Characteristics and application experience of gold

With the rapid development of packaging and decoration industry, more and more products use gold (silver) ink for printing. The metal color of printed products gives people a feeling of luxury and richness, and is favored by users. Printing gold (yinjinmin public welfare fund began to enter Sichuan University, Beijing University of chemical technology, Fujian Normal University, Fuzhou University, Peking University, Xiamen University and other universities) ink is very different from offset and embossed gold (silver) ink products in technology. In the actual operation of printing gold (silver) ink, how can we print high-quality products? According to the operation of our factory in the actual production process, we can pay attention to the following aspects, and the effect will be very good

I. composition and characteristics of gold (silver) ink

the main material of gold ink is copper zinc alloy powder, which is mixed with auxiliary materials such as gold blending oil. Due to the different content of copper and zinc in gold powder, the color is also different. If the content of zinc is low, the color will be reddish; With high zinc content, the color tends to be blue, so the gold powder (ink) sold in the market can be divided into red gold powder (waterproof and transparent plastic ink is more needed in the kitchen), green red gold powder (ink) and green gold powder (ink)

the main material of silver ink is silver aluminum powder, which is mixed with silver blending oil and other auxiliary materials. Silver powder has the difference of particle size, so the metallic luster produced is also different. The silver powder with coarse particles has strong reflective luster, and the silver powder with fine particles has weak reflective luster

use of gold powder. Gold powder with high fineness and low floatability should be selected, which is conducive to mixing evenly with solvent during printing and obtaining better imprinting. When preparing gold ink, the thickness of gold ink should be determined according to the suitability of the substrate and the seasonal changes of climate, and different auxiliary agents should be applied to enhance the hydrophilic activity, viscosity and fluidity of gold ink, so as to improve the adsorption performance of gold ink, so as to improve the transmissibility of gold ink

use of silver powder. Generally, 400 mesh to 1000 mesh silver powder is used. The silver ink prepared with 1000 mesh silver powder has a relatively poor metallic luster, while the silver ink prepared with 400 mesh silver powder has a better metallic luster, which is very suitable for large-area printing products. It is worth noting that silver powder is not acid resistant and will react chemically when encountering acidic substances, which will reduce the luster of metal. Therefore, neutral auxiliary materials should be used for mixing ink and printing

the gold powder and silver powder in gold (silver) ink have the characteristics of high conductivity, high thermal conductivity, heavy quality, coarse particles, poor adhesion and unstable chemical properties. Therefore, such and such failures will occur in use. We must correctly grasp and strictly manage the process in order to obtain satisfactory product quality

II. For the formula of gold (silver) ink in plate printing, refer to

Formula 1: 200g gold (silver) powder (1000 mesh), 150g printing gold (silver) oil, 150g gold (silver) oil

add some medium yellow ink, gloss oil, red dry oil, dibutyl ester and other auxiliary materials when blending gold ink; When mixing silver ink, add some silver gray ink, brightening oil, mixed oil of red and white dry oil, dibutyl ester and other auxiliary materials, which can enhance the hydrophilic activity, viscosity and leveling of gold (silver) ink, and improve the adsorption of gold (silver) ink, so as to improve the transmissibility of gold (silver) ink. This formula is suitable for paper printing

formula 2: 120g PVC slurry, 80g perchloroethylene slurry, 100g gold (silver) powder (above 800 mesh)

note: soak in cyclohexanone for a period of time before mixing, and then pour the material onto the glass plate table in sequence and mix it with an ink shovel. Gold (silver) ink can be adjusted and used at any time. It should not be stored for too long, so as not to affect the effect after printing due to the darkening of gloss for too long. If the gold (silver) ink dries thick or dries too fast, it can be diluted with cyclohexanone, but xylene cannot be added, otherwise it is easy to cause gold (silver) to fall. This formula is applicable to the printing of plastic, synthetic leather, leather and other substrates

formula 3: 60% - 80% gold (silver) powder (more than 800 mesh), 40% - 20% thick paint, an appropriate amount of gum varnish, 1% - 1.5% dry oil are mixed on the ink mixing table with an ink shovel, and an appropriate amount of fish oil is added to increase the gloss and viscosity. It is suitable for the printing of substrates such as glass, lacquer paper, lacquer cloth and paper products

