JPH01262555A - Positively chargeable toner - Google Patents

Abstract

PURPOSE:To obtain a toner suitable not only to black printing but also especially to color printing by forming a white or light color toner, and to obtain a high charge control effect by use of a small amount by incorporating a specified 4,4'-methylene methylene bisimidazole derivative. CONSTITUTION:The toner contains 4,4'-methylene-bis(2-alkyl-5-methylimidazole) represented by formula I in which R2 is an ethyl or undecyl group, in an amount of 0.1-10wt.%, preferably, 0.5-5.0wt.%. If it is added too little, the charge control effect is lowered, and if too much, the effect becomes instable, thus permitting an electrostatic photographic toner not only for black printing but also for color printing to be produced by using such a charge controller.

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 colored particles such as dyes or pigments and a charge control agent for imparting positive or negative chargeability into a binder resin such as epoxy resin or polyester resin, fine particles with an average particle size of 10 to 15 μm are dispersed. It is ground and adjusted.

Conventionally, charge control agents added to positively charged toners include black nigrosine dyes and colorless to light-colored quaternary dyes.
Grade ammonium salts and metal salts of higher fatty acids are known.

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 and No. 61-259265).

A method of using vinyl imidazole in the outer shell of a capsule toner (JP-A-59-187350), a toner using imidazoledicarboxylic acid in combination with a nigrosine dye as a charge control agent (JP-A-61-294461),
A method of using imidazoles as a curing agent when an epoxy resin is used as a binder resin for toner (Japanese Patent Laid-Open No. 6
2-242960).

Problems to be Solved by the Invention Among the conventionally known positive charge control agents, nigrosine dyes have poor sustainability of charge control effect and are black in color, so they are unsuitable for toners of colors other than black. Also,
Quaternary ammonium salts or metal salts of higher fatty acids are
Although it is advantageous for color toners because it is colorless or light-colored, it has been difficult to obtain a high charge amount even by adding a small amount because the charge control effect is insufficient. Various other compounds have been proposed, but are they all charge-controlling? Since the il effect is insufficient, a product that can withstand practical use has not yet been found.

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 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 discovered 4.4°-methylene-bis(2-undecyl-5- By using methylimidazole) [hereinafter referred to as C,,4MZ bis form] or 4,4゛-methylene-bis(2-ethyl-5-methylimidazole) [hereinafter referred to as 2E4MZ bis form], the desired correctness can be achieved. It has been found that a chargeable toner can be obtained.

Cz4MZ bis body or 224M used in the present invention
The Z bis body can be synthesized by the method described in Japanese Patent Publication No. 61-41910 or No. 61-41911, and its melting point is 183°C, 2
Both of the E4MZ bis bodies have a high temperature of 260.5°C, and both are colorless to pale yellow solids, and are odorless, have low hygroscopicity, and have excellent thermal stability.

4,4'-methylene-bis(2-alkyl-5-methylimidazole) in the positively charged toner of the present invention is added in an amount of 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight. If the amount is too small, the charge control effect will be low, and if it is too large, the charge control effect will be unstable.

Furthermore, in carrying out the present invention, 4,4゛-methylene-
Bis(2-alkyl-5-methylimidazole) and a conventionally known 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.

In carrying out the present invention, the binder resin may include polyethylene resin, polypropylene resin, polystyrene resin,
Polyamide resins, polyurethane resins, epoxy resins, phenol resins, polyester resins, polycarbonate resins, etc., or a mixture of two or more of these resins can be used, and copolymer resins of styrene and acrylic ester are particularly suitable. be.

Various known colorants can be used as the colorant.

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 is used for yellow toners. Colorants such as yellow can be used.

In carrying out the present invention, in addition to the above-mentioned compounds, known additives that improve image characteristics may be added. For example, it may contain 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.

The positively charged toner of the present invention can be produced by a known method. That is, 4,4” in the binder resin.
- After appropriately blending methylene-bis(2-alkyl-5-methylimidazole), a coloring agent, and other additives, the mixture is thoroughly kneaded using a hot roll, niegu or extruder, and then coarsely ground and finely milled. After pulverization and a classification step, particles with a particle size of 45 μm or less, preferably 4 to 20 μm, are collected to produce a toner with an average particle size of 10 to 15 μm.

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

Examples 1 to 7 and Comparative Examples 1 to 3 Using styrene-acrylic acid ester copolymer resin (manufactured by Fujikura Kasei ■: S-708F) as the binder resin,
Carbon black #40 (Mitsubishi Chemical Industries ■) as a coloring agent
(manufactured by Mitsubishi Chemical Corporation, neutral type) (displayed as CB-1), carbon black MA100 (manufactured by Mitsubishi Chemical Corporation, acidic type) (
CB-2) or Lionol Blue FG
7330 (manufactured by Toyo Ink σJun, phthalocyanine-based blue pigment) (indicated by F), and Cz as a charge control saving agent.
A 4MZ bis body and a 224MZ bis body were finely pulverized in a mortar, and in a comparative example, a commercially available colorless quaternary ammonium salt type positive charging charge control agent was used. The control agents were blended according to the weight ratio shown in Table 1, tri-blended using a small mixer, and then mixed using a twin-screw extruder to give a weight ratio of 130 to 160
The mixture was kneaded at a temperature of °C, extruded and then cooled to form a plate, which was coarsely crushed in a mortar, and then finely crushed using a tabletop crusher while cooling, and then passed through a stainless steel sieve with an opening of 44 μm. 1 g of the sample and 25 g of carrier (iron powder or ferrite) were placed in a polyethylene container (1 g).
After stirring and shaking for 5 or 30 minutes on a roll mill rotating roll, the amount of charge was measured using a blow-off type charge amount measuring device.

In addition, as a carrier, iron powder (DSP made by Dowa Iron Powder)
-128B) or ferrite (F-1 made by Nippon Steel Powder)
50) was used.

Also, how to measure the amount of charge is a sample! 200+gg, blow pressure 1 kg/ctJ, and measurement time 25 seconds, and the unit of measurement value was expressed in μC (10-' clone) per 1 g of sample.

The test results of Examples and Comparative Examples were as shown in Table 2.

Table 1. Mixing ratio of sample and type of carrier
5Table 2. Measurement result of charge amount ≧ Effect of brightness

Claims (1)

[Claims] (1) 4,4'-methylene- represented by the following general formula
A positively charged toner containing bis(2-alkylimidazole). General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R_2 represents an ethyl group or an undecyl group. ]