JPH0414346B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a carrier for developing electrostatic images. Generally, in electrophotography, electrostatic recording, etc., toner, which is a colored fine powder, and carrier are used to develop an electrostatic image formed on an image support made of a photoconductive photoreceptor or dielectric material. The following developer is used. The toner that makes up this developer is
During the conveyance process, the toner rubs against the carrier and a charge of the opposite polarity to that of the electrostatic charge image is induced in the toner, and during the development process by the developer, the toner electrostatically adheres to the image support and forms a visible image. is formed. Therefore, the toner in the developer in the developing device is consumed each time development is performed, but the developing device is replenished with new toner accordingly, so that the toner in the developing device is constantly renewed. However, the carrier, which is initially prepared, is used repeatedly over a long period of time, and as a result, the characteristics of the carrier deteriorate as development is repeated. For example, a portion of the toner may become fused to the carrier surface, resulting in so-called spent toner, which may reduce the triboelectric charging properties of the carrier, or may reduce the desired effect in image quality adjustment performed by applying a bias voltage to the developer. Therefore, good development cannot be achieved. Furthermore, inorganic powder or granules are generally used as they are as carriers, but if their surface conditions are hydrophilic, the moisture resistance of the developer decreases, making it impossible to achieve good development. As a means to solve the above problems,
For example, it is possible to use inorganic particles as a carrier core material and form a coating layer made of a resin with excellent triboelectric properties with toner on its surface.
This is disclosed in JP-A No. 27879, Japanese Patent Application Laid-Open No. 13954-1984, and the like. According to the so-called coating carrier having such a resin coating layer, deterioration of the characteristics of the developer due to spent toner adhering to the carrier surface can be suppressed to some extent. However, developers using conventional resin-coated carriers have the disadvantage that during the process of flowing in the developing device, they collide with the container wall, causing the resin coating layer to be missing from the carrier surface, resulting in deterioration of the carrier's performance. . Therefore, as described in JP-A-55-33109, for example, a layer of a silane coupling agent such as alkyltrialkoxysilane and tetraalkoxysilane is provided on the surface of the magnetic material in advance, and a resin coating layer is further provided on the surface of the magnetic material. There are also attempts. However, with this method, the silane coupling agent is highly hydrolyzable, resulting in reduced moisture resistance and durability, and the low reactivity of the silane coupling agent to magnetic materials reduces the coating strength of the coating layer. Furthermore, there is a drawback that it is difficult to control the charge polarity. As described above, the reality is that no carrier that is fully satisfactory for practical use has been found at present. The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a resin coating layer that does not cause toner adhesion and has little deterioration in characteristics. It is an object of the present invention to provide a carrier for developing electrostatic images that is firmly bonded to an inorganic carrier core material, exhibits little deterioration in characteristics even after long-term use, and is capable of achieving good development. Another object of the present invention is to provide a carrier for developing electrostatic images that has excellent moisture resistance and allows easy control of charging polarity. The above-mentioned object is achieved by forming a coating layer of a compound represented by the following general formula and a resin on the surface of a carrier core material to form a carrier for developing an electrostatic image. general formula Here, R ₁ : Hydrogen atom, substituted/unsubstituted alkyl group, or substituted/unsubstituted alkenyl group R ₂ : Substituted/unsubstituted alkyl group or substituted/unsubstituted alkenyl having 9 to 17 carbon atoms. It is the basis. In order to produce the carrier for developing electrostatic images of the present invention, (1) a method of treating an inorganic carrier core material with a compound represented by the above general formula (hereinafter referred to as "compound") and then applying a resin coating layer. (2) A method of coating an inorganic carrier core material with a resin containing the above compound. (3) It is possible to use a method such as coating an inorganic carrier core material with a monomer containing the above compound and polymerizing the monomer. To explain in detail, in the case of method (1), a carrier core material is treated with the above-mentioned compound to obtain a treated core material, and a solution in which a coating resin is dissolved in a solvent is applied to the treated core material using, for example, a fluidizing bed device. It can be applied to the material and allowed to dry, or it can be similarly applied with a monomer that provides a coating resin and polymerized. Also in the case of methods (2) and (3), known means can be used as the coating means. According to method (1), as schematically shown in FIG. 1, the coating layer 2 formed on the outer surface of the carrier core material 1 includes the compound layer 2A and the resin layer
It is made of a laminate with B and has particularly excellent moisture resistance and durability. According to method (2) or method (3), as shown in FIG. 2, the coating layer 2 is made of a resin containing the above compound, which has the advantage of being particularly easy to manufacture. In the present invention, the carrier core material has a particle size of 30
