JPH0318710B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to carriers for developing electrostatic images. In general, 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. When developing a negative latent image, friction between the carrier powder and the toner causes negative charges to be generated on the surface of the carrier and positive charges on the surface of the toner. In general, carriers can be broadly classified into conductive carriers and insulating carriers. Oxidized or unoxidized iron powder is usually used as the conductive carrier, but in a developer containing this iron powder carrier, the amount of triboelectric charge on the toner is unstable, and the visible image formed is unstable. There is a drawback that fog occurs. In other words, when a developer is used, toner particles adhere to the surface of the iron powder carrier particles, which increases the electrical resistance of the carrier particles and lowers the bias current.Furthermore, the triboelectric charging characteristics become unstable, and the visible image The image density decreases, and fog also increases. If a developer containing an iron powder carrier is used for continuous copying, the developer deteriorates after a few times, resulting in a lack of durability, which is not preferable. On the other hand, insulating carriers generally include iron,
A typical example is a carrier in which the surface of carrier core particles made of a ferromagnetic material such as nickel or ferrite is uniformly coated with an insulating resin. In a developer using this insulating carrier, toner particles are less likely to fuse to the surface of the carrier particles than with a conductive carrier, and at the same time, it is easy to control the frictional charging characteristics between the toner and the carrier. , has excellent durability and generally has a long service life. However, when insulating carrier particles come into contact with other carrier particles, toner, the wall of the developing device, or the surface of the photoreceptor multiple times in the developing device, the coating material gradually wears away and the stability of the charging characteristics deteriorates. There is a drawback that the toner particles are gradually lost and cannot be constantly positioned and imparted with a desired charging state to the toner particles. Since the magnitude and polarity of the triboelectric charges generated on toner particles are controlled by the carrier, in order to impart the desired charging state to the toner, the carrier must naturally have charging characteristics corresponding to this. . In order to have this desired charging property, coating films have conventionally been formed using dyes or easily charging resins, but dyes are expensive and lack stability, and resins with excellent charging performance are In addition to being limited to those with a specific structure, they also had the disadvantage of a short service life due to the adhesion to the carrier core material and the relationship with other additives in the developer. SUMMARY OF THE INVENTION The object of the present invention is to provide an electrostatic image carrier having sufficiently long durability, stable triboelectric charging characteristics, and a significantly long service life. Another object of the present invention is to provide a carrier for developing electrostatic images that is inexpensive, easy to manufacture, and has a uniform negative charging voltage. Other objects of the invention will become apparent from the rest of the description. The present invention was completed as a result of intensive research to achieve the above objects. That is, the present invention is a carrier for developing electrostatic images characterized by forming a coating layer on the surface of an inorganic carrier core material using a resin containing a compound of the following general formula [A]. General formula [A] However, X, Y, and Z each represent a halogen atom, a nitro group, a carboxyl group, a carboxyalkyl ether group, a cyano group, a sulfonic acid group, or a dialkylamino group, and X, Y, and Z may be the same or different. Good too. l and n represent integers from 0 to 3, and m represents an integer from 0 to 2. The content of the compound represented by formula [A] in the resin is preferably 0.5 to 15% by weight. Specific examples of what can be used as the compound of the general formula [A] are listed below, but the invention is not limited to these compounds. The above object of the present invention is achieved by using a coating carrier for electrostatic image development in which the surface of carrier core particles is coated with a coating material containing any one of o, m, and p-terphenyl. I discovered that The reason why terphenyl exhibits such a surprising effect is not clear, but one