UV ink is an ink that cures instantaneously by ultraviolet irradiation and forms a good ink film. When using UV inks, you usually need to pay attention to the following points:
1. Indoor temperature adjustment
The viscosity of a UV type ink has the property of drastically changing with the change in temperature, and this change in viscosity has a great influence on the printability and the print film thickness. In general, when the ink temperature decreases, the viscosity increases and the film thickness increases. The viscosity of the ink becomes too high, the permeability of the screen is weakened, and printing quality problems such as foaming and blowholes occur after printing. Therefore, try to keep the room temperature constant during printing. Generally 18 ~ 25 °C is appropriate. Partial UV screen printing ink. When the humidity at the printing site is high, moisture is absorbed, causing problems such as thickening and gelation. At this time, an air conditioner or dehumidifier can be used to solve this problem.
2. Screen
When using general color inks, use a screen with a screen size of 300 mesh or more and a thickness of 10.1xm or less. In this condition, the thickness of the ink printed is 10~121xm. If the printing area is up to 70~90m/kgc for printing five-color varnish, thick-film effect can be printed by using a low-mesh screen, and the screen can be selected according to the purpose.
3. scraper
Please use a polyurethane blade with a hardness of 65~80 and the edges are sharpened. The monomer contained in the ink causes the blade to swell, and it is necessary to carry out the necessary treatment such as grinding or reversal of the blade.
4. Viscosity adjustment
After being fully stirred, the ink can be directly printed out after being taken out from the ink tank. According to the use, if it is necessary to reduce the viscosity of the ink, add the diluent within 10%. Conversely, if it is necessary to increase the viscosity before printing, please mix with a matt varnish (high viscosity) or add a powder matting agent, and print it after mixing.
5. Concentration adjustment
When adjusting the concentration, add a clear varnish or a colorless concentration adjuster.
6. The effect of light
During the printing process or the screen printing process, avoid direct sunlight on the screen printing ink. The fluorescent light, as long as it is not very close, is generally no problem.
7. Standard curing conditions
Each UV series ink has its own standard curing conditions. Please refer to the standard curing conditions described in each series of ink product manual for correct operation.
8. Preliminary test
The curing conditions in the official printing vary depending on the printing materials and printing conditions. UV irradiation machine manufacturers and different types of machines, will also cause differences in curing. Therefore, pre-testing must be performed under the same conditions as the printing line to determine the curing conditions.
The procedure for preparing for the test is as follows:
1 After printing the ink on the printed material, pass the UV irradiator under standard conditions.
2 Then test the remaining traces, adhesion, scratching, and flexural properties of the printed surface.
3 If the test result is not satisfactory, it is necessary to adjust the conditions of the irradiation until satisfactory results are obtained.
4 During the test, it is recommended to use a UV light meter for measuring the amount of light.
9. Printing warm up
When the ink is printed after printing on a substrate that does not easily adhere, preheating is performed before UV irradiation. Preheating with near-infrared rays, far-infrared rays, etc. for 15 to 90 seconds will greatly improve the adhesion.
Reprinted from: China and Hong Kong silk screen network
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