JP3466875B2 - Electrophotographic carrier - Google Patents

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 charge latent image formed by an electrostatic recording method, and a two-component developer using the carrier.

[0002]

2. Description of the Related Art Conventionally, in a magnetic brush developing system, a carrier used to impart an appropriate amount of positive or negative electric charge to a toner is generally a coated carrier having a core material surface provided with a coating layer. And the non-coated carrier without a coating layer, the former is superior in view of the life of the developer. Therefore, the former coated carrier has been developed, and various types have been put into practical use. In particular,
The resin-coated carrier provided with a resin coating layer on the surface,
Various types of coated carriers have been developed because of improved charge control characteristics, improved environmental dependence, and improved stability over time. Here, the biggest problem in using the two-component type developer using such a resin-coated carrier is that the binder resin, the charge control agent, the external additive, etc., which are the constituent components of the toner, are on the carrier surface. To contaminate the coating layer and deteriorate the charge controllability over time.

In order to prevent such surface contamination of the resin-coated carrier, it has been proposed to use a low surface energy fluorine-based polymer or silicone-based polymer having excellent surface contamination resistance as a coating material. However, although the surface energy of the fluorine-based polymer is certainly low, the fluorine atom as a constituent thereof has a high electronegativity, so that the fluorine-based polymer cannot be used in a large amount as a material of the carrier for imparting the negative electrification property. Further, when a fluorine-based polymer is used as a coating material, there is a drawback that the charge imparting ability is remarkably deteriorated particularly under high temperature and high humidity, so that it cannot be put to practical use.

On the other hand, silicone-based polymers also have low surface energy and are effective against carrier surface contamination in the same manner as the above-mentioned fluorine-containing polymers, but carrier surface contamination cannot be completely prevented. Further, the silicone-based polymer is also positioned in the middle of the charging series, and it cannot be said that it is a sufficient carrier material for imparting negative charging property. or,
Carriers coated with a silicone-based polymer tend to have a slower rise in charging under low temperature and low humidity, and when a new toner is added, a low charge amount toner is likely to occur, causing fog and toner scattering in the formed image. There is a risk of In addition, the fluorine-based polymer and the silicone-based polymer have other problems such as poor adhesion to the material of the carrier core material and strength of the formed coating layer itself.

As a means for overcoming this problem, Japanese Patent Laid-Open No. Sho 4
In Japanese Patent Publication No. 9-51950, it is proposed to use an epoxy resin as an intermediate layer between the core material and the coating layer in order to improve the adhesion between the fluoropolymer and the carrier core material. Further, JP-A-57-99653 and JP-A-60-
Japanese Patent Laid-Open No. 202451 proposes to improve the adhesion between the two by using a fluorine-based block copolymer or graft copolymer.
In JP-A-16573 and JP-A-2-24670, it is proposed to improve the adhesion between the core material of the carrier and the coating layer by using a fluoropolymer containing a hydrolyzable silyl group. There is.

However, in each of these cases, although an improving effect for improving the adhesiveness is recognized,
There is still room for improvement in that the ability to impart negative charge to the toner is low and the environmental stability of imparting charge is insufficient.
On the other hand, one having a carrier coated with an imidazole derivative for the purpose of improving the ability to impart a negative charge is disclosed in JP-A-2-176.
In this case, the adhesion between the carrier core substance and the coating layer was not sufficient.

Further, in the case of using a silicone polymer, JP-A-60-19156 discloses that a coupling agent is used to improve the adhesion of the silicone resin coating layer to the core material. . However, even in this case, although there is an effect of improving the adhesiveness of the coating layer, there is still a problem that the ability to impart a negative charge to the toner is insufficient although the effect is not so high as that of the fluoropolymer. Further, it has been difficult to say that the resin coating layer made of such a material has a sufficient effect of preventing contamination on the carrier surface.

Further, in JP-A-62-121463, in order to improve the adhesion between the core material and the silicone resin, the surface of the carrier core treated with a silane coupling agent is
A carrier provided with a coating layer made of a silicone resin is described. However, in the case of the coating layer made of this silicone resin, there are problems in production such as non-uniform film formation and high curing temperature when coating the material for forming the coating layer. . Further, JP-A-64-35563, JP-A-64-29857 and JP-A-64-298.
No. 60 discloses a carrier having a coating layer having a laminated structure in which various functional films are laminated on the surface, but in any case, the charging ability cannot be maintained when repeatedly used for a long time. There was a problem.

