JPH0440472A - Carrier for magnetic blush development and developer composition - Google Patents

Abstract

PURPOSE:To eliminate the reduction of a charging quantity and the occurrence of the stain inside a machine by processing the surface of a magnetic core material with a specified copolymer mixture and forming a covered layer on the surface of the core material. CONSTITUTION:The magnetic core material is covered with an acrylic acid ester or methacrylic ester copolymer incorporating 0.1-2.0 wt.% of N-containing vinyl monomer. When the ratio of the N-containing vinyl monomer is lower than 0.1 wt. %, the absolute value of the charging quantity is low and the stain in the in a reproduction machine occurs, and in the case of higher than 2.0 wt.%, the absolute value of the charging quantity is higher than a proper range under a low temp. and low humidity and the reduction of the image density is caused. Thus, the improved resistance to the surface contamination and the improved charge capacity are obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a carrier for magnetic brush development and a developer composition used for developing electrostatic latent images in electrophotography and electrostatic recording. Regarding.

(Prior art) In electrophotography, a photoconductive substance such as selenium is used as a photoreceptor, an electrostatic latent image is formed using various means, and a magnetic brush development method is applied to the electrostatic latent image. Generally, a method is adopted in which the toner is deposited on the toner using a method such as the like, and the image is visualized.

In the magnetic brush development method, carriers used to apply an appropriate amount of positive or negative electricity to l-ner are generally classified into coated carriers and non-coated carriers, but developer life is taken into consideration. In this case, the former is superior, and 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 inorganic powder such as silica for the purpose of improving the powder fluidity of toner.

(Problems to be Solved by the Invention) There are various properties required of the coated carrier, but particularly important properties include appropriate charging properties, impact resistance, abrasion resistance, and the relationship between core strength and coating layer. Good adhesion, uniformity of charge distribution, etc. can be achieved.

Considering the above-mentioned characteristics, the coated carriers used in the past still have problems to be improved, and no perfect solution is known at present. For example, as a coating material, fluorinated vinyl polymers have excellent surface stain resistance or have problems with adhesion with the core shrine, while acrylic polymers have poor mechanical strength and adhesion with the core shrine. Although it can be applied as well as tSi, there are problems in surface dyeing resistance and charging properties. In any case, the current situation is that we are forced to use coating materials that have advantages and disadvantages.

On the other hand, in the case of a developer using a polyester resin as a binder resin, the toner has the disadvantage that the charge amount fluctuates greatly due to changes in the environment and also exhibits a wide charge distribution.

Furthermore, when adding external additives such as phosphoric acid to l-ner, the area where the effect of improving powder fluidity is expressed (coverage rate 100
%), there is also the problem that the environmental dependence of the developer's charge is greatly reduced.

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

The purpose of the present invention is to exhibit good charging properties, good environmental dependence of charging, and no reduction in the amount of charging during running, and as a result, no early fogging or internal contamination. An object of the present invention is to provide a carrier for magnetic brush development.

Another object of the present invention is to provide a developer having excellent development properties.

(Means for Solving the Problem) As a result of various studies and examinations in order to improve the above-mentioned drawbacks in the conventional technology, the present inventors have found that by using a specific coating material, the above-mentioned coated carrier can meet the requirements. The developer composition in combination with the carrier and a toner containing polyester as a binder resin exhibits excellent development properties, especially when certain external additives are added. The present inventors have discovered that the amount of charge is within an appropriate range, the environmental dependence of charge is excellent, and the charge distribution is sharp, leading to the completion of the present invention.

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

That is, the carrier of the present invention has a coating layer made of an acrylic ester or methacrylic ester copolymer having a nitrogen-containing vinyl monomer content of 0.1 to 2.0% by weight on the surface of the magnetic core material. Features.

Further, the developer composition of the present invention is characterized in that it consists of the above-mentioned carrier and a polyester toner made by externally adding amorphous titania fine particles to L-ner particles containing a polyester resin as a binder resin.

The present invention will be explained in detail below.