~1000 microns, preferably 30-200 microns, such as sand, glass, or cobalt, iron, copper, nickel, ferrite, zinc, aluminum, brass,
Metals such as metals, alloys thereof, or oxides thereof, which are conventionally used as carrier core materials, can be used, but in reality, they are appropriately selected according to the developing method employed. This carrier core material is preferably spherical. Specific examples of compounds used in the present invention include, for example, the following. Exemplary compound Product: "Nitsukor MGK" (manufactured by Nikko Chemicals) Product: "Nitsukor MGK" (manufactured by Nikko Chemicals) Products: “Nitsukor MGS-A” “Nitsukor
MGS-B” and “Nitsukor MGS-C” (all manufactured by Nikko Chemicals) Product: "Nitsukor MGO" (manufactured by Nikko Chemicals) Product: "Nitsukol MGIS" (manufactured by Nikko Chemicals) (8) Glycerin castor oil fatty acid ester Product: "Nitsukol MGCO" (manufactured by Nikko Chemicals) (9) Glycerin hydrogenated castor oil fatty acid ester Product: "Nitsukol MGHCO" (Nikko Chemicals) company) Product: "Nitsukor DGMS" (manufactured by Nikko Chemicals) Product: “Nitsukol DGMO” (manufactured by Nikko Chemicals) (12) Glycerin castor oil fatty acid ester Product: “Nitsukol MGL-C” (manufactured by Nikko Chemicals) Product: "Nitsukol A-1070" (manufactured by Nikko Chemicals Co., Ltd.) Various resins can be used as the coating resin in the present invention, such as styrenes such as styrene, parachlorostyrene, and α-methylstyrene; acrylic; α- Methyl acrylate, ethyl acrylate, n-propyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, etc. Methylene aliphatic monocarboxylic acid esters; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine; N-pinyl N-vinyl cyclic compounds such as pyrrolidone; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; unsaturated hydrocarbons such as propylene, ethylene, isoprene, and butadiene; halogen-based unsaturated carbons such as chloroprene Polymers made of monomers such as hydrogen, copolymers of two or more of these monomers, and mixtures thereof, such as rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyester resins, polyurethane resins, polyimide resins, etc. Non-vinyl condensation resins or mixtures of these and the above-mentioned vinyl resins can be mentioned. The amount of coating of the compound and the coating resin must be within an appropriate range; if the amount of coating of the compound is too large, the compound will precipitate, resulting in poor adhesion of the coating layer to the carrier core material. becomes small, and the fluidity as a developer decreases, resulting in poor conveyance. The preferred coating amount is such that the compound is in the range of 0.01 to 5% by weight and the coating resin is in the range of 0.1 to 10% by weight based on the total amount of the carrier. Further, two or more of the above compounds may be used in combination. Furthermore, the glass transition temperature of the coating resin is at least
The temperature is preferably 60°C. If the glass transition temperature is low, the resin will become sticky when heat is generated due to friction between the carriers or between the carrier and the wall of the developing device, resulting in poor fluidity. Become. In addition, the carrier of the present invention has the following characteristics for the toner used together with the carrier:
It is preferable that it provides a charge of 5 to 40 microcoulombs/g in absolute value under normal usage conditions. The toner constituting the developer together with the carrier of the present invention is made by dispersing a colorant in a resin, and various thermoplastic resins are used as the binder resin. Specific examples include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate;
Ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate,
α- such as n-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.
Methylene aliphatic monocarboxylic acid esters; Vinyl nitriles such as acrylonitrile and methacrylonitrile; Vinyl pyridines such as 2-vinylpyridine and 4-vinylpyridine; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl methyl ketone, vinyl Vinyl ketones such as ethyl ketone and methyl isopropenyl ketone; unsaturated hydrocarbons such as ethylene, propylene, isoprene, butadiene and their halides; polymers of monomers such as halogenated unsaturated hydrocarbons such as chloroprene; , a copolymer obtained by combining two or more of these monomers, and a mixture thereof, or
Examples include non-vinyl condensation resins such as rosin-modified phenol formalin resin, oil-modified epoxy resin, polyester resin, polyurethane resin, polyimide resin, cellulose resin, and polyether resin, or mixtures of these and the vinyl resins. Further, as specific examples of the colorant, for example,
carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow,
Mention may be made of ultramarine blue, methylene blue, rose bengal, phthalocyanine blue or mixtures thereof. Since the carrier for developing electrostatic images of the present invention is as described above, the inorganic carrier core material is covered with a coating layer made of the above-mentioned compound and resin. , the coating layer firmly adheres to the carrier core material and does not come off, and does not cause toner adhesion, so it has great durability, maintains its excellent properties for a long time, and is generally Good electrostatic image development can be achieved. Of course, various additives such as charge polarity control agents and the like can be added to the carrier of the present invention as required. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. Example 1 Iron powder with an average particle size of 100 microns was used as a carrier core material, and a solution of 110 g of the exemplified compound dissolved in 400 ml of toluene was added to 1 kg of the iron powder, stirred for 3 hours, and solids were filtered off and dried. A treated core material was obtained. This treated core material is used in a scanning electron microscope "JSH-T200"
(manufactured by JEOL Ltd.) when observed at 3500x magnification.