On the other hand, as a means for improving the problem of maintaining the charging ability, JP-A-61-110159 and JP-A-61-110160 disclose a triboelectrification control layer and a release layer on a core material. It is described that a coated carrier having a conductive surface layer laminated thereon can stably impart a negative charging property to the toner and that the charge imparting property can be maintained well. However, these carriers have a practical problem in that the initial value of charging varies greatly and that the charge distribution of the toner spreads. Further, in this case, when the photoconductor is contaminated by the product generated by the ozone generated by the charger, the cleaning property of cleaning the photoconductor by the ear of the developer (hereinafter, also referred to as magnetic brush cleaning property). There was also a problem that it was insufficient in terms of). The present invention has been made in view of the above-mentioned problems of the conventional technology.

[0010]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is that the carrier surface is excellent in stain resistance and the photosensitive member surface is easily cleaned, and the charge imparting ability is stable under environmental conditions. Another object of the present invention is to provide a carrier for developing an electrostatic charge image, which is used in a magnetic brush developing method and has an excellent charge exchange property with a fast rising speed of application. That is, the main object of the present invention is that the rising speed of charge imparting is fast, the carrier surface is less likely to be contaminated by toner or an external additive even after long-term use, and the charge imparting ability is less likely to decrease due to environmental conditions, etc. It is to provide a carrier having excellent properties. Still another object of the present invention is to provide a carrier for developing an electrostatic charge image capable of forming a magnetic brush having excellent cleaning ability, which is capable of sufficiently removing photoreceptor contamination caused by products of ozone. is there. Particularly, in full-color development in which highlight image reproducibility is strictly required, this is a serious problem because photoreceptor contamination that occurs in this case is one of the main causes of image defects.

[0011]

The above object can be achieved by the present invention described below. That is, in the present invention, the surface of the core material is a vinyl-based copolymer having an acid value of 2 to 40 mgKOH / g, and a fluorine-containing vinyl-based copolymer having at least a fluorinated alkyl acrylate or a fluorinated alkyl methacrylate as a monomer component, A carrier for electrophotography, which is coated with a coating material containing an imidazole compound having an average particle diameter of 5 to 200 nm.

As a result of intensive studies to solve the above-mentioned problems of the prior art, the inventors have found that an imidazole compound having an average particle size of 5 nm to 200 nm has a good negative charge imparting property, and the imidazole compound is a carrier. It is possible to obtain a carrier having an excellent charge-imparting ability by using the above-mentioned coating layer, but in that case, it was found that there are the following problems. First, since the imidazole compound does not have adhesiveness with a composite made of a metal oxide such as ferrite particles used as a carrier core material, an excellent binder resin is required to form a strong coating layer. However, if a styrene acrylic resin having an acid value is used as the binder resin, the carrier core material and the imidazole compound are firmly bound by the acid group of the styrene acrylic resin and the basicity of the imidazole compound. It is possible to wear it. However, in this case, the excellent negative charge imparting ability of the imidazole compound is not sufficiently exerted, and when such a carrier is used as a developer,
It was found that the magnetic brush cleaning property against the stain on the photoreceptor caused by the generation of the product by ozone from the charger was not sufficient. According to the study of the present inventors, this phenomenon is caused by the fact that when a styrene acrylic resin is used as the binder resin, the imidazole compound, which is the negative chargeability imparting agent, is incorporated into the resin coating layer. It was speculated that this occurs because the amount of the imidazole compound present on the surface of the coating layer decreases.

Therefore, in order to expose a large amount of granular imidazole compounds having an average particle size of 5 nm to 200 nm on the surface of the carrier coating layer, the present inventors used the imidazole compound in combination with various binder resins. As a result of further studies on the above, as a result, a fluorine-containing vinyl copolymer having a fluorinated alkyl acrylate or fluorinated alkyl methacrylate as a monomer component (hereinafter, also referred to as “fluorinated alkyl (meth) acrylate copolymer”) was bound. When used as a part of resin, since this copolymer has a large atomic group, the imidazole compound is not deeply incorporated into the resin coating layer as compared with the case of using a styrene acrylic resin, and the carrier coating layer As a result of the large amount of imidazole compound present on the surface of the coating, a negative charge imparting agent is provided on the surface of the coating layer. It is possible to expose a large number of certain imidazole compounds, leading to the present invention by finding that the various problems described above can be solved. That is, according to the carrier in which the resin coating layer having the above-mentioned configuration is formed on the surface of the carrier core material, sufficient negative charge imparting ability is exhibited, and moreover, a large number of imidazole compounds present on the surface of the carrier coating layer are photosensitive. The inventors have found that contamination of the photoconductor is not observed at the time of development, probably because the product (for example, a nitric acid compound) generated by ozone, which is the cause of body contamination, is trapped.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to preferred embodiments of the present invention. In the electrophotographic carrier of the present invention, the surface of the carrier core material has an acid value of 2 to
A coating containing 40 mg KOH / g vinyl copolymer, a fluorine-containing vinyl copolymer having at least a fluorinated alkyl acrylate or a fluorinated alkyl methacrylate as a monomer component, and an imidazole compound having an average particle diameter of 5 to 200 nm. It is characterized by being covered with a material.

