Overview of the printing of the most popular alumi

Overview of aluminum spray paper (board)

aluminum spray paper (board) is a kind of high-grade packaging and printing paper made of common white paper (board). Many of its advantages have long been known by insiders. However, due to the structural relationship of aluminum spray paper (board), such as the non absorbability of the surface, it is different from the printing process conditions of ordinary white paper (board), and first-time users often encounter some problems. Now the main points of attention of aluminum spray paper (board) in printing are stated below for reference, hoping to be useful to printing operators

offset printing:

1. full oxidation drying ink should be used. (plastic and aluminum foil special inks)

2. The amount of anti adhesion powder spraying must be kept to a minimum. Excessive use of powder spraying will cause wear on the printing surface. Make the surface rough and dull

3. Keep the stacking height of the post press paper at about 300mm. Reduce the stacking pressure before the post press paper is completely dried. If you are not careful, scrape the sheet metal to avoid adhesion

4. in order to facilitate drying, it is recommended to thin the ink layer. Some printing requires an ink layer with strong hiding power. This thick ink layer printing can be achieved by printing twice in one color (overprint)

5. if possible, you should use clean water (deionized water or distilled water) to moisten the plate. If you use moistening solution, it should not be too acidic (pH = 5.5) and should be used in a small amount, because it will affect drying. Sometimes it may be necessary to add up to 15% isopropanol to the fountain solution to reduce the surface tension and the amount of water brought to the paper (board)

6. generally, it can be used according to the ink viscosity supplied by the manufacturer. If it is necessary to adjust the viscosity, it must be according to the supplier's instructions. Mineral oil and paste thinner should be avoided

7. additives can be added to the fountain solution to help dry, but everything should be done according to the ink manufacturer's recommendations. Runban is now basically stable at 140000 yuan/ton and must cross the width to avoid excessive moisture on the edge of the paper (board). It is recommended to add an appropriate amount of desiccant to the ink to ensure solid drying

the temperature of the fountain solution is generally controlled at 10 ℃ - 15 ℃, and the temperature and dosage of the fountain solution are controlled to prevent excessive emulsification of the ink, so as to prevent the problems of imprinting and broken marks and poor printing caused by the back and forth switch of the electrical appliance

8. Generally speaking, the viscosity of the second color ink is slightly lower than that of the first color ink. (the so-called surface non absorbability of aluminum spray paper, strictly speaking, there is still a small amount of absorbability). Excessive increase of printing pressure will cause aluminum loss, which is undesirable

9. the surface of aluminized paper is relatively smooth, and sometimes there will be slight paper adhesion. When feeding paper, blow the air moderately to ensure smooth feeding

UV ink printing: UV curing ink is very suitable for printing on aluminum sprayed paper (board). Use ultraviolet light to achieve instant and rapid drying effect (actually absorb UV energy and cause monomer polymerization to form a solid liquid ink). While radiating UV energy, heat will also be brought to the surface of the substrate material. Be careful when printing to avoid excessive heating of the paper surface, because this will make the surface of aluminum sprayed paper lose its metallic luster texture. It is recommended that the long-term surface temperature of paper (board) should be less than 40 ℃. That is, the paper (board) should be fully cooled after printing and before stacking

UV glazing: there will be considerable differences in the quality of UV oils. Some UV oils contain a certain amount of aliphatic amines and surfactants. In order to reduce potential problems, we should choose high-quality glazing inks. On the premise of ensuring good transparency and surface protection, it is better to apply a small amount of varnish, which will also be beneficial to reducing costs. When aluminum spray paper (board) is used as packaging material, too thick glazing oil layer is easy to cause the disadvantage of too shallow packaging crease line. At this time, if you want to maintain the depth of the crease line, it will cause apparent problems such as fine cracks or ink bursts

sometimes it is better to polish 24 hours after printing

silk printing: it is recommended to contact the ink manufacturer and conduct printing production test in advance in order to establish processing parameters. When printing, we should also pay attention to avoid transferring excessive heat to the surface of aluminum spray paper

gravure and flexographic printing: traditional printing ink can be used. Due to the non absorbability of the material surface (ink), it needs to be adjusted to reduce the drying degree. The temperature of the drying oven should not be too high. Too high a temperature will cause excessive drying and water loss of the paper base, causing changes in the dimensional stability of the material, resulting in inaccurate printing of the working principle diagram of the pulsating fatigue testing machine. Generally, the drying temperature should be less than 75 ℃, and the drying temperature of 50 ℃ is often used (ink with high proportion of quick drying solvent can be used). If the length of the drying oven is short, the printing speed should be slower. If the length of the drying oven is long, the printing temperature can be lower. It should be noted that the time for printing materials to pass through the drying oven should not be too short

the ink should be allowed to dry, otherwise the residual solvent in the ink will penetrate into the surface coating of the sealed aluminum paper (board), which will cause problems such as surface paste, cracking and other surface coating damage

use the oven to dry the printing ink, Its dryness can be comprehensively considered in combination with the following points:

1. Printing speed

2. Drying temperature and number of temperature zones in the oven

3. Drying wind speed

4. Oven length

5. Characteristics of printing coating (solvent type and solvent release performance of ink resin, solid content)

6. Thickness of printing coating (wet coating printing volume, i.e. depth and number of lines of printing line roller, printing area)

7. paper base thickness

of course, the adjustment of drying degree is mainly to determine the speed of printing and the level of drying temperature according to the characteristics and thickness changes of printing coating and the thickness of paper base

at the same time, it is recommended to use ink with less plasticizer (such as DOP), which can prevent some adhesion problems

plastic and aluminum foil special gravure printing inks are very suitable for printing on aluminum sprayed paper (board)

environmental conditions:

to avoid paper edge deformation, balance the paper and paper roll to the temperature of the printing workshop 24 hours before printing, and then unpack and start printing before printing. The greater the temperature difference, the longer the balance time is required, sometimes up to several days. The temperature and humidity of the printing workshop should be kept at 20-25 ℃, 50-60% RH. In the process of storage and printing processing (such as ink printing drying, cutting, bronzing, die cutting, finishing processes, etc.), too high or too low temperature and humidity must be avoided. If the time interval between work and sequence is long, it is necessary to temporarily moisture-proof package semi-finished products, which will play a good role in the smooth progress of subsequent processing

printing on aluminum spray paper (board) is similar to printing on plastic and aluminum foil. Ink drying requires evaporation and/or oxidation process. Due to the non absorbability of the surface, the ink drying of offset printing is slower than that of ordinary white paper (board). The rise of ambient temperature or the decline of humidity is certainly conducive to the oxidation drying of printing ink on aluminum spray paper, but it is not conducive to the flatness of paper

in addition, the stacking height of aluminized paper (board) before printing should be cut; When the aluminum coated paper is stored on two pallets and reels, the end face is facing down (the so-called eye is facing up), so as to prevent the adhesion or surface damage of the paper. Because the aluminum spray paper (board) has a good metallic luster, compared with ordinary paper, the surface of the paper is greatly affected by the outside world. It is obvious that the surface of the aluminum spray paper (board) is damaged. Therefore, the aluminum spray paper (board) should be prevented from excessive pressure during transportation and storage

suggestion: there is a process of exploration, familiarity and experience accumulation for the printing of aluminum spray paper (board). In addition to the above, to sum up, pay special attention to the following two points

1. temperature:

if the surface temperature of aluminum spray paper (board) is improper (or too high) in the printing process, its retention heat will soften the resin coating on the surface of aluminum spray paper (board) and deform, resulting in the loss of metal luster and texture

using the metal texture of aluminum spray paper (board) and properly mixing transparent and opaque inks will make the printed image have a three-dimensional sense. Of course, it needs to keep the metal luster intact in the printing process to achieve a beautiful effect

2. Humidity:

environmental humidity will affect the retention and loss of moisture in aluminum spray paper, resulting in the curling of aluminum spray paper. Too low environmental humidity will cause the loss of moisture in aluminum spray paper, and aluminum spray paper will curl to the opposite side of aluminum. On the contrary, too high environmental humidity will cause the increase of moisture in the aluminum spray paper, and the aluminum spray paper will curl towards the aluminum surface

generally, the relative moisture content of aluminum spray paper is 4.5-5.5%. For printing with drying ink in an oven (such as gravure printing and flexo printing), the relative moisture content of aluminum spray paper is generally lower than 4.5% after printing. At this time, the moisture can be properly added back to the paper, and the relative moisture content of aluminum spray paper can be maintained at the level of 4.5-5.5% before printing, so as to prevent the paper from curling towards aluminum painting in the ordinary environment, And affect the use

compared with aluminized paper, aluminized paper board has a larger stiffness and is not easy to curl due to the influence of environmental humidity (similarly, 1 g of moisture changes, accounting for 1% for 100 g of paper, and only 0.5% for 200 g of paper)

conclusion: in order to obtain good packaging prints when printing enterprises use aluminum spray paper (board), in addition to having excellent printing machinery and equipment and good printing technology; We should be familiar with the characteristics of the two raw materials aluminum spray paper (board) and ink. We should choose and use the appropriate ink. Combined with the above-mentioned points of attention, it will certainly play a role in improving the printing quality and reducing the cost with half the effort

reprinted from: cpnic