JPH0325450A - Negative chargeable toner - Google Patents

Abstract

PURPOSE:To obtain an inexpensive charge control agent of a negative charge which is suitable not only as a toner for black printing but also for color printing, is white or pale in color and exhibits a high charge control effect with a smaller amt. of addition by incorporating a specific 4-nitroimidazole compd. as the charge control agent into the toner. CONSTITUTION:This toner contains the imidazole compd. having a nitro group in the 4th position expressed by formula I as the charge control agent. In the formula I, R2 denotes a hydrogen atom or lower alkyl group. The representative 4-nitroimidazole compds. suitable for this compd. are 4-nitroimidazole, 2-methyl-4- nitroimidazole and 2-isopropyl-4-nitroimidazole. The inexpensive charge control agent of the negative charge which is suitable not only as the toner for black printing but also for color printing, is white or pale in color and exhibits the high charge control effect with the smaller amt. of addition is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a negatively charged toner used for developing an electrostatic latent image 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 particle size of about 10 to 15 μm are dispersed. It is ground and adjusted.

In addition, special manufacturing methods include applying mechanochemical reactions to the surface of particles made of binder resin to attach pigments and charge control agents, or adding pigments and charge control agents to the monomers that are the raw materials for binder resin. After dispersing,
A method of producing spherical toner by suspension polymerization reaction is also known.

Conventionally, metal complex salts of monoazo dyes, non-dye metal complexes, and the like are known as charge control agents added to negatively charged toners.

In addition, as an example of an imidazole compound being used in a toner for developing an electrostatic latent image, 2 is used as a negative charge control agent.
- Use of aminobenzoi≧dazole (JP-A-61-21
No. 7055, No. 61-259265), a method of using vinyl ξdazole in the outer shell of a capsule toner (Japanese Patent Application Laid-open No. 187350/1983), and a method of using a curing agent when an epoxy resin is used as a binder resin of the toner. A method using an i5dazole compound as
No. 94461, No. 62-242960).

Problems to be Solved by the Invention Among conventionally known negative charge control agents, metal complexes of monoazo dyes, metal complexes of salicylic acid, naphthoic acid, cobalt, chromium, iron, etc. of dicarboxylic acids, etc. generally have a structure of has complex and strong coloring properties, making it unsuitable for toners of colors other than black; it also deteriorates due to decomposition during heat kneading or changes in temperature and humidity during storage; charge controllability tends to vary; Since it is extremely difficult to disperse it in a thermoplastic resin, it is difficult to obtain a toner with stable and uniform charging properties.

In addition, 2-anobenzoi≧dazole compounds are colorless and therefore advantageous for use as latners, but these compounds lack productivity and have the problem of high cost.

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

Means for Solving the Problems In view of the above circumstances, the present inventors have conducted various tests and studies, and as a result, they have developed an Izumi Dazur compound having a nitro group at the 4-position represented by the following general formula as a charge control agent. It has been found that when a metal complex having a nitro group at the 4-position represented by the general formula or the general formula below is used as a ligand, it has excellent charge control performance, and the present invention completed.

Representative 4-nitroimidazole compounds suitable for the practice of this invention include 4-nitroigodazole, 2-methyl-4-nitroigodazole, and 2-isobrovir-4-
Nitroimidazole, these are commercially available;
readily available. Further, the metal complex of the imidazole compound suitable for carrying out the present invention can be easily obtained by reacting the 4-21-loimidazole compound and metal salts in the presence of an alkali in an aqueous solvent, and a typical 4-
Examples of metal complexes of nitroimizole include nickel metal complexes, copper metal complexes, cobalt metal complexes, and zinc metal complexes of 4-nitroimidazole, 2-methyl-4-nitroidazole, or 2-isopropyl-4-nitroigodazole. be.

The 4-nitroimidazole compound used in the present invention is milky white to yellowish white and can be used for color toners.

In addition, all 4-nitroimidazole compounds have high melting points, and these metal complexes have even higher melting points, so
Since it has excellent thermal stability and low hygroscopicity, it is suitable as a charge control agent.

The 4-nitroimidazole compound and the metal complex thereof in the negatively charged toner of the present invention are contained in the toner in an amount of 0.5 to
10% by weight preferably i.p. o ~ 5.0% by weight should be added, and if these amounts are small, the amount of charge on the toner will be insufficient, and on the other hand, if it is too large, the amount of charge on the toner will change over time, making it difficult to control the charge. The effect becomes unstable. Furthermore, in carrying out the present invention, a 4-nitroimidazole compound or a metal complex thereof may be used in combination with a conventionally used negatively charged charge control agent.