First, in the present invention, the vinyl-based copolymer having an acid value of 2 to 40 mgKOH / g used as a binder resin for the resin coating layer includes, for example, a carboxyl group as a polar functional group, an acid anhydride and / or Alternatively, those having an acid group formed by a partial ester thereof can be mentioned.
As such, for example, as a monomer unit, acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, dimethyl maleic acid and their acid anhydrides and / or partial esterified products thereof, and these, Examples thereof include copolymers with vinyl monomers such as olefin and styrene.

In the present invention, specific examples of the monomer that can be used when forming the above vinyl copolymer include ethyl acrylate, propyl acrylate, butyl acrylate and acryl as derivatives of acrylic acids. Octyl acid, 2-ethylhexyl acrylate, n-tetradecyl acrylate, n-hexadecyl acrylate,
Examples thereof include acrylic acid esters such as lauryl acrylate, cyclohexyl acrylate, diethylaminoethyl acrylate and dimethylaminoethyl acrylate. Similarly, as a derivative of methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, Examples thereof include methacrylic acid esters such as lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, and stearyl methacrylate. Examples of styrenes include styrene, α-methylstyrene, vinyltoluene, chlorostyrene and the like.

The vinyl copolymer having an acid group in its structure, which is used in the present invention and has the above-mentioned materials, has an acid value of 2 to 40 mgKOH / g, preferably 1
The one used is in the range of 0 to 30 mg KOH / g. That is, when the acid value is less than 2 mgKOH / g, the incorporation of the imidazole compound into the binder resin is weak, and the imidazole compound is easily peeled off from the surface of the carrier, and the charge imparting ability is deteriorated over a long period of use. On the other hand, acid value is 40mgKOH
When the amount exceeds / g, the imidazole compound is deeply incorporated into the binder resin, and is difficult to be exposed on the surface of the carrier coating layer, and the effect of adding the imidazole compound cannot be sufficiently obtained. Further, in the present invention, the number average molecular weight (Mn) of the vinyl-based copolymer having the above-mentioned specific acid value is 3,000 to 50,0.
00, the weight average molecular weight (Mw) is 4,000 to 100,
It is preferred to use those having a molecular weight in the range of 000.

In the present invention, the acid value of the resin (mgKO
H / g) was measured by the following method. Resin sample 2
Accurately weigh 10g to put it in a 200-300ml Erlenmeyer flask, and methanol: toluene = 30:70
About 50 ml of the mixed solvent of is added to dissolve the resin. At this time, a small amount of acetone may be added if the solubility of the resin seems to be poor. Then, the measurement sample prepared in this manner was pre-standardized with N / 10 which was mixed with 0.1% of bromthymol blue and phenol red mixed indicator.
Is titrated with an alcoholic solution of potassium hydroxide and the acid value of the resin sample is calculated from the consumption amount of the KOH solution used for the titration according to the following calculation formula (1). Acid value = KOH (number of ml) × f × 56.1 / Sample weight (g) (1) (In the formula, f represents a factor of N / 10 KOH alcohol solution)

Next, in the coating layer of the electrophotographic carrier of the present invention, a granular imidazole compound is used as a negative charge imparting agent in addition to the vinyl copolymer having a specific acid value as described above .

The following are mentioned as specific examples of the imidazole compound which is particularly preferably used. Specifically, for example, 2-methylimidazole, 2-ethyl-4
-Methylimidazole, 2-phenylimidazole, 2
-Undecyl imidazole, 2-heptadecyl imidazole, 1-benzyl-2-methyl imidazole, 1-cyanoethyl-2-methyl imidazole, 1-cyanoethyl-2-phenyl imidazole, 1-cyanoethyl-2
-Ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2
-Methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate, 1-cyanoethyl-2-undecylimidazole trimellitate, 2, 4-diamino-6- (2 '
-Methylimidazolyl (1 '))-ethyl-s-triazine, 2,4-diamino-6- (2'-undecylimidazolyl- (1'))-ethyl-s-triazine, 2,
4-diamino-6- (2'-ethyl-4'-methylimidazolyl (1 '))-ethyl-s-triazine, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1,3-dibenzyl- 2-methylimidazolium chloride, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-cyanoethyl-2-
Compounds selected from the group of phenyl-4,5-di (cyanoethoxymethyl) imidazole are mentioned.

