .mu.m, preferably about 5 to 10 .mu.m is good.

[0031]

EXAMPLES The present invention will now be described by way of examples, which should not be construed as limiting the invention. In the examples, “part” means part by weight. [Example 1] Cu-Zn ferrite (manufactured by Powdertec Co., average particle size 50 µm) 1000 parts Benzoguanamine / n-butyl alcohol / formaldehyde cocondensate (cocondensation ratio 1: 1: 3) 16 parts Acrylic resin (Mitsui Higashi) Manufactured by Tatsusha, Almatex 748-5M, solid content 55%) 7.3 parts In a 1 L small kneader equipped with a heater, the above materials were mixed at 90 ° C for 30 minutes, and then the heat medium temperature was 250 ° C.
To 40 ° C., the mixture was stirred and kneaded for 40 minutes, then the heater was turned off, and the mixture was cooled for 50 minutes while stirring. Then 105μ
The carrier was obtained by sieving with a m sieve.

Example 2 1000 parts of Cu—Zn ferrite (manufactured by Powdertec Co., average particle size: 50 μm) was heated at a heating medium temperature of 1 in a 1 L small kneader equipped with a heater.
16 parts of benzoguanamine / n-butyl alcohol / formaldehyde co-condensate (co-condensation ratio 1: 1: 3) and polyester resin (Mitsui Toatsu Co., Ltd., Almatex P646, solid content) while raising to 00 ° C. and stirring with heating. 60
%) Was added and the mixture was stirred and kneaded for 40 minutes, then the heating medium temperature was raised to 250 ° 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, it was sieved with a 105 μm sieve to obtain a carrier.

[Example 3] Cu-Zn ferrite (manufactured by Powdertec Co., average particle size 50 µm) 1000 parts Benzoguanamine / n-butyl alcohol / formaldehyde cocondensate (cocondensation ratio 1: 1: 3) 16 parts Acrylic resin (Mitsui Toatsu Co., Ltd., Almatex 748-5M, solid content 55%) 7.3 parts MMA / perfluorooctyl methacrylate copolymer (copolymerization ratio 8: 2) 5 parts Using the above materials, Example 1 and I got a carrier in the same way.

[Example 4] Cu-Zn ferrite (manufactured by Powdertec Co., average particle size: 50 µm) 1000 parts Benzoguanamine / n-butyl alcohol / formaldehyde cocondensate (cocondensation ratio 1: 1: 3) 9 parts Acrylic resin (Mitsui Toatsu Co., Ltd., Almatex 748-5M, solid content 55%) 20 parts Using the above materials, the same treatment as in Example 1 was performed to obtain a carrier.

[Comparative Example 1] 1000 parts of Cu-Zn ferrite (manufactured by Powdertec Co., average particle size: 50 μm) and acrylic resin (manufactured by Mitsui Toatsu Co., Almatex 748-5)
M, solid content 55%) 36.4 parts were used to obtain a carrier in the same manner as in Example 1.

[Comparative Example 2] 1000 parts of Cu-Zn ferrite (manufactured by Powdertec Co., average particle size: 50 μm) and polyester resin (manufactured by Mitsui Toatsu Co., Almatex P64)
6, solid content 60%) was used to obtain a copolymer in the same manner as in Example 2.

Comparative Example 3 Acrylic resin (manufactured by Mitsui Toatsu, Almatex 748-5M, solid content 55%) 11.1 parts Melamine resin (manufactured by Mitsui Toatsu, Uban 20SE60, solid content 55%) 2 .9 parts Benzoguanamine / n-butyl alcohol / formaldehyde co-condensate (co-condensation ratio 1: 1: 3) 1.3 parts Epoxy resin (Ciel Chemical Co., Epicoat 1004) 0.87 parts The above materials are xylene / methanol ( 7: 3) Mixed solvent 5
It was dissolved and dispersed in 00 parts. Then, the above solution and Cu-
Zn ferrite (manufactured by Powder Tech Co., average particle size 50μ)
m) 1000 parts, 1 equipped with a decompression device and a heater
In a small L-kneader, the temperature of the heating medium was raised to 120 ° C., and the solvent was removed while stirring under heating and reduced pressure to obtain a carrier.

Comparative Example 4 Cu-Zn ferrite (manufactured by Powdertec Co., average particle size 50 μm) 1000 parts Benzoguanamine / n-butyl alcohol / formaldehyde cocondensate (cocondensation ratio 1: 1: 3) 4 parts Acrylic resin (Manufactured by Mitsui Toatsu Co., Ltd., Almatex 748-5M, solid content 55%) 29.1 parts The same materials as those in Example 1 were processed to obtain a carrier.

