JP2853272B2 - Carrier for magnetic brush development and developer composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic brush developing carrier used for developing an electrostatic latent image in electrophotography and electrostatic recording,
And a developer composition.

(Prior Art) In electrophotography, a photoconductive material such as selenium is used as a photoreceptor, an electrostatic latent image is formed using various means, and a magnetic brush developing method is applied to the electrostatic latent image. In general, a method of adhering toner by using such a method to visualize the toner is adopted.

In the magnetic brush developing method, carriers used to apply an appropriate amount of positive or negative electricity to toner are generally roughly classified into coated carriers and uncoated carriers. Since the former is superior, various types of coated carriers have been developed and put into practical use.

On the other hand, toners using various resins as binder resins have been proposed, and toners using polyester resins are also known. It is also known to use an inorganic powder such as silica for the purpose of improving the powder fluidity of the toner.

(Problems to be Solved by the Invention) There are various properties required for the coated carrier, but particularly important properties are appropriate chargeability, impact resistance,
Abrasion resistance, good adhesion between the core material and the coating layer, uniformity of charge distribution, etc. can be improved.

In view of the above properties, conventionally used coated carriers still have problems to be improved, and the perfect ones are not known at present. For example, as coating materials, fluorinated vinyl polymers are excellent in surface contamination resistance, but have problems in adhesion to the core material, and acrylic polymers have mechanical strength and adhesion to the core material. However, there is a problem in surface contamination resistance and chargeability. In any case, at present, it is necessary to use a coating material having advantages and disadvantages.

On the other hand, in the case of a developer using a polyester resin as a binder resin as a toner, there are disadvantages in that the amount of charge varies greatly due to environmental fluctuations and a wide charge distribution is exhibited.

Further, when an external additive such as silica is added to the toner, a region exhibiting an effect of improving powder fluidity (a coverage of 100%).
%), There is also a problem that the environment dependency of the charging of the developer is greatly reduced.

The present invention has been made in view of the various problems as described above.

An object of the present invention is to show good chargeability, good environmental dependency of charge, without causing a decrease in charge amount during running, and as a result, early generation of fog and no occurrence of in-machine contamination. An object of the present invention is to provide a magnetic brush developing carrier.

Another object of the present invention is to provide a developer having excellent developing characteristics.

(Means for Solving the Problems) The present inventors have conducted various studies and studies to improve the above-mentioned drawbacks in the prior art, and as a result, the use of a specific coating material has led to the demand for the above-mentioned coated carrier. The developer composition in which the carrier and the toner containing the polyester as a binder resin exhibit excellent development characteristics, especially when a specific external additive is added , The charge amount is in an appropriate range,
The inventors have found that the environment dependence of charging is excellent and that the charge distribution is sharp, and have completed the present invention.

The above object of the present invention can be achieved by coating the magnetic core material with an acrylate or methacrylate copolymer having a nitrogen-containing vinyl monomer content of 0.1 to 2.0% by weight.

That is, the carrier of the present invention is intended for use in a toner containing a polyester resin, and is a binary copolymer comprising an acrylate ester or a methacrylate ester and 0.1 to 2.0% by weight of a nitrogen-containing vinyl monomer. Or
Alternatively, a coating layer consisting of a terpolymer is provided if it is composed of an acrylate ester or a methacrylate ester, 0.1 to 2.0% by weight of a nitrogen-containing vinyl monomer, and 40% by weight or less of another monovinyl monomer. It is characterized by.

Further, the developer composition of the present invention is characterized by comprising the carrier and a polyester-based toner obtained by externally adding amorphous titania fine particles to toner particles containing a polyester resin as a binder resin.

 Hereinafter, the present invention will be described in detail.

Examples of the magnetic core material (hereinafter, simply referred to as a core material) used in the present invention include iron powder, iron oxide powder, carbonyl iron powder, magnetite powder, and powders such as nickel and ferrite. As a normal carrier,
Those having a particle size of 10 to 500 μm are used.

