The mark left on the printed product of the self-adhesive label is formed by ink. The ink is the colorant for printing and the main raw material for printing. The ink is crucial to the quality of the printing quality. When the ink performance is not suitable for printing, it will It caused a series of problems and problems in the process, which seriously affected the progress of production and product quality. The printing master must change some properties of the ink to meet the needs of printing, but some problems are not only caused by the ink, but also related to other factors, so the printing master must carefully analyze and handle it correctly.
Blots dry slowly
phenomenon
After the imprint is transferred from the printing plate to the paper through the blanket, it is generally required to be dried in about 10 hours to facilitate the post-color printing or finished product inspection and delivery. Once the imprint is slow to dry, this not only makes the next color impossible to overprint, but also It is easy to make the back of the printed matter sticky and dirty. There are three factors in the drying of blots, such as oxidized conjunctiva, paper absorption, and water evaporation. We must correctly grasp the operation and prevent it in advance.
Common causes of slow drying
Paper PH value below 6
PH value of water bucket is below 3
Large water surface, large ink causes serious ink emulsification
The workshop temperature is low. Relative humidity is higher than 75%
Poor paper absorption
There are too many auxiliary materials such as ink adjusting agent and tackifier in the ink
Too little dry oil
Approach
In order to prevent the slow drying of the printed matter, the height of the stacked printed matter should be reduced, the paper pile should be shaken, and the semi-finished product ventilation can allow the air to penetrate into the stacked paper and shorten the time of its oxidized conjunctiva.
If the printing is urgently needed, the original graphic printing plate is used for dry oil overprinting, the formula is 70% of Wei Li oil and 30% of dry oil.
In order to prevent the factors of unfavorable drying, add a proper amount of dry oil. The amount of dry oil is: more in winter than summer, more in the latter color than in the previous color, and add more diluted ink than undiluted ink.
The color is not printed
Phenomenon and causes
Excessive dry oil is added to the ink or the stacking time of the semi-finished products is too long, resulting in too fast drying and causing the glass surface of the imprinted surface to become too smooth. The imprinted surface is too smooth and loses its ability to adsorb. This kind of failure is common in the full version of the field, especially the yellow version (ink) or line pattern printing.
Approach
Mainly for prevention, add appropriate amount of auxiliary materials such as Viley oil, Kangbang, magnesium carbonate powder to the yellow ink that is easy to vitrify in advance to make the surface conjunctiva rough or prolong the drying time.
If the vitrification phenomenon has occurred and the next color is not printed, if the number of products is small, you can use a soft cloth dipped in magnesium carbonate powder to gently wipe the surface ink film of each sheet, and then apply the next color, if the number is large , It can be printed while the caustic soda water is set.
Sticky back
phenomenon
Dirty on the back means that the semi-finished product or finished product enters the stack, and the back is dirty with the ink on the next printed sheet.
Causes of stickiness on the back
Paper surface is too smooth
Ink is too thin
Layout, water and ink
Ink color is too light
Printing pressure is too light
Approach
In the printing process, there should be no large water and ink phenomenon. Control the water content of the layout, the ink color becomes darker, and reduce the amount of ink delivered by the ink fountain. If the greasy or paste version is produced after reducing the water content, the water roller should be cleaned or replaced with a new water roller, or the acidity of the water bucket syrup should be appropriately strengthened and some gum arabic should be placed.
If the ink is adjusted too thinly and easily sticks to the back of the dirty product, new ink should be replaced or some new ink should be added to increase the viscosity of the ink.
The use of light color inks is commonly used in the preparation of light red, light blue, light tea, and light gray inks, which should be adjusted deeper to improve their color quality, so as to avoid the printer from feeling that the color of the ink is too light, and artificially meet the sample hue Increasing the amount of ink delivery causes the ink layer to be printed too thick, which causes the back of the printed product to become dirty.
During the printing process, the rubber cylinder must ensure sufficient printing pressure when transferring images to the paper, so that the ink is completely transferred on the surface of the blanket to avoid the back of the printed matter from being dirty.
Chalking
phenomenon
Ink pulverization means that after the semi-finished product or finished product is dried, the ink layer cannot be well combined with the paper surface and is slightly rubbed, and the pigment particles on its surface fall off like powder. This pulverization phenomenon has a great relationship with the properties of paper and ink, except that the acidity of the water hopper liquid is too high and there are too many surfactants.
Common causes of ink powdering
The adhesion of the ink is too small and the paper surface is relatively smooth, so that the ink layer and the paper surface cannot be well combined, resulting in the ink layer rubbing off the paper surface.
The ink is too thin, the binding material is easily absorbed by the paper, and a large amount of the binding material penetrates into the paper, causing the binding material and the pigment in the ink to be separated, causing the pigment particles to float on the paper surface, and the pigment loses the adhesion of the binding material. The degree of connection is reduced, so that it does not adhere well to the paper surface, causing peeling.
The ink used is seriously emulsified, which not only reduces the viscosity, drying speed, and increases the amount of penetration, but more importantly, the emulsified ink cannot be well combined with the paper surface after film formation, the adhesion is poor, and the film layer is very strong. A slight rubbing will cause the film to rupture and fall off.
Coated paper is made by coating paint on the base paper. The paint and the base paper have strong absorption, and the paper is thicker, which can absorb a large amount of binder, and the surface of the coating is smooth and the pores are very fine. Inhaled together, it acts as a filter layer, causing the pigment particles to float on the paper surface and fall off due to the lack of wrapping of the binding material.
