JPH05173371A - Electrostatic charge image developing carrier and its production - Google Patents

Abstract

PURPOSE:To provide an electrostatic charge image developing carrier and its production method so that peeling or chipping of surface layers of the electrostatic charge image developing carrier is prevented, deterioration of electrification characteristics due to deposition of the toner component is improved, good picture quality is maintained against environmental changes, and proper electrification level is controlled. CONSTITUTION:This electrostatic charge image developing carrier consists of core particles covered with a coating resin containing a methylphenyl silicone polymer. This polymer has >=50 deg.C softening point and 0.6-3.0 absorbance ratio of methyl groups to phenyl groups measured by an IR spectro photometer. This carrier is produced by mixing the coating resin and core particles in a dry state and heating to melt the resin to coat the core particles.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A method of visualizing image information through an electrostatic latent image such as electrophotography is currently used in various fields. In the electrophotographic method, an electrostatic latent image formed on a photoconductor by a charging and exposing process is developed with a developer containing toner, and then visualized through a transferring and fixing process. Developers used for development include 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. In the two-component developer, the carrier is a stirring agent of the developer. -Since the functions such as transport and charging are shared and the functions are separated as a developer, it has the characteristics of good controllability and is currently widely used. In particular, a developer using a carrier coated with a resin has excellent charge controllability, and it is relatively easy to improve environmental dependency and stability over time.

Further, as a developing method, a cascade method or the like has been used for a long time, but nowadays, a magnetic brush method using a magnetic roll as a developer transporting unit is mainly used. In the magnetic brush development method using a two-component developer, the image density is lowered due to the charge deterioration of the developer, the background is markedly stained, the image is roughened due to the carrier attached to the image, and the carrier is consumed. There is a problem such as occurrence of uneven image density.

The cause of the charge deterioration of the developer is often caused by peeling or peeling of the carrier charge control layer, or contamination of the carrier surface by the toner component. The mechanism of carrier adhesion to the image is that the resistance of the carrier decreases
Injected charge is injected into the image area to attach carriers,
It is considered that, because the upper limit control of the charge amount of the carrier is insufficient, the charge amount of the carrier after development becomes excessive and the carrier adheres to the edge portion.

The present invention is intended to provide a carrier for developing an electrostatic charge image and a method for producing the same, in which the above problems are solved, and the objects thereof are as follows. To prevent the surface layer of the carrier for developing an electrostatic image from being peeled off or overlaid, and to improve the deterioration of charge retention due to the adhesion of toner components. To improve the image maintainability due to the change in charging property due to environmental changes. Stable image quality is obtained by suppressing carrier adhesion and carrier consumption by the developer controlled to an appropriate charge level.

[0006]

The present invention has a softening point of 50 ° C. or higher, and the absorbance by an infrared spectrophotometer is in the range of 0.6 to 3.0 in terms of the ratio of methyl group to phenyl group. A coating resin containing a methylphenyl silicone polymer,
Carrier for electrostatic image development characterized by coating core particles, and, after mixing the coating resin and the core particles in a dry state, heated to melt the coating resin, the core A method for producing a carrier for developing an electrostatic charge image, which comprises coating particles.

[0007]

In the resin coating on the magnetic core particles, it is important to ensure the adhesion between the resin and the core particles and the uniformity of the coating. When the adhesiveness is poor, it is easily peeled off due to mechanical stress, and toner contamination easily occurs on the exposed portion of the core particles. In addition, when the uniformity of the resin coating is lost or when the core particles are exposed from the beginning, not only toner contamination but also charge injection carrier adhesion due to a decrease in electrical resistance occurs, and temperature, humidity, etc. The change in the environment causes a large change in the charging property. In particular, when a carrier is produced by a resin coating method that does not use a solvent, it is difficult to sufficiently adapt the core particles and the resin,
Improvement was needed. On the other hand, a silicone resin having a softening point in the range of about 50 to 150 ° C. can form a relatively uniform film on the surface of the core particles by the coating method using a solvent or the coating method using no solvent. The properties of the coating largely depend on the component ratio of the monomer. Here, the silicone resin is composed of a monomer represented by the following formula,
Usually, it is synthesized by hydrolysis of a mixture of dimethyldichlorosilane, methylphenyldichlorosilane, diphenyldichlorosilane and the like, and the ratio of the methyl group and the phenyl group is controlled by the mixing ratio thereof.