In the nitrogen-containing vinyl monomer-containing acrylate or methacrylate copolymer used for coating the core material surface, examples of the nitrogen-containing vinyl monomer include 2-vinylpyridine, 4-vinylpyridine, and 2-vinylpyridine.
Vinyl-6-methylpyridine, 2-vinyl-5-methylpyridine, 4-butenylpyridine, 4-pentenylpyridine, N-vinylpiperidine, 4-vinylpiperidine,
N-vinyl dihydropyridine, N-vinyl pyrrole, 2
-Vinylpyrrole, N-vinylpyrroline, N-vinylpyrrolidine, 2-vinylpyrrolidine, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinylcarbazole, N-vinylmorpholine and the like are used. These can be used alone or in combination of two or more. The copolymerization ratio of these nitrogen-containing vinyl monomers must be in the range of 0.1 to 2.0% by weight based on the total weight of the copolymer. 0.1% by weight of nitrogen-containing vinyl monomer
If it is lower, the absolute value of the charge amount will decrease, causing toner contamination in the copying machine. On the other hand, if it exceeds 2.0% by weight, the absolute value of the charge amount becomes higher than an appropriate range, particularly under low temperature and low humidity, and the image density is lowered.
Further, the environment dependence of charging increases.

On the other hand, acrylates or methacrylates include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, etc. Alkoxy alcohols such as methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethoxyethyl alcohol, methoxypropyl alcohol, ethoxypropyl alcohol, etc., which are alkoxylated alkyl alcohols, benzyl alcohol, phenylethyl alcohol, phenylpropyl alcohol Aralkyl alcohols, allyl alcohol, crotony Alkenyl alcohols such alcohols, esters of thereof. Of these, alkyl acrylate and alkyl methacrylate are preferred.

In the present invention, if desired, another monovinyl monomer can be further copolymerized. Such monovinyl monomers include styrene, methylstyrene,
Dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, alkylstyrene such as octylstyrene,
Halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene and iodostyrene; and styrene-based monomers such as nitrostyrene, acetylstyrene and methoxystyrene; acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, Addition-polymerizable unsaturated aliphatic monocarboxylic acids such as α-methyl crotonic acid, α-ethyl crotonic acid, isocrotonic acid, tiglic acid, ungeric acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid , Addition-polymerizable unsaturated aliphatic dicarboxylic acids such as dihydromuconic acid;
Esters, amides, and nitriles of the above carboxylic acids other than acrylic acid and methacrylic acid esters; aliphatic monoolefins such as ethylene, propylene, butene, and isobutylene; vinyl chloride, vinyl iodide, 1,2-dichloroethylene, 1,2-dibromo Ethylene, 1,2-diiodoethylene,
Examples include halogenated aliphatic olefins such as isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride, and vinylidene fluoride. The amount of the monovinyl monomer to be copolymerized as desired is desirably 40% or less based on the total weight of the copolymer.

The acrylic acid or methacrylic acid ester copolymer containing the nitrogen-containing vinyl monomer used in the present invention can have a number average molecular weight in the range of 10,000 to 200,000, particularly preferably in the range of 50,000 to 100,000. . When the number average molecular weight is lower than 10,000,
In the copying machine, a phenomenon occurs in which the coating layer is peeled off from the core material, and when the coating layer is higher than 200,000, it becomes difficult to coat the core material.

The electrophotographic carrier of the present invention is obtained by subjecting the magnetic core material as described above to a surface treatment with the copolymer mixture as described above, and forming a coating layer of the copolymer mixture on the surface of the core material by chemical bonding or adsorption. Can be obtained.

The surface treatment of the core material can be performed by, for example, mixing a solution obtained by dissolving the mixture of the above-mentioned copolymers in a suitable solvent with the core material and drying. The coating amount of the copolymer is 0.5 μm on the surface of the core material.
The amount is preferably such that a coating layer having a thickness of not more than μm is formed. If the film thickness exceeds 0.5 μm, there is a problem that the carrier resistance becomes high and the image density of a large area decreases, so the film thickness is desirably 0.5 μm or less.

The thus obtained electrophotographic carrier of the present invention is mixed with a toner and used as a developer composition for a magnetic brush for developing an electrostatic latent image.

