In general there is no simple way in getting graphics onto the topsheet. The explanation I have gotten from professional printing companies is, that the topsheet and base plastics are very tough and durable industrial plastics made for application of durability, hence also from the chemical viewpoint they will be tough and resistant against reacting with any ink.
There are several ways people have tried toget the graphics onto the topheet,
– Digital printing with solvent ink, UV curable ink, Epoxy inks etc.
– Sublimation or heat transfer
– Silk screen printing.
– Printing on a substrate or a cloth which is an inlay to the topsheet (goes under the topsheet).
For topsheets available, here are the options,
PBT: This one is white, and is sutiable for sublimation only. It gives fantastic results.
PA: PA is suitable for sublimation as well. You should be able to screen print on it as well. For white background you have to back print on it.
TPU/ABS: The ABS component in this topsheet reacts chemically with solvant ink. Typically white is not printable, so it becomes see thru, unless you can find someone who can print white. So this one you can print with solvant ink. Also screen printing should be ok.
In general Iv tried UV printing. It will not stick to the topsheet! If you can somehow print with epoxy ink on the topsheet, this will work but so far I have not found anyone who can do this.
Isosport has not been succesfull in digitally printing on any topshets, the latest update is that soome of the topshets suchas ICP 8210 PA might be printed on with a Latex printr (which is quite expensive), however no waranty.
The main problem is that if you print digitally the ink might stick to the topsheet and seem to be ok, however the bound between ink and the topsheet is so weak, that after the process of lamination, the ink will seperate from the topsheet and your topsheet will fall off.
Any topsheet with ABS component in it will react well with solvent ink. As far as I know, this is how signs are made. One drawback to pure ABS is that it is UV sensitive, it might give yellowing if the topsheet is not threated with some kind of varnish.
So in general unless you have a Latex printer you can test, or unless you use a ABS topsheet, digital printing is hard to accomplish.
The results from a digital printing on a transparent topsheet are transparent graphics, so if you dont for your internal layup to be visible you will have to backprint with some white pigmented epoxy or similar. Nadzar has epoxy inks used for this, from personal experience the pigment to epoxy ratio has to be high.
Usually white might be hard to get.
Printing on an inlay should be doable. The main properties of the inlay should be that it will bind to epoxy on both sides and that it will receive ink well. It should also be strong in a way that you can not rip it appart when you pull on the two sides (topsheet will pull one way and the glassfabric on the other side will pull another way). Also you need to think about that your inlay will not absorb moisture and delaminalte later on.
Printing on cotton or bamboo or similar cloth material (say 100gms) can be done by some companies, or you can try to set it up on your printer. Thin cloth inlays are successfully used in surfboards, however quite often they also give a see thru result.
Another method I hear about is printing on paper. I have had bad results with delamination this way. Make sure you experiment before you go with this method.
Sublimation should be possible on PBT-polyester inlay fabric.
Tissue paper or rice paper are also widely used but are hard to deal with. Tissue paper is a cheap and simple way for a small builder. You need some acidic free tissue paper, a spray adhesive and some printer paper. You spray the adhesive to your printer paper, attach the tissue paper and cut it quickly to shape, put it in the printer, print. Once it is printed you need to be quick to remove the tissue paper from the printer paper. It is now ready!
As long as the fabric/inlay has some small holes where the epoxy can penetrate, this should improve the bound to the topsheet and minimize delamination.
The thickness of the inlay and density will determine the see thru and the white in the graphics.
Silk screen printing
Silk screen printing on a topsheet is not my favorite (unless you can find waterbased epoxy inks or similar). In this method you create a screen for each color and the you put your screen over the topsheet and press the color thru the screen. Once this color dries, you go to the next screen for the next color, and in the end you have a topsheet impregnated with all the graphics.
It is mainly for larger production, the initial setup cost is high and you have little degree of freedom in making custom graphics. You also need some strong epoxy chemicals which are both hasardeous to you and the environment.
White color is doable.
Sublimation printing or heat transfer is the method where the ink is transfered onto the tophseet in a pressurized heated press. The molecules of ink go deeply into the topsheet and are hard to get out or scratch off. I prefer this method for several reasons. Beyond the not so bad setup investment, the method works on several topsheets such as PA and PBT and some ptex. The ink is water based and hence environmentally and health friendly. The waste is minimum. It is suitable for custom graphics.
White colors are not doable, so any graphics with white component is done on a white topsheet – PBT.