Digital Laser Transfer Print Technology & Process
What is Laser Tranfer Printing?
LTP stands for Laser Transfer Printing.
A laser is used to transfer ink to a substrate. The dimensions of the particles and pigments contained in the ink do not matter because it is coated on an endless ribbon and no nozzles are needed to print the ink.
The laser is focused through the ribbon onto the ink and evaporates defined parts of the ink solvent. This releases an ink droplet which is then deposited onto the substrate.
The rapid movement of the laser in one direction generates a printed line and the continuous motion of the entire printhead relative to the substrate generates a complete printed image.
Any binary image can be printed using this method. Black means laser on and ink droplets will be released. White means laser off and no ink will be deposited onto the flat substrate.
The deposition of the ink is almost independent from the ink, as long as the ink reacts with the laser and as long as the viscosity of the ink is in the range of 300 to 1200 mPas for the LPKF NovaPrint inking system.
Using original and certified screen-printing pastes with large particles and pigments is no problem for LTP. Only the organic medium is adapted to obtain the required viscosity, while the inorganic part of the ink remains unchanged.
After firing, the resulting print on the glass substrate is therefore identical in terms of quality and physical/chemical properties to that obtained through screen printing.
This enables LTP to be used in applications such as automotive glass, where other digital processes are still subject to certain limitations.
Outstanding Characteristics of Laser Transfer Print Technology
LTP enables the digital printing of ceramic particles in original screen-printing size
Almost all pastes and inks can be adapted to the LTP process by changing the paste medium
The viscosity is higher than with inkjet printing and lower than with screen printing
The final product has the same properties as when screen-printed
Printing is contactless with an operating distance of 150 µm
Contactless printing enables wet-on-wet printing (same ink)
The endless ribbon in the system is continously coated with fresh ink. The ink is provided by an external ink supply system. Since it circulates in the system there is no loss of ink.
Owing to the very small working distance of 200 µm, almost no ink splatter occurs
Highly precise and accurate printing with laser
Why Use Laser Transfer Print Technology?
- Original screen-printing pastes can be used. These pastes are only adjusted in viscosity, and after firing, the product has the same properties as screen-printed products. Time-consuming and expensive ink qualification is therefore not necessary.
- The process is ink-independent. Nearly all screen-printing pastes and other inks can be adapted to the LTP process. Extensive tests are carried out in the Application Center and the ink is developed accordingly.
- The level of laser power determines the amount of ink transferred. Thus, the conductivity (silver) and optical density (black) can easily be adjusted.
- The ink thickness on the ribbon also influences the amount of transferred ink and can be changed quickly.
- The contactless process enables wet-on-wet printing, which can also influence optical density and conductivity and result in extremely thick layers.