The above-mentioned imidazole compound used in the present invention has an average particle size of 5 to 200 nm. 5n
When it is less than m, the charge imparting ability is lowered and the effect of trapping contaminants on the photoconductor is reduced. On the other hand, 20
If it exceeds 0 nm, the strength of the coating film formed by the binder resin tends to decrease, which causes a problem during long-term use.

Further, in the coating layer of the electrophotographic carrier of the present invention, in addition to the vinyl copolymer having a specific acid value and the imidazole compound having a specific particle size, a fluorinated alkyl acrylate or It has a fluorine-containing vinyl-based copolymer containing a fluoroalkyl methacrylate as a monomer component. Further, it is preferable to use a fluorinated alkyl (meth) acrylate copolymer having a fluorinated alkyl (meth) acrylate monomer amount of 10 to 60% by weight. Furthermore, it is preferable that the mixing ratio of the copolymer to the vinyl copolymer having a specific acid value described above is 20 to 70% by weight.

The fluorinated alkyl acrylate or fluorinated alkyl methacrylate constituting the fluorinated alkyl (meth) acrylate copolymer used in the present invention includes, for example, acrylic acid or methacrylic acid
1-dihydroperfluoroethyl, 1,1-dihydroperfluoropropyl, 1,1-dihydroperfluorohexyl, 1,1-dihydroperfluorooctyl, 1,1-dihydroperfluorodecyl, 1,1-dihydroperfluoro Lauryl, 1,1,2,2-tetrahydroperfluorobutyl, 1,1,2,2-tetrahydroperfluorooctyl, 1,1,2,2-tetrahydroperfluorodecyl,
1,1,2,2-dihydroperfluorolauryl, 1,
1,2,2-dihydroperfluorostearyl, 2,2
3,3-tetrafluoropropyl, 2,2,3,3,4
4-hexafluorobutyl, 1,1, ω-trihydroperfluorohexyl, 1,1, ω-trihydroperfluorooctyl, 1,1,1,3,3,3-hexafluoro-2-
Chloropropyl, 3-perfluorononyl-2-acetylpropyl, 3-perfluorolauryl-2-acetylpropyl, N-perfluorohexylsulfonyl-N-methylaminoethyl, N-perfluorohexylsulfonyl-N
-Butylaminoethyl, N-perfluorooctylsulfonyl-N-methylaminoethyl, N-perfluorooctylsulfonyl-N-ethylaminoethyl, N-perfluorooctylsulfonyl-N-butylaminoethyl, N-
Perfluorodecylsulfonyl-N-methylaminoethyl, N-perfluorodecylsulfonyl-N-ethylaminoethyl, N-perfluorodecylsulfonyl-N-butylaminoethyl, N-perfluorolaurylsulfonyl-
Examples thereof include ester compounds such as N-methylaminoethyl, N-perfluorolaurylsulfonyl-N-ethylaminoethyl, N-perfluorolaurylsulfonyl-N-butylaminoethyl.

Examples of the monomer component to be copolymerized with the above-mentioned fluorinated alkyl acrylate or fluorinated alkyl methacrylate include styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, Alkyl styrenes such as butyl styrene, hexyl styrene, heptyl styrene, octyl styrene; halostyrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodostyrene; and nitrostyrene, acetylstyrene,
Styrene-based monomers such as methoxystyrene; addition-polymerizable unsaturated compounds such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, α-methylcrotonic acid, α-ethylcrotonic acid, isocrotonic acid, tiglic acid, and ungeric acid Aliphatic monocarboxylic acid; addition-polymerizable unsaturated aliphatic dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, dihydromuconic acid; and the addition-polymerizable unsaturated carboxylic acid and alcohol Esterification products such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amino alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol,
Alkyl alcohols such as dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, etc. Alkoxyalkyl such as methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethoxyethyl alcohol, methoxypropyl alcohol, ethoxypropyl alcohol, etc., which are obtained by partially alkoxylating these alkyl alcohols. Esters of aralkyl alcohols such as alcohol, benzine alcohol, phenylethyl alcohol, phenylpropyl alcohol, etc., and alkenyl alcohols such as allyl alcohol, crotonyl alcohol, etc., preferably acrylic acid alkyl ester, methacrylic acid alkyl ester (excluding methyl methacrylate) , Fumaric acid alkyl ester, maleic acid alkyl ester, etc .; Amides derived from carboxylic acids and nitriles, ethylene, propylene, butene, aliphatic monoolefins isobutylene, vinyl chloride, vinyl bromide, vinyl iodide, 1,2-dichloroethylene, 1,2
-Dibromoethylene, 1,2-diiodoethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride, vinylidene fluoride and other halogenated fatty acid olefins; 1,3-butadiene , 1,3-pentadiene, 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene,
Conjugated diene-based aliphatic diolefins such as 2,3-hexadiene and 3-methyl-2,4-hexadiene; 4-vinylpyridine, 2-vinyl-6-methylpyridine, 2-vinyl-5-methylpyridine, 2- Vinyl-5-methylpyridine, 4-butenylpyridine, 4-pentylpyridine,
N-vinylpiperidine, 4-vinylpiperidine, 4-vinylpiperidine, N-vinyldihydropyridine, N-vinylpyrrole, 2-vinylpyrrole, N-vinylpyrrolidine, N-vinylpyrrolidine, 2-vinylpyrrolidine, N
-Vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinylcarbazole, and other nitrogen-containing vinyl-based monomers are exemplified. These monomers alone or 2
You may use it in combination of 2 or more types.

