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Mirror Silver Inks
Application and selection of mirror silver ink in IMD technology With the continuous development of IMD (Formable surface decoration) technology, The application of mirror ink in IMD has made IMD technology a step forward, increased the beauty of IMD workpieces, and improved the grade of products. The so-called "mirror ink", it is a metal color screen printing ink, a solvent volatile type, is made of plastic resin mixed with special metal powder cloth, used to print on the back of transparent plastic sheet (polyester sheet, PC sheet, PVC sheet, PMMA, etc.), to get the metal color mirror printing effect, just like the general mirror or the effect of hot stamping surface.
Mirror Silver Inks Printing Process
First, the printing step is completed in two stages, that is, the mirror ink is printed on the back of the sheet, thoroughly dried, and then IMD special ink is printed on the mirror ink, thoroughly dried, and the printing process is completed. The specific printing process of these two stages is as follows:
1. Printing of mirror silver ink
(1) Printing process parameters:
Screen: Select 270-300 mesh/inch polyester screen
plate: solven-resistant screen
scraper hardness: 80°-85°
Dilution: with T-1000 solvent dilution (in the printing process viscosity becomes high can be added)
Drying: Heating and drying at 80 ° C, 10-15 minutes or 60 ° C, 15-20 minutes, drying at room temperature takes about 20-30 minutes, but the mirror effect of natural drying is not as good as heating and drying.
Net washing: T-15 or T-31 solvent
2) Mirror Silver Ink Printing technology skills:
a. Due to the different proportion of metal toner, plastic resin and additives, the components of the ink will be layered when stored, so it must be thoroughly stirred before use.
b. Due to the low viscosity of the ink, pay attention to the selection of a higher mesh screen when printing, and the selection of a higher hardness of the scraper, usually with 80°, printing to appropriately reduce the printing pressure of the scraper.
c. In order to prevent the phenomenon of network blockage, be careful not to print in the place of air circulation.
d. The net distance should be smaller, and the tension of the screen should be slightly lower.
e. This ink is more difficult to print than ordinary ink, it is best to choose an experienced technician to print.
f. In order to prevent the ink from absorbing water and making the mirror gloss low, avoid moisture when printing and storage, and dry at low temperature immediately after printing.
2. After the printing mirror ink of IMD ink is thoroughly dried, a layer of IMD special ink (solvent-based or photocuring) is evenly coated on the top of the mirror ink. Generally use light oil or white ink to protect the mirror ink and prevent the washing of the mirror ink by high temperature injection molding fluid, because the mirror ink is not resistant to high temperature. This layer should have a certain thickness, if the printing is too thin, can not evenly cover the mirror ink, you can print twice. (The position of the injection gate is best to print twice or print a layer of temperature-resistant ink, in addition, the correct design of the position and direction of the injection mold pouring gate is also a very important factor, because the injection liquid at the position of the gate has the highest temperature and pressure, and the impact is large, and the ink is easy to be washed away.) This layer of IMD special inks can be used either solvent-based such as, and the process parameters are as follows:
(1) printing process parameters:
screen: 90-120 mesh/cm polyester screen plate: solvent-resistant screen
thinner.
according to the change in temperature and humidity of the screen printing environment, all solvents can be mixed at different ratios to achieve the ideal drying speed.
It is the most widely used, when printing fine lines, the use of slow drying agent will extend the drying time of the screen.
Drying: After drying in a tunnel dryer with good ventilation at 60-80°C, and then thoroughly drying at 90°C in the IR oven for 1-5 hours, the length of drying time is subject to the evaporation of all the residual solvents, and sometimes the drying time is too long, which will also cause the ink film brittle increase leading to cracking or flying oil and other ills.
Imprint (Water-based binder) HF-093 and dry at 80°C for 5 minutes.
(2) IMD special UV ink process parameters:
mesh: 120-180 mesh/cmpw polyester wire mesh
plate: tension is about 20N/CM solvent-based screen
additives: 073 solid promoting agent, 100 thickening agent, 060 dot varnish
drying: Two 120 W/cmUV curing medium pressure mercury lamps, curing speed of 20 meters/about
printing: AutotypeSC(water-based adhesive), drying at 80℃ for 5 minutes.
2. Forming and forming method
（1）Since the binding force between PC sheet + mirror ink + injection plastic is less than the binding force between PC sheet + injection plastic, the mirror ink can not be fully printed, that is, it can not be printed to the edge, and the edge margin of PC sheet must be left, so that PC sheet and plastic can be firmly combined together and the PC sheet and injection plastic at the edge of the IMD workpiece is very strong. When it will not be torn under the action of external forces, the bonding fastness of the mirror ink inside with the PC sheet and the injection plastic will not be affected by edge tearing. In order to ensure that the mirror ink molding does not crack, the PC and it are not layered (separated) during injection molding, in addition to the structural design of the image and text should be reasonable, when printing mirror ink, the design of the molding mold is also very important to leave a PC sheet margin outside the effective mirror ink area. For example, if the IMD workpiece of the following figure is made, the usual process is: like the top foot edge of the mirror ink, the following situation will occur: when the edge is bent, the concave and convex is strong or the force is torn, the edge will crack, and the entire mirror ink layer will be separated. If the molding mold is improved, the PC workpiece after prepressing has a printing mirror ink edge of 0.5mm, and the 0.5mmPC sheet after injection is just integrated with the injection plastic, so that the edge of the sheet can be avoided after injection and the mirror ink is separated, which greatly improves the finished product rate, and the edge of the injection workpiece is smoother and the finished product is more beautiful. As shown below:
（2）If the structure of the molding die is unchanged, the molding method in the normal IMD process is followed.
（3）The shearing process is carried out in accordance with the normal IMD process.
（4）Injection molding For two different molding methods, the injection molding process has two measures.
① If the molding is according to the first molding method above, the structure of the injection mold should be improved with the structure of the molding mold, so that the injection mold and the molding mold are matched, and the others are the normal injection molding process in the IMD process.
② If the molding die and injection mold are unchanged, they are produced according to the normal IMD process, and the edge of the mirror ink is ultrasonic welding or thermal welding after injection, so that the binding strength of the workpiece edge is guaranteed.
The application of mirror ink in IMD technology has improved the application status of IMD products. This paper hopes to play a reference role for IMD manufacturers in the process of IMD manufacturing.