[Toner Production Example 1] Binder resin (styrene-n-butyl methacrylate, copolymerization ratio 70:30) 87 parts Carbon black (manufactured by Cabot Co., BPL) 8 parts Charge control agent (manufactured by Hodogaya Chemical Co., Ltd., TRH) 1 part Polypropylene wax (manufactured by Sanyo Kasei Co., 660P) 4 parts Toner particles having an average particle size of 7.5 μm were obtained by a kneading and pulverizing method using the above materials. Then, 100 parts of the toner particles and colloidal silica (R972 manufactured by Nippon Aerosil Co., Ltd.) 1
Parts were mixed with a Henschel mixer to obtain a toner for evaluation.

(Evaluation) The carriers obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were mixed with the toner obtained in Toner Production Example 1 so as to have a toner concentration of 5% to prepare a developer for evaluation. . About these developers, 50 manufactured by Fuji Xerox Co., Ltd.
An image quality evaluation test was conducted using a No. 39 remodeling machine, and the coated state of the carrier was observed with an electron microscope. The results are shown in Table 1. As is clear from Table 1, the developer of the example is superior in the solid portion density, the background portion stain, and the coated state as compared with the comparative example, and it is understood that the developer has excellent charge stability.

[0041]

[Table 1]

[Example 5] A benzoguanamine / n-butyl alcohol / formaldehyde cocondensate (cocondensation ratio 1: 1: 3) and an acrylic resin were formed on the surface of a developing roll sleeve (stainless steel) for a laser printer 4105 manufactured by Fuji Xerox Co., Ltd. (Mitsui Toatsu Co., Ltd., Almatex 748-
5M, solid content 55%) was mixed so as to have a solid content weight ratio of 8: 2, and was dissolved in a mixed solvent of xylene / methanol (7/3) by dipping to coat 50 g / m ² on the sleeve. Layers were formed. Thereafter, this sleeve was heated and cured at 250 ° C. for 30 minutes in a heating chamber to obtain a charging sleeve.

Comparative Example 5 A developing roll sleeve (made of stainless steel) for a laser printer 4105 manufactured by Fuji Xerox Co., Ltd. was used as it was.

(Production Example 2 of toner) Binder resin (styrene-n-butyl methacrylate, copolymerization ratio 70:30) 44 parts Magnetite powder (EPT-1000 manufactured by Toda Kogyo Co., Ltd.) 50 parts Charge control agent (Hodogaya) 2 parts polypropylene wax (660P, manufactured by Sanyo Kasei Co., Ltd.) 4 parts manufactured by Kagaku Co., Ltd. Toner particles having an average particle size of 9.0 μm were obtained by a kneading and pulverizing method using the above materials. Then, 100 parts of the toner particles and colloidal silica (R972 manufactured by Nippon Aerosil Co., Ltd.)
Toner for evaluation was obtained by mixing 8 parts by a Henschel mixer.

(Evaluation) The sleeves obtained in Example 4 and Comparative Example 4 were used as laser printers 4105 manufactured by Fuji Xerox Co., Ltd.
The image quality evaluation test was performed using the toner of Toner Production Example 2 and the results are shown in Table 2. As is clear from Table 2, the sleeve of Example 4 is superior in image quality stability to Comparative Example 4.

[0046]

[Table 2]

[0047]

According to the present invention, by adopting the above-mentioned constitution, it is possible to greatly improve the charge maintaining property, the environmental stability and the image quality maintaining property of the carrier and the charge imparting member. It has become possible to obtain good image quality without stains on the parts. Further, it has become possible to uniformly and efficiently coat the surface of the core material with the coating resin containing the guanamine resin.

Claims (3)

[Claims] 1. An electrophotographic carrier having a coating layer provided on a core material, the coating layer comprising 40% by weight or more of a guanamine resin and a second resin having a functional group capable of reacting with the guanamine resin. An electrophotographic carrier comprising a thermosetting resin. 2. The resin according to claim 1 and a core substance are heated and mixed at a temperature lower than the curing temperature of the resin to form a coating layer, and then the coating layer is heated to a temperature higher than the curing temperature for curing. A method for manufacturing a carrier for electrophotography, comprising: 3. A charging member for electrophotography, comprising a core material coated with the coating resin according to claim 1.