Approach
Do not use strong absorption coated paper (absorption is less than 30 seconds) to print products, otherwise it must be printed with strong adhesion resin ink.
Appropriate amount of No. 0 ink or adhesive is added to enhance the adhesion of the ink to the paper.
To control the emulsification of the ink, the amount of water used in the layout should be small. Frequently measure the PH value of the water bucket solution and adjust it to the required value. Dry oil should be added with use to reduce ink emulsification so as to master the drying time.
Fine products that have been pulverized can be solved by coating or filming.
Ink flooding
phenomenon
Ink flooding means that the hue of the ink changes and the color changes, so that the printed matter loses its due artistic value. The common ones are golden red and black, sky blue and blue, peacock blue and light blue, and yellow ink and transparent yellow color disappear. And the coloring caused by the heating of semi-finished products or finished products.
Causes of ink flooding
The ink pigment itself is unstable
The acidic potion infiltrates the ink and floods
Oxidative fever reaction
Approach
When the oil-based gold red ink is used, the pigment powder meets iron to produce a chemical reaction, and the hue is extremely easy to blacken. The resin ink is used to avoid the phenomenon of flooding.
The sky blue ink will become reddish after printing on paper for a few days, and the ink color looks darker than the original. This phenomenon should be noted that when the bulk products are printed in batches, the formula of the ink color must be consistent and cannot be changed at will , So as not to cause inconsistencies in product hue.
Peacock orchid, light blue ink meets the chromic acid bucket liquid, the ink color is very easy to yellow, you can use white medicine.
Sunlight can make the finished product fade, and it can be solved by light or film on the printed paper.
In the process of stacking semi-finished products or finished products, it is easy to generate great heat, and the middle is short of oxygen. The time will be slightly longer. The product will become hot and dark. It should be mainly prevention. Ventilate once to accelerate the air flow between the paper, help it diffuse heat and shorten the time to oxidize the conjunctiva.
Reduce the use of cobalt dry oil (that is, 402 red dry oil), because the red dry oil is easy to darken the hue of the ink after heating.
Ink through
phenomenon
The ink part of the printed part penetrates to the back of the paper, and there are obvious imprints or oil stains on the back of the paper, especially for products that require double-sided printing, which is more harmful. In addition to the fact that the paper itself is too thin or has transparency, it affects the quality of the product, and there are other important reasons for the transparent printing of product prints.
Common causes of ink through printing
The ink is too thin and contains too much binder. A large amount of binder is absorbed by the paper and penetrates the back of the paper.
There are too many non-drying linking materials in the ink. Too much non-drying linking material will slow down the oxidative film formation on the surface of the paper, and the penetration and drying will be accelerated.
The ink is printed too thick and dries too slowly, which also causes the binder to penetrate into the paper and print to the back.
The oily pigment contained in the ink is dissolved in the connecting material. During the printing process, the pigment and the connecting material are printed through the paper and printed on the back of the printed product.
Approach
If through-printing has already appeared on the printed product, there is no way to remedy it, only prevent it in advance to prevent the occurrence of through-printing.
Add No. 0 adjusting ink to the ink to increase its viscosity.
Do not use non-drying oil as the linking material, and reduce the proportion of non-drying or highly permeable auxiliary materials.
Increase the color value of the ink, thin the printed ink layer, and accelerate drying.
If the pigment is oil-soluble, it is best to use resin ink for printing.
Print gloss issues
phenomenon
Printed matter is the reproduction of artistic reproduction. It should have bright colors, distinct layers, strong texture, space and material sense. Otherwise, the printed matter will lose its due value.
Common reasons that affect the gloss of printed products
The printing uses low-grade ink, and the product has poor gloss after coloring (except low-grade products).
The surface of the paper is rough, the larger the fiber gap, the stronger the absorption capacity of the binding material. After the ink is transferred to the paper, the binding material is absorbed by the paper fibers most of the time without film formation, and the remaining pigment particles of the ink are attached to The surface of the paper makes the product dull and dull.
Approach
How to make the printed products have better gloss, the actual operation experience tells us that the printing gloss can be obtained from the following aspects:
The gloss of the ink itself is the most basic element. When printing high-end fine products, the ink should be printed with high-end quick-drying bright ink to obtain the best gloss.
When printing, add dry oil to the ink properly to help the good conjunctiva on the surface of the ink, so that the product can get a proper gloss. To correctly grasp the performance and dosage of red and white dry oil, the type and dosage of dry oil have a certain influence on the gloss. No. 402 red dry oil is mainly composed of cobalt citrate. The drying effect is based on the surface oxidized conjunctiva. The drying speed is about 23 times that of white dry oil. Generally, it is added in red ink and black ink, and medium blue and deep blue can also be used. Especially in the latter colors of the same kind of printed matter, if the red and dry oil can be added to the maximum, this will have a good effect on increasing the gloss of the printed matter. When the yellow version is used as the first color sequence, it is not advisable to add red dry oil, because the color of the red dry oil will change the hue of the yellow ink, followed by the largest amount of yellow ink, and excessive drying is prone to vitrification.
White dry oil is a mixture of metal salts of cobalt, manganese, and lead. It has a comprehensive drying effect, but it is not as strong as red dry oil. The correct amount of white dry oil added will have an effect on increasing the gloss of the printed matter.
Apply varnish or film to the surface of the finished product.
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