JPH07117776B2 - Positively charged toner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positively chargeable toner used for developing an electrostatic latent image in electrophotography, electrostatic printing or the like.

2. Description of the Related Art Generally, a toner for developing an electrostatic latent image is a styrene resin,
After dispersing a colorant such as a dye or a pigment and a charge control agent for imparting positive or negative chargeability to a binder resin such as an epoxy resin or a polyester resin, the average particle diameter is reduced to about 10 to 15 μm. It is crushed and adjusted.

Conventionally, as a charge control agent added to a positively chargeable toner, a nigrosine dye, a quaternary ammonium salt, a metal salt of a higher fatty acid, or the like is known.

Further, as an example in which imidazoles are used in a toner for developing an electrostatic latent image, use of 2-aminobenzimidazole as a negative charge control agent (JP-A-61-217055,
No. 61-259265), a method of using vinylimidazole as the outer shell of a capsule toner (Japanese Patent Laid-Open No. 59-187350), and using imidazoles as a curing agent when an epoxy resin is used as a binder resin of the toner. There is a description of the method (Japanese Patent Application Laid-Open Nos. 61-294461 and 62-242960). Further, a method of using an imidazole complex as a curing accelerator of an epoxy resin is known. (Japanese Patent Publication 50-152
(Patent No. 79) Problems to be Solved by the Invention Among conventionally known positive charge control agents, nigrosine dyes are not suitable for color toners other than black because they have poor sustainability of charge control effect and are black. Met.

Further, a quaternary ammonium salt or a metal salt of a higher fatty acid is advantageous for color toners because it is white or light in color, but it is difficult to obtain a high charge amount by adding a small amount because of insufficient charge control effect. there were.

Other various compounds have been proposed, but none of them have been found to be practically applicable because of their insufficient charge control effect.

It is an object of the present invention to provide a positively-charged charge control agent which is suitable not only for black printing toner but also for white or light color particularly suitable for color printing and which can obtain a high charge control effect with a small addition amount.

Means for Solving the Problems The present inventors have conducted various test studies in view of such circumstances, and as a result, as a charge control agent, the second position has 11 to 12 carbon atoms.
The present inventors have completed the present invention by discovering that when a metal complex having an imidazole compound having 17 long-chain alkyl groups as a ligand is used, particularly excellent charge control performance is provided.

A typical imidazole metal complex used in the practice of the present invention has the general formula (I) Or general formula (II) Is represented by.

The imidazole metal complex represented by the general formula (I) (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 heating the mixture for a short time. At that time, as metal salts,
Organic acid salts such as silver, copper, cadmium, zinc, mercury, nickel or cobalt halides, nitrates, sulfates or acetic acid can be used. Of these, especially copper,
Zinc, nickel or cobalt hydrochlorides are suitable.
Depending on the type of these A-type metal complexes, there are liquid ones that are viscous at room temperature, but they are unsuitable as charge control agents. Suitable as the charge control agent is one having a melting point of 50 ° C. or higher, excellent thermal stability and low hygroscopicity.

Some of the A-type metal complexes exhibit vivid colors depending on the type of metal ions, and are particularly suitable as a charge control agent that also serves as a colorant for color toners.

The imidazole metal complex represented by the general formula (II) (hereinafter referred to as B
Type metal complex) can be synthesized, for example, by treating the type A metal complex with an alkaline substance. For example, an A type metal complex [Zn (C ₁₁ Z) obtained from 2-undecylimidazole (denoted as C ₁₁ Z) and zinc chloride]
₂ ] Cl ₂ (mp 89 to 92 ° C.) was dissolved in methanol, and a slight excess of sodium hydroxide solution was added to this solution with stirring to give a B-type metal complex (C ₁₁ Z) ₂ Zn (mp 250 ° C. or higher). Can be synthesized.

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

Examples of the metal complex of an imidazole compound having a long-chain alkyl group at the 2-position include 2-amylimidazole, 2-heptylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-tridecylimidazole, 2-tetradecylimidazole, Although 2-heptadecylimidazole, 2-undecyl-4-methylimidazole or 2-heptadecyl-4-methylimidazole as a ligand is suitable for practical use, an alkyl group having 11 to 17 carbon atoms at the 2-position An excellent positive charge control performance is recognized for an imidazole compound having ## STR3 ##, particularly for an imidazole compound having an undecyl group or a heptadecyl group at the 2-position.

The imidazole metal complex in the positively chargeable toner of the present invention may be added to the toner in an amount of 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight. If the blending amount of these is too small, the charge control effect becomes low and too large. And the charge control effect becomes unstable. Further, in carrying out the present invention, a nigrosine-based dye conventionally used with an imidazole metal complex,
You may use together positive charge control agents, such as a quaternary ammonium salt or a metal salt of a higher fatty acid.

A typical binder resin suitable for carrying out the present invention is a copolymer resin of styrene and an acrylic ester, and other polystyrene resins, polypropylene resins, polyethylene resins, polyamide resins, polyurethane resins, phenol resins, polyesters. Resins, polycarbonate resins, and the like, and two or more of them may be mixed and used.

As the colorant, various known colorants can be used. For example, carbon black or nigrosine dye for black toner, rhodamine pigment or quinacdrine pigment for red toner, copper phthalocyanine pigment or anthracene derivative dye for blue toner, and benzine yellow for yellow toner. The use of colorants is possible.

