Screen printing gold (silver) ink characteristics and experience

With the rapid development of the packaging and decorating industry, more and more products using screen printing gold (silver) ink, the metal color of the printed product gives people a feeling of luxury and rich, much favored by users. Screen printing gold (silver) ink and offset printing and embossing gold (silver) ink products are very different in the process. In the actual operation of screen 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.

First, the composition of gold (silver) ink and characteristics

The main material of gold ink is copper-zinc alloy powder, which is formulated with auxiliary materials such as gold transfer oil. Due to the different content of copper and zinc in the powder, the color is also different, the amount of zinc is low, and the color is reddish; the zinc content is high, the color is partial green, so the gold powder (ink) sold in the market has red powder (ink), Green red powder (ink), green powder (ink) points.

The main material of the silver ink is a silvery aluminum powder that is formulated with auxiliary materials such as silver regulating oil. Silver powder has a difference in particle size, so the resulting metallic luster is not the same. The coarse silver particles reflect a strong luster, and the fine silver particles have a weak reflection and luster.

The use of gold powder. Should choose a high degree of fineness, low floating gold powder, which is conducive to printing and solvent evenly distributed, and get a better print. In the deployment of gold ink, the dilute consistency of gold ink shall be determined according to the suitability of the substrate and seasonal changes in the climate, and different auxiliary agents shall be applied to enhance the affinity, viscosity, and fluidity of the gold ink so that the adsorption performance of the gold ink is obtained. Improve, thereby improving the transitivity of gold ink.

The use of silver powder. 400-1000 mesh silver powder is generally used. Silver ink formulated with 1000-mesh silver powder has relatively poor metallic luster, while 400-mesh silver powder blended with silver ink has better metallic luster and is suitable for large-area printing products. It is worth noting that the silver powder is not acid-resistant. When it encounters acidic substances, it will cause a chemical reaction and reduce the metallic luster. Therefore, neutral auxiliary materials should be used for preparation of inks and printings.

The gold powder and silver powder in the gold (silver) ink have the characteristics of high electrical conductivity, high thermal conductivity, heavy weight, coarse particles, poor adhesion, and unstable chemical properties. Therefore, such failures will occur during use and must be correctly grasped. Strict process management in order to obtain satisfactory product quality.

Second, screen printing, gold (silver) ink formula reference

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

When adding gold ink, add some medium yellow ink, bright oil, red dry oil, dibutyl ester, etc.; mix silver oil, bright oil, red dry oil, and white dry oil when adding silver ink. The butyl ester and other additives can enhance the pro-activity, viscosity and leveling of the gold (silver) ink, so that the adsorption of gold (silver) ink can be improved to facilitate the improvement of the transferability of the gold (silver) ink. Suitable for printing on paper.

Formula 2: polyvinyl chloride slurry 120g, vinyl chloride slurry 80g, gold (silver) powder (above 800 mesh) 100g

Note: Before blending, soak in cyclohexanone for a period of time, and then pour the material on the glass plate table in order to mix with the ink scoop. Gold (silver) ink is used with the tone, it should not be stored for too long, so as to avoid long-time gloss and affect the effect after printing. If the gold (silver) ink is thick or dried too quickly, it can be diluted with cyclohexanone, but xylene cannot be added or added. Otherwise, gold (silver) is easily lost. This formula is suitable for the printing of plastic, synthetic leather, leather and other substrates.

Formula 3: Gold (silver) powder (800 mesh or more) 60% to 80%, thick paint 40% to 20%, fat gel varnish amount, dry oil 1% to 1.5% on the ink leveler with ink shovel for deployment, Appropriate amount of fish oil is added to increase luster and viscosity, suitable for the printing of substrates such as glass, lacquer paper, lacquer cloth and paper products.

Third, the screen production

Gold (silver) ink screen printing should use 150 to 200 mesh nylon or polyester monofilament mesh. The frame is made of wooden frame or aluminum alloy frame. Manual stretch netting or stretching with a stretcher can be used to stretch the net. The stretch net should be smooth, even in tension, and moderate in elasticity.

Direct sensitization method can be adopted. Photosensitive adhesive can be prepared by using dichromate or diazonium salt, or can be purchased directly from the market. Apply as many times as possible on the screen to make it suitable for screen printing. .

Fourth, print job 1. Check the screen

Check the sealing frame of the screen, whether the screen has holes, damage, network spacing is correct, the printing rules are positioned correctly, there are many sets of color with or without the phenomenon of walking, etc., and use the solvent to wet the mesh, scrub the clean plate, until the solvent is completely volatilized After the ink job.

2. Selection of scraper

Scraper length should be slightly longer than the printed graphics, different substrates should use different shapes of the scraper; squeegee should have a certain degree of flexibility, in order to facilitate the improvement of the screen and the substrate contact properties, so that the ink is uniform; scraper mouth requirements flat Straight, if uneven can be sanded, the blade can be made of 5mm acid resistant rubber.

3. Printing ink preparation

The type and composition of the ink should be determined according to the material of the substrate and the printing requirements. The key is to adjust the color, adjust the dryness, adjust the viscosity, and try to adapt to the printing requirements. Gold (silver) inks should be used as they are, and each time printing should not be deployed too much to avoid wastage, and the residual ink remaining after the printing of a batch of products will be stored for a period of time will swell, the viscosity will decrease, and the gloss will darken. Affect the post-press effect, should not be used again.

4. Screen Printing

Put the substrate on the platen with rules, put down the screen frame, and leave a certain distance between the plate and the platen, press the blade against the screen, and keep the angle of 50~60° when the blade is scraped. , And with a certain speed of ink scraping, so that the ink under the pressure of the scraper, missing printed on the substrate, the scraper scraped off after the screen plate rebound and the substrate separation. In addition to control the amount of ink, the layout should be scraped clean, there can be no ink on the printing plate at the graphic.