reason is that due to the stacking of benzene rings by terphenyl, the electron accepting property of the carrier of the present invention increases and it has good negative charging characteristics. Therefore, unlike conventional carriers, there is no need to add additives such as dyes for the purpose of charge control, and the resin has very good and stable charge characteristics. It will be done. Furthermore, terphenyl is preferred because it has excellent stability and high durability. Terphenyl is also soluble in most commonly used solvents. Namely, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as methyl acetate and butyl acetate, and halogenated solvents such as chloroform and trichloroethylene. Soluble in hydrocarbon solvents. As mentioned above, since it is soluble in most solvents, it is possible to select and use a low-cost, non-flammable solvent in manufacturing the carrier of the present invention, and it is possible to select and use a solvent that is low in cost and nonflammable, and has no toxicity, explosion limit, or vapor at the manufacturing temperature. It is possible to prevent various accidents such as explosions and pollution during manufacturing due to conditions such as pressure, and furthermore, it has the advantage of being able to freely select a solvent with low compatibility with water that can be easily recovered. There is. In the present invention, the content of terphenyl in the coating layer resin is 0.5 to 15% by weight, preferably 1 to 5% by weight. If the content is less than 0.5% by weight, the effect on charging will be small, and if it is more than 15% by weight, the amount of electrification will be saturated, and the durability of the coating layer will be affected due to the large amount of terphenyl relative to the resin. have a negative impact. In order to produce the carrier for developing an electrostatic image of the present invention, M-(1) A method of coating an inorganic carrier core material with a resin containing terphenyl. M-(2) A method of coating an inorganic carrier core material with a terphenyl-containing monomer and polymerizing the monomer. You can use methods such as Specifically, a solution of terphenyl and coating resin dissolved in a solvent is applied to the treated core material using, for example, a fluidizing bed device and allowed to dry, or a monomer providing the coating resin is similarly applied and the same is applied. All you have to do is to superimpose them. In the present invention, various resins can be used as the coating resin, such as styrenes such as styrene, valachlorstyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic α-methylene aliphatic monocarboxylic acid esters such as 2-ethylhexyl acid, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate; acrylonitrile, methacrylonitrile, etc. vinyl nitriles; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; N-vinyl cyclic compounds such as N-vinyl pyrrolidone; vinyl methyl ketone, vinyl Polymers composed of monomers such as vinyl ketones such as ethyl ketone and methyl isopropenyl ketone; unsaturated hydrocarbons such as propylene, ethylene, isoprene, and putadiene; and halogenated unsaturated hydrocarbons such as chloroprene, or these monomers. Copolymers in which two or more types of polyesters are combined, mixtures thereof, non-vinyl condensation resins such as rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyester resins, polyurethane resins, and polyimide resins, or these and the above-mentioned vinyl resins. Mention may be made of mixtures of. Solvents used in this production include those that are soluble in the resin, such as alcohols such as methanol, ethanol, butanol and isopropanol, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, Other organic solvents such as tetrahydrofuran and dioxane, or mixed solvents thereof may be used. The carrier of the present invention produced by the method described above usually has a concentration of 0.1 on the surface of the carrier core particles.
Coated with a thickness of ~30 microns, preferably 0.2-20 microns. Furthermore, the glass transition temperature of the coating resin is at least
The temperature is preferably 60°C or higher. 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. Deteriorate. In the present invention, the particle size of the carrier core material is
Conventional carrier cores of 20 to 1000 microns, preferably 30 to 200 microns, such as sand, glass, or metals such as cobalt, iron, copper, nickel, ferrite, zinc, aluminum, brass, or their alloys or oxides thereof. Although materials used as materials can be used, in reality, they are appropriately selected according to the developing method employed. This carrier core material is preferably spherical. 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,
α such as lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.
