JPH01265260A - Positively chargeable toner - Google Patents

Abstract

PURPOSE:To enhance the charge control efficiency of a black toner and a color toner by using a specified charge controller. CONSTITUTION:The entitled toner contains as the charge controller the metal complex of imidazole having a 11-17C long chain alkyl group at the 2-position, preferably, such as compounds represented by formulae I and II in which R2 is said 11-17C long chain alkyl group, such as undecyl or heptadecyl alkyl group; R4 is H or methyl; M is a metal atom; X is an anion; and each of l, m, and n is an integer, thus permitting the obtained metal complex to be white or light in color, accordingly, to be used for the color toner, and to enhance a charging amount of toner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positively charged toner used for developing electrostatic latent images in electrophotography, electrostatic printing, or the like.

Conventional technology Generally, toner for developing electrostatic latent images is made of styrene resin,
After dispersing a coloring agent such as a dye or pigment and a charge control agent to impart positive or negative chargeability to a binder resin such as an epoxy resin or a polyester resin, fine particles with an average diameter of about 10 to 15 μm are dispersed. It is ground and adjusted.

Conventionally, known charge control agents added to positively charged toners include nigrosine dyes, quaternary ammonium salts, and metal salts of higher fatty acids.

Furthermore, as an example of imidazoles being used in toners for developing electrostatic latent images, the use of 2-aminobenzimidazole as a negative charge control agent (Japanese Patent Laid-Open No. 61-2170
No. 55, No. 61-259265), method of using vinyl imidazole in the outer shell of capsule toner (Japanese Patent Application Laid-open No. 187350/1983) 1, method of using vinyl imidazole when using epoxy resin as the binder resin of the toner. There is a description of a method of using it as a curing agent (Japanese Patent Laid-Open Nos. 61-294461 and 62-242960). Furthermore, a method is known in which an imidazole complex is used as a curing accelerator for epoxy resin. (Unexamined Japanese Patent Publication No. 50-1527
9) Problems to be Solved by the Invention Among the conventionally known positive charge control agents, nigrosine dyes are unsuitable for toners of colors other than black because they have poor sustainability of charge control effect and are black in color. Met.

In addition, quaternary ammonium salts or metal salts of higher fatty acids are white or light in color, so they are advantageous for color toners, but their charge control effect is insufficient, making it difficult to obtain a high amount of charge even when added in small amounts. there were.

Various other compounds have been proposed, but none have been found to be of practical use because they all have insufficient charge control effects.

An object of the present invention is to provide a positively charged charge control agent that is white or light in color and is suitable not only for black printing toners but also for color printing and that provides a high charge control effect with a small amount added.

Means for Solving the Problems In view of the above circumstances, the present inventors conducted various tests and researches, and as a result, they found that an imidazole compound having a long-chain alkyl group having 11 to 17 carbon atoms at the 2-position can be used as a charge control agent. The present invention has been accomplished based on the finding that particularly excellent charge control performance is achieved when using a metal complex having as a ligand.

Typical imidazole metal complexes used in the practice of the present invention are those represented by general formula (1) or general formula (II).

The imidazole metal complex represented by the general formula (1) (hereinafter referred to as A-type metal complex) can be synthesized by mixing an imidazole compound and a metal salt in an organic solvent or by heating them briefly.

In this case, the metal salts include silver, copper, and cadmium.

halides of zinc, mercury, nickel or cobalt,
Organic acid salts such as nitrates, sulfates or acetic acid can be used. Among these, hydrochlorides of copper, zinc, nickel or cobalt are particularly suitable. Some of these A-type metal complexes are viscous and liquid at room temperature, but they are unsuitable as charge control agents. Suitable charge control agents have a melting point of 50° C. or higher, excellent thermal stability, and low hygroscopicity.

Among type A metal complexes, some exhibit bright colors depending on the type of metal ion, and are particularly suitable as charge control agents that also serve as colorants for color toners.

The imidazole metal complex represented by the general formula (11) (hereinafter referred to as a B-type metal complex) can be synthesized, for example, by treating an A-type metal complex with an alkaline substance. For example, type A metal complex (Zn
(CzZ)z ) CI2 (mp89~92°C)
By dissolving in methanol and adding slightly excess sodium hydroxide solution to this solution with stirring, type B metal complex (C+ +Z) z Zn (mp 250°C or higher)
can be synthesized.

