Talking about the faults caused by the ink printing process and the treatment methods
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The imprint left on the printed matter is formed by ink. The ink is a coloring agent for printing. It is the main raw material for printing. The ink is very important for the quality of printing. When the ink performance is not suitable for printing, it will cause a series of processes. Failure, seriously affecting the progress of production and the quality of the product. The print operator must change certain properties of the ink to suit the needs of the print, but some faults are not only caused by the ink, but also related to other factors, so the print operator must carefully analyze the correct treatment. This article discusses the faults and treatment methods caused by the ink printing process, and hopes to be helpful.
First, the blot is dry slowly
Phenomenon and cause: After the printing plate is transferred from the printing plate to the paper by the blanket, it is generally required to be dried in about 10 hours to facilitate the printing of the back color or the inspection of the finished product. Once the printing is slow, the next color cannot be Overprinting, and it is very easy to make the back of the print dirty. The drying of the blot has three factors: oxidized conjunctiva, paper absorption, and water evaporation. We must correctly control the operation and prevent it in advance. The reasons why common blots are slow to dry are as follows:
(1) The paper has a PH value of 6 or less.
(2) The water bucket has a pH value of 3 or less.
(3) The layout of the water is large, and the ink is very emulsified by the ink.
(4) The workshop temperature is low. Relative humidity is above 75%.
(5) Paper absorbability is poor.
(6) There are too many auxiliary materials such as varnish and debonding agent in the ink.
(7) The amount of dry oil is too small.
Approach:
(1) In order to prevent the phenomenon of slow drying of printed matter, the height of stacked printed products should be reduced, and the pile of paper should be shaken. The semi-finished product can allow air to penetrate into the stacked paper and shorten the time of oxidation and conjunctiva.
(2) If the printing is urgently needed, use the original graphic printing plate for dry oil overprinting, the formula is 70% of Wei Li oil and 30% of dry oil.
(3) In order to prevent unfavorable drying factors, add appropriate amount of dry oil. The amount of dry oil is: winter is more than summer, the latter color is more than the previous one, and the diluted ink is more than the diluted ink.
Second, the color can not be printed
Phenomenon and cause: Excessive dry oil is added into the ink or the semi-finished product is stacked for too long, causing too fast drying to cause vitrification on the surface of the imprint. The surface of the imprint is too smooth, and the adsorption capacity is lost, and the latter color cannot be printed. This type of fault is common in the full version of the field, especially the yellow (ink) or line pattern prints.
Approach:
(1) Precaution-based. Precisely add a suitable amount of Wei Li oil, Kang Bang, magnesium carbonate powder and other auxiliary materials to the yellow ink which is easy to vitrify, so that the surface of the yellow film is rough or the drying time is prolonged.
(2) If the vitrification phenomenon has occurred and the latter color is not printed, if the product quantity is small, use a soft cloth of magnesium carbonate powder to gently rub on the surface ink film of each sheet, and then set the color, if The quantity is large, and it can be printed on the edge of the soda caustic water.
Third, the back is dirty
Phenomenon and cause: The back side is dirty. After the semi-finished product or finished product enters the delivery pile, the ink on the back side is stained by the ink on the next sheet. The reason for the back adhesion is.
(1) The surface of the paper is too smooth.
(2) The ink is too thin.
(3) The layout is large and large.
(4) The ink color is too light.
(5) The printing pressure is too light.
Approach:
(1) In the printing process, there should be no occurrence of large water and large ink, control the moisture of the layout, darken the ink, and reduce the ink volume of the ink fountain. If the water is reduced to produce greasy or paste, clean the water roller or replace the new water roller, or properly strengthen the acidity of the water fountain and put some gum arabic.
(2) The ink is adjusted too thin and easy to stick to the back of the printed product. The new ink should be exchanged or some new ink should be transferred to increase the viscosity of the ink.
