Electrostatic toner

Materials used for electrostatic image forming technologies such as electrophotography and electrostatic recording are called electrostatically-padded inks and have a function of selectively attaching to electrostatic latent images for physical development. In addition, there are methods such as electronic toners, electronic printing inks, and developers.

In practical terms, it is classified into a liquid toner (developer) and a powder toner (developer) corresponding to liquids and solids. The general characteristics required for toning inks are: (1) quality stability at high speeds, long-term use; (2) image quality, especially midtone reproduction; (3) color (multi-color) image reproducibility. For powder toning inks, liquid toning inks and color toning inks, they all have their own required characteristics:

Powder toning ink

Usually, it is a kind of fine-particle powder in which a binder such as a pigment and a dye is mixed with a binder such as a resin and an auxiliary agent, and is attached to the surface of a carrier such as a glass ball or an iron powder, and is used in a charged state. The use of powder toning inks mainly involves electrostatic printing, indirect electrophotography, electrostatic recording, and electronic facsimile platemaking and copying, which have attracted widespread attention. New manufacturing methods for powder toning inks are currently under study:

(1) Various necessary ingredients are mixed by a heating roller, a heat roller, and a method such as dissolving to obtain a uniform dispersion, and after cooling, the fine particles are crushed. This is the most common method.
(2) A substance is mixed on a flat plate with a solvent mixed at room temperature to form a film, which is dried and solidified, followed by fine particle grinding. Its disadvantage is that it tends to leave residual solvents and is only suitable for small amounts of production.
(3) Spray dry the mixed dispersion of the preceding paragraph.
(4) The polymerizable monomer, the colorant, and other components are mixed and microparticles are formed after suspension polymerization.
(5) Dissolving the solvent dispersion mixed in the item (2) with a solvent, mixing, and charging a large amount of non-solvent in which the respective components are not dissolved to precipitate as insoluble fine particles.
(6) Dispersions are mixed in a non-solvent state in a dissolving state to disperse them as spherical particles, and the original substance is cooled and solidified, followed by solid-liquid separation.

The powdery toned ink thus obtained generally has the following properties as the main indicators for evaluating the quality:
(1) Chargeability: Charge capacity, polarity, stability, etc.; (2) Graininess: particle shape, maximum (minimum) particle size, particle size distribution; (3) developability: density, paste, ghost, gloss Etc.; (4) Fixability: Melting temperature, solubility, adhesion strength; (5) Image quality: resolution, contrast; (6) Intensity: fatigue phenomenon, powdering.

Liquid color ink

This is made by dispersing a binder such as a dye, a pigment, etc., a resin, and a charge control agent in a highly insulating liquid carrier. It is mainly used for electronic facsimile, and a surface having an electrostatic latent image is immersed in the toner. The dispersion, redispersed and diluted in an excess liquid carrier--a liquid developer or a developer coated on a roller, is selectively attached to the latent image. Then, excess developing ink is removed, and after the liquid carrier is evaporated, the image is fixed on the surface.

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