Selection and use of steel screen printing ink
Yang Wenliang
The screen printing of steel drums is a new technology that has gradually matured in recent years. It has changed the backward process of the original missing printing type, which not only improves the production efficiency and printing quality, but also reduces the labor intensity and avoids environmental pollution. This process is a typical green process and an important step for the environmental protection of steel drum packaging. Therefore, the current development of the process in China is on the rise. However, due to technical reasons, most companies have not fully mastered this process, and many process or quality problems have arisen. In order to guide enterprises to apply this technology correctly, the author has systematically applied this technology in steel shovel production. Research. A brief introduction to the issues of common interest to most companies is now available.
Steel wire mesh brush ink composition
1. Screen printing inks generally consist of colorants, binders and adjuvants.
1, color material
As the name implies, coloring is a material that makes the ink appear color, and it is an important part of the ink. Colorants are generally selected from organic and inorganic pigments, and dyes are generally not used in steel enamel inks. Compared with inorganic pigments, organic pigments have bright color, high tinting strength and good chemical resistance, but some varieties have poor light resistance, heat resistance, color resistance, color migration resistance and solvent resistance. Inorganic pigments have large hiding power and light resistance. The heat resistance and color migration resistance are good; however, the density is large, the refractive index is large, the particles are large, and the hue is poor.
2, the binder
The binder is a uniform fluid component in the ink, which uniformly disperses solid materials (colorants and other auxiliary components) in order to facilitate uniform transfer of ink during printing, and to dry the ink after printing, and to form a film. The material is attached to the surface of the substrate.
The binder generally consists of grease, resin and solvent.
(1) Oils and fats include animal oil, vegetable oil, and mineral oil. Because of its different drying conditions in the air, it is often divided into thousands of oils, non-thousand oils, and non-drying oils. The dry oil contains unsaturated bonds, which are easy to combine with oxygen to cure or double bond activation at high temperature to crosslink. It is often used for heating and drying screen inks: non-drying oil is mostly high boiling point mineral oil, not suitable for steel. Screen printing of the barrel. Commonly used dry oils are mostly glycerol esters of unsaturated fatty acids, such as linseed oil, tung oil and the like.
(2) Resins for resin binders include natural resins and synthetic resins. The resin for steel drum printing screen ink is basically made of synthetic resin, and a small amount of natural resin derivative (such as cyclized rubber) is used. The resin is the main material for the ink film to form a strong adhesion to the surface of the steel drum, so it is necessary to Great affinity for plastic surfaces. The main resin used for the ink connecting agent for steel drum screen printing is epoxy resin.
(3) Solvent
1 The effect of the solvent on the solvent of the resin is to dissolve the resin, to form a binder, and to evaporate after printing to form an ink film. Therefore, the first condition of the solvent for the ink binder is that it has good solubility for the compound and the resin. Broadly speaking, the process of mixing two or more substances into one phase is called dissolution, and the resulting phase is called a solution.
2 The effect of solvent on the dryness and safety of steel drum ink, solvent has a great influence on the drying speed and safety of steel drum ink. Generally, the steel drum ink is volatile and escapes. The resin and color material remaining on the surface of the steel drum are dried and formed into a film attached to the surface of the steel drum. The drying speed is directly affected by the boiling point and evaporation rate of the solvent, and the solvent accounts for the ink. The ratio determines the evaporation rate of the ink, and the dry film quality of the ink also depends on the reasonable evaporation rate gradient of the mixed solvent and the suitable solvency.
3. Auxiliary agent for steel drum screen printing ink
The two components of the ink - the colorant and the binder - are described above. They are the main agents of the ink. For the ink, these two components are indispensable; in addition to the main agent, in order to meet some special needs of the ink performance, it is often necessary to add some auxiliary components, which are auxiliary agents. There are many types of adjuvants, and the following are commonly used:
(1) The thickener increases the consistency of the ink and reduces the sinking property of the solid particles in the ink. There are ways to avoid the deposition of agglomerated ink:
(2) Viscosity improver improves ink fluidity;
(3) a dispersing agent promotes dispersion of the colorant in the adhesive;
(4) The antifoaming agent promotes the elimination of bubbles in the ink;
(5) a homogenizer to improve ink smoothness;
(6) The ultraviolet absorber improves the weather resistance of the ink.
In addition, there are antistatic agents, curing agents, color separation inhibitors, and the like.
Second, the color printing of steel drum screen printing ink
1, the principle of color
To get the right color, the ink should be carried out under stable natural light, free from illusions. When preparing fresh ink, the dark ink should be gradually added. Do not add too much at once. At the same time, the mixed hue should be reduced as much as possible. The more the hue, the larger the gray scale. In addition, attention should be paid to the color change before and after drying. For example, on a light-colored steel drum with a large amount of ink absorption, the ink color after drying is often talked about: white ink will turn yellow after high temperature. These discoloration rules require the printer to accumulate experience and samples in practice to make alternate swatches. Color blending usually uses basic principles such as subtractive color. There are three different forms of color matching: color blending, color and overlap, and color juxtaposition.
(l) Color matching of color ink
The magenta, blue, and yellow, which have high brightness, are called the primary colors of the color materials, and the three primary colors are mixed in different proportions to obtain various hue which are darker than the primary colors. The colorants are mixed to give various colors. Magenta + Huang Qi Deng, yellow + blue = green, blue ten red / purple, the above is the result of mixing in equal proportions. If the mixing ratio is different, the colors obtained are different. We refer to the color mixed by the two primary colors as the inter-color. The color that is mixed in proportion is called the standard color.