Examples of the four-magnetic core material (hereinafter simply referred to as core material) used in the present invention include powders such as iron powder, iron oxide powder, carbonyl iron powder, magnetite powder, nickel, and ferrite.

Usually, a carrier having a particle size of 10 to 500,711+1 is used.

In the nitrogen-containing vinyl monomer-containing acrylic ester or methacrylic ester copolymer used for coating the surface of the core material, examples of the nitrogen-containing vinyl monomer include 2-vinylpyridine, 4-vinylpyridine, 2-vinyl-6- Methylpyridine, 2-vinyl-5-methylpyridine, 4-butenylpyridine, 4-pentenylpyridine,
N-vinylpiperidine, 4vinylpiperidine, N-vinyldihydropyridine, N-vinylpyrrole, 2-vinylpyrrole, N-vinylpyrroline, N-vinylpyrrolidine, 2-vinylpyrrolidine, N-vinyl-2-pyrrolidone, N-vinyl -2-piperidone, N-vinylcarbazole, N-vinylmorpholine, etc. are used. These can be used alone or in combination of two or more.

The copolymerization ratio of these nitrogen-containing vinyl monomers needs to be in the range of 0.1 to 2.0% by weight based on the total weight of the copolymer. When the proportion of the nitrogen-containing vinyl monomer is lower than 0.1% by weight, the absolute value of the amount of charge decreases, causing toner contamination within the copying machine. Moreover, if it exceeds 2.0% by weight, the absolute value of the charge amount will be higher than the appropriate range, especially under low temperature and low humidity, resulting in a decrease in image density. Furthermore, the dependence of charging on the environment increases.

On the other hand, acrylic esters and methacrylic esters include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol,
Alkyl alcohols such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadenyl alcohol, methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethyl alcohol, etc. Esters with alkoxyalkyl alcohols such as ethoxyethyl alcohol, methoxypropyl alcohol, and ethoxypropyl alcohol, aralkyl alcohols such as benzyl alcohol, phenylethyl alcohol, and phenylpropyl alcohol, and alkenyl alcohols such as allyl alcohol and crotonyl alcohol. can give. Among these, preferred are acrylic acid alkyl esters and methacrylic acid alkyl esters.

In the present invention, it is also possible to further copolymerize other vinyl monomers, if desired. Such vinyl monomers include styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene,
Alkylstyrenes such as butylstyrene, hexylstyrene, heptylstyrene, octylstyrene, halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dipromostyrene, iodostyrene, and styrenes such as nitrostyrene, acetylstyrene, methoxystyrene, etc. Monomer; acrylic acid, methacrylic acid, α
- Addition-polymerizable unsaturated aliphatic monocarboxylic acids such as ethyl acrylic acid, crotonic acid, α-methylcrotonic acid, α-ethylcrotonic acid, isocrotonic acid, tiglic acid, ungellic acid, maleic acid, fumaric acid, itaconic acid, Addition-polymerizable unsaturated aliphatic dicarboxylic acids such as citraconic acid, mesaconic acid, glutaconic acid, and dihydromuconic acid; Esters, amides, and nitriles of the above carboxylic acids other than acrylic acid and methacrylic acid esters; Ethylene, propylene, butene, isobutylene, etc. Aliphatic monoolefin; vinyl chloride, vinyl iodide, 1,2-dichloroethylene, ], ]2
Examples include halogenated aliphatic olefins such as -dibromoethylene 1,2-short ethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride, and vinylidene fluoride. The amount of these optionally copolymerized vinyl monomers 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 to of 000 to 200,000, particularly 50,000 to 1.00,000. Those within the range of are preferably used. The number average molecular weight is 1
If it is less than 0,000, the coating layer may peel off from the core material in the copying machine, and if it is less than 200,000
If it is higher than that, it becomes difficult to cover the core system.

In the electrophotographic carrier of the present invention, a magnetic core material as described above is surface-treated with a copolymer mixture as described above, and a coating layer of the copolymer mixture is formed on the surface of the core material by chemical bonding or adsorption. You can get it.

