Q1: Why are Inkjet Films referred to as Waterproof Film?
EIE INKJET FILMS are designed with high-grade P.E.T Films with a microporous Inkjet Coating (simply put, ‘ink absorbent coating’) on the top and antistatic coating on the back as shown below (fig.1.1):
This Microporous Coating is often mistakenly referred to as ‘Waterproof’ Coating and hence the term Waterproof film. When factually it is basically just a BLEED RESISTANT coating. A truly waterproof coating would repel the water-based ink. A more appropriate term is bleed resistant film, but it got named before pigment inks were mainstream. Pigment inks just use microporous coatings because the particles in the ink need to be able to go into the coating.
The particles contained in pigment ink can't be absorbed into swell-able coatings. The liquid can go inside, but the pigment particles will sit on the top like ‘sprinkles’ on a frosted donut
Q2: What are Pigment based inks?
INK = PIGMENT + VEHICLE
- Pigment – gives the color to the ink. They are micro granules of color suspended in the Vehicle.
- Vehicle – is what carries the ink in liquid form, i.e Water + Glycol (or glycerol humectant additives)
A vehicle is the carrier of the Pigment to the destination. After the ink is manufactured and filled in a cartridge, the Vehicle must:
- keep the pigments in suspension.
- make sure the pigments don’t settle down to the bottom. Otherwise, it would clog heads of the printer and cause expensive repairs.
- slow the drying process until it hits the surface of the film.
Q3: How does Microporous coating work?
This microporous coating is designed to absorb the water (Vehicle) contained in the pigments inks with a “Capillary” action. However, the Pigment particles can't be absorbed into the microporous coating. The vehicle can be absorbed into the pores, but the pigment particles will sit on the top like ‘sprinkles’ on a frosted donut the vehicle eventually dries and only the pigment is left in the capillaries of the coating.
Q4: Are the Films completely dry when they come out of the Printer?
In general terms, yes, they are completely dry to your touch. Technically speaking, they are NOT! They are ONLY DRY TO TOUCH.
When the ink is put on the film, the Pigment and Vehicle* are trapped in the microporous coating. In order to prove this, we applied heat to the film in our Labs, what we saw was that the trapped glycol* would immediately turn in to steam and create bubbles.
* (Refer to question #Q2)
Hence, we recommend printers adhere to the following operating specifications when imaging films & storing films:
- Required temperature for optimum performance 60° – 80°F (15° – 25°C)
- Required humidity for optimum performance 40% – 55% RH
(Note: High humidity will prolong the drying time or the ability to absorb ink)
Q5: Why does ink stick to stencil sometimes?
Knowing what we know about the Film, Coating, and Inks, we can now understand how the imaging of the film works.
Add to this, Inkjet Ink manufacturers must balance the temptation between manufacturing fast drying inks or inks that require less nozzle maintenance due to dried ink in the cartridge and thus having to replace the expensive inkjet cartridge. Glycol or glycerol humectants are added to the water-based ink vehicle to keep the pigments in suspension, retard drying, and prevent nozzle blockage. This also is the reason for slow evaporation of the inkjet ink in your art room.
Microporous EIE Inkjet Film allows the water (vehicle) in the pigment inks to penetrate the coating and appear dry to the touch, yet remain wet inside. Hence, you still need a dry stencil and dry positive to avoid the sticking of the inkjet ink to the stencil. Otherwise, the combination of vacuum and moisture will damage your positive when the ink pulls out.
Ideally, we would suggest you follow the recommended Temperature and Relative Humidity in your art room. And if you plan to store the film let it dry for 24 hours before storing.
Q6: What do I do if the positive gets wet?
It’s not uncommon when the water spills on the film due to crammed up art room or just pure accident. The best thing to do is just hang the film to dry completely and re-use.
Q7: Image Quality of the Positive is not good?
There could be a number of factors:Check to see that the digital artwork you have from your client is of adequate resolution.
Line Art should be at a resolution of 1200 dpi.
Color or grayscale art should be at a minimum of 300 dpi.
Check to see that you are printing at a proper resolution.Positives should be printed at a minimum of 720 dpi.
However, if time is not a constraint, 1440 dpi is recommended. When printing at 1440 dpi the speed would reduce.
Be sure to choose the right media from PRINTER PROPERTIES MENU, when printingEIE INKJET FILMS choose FILM MEDIA. This tells the printer what type of media is going through it and allows the printer to automatically selects a speed to suit the film.
Are you using a RIP Software?
RIP Software would typically help improve the print quality, resulting in smoother line edges and clean halftone dots.
It also helps you to pick halftones if you are doing separations.
Q8: Why is RIP Software Required?
Inkjet printers are designed to reproduce color prints on white paper, but screen printers need high contrast positive images on clear film, with hard sharp edges and opacity to stop UV light from touching the stencil. Otherwise, you would have a poorly exposed stencil. This is not easy to do with transparent inks (viz. Epson K3 or pigment inks) designed to create full-color prints by the overlapping and blending of CMYK inks. To get a dark positive, you need to increase ink deposit, and to control the dot gain from all that ink - and convert vector image curves into bitmap images that can be printed, you need a software RIP.
Q9: Why are my Positives not very Dense?
We hope you have followed our instructions discussed in the Q6 & Q7. However, if you continue to have density issues with the films, check the following:
- Convert the artwork to B&W and make sure there is no residual CMY or RGB colors in the artwork.
- While printing, print with Black only versus using the CMY colors. Sometimes the printers mix the C, M, & Y colors to get black colors instead of using Pure Black.
If these answers in Q6, Q7, and Q8 have still not resolved your Density issues and you are assured that you have a good quality of pigment ink in your printer, then your last resort is to look at Dye Based Inks. Dye Based inks penetrate better into the capillary of the film yielding better density. Pigment-based inks remain on the surface (as pigment particles cannot penetrate deep) yielding lesser density.
Q10: Can I store EIE INKJET FILMS?
Absolutely.EIE INKJET FILMS can easily be archived for future use. For best results, store printed positives in a cool, dry place. It is also recommended to interleave with clean newsprint or tissue paper.
This blog post is written by Sales Staff of 4S Graphics, Inc, based off of various articles, news and technical papers found on the internet along with extensive sales knowledge.
DISCLAIMER: THE INFORMATION PROVIDED IS BASED ON FIELD KNOWLEDGE AND SALES STAFF DATA ACCUMULATION AND IS BEST CURRENTLY AVAILABLE ON THIS SUBJECT. HENCE THE SETTINGS AND SUGGESTIONS MADE IN THIS BLOG POST MUST ONLY BE REGARDED AS A GENERAL GUIDE TO MATERIAL PROPERTIES AND NOT A GUARANTEE. THE SUGGESTIONS MADE IN THIS E-BOOK IS GIVEN IN GOOD FAITH, BUT 4S GRAPHICS, INC. OR ITS AFFILIATES MAY NOT BE HELD LIABLE FOR LOSS OR DAMAGE ARISING FROM ACTION BASED ON THE INFORMATION PROVIDED.