Type B metal complex does not melt even when heated to 200°C or higher,
Since it is insoluble in most inorganic and organic solvents and exhibits low hygroscopicity, it is suitable as a charge control agent.

Examples of metal complexes of imidazole compounds having a long-chain alkyl group at the 2-position include 2-amylimidazole, 2-hebutylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-tridecylimidazole, 2
Although those having tetradecyl imidazole, 2-heptadecyl imidazole, 2-undecyl-4-methylimidazole, or 2-heptadecyl-4-methylimidazole as a ligand are suitable for practical use, two of these
Imidazole compounds having an alkyl group having 11 to 17 carbon atoms at the 2-position, particularly imidazole compounds having an undecyl group or a heptadecyl group at the 2-position, have been found to have excellent positive charge control performance.

Imidazole gold FJi in the positively charged toner of the present invention
0.1 to 10% by weight preferably 0.5% by weight in the toner.
It is sufficient to add up to 5.0% by weight; if the amount of these compounds is too small, the charge control effect will be low, and if it is too large, the charge control effect will not be stable. Further, in carrying out the present invention, the imidazole metal complex and a conventionally used positive charge control agent such as a nigrosine dye, a quaternary ammonium salt, or a metal salt of a higher fatty acid may be used in combination.

Typical binder resins suitable for carrying out the present invention are copolymer resins of styrene and acrylic ester, and other polystyrene resins.

Polypropylene resin, polyethylene resin, polyamide resin, polyurethane resin, phenolic resin.

Polyester resins, polycarbonate resins, etc., and mixtures of two or more of these can be used.

As the colorant, various known colorants can be used. For example, carbon black or nigrosine dyes are used for black toners, rhodamine pigments or quinacridine pigments are used for red toners, copper phthalocyanine pigments or anthracene derivative dyes are used for blue toners, and benzine yellow is used for yellow toners. It is possible to use colorants.

In carrying out the present invention, known additives that improve image characteristics may be added in addition to the above-mentioned compounds. For example, it may contain a fluidizing agent such as colloidal silica, an abrasive such as strontium titanate and silicon silicon carbide, a lubricant such as metal stearate, and a conductivity imparting agent such as tin oxide.

The positively charged toner of the present invention can be produced by a known method. That is, after appropriately blending the imidazole metal complex, coloring agent, and other additives with the binder resin, the mixture is thoroughly kneaded using a heated roll, kneader, or extruder, and then coarsely and finely crushed to determine the particle size. 4
A toner having an average particle size of 10 to 15 μm can be produced by collecting particles of 5 μm or less, preferably 4 to 20 μm.

The present invention will be specifically explained below using Examples, Reference Examples, and Comparative Examples.

Reference Example Among the metal complexes of long-chain alkylimidazoles in the present invention, C++Z and ZnC1z+ CuCIz ・21
1zO, COCl2.6HzO and NiClz-61
Table 1 shows the properties of the A-type metal complex obtained by putting 1,0 into ethanol at a molar ratio of 2:1, heating for a short time with stirring, distilling off the ethanol, washing and drying.

Table I Properties of various A-type metal complexes of CuZ *1) 5% reduction M temperature indicates the temperature at which 5% of the weight decreases when the temperature is increased at 5°C/win using a thermobalance.

Umbrella 2) Metal content was measured by atomic absorption method.

Next, a slightly excessive amount of sodium hydroxide solution was added to the methanol solution of the type A metal complex shown in Table 1 under stirring, and the precipitated powder was thoroughly washed and dried to obtain a type B metal complex.

However, since the metal complex of C1Z and NiC1z.61hO could not be isolated as a type A metal complex, a type B metal complex was obtained by direct alkali treatment. Also (C.

(C++Z)z ) C1z was decomposed into C0Z and cobalt hydroxide by alkali treatment, and no B-type metal complex was obtained. Table 2 shows the properties of the B-type metal complex obtained.