-Methylene aliphatic monocarboxylic acid esters; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone , vinyl ethyl ketone, methyl isopropenyl ketone; unsaturated hydrocarbons such as ethylene, propylene, isoprene, butadiene, and their halides; polymers of monomers such as halogen-based unsaturated hydrocarbons such as chloroprene; Alternatively, copolymers obtained by combining two or more of these monomers, mixtures thereof, or, for example, rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyester resins, polyurethane resins, polyimide resins, cellulose resins, polyester resins, etc. Examples include non-vinyl condensation resins such as ether resins, and mixtures of these and the above-mentioned 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 the 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 over a long period of 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 m-terphenyl (exemplified compound A-2) 0.45g
and styrene:methyl methacrylate = 70:30 styrene-methyl methacrylate = 70:30 styrene-methacrylate copolymer (15 g) toluene 500
ml of the solution was sprayed onto 1 kg of iron powder with an average particle size of 100 microns using a fluidizing bed device and dried at a temperature of 70°C to form a coating layer with a thickness of 1 to 2 microns. A carrier of the present invention was constructed having the following characteristics. The obtained carrier was non-sticky and free of agglomerates and had good fluidity. Example 2 m-terphenyl (exemplified compound A-2) 0.75g
and 15 g of styrene-methyl methacrylate copolymer (composition ratio 7:3) were dissolved in 500 ml of toluene,
Spray on 1 kg of iron powder with an average particle size of 100 microns,
A carrier of the present invention was obtained. Example 3 o-terphenyl (exemplified compound A-3) 0.45g
A carrier was prepared in the same manner as in Example 1, except that a carrier was used. Example 4 O-terphenyl (exemplified compound A-
3) Dissolve 3g of lauroyl peroxide as a polymerization initiator, mix with 1kg of spherical iron powder with an average particle size of 100 microns, stir for about 30 minutes, let stand, and separate the supernatant liquid. , an aqueous solution containing 1.5 g of colloidal calcium phosphate as a dispersant.
Polymerization was carried out at a temperature of 75° C. for 8 hours while thoroughly dispersing the mixture in 500 ml of water. Thereafter, the system was cooled, 2 ml of concentrated hydrochloric acid was added, and after stirring for 10 minutes, the solid matter was taken out and thoroughly washed with water to obtain the carrier of the present invention. Example 5 p-terphenyl (exemplified compound A-1) 0.45g
A carrier was prepared in the same manner as in Example 1 except that a carrier was used. Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that styrene-methyl methacrylate (70:30) copolymer was used instead of m-terphenyl. Comparative Example 2 A sample was prepared in the same manner as in Example 1, except that a styrene-methyl methacrylate (30:70) copolymer was used instead of a terphenyl compound. Comparative Example 3 A sample was prepared in the same manner as in Example 1, except that a styrene-methyl methacrylate (90:10) copolymer was used instead of a terphenyl compound. Comparative Example 4 A sample was prepared in the same manner as in Example 1, except that the terphenyl compound was not used and polystyrene was used instead of the styrene-methyl methacrylate copolymer. As described above, the carriers obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were combined with 100 parts of styrene-acrylic resin,
A developer is prepared by mixing toner with an average particle size of approximately 10 microns consisting of 10 parts of carbon black, and the mixture is idly stirred 100 times in a developing device to be triboelectrically charged.
The toner charge amount was measured by a known blow-off method. Furthermore, after performing an image test using these developers 20,000 times using Ubitx-2000R (manufactured by Konishiroku Photo Industry Co., Ltd.), the amount of charge was also measured. The results are shown in the table below.

[Table] In Comparative Examples 3 and 4, the coating layer was brittle due to the large amount of styrene, and the film peeled off after 20,000 copies. When the developer of Examples 1 to 4 was similarly subjected to an image test 20,000 times under a high temperature and high humidity atmosphere of 50 DEG C. and 80% relative humidity, good copied images could be obtained.

Claims (1)

[Scope of Claims] 1. A carrier for developing electrostatic images, characterized in that a coating layer is formed on the surface of an inorganic carrier core material using a resin containing a compound of the following general formula [A]. General formula [A] X, Y, and Z each represent a halogen atom, a nitro group, a carboxyl group, a carboxyalkyl ether group, a cyano group, a sulfonic acid group, or a dialkylamino group, and X, Y, and Z may be the same or different. good. l and n represent integers from 0 to 3, and m represents an integer from 0 to 2. 2. The carrier for developing electrostatic images according to claim 1, characterized in that a coating layer is formed on the surface of an inorganic carrier core material using a resin containing 0.5 to 15% by weight of the compound.