In the practice of the present invention, known additives for improving image characteristics may be added in addition to the above compounds. For example, a fluidizing agent such as colloidal silica, an abrasive such as strontium titanate and silicon carbide, a lubricant such as metal stearate, and a conductivity-imparting agent such as tin oxide may be contained.

The positively chargeable toner of the present invention can be manufactured by a known method. That is, after appropriately blending the imidazole metal complex, the colorant and other additives to the binder resin, kneading is sufficiently performed using a hot roll, a kneader or an extruder, and then coarse pulverization and fine pulverization are performed to obtain a particle diameter of 45.
A toner having an average particle size of 10 to 15 μm can be produced by collecting particles of μm or less, preferably 4 to 20 μm.

Hereinafter, the present invention will be specifically described with reference to Examples, Reference Examples and Comparative Examples.

Reference Example Among the metal complexes of long-chain alkylimidazoles in the present invention, C ₁₁ Z and ZnCl ₂ , CuCl ₂ · 2H ₂ O, CoCl ₂ · 6H ₂ O and NiCl ₂
・ Characteristics of A-type metal complex obtained by adding 6H ₂ O in ethanol at a molar ratio of 2: 1 and heating for a short time under stirring, distilling off ethanol, washing and drying are shown in Table 1. .

However, since the A-type metal complex could not be isolated from the metal complex of C ₁₁ Z and NiCl ₂ .6H ₂ O, a B-type metal complex was obtained by direct alkali treatment. Also, [Co (C ₁₁ Z) ₂ ] Cl ₂ is decomposed into C ₁₁ Z and cobalt hydroxide by alkali treatment,
No B-type metal complex was obtained. Table 2 shows the properties of the obtained B-type metal complex.

In the infrared absorption spectrum, the absorptions at 3140 cm ^-1 and 3250 cm ^-1 near the 3140 cm ^-1 and 3250 cm ^-1 based on the imino group (-NH-) of imidazole, which were remarkably observed in the A-type metal complex shown in Table 1, were shown by B in Table 2. It was not observed in the type metal complex. Of Table 2
The metal content of (C ₁₁ Z) ₂ Ni is higher than the theoretical value, which is presumed to be due to the coexistence of nickel hydroxide (Ni (OH) ₂ ) as a by-product. This product is as it is in Example 7.
Used in.

In addition, 2- which is a long-chain alkylimidazole other than C ₁₁ Z
Heptadecyl imidazole (denoted as C ₁₇ Z) or 2-undecyl-4-methyl imidazole (denoted as C ₁₁ 4MZ) and zinc chloride (ZnCl ₂ ), zinc bromide (ZnBr ₂ ) or zinc iodide (ZnI) It was possible to synthesize the A-type metal complex and the B-type metal complex by the same method using the metal halide salt such as ₂ ). Table 3 shows the properties of the compounds thus obtained.

Examples 1 to 15 and Comparative Examples 1 to 3 Styrene-acrylic ester copolymer resin (S-708F manufactured by Fujikura Kasei Co., Ltd.) was used as a binder resin, and carbon black # 40 (Mitsubishi Kasei Co., Ltd.) was used as a colorant. (stock)
Made, neutral type) [labeled as CB-1], carbon black MA100 (made by Mitsubishi Kasei Co., Ltd., acidic type) [CB-2
Or [Lionol Blue FG7330 (Phthalocyanine blue pigment manufactured by Toyo Ink Co., Ltd.) [denoted as F] and various metal complexes of long-chain alkylimidazole shown in Reference Example as a charge control agent are mortared. Table 4 shows the binder resin, the colorant, and the charge control agent in the comparative example, using a commercially available colorless quaternary ammonium salt type charge control agent for positive charge. Blended in different weight ratios, dry blended in a small mixer, then used a twin-screw extruder to
After kneading at a temperature of ~ 160 ° C, extruding and cooling it into a plate, crush it in a mortar, then pulverize it with a desktop crusher while cooling, and then use a stainless steel sieve with a 44 μm opening. A sample is made by passing it through, and 1 g of the sample and 25 g of carrier (iron powder or ferrite) are added to a polyethylene container (100
(ml volume), the mixture was shaken with stirring on a rotating roll of a roll mill for 5 minutes or 30 minutes, and then its charge amount was measured using a blow-off type charge amount measuring device. As the carrier, iron powder (DSP-128B manufactured by Dowa Iron Powder Co., Ltd.) or ferrite (F-150 manufactured by Nippon Iron Powder Co., Ltd.) was used.

The method of measuring the charge amount was 200 mg of sample, 1 kg / cm ^{2 of} blow pressure, and 25 seconds of measuring time, and the unit of the measured value was μC (10 ⁻⁶ coulomb) per 1 g of the sample.

The test results of Examples and Comparative Examples are shown in Table 5.

The commercial product used in Comparative Example 3 was a charge control agent for colorless positive charge (product name: BON, manufactured by Orient Chemical Co., Ltd.).
TRON P-51).

EFFECTS OF THE INVENTION By using a charge control agent having a color tone other than white or black, which can obtain a high charge control effect by adding a small amount according to the present invention, it is possible to obtain a toner for electrostatic photography not only for black printing but also for color printing. It can be manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 61-294461 (JP, A) JP-A 59-187350 (JP, A) JP-A 48-79300 (JP, A)

Claims (2)

[Claims] 1. A positively chargeable toner containing an imidazole metal complex represented by the following general formula as a charge control agent. General formula 2. A positively chargeable toner containing an imidazole metal complex represented by the following general formula as a charge control agent. General formula