Table 2 Properties of various B-type metal complexes of C++Z In addition, in the infrared absorption spectrum, the imino group (-NH-) of imidazole was significantly observed in the A-type metal complexes shown in Table 1.
Based on <3140CT11-' vicinity and 3250cm-
Absorption around ' was not observed in the B-type metal complexes shown in Table 2. The metal content of (C++ZL Ni in Table 2) is larger than the theoretical value, which is presumed to be due to the coexistence of by-product nickel hydroxide (N1(Oll)z). This was used in Example 7 as it was.

In addition, 2-heptadecyl imidazole, which is a long chain alkylimidazole other than C, Z (displayed as CI?Z)
Alternatively, 2-undecyl-4-methylimidazole (C
Z4MZ) and zinc chloride (ZnC1g), zinc bromide (ZnBr, ), or zinc iodide (ZnIz)
A-type metal complex and B-type metal complex could be synthesized in a similar manner using halogenated metal salts such as . Table 3
indicates the properties of the compound thus obtained.

Table 3 Various long-chain alkylimidazoles and halogen Example 1
~15 and Comparative Examples 1 to 3 Styrene-acrylic acid ester copolymer resin (manufactured by Fujikura Kasei ■: S-708F) was used as the binder resin, and carbon black #40 (manufactured by Mitsubishi Chemical Industries, Ltd., neutral) was used as the colorant. type) (displayed as CB-1), carbon black MA100 (manufactured by Mitsubishi Chemical Corporation, acidic type)
[Displayed as CB-2] or Lionol Blue F
G7330 (manufactured by Toyo Ink ■, phthalocyanine-based blue pigment) (indicated by F) was used as a charge control agent, and various long-chain alkylimidazole metal complexes shown in the reference examples were finely ground in a mortar and compared. In the example, a commercially available colorless quaternary ammonium salt type positive charging charge control agent was used, and the binder resin 2 coloring agent and charge control agent were mixed in the weight ratio shown in Table 4, and a small mixer was used. The mixture was triblended, then kneaded at a temperature of 130 to 160°C using a twin-screw extruder, cooled after extrusion, and crushed into a plate in a mortar, and further cooled using a tabletop crusher. After finely pulverizing the sample, it was passed through a stainless steel sieve with an opening of 44 μm to prepare a sample, and 1 g of the sample and 25 g of carrier (iron powder or ferrite) were mixed.
into a polyethylene container (100n+j! capacity),
After stirring and shaking on a rotating roll of a roll mill for 5 minutes or 30 minutes, the amount of charge was measured using a blow-off type charge amount measuring device. Furthermore, as a carrier,
Iron powder (DSP-128B manufactured by Dowa Iron Powder+11) or ferrite (F-150 manufactured by Nippon Iron Powder ■) was used.

The method for measuring the amount of charge was to use a sample amount of 200 mg.

The blowing pressure was 1 kg/cd, the measurement time was 25 seconds, and the unit of the measurement value was μC (10-'
expressed in coulombs).

The test results of Examples and Comparative Examples are shown in Table 4 shown in Table 5. Sample compounding ratio and carrier type Table 5. Measurement results of charge amount Effects of the invention By using a charge control agent with a color tone other than white or black, which can provide a high charge control effect with a small amount of addition according to the present invention, it is possible to improve the static charge control agent not only for black printing but also for color printing in particular. It is possible to produce toner for electrophotography.

Claims (5)

[Claims] (1) A positively charged toner comprising, as a charge control agent, an imidazole metal complex having a long-chain alkyl group having 11 to 17 carbon atoms at the 2-position. (2) A positively charged toner containing an imidazole metal complex represented by the following general formula as a charge control agent. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, R_2 is a long-chain alkyl group with 11 to 17 carbon atoms, R_4 is a hydrogen atom or a methyl group, M is a metal atom,
represents an anion, and l, m, and n represent integers. (3) A positively charged toner comprising an imidazole metal complex represented by the following general formula as a charge control agent. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, R_2 is a long-chain alkyl group with 11 to 17 carbon atoms, R_4 is a hydrogen atom or a methyl group, M is a metal atom, n
indicates an integer. (4) A positively charged toner comprising an imidazole metal complex having an undecyl group at the 2-position as a charge control agent. (5) A positively charged toner comprising an imidazole metal complex having a heptadecyl group at the 2-position as a charge control agent.