The surface treatment of the core material can be carried out, for example, by dissolving the above-mentioned copolymer mixture in a suitable solvent, mixing it with the core material, and drying the solution.

The amount of the copolymer coated is preferably such that a coating layer having a thickness of 0.5 knots or less is formed on the surface of the core material. If the film thickness exceeds 0.5 an, the resistance of the carrier increases, causing a problem that the bulk image density decreases, so the film thickness is desirably 0.5 an or less.

The electrophotographic carrier of the present invention obtained in this way is
It is mixed with a toner and used as a developer composition for a magnetic brush for developing electrostatic latent images.

Toners to be used in combination with the above carriers include:
Any known toner in which a colorant is dispersed in a binder resin can be used. However, as a binder resin,
When using a toner made of polyester resin, adding amorphous titania as an external additive improves the wide charge distribution inherent in polyester resin at low temperatures and low humidity, and the amount of charge under high temperature and high humidity. It is preferable because it has a remarkable effect of improving problems such as low height.

Polyester resins used as binder resins include:
For example, a linear polyester resin made of a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components can be preferably used.

More specifically, it is a linear polyester obtained from terephthalic acid/bisphenol A ethylene oxide adduct/cyclohexanedimethanol, and has a softening point of 100 to
125℃, glass transition point 55-68℃, number average molecular weight (
3,3±0.3)X 103, weight average molecular weight (9,
1±(1,4)X103, acid value 6-12, hydroxyl value 25
Resins having a molecular weight of 40 to 40 are particularly preferably used.

As for amorphous titania used as an external additive,
Those treated with a coupling agent are preferred. The treated amorphous titania fine particles have a higher surface hydroxyl value, are more active, and have higher reactivity with the coupling agent than crystalline ones, and this results in a high charge amount on the toner. It becomes possible to give. Moreover, the particle size is -order particle size 1. ．． Off, preferably 0.3 or less, is used.

The amount added is 0.1 wL% to 2,000 wL% to the toner.
A range of Owt% is preferred.

(Example) Example 1 Carrier Preparation Example Carrier 1 (Comparative Example) As a coating agent, 20% by weight of styrene, 75.0% by weight of methyl methacrylate, and 5% by weight of 4-vinylpyridine.
．． Nitrogen-containing methacrylate copolymer (M
n=50,00(1,My-1(1(1,(1(1(1)
) was used to prepare a 20% solution by dissolving it in toluene.

The resulting solution was used as a coating solution.

As a core material, Cu-Zn-based ferrite carrier particles (P-100, manufactured by Powdertic Co., Ltd.) with an average particle size of 120
Apply the above coating solution to the core material at a rate of 1
．． 2 parts by weight were added, mixed in a kneader, dried and sieved to obtain a coated carrier with a film thickness of 0.25.

Carrier 2 (present invention) As a coating agent, 20% by weight of styrene, 78.0% by weight of methyl methacrylate and 4-vinylpyridine 2
．． Nitrogen-containing methacrylate copolymer (M
n-50,000, My-100,000) and dissolved in toluene to prepare a 20% solution. Using the obtained solution as a coating solution, a coated carrier was obtained in the same manner as in the case of carrier 1.

Carrier 3 (present invention) As a coating agent, 20% by weight of styrene, 79.0% by weight of methyl methacrylate and 4-vinylpyridine 1
．． Nitrogen-containing methacrylate copolymer (M
using rr50,000, My-100,000),
A 20% solution was prepared by dissolving in toluene. Using the obtained solution as a coating solution, a coated carrier was obtained in the same manner as in the case of carrier 1.

Carrier 4 (present invention) As a coating agent, 20% by weight of styrene, 79.9% by weight of methyl methacrylate, and 0% by weight of 4-vinylpyridine.
．． Nitrogen-containing methacrylate copolymer consisting of 1% by weight (number average molecular weight Mrr 50,000, weight average molecular weight MW
-100, (10(1)), dissolved in toluene and 2
A 0% solution was prepared. Using the obtained solution as a coating solution, a coated carrier was obtained in the same manner as in the case of carrier 1.