Typical binder resins suitable for carrying out the present invention are copolymer resins of styrene and acrylic esters, and other binder resins include polystyrene resins, polypropylene resins, polyethylene resins, boria ξ resins, polyurethane resins, and phenol resins. Resins, 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 dye for black toner, rhodium pigment or quinacridine dye for red toner, copper cyanine pigment or anthracene derivative dye for blue toner, and copper cyanine pigment or anthracene derivative dye for yellow toner. It is possible to use a coloring agent such as benzine yellow.

Furthermore, the negatively charged toner of the present invention can also be used as a magnetic toner by containing a magnetic material. The magnetic materials added to the magnetic toner include iron oxide, iron, cobalt, etc. such as magnetite, hematite, and ferrite.
Metals such as nickel or alloys containing these metals. These magnetic materials preferably have an average particle size of about 0.1 to 2 μm, and the amount contained in the toner is as follows:
40 to 150 per 100 parts by weight of binder resin
Parts by weight are appropriate.

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

The negatively charged toner of the present invention can be prepared by a known method. The most common method is to mix a 4-nitroimidazole compound or a metal complex thereof, a coloring agent, and other additives with a binder resin, and then thoroughly heat the mixture using a hot roll, a roller, an extruder, etc. Knead, coarsely crush, and finely crush particles with a particle size of 45 μm or less, preferably 4 to 20 μm, and collect particles with an average particle size of 10-15 μm.
It is sufficient to set it to μm.

The present invention will be specifically explained below with reference to Examples and Reference Examples.

Reference Example 4 - Nitroigodazole 11.3g (0.10mol)
, 93% sodium hydroxide 4.3g (0.10mol)
While stirring a solution consisting of and 120 d of water at room temperature,
To this, 11.9 g of cobalt chloride (n) hexahydrate
A solution consisting of (0.050 mol) and 50 mol of water was added and stirred for an additional 30 minutes. After the reaction, the precipitate was collected by filtration and washed with water.
4-Nitro-cobalt (II) 11
．． 9 g (0.042 mol, yield 84%) was obtained.

Similarly, bis(4-nitro5dazolato)nickel (■), bis(4-nitroydazolato)copper (■)
, bis(2-methyl-4-nitro-dazolato) cobalt (■), bis(2-isoprobyl-4-nitro-dazolato) zinc (It), bis(2-isoprobyl-4-
Nitroimidazolate) nickel(II) was prepared.

Examples 1 to 13 Styrene-acrylic acid ester copolymer resin (manufactured by Fujikura Kaei ■: S-7 08F) as a binder resin, carbon black (manufactured by Mitsubishi Kakai Industries, Ltd., MA) as a coloring agent
IOO), 4-nitroimidazole (
BASF ■), 2-methyl-4-nitroimidazole (Orient Chemical Industry ■), 2-isobrovir-4-
Using nitro fruit dazole (manufactured by BASF ■) and the imidazole metal complex shown in the reference example, 100 parts by weight of these binder resins, 5 parts by weight of a coloring agent, and a charge control agent as shown in Table 1 were blended. Dry blended using a ξ mixer and then using a twin screw extruder to
The mixture was kneaded at a temperature of 160°C, extruded and then cooled to form a plate, which was coarsely crushed in a mortar, then finely crushed using a tabletop crusher while cooling, and then passed through a stainless steel sieve with an opening of 44 μm. A sample was prepared by

1 g of the sample and 25 g of iron powder (manufactured by Dowa Iron Powder ■; DSP-128B) as a carrier were placed in a polyethylene wide-mouth bottle with a capacity of 100 Id, stirred and shaken on a rotating roll of a roll mill for 5 or 30 minutes, and then blow-off. The amount of charge was measured using a type charge amount measuring device, and the results were as shown in Table 1.

The measurement conditions for the amount of charge are as follows: Mixture 2 of sample and carrier
00mg, blow pressure 1kg/c4, measurement time 25 seconds, and the unit of measurement value is μC (10-") per 1g of sample.
expressed in coulombs).

Table 1. Sample composition and charge amount measurement results Effects of the invention

Claims (2)

[Claims] (1) A negatively charged toner characterized by containing a 4-nitroimidazole compound represented by the following general formula as a charge control agent. General formula ▲ Numerical formula, chemical formula, table, etc. are available ▼ [In the formula, R_2 represents a hydrogen atom or a lower alkyl group. ] (2) A negatively charged toner comprising a metal complex of a 4-nitroimidazole compound represented by the following general formula as a charge control agent. General formula ▲ Numerical formula, chemical formula, table, etc. are available ▼ [In the formula, R_2 represents a hydrogen atom or a lower alkyl group, and M represents nickel, copper, cobalt, or zinc. ]