The screen printing industry has only begun to develop rapidly since the development of color inks. Although the term "pigment" has been used instead of the word "pigment" originally used, the term "pigment" is better than "advertisement color" (one of the early words of screen printing) when it comes to the quality of printed media. Has a deeper connotation. Screen printing is called color media because it has the same results as other images that are reproduced using ink, and it also uses squeegee blades, rollers, and vacuum. It uses brushes, jets, or roller pressure. Ink is transferred to the surface of the substrate.
Compared with other inks, screen printing ink must be squeezed by a squeegee to reach the surface of the substrate through the screen cloth. In order to ensure that the work is carried out normally, whether by manual or mechanical methods, there must be no material under the squeegee that impedes the passage of the ink. The ink must not block the screen mesh (mesh), damage the screen, and must not dissolve or destroy the screen plate. They must be able to print clean edges without burrs. Usually these inks must be able to dry by oxidizing, evaporating, polymerizing, melting, or compounding, but they cannot be blocked quickly by the mesh. However, the new UV-curable ink is immediately dried under UV light irradiation without blocking the mesh. When needed, the ink layer can be printed thick to form an embossed effect, sometimes 20% thicker than the thickness of the letterpress print. But when printing halftones and printing on silk, they cannot leave relief.
Screen printing inks must be able to print on the surface of the following materials: paper, cardboard, wood products, metals, plastics, rubber, silk, glass, porcelain, leather, cork, gypsum, or composite surfaces of the above materials. During the printing process, the ink cannot rub the printed material. The most important thing is that the screen printing ink cannot interfere with any printing operation.
The ink must allow the printer to make some changes to it, that is, the ink can be transferred. However, it must be adjusted according to the manufacturer's instructions. In addition, changing too much at the time of ink adjustment may degrade the performance of the ink because a better ink is developed by a chemist over a certain period of time under certain conditions and cannot withstand large changes. In terms of color, the pigment in the ink must have a long-lasting and stable quality. Of course, if the ink can be changed as easily as the wind, then the printing industry will save more. But this is not the case. Some inks can only be used for screen printing. For all printing categories in the printing industry, not only do they require different inks, but the inks themselves are also very different. There are many kinds of screen printing inks and the classification is very complicated. They can be categorized in the following ways: (a) Classification by substrate surface; (b) By natural or synthetic classification; (c) By transparent, opaque, translucent classification; (d) By gloss classification; (e) By Classification of the used binders; (f) Classification by drying methods; (g) Special inks. When screen printers understand various categories, they also understand various screen printing inks. The variety of screen printing inks is also related to the use of screen printing inks and the use of related industrial inks. The initial source of silk screen printing inks was the use of related industrial inks, and many new inks were developed on this basis. Although only those borrowed inks can know where they came from, the development of screen printing inks has greatly promoted the development of the screen printing industry. They have not only increased the value of the products but also improved the appearance quality. The different types of inks are described below.
Divided by the surface of the substrate, silk screen printing ink can be divided into: resin screen printing ink, glass screen printing ink, glass etching screen printing ink, textile screen printing ink, ceramic screen printing ink and so on. Natural inks are made from natural materials that are found directly or indirectly. Synthetic inks are the result of all or part of artificial synthesis and chemical research.
Opaque inks have the ability to completely block the printed surface without passing any light. Clearly, the clear ink allows light to pass through to reveal the printed surface. Also included in such inks are those inks that can be printed directly on other colors to give a variety of different colors. When using opaque inks, two or more colors can be mixed to produce a third color before printing because the third color is not printed when overprinting, but one kind of ink blocks another ink. The translucent ink has a transparency between transparent and opaque.
In the fourth category, conventional inks are those that do not have reflective or luminescent properties after drying. Bright inks and semi-gloss inks are two types of inks with different degrees of light emission on the ink film after drying. This mainly depends on whether they contain long oil varnish or short oil varnish. Blue paint is marked with long oil, medium oil, and short oil. This classification is based on the number of gallons of oil contained in 100 pounds of resin. For example, long oil varnish typically contains about 25-50 gallons of oil, while short oil varnish contains about 5-25 gallons of oil. The long oil varnish has a luster and is usually sold in the form of a crucible made of natural or synthetic resin oils and desiccants added to the paint. Luminous ink is an ink that can emit light, there are three types: fluorescent ink, solar ink, phosphorescent ink. Fluorescent inks emit light under ultraviolet or black light. Daylight and fluorescent inks glow during the day or under the illumination of fluorescent lamps. Phosphorescent inks are inks that still glow when light is removed.
Classifying with binders is a practical and straightforward method. The binder is a liquid substance that mixes, dissolves or suspends very fine pigments and other materials together. It consists of a solvent and a binder. The role of the adhesive is to bind the components of the ink together to facilitate the use of the ink; the solvent is the liquid that makes the ink a fluid and can be printed. The binder used in screen printing inks is related to the substances added to other inks, but certainly not necessarily the same substance. Which connection material to use is related to the corresponding ink or pigment. This means that it must be able to coexist with the ink chemically or not adversely affect the mixing of the colors. It is interesting to note that UV inks contain pigments, binders and active agents or sensitizers called photoinitiators whose binders are 100% solids.