It was found that a uniform and good film was formed. To this treated core material, 70 g of methyl methacrylate and 30 g of sterene were mixed, and a solution containing 2.5 g of lauroyl peroxide as a polymerization initiator was added, stirred for about 30 minutes, and left to stand to separate the supernatant liquid. 500 ml of an aqueous solution containing 1.5 g of colloidal calcium phosphate as a dispersion stabilizer was added, and polymerization was carried out at a temperature of 75° C. for 8 hours while thoroughly dispersing the mixture.
Thereafter, the system was cooled, 2 ml of concentrated hydrochloric acid was added, and after stirring for 10 minutes, the solid material was taken out and thoroughly washed with water to obtain a carrier of the present invention. This will be referred to as "Sample 1". Example 2 1 kg of the same treated core material as in Example 1 was mixed with methyl methacrylate:styrene = 70:30 by weight
Methyl methacrylate-styrene copolymer 15g
The carrier of the present invention was obtained by treating with a solution prepared by dissolving the above in 500 ml of toluene using a fluidizing bed apparatus. This will be referred to as "Sample 2." Example 3 Using a solution in which 15 g of the exemplified compound and 15 g of methyl methacrylate-styrene copolymer with a weight ratio of methyl methacrylate:styrene = 70:30 were dissolved in 500 ml of toluene, 1 kg of iron powder with an average particle size of 100 microns was fluidized. The carrier of the present invention was obtained by processing with a chemical bed equipment. This will be referred to as "Sample 3." Example 4 Using a solution prepared by dissolving 15 g of the exemplary compound in 300 ml of toluene, 1 kg of iron having an average particle size of 100 microns was treated in a fluidizing bed apparatus to obtain a treated core material. Methyl methacrylate weight ratio of treated heartwood:
A carrier of the present invention was obtained by treating with a solution of 15 g of methyl methacrylate styrene copolymer of 70:30 styrene dissolved in 500 ml of toluene. This will be referred to as "Sample 4." Example 5 A carrier of the present invention was obtained in the same manner as in Example 1 except that Exemplified Compound 2 was used in place of Exemplified Compound 1 in Example 1. This will be referred to as "Sample 5." Example 6 A carrier of the present invention was obtained in the same manner as in Example 2 except that Exemplified Compound 2 was used in place of Exemplified Compound 1 in Example 2. This will be referred to as "Sample 6". Example 7 A carrier of the present invention was obtained in the same manner as in Example 3 except that Exemplified Compound 2 was used in place of Exemplified Compound 1 in Example 3. This will be referred to as "Sample 7." Example 8 A carrier of the present invention was obtained in the same manner as in Example 4 except that Exemplified Compound 2 was used in place of Exemplified Compound 1 in Example 4. This will be referred to as "Sample 8." Example 9 A carrier of the present invention was obtained in the same manner as in Example 1 except that "Nitsukor MGK" (manufactured by Nikko Chemicals) (Exemplary Compound 3) was used in place of Exemplified Compound 1 in Example 1. This will be referred to as "Sample 9." Example 10 A carrier of the present invention was obtained in the same manner as in Example 2 except that "Nitsukor MGK" was used in place of Exemplified Compound 1 in Example 2. This is called “Sample 10”
shall be. Example 11 A carrier of the present invention was obtained in the same manner as in Example 3 except that "Nitsukor MGK" was used in place of Exemplified Compound 1 in Example 3. This will be referred to as "Sample 11." Example 12 A carrier of the present invention was obtained in the same manner as in Example 4 except that "Nitsukor MGK" was used in place of Exemplified Compound 1 in Example 4. This will be referred to as "Sample 12." Samples 1 to 12 obtained in Examples 1 to 12 above
Toner for the electrophotographic copying machine "U-Bix3000" was added to each of these to make a total of 12 types of developer with a toner concentration of 3%, and the developer was shaken for several minutes to become triboelectrically charged, and then subjected to a known blow-off process. A charge amount test was conducted using the method. The results are shown in Table 1.