(3) The use of light-coloured ink is common in the blending of light red, light blue, light tea, and light gray ink. It should be deeper, improve its color quality, and avoid the printer's feeling that the ink color is too light, in order to achieve the sample color. It is required to artificially increase the amount of ink, which causes the ink layer to be printed too thick to cause the back of the print to be dirty.
(4) During the printing process, the blanket cylinder should ensure sufficient printing pressure when transferring the paper to the paper, so that the ink is completely transferred on the surface of the blanket to avoid the dirt on the back of the printed matter.
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Fourth, chalking
Phenomenon and cause: Ink pulverization means that after the semi-finished product or the finished product is dried, the ink layer can not be well combined with the paper surface, and the surface of the pigment granules will fall off like a powder. This pulverization phenomenon has a great relationship with the properties of paper and ink, except that the water syrup is too acidic and contains too much surface active material. Common ink pulverization has the following reasons:
(1) The adhesion of the ink is too small and the surface of the paper is relatively smooth, so that the ink layer and the paper surface are not well combined, resulting in the ink layer being wiped off from the paper surface.
(2) The ink is too thin, the binder is easily absorbed by the paper, and a large amount of the binder penetrates into the paper, causing the binder to separate from the pigment, causing the pigment particles to float on the paper surface, and the pigment loses the binder. Adhesion, the degree of bonding is lowered, so that it does not adhere well to the paper surface, causing shedding.
(3) The used ink is emulsified severely, not only reducing the viscosity, drying speed, increasing the amount of penetration, but more importantly, the emulsified ink is not bonded to the paper surface after the film is conjuncted, the adhesion is poor, and the film layer is firm. Very poor, a slight rub will cause the film to rupture and fall off.
(4) Coated paper is coated on the base paper. The paint and base paper have strong absorption, and the paper is thicker and can absorb a large amount of binder. In addition, the surface of the coating is smooth and the pores are very fine. It is possible to inhale the pigment together and act 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 binder.
Approach:
(1) It is not necessary to print the product without strong absorbent paper (absorbability is less than 30 seconds), otherwise it must be printed with a strong resin ink.
(2) Add the No. 0 varnish or adhesive to the paper to enhance the adhesion of the ink to the paper surface.
(3) Control the emulsification of the ink, and the water consumption of the plate should be small. Frequently measure the pH value of the water bucket solution and adjust it to the required value. The dry oil should be added as needed to reduce the ink emulsification to facilitate the drying time.
(4) Fine products that have been powdered can be solved by glazing or filming.
Five, ink color
Phenomenon and cause: The color of the ink is the change of the hue of the ink, and the color changes, which makes the printed matter lose its artistic value. Commonly, there are gold red black, Tianlan pan blue, peacock orchid and pale blue yellow.
Yellow ink and transparent yellow color disappear, and the color of the semi-finished or finished product is caused by heat generation. The reasons for the above drawbacks are:
(1) The ink pigment itself is unstable.
(2) The color of the acidic drug solution is infiltrated into the ink.
(3) Oxidative exothermic reaction.
Approach:
(1) When the oily gold-red ink is used, the pigment powder reacts with iron to produce a chemical reaction, and the hue is easily blackened. The resin ink is used instead of the bluing phenomenon.
(2) Tianlan ink printing will be red on a few days after the paper, and the ink color looks deeper than the original. This phenomenon should be noted that when the bulk products are printed in batches, the ink color modulation formula must be consistent. Do not change at will, so as not to cause inconsistencies in product hue.
(3) Peacock orchid, light blue ink meets the chromic acid water bucket liquid, the ink color is easy to yellow, and can be changed to white medicine water.
(4) Daylighting can fade the finished product, which can be solved by printing or printing on the printed paper.
(5) During the stacking process, the semi-finished products or finished products are prone to generate a lot of heat, and the middle part is also deficient in oxygen. The time is longer, the product will be hot and dark, and should be based on prevention. The product stacking should not be too high, and should be guaranteed 4 Ventilate once every -6 hours to accelerate air flow between the papers, helping them to dissipate heat and shorten the time to oxidize the conjunctiva.