Carrier 5 (Comparative Example) As a coating agent, a copolymer (M
rr50,000, Mv=1-00,000) was used and dissolved in toluene to prepare a 20% solution. The obtained solution was used as a coating solution to obtain a coated carrier in the same manner as in the case of Carrierco.

Example 2 Toner creation example Toner 1 Polyester resin (trade name Niplas Deck S-1000 manufactured by Dainippon Ink ■) (Mrr4,000, My-1,0,000)
95 parts by weight of carbon black (#4000 manufactured by Mitsubishi Kasei ■) 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 size of 9 tung.

Amorphous titania (trade name:
Ultra Fine Powder (manufactured by Idemitsu Kosan ■) (surface treated with a low-molecular-weight silane coupling agent to make it hydrophobic) was added and mixed using a Henschel mixer. The amount of amorphous titania added was such that the surface of the toner was covered with 100% coverage. Note that the coverage rate refers to the coverage rate when the external additive is regarded as a perfect sphere and the surface is covered with hexagonal crystals.

Toner 2 Hydrophobic silica (R-
A toner was obtained in exactly the same manner as in the case of Toner 1, except that Toner 812 (manufactured by Nippon Aerosil Co., Ltd.) was used.

Example 3 Example of Preparation of Developer Composition Toners 1 and 2 obtained as described above were mixed in a weight ratio of 297 to 1 to 5 and 3 to prepare a developer composition.

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

Evaluation of developer compositions In order to evaluate the effect of adding external additives, developer compositions were prepared in which carriers 2.4 and 5 were mixed with toner], and developer compositions in which carriers 1 and 4 were mixed with toner 2. The absolute charge amount, environmental dependence of charge, and width of charge distribution were measured. The results are shown in Table 2.

The evaluation methods are as follows: Absolute charge amount: The blow-off charge amount was measured 3 minutes after mixing the toner and carrier (μC/g) Environmental dependence of charge: (28°C) , 85% R1 (charge amount) (10
℃, 15%R11 charge amount) Width of charge distribution...Charge spectrum graph image analysis value, 20% charge amount Q (2
0) and 80% charge amount Q (80) is the 50% charge amount Q
The value divided by (5(]), that is, fQ (80) −
Q (20) l / Q (50) Margin Table 1 From Table 1, it can be seen that the nitrogen-containing vinyl monomer in the coating agent is 0.1
When it contains ~2.0% by weight, the absolute charge amount is
It can be seen that the values are in an appropriate range.

8]-7 Table 2 shows that when amorphous titania is used as an external additive in a toner containing polyester resin as a binder resin, a developer composition exhibiting excellent development characteristics can be obtained. I understand. That is, the absolute value of the charge amount is within an appropriate range under each environment, and the distribution of the charge amount among the toner particles is small, resulting in a developer composition having high development efficiency.

Using the developer composition of copy test developer No. 4, a copying machine (FX
4700, manufactured by Fuji Xerox ■), there were no stains on the background under conditions ranging from high temperature and high humidity (30°C, 85% R1+) to low temperature and low humidity (10°C, 15% R11), and there was no stain from the beginning. High-density, high-quality images were obtained. Furthermore, when I made continuous copies of to, ooo sheets,
Almost no change in image quality was observed.

(Effects of the Invention) As is clear from the above comparison, the carrier of the present invention has the following advantages:
The developer composition that combines this carrier with a polyester toner and has amorphous titania added as an external additive has an appropriate amount of charge and has improved environmental dependence of charge. In addition, the width of the charge distribution is small and exhibits excellent development characteristics.

Patent applicant: Fuji Xerox Co., Ltd. Agent: Patent Attorney Tsuyoshi Nagabe

Claims (2)

[Claims] (1) A carrier characterized in that a coating layer made of an acrylic ester or methacrylic ester copolymer having a nitrogen-containing vinyl monomer content of 0.1 to 2.0% by weight is provided on the surface of a magnetic core material. (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.