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Technology of Letterpress Printing of Medical Labels

       Pharmaceutical label is an indispensable product identification of drugs. It can be said that it is also the ID card of pharmaceutical products and an important production process in packaging and printing technology. The main contents of the medical label shall generally include: 

       product name, adaptive symptoms, production date, production batch number, specification, quantity, precautions, shelf life, dosage and usage, storage environment requirements, manufacturer’s name, etc. Product labels are printed in monochrome, overprint or overprint in multicolor; 

       Some are printed with offset paper, others are printed with coated paper and other self-adhesive paper. From the perspective of health and safety, the printing quality control of medical labels is a very important technical link. 

       Therefore, the instructions in the product layout must be clear and clear, and the printed color must be accurate and consistent. It can be seen that medical labels should have the requirements of easy identification and good anti-counterfeiting effect. A considerable part of medical labels are printed by traditional letterpress printing technology.  

      The author has also printed medical label products in clinical production practice in the past, and has personal experience in the letterpress printing technology of medical product labels. Based on the practice of letterpress printing process, this paper discusses some experience of process technology control

Technology of Letterpress Printing of Medical Labels

Some technological measures to improve the printing quality of label products

 

       Pay attention to the technical control of paper cutting process. The specification accuracy of paper directly affects the overprint accuracy of products. Because of different machine structures, their front gauge and pull gauge positions are not the same. In this way, if the edge of the paper is not cut square enough and there is a bevel or wavy edge, it will cause inaccurate overprint. Technology of Letterpress Printing of Medical Labels

      This requires that for the products with glue convex combination, the side of the paper must be cut into right angles and straight lines, and there shall be no bevel or wavy edge. In order to improve the cutting accuracy of paper, the cutting thickness must be strictly controlled, because the thicker the paper stack and the softer the paper, the more severe the paper surface deformation when the paper press is pressed down.Technology of Letterpress Printing of Medical Labels 

       Therefore, the less the cutting thickness of each stack, the more conducive to improving the cutting accuracy of paper. In addition, the blade edge should be kept sharp, and the appropriate blade angle should be selected according to the hardness of the paper, which is also an important measure to improve the cutting accuracy.Technology of Letterpress Printing of Medical Labels

 

       Pay attention to the reasonable selection of the bottom support of the printing plate. For the relief printing press with circular flattening structure, the characteristics of the plate base material have a great impact on the printing pressure, overprint accuracy and ink quality.Technology of Letterpress Printing of Medical Labels

        The traditional wooden bottom support is not solid, with poor squareness, flatness and stability. It is easy to bow and deform, and the printing quality is difficult to guarantee. Technology of Letterpress Printing of Medical Labels

      Therefore, relief printing should use solid, flat, square and stable aluminum or cast iron and other metallic materials, which is a reliable guarantee to improve the overprint accuracy and ink quality.Technology of Letterpress Printing of Medical Labels

 

          Pay attention to the rational use of paper. Paper is very sensitive to the temperature and humidity changes of the external environment, especially the paper just produced, which is most prone to expansion and variation due to the changes of temperature and humidity, resulting in inaccurate overprint of products.Technology of Letterpress Printing of Medical Labels 

         In order to reduce the chance of this bad situation, the newly produced paper usually needs to be stored for about half a year after being transported back by the printing factory, so that the paper can be put into use after its characteristics are relatively stable, so it is not easy to have overprint problems. Technology of Letterpress Printing of Medical Labels

       In addition, it is also conducive to the registration of products by hanging the paper and placing the cut paper in the printing workshop for several days to balance with the temperature and humidity of the printing workshop for a period of time.Technology of Letterpress Printing of Medical Labels

 

         Pay attention to select the appropriate printing plate. Letterpress printing process uses copper plate, zinc plate, resin plate and other plate materials. Due to the different characteristics of printing plate materials, there are obvious differences in their printing suitability and printing quality. Technology of Letterpress Printing of Medical Labels

         According to the ink affinity, ink transmission, gloss and pressure effect, resin plate performs best, copper plate takes second place and zinc plate performs worst. In terms of dot printing quality, the copper plate dot printing quality is better and the dot expansion rate is the least.Technology of Letterpress Printing of Medical Labels

       Therefore, according to the characteristics of products, we should reasonably select plates for printing, so as to better improve the printing quality of products.Technology of Letterpress Printing of Medical Labels

 

          Pay attention to the reasonable arrangement of printing color sequence. Reasonable arrangement of printing color sequence is an important measure to improve printing quality. Technology of Letterpress Printing of Medical Labels

        Reasonable arrangement of printing color sequence should be considered from these aspects, that is, considering the arrangement of printing color sequence according to the characteristics of substrate; Technology of Letterpress Printing of Medical Labels