(6) Reduce the use of cobalt dry oil (ie 402 red dry oil), because the red dry oil is easy to make the hue of the ink dark after heating.
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Six, ink throughprint
Phenomenon and cause: The ink part of the print penetrates into the back of the paper, and there are obvious imprint patterns or oil stains on the back of the paper, especially for products requiring double-sided printing. Affect the quality of the product, resulting in the printing of the product. In addition to the paper itself is too thin or transparent, the common reasons for ink penetration are as follows:
(1) The ink is too thin and contains too much binder, and a large amount of binder is absorbed by the paper and penetrates to the back of the paper.
(2) There are too many non-drying binders in the ink. Too much non-drying binder will slow down the oxidized conjunctiva on the paper surface, and the percolation drying will accelerate. A large amount of binder will penetrate into the paper and pass through to the back. .
(3) The ink is printed too thick and the drying is too slow, so that the binder is infiltrated into the paper in a large amount and is printed on the back side.
(4) The oily pigment contained in the ink is dissolved in the binder. During the printing process, the pigment is printed on the paper together with the binder and is printed on the back side of the print.
Approach:
If there is already a print-through on the printed product, there is no way to remedy it. Only prevent it in advance to prevent the phenomenon of offset.
(1) Add 0 varnish to the ink to increase the adhesion.
(2) Do not use non-drying oil as the binder, and reduce the proportion of excipients with strong dryness or permeability.
(3) Increasing the color value of the ink, thinning the imprinted ink layer, and accelerating drying.
(4) If the pigment is oil-soluble, it is preferable to use a resin type ink for printing.
Seven, print gloss
Phenomenon and reason: Printed matter is a reproduction of artistic reproduction. It should be bright in color, clear in layer, with strong sense of texture, space and material. On the contrary, printed matter will lose its due value.
The common reasons that affect the gloss of printed products are as follows:
(1) Low-grade ink is used for printing, and the gloss of the product is poor after coloring (except for low-end products).
(2) The surface of the paper is rough, the larger the fiber gap is, the stronger the absorption capacity of the binder is. After the ink is transferred to the paper, the binder is absorbed by the paper fiber in the case of unconjuncted film, and the pigment of the ink remains. The particles are attached to the surface of the paper, thus making the product dull.
Approach:
How to make the printed products have better luster, the actual operating experience tells us that the gloss of the printed products can be obtained from the following aspects:
(1) The gloss of the ink itself is the most basic element. When printing high-grade fine products, the ink should be printed with high-grade fast-drying bright ink to obtain the best gloss.
(2) Adding dry oil to the ink during printing to help the film to form a good conjunctiva, so that the product obtains proper gloss. To correctly grasp the performance and dosage of red and white dry oil, choose the type and amount of dry oil to have a certain effect on the gloss. No. 402 red dry oil is mainly composed of cobalt ruthenate. Dry speed is about 23 times that of white dry oil. It is usually added in red ink and black ink. Zhonglan and deep blue can also be used. Especially for the latter colors of the same type of printing, if the red dry oil can be added to the maximum, this will have a good effect on increasing the gloss of the printed product. When the yellow plate 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, and the yellow ink is the largest. The drying is extremely prone to vitrification. White dry oil is a mixture of metal salts of cobalt, manganese and lead, which has a full-drying effect, but 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.
(3) Apply a bright oil or film to the finished product surface.
Ink is a complex colloid formed by mixing pigments, binders and additives. Its properties are mainly determined by the properties of pigments and binders. It completes the drying of printed blots by volatilization, permeation and oxidized conjunctiva. As the main material of printing, understanding the composition of ink, familiar with the performance of ink, and correctly mastering the use of ink, it is a necessary condition to ensure the quality of printing.