[0008]

[Chemical 1]

The present inventors have found that this ratio greatly affects the properties of the carrier coating. That is, when the amount of methyl groups is extremely small, the coating layer becomes brittle, and chipping or peeling easily occurs, and electrical resistance and charge controllability become unstable, resulting in lack of charge retention. Further, when the phenyl group is extremely small, the softening point is remarkably lowered, and the adhesion of the toner becomes remarkable because the adhesiveness at room temperature increases.
The carrier deteriorates, resulting in a decrease in charge amount and a decrease in developer fluidity. Therefore, the inventors of the present invention have made an earnest study on the assumption that the methylphenyl silicone resin as a carrier coating material has an optimum range of the ratio of methyl groups to phenyl groups, and as a result, carbon tetrachloride and the like do not affect the background. A methylphenyl silicone resin sample was dissolved in a solvent at 5% by weight, and the ratio of the methyl group and the phenyl group in the solution state was measured at a specific wavelength of the infrared spectrophotometer (the methyl group is
250 cm ^-1, the phenyl group by measuring absorbance at 1440cm ^-1), when expressed as a ratio of the absorbance, the ratio (a phenyl group absorbance / methyl absorbance) is 0.6
It has been found that the range of 3.0 is preferable, and the range of 0.8 to 2.5 is particularly preferable. When a silicone polymer having a ratio of less than 0.6 and a softening point of 50 ° C. or higher is used,
Crosslinking is likely to proceed due to the residual OH groups, and it is difficult to obtain a uniform coat by the heat fusion coating method, and peeling easily occurs. Further, when the above ratio is 0.6 or more and the softening point is 50 ° C.
If a silicone polymer of less than 1 is used, the polymerization tends to be insufficient, a large number of low molecular weight polymers are contained, and carrier aggregation is likely to occur during production or after coating.

As the carrier coating resin, this methylphenyl silicone resin can be used alone or in combination with other resins. As the combined coating resin used in the present invention, a resin that has been generally used conventionally can be used. For example, a fluorine-containing resin is mainly used for a negative charging carrier, and an acrylic resin is used as a positive charging carrier. Based resins are mainly used. Examples of the fluorine-containing resin include vinylidene fluoride,
Examples thereof include homopolymers or copolymers of vinyl-based fluorine-containing monomers such as tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethylene, monofluoroethylene and trifluoroethylene. In addition, examples of other resins include styrenes such as styrene, chlorostyrene, and methylstyrene; methyl methacrylate, methyl acrylate, propyl acrylate, lauryl acrylate, lauryl methacrylate,
Methacrylic acid, acrylic acid, butyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate,
Α-Methylene aliphatic monocarboxylic acids such as ethylmethacrylate; nitriles such as acrylonitrile and methacrylonitrile; vinylpyridines such as 2-vinylpyridine and 4-vinylpyridine; vinyl ethers; vinyl ketones; ethylene, propylene, butadiene, etc. It is possible to use homopolymers such as olefins, or copolymers thereof. It is also possible to use polyesters containing bisphenol, glycol and the like.
The coating amount of the coating resin is about 0.3 to 10% by weight, preferably 0.5 to 3% by weight, based on the total amount of the resin alone or in combination with the carrier.

The core particles used in the present invention are iron,
Magnetic metal powder such as nickel, iron oxide powder, ferrite particles,
Inorganic oxide powder such as granulated magnetite can be used. The average particle size is usually about 20 to 200 μm. The method for producing the carrier of the present invention includes a heating type kneader, a heating type Henschel mixer, and a heating type UV.
Using a mixer or the like, a heating type fluidized rolling bed, a heating type kiln or the like can also be used depending on the compounding ratio such as the amount of resin.

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, and the binder resin used in the toner includes styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate. , Α-methylene aliphatic monocarboxylic acids such as n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate Esters; Vinyl nitriles such as acrylonitrile and methacrylonitrile; Vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl methyl ketone, vinyl ethyl ketone, vinyl isopro Vinyl ketones such as penyl ketone; ethylene, propylene,
Unsaturated hydrocarbons such as isoprene and butadiene, and halides thereof, polymers of halogenated unsaturated hydrocarbons such as chloroprene, and the like, or copolymers obtained by combining two or more of these monomers , And mixtures thereof, and further 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 a mixture of these with the vinyl resin. Can be mentioned.

Examples of the colorant used in the toner include carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, and 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.

[0014]

【Example】

[Example 1] (Manufacture of carrier) Core particles: spherical ferrite (manufactured by Powder Tech Co., Ltd .: average particle size 80 µm) 100 parts by weight Coating resin: vinylidene fluoride-tetrafluoroethylene copolymer (manufactured by Penwald Co., Ltd .: Kynar) 7201) 1.0 part by weight Methylphenyl silicone resin (Toray Dow Co .: phenyl / methyl ratio 1.03, DSC softening point 64 ° C.) 0.5 part by weight The materials having the above composition were mixed with an Irie Shokai 5L kneader. After that, the temperature was raised to 200 ° C. in 30 minutes, and then the heating was stopped and the mixture was cooled for 50 minutes while stirring in a fume hood. The sample was sieved with a 144 μm sieve and a 44 μm sieve to obtain a carrier having an average particle size of about 80 μm. This carrier was mixed with the following toner in a V blender at a toner weight concentration of 5% to obtain a developer. (Production of toner) Styrene-n-butyl methacrylate resin 88% by weight Nigrosine (Bontron N04 manufactured by Hodogaya Chemical Co., Ltd.) 2% by weight Carbon black (BPL manufactured by Cabot Co., Ltd.) 6% by weight Polypropylene wax (660P manufactured by Sanyo Kasei Co., Ltd.) 4% by weight The above materials were kneaded with a Banbury mixer, finely pulverized, and classified to obtain a toner having an average particle size of 11μ. (Image quality maintenance test) An image quality maintenance test was conducted on the above developer using a modified FX5030 machine manufactured by Fuji Xerox Co., Ltd., and the initial good image quality was maintained even after the continuous copying of 150,000 sheets. Further, no carrier adhesion was observed.

