Thermal transfer technology is a common process in the surface treatment of cosmetic packaging materials. It is a process that is preferred by brands because of its convenience in printing and the customizable colors and patterns. However, thermal transfer technology also often encounters related quality problems. In this article, we list some common quality problems and solutions.
Thermal transfer technology refers to a printing method that uses transfer paper coated with pigments or dyes as a medium to transfer the pattern of the ink layer on the medium to the substrate through heating, pressurization, etc. The basic principle of thermal transfer is to directly contact the medium coated with ink with the substrate. Through the heating and pressurization of the thermal printing head and the impression roller, the ink on the medium will melt and transfer to the substrate to obtain the desired printed product.
1、Full-page flower platePhenomenon: spots and patterns appear on the full page.
Reason: The viscosity of the ink is too low, the angle of the scraper is improper, the drying temperature of the ink is insufficient, static electricity, etc.
Troubleshooting: Increase the viscosity, adjust the angle of the scraper, increase the oven temperature, and pre-coat the back of the film with static agent.
2. Pulling
Phenomenon: Comet-like lines will appear on one side of the pattern, often appearing on the white ink and the edge of the pattern.
Reason: The ink pigment particles are large, the ink is not clean, the viscosity is high, static electricity, etc.
Troubleshooting: Filter the ink and remove the scraper to reduce the concentration; the white ink can be pre-sharpened, the film can be treated with static electricity, and the scraper and plate can be scraped with a sharpened chopstick, or an static agent can be added.
3. Poor color registration and exposed bottom
Phenomenon: When several colors are superimposed, the color group deviation occurs, especially on the background color.
Main reasons: The machine itself has poor precision and fluctuations; poor plate making; improper expansion and contraction of the background color.
Troubleshooting: Use strobe lights to manually register; re-plate making; expand and contract under the influence of the visual effect of the pattern or do not whiten a small part of the pattern.
4. The ink is not scraped clearly
Phenomenon: The printed film appears foggy.
Reason: The scraper fixing frame is loose; the plate surface is not clean.
Troubleshooting: Readjust the scraper and fix the blade holder; clean the printing plate, and use detergent powder if necessary; install reverse air supply between the plate and the scraper.
5. Color flakes
Phenomenon: Color flakes off in local parts of relatively large patterns, especially on pre-treated films of printed glass and stainless steel.
Reason: The color layer is more likely to flake off when printed on the treated film; static electricity; the color ink layer is thick and not dried sufficiently.
Troubleshooting: Increase the oven temperature and reduce the speed.
6. Poor transfer fastness
Phenomenon: The color layer transferred to the substrate is easily pulled off by the test tape.
Reason: Improper separation or back glue, mainly manifested by the back glue not matching the substrate.
Troubleshooting: Replace the separation glue (adjust if necessary); replace the back glue that matches the substrate.
7. Anti-sticking
Phenomenon: The ink layer flakes off during rewinding, and the sound is loud.
Cause: Too much winding tension, incomplete drying of ink, too thick label during inspection, poor indoor temperature and humidity, static electricity, too fast printing speed, etc.
Troubleshooting: Reduce winding tension, or appropriately reduce printing speed, make drying complete, control indoor temperature and humidity, and pre-apply static agent.
8. Dropping dots
Phenomenon: Irregular leaking dots appear on the shallow net (similar to dots that cannot be printed).
Cause: The ink cannot be put on.
Troubleshooting: Clean the layout, use electrostatic ink suction roller, deepen the dots, adjust the scraper pressure, and appropriately reduce the ink viscosity without affecting other conditions.
9. Orange peel-like ripples appear when gold, silver, and pearlescent are printed
Phenomenon: Gold, silver, and pearlescent usually have orange peel-like ripples on a large area.
Cause: The particles of gold, silver, and pearlescent are large and cannot be evenly dispersed in the ink tray, resulting in uneven density.
Troubleshooting: Before printing, mix the ink evenly, pump the ink onto the ink tray, and place a plastic air blower on the ink tray; reduce the printing speed.
10. Poor reproducibility of printed layers
Phenomenon: Patterns with too large a transition in layers (such as 15%-100%) often fail to print in the light-tone part, have insufficient density in the dark tone part, or at the junction of the middle tone part with obvious light and dark.
Cause: The transition range of the dots is too large, and the ink has poor adhesion to the film.
Troubleshooting: Use an electrostatic ink-absorbing roller; divide into two plates.
11. Light gloss on printed products
Phenomenon: The color of the printed product is lighter than the sample, especially when printing silver.
Cause: The viscosity of the ink is too low.
Troubleshooting: Add original ink to increase the viscosity of the ink to an appropriate amount.
12. The edges of white characters are jagged
Phenomenon: Jagged edges often appear on the edges of characters with high whiteness requirements.
Cause: The granularity and pigment of the ink are not fine enough; the viscosity of the ink is low, etc.
Elimination: sharpening the knife or adding additives; adjusting the angle of the scraper; increasing the viscosity of the ink; changing the electric engraving plate to a laser plate.
13. Uneven coating of the pre-coated film of stainless steel (silicon coating)
Before printing the transfer film of stainless steel, the film is usually pre-treated (silicon coating) to solve the problem of incomplete peeling of the ink layer during the transfer process (when the temperature is above 145°C, it is difficult to peel the ink layer on the film).
Phenomenon: There are lines and filaments on the film.
Cause: Insufficient temperature (inadequate decomposition of silicon), improper solvent ratio.
Elimination: Increase the oven temperature to a fixed height.
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Company Name: Shanghai Rainbow Industrial Co., Ltd.
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Country: China
Website: https://www.rainbow-pkg.com/