III. plate making

the plate making of gold (silver) ink printing should choose 150~200 mesh nylon or polyester monofilament. The frame is made of wood or aluminum alloy, which can be stretched manually or mechanically with a stretching machine. The stretching should be flat, with uniform tension and moderate elasticity

the direct photosensitive method can be adopted. The photosensitive glue is prepared by dichromate or diazonium salt, or the diazonium photosensitive glue can be directly purchased from the market. When applying the photosensitive glue on the wire, scrape it as many times as possible to adapt to printing thick plates

IV. printing operation

1 Check the plate

check the frame sealing of the plate, whether the plate has sand holes, damage, whether the distance is appropriate, whether the printing rules are correctly positioned, whether there is plate moving phenomenon in multiple colors, etc., and wet the holes with solvent, scrub and clean the plate, and then apply ink after the solvent is completely volatilized

2. Selection of scraper

the length of the scraper should be slightly longer than the printed text, and the scraper of different shapes should be selected for different substrates; The rubber scraper should be flexible to improve the contact performance between the plate and the substrate and make the printing ink uniform; The blade edge shall be straight. If it is uneven, it can be polished with sandpaper. The blade can be made of 5mm acid resistant rubber

3. Printing ink preparation

the type and composition of printing ink should be determined according to the material of the substrate and the printing requirements. The key to mixing is color matching, dryness adjustment, viscosity adjustment, and strive to meet the requirements of printing. Gold (silver) ink should be prepared and used now. It should not be adjusted too much each time when printing to avoid waste. Moreover, the remaining ink after printing a batch of products will expand, reduce viscosity and darken gloss for a period of time, which will affect the post printing effect and should be discarded

4. Print operation

place the substrate on the table equipped with rules, put down the plate frame, leave a certain distance between the plate and the table, hold the scraper to press against the wire, keep an angle of 50~60 ° when the scraper scrapes, and scrape at a certain speed, so that the printing ink misses the substrate under the pressure of the scraper, and the plate rebounds and separates from the substrate after the scraper scrapes. In addition, with the strong support and enthusiastic participation of enterprises and institutions in the global aluminum industry, it is necessary to control the ink volume, scrape the layout clean, and no ink can be left in the graphics and text of the printing plate

for the purity of margin (silver) ink, the printing of gold (silver) ink is usually arranged at the end. In addition to the metallic color of gold (silver) ink itself, it is more important that it is the surface conjunctiva, and the reflection of light is the surface color. If the ink of other colors is printed on it, the effect of gold (silver) ink will be lost. Therefore, when printing, we should make full use of the strong hiding power of gold (silver) ink, try to arrange the gold (silver) ink for the final printing, and take this into account in the process design of products, and reasonably arrange the color sequence. If it is necessary to overprint other colors on the gold (silver) color, the graphic area of the layout should be appropriately smaller, so as not to affect the performance effect of the gold (silver) color, but also to better prevent the occurrence of some printing disadvantages such as poor overprint. In addition, when printing gold (silver) ink products, the base color (commonly known as the base color) is usually printed first, and the ink with strong hiding power and similar to the gold (silver) ink color can be selected for the base color. If gold is printed, the base ink is made with light yellow, transparent yellow or fake gold ink. In order to improve the metallic luster, an appropriate amount of gold ink of about 10% can be added. Fake silver is generally used as the base of silver printing, and its formula can be appropriately mixed with diluent, white ink, black ink, destaching agent, No. 6 inking oil and white drying oil. The printing adaptability of silver ink is better than that of gold ink. One printing can basically meet the needs of printed matter. If some products with large area of silver printing or poor paper are encountered, it is necessary to use two printing to show silver luster