In the classification of binders, inks are classified into oil inks, resin inks, oil-water inks, and water-based inks. Oil-based inks are made from pigments or oil-soluble dyes that are blended with natural or synthetic resin oils. Pigments are usually present in powder form, while dyes are color substances dissolved in liquids.
Oily inks are dried in oxidized form. This means that the combination of oil and oxygen slowly causes the ink layer to lose its oil and dry. Dry oils used for oily inks include linseed oil, soybean oil, tung oil, or perilla. Because these oils exist in a liquid or pasty form and dry slowly, some desiccants consist of metal salts. Adding such desiccants to the ink can accelerate ink drying.
The resin binder ink contains resins or inks consisting of chemically reacted oils, typically as part of a plastic type material ink. Pigments can be man-made or natural. They are mixed with binders and other ingredients to make inks that have consistent plastic consistency and drying properties.
Tree esters are synthetic solid or semi-solid organic materials that are either natural or obtained by chemical reactions. Natural tree esters with different properties are used as part of the ink. When the resin is dissolved in a liquid state and suspended in the binder and desiccant, an ink or coating layer is formed to form a hard, solid, and resistant surface. Synthetic resins include alkyd resins, urea, stearic acid, modified stearic acid, and other resins that differ from natural resins in chemical structure and reactivity.
The binders in lacquers and enamels are usually composites of resins, plasticizers, cellulose acetates, or other cellulose derivatives. Plasticizers or softeners help to obtain a thoroughly mixed homogeneous product and desired properties. The binder is a combination of drying oil, metal drying agent, and solvent.
The synthetic ink is dried by evaporation or polymerization. Evaporative drying volatilizes the volatile material and leaves behind an ink layer containing resin and pigment. Polymerization drying is through a chemical reaction, in the absence of any change in the atomic ratio, a single small molecule linked and combined into a large molecule. For synthetic inks, the drying must be under normal conditions, but not at low temperatures, high humidity, and excessively thick ink layers. Synthetic inks are produced because they can be air-dried or accelerate the drying process at a given temperature and time.
The solvents used to synthesize inks under different conditions rely heavily on the given ink and manufacturer. It is obvious that due to the chemical complexity of these inks, it is not possible for the printer to meet the requirements each time the ink is transferred. Therefore, any change in the mixing ratio at the time of ink transfer should be based on the manufacturer's instructions.
For a consistent mix of inks, the mechanical mixer shown in Figure 20 can be used to help you mix inks.
Because some solvents and inks are flammable, they must be used with care. Keep away from flames, keep away from sparks, and ban smoking. In addition, if the solvent is toxic or harmful to the body, direct contact with human skin should be avoided. In the oil-water binder ink, the smaller the proportion of the binder, the better the quality of the ink. Water-based inks are inks made from pigments such as earth and artificial mineral pigments plus water-soluble gums or binders as gum arabic, dextrins, glue, casein or water glass.
When using inks, care must be taken to distinguish between gums and resins used in screen printing inks. Although they produce the same result, the gum is a substance that dissolves in water or swells in water and is a natural synthetic material. Tree esters are generally insoluble in water, both natural and synthetic. The pigments in screen printing inks come from three sources: soil pigments, chemical pigments and lake pigments. Soil pigments are naturally found pigments that are collected and refined for a certain purpose. Chemical pigments use more and more pigments and are pigments obtained by chemical reactions between different compounds and elements. The lake pigment is a special kind of organic pigment made of an inert substance such as aluminum or chalk. They can be combined with a transparent or translucent body of plastic consistency and ensure that they remain transparent when added to oily inks. However, other colors cannot be added to the ink unless specifically specified because it may cause a harmful reaction to the color.
Dyes are used as inks in the screen industry in three forms: direct dyes, dyes that require mordants, and special dyes. Direct dyes are dyes that are dyed directly onto silk fabrics and cloths without mordants. Dyes that require mordants are those that require a mordant or must be pretreated with silk before printing. Special dye inks are designed for the specific silk fabric chemicals and substances used under specific conditions. In general, these dye inks need to be accelerated by heating and evaporation.
One thing is, when the printer must change the characteristics of the ink, such as delay drying, accelerated drying, use of supplements, etc., there must be a certain limit, not excessive. Of course, these compounds must be used in accordance with the manufacturer's instructions. Retarders are solvents used to reduce drying speeds and improve print quality, such as ripcord varnish or flax oil. The varnish used in the image is classified by consistency, from NO.00000 to NO.8, NO.00000 is the thinnest, and NO.8 is the thickest. Among them, NO. 1, 2 and 3 are recommended types in screen printing operations.
Supplements are products used to expand the performance of inks, reducing the cost of the ink. They are substances that increase ink density and hardness. However, they cannot change the hue and quality of the ink. There is also a limit to the use of supplements, as the opacity of the ink decreases as the amount added increases.
Transparent base is a transparent, neutral color butter material that can be used to: (a) increase the consistency of overly dilute inks; (b) prevent ink creep from occurring
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