The color obtained by mixing the three primary colors is called a complex color, such as magenta ten yellow ten blue = black (equal ratio). The complex color can also be obtained by mixing the colors, for example, magenta (1 part), ten green (two parts) = black; green ten magenta (small amount) = dark green. The complex color is darker than the color.
(2) overlapping of colors
When two or more colors are applied together, a new color sensation is caused. Colors applied to overlap are generally more transparent. The thinner the color applied to the white steel drum, the stronger the brightness, resulting in the following phenomenon: the thinner the yellow, the closer to the yellow-green feeling; the thinner the orange, the closer to the yellow feeling; the thinner the red, the closer it is. The feeling of orange; the thinner the dark red, the closer it is to red; the thinner the cyan, the closer it is to green; the thinner the purple, the closer it is to red; the thinner the dark purple, the closer it is to purple.
The overlap of the above colors also conforms to the order of the bands of the spectrum. In general, the color of the color pattern uses a method of overlapping colors.
(3) juxtaposition of colors
The juxtaposition of color is to associate one color with another color, enhance or weaken the natural hue from mutual reflection, and form a new color feeling due to the illusion of visual nerve.
2, the method of mixing ink
When the color ink is used before the first use, the color to be prepared on the color sample is separately exposed, and the original or the original color is correctly identified as the primary color, the intermediate color, or the complex color. If it is a color, a complex color, you need to distinguish the ratio of the primary color to the complex color. Secondly, it must be debugged according to the color tone indicated by the original, and it can be adjusted in a large amount when the color difference is small or equal compared with the original. Pay attention to the following three points when stencil printing ink is stenciled:
(1) When adding ink, it is necessary to add less ink of different colors as much as possible. The less the type of color ink, the better the mixing effect.
(2) The principle of shallow to deep, regardless of the preparation of light or vivid color inks, should be cautious when the hue is close to the sample. Ink produced by different manufacturers, it is best not to mix and call, try to use the same manufacturer of different colors of ink to color, otherwise it will produce uneven color tone, in severe cases will appear condensation and ink scrap.
(3) Some silk screen printing inks are dried by drying, lighter and dry after drying in lighter colors, and darker after drying in dark colors. In addition, it is necessary to pay attention to whether the color tone of the ink differs after drying during printing. Generally, the color does not change by a naturally drying (solvent-evaporating ink) steel drum.
The original ink colors are mixed in different ratios and can be used with a lot of colors.
The formulation of light-colored inks is generally based on self-inking, with appropriate color inks. Such as light blue, mainly white ink, slightly added blue ink (cyan); light red, mainly from ink, slightly increased red; gray, mainly white ink, slightly black; silver gray, mainly white ink, Add a little silver paste and add a trace of black ink. To prepare a light-colored silk screen printing ink, it is necessary to add as little white ink as possible, because the self-inking activity is large, and it is easy to cause discoloration of other colors.
In short, to adjust the ink, you must do the following:
(l) Understand the various specifications and properties of the ink, so that the prepared ink is suitable for production needs;
(2) To master the basic knowledge of color science, use it freely in the adjustment of ink;
(3) Analyze the color and process technology of printing to find out the color sequence of multiple sets of colors, so as to avoid the color sequence not being miscible with the two colors, and the color changes;
(4) Pay attention to the measurement of ink color when adjusting ink. It is required to adjust the original color as much as possible. Otherwise, the ink will be blackened and the original color brightness will be reduced.
Third, ink printing adaptability adjustment
Usually the factory screen printing ink, the viscosity is slightly larger, the user should use appropriate solvent, diluent, surface activity according to the characteristics of the printing pattern, mesh size, printing speed, environmental humidity, steel drum surface tension and ink absorption performance. The agent, the viscosity reducing agent, etc., comprehensively adjust the viscosity, surface tension, fluidity and drying speed of the ink. For silk screen printing lines and dots, the ink should be slightly less fluid and the drying speed can be slightly slower; when printing on coarse mesh, the viscosity should be slightly larger and the drying speed can be slightly faster; when printing at high speed, the fluidity is slightly larger and the drying speed can be Slightly faster; when the working environment temperature is high, the drying should be slower and the viscosity is slightly larger; when the surface of the steel drum is small, the surface tension of the ink should be smaller; when the surface of the steel squeegee is strong, the fluidity and surface tension of the ink can be Larger, the drying speed can be slower.
The screen printing of steel drums is printed by the ink extruded from the screen, so the determination of the viscosity of the ink depends largely on the size of the mesh mesh and the material of the screen. When using a high monthly screen printing, the viscosity of the ink is low, so that no ink flooding occurs during printing. So, what kind of viscosity is appropriate? Usually, the adjusted ink is placed on the screen plate to test. If the ink can pass through the mesh of the screen, it will not drop, and the viscosity is adjusted to be suitable. If the ink is to be dripped, the instructions are too dilute; if the ink does not pass through the mesh, the ink is too thick and requires additional solvent.
Fourth, the type and selection of steel screen printing ink
Steel drum screen printing inks are generally purchased from the market, and can be roughly classified into two types of inks, dry type and light solid type. Dry type inks are mostly used for the printing of the upper barrel of the steel drum container. This is because the light-solid ink is expensive except for itself, and the drying equipment is added, which increases the printing cost. The imported inks purchased from the market include American 膺 brand series, German Baolong, Singapore SSI series, Japan Toyo SS series and Yi Dahe ij-ARGON series, etc.; domestic inks have GS series produced by Guangdong Zhongshan Jinlong Ink Factory.
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