        Arrange the color sequence according to the difference of printing machine structure; Arrange the color sequence according to the different graphic structure of the printing layout; Arrange the color sequence according to the color characteristics of the original;Technology of Letterpress Printing of Medical Labels

        Arrange the color sequence according to the difference of ink characteristics; Arrange the color sequence according to the ink drying characteristics. This scientific and reasonable arrangement of printing color sequence can better improve production efficiency and product printing quality.Technology of Letterpress Printing of Medical Labels

 

        Pay attention to the lining technology. Lining is the medium of pressure and imprint transfer. Its characteristics also affect the registration and ink quality of products. Therefore, the deformation coefficient of the lining material should be smaller, and the material should be neutral and hard. Technology of Letterpress Printing of Medical Labels

       At the same time, the thickness of the lining must be determined in strict accordance with the technical parameters of the equipment specification. Technology of Letterpress Printing of Medical Labels

       In addition, the lining must be tightly wrapped and tight, and there shall be no virtual looseness or bulging. It is forbidden to make repeated patching or hollowing on the lining to prevent inaccurate overprint and ghosting.Technology of Letterpress Printing of Medical Labels

 

         Pay attention to adjust the appropriate printing pressure. The printing pressure should be adjusted evenly and moderately. Excessive pressure is easy to stretch and deform the printing sheet, resulting in the disadvantage of inaccurate overprint. Technology of Letterpress Printing of Medical Labels

        Therefore, the appropriate printing pressure should be adjusted. The printing pressure should not be biased, so as not to make the edge of the printing page rough and enlarged.Technology of Letterpress Printing of Medical Labels

 

         Pay attention to master the overprint production cycle of the product. After printing the first color or several colors of the printed matter, those that can be overprinted shall be overprinted immediately, so as to avoid stretching and variation of the printed matter due to too long delay, resulting in inaccurate overprint and quality failure.Technology of Letterpress Printing of Medical Labels

 

       Pay attention to prevent printing from sticking and dirty. When printing pharmaceutical label products with relief process, it is easy to cause the back of the product to rub dirty when it meets the conditions of good paper gloss, acidic paper, affecting the drying of ink layer, large printing ink supply, slow ink drying speed, excessive stacking of semi-finished products, etc.Technology of Letterpress Printing of Medical Labels

       The solution is to use the “deep ink thin printing” process for printing, that is, to darken the ink hue and make the printing ink layer thinner. In this way, it can not only meet the printing ink color requirements, but also reduce the chance of sticking. In addition, you can add some dry oil in the ink to dry the ink layer in time; Technology of Letterpress Printing of Medical Labels

       Add some anti adhesion agent in the ink to make it difficult for the ink layer on the surface of the print to transfer; Proper powder spraying shall be applied to the surface of the printing ink layer to prevent the surface ink layer from transferring to the back of the printing; Technology of Letterpress Printing of Medical Labels

      The stacking amount of printing semi-finished products shall be appropriately reduced, and the semi-finished products shall be hung in small stacks with an air rack.Technology of Letterpress Printing of Medical Labels

 

         Pay attention to prevent the printing plate from pasting. When the printing pressure is uneven or too heavy, the ink particles are too thick, the fluidity of the ink is poor, the paper surface is powdered, roughened, the height adjustment of the inking roller is inappropriate, and there is poor contact between the inking roller and the inking roller, it is easy to cause the plate pasting phenomenon. Therefore, corresponding measures should be taken for adjustment.Technology of Letterpress Printing of Medical Labels

 

         Pay attention to prevent the ink color of the printing plate from crystallizing. When too much dry oil is added to the ink, the ink layer on the surface of the print is excessively dry to form a glass surface, so that the overprint ink is difficult to adhere to the background color of the print.Technology of Letterpress Printing of Medical Labels

       Even if it can be printed, the ink only shows an obvious blooming phenomenon, which is the crystallization phenomenon of the ink film. Technology of Letterpress Printing of Medical Labels

        To prevent the crystallization of printing ink film, we should strictly control the amount of dry oil and shorten the overprint production cycle as far as possible. For semi-finished products that have crystallized, add some soap chips to the overprint ink. Technology of Letterpress Printing of Medical Labels

      The method is: first mix the soap crumbs into slurry with resin oil, and then add them into the ink, which is easier to stir evenly. After adding soap to the ink, add some dry oil, otherwise the overprint ink layer will dry slowly.V

 

       Pay attention to prevent the ink color of the print layout from blooming. When the printing pressure is uneven or too light; The lining surface is deformed under pressure and loses good flatness; Technology of Letterpress Printing of Medical Labels

      The paper surface is powdered, roughened and adhered to the layout or ink roller; The colloid of the inking roller deviates from the core, resulting in uneven inking.Technology of Letterpress Printing of Medical Labels