Digital Laser Transfer Printing (LTP)
Digital Laser Transfer Printing (LTP)
Digital Laser Transfer Printing for ceramic colours
An innovative digital printing technology
Learn more about this unique technology...
The LTP process
In the LTP process, an endless web is used as a carrier for the ink. The laser beam transfers a defined amount of the ink to a flat substrate. The ink carrier web is transparent for the laser wavelength used. The laser beam is focussed onto the ink and evaporates some portion of the ink solvent. As a consequence a vapour bubble expands and pushes an ink droplet towards the substrate. The ink droplet is released and deposited on the substrate.
The laser focus is scanned in form of a line across the carrier web. The continuous motion between the printing line and the substrate creates a two dimensional print - line by line. Switching the laser on and off during the scan then creates an image.
The laser energy applied determines the amount of ink being transferred and enables to control the ink layer thickness on the substrate.
From screen printing to LTP
Historically car glass is being bonded to auto body since the 80s. The purpose of printing black colour around the edges is the protection of the glue against the UV radiation. Furthermore, the edge printing is simply supposed to look nice to the outside. Nowadays lorry, bus and train glass is also bonded and printed upon.
Up to today screen printing has been the established method to apply the colour to the glass substrate. Screen printing provides high printing speed independent of the glass size. Hence, it is unbeatable in terms of cycle time on large areas.
However, there are limitations to screen printing. Image resolution is also limited and the layer thickness is fixed with the screen thickness. One screen per window model is required, thus glass-to-glass data variation is impossible. Screen handling from procurement to storage is extensive and costly, in particular with regard to rigging, dismounting, cleaning and storage. This results in high fixed costs making screen printing uneconomical for small runs.
As a result LTP is ideal for producing smaller runs which applies to aftermarket replacement and transportation glass (trains, ships lorries and busses). In addition, where only small areas need to printed, e.g. for logo printing, LTP is a digital method. Above all, as the enamel in screen and LTP printing is the same LTP does not have to be requalified. Serveral inks have already successfully passed the relevant automotive tests.
Benefits for transportation glass printing
Printing of all features
- black edge and cover print
- serialized logo print
- silver for antennas, defrosters and solder pads
Ideally for ARG and transportation glass applications
Serialization and individualization
- QR or datamatrix codes, serial numbers
- QR codes down to 4 mm × 4 mm
- Excellent Quality
Enables traceability for OEM car and transportation glass
Printing of narrow lines
- fine line resolution for silver prints (stable Linienbreite 150 µm line width)
- print-on-print to selectively increase thickness
- accurate silver on black print to hide antenna
Enables traceability for OEM car glass manufacturing
Laser power dependent ink amount transfer for
- grey-scaling of areas
- resistance adjustment without ink modification
defroster grid printing on backlites or windscreens
Laser Transfer Printing - Transfer your ideas to glass
LPKF Callisto for aftermarket and transportation glass
The heart of LTP printers
At the heart of each LPKF LTP printer a high performance print head does its job. This mainly consists of an inking unit, the high-speed line scanner as well as the laser unit. In the inking unit, an endless rotating web is continuously and homogeneously coated with the ink for printing. Inside this, the laser beam focus is moved at extremely high speed over the web to perform the transfer operation. The laser unit comprises the laser source as well as the beam modulation and beam guiding and forming system.
The printing head can be scaled in its performance according to the application. Small area prints like logo printing can usually be achieved at lower speed demanding for less laser power and component performance. Large area prints require our 250 mm/s print speed head with a theoretical area coverage of 90 m²/h. Furthermore, our print head line can be equipped with different interface packages to allow for different integration scenarios. This includes integration into existing printing lines or machines as well as our LPKF Callisto large are printer.
The LPKF Callisto printer for transportation glass applications
The LPKF Callisto, the first printer in our Jupiter product line, has been developed for printing on transportation glass. Conventional cars (aftermarket replacement glass) as well as busses, trains, airplanes, and ships are included in this segment.
The Callisto's design draws on LPKF’s experience in fast, high-precision processing of glass-based thin film solar modules. It is equipped with fast linear axes based on a gantry design. The axis system can hold one print head. The glass referencing respectively focalization system is camera based and thus flexible, no adjustments of the known mechanical focalization is required prior to production. By simply changing the print data the glass model is changed. No extensive and costly rigging of new screens is required. No screens have to cleaned, re-ordered or stored anymore. The Callisto is designed as a stand-alone printer that can be configured as a terminal or inline system.
The basic Callisto comprises a 2 x 3 m glass size printing area with our 250 mm/s print head. The head is equipped with a sensor system to allow for an edge-to-edge printing. Printing is bidirectional and the print head is height controlled relative to the glass during printing. The ink temperature is controlled and kept constant. The Callisto has an automatic ink handling for one ink/colour. Options are a cabin with air conditioning to ensure optimized process conditions, an active solvent extraction and filter unit, the extension of the external ink supply to one more ink and more.
Also as an option the entrance conveyor can be ordered from LPKF. This allows to easily load and unload a glass substrate onto or from the conveyor.