Offset Printing 1000 Questions (88-99)

89. What are the components of offset inks?

A: Offset ink is a uniform, colored, adhesive, fluid that is fully agitated and ground from pigments, fillers, binders, and accessories. Its main components are pigments, binders and excipients.

90. What is ink paint? Including which types?

A: Ink pigments are colorants that make inks show a certain color. They are insoluble in water, oil and other media. They can only be dispersed in adhesively linked materials, directly affecting the rheology, dryness, and various resistances of the inks. Ink pigments develop color by reflecting light at a specific wavelength.

Offset ink pigments are inorganic pigments and organic pigments. Among them, organic pigments are divided into three kinds of chromatic pigments, lake pigments and pigment dyes. At present, the pigments used in China's lithographic offset inks use more organic pigments with bright colors and strong coloring power in color inks, while inorganic pigments are gradually being eliminated. Non-color inks, like international ones, are still dominated by inorganic pigments, and no cheap organic pigments have been available for replacement.

91. What is ink binder? Including which types?

A: The binder is an adhesive fluid with a certain viscosity and rheology. It is the dispersion medium and film former for ink pigments. Ink binders include synthetic resins (including solid resins and liquid resins), dry vegetable oils, and mineral oils (ink oils). Resin is the main component of the binder. Usually, the solid resin and the liquid resin are used. At present, in the solid resin, the diphenol-based rosin-modified phenolic resin is most widely used, and the liquid resin is phthalaldehyde. Mainly dry modified alkyd resin. Dry vegetable oil is currently used as a toughening agent or plasticizer for resins. It exists in the composition of linking materials. With the upgrading of the main resins of inks, the amount and role of them in ink composition will gradually be mineralized. Replaced by oil. Mineral oil is a thinner and viscosity reducer for the resin in the ink, and it is also one of the pigment dispersion media that replaces the dry vegetable oil.

92. What is ink accessories? Including which types?

A: The ink accessories are additives that are used in the ink composition to improve or adjust its tinting power, drying properties, and rheological properties, so that the ink can adapt to various requirements of the printing process technology. In addition to fillers, impermeable agents, and slip agents that are added during the manufacture of inks, ink auxiliaries are mostly driers, anti-adherents, and the like added at the time of ink distribution at the printing site.

93. Domestic offset printing inks fall into several categories. What inks are included?

Answer: Offset printing inks mainly have the following 7 common classification methods in lithographic offset printing.

1 According to the color points, there are two types of offset printing inks: color ink and non-color ink. Among them, the color ink includes various series of standard three-color inks, such as international universal type, Kodak type, Japan and Western Europe universal three-color ink.

2 according to the nature of the pigment, offset printing inks are common pigments (organic and inorganic) inks and metal pigments (copper, aluminum, etc.) Ink two categories.

3 according to the nature of the link material, offset printing inks are grease type ink and resin type ink two major categories, including resin type ink is divided into ordinary type, bright type, fast fixing type and fast solid light type ink.

4 According to the type of printing press, there are two types of offset printing inks: sheet-fed offset printing ink and web-fed offset printing ink.

5 According to the use of the printing process, there are two types of offset printing inks: proofing inks and printing inks.

6 According to the nature of printing materials, there are two major categories of offset inks, paper ink and tinplate ink.

7 According to the ink fixing and drying mode, there are two types of offset printing inks: thermosetting ink and non-thermosetting ink. The non-thermosetting ink is divided into oxidation polymerization type and osmotic solidification type.

94. What is a sheetfed offset ink?

A: Sheetfed offset inks generally refer to various types of printing inks used in sheetfed offset machines. At present, this type of printing ink has grease type and resin type. Among them, resin type inks include different types and series. This type of ink is often referred to as offset ink, resin offset ink, bright offset ink, etc. in production.

95. What is a web offset ink?

A: Web offset inks generally refer to various types of printing inks used in web offset machines. In the form of fixed drying, web offset inks are generally classified as non-thermosetting (or fast drying) and thermosetting inks. This ink is often referred to as offset rotary ink in production.

96. What kind of performance requirements should offset ink have?

A: Offset printing is an indirect printing method. Although different types of offset printing presses vary in the form of paper feeding or the type of paper used, they must generally be cured by concentrating the ink onto the surface of the paper through processes such as ink supply, ink distribution, and ink deposition. , forming a graphic. Therefore, offset ink must meet the following three basic requirements.

1 Regardless of the type of paper and model used, offset inks used should not exhibit condensation, gelation, delamination, surface conglomeration, etc., nor should they be mixed with impurities to affect the appearance of the print job.

2 The chromaticity properties, rheological properties, transfer and separation properties of the ink, and the physical properties of the ink film strength must all be compatible with the basic conditions of the printing process in order to ensure smooth flow, transfer and separation on the printing press. Fracture, until cured shows color, showing shiny.

3 In offset printing, the ink has the chemical properties of acid resistance, alkali resistance, water resistance, solvent resistance, etc. It is important to maintain the ink balance with the fountain solution and to minimize ink emulsification until the fixation is dry. In addition, the nature of the anti-chemical properties of the ink film, such as light resistance, water resistance, acid resistance, and alkali resistance, also directly affects the use of printed products. Therefore, offset printing inks must meet the chemical properties of the offset printing process and the use of printed products.

97. What is the physical properties of the ink? What are the aspects included?

A: The physical properties of inks refer to the inherent physical properties of offset inks, including ink fineness, transparency, coloring power, fluidity, viscosity, viscosity, viscoelasticity, thixotropy, and yield value.

98. What is ink fineness? What is the effect on offset printing?

A: The ink fineness refers to the maximum particle diameter of the pigment, filler, etc. in the ink, and the uniformity of the distribution in the binder. At present, the fineness of domestic offset printing inks is generally 15 to 20 μm, and the fineness of inks produced by most ink manufacturers is under 15 μm, but the fineness of various auxiliary materials is generally 20 to 35 μm.

The fineness of the ink determines the fluidity and color strength of the ink body to a certain extent, and has a great influence on the printing process and the printing quality. In the printing process, the fineness of the ink affects the transfer and sharpness of the image because it maintains a certain relationship with the dot area on the printing plate. The finer the fineness of the ink, the more full the dot of the printed imprint, the stronger the coloring power; if the fineness of the ink is too thick, the drawbacks such as imaginary, enlarged dots, poor shape, and lack of smoothness of the dots are liable to occur, and are easily destroyed. Versions, pastes, heaps of ink (including heap plates, blankets, etc.) are also detrimental to the integrity of small outlets.

99. How to measure the fineness of the ink?

Answer: In practice, the measurement of the ink fineness is mostly carried out using a 50-μm single-slot scraper fineness meter. The specific method is: according to the size of the ink flow, dilute the 0.5ml ink sample with No. 6 varnish, place the diluted ink sample in the depth of the groove at the beginning of the fineness meter, and hold the hands vertically. The squeegee is set to 90°, and then the ink is scraped to the end of the scale, and the angle of the light source is observed with a 10× magnifier at a 30° angle. The particles are densely packed with more than 15 values ​​within one scale, which is the fineness value of the ink. Note: The average value of 2 to 3 measurements should be taken during the measurement.

(Author/Drilling)