TAIWAN • This article, written by Hilson Huang, CEO of Flexotech, will indicate non negative film plate making by direct inkjet image on a photopolymer plate deeply in order to compare with conventional way of plate making and digital plate with black layer coated to make image by means of an expensive laser ablation machine.
Conclusions of this article for easy understanding:
- Photographic film is no longer required, computer image can be printed direct on any photopolymer plate
- NozzleBlack inkjet printer is costing you as common as a printer from market, which is saving you lots of investment and to use expensive black-coated digital plate.
- No need to use vacuum unit any more, no more contact problem in between negative film and plate so it is easy to make a good plate with 100% success.
- @flexo CTP system simplified the plate making procedure for easy access and saving 10-20 minutes process time. Skillful engineer for plate making is no longer required.
In 1994, direct image system for photopolymer plate was first introduced, the industry has welcomed this new technology until now. It is however, expensive equipment investment and 30% higher cost of a digital plate than a conventional photopolymer plate are the reasons not able to be accepted by a plate maker or a printer widely.
Meantime, due to creative development of inkjet technology, spray an image on a non treated or coated film in detailed and fine image is very easy to achieve nowadays, so that to print a negative image on any of photopolymer plate by means of a flat bed inkjet printer no mater it is a flexographic or letterpress plate is no longer difficult to print a fine image on the plate directly any more. The printer is easy to get from the market now at reasonable price and the negative image can be reproduced sharply direct on a flexo plate.
Conventional flexo plate making
From a conventional way of plate making, these are the normal procedures:
- back exposure
- film exposure
- post exposure
Back exposure is to determine the thickness of a relief base in order to support a finished plate for long run by means of a short exposure on the back of a plate before having an image exposure with a negative film.
Film exposure is to give the plate an original image from a negative film in order for printing with design, photopolymer plate hence exposed by UVA light to harden the image area while the unhardened part is washout by the solution no mater it is a solvent washout or water washout plate, a relief plate will be ready for printing after drying and anti-tack procedure. Drying is to remove the solution completely from inside a plate during washout which is penetrated into plate, after drying the plate goes back the original thickness and good for printing. By using UVC lamps, it is a dry and easy way to remove the tack of a processed plate if in the past time have to use bleach + hydrochloric acid to achieve this function by which a pollution odor of chlorine is produced and it hurts human respiratory organs a lot.
Laser ablation image on digital plate
This is so called the pioneer of CTP, (Computer To Plate) which is using a black layer coated photopolymer plate by using laser ablation removing the layer according to image then naked photopolymer areas are waiting for UVA exposure to harden and to form printing relief after washout. Photopolymer is not sensitive to this ultra red light wave at all therefore it is no affection to the plate during UVA exposure afterwards. The digital plate is now as a plate + negative film on it, after expose to UVA lamps entirely, it is completely the same as a conventional plate with negative film exposure already now, the following procedures are the same as conventional plate making. Black layer is easy to be washout with the solution inside the washout tank automatically without any problem, but the film exposure with vacuum pump for close contact without air bubbles in between film and plate is deleted.