Analysis of screen printing technology in the hott

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Analysis of printing technology in special printing (Part 1)

with the improvement of technical level and the development of label technology, using special printing to deal with the bottom layer of label panel has become a common means, and it is colorful and beautiful, which not only increases the decorative, but also obtains a more prominent effect. The following introduces several common special printing techniques to further reduce the permeability of brush printing and questions to be paid attention to (2) fireproof materials

I. pearlescent printing

pearlescent printing is a new type of printing popular in packaging printing and anti-counterfeiting printing in recent years. It mainly uses pearlescent ink. Pearlescent ink is an ink with pearl luster. When the printing pattern changes the angle, the color of the ink will change, so that the authenticity can be recognized. The printing process of pearlescent printing is basically the same as that of traditional printing. The key lies in the preparation of pearlescent ink, which is generally composed of binder, thickener, pearlescent pigment, solvent, additives, etc. In the formulation of pearlescent ink, the flashing effect of pearlescent pigment is passive luminescence, that is, it can show its flashing effect under the condition of receiving light. In order to give full play to this feature of pearlescent pigments, when selecting pearlescent pigments to mix inks, we should pay attention to the following three relationships:

1. The relationship between the size of pearlescent pigments and the flash effect. The pearlescent pigments used in packaging and printing will suddenly drop under the load. Usually, if the film diameter is large, the distance between flash sources is large, and the flash effect is dispersed; On the contrary, if the film diameter is small and the flash source spacing is small, the flash effect will be concentrated

2. The relationship between the diameter of pearlescent pigments and the flash intensity. The larger the flake diameter of pearlescent pigment, the more opportunities for its surface to be reflected and refracted by light, and the stronger the intensity of flash; On the contrary, the intensity of flash is weak

3. The relationship between the flake diameter of pearlescent pigment and its coagulation and suspension sedimentation in binder. Generally, the smaller the flake diameter of pearlescent pigment is, the easier it is to condense, and the smaller the aspect ratio of particles is, so it is easy to settle in the binder, otherwise it is easy to be suspended

in order to make the pigment evenly dispersed in the binder, it is necessary to select the pearlescent pigment with appropriate sheet diameter and aspect ratio according to the density of the binder on the basis of mastering the three relationships. In ink blending, thickeners can also be added to prevent the deposition of pearlescent pigments; Or wetting the pearlescent pigment in advance and then dispersing it in the binder, which can also avoid the disadvantage of particle agglomeration and sedimentation

the blending method of pearlescent ink is as follows: ① generally, 10~20g pearlescent pigment is added to every 100g of ink; ② After the pearlescent pigment is directly mixed with the binder in the ratio of 1:1, the surface of the oil is generally not or rarely decorated with fabric or leather, and the ink fluidity meets the printing requirements; ③ Some trace organic pigments can also be added when preparing color pearlescent ink to reduce the cost. Generally, white pearlescent pigments are used together with other pigments, such as adding 1% carbon black to white pearlescent pigments to obtain ancient silver effect

generally speaking, the pearlescent color should be mainly light color, because too much dark pigment will cover part of the pearlescent luster when blending dark color. In addition, it is not allowed to mix the color pearlescent ink series products. It is different from general-purpose inks. It can use two or more inks to mix into another color. When two or more pearlescent inks are mixed, complementary colors will appear between them, which will reduce the pearlescent effect

pearlescent ink printing is mainly used in commodity packaging printing, such as soap packaging paper, cigarette box, cigarette holder, greeting card, wallpaper, food packaging paper, etc; Film printing: pet, PE, OPP, PS, etc. In terms of printing process, pearlescent printing is almost suitable for all kinds of printing. However, due to the different mechanical properties, technical indicators and operations of different printing processes, the proportion of pearlescent ink is also different. In silk printing, the general proportion of pearlescent ink is: binder 10%~45%, thickener 0.5%~1.5%, pearlescent pigment 5%~30%, solvent 15%~35%, and an appropriate amount of additives

second, braille printing

with the development of science and technology, we can already use silk printing and foaming ink to print Braille. The printing of Braille books, documents and other publications is completely different from the graphic printing of general books and periodicals. The size, dot spacing, word spacing and line spacing of Braille bulges have been fixed in the design according to the physiological and psychological characteristics of blind people's touch. The shape of the bump is generally hemispherical or parabolic. The diameter of the bottom of the bump is 1~1.6mm, the height is 0.2~0.5mm, and the point distance is 2.2~2.5mm. If the bump is too small and too close, it will affect the touch response speed of the blind, and if it is too large, it will exceed the most sensitive area of the fingertip touch of the blind. Braille printing methods mainly include die stamping, ink printing and foaming printing

(1) die stamping method. It is the earliest printing method used in braille printing. When printing Braille, first use a special typewriter to punch concave points on the double-layer iron sheet to make a Braille concave convex mold. Then special thick paper is placed between two die sheets, heated and pressurized, and embossed on the thick paper to form Braille pages. Generally, 120g thick kraft paper is used. If you find errors in the layout, just flatten the bumps and re type the corrected ideas. After printing, the pages are bound into a volume, which completes the printing of Braille books

(2) ink printing method. Braille printing with ink is a great progress in braille printing. The method is to add a certain proportion of rosin powder and other auxiliary materials into the ordinary ink to make rosin ink, and then use relief printing or silk printing to print the blind spots or patterns on the paper. After heating and baking, the ink is raised to make the required Braille. The blending method of this rosin ink is: melt the rosin and put it into corn flour, stir it evenly, then slowly pour the pigment dissolved in ethanol, stir it evenly, and then print; Rosin powder can also be added to offset printing ink or relief printing ink

note: the ink must be mixed strictly according to the specification and proportion, and the viscosity of the ink must be well controlled, and it should be firm but not brittle after being heated up, with a small deformation rate. Strictly control the amount of additives, and the ink consistency should be high, and the wire head should be appropriate. The effect of silk printing will be better

(3) foaming printing method. Foaming printing is the most widely used method in braille printing at present. Foaming printing is to use the ink with foaming characteristics to print on the paper. After heating, the ink foams and bulges when heated, and solidifies into a convex picture and text at room temperature. Braille foaming printing can not only print on both sides of the paper, but also print patterns; The Braille printed has the characteristics of wear resistance, soft texture, long-term touch and reading without hurting fingers, etc

foaming printing usually adopts the method of silk printing. The process flow is:

preparation of silk plate and foaming ink → silk printing → low temperature drying → heating foaming → binding into a volume

at present, the types of foaming printing mainly include microsphere foaming printing and groove bottom foaming printing

microsphere foaming printing is widely used in new braille printing technology systems. The braille printing system is different from the original Braille production method. It uses a computer, which can greatly reduce the process of plate making, and can print Braille books in large quantities and quickly; Braille printing can not only print Braille characters, but also print patterns, and both sides of the paper can be printed. The thickness of a book is only 2/3 of the original braille printing with zinc plate, which greatly reduces the raw materials and operating costs; Braille printed with foaming ink is durable and not easy to be damaged

the foaming printing process at the bottom of the groove is relatively complex. The prepared paste ink is brushed or printed on the substrate, and then foamed after printing with the printing roller; Or adopt groove bottom printing roller printing, and produce concave convex graphics and texts of different shapes after rolling

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