As the toner used in combination with the carrier, any known toner in which a polyester resin is used as a binder resin and a colorant is dispersed therein can be used. When a toner using a polyester resin is used as the binder resin, by adding amorphous titania as an external additive, the width of the charge distribution at low temperature and low humidity inherent in the polyester resin and under high temperature and high humidity The effect of resolving problems such as a low charge amount in the device is remarkable.

As the polyester resin used as the binder resin, for example, a linear polyester resin composed of a polycondensate using bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components can be preferably used. More specifically, a linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol, having a softening point of 100 to 125 ° C. and a glass transition point of 55 to
A resin having a number average molecular weight (3.3 ± 0.3) × 10 ³ , a weight average molecular weight (9.1 ± 0.4) × 10 ³ , an acid value of 6 to 12, and a hydroxyl value of 25 to 40 can be particularly preferably used.

Amorphous titania used as an external additive is preferably treated with a coupling agent. Amorphous titania particles to be treated have a higher surface hydroxyl value, are more active, and have higher reactivity with coupling agents than crystalline ones. It becomes possible to do. In addition, the particle size of the primary particles is 1.0 μm or less, preferably 0.3 μm or less.

The addition amount is preferably in the range of 0.1% by weight to 2.0% by weight based on the toner.

(Example) Example 1 Carrier Preparation Example Carrier 1 (Comparative Example) As a coating agent, a nitrogen-containing methacrylate copolymer (Mn = 50) composed of 20% by weight of styrene, 75.0% by weight of methyl methacrylate and 5.0% by weight of 4-vinylpyridine. , 0
(Mw = 100,000) and dissolved in toluene to prepare a 20% solution. The resulting solution was used as a coating solution.

As a core material, Cu-Zn ferrite carrier particles (F-100, manufactured by Powder Tech) having an average particle size of 120 μm were used, and 1.2 parts by weight of the above coating solution was added to the core material and mixed with a kneader. , Drying, sieving, film thickness
A coated carrier of 0.25 μm was obtained.

Carrier 2 (the present invention) As a coating agent, a nitrogen-containing methacrylate copolymer (Mn = 50,0) comprising 20% by weight of styrene, 78.0% by weight of methyl methacrylate and 2.0% by weight of 4-vinylpyridine.
(Mw = 100,000) and dissolved in toluene to prepare a 20% solution. Using the obtained solution as a coating solution, a coating layer carrier was obtained in the same manner as in the case of Carrier 1.

Carrier 3 (Invention) As a coating agent, a nitrogen-containing methacrylate copolymer (Mn = 50,0%) comprising 20% by weight of styrene, 79.0% by weight of methyl methacrylate and 1.0% by weight of 4-vinylpyridine.
(Mw = 100,000) and dissolved in toluene to prepare a 20% solution. Using the obtained solution as a coating solution, a coating layer carrier was obtained in the same manner as in the case of Carrier 1.

Carrier 4 (Invention) As a coating agent, a nitrogen-containing methacrylate copolymer composed of 20% by weight of styrene, 79.9% by weight of methyl methacrylate and 0.1% by weight of 4-vinylpyridine (number average molecular weight Mn = 50,000, weight average molecular weight Mw = 100,000) ) Was dissolved in toluene to prepare a 20% solution. Using the obtained solution as a coating solution, a coating layer carrier was obtained in the same manner as in the case of Carrier 1.

Carrier 5 (Comparative Example) As a coating agent, a copolymer composed of 20% by weight of styrene and 80.0% by weight of methyl methacrylate (Mn = 5)
0,000, Mw = 100,000) and dissolved in toluene to 20%
A solution was prepared. The obtained solution was used as a coating solution, and a coated carrier was obtained in the same manner as in the case of Carrier 1.

Example 2 Toner preparation example Toner 1 95 parts by weight of polyester resin (trade name: Plusdec S-1000, manufactured by Dainippon Ink Co., Ltd.) (Mn = 4,000, Mw = 10,000) Carbon black (# 4000 manufactured by Mitsubishi Chemical Corporation) 5 parts by weight) The above materials were kneaded with an extruder, pulverized with a jet mill, and classified with an air classifier to obtain a toner having an average particle diameter of 9 μm.