Next, as the carrier core material used when forming the resin coating layer made of the above-mentioned constituent materials, any conventionally known carrier core material can be used. For example, iron,
Examples include ferromagnetic metals such as cobalt, those obtained by dispersing a magnetic substance in a resin, magnetite, hematite, and ferrite. Preferably, ferrite containing at least two kinds of Mn, Mg, Cu, Zn, and Ca, whose surface smoothness can be easily controlled, is preferable. When the core material having high smoothness is used, the fluorinated alkyl (meth) acrylate and the imidazole compound are not deeply taken into the resin coating layer and can be easily exposed to the surface layer.

The average particle size of the carrier core material used in the present invention is preferably about 20 to 100 μm, and more preferably 30 to 65 μm. This is because when the average particle diameter of the carrier core material is less than 20 μm, the distribution of the carrier particles is increased, and the fine powder system is increased and the magnetization per particle is lowered, and carrier scattering easily occurs, and the average particle of the carrier is If it exceeds 100 μm, the specific surface area decreases, and the toner tends to scatter. In particular, in a full-color image having many solid portions, it is not preferable that the average particle size of the carrier exceeds 100 μm, because the solid portions are poorly reproduced.

In the electrophotographic carrier of the present invention,
On the surface of the carrier core material as described above, a fluorine-containing vinyl-based copolymer having at least a fluorinated alkyl acrylate or a fluorinated alkyl methacrylate as a monomer component and the vinyl-based copolymer having an acid value of 2 to 40 mgKOH / g described above. A forming material containing a polymer and an imidazole compound having an average particle diameter of 5 to 200 nm is coated to form a coating layer. At that time, as a solvent used to obtain an optimum coating film, for example, , Toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like.

Further, in the material for forming the resin coating layer used in the present invention, other resin components such as acrylic acid ester resin, methacrylic acid ester resin, styrene-acrylic acid ester copolymer, Styrene-methacrylic acid ester copolymer, methacrylic acid ester-modified silicone resin, acrylic acid ester-modified silicone resin, styrene-acrylic acid ester-modified silicone resin, styrene-methacrylic acid-modified silicone resin, amino-modified silicone resin, polyester, dimethyl silicone resin , Diphenyl silicone resin, epoxy-modified silicone resin, methylphenyl silicone resin and the like may be used alone or in combination.

In the electrophotographic carrier of the present invention, first, a resin coating liquid (material for forming a resin coating layer) made of the above-mentioned materials is prepared, and then this resin coating liquid is used as a carrier core material. After coating, it is dried and cured to form a coating layer.
The baking device for drying and curing the resin coating liquid may be either an external heating system or an internal heating system, and may be, for example, a fixed or fluidized electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking. . The resin coating amount of the electrophotographic carrier of the present invention is preferably 0.1 to 5.0% by weight based on the total amount of the carrier,
More preferably, it may be in the range of 0.15 to 2.0% by weight.

The electrophotographic carrier of the present invention obtained as described above is mixed with a toner and used as a two-component developer. As the toner used at this time, a colorant, a charge control agent dispersed in a binder resin, or the like,
Any of the toners used in conventionally known two-component developers can be preferably used. The binder resin used for the toner is not particularly limited, but examples thereof include polystyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-acrylic ester copolymer, styrene-methacrylic acid copolymer, Further, rosin-modified maleic acid resin, epoxy resin, polyester resin, polyurethane resin and the like can be mentioned, and these can be used alone or in combination.