Comparative Example 1 Instead of the methylphenyl silicone resin of Example 1, a methylphenyl silicone resin (manufactured by Toray Dow: Phenyl / methyl ratio 3.2, DSC) was used.
A softening point of 82 ° C.) was used, and the other conditions were the same as in Example 1 to obtain a carrier, and the toner of Example 1 was used to obtain a developer in the same manner. When an image quality maintenance test was conducted on this developer with a modified machine of FX5030 manufactured by Fuji Xerox Co., the initial image quality was a little low, and after the 100,000-sheet continuous copying was completed, the amount of the developer decreased due to the adhesion of the carrier. Remarkably, density unevenness partially occurred on the image.

[Example 2] Instead of the methylphenyl silicone resin of Example 1, a methylphenyl silicone resin (manufactured by Toray Dow: Phenyl / methyl ratio 2.4, DSC) was used.
A softening point of 78 ° C.) was used, and the other conditions were the same as in Example 1 to obtain a carrier, and the toner of Example 1 was used to obtain a developer in the same manner. When this developer was subjected to an image quality maintenance test with a modified machine of FX5030 manufactured by Fuji Xerox Co., Ltd., the initial good image quality was maintained even after the continuous copying of 150,000 sheets. Further, no carrier adhesion was observed.

[Example 3] (Production of carrier) Core particles: Spherical ferrite (manufactured by Powder Tech Co., Ltd .: average particle size 80 µm) 100 parts by weight Coating resin: Styrene-methyl methacrylate copolymer (manufactured by Mitsubishi Rayon Co., Ltd.) 1 0.0 parts by weight Methylphenyl silicone resin (manufactured by Toray Dow: phenyl / methyl ratio 1.03, DSC softening point 64 ° C.) 0.5 parts by weight After mixing the materials having the above composition with a 5L kneader manufactured by Irie Shokai, 30 The temperature was raised to 200 ° C. in minutes, and then the heating was stopped and the contents were cooled for 50 minutes while stirring in a fume hood. The sample was sieved with a 144 μm sieve and a 44 μm sieve to obtain a carrier having an average particle size of about 80 μm. This carrier was mixed with the following toner in a V blender at a toner weight concentration of 5% to obtain a developer. (Manufacture of toner) Styrene-n-butyl methacrylate resin 88% by weight Nigrosine (TRH manufactured by Hodogaya Chemical Co., Ltd.) 2% by weight Carbon black (BPL manufactured by Cabot Co., Ltd.) 6% by weight Polypropylene wax (330P manufactured by Sanyo Kasei Co., Ltd.) 4% by weight or more The above material was kneaded with a Banbury mixer, then finely pulverized and classified to obtain a toner having an average particle size of 10 μm. (Image quality maintenance test) This developer is F manufactured by Fuji Xerox Co., Ltd.
When the image quality maintenance test was conducted with the modified X5030 machine,
Even after the continuous copying of 150,000 sheets was completed, the initial good image quality was maintained.

Comparative Example A methylphenyl silicone resin (manufactured by Toray Dow: phenyl / methyl ratio 0.5, DSC softening point 42 ° C.) was used in place of the methylphenyl silicone resin of Example 1 under other conditions. A carrier was obtained in the same manner as in Example 1, and a developer was obtained in the same manner using the toner of Example 1. When the amount of charge of this developer was measured by a Toshiba blow-off charge amount measuring device, the amount of charge was extremely low and the fluidity as a developer was poor, so an image quality maintenance test could not be reached.

[0019]

According to the present invention, by adopting the above-mentioned constitution, it is possible to prevent the surface layer of the carrier for developing an electrostatic image from being peeled off or broken. The image quality can be improved, and good image quality can be stably maintained against environmental changes.

Claims (2)

[Claims] 1. A softening point of 50 ° C. or higher, and an absorbance measured by an infrared spectrophotometer is a ratio of methyl group to phenyl group of 0.
A carrier for developing an electrostatic charge image, comprising core particles coated with a coating resin containing a methylphenyl silicone polymer in the range of 6 to 3.0. 2. A carrier for developing an electrostatic charge image, comprising mixing the coating resin and core particles in a dry state and then heating the resin to melt the coating resin to coat the core particles. Manufacturing method.