[Table] Furthermore, when we conducted a photocopying test using each of the above developers using an electrophotographic copying machine "U-Bix3000" (manufactured by Konishiroku Photo Industries Co., Ltd.), the results were good with no fogging up to 100,000 copies. A copy image was obtained. After 100,000 copies, each developer was tested again for the amount of charge. The results are shown in Table 2.

【table】

[Table] Using each of the above developers, we conducted similar photocopying tests in a high temperature, high humidity atmosphere with a temperature of 50°C and a relative humidity of 80%, and good copy images were obtained up to 100,000 copies. I was able to do that. Comparative Example 1 A carrier was obtained in exactly the same manner as in Example 2, except that the treatment with Exemplary Compound 1 was not performed. This will be referred to as "comparative sample 1." A developer was prepared using Comparative Sample 1 in the same manner as described above, and the same charge amount test was conducted, and the charge amount was -17.5 microcoulombs/g.
When a similar photocopying test was conducted using the above developer, fog-free copied images were obtained up to 50,000 copies, but after that, fog occurred and the image quality deteriorated. Furthermore, after 100,000 copies, a charge amount test was conducted and the charge amount was -10 microcoulombs/g.
It was hot. Comparative Example 2 A carrier was obtained in exactly the same manner as in Example 1 except that vinyltriethoxysilane was used in place of Exemplified Compound 1 in Example 1. This will be referred to as "comparative sample 2." A similar developer was made using this comparative sample 2,
When a similar photo-copying test was conducted in a high-temperature, high-humidity atmosphere with a temperature of 50°C and a relative humidity of 80%, the image quality of the copied images deteriorated significantly after 20,000 copies were made. Example 13 A carrier of the present invention was obtained in the same manner as in Example 2 except that a styrene-vinylidene chloride copolymer was used as the coating resin. This will be referred to as "Sample 13." Example 14 A carrier of the present invention was obtained in the same manner as in Example 6 except that a styrene-vinylidene chloride copolymer was used as the coating resin. This will be referred to as "Sample 14." Example 15 A carrier of the present invention was obtained in the same manner as in Example 10, except that a styrene-vinylidene chloride copolymer was used as the coating resin. This will be referred to as "Sample 15." Comparative Example 3 A carrier was obtained in the same manner as in Example 2, except that tetra-n-butoxytitanium was used in place of Exemplified Compound 1 in Example 2, and styrene-vinylidene chloride copolymer was used as the coating resin. This will be referred to as "comparative sample 3." When the three samples 13 to 15 and comparative sample 3 were stored for one month in a high temperature and high humidity atmosphere with a temperature of 50 ° C. and a relative humidity of 80%, no changes were observed in samples 13 to 15. 10 in the live-action test
Even after 10,000 copies, images of good quality were obtained. On the other hand, in comparative sample 3, aggregation occurred after storage. Even when a resin containing a halogen atom is used as the coating resin, the carrier of the present invention has excellent properties. Comparative Example 4 A carrier was obtained in the same manner as in Example 1 except that polyoxyethylene laurate was used instead of Exemplary Compound 1. In addition, when the surface of the treated core material in this step was observed using a scanning electron microscope, non-uniform portions were observed in the formed film. The carrier obtained here was equipped with an electrophotographic copying machine "U".
-Toner concentration is 3 by adding toner for ``Bix3000''
% developer was prepared. Using this developer, a photocopying test was conducted using an electrophotographic copying machine "U-Bix3000", and the amount of charge of the developer was measured at the initial stage and after 100,000 copies. The results are as follows. Initial stage: -18.0 microcoulombs/g After 100,000 copies: -12.6 microcoulombs/g Fog occurred after 80,000 copies.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory cross-sectional views schematically showing the structure of particles of the carrier for developing electrostatic images of the present invention. 1... Inorganic carrier core material, 2... Covering layer, 2
A...Compound layer, 2B...Resin layer.

Claims (1)

[Scope of Claims] 1. A carrier for developing electrostatic images, characterized in that a coating layer made of a compound represented by the following general formula and a resin is formed on the surface of a carrier core material. general formula Here, R ₁ : Hydrogen atom, substituted/unsubstituted alkyl group, or substituted/unsubstituted alkenyl group R ₂ : Substituted/unsubstituted alkyl group or substituted/unsubstituted alkenyl having 9 to 17 carbon atoms. It is the basis. 2 The ratio of the compound represented by the general formula in the coating layer to the carrier core material is 0.01.
5% by weight of the carrier for developing electrostatic images according to claim 1.