Any appropriate charge control agent can be used as the charge control agent used in the toner used in the present invention. Examples include salicylic acid metal complexes, metal-containing monoazo dyes, nigrosine bases, and the like. As the colorant constituting the toner, conventionally known dyes and / or pigments can be used, and any of those used for full color can be used. Examples thereof include carbon black, phthalocyanine blue, permanent red, permanent yellow and the like. The content of the colorant is 0.5 to 1 with respect to 100% by weight of the binder resin.
It may be about 0% by weight. In addition, external additives such as silica titania or alumina fine powder can be added according to the toner particles.

To prepare the toner used in the present invention, for example, the above-mentioned binder resin, charge control agent, colorant and the like are thoroughly mixed with a mixer such as a Henschel mixer, kneaded with a twin-screw extruder, and then cooled. After coarsely pulverizing the mixture with a feather mill or the like, the mixture can be obtained by using a jet pulverizer, an air stream classifier or the like to form particles having a desired particle size, and adding an external additive or the like and mixing with a mixer. .

(Measurement of Binder Resin Molecular Weight) Next, the method for measuring the binder resin molecular weight in the present invention will be described. The molecular weight of the present invention is measured by a chromatogram by GPC (gel permeation chromatography) under the following conditions. The column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) as a solvent was passed through the column at this temperature at a flow rate of 1 ml / min while the sample concentration was 0.05 to 0.
The THF sample solution of the resin adjusted to 6 wt% is 50 to 20
Inject 0 μl and measure. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value and the count number of a calibration curve prepared from several kinds of monodisperse polystyrene standard samples. As a standard polystyrene sample for preparing the calibration curve, for example, Pressure Chre
electrical Co. Manufactured or manufactured by Toyo Soda Kogyo Co., Ltd. having a molecular weight of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.7.
5 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 ×
10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ^{6, and the} like, and it is suitable to use a standard polystyrene sample of at least about 10 points. An RI (refractive index) detector is used as the detector.

As the column, a plurality of commercially available polystyrene gel columns may be combined in order to accurately measure the molecular weight region of 10 ³ to 2 × 10 ⁶ , for example, Watt.
ers manufactured by the μ-styragel 500,10 ^3,
Combination of 10 ⁴ and 10 ⁵ and Shodex manufactured by Showa Denko KK
KF-80M and KF-801, 803, 804, 8
05 combination, KA-802, 803, 804, 805
Or a combination of Toyo Soda and TSKgel G100
0H, G2000H, G2500H, G3000H, G
4000H, G5000H, G6000H, G7000
A combination of H and GMH is preferred.

(Measurement of average particle size of imidazole compound)
Next, a method for measuring the average particle size of the imidazole compound used in the present invention will be described. In the present invention, the imidazole compound was ultrasonically dispersed using a laser diffraction / scattering type particle size distribution measuring device and then measured.

[0036]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, "part" and "%" are based on weight unless otherwise specified. Example 1 The following materials were dissolved in 20 parts of xylene solvent to prepare a coating layer forming material.・ Styrene / methacrylate / maleic anhydride (70/20/10) copolymer (Mn = 10,000, Mw = 35,000, acid value = 20 mgKOH / g) 0.2 parts ・ 1,1-dihydroperfluoro Ethyl methacrylate / styrene (30/70) copolymer 0.1 part, 2-undecyl imidazole (average particle size 70 nm) 0.05 part

Next, using a fluidized bed coating apparatus, 100 parts of Mn-Mg ferrite particles having an average particle diameter of 45 μm were used as the core material, and the surface of the core material was coated with the coating layer forming material obtained above. Then, the coating layer is formed, and the carrier 1
Got Using Carrier 1 obtained above and CLC700 black toner, a black developer was prepared so that the toner concentration would be 6% by weight. Then, this developer 1 is mounted on a full-color copying machine CLC700 manufactured by Canon Inc., and the image area ratio is 6% under the environment of 23 ° C./5% RH.
50,000 originals were copied.

As a result, as shown in Table 1, the fluctuation of the image density after 50,000 sheets is small as compared with the image density at the initial stage, and even after 50,000 sheets, there is no fog on the image and high quality is obtained. Image was obtained. Further, as shown in Table 1, there was almost no change in the charge amount of the toner after 50,000 sheets, and the durability stability was excellent. Furthermore, the change in the amount of charge with respect to environmental changes under the conditions of high temperature and high humidity and room temperature and low humidity was also small. Further, the charging characteristics were excellent, and the image contamination on the photosensitive drum, which tends to become remarkable under high humidity, did not occur at all, and the excellent characteristics were exhibited. These evaluation methods and evaluation criteria will be described later.
The test under high humidity was conducted under the condition that ozone products stayed in the copying machine without operating the exhaust fan in the machine.