In order to guarantee the purity of the gold (silver) ink, the printing of gold (silver) ink is usually arranged at the end. In addition to its metallic color, gold (silver) ink, more importantly, it is the surface of the conjunctiva, the reflection of the light is the surface color, if it is printed on the ink of other colors then it will lose the effect of gold (silver) ink . Therefore, in printing, the strong hiding power of gold (silver) ink should be fully utilized. The gold (silver) ink should be arranged as far as possible in the final printing. This should also be taken into account in the process design of the product and the color sequence should be reasonably arranged. If it is necessary to superimpose other colors on the gold (silver) color, the area of ​​its layout should be appropriately smaller, so as not to affect the performance of gold (silver) color, but also to prevent some defects such as poor printing of overprinting. Produce as well. In addition, when printing gold (silver) ink products, the background color is generally printed first (commonly known as the background color), and the ink with the strong hiding power and the similar color to the gold (silver) ink may be used as the base color. If gold is printed, the ink is primed with a yellowish, clear yellow or fake gold ink. In order to increase the metallic luster, an appropriate amount of about 10% gold ink is added. The silver printing base is generally made of fake silver. Its formula can be diluted with dilute agent, white ink, black ink, de-sticking agent, No. 6 varnish, and white dry oil. Silver ink printing is better than gold ink, a print can basically meet the needs of printed matter, if you encounter a large area of ​​silver printing products or poor paper quality, you need to use two prints to show a silvery luster.

The printing of gold (silver) ink on the undertone ink can achieve the purpose of saving gold (silver) ink, increase the gloss of the gold (silver) ink layer, and enhance the process effect of gold (silver) ink. Since the printing quality of the under color ink is a prerequisite for improving the printing quality of the gold (silver) ink, the printing surface of the under 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 dryness of the base color ink should be selected as the combination of permeability and conjunctiva, and it is better not to crystallize the base color ink layer. In addition, in addition to the above-mentioned selection of inks that are similar to the color of gold (silver) inks, the undertone inks used in printing can be selected from black ink, blue ink, dark red ink, magenta ink, and dark green ink. Color ink easy to bring out the bright and three-dimensional sense of gold ink. Note: The background color should not be too thick, thin is better. Similarly, silver ink can also be used silver-gray ink, if you use a transparent yellow background color, silver ink can be stacked to achieve a golden glossy printing effect. Imprinted gold (silver) inks should be overprinted when the underlying ink is not completely dry. Otherwise, inks that are not printed on gold (silver) or gold (silver) may fall off.

If the printing material of gold (silver) ink is paper, the choice of paper is also crucial, and the paper performance must be compatible with the process characteristics of gold (silver) ink printing. Offset paper and letterpress paper have strong ink absorption. After printing, they can not express the metallic luster of gold (silver) ink. Paper with good paper quality, coated paperboard, glass paperboard, and whiteboard paper (slightly) are suitable for gold printing. (Silver) ink, after the printed metal luster easier to present, and give people the artistic beauty. In order to prevent the gold (silver) ink product from coming off in contact with air or other chemical substances, it is necessary to overprint the varnish once again after printing the gold (silver) ink or coat the surface of the printed product.

The room temperature should also be mastered during operation. Generally, the indoor temperature is maintained at 22~25°C. The temperature is too high or too low to be detrimental to printing. If the temperature is too low, the flow of gold (silver) ink will be reduced, and the temperature will be too high. ) The transferability of the ink will deteriorate. When the room temperature exceeds 38°C, the screen clogging will affect the transmission of ink. The appropriate amount of dibutyl ester can be added to the gold (silver) ink. When operating, be careful not to blow the plate directly.

Fifth, troubleshooting In the printing process of gold (silver) ink, there are often such problems, in order to obtain the desired print quality, some variables must be adjusted.

1. Blocking the net

When scratching, avoid empty scratches without prints and long downtime. When the weather is hot, the printing material often jams the printing plate mesh so that no graphics can be printed. At this time, the printing plate must be scrubbed. Can be used to remove the positive and negative sides of the screen plate by using a degreasing cotton wool or a soft cloth and a solvent. When the scrubbing is performed, the graphic and text areas should be wiped first, and then the other parts should be scrubbed. The positive and negative sides must be scrubbed cleanly, so that the plugging mesh can be dredged and the screen plate can be dried. On the solvent. At the same time in the printed material appropriate addition of dibutyl ester like slow-drying agent, but dibutyl ester and the like sticky, so the scraped printed products should not be too thick to store, in order to prevent the printing product adhesion phenomenon.

2. The layout is sticky

The typography of the screen is due to the small mesh distance and insufficient elasticity. Should increase the net distance appropriately, general network distance is 3~5mm is appropriate.

3. Screen printing ink

The main reason for ink leakage in the layout is that some areas are not sealed when the net is closed, and the screen should be sealed after the ink is sealed.

4. Plates dirty, blotting paste

The dirty printed surface of the printing plate and the printed paste are too thin for the formulated printing material, and the printing material leaks to the bottom layer when the printing is scratched. The thickening of the printing material can be appropriately thickened, and the amount of printing material can also be appropriately controlled with a squeegee.

The factors affecting product quality are many, as long as we continue to explore and sum up experience in all aspects, earnestly understand and master the printing performance of gold (silver) ink and connecting materials, and correctly deploy and strictly process operations, we can obtain satisfactory printing. effect.

Reprinted from: Screen Printing