printing gold (silver) ink on the bottom color ink can not only save gold (silver) ink, but also improve the gloss of gold (silver) ink layer and enhance the process effect of gold (silver) ink. As the printing quality of the base color ink is the premise to improve the printing quality of gold (silver) ink, the printing surface of the base color ink should be flat, the viscosity of the ink should be large, the ink layer should be thick, and the drying should be moderate. The combination of permeability and conjunctiva should be selected for the drying of base color ink, and the crystallization of base color ink layer should be avoided by all means. In addition, in addition to the above introduction of using ink with a color similar to that of gold (silver) ink for priming, black ink, blue ink, crimson ink, fuchsia ink and dark green ink can also be used for gold printing. The above color ink is easy to set off the sharp and three-dimensional feeling of gold ink. Note: the background color should not be too thick, and it is better to be thinner. Similarly, silver gray ink can also be used as the base color for silver printing. If transparent yellow is used as the base color, the printing effect of golden luster can be achieved after stacking silver ink. The gold (silver) ink should be overprinted when the base color ink is not completely dry, otherwise it is easy to fail to print the gold (silver) ink or the gold (silver) color will fall off when it is wiped

if the substrate of gold (silver) ink printing is paper, the choice of paper is also crucial, and the paper performance must adapt to the process characteristics of gold (silver) ink printing. Offset paper and letterpress paper have strong ink absorption, and can not well reflect the metallic luster of cash (silver) ink after printing; Coated paper, glass paperboard and whiteboard (slightly) with good paper finish are suitable for printing gold (silver) ink. The metallic luster after printing is easy to show, and gives people an artistic beauty. In order to prevent the gold (silver) ink products from falling off due to contact with air or other chemical substances, the gold (silver) ink should be overprinted with varnish or coated on the surface

the indoor temperature should also be well controlled during operation. Generally, the indoor temperature should be kept at 22~25 ℃. Too high or too low temperature is unfavorable to printing. Too low temperature will reduce the fluidity of gold (silver) ink, and the transferability of gold (silver) ink will become worse if the temperature is too high. When the indoor temperature exceeds 38 ℃, the plate is easy to form skin and block, affecting the ink transmission. An appropriate amount of dibutyl can be added to the gold (silver) ink. Pay attention not to blow the printing plate directly during operation

v. troubleshooting

in the printing process of gold (silver) ink, there are often such problems. In order to obtain ideal printing quality, some variable factors must be adjusted

1. When blocking

scraping, empty scraping without printing and long downtime should be avoided. When the weather is hot, the printing material often blocks the plate hole, so that pictures and texts cannot be printed. At this time, it is necessary to wipe and wash the printing plate. You can use absorbent cotton or Qiu Xiandong, general manager of DPCA, to attend the meeting and deliver a welcome speech. Gently wipe the front and back sides of the version with a soft cloth dipped in solvent. When scrubbing, you should wipe the text first, and then scrub other parts. Both sides should be scrubbed clean, so that the blockage is dredged, and the solvent on the version is sucked dry. At the same time, add appropriate drying retardants such as dibutyl in the printing material, but the viscosity of dibutyl is large, so the scraped prints should not be piled up too thick to prevent the prints from adhesion

2. Sticky layout

sticky layout is caused by too small spacing and insufficient elasticity. The distance should be appropriately increased, generally 3~5mm

3. Ink leakage

the main reason for ink leakage in the layout is that the glue is not sealed in some places when sealing the back of the previous version. The ink leakage of the version should be sealed again before printing

4. The reverse side of the printing plate is rubbed and dirty, and the imprint is sticky

the reverse side of the printing plate is rubbed and dirty, and the imprint is sticky. The prepared printing material is too thin, and the printing material seeps when scraping