Example 2 A carrier 2 was obtained in the same manner as in Example 1 except that the composition of the coating layer forming material was changed as follows. -Styrene / n-butyl acrylate / maleic anhydride (80/15/5) copolymer (Mn = 13,000, Mw = 40,000, acid value = 10 mgKOH / g) 0.2 parts-1,1- Dihydroperfluoroethyl methacrylate / styrene (20/80) copolymer 0.05 part 2-phenyl-4,5-dihydroxyimidazole 0.02 part Further, using the carrier 2 obtained above, Example 1 A developer was prepared in the same manner as above, and each evaluation was performed in the same manner as in Example 1 using the developer. As a result, as shown in Table 1, good results were obtained as in Example 1.

Example 3 A carrier 3 was obtained in the same manner as in Example 1 except that the composition of the coating layer forming material was changed as follows.・ Styrene / methacrylate / maleic anhydride (70/15/15) copolymer (Mn = 8,500, Mw = 47,000, acid value = 35 mgKOH / g) 0.2 parts ・ 1,1-dihydroper Fluoroethyl methacrylate / styrene (25/75) copolymer 0.05 part 2-phenyl-4,5-dihydroxyimidazole 0.02 part Further, using the carrier 3 obtained above, the same as Example 1. In the same manner as in Example 1, each developer was evaluated. As a result, as shown in Table 1, good results were obtained as in Example 1.

Comparative Example 1 A carrier 4 for comparison was obtained in the same manner as in Example 1 except that the composition of the material for forming the coating layer was changed as follows. In this comparative example, unlike Example 1, a vinyl copolymer having a low acid value was used as the binder resin for the coating layer. -Styrene / n-butyl acrylate (80/20) copolymer (Mn = 10,500, Mw = 37,000, acid value = 0.1 mgKOH / g) 0.2 parts-1,1-dihydroperfluoroethyl Methacrylate / styrene (20/70) copolymer 0.05 part 2-phenyl-4,5-dihydroxyimidazole 0.02 part Further, using the carrier 4 obtained above, in the same manner as in Example 1. A developer was prepared, and the same evaluation as in Example 1 was performed using the developer. As a result, as shown in Table 1, the fluctuation of the image density and the fluctuation of the charge amount after 50,000 sheets were large, and the durability stability was poor. In addition, the change in the charge amount due to the environment was large, and the charge characteristics were inferior.
Fogging occurred on the image after 50,000 sheets, and the image characteristics in durability were inferior.

Comparative Example 2 A comparative carrier 5 was obtained in the same manner as in Example 1 except that the composition of the coating layer forming material was changed as follows. In this comparative example, unlike Example 1, the fluorinated alkyl (meth) acrylate copolymer is not used as a part of the binder resin of the coating layer. Styrene / n-butyl acrylate / maleic anhydride (80/15/5) copolymer (Mn = 13,000, Mw = 40,000, acid value = 10 mgKOH / g) 0.2 parts 2-phenyl- 4,5-Dihydroxyimidazole 0.02 part Further, a developer was prepared in the same manner as in Example 1 using the carrier 5 obtained above, and the same evaluation as in Example 1 was performed using this developer. I went. As a result, as shown in Table 1, variations in image density after 50,000 sheets, variations in charge amount, and fog were poor, durability stability was lacking, and there was a problem in practical use.

Comparative Example 3 A carrier 6 for comparison was obtained in the same manner as in Example 1 except that the composition of the coating layer forming material was changed as follows. In this comparative example, unlike Example 1, the coating layer does not contain an imidazole compound. -Styrene / n-butyl acrylate / maleic anhydride (80/15/5) copolymer (Mn = 13,000, Mw = 40,000, acid value = 10 mgKOH / g) 0.2 parts / 1,1- Dihydroperfluoroethylmethacrylate / styrene (5/95) copolymer 0.05 part Further, a developer was prepared in the same manner as in Example 1 using the carrier 6 obtained above, and using this, Each evaluation was performed in the same manner as in Example 1. As a result, as shown in Table 1, the fog after 50,000 sheets and the fluctuation of the charge amount were bad,
It lacked durability stability and had a bad level of image contamination on the photosensitive drum.

[0044]

[Table 1] Table 1: Evaluation results

<Evaluation Method> 1. Image densities were copied under proper exposure conditions, and the image densities of the solid portion at the initial stage and after the endurance of 50,000 sheets were measured with a Macbeth densitometer, and
D. The change was evaluated by the change in the value.

