Liquid digital printing ink

Liquid digital printing inks are often used for ink jet printing. The type of ink is related to the structure of ink heads of ink jet printers. The ink heads can be divided into two types: thermal compression type and piezoelectric type. Piezoelectric type is divided into high precision and low precision, such as EPSON. The inkjet head is a high-precision product, while Xaar and Spectra's inkjet heads are less accurate, with the former mostly using water-based inks and the latter mostly using solvent-based inks.

1. Composition and performance of water-based ink

Water-based inks are mainly composed of solvents, colorants, surfactants, pH regulators, driers, and other additives. For hot-press inkjet printing systems, only aqueous inks can be used; on-demand ink-jet printing inks are also commonly used. Water-based ink.

(1) Colorant

Dyes are mainly used as the colorant for water-based inks, because for aqueous inks, the dyes can be completely dissolved in a solvent and fuse well with the solvent in the form of macromolecules to exhibit good colorability. Such as azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, quinoneimine dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes A phthalocyanine dye or a metal phthalocyanine dye, with an oil-soluble dye being particularly preferred.

For pigmented water-based inks, because the pigment is insoluble in the solvent, it is necessary to ensure its dispersion stability in the solvent and the color effect also requires other components and higher technical requirements. Pigments are divided into inorganic pigments and organic pigments, including carbon black, chrome red, molybdenum red, chrome yellow, titanium yellow, chromium oxide, Viridian pigments, titanium cobalt green, ultramarine blue, cobalt blue, diketopyrrolopyrrole Indole, quinone, benzimidazolone, indenopyrimidine, and azo, phthalocyanine, strychnine, perylene ketones, sulfhydryls, quinophthalones, metal complex pigments, and the like.

The pigment or dye may be used alone, or two or more kinds of pigments or dyes may be used in combination. The average diameter of the pigment particles is preferably 50 to 500 nm, and the content thereof is appropriately selected depending on the use of the ink or the printing property, and is the total weight of the ink. 1.0% to 10.0%.

(2) Solvent

Water-based ink solvent is generally deionized water as the main solvent, and then add an appropriate amount of organic solvent, the organic solvent content is 0.1% to 1.0% of the total weight of the ink, mainly using the following categories.

Polyhydric alcohols: ethylene glycol, propylene glycol, butanediol, diethylene glycol, triethylene glycol, 1,2-pentanediol, 1,2,6-hexanetriol, thiodiglycol, polyethylen Diols and polypropylene glycols.

Glycol esters: Glycerol, polyalkylene glycols, lower alkyl esters of polyhydric alcohols.

Alcohol amines: diethanolamine, triethanolamine.

Amides: dimethylformamide, dimethylacetamide, dimethyl sulfoxide and sulfolane.

Ketones or ketoalcohols: acetone, cyclobutanone, N-methyl-2-pyrrolidone, N-(2-hydroxyethyl)-2-pyrrolidone, 2-pyrrolidone.

Ethers: tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monoethyl ether Triethylene glycol monoethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether.

(3) Surfactants

Surfactants commonly used are benzene sulfonates, alkylamine oxides and amine salts, acetylenic diols, and fluorosurfactants, typically 0.1% to 1.0% by weight of the ink, preferably 0.5%.

(4) Dispersing agent

For pigment-based inks, it is necessary to add a dispersant to the ink in order to ensure its dispersion stability in water. Usually water-soluble pigment dispersion resins are used, including styrene-maleic acid copolymers, styrene-maleic acid- Acrylic naphthalene-maleic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, ethylene naphthalene-maleic acid copolymer, and the like. The concentration of the dispersion resin is preferably 0.05% to 2.0% with respect to the total weight of the ink.

(5) pH regulators and other regulators

pH regulators, also called buffers, can use inorganic acids or inorganic bases. Common inorganic acids include hydrochloric acid, phosphoric acid or sulfuric acid; organic acids include methanesulfonic acid, acetic acid and lactic acid; inorganic bases include alkali metal hydroxides and carbonates; common organic bases include ammonia, triethanol and tetramethylethylenediamine.

Other additives can be added according to the specific application requirements of the ink, such as UV absorbers, metal chelating agents, defoaming silicone oil, and the like. The content of these additives is generally 0.1% to 1.0%, preferably 0.5% by weight of the ink.

Example of composition of liquid water-based ink:

Dyes 4.0% Sodium benzenesulfonate 0.5%

Chelating agent 0.5% Sodium borate 0.5%

Ethylene glycol 20.0% deionized water balance

(to be continued)

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