Bottles Screen Printing

What affects UV ink adhesion in bottle screen printing process?

Silk screen printing is one of the most commonly used graphics and text printing processes in cosmetic packaging materials. It has simple equipment, easy operation, simple printing and plate making, low cost, and strong adaptability. However, if the adhesion is poor, does not have a certain fastness, is not resistant to friction, and is not resistant to impact, it is equivalent to no printing. This article will explain the factors that affect adhesion when screen printing.

1, The Substrate of Bottles

If the printing material is impure, it will have a considerable impact on the adhesion. In the current market, impure printing materials are mainly manifested in synthetic materials and nozzle materials. During injection molding, the process differences of different companies lead to different conditions on the plastic surface. There are many materials with grease on the surface, which will affect its adhesion. The color of the bottle material also affects UV absorption and therefore its adhesion.

2, Pre-treatment before Printing

In order to obtain good adhesion of the ink to the substrate, the bottle must be pre-treated so that the surface tension of the bottle is not less than 3.8×10-2mN/m (generally speaking, the most basic condition for the ink to have good adhesion to the substrate The surface tension of the substrate must reach at least 50mN/m).

3, UV dryer

UV lamp curing

The UV ink should be cured under a 280-320nm UV lamp immediately after printing. The curing speed depends on the thickness of the ink layer and the power of the lamp. The conveyor belt speed is neither too fast nor too slow.

UV curing lamp

The curing lamp must ensure that the wavelength, power, and energy meet the curing requirements of UV ink. All three are indispensable. Otherwise, it will cause non-curing, incomplete curing or embrittlement of the ink layer, further affecting the adhesion and softness of the ink.

Different ink colors require different energy during curing

Generally speaking, during the curing process of UV bottle ink, black, white, yellow, and red inks require higher energy. Therefore, the conveyor belt speed of the UV curing equipment should be appropriately reduced during curing to increase the curing time of the ink. In addition, the curing time of specially formulated inks mixed with different colors must be tested and confirmed.

4, Screen Printing Material and Technical process

Mesh

For bottle screen printing, a polyester or nylon screen with a mesh size of 140 to 165 mesh/cm is generally selected to ensure the covering power of the ink layer and complete curing of the UV ink during printing.

Squeegee

The hardness of the squeegee is generally between 75 and 85 degrees. A 5×25 flat squeegee or a pointed squeegee can be used. The squeegee must be wear-resistant and solvent-resistant. The choice of squeegee hardness and angle has a great impact on the fineness and ink volume of screen printing. For fine pattern printing, it is generally required to choose a squeegee with higher hardness. As for the angle of the squeegee, the theoretical optimal angle is 45°. At this time, the edge of the squeegee contacts the screen in a straight line. Considering the pressure during printing, the angle of the squeegee should be greater than 45°. If the hardness of the squeegee is too small and the angle is improperly selected, it will increase the amount of ink deposited, affect the degree of solidification of the ink, and thus affect the adhesion of the ink.

Techniques

The screen printing ink layer should not be too thick. If it is too thick, the UV penetration will be weak and the light will not be completely cured. Naturally, the adhesion will be affected.

5, UV Printer Ink

Before using ink

The most basic principle of UV ink screen printing is that the ink must be fully stirred before use. This is because the proportions of resins, solvents, pigments, and additives in the ink are different, and delamination will inevitably occur after the ink is left for a period of time. If the ink is not stirred sufficiently before use, the components with light specific gravity will be on the upper layer and the components with heavy specific gravity will precipitate. In this way, customers will often react to phenomena such as unstable ink quality and different covering power and adhesion of inks used before and after. Leaving it for 24 hours after printing will deepen the curing effect and various resistances.

UV ink reacts easily when exposed to light

When printing with UV ink, avoid direct sunlight and keep away from fluorescent lamps and mercury lamps.

Ink storage

The storage time of UV ink in a dark room at 22℃-25℃ without opening the can is 1 and a half to 2 years. After opening the can, please tighten the cap and store it at 22℃-25℃. The storage time is half a year. Please Be careful not to let moisture spill into the bottle after the ink is opened.

6, The Condition of Working Room

Printing working room requirements

Because UV screen printing ink is ultraviolet light-setting ink, and sunlight contains ultraviolet rays, it is recommended that the indoor sunlight in the UV ink printing workshop should not be too bright. If the light is too bright, please install curtains to block the light. If there are many fluorescent lamps in the room, please pay attention. The silver powder on the surface of the fluorescent lamp falls off and causes ultraviolet transmission. Too strong indoor light and the ultraviolet transmission of the fluorescent lamp will cause the UV ink to solidify on the screen during the printing process, thus blocking the screen. (In production lines where the sunlight is too bright, please pay special attention to the production line near the window, and please take back the UV ink on the screen in time after printing to avoid curing).

Control the temperature and humidity in the workshop

If the temperature is low and the humidity is high, the photocuring reaction of UV ink will be slow and the binding ability of the ink and substrate will be reduced. Therefore, the ambient temperature and humidity of the workshop must be controlled when printing UV ink. The general temperature is about 18℃~25℃, and the relative humidity is about 50%~65%.

Top China Manufacturer of Screen Ink, Screen Printing ink, Printing ink.

What affects UV ink adhesion in bottle screen printing process?

PET Bottle UV INK screen Printing

Top China Manufacturer of Screen Ink, Screen Printing ink, Printing ink.

What affects UV ink adhesion in bottle screen printing process?

PET Bottle UV INK screen Printing

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