2. Fog on image Toner fog on white background REFLE made by Tokyo Denshoku Co., Ltd.
It measured using CTO METERMODEL TC-6DS and evaluated the rank as follows. ○: Less than 0.5% △: 0.5 or more and less than 1.5% ▲: 1.5 or more and less than 2.5% ×: 2.5% or more

3. Environmental change in charge amount Charge amount Q (LL) after leaving the developer for one day in an environment of room temperature and low humidity (23 ° C., 5% humidity) and high temperature and high humidity (3
0 ° C, 80% humidity) Charge amount Q after left for 1 day in an environment
(HH) is calculated using the charge amount measuring method described later,
The difference ΔQ (= Q (LL) -Q (HH)) was obtained and the rank was evaluated as follows. ◯: ΔQ = less than 10 μC Δ: ΔQ = 10 μC or more and less than 15 μC ▲: ΔQ = 15 μC or more and less than 20 μC ×: ΔQ = 20 μC or more

4. Durability fluctuation of charge amount Charge amount Q (sta
rt) and the charge amount Q (last) after 50,000 sheets are calculated using the charge amount measuring method described later, and the difference ΔQ (=
Q (start) -Q (last)) was obtained, and rank evaluation was performed as follows. ◯: ΔQ = less than 5 μC Δ: ΔQ = 5 μC or more and less than 10 μC ▲: ΔQ = 10 μC or more and less than 15 μC ×: ΔQ = 15 μC or more

5. Image contamination on the photoconductor drum Under a condition of 30 ° C. and 80% humidity, a halftone image was formed using a CLC700 manufactured by Canon Inc. without operating an exhaust fan, and the image quality was evaluated according to the following ranks. . ◯: No image deletion is seen Δ: A little image deletion is seen, but there is no problem in practical use ▲: Image deletion is seen and there is a problem in practical use ×: Image deletion is seen on the entire surface and is not practical Level

The charge amount of the developer in the present invention was measured by the following method. FIG. 1 is an illustration of an apparatus for measuring the amount of charge of toner. First, about 0.5 to 1.0 g of a mixture (developer) of toner and carrier whose triboelectric charge is to be measured is placed in a metal measuring container 2 having a 500 mesh screen 3 on the bottom, Put the lid 4 on. At this time, the weight of the entire measuring container 2 is weighed, and W ₁ (k
g). Next, in the suction device 1 (at least the portion in contact with the measurement container 2 is an insulator), suction is performed from the suction port 7,
Adjust the air volume and adjust the pressure of vacuum gauge 5 to 2,450 Pa (25
0 mmAq). This state is sufficient, preferably about 2
Suction for a minute to remove the toner by suction. The potential of the electrometer 9 at this time is V (volt). Here, 8 is a condenser, and the capacity is C (mF). The weight of the entire measuring container after suction is weighed and is W ₂ (kg). From the above measured values, the triboelectric charge amount of the toner at this time (mC / kg)
Is calculated by the following formula. Toner triboelectric charge amount (mC / kg) = (C × V) / (W
_1- W ₂ )

[0051]

As described above, according to the present invention,
Provided is an electrophotographic carrier capable of stably maintaining a high charge imparting property regardless of environmental conditions and capable of forming a good image even when a developer is used for a long period of time. Furthermore, according to the present invention, it is possible to form a magnetic brush having excellent cleaning properties that is capable of sufficiently removing photoreceptor contamination caused by ozone products, and as a carrier for full-color two-component development in which highlight reproduction is important. Also provided is an electrophotographic carrier capable of stably forming a high-quality image, which is also useful.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus for measuring a charge amount of a developer in the present invention.

[Explanation of symbols]

1: Suction machine 2: Measuring container 3: Conductive screen 4: Lid 5: Vacuum gauge 6: Same amount control valve 7: Suction port 8: Capacitor 9: Electrometer

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-2-176774 (JP, A) JP-A-5-216282 (JP, A) JP-A-4-175769 (JP, A) JP-A-62-1 138859 (JP, A) JP 61-120169 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/107-9/113

Claims (2)

(57) [Claims] 1. The surface of the core material has an acid value of 2 to 40 mgKOH /
A coating material containing g of a vinyl-based copolymer, at least a fluorine-containing vinyl-based copolymer having a fluorinated alkyl acrylate or a fluorinated alkyl methacrylate as a monomer component, and an imidazole-based compound having an average particle diameter of 5 to 200 nm. An electrophotographic carrier characterized by being coated. 2. The core material has magnetism, and Mn, Mg,
The electrophotographic carrier according to claim 1, which is a ferrite particle containing at least two kinds of Cu, Zn and Ca.