To the toner obtained as described above, as an external additive,
Amorphous titania having an average particle diameter of 15 nm (trade name: Ultra Fine Powder, manufactured by Idemitsu Kosan Co., Ltd.) (hydrophobicized by treating the surface with a low-molecular-weight silane coupling agent) was added and mixed with a Henschel mixer. . The amount of amorphous titania added was such that the toner surface was covered with 100% coverage. In addition, the covering ratio means a covering ratio when the surface of the external additive is regarded as a perfect sphere and hexagonal crystal is coated.

Toner 2 As an external additive, hydrophobic silica (R-81) having an average particle size of 7 nm was used.
2, Nippon Aerosil Co., Ltd.)
A toner was obtained in exactly the same manner as in the above case.

Example 3 Preparation Example of Developer Composition The toners 1 and 2 obtained as described above were mixed with the above carriers 1 to 5 at a 3:97 weight ratio to prepare a developer composition.

Evaluation of Carrier In order to evaluate the electrophotographic characteristics of the carrier, the carriers 1 to 5 were mixed with the toner 1 and the absolute charge amount was measured. The results are shown in Table 1.

Evaluation of developer composition In order to evaluate the effect of adding an external additive, carriers 2 and 4 were used.
The absolute charge amount, the environmental dependency of charge, and the width of the charge distribution were measured for the developer compositions in which the toner compositions Nos. 5 and 5 were mixed with the toner 1 and the developer compositions in which the carrier compositions 1 and 4 were mixed with the toner 2. Table 2 shows the results.

In addition, each evaluation method is as follows. Absolute charge amount: Blow-off charge amount was measured 3 minutes after mixing the toner and the carrier (μC / g). Environmental dependence of charging: (28 ° C., 85% RH) (Charge amount of 10 ° C, 15% RH) Charge distribution width: Charge spectrum graph image analysis value, 20% charge amount Q (20) and 80% of cumulative integration of charge distribution
The value obtained by dividing the difference of the charge amount Q (80) by the 50% charge amount Q (50),
That is, {Q (80)-Q (20)} / Q (50) Table 1 shows that the coating agent contained 0.1% of the nitrogen-containing vinyl monomer.
It can be seen that the absolute charge amount shows a value in an appropriate range when the content is within 2.0% by weight.

From Table 2, it can be seen that when amorphous titania is used as an external additive in a toner containing a polyester resin as a binder resin, a developer composition having excellent development characteristics can be obtained. That is, since the absolute value of the charge amount is in an appropriate range under each environment and the distribution of the charge amount between the toner particles is small, the developer composition has high development efficiency.

Copy test Using a developer composition of developer No. 4, a copying machine (FX4700,
When a copy test was performed by Fuji Xerox Co., Ltd., the temperature range was from high temperature and high humidity (30 ° C., 85% RH) to low temperature and low humidity (10
(° C., 15% RH), the background portion was free of stains, and high-quality images of high density were obtained from the beginning. When 10,000 copies were continuously made, little change in image quality was observed.

(Effect of the Invention) As is clear from the above comparison, the carrier of the present invention has good chargeability, and a developer obtained by combining this carrier with a polyester-based toner and adding amorphous titania as an external additive. The composition has an appropriate charge amount, improves the environmental dependence of charging, has a small charge distribution width, and exhibits excellent development characteristics.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Imai 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. Takematsu Office (56) References JP-A-60-208765 (JP, A) JP-A-64- 35562 (JP, A) JP-A-1-140168 (JP, A) JP-A-62-28772 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/113 G03G 9 / 08

Claims (2)

(57) [Claims] 1. A binary copolymer comprising an acrylate or methacrylate and 0.1 to 2.0% by weight of a nitrogen-containing vinyl monomer, or an acrylate or methacrylate on a surface of a magnetic core material. To 2.0% by weight of a nitrogen-containing vinyl monomer and up to 40% by weight of another monovinyl monomer, provided with a coating layer composed of a terpolymer. Carrier for use. 2. A developer composition comprising: the carrier according to claim 1; and a polyester toner obtained by externally adding amorphous titania fine particles to toner particles containing a polyester resin as a binder resin. Stuff.