Mirror ink application and selection in IMD technology

With the continuous development of IMD (formable surface decoration) technology, the application of mirror inks to IMD has made IMD technology a step forward, increasing the aesthetics of IMD parts and improving the quality of the products.

The so-called "mirror ink", which is a metal-colored silk screen printing ink, is a solvent-evaporation type, and is made of a plastic resin mixed with a special metal toner for printing on transparent plastic sheets (polyester sheet, PC sheet, PVC sheet, PMMA On the back side, a metallic mirror printing effect is obtained as if it were an ordinary mirror or bronzing surface.

There are three types of Seiko mirror inks that can be selected based on the material and application of the prints:

Mirror silver ink B: only suitable for printing on polyester film (PET), with excellent mirror effect and strong adhesion to PET.

Mirror silver ink NO2: Printable polyester sheet (PET), PC, PVC, PMMA.

Mirror silver ink NO3: used for mirror printing of other colors. Can be used for PET, PC, PVC, PMMA, with gold, red gold, green gold and other colors.

The following is a brief description of the application and process flow of mirror ink in IMD technology.

First, printing

The printing step is completed in two stages. First, a mirror ink is printed on the back of the sheet, and after drying thoroughly, an IMD-specific ink is printed on the mirror ink, and the ink is thoroughly dried to complete the printing process. The specific printing process for these two phases is as follows:

1. Mirror ink printing

(1) Printing process parameters:

Mesh: Use 270-300 mesh/inch polyester mesh

Screen: Solvent-resistant screen

Scraper hardness: 80°-85°

Dilution: Dilution with T-1000 solvent (add it only when the viscosity becomes high during printing)

Drying: Heat drying at 80° C., 10-15 minutes or 60° C., 15-20 minutes, drying at room temperature takes about 20-30 minutes, but the natural dry mirror effect is not as good as heating and drying.

Wash Net: T-15 or T-31 Solvent

(2) Printing process skills:

a. Due to the different proportions of metallic toner, plastic resin and additives and additives, the components in the ink will be layered when stored, so be sure to mix thoroughly before use.

b. Due to the low viscosity of the ink, a screen with a higher screen mesh should be selected for printing, and a doctor blade with a higher hardness is used, usually 80°, and the printing pressure of the doctor blade is appropriately reduced during printing.

c. In order to prevent blocking of the net, be careful not to print in places where the air circulates.

d. The network distance should be smaller and the screen tension should be slightly lower.

e. This ink is harder to print than ordinary ink. It is best to choose an experienced mechanic to print.

f. In order to prevent the ink from absorbing the moisture, the mirror glossiness is low, and the moisture should be avoided during printing and storage, and it should be dried at low temperature immediately after printing.

2. IMD ink printing

After the mirror ink is completely dried, an IMD-specific ink (solvent type or photo-curable type) is evenly applied on the mirror ink. The general use of lacquer or white ink to protect the mirror ink prevents high-temperature injections from flushing the mirror ink because the mirror ink is not resistant to high temperatures. This layer should have a certain thickness. If it is too thin to be printed, it can't evenly cover the mirror ink and it can be printed twice. (The location of the injection gate is best to print two times or to print a layer of temperature-resistant ink. In addition, the correct design of the position and direction of the injection port of the injection mold is also an important factor because of the injection molding liquid at the gate location. The highest temperature and pressure, large impact, the ink can be easily washed away.) This layer of IMD special ink can be used solvent type such as Baolong Noriphan HTR, can also be used UV ink such as the promise of IMD special UV ink, the process parameters are as follows:

(1) Noriphan HTR printing process parameters:

Wire mesh: polyester mesh 90-120 mesh/cm

Screen: Solvent-resistant screen

Thinner: Noriphan HTR 090 Thinner, Noriphan HTR 097 Slow Dryer, Noriphan HTR 097/003 Slow Dryer

Diluent is selected based on the temperature and humidity of the screen printing environment. All solvents can be mixed at different ratios to achieve the desired drying speed.

Noriphan HTR 097 is the most widely used and can use slow drying agent Noriphan HTR 097/003 to extend screen drying time when printing fine lines.

Drying: After drying in a well-ventilated tunnel dryer at 60-80°C, then dry it in an IR oven at 90°C for 1-5 hours. The drying time is based on the total amount of residual solvent evaporated. Sometimes the drying time is too long. Long, it will also cause the ink film brittleness to increase and lead to cracking or flying oil and other ills.

The Aquapress (aqueous adhesive) HF-093 was stamped and dried at 80°C for 5 minutes.

(2) Noguchi IMD special UV ink process parameters:

Wire mesh: 120-180 mesh/cm pw polyester mesh

Screen: solvent-resistant screens with a tension of about 20N/CM

Auxiliaries: 073 Accelerator, 100 Thickener, 060 Dot Varnish


Drying: Two 120 watts/cm UV curing medium pressure mercury lamps with a curing speed of 20 meters/or so

Binding: Autotype SC (water based adhesive), dried at 80°C for 5 minutes.

Second, molding and molding methods

1. Because the binding force between the PC sheet + mirror ink + injection molding plastic is less than the binding force of the PC sheet + injection molding plastic, the mirror printing ink cannot be full printed, ie it cannot be printed on the edge, and must be left The margin of the PC sheet is such that the PC sheet and the plastic can be firmly bonded together, and the PC sheet and the injection molding plastic at the edge of the IMD workpiece are firmly bonded, and when the external force does not tear, the mirror ink inside is The bond fastness to PC sheet and injection molding plastic is not affected by edge tear. In order to ensure that the mirror ink is not cracked during molding, the PC is not layered (separated) during injection molding. In addition to the graphic design of the graphic, the graphic design should be reasonable. When the mirror ink is printed, the effective mirror ink area is left with the PC sheet remaining outside the forming die. Design is also very important. For example, if you make an IMD workpiece as shown below, the usual procedure is:

The top edge of the mirror ink, such as this, will appear the following situation: When the edge of the curved, concave and convex or tearing force will appear cracking edge, leaving the entire mirror ink layer is separated. If the molding die is improved, the pre-pressed PC workpiece will grow 0.5 mm long on the edge of the ink on the mirror. The grown 0.5 mm PC sheet will be integrated with the injection-molded plastic just after injection, so that the edge and the mirror surface of the sheet can be avoided after injection. Separation of ink greatly improves the yield, and the edge of the injection molded part is smoother and the finished product is more beautiful. As shown below:

2. The structure of the molding die is unchanged, and the molding method in the normal IMD process is followed.

Third, cut

The shearing process is performed in a normal IMD process.

Fourth, injection molding

There are two measures for the injection molding process for two different molding methods.

1. If the molding is performed according to the above first molding method, the injection molding structure should be modified with the molding mold structure so that the injection molding mold is matched with the molding mold, and the others are all normal injection molding processes in the IMD process.

2. If the molding die and injection mold are not changed, they are produced according to the normal IMD process. After the injection molding, the edge of the mirror ink is subjected to ultrasonic welding or heat welding, so that the bonding strength of the edge of the workpiece is ensured.

The application of mirror ink in IMD technology has further enhanced the application status of IMD products. This article hopes to play a reference role for IMD manufacturers in the process of manufacturing IMD

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