Printing Recommendations - Autoflex EB
a) Jet Drying
Jet drying is the most effective drying method, since evaporated solvent is removed by the moving air stream. Temperatures of up to 100°C may be used if necessary, due to the high dimensional stability of Autoflex.
Where multizone dryers are available, the first zone should be set at up to 70°C and later zones up to 90°C to give optimum results. On single zone dryers a temperature of 80°C typically gives good results. With certain inks, commonly those with high gloss finish, skinning of the ink surface may occur at high temperatures preventing further solvent evaporation. If this is identified as a problem the use of slightly lower temperatures for a longer period of time can be beneficial.
The dwell time in the dryer is also of importance. In general the longer the drying time, the better the result. A drying time of about 2 mins per layer typically gives good results.
With some slow drying inks, several extra passes through the dryer may be necessary after completion of a multipass print operation.
The use of thinners and retarders increases the level of solvent which needs removing during drying. In particular, retarders contain slow drying solvents which are difficult to remove, even at elevated temperatures. The level of thinner should be kept as low as possible - consistent with ink manufacturers’ recommendations. We do not recommend the use of retarders.
b) IR Drying
Although capable of generating high temperatures IR dryers tend to suffer from low air flows over the print. This prevents complete solvent removal and creates a greater tendency to cause skinning. In general we do not recommend IR drying.
c) Air Drying
Air drying of inks printed onto Autoflex should be avoided where possible. To give best results the air flow around the drying rack should be maximised and the panels dried for at least 16 hours between each printing operation and at least 24 hours after the final print. Rack drying is very dependant on ambient conditions such as temperature, humidity and air circulation, hence drying will take much longer and be inconsistent. It may not be possible to remove the slower evaporating solvent at all at ambient temperatures, creating the possibility of delamination.
1.2.2 Ink Thickness
It has been found that the thickness of each individual ink layer, and the total thickness of the finished print, both have a great effect on adhesion. The "critical ink thickness" will vary for each ink range, processing conditions and even colours used, but the general principles are:
a) layers should be printed as thin as possible (4 -6μ is ideal). This can be achieved by use of a 120 thread/cm mesh.
b) for a given total thickness, a higher number of thin prints will show better adhesion than a lower number of thicker prints.
c) above a certain total ink thickness (typically 24μ), adhesion will become poor even where the ink normally shows very good adhesion.
It should be noted that the maximum total thickness is an average figure. It will change slightly for different ink ranges and processing conditions. The adhesion of any ink will worsen as thickness increases. The best results will always be obtained if total ink thickness is kept as low as possible.
In all cases, we recommend that optimum printing and drying conditions are established by thorough testing using the processing set-up in question.
1. Correct ink selection
2. Pre-production testing of all inks under production conditions
3. Thorough drying - 2 mins per layer at 800C
4. Keep ink thickness as low as practicable
2. UV LACQUER PRINTING
Where Fototex is to be printed onto the Autoflex EB surface, this must be done as soon as possible after the Autoflex EB is removed from its packaging. If the product is exposed to light and air a slow loss of receptivity occurs. If possible the lacquer should therefore be applied in the first or second printing operation.
Once the Fototex has been correctly printed and cured onto the film the level of adhesion achieved WILL NOT DETERIORATE UNDER NORMAL OPERATING CONDITIONS. See the relevant Processing and Safety Recommendations for details.
Autotype is a major manufacturer of screen stencil and ancillary products which can be used when printing Autoflex EB.
Cleanliness is the key to successful printing. A dust-free environment will enhance the quality of printing. Reduction of static electricity helps to prevent attraction of dust onto the substrate surface. This can be achieved by raising the level of relative humidity in the printing area and by the use of static eliminators.
General contamination, eg grease, dirty cloths, fingerprints etc may cause repellencies or small areas of poor adhesion. Autoflex EB should be kept as clean as possible. Change cleaning cloths regularly, avoid handling the material, and ensure that the work area is free of dirt and grease. Spatulas, squeegees, and other tools must be scrupulously clean – if possible, reserve a set of tools for Fototex use only. Return lid to the pot immediately after pouring out the lacquer. To avoid contamination, never return lacquer to the pot. Always store in the original container.
Sticky roller cleaning systems are very effective for film cleaning, but a small area of contamination on one sheet is likely to be transferred to each subsequent sheet passing under the roller. If used, ensure that tape is changed and rollers cleaned at least daily - more often is advisable.
Occasionally the ink from the reverse of the sheet above in a stack can offset contamination onto the surface below causing repellencies. This is most common when transparent inks are used to tint windows but it can happen with any ink. In order to overcome this either print the lacquer as the first operation or if this is not possible, paper interleaving should be used to separate panels during stacking.
Antistatic sprays can also contaminate film surfaces even if used some distance from the printer.
2.2 Stirring Lacquers
Due to their formulation, lacquers will separate during storage and hence it is essential that they are thoroughly stirred before printing. Failure to do so may result in poor quality cosmetics. For best results, stir vigorously for 2 minutes - air bubbles formed will not transfer to the printed substrate.
2.3 Printing Tips
Dust contamination is not generally a problem with textured lacquers. Wash marks and squeegee lines are more prominent. The slightest damage to a squeegee edge may leave a line in the print. Blades must be maintained in the best condition. Wash marks are caused by the lacquer rolling over at the end of the stroke. This will stop a short while after the squeegee starts moving. Allowing 20cm of squeegee and flood bar travel beyond the image area should allow the lacquer to settle before reaching the print area.
The printed thickness of Fototex UV Matt will change the gloss level. Thicker prints will appear glossier. More information can be found in the Fototex Processing and Safety Guidelines.