Products

TORAY waterless chemistry - function/application

Printing plate developer/cleaner for TORAY waterless printing plates

Griso-Chemie AG, as licensee for Europe, America and Asia, produces developers and cleaners for the waterless printing plates of TORAY from Japan.

From our production base in Rotkreuz, we market our products virtually everywhere in the world. Our subsidiary company, GRISO CHEMICAL INC. in the USA guarantees the rapid availability of our products in North and South America.

As members of the Waterless Printing Association and the European Waterless Printing Association, we are in contact with distributors and users of waterless print technology. In seminars and practical sessions, experience with this special printing technology is exchanged amongst those taking part. The Waterless Printing Association attempts to bring together machine manufacturers, distributors and users to jointly promote waterless offset printing. Waterless printing is one of the greatest innovations in the recent history of the printing industry and, thanks to the latest developments in the printing press industry, it enjoys an application range that is becoming more and more extensive. Therefore, some well-known newspaper printing houses have decided on waterless printing technology and their experiences have been excellent.

TORAY WATERLESS PLATE

Enrich colors, stimulate your output & save the earth

History of waterless offset printing

Offset printing uses two separate media, namely printing ink and dampening solution. For a long time, attempts have been made to operate a flat printing process with only ink. Over a century after the invention of flat printing itself by A. Senefelder (Munich 1798), the great pioneer Caspar Hermann was experimenting between 1926 and 1931 in Vienna and Leipzig with attempts to develop a flat printing process which did not use dampening solution. He eventually achieved it by making complicated modifications to the ink. Heinrich Renck approached matters differently: in 1930 in Hamburg, he developed the first special printing plate for printing without dampening solution.He started waterless commercial offset printing in the 1970s. The 3M company developed, patented and sold a plate, but soon lost its way again after enormous technical difficulties in the practical implementation of the procedure. The Japanese company, TORAY Industries, purchased the rights, supplied printing plates and for decades supported the worldwide commercial distribution and technical development of this flat printing alternative. In Germany the Marks-3zet company, as supplier of TORAY plates in Germany, supported the slow and laborious distribution process with great commitment. Using positive and negative plates, attempts were made to practically replace wet offset 1:1. A few printers adopted the technology and carried out some exemplary pioneering work.

Since the expiry of the TORAY patent a few years ago, some other plate manufacturers have entered the market, offering their own developments for particular market niches. An example worth mentioning here is the Presstek company which supplies waterless plates for DI (direct imaging) presses. (Description of Heidelberg presses: offset printing presses, which image the plates inside the machine). At the same time, König & Bauer AG in Germany began developing and supplying new machine concepts. Suppliers of printing plates and inks could therefore also push forward the development of their waterless products.

Printing principle and plate design

In the case of offset printing (indirect ink application) we are dealing with a flat printing process. In flat printing, the printing (ink carrying) parts of the printing plate can be coated with ink, whereas the image-free (or non-printing) parts cannot. Coating procedures are identified by surface tension or interfacial tension. This means that the areas on the plate to be printed (surface tension approximately 35 mN/m) accept the ink because of their high surface tension (surface tension of the ink lower, approximately 30 mN/m). The areas that are not to be printed are coated with silicone and, because of their lower surface tension (around 20 mN/m), cannot be coated with ink. With the brands currently on the market, the ink-bearing areas (mostly a polymer coat) lie directly on the substrate (aluminium or polyester) and the image-free areas on a thin layer of silicone (approximately 2 µm) that has been applied on top of this.

Depending on the manufacturer, the substrates can differ, as sometimes do the extra layers for surface protection or for activation of the imaging process.
The imaging of plates can takes place photo-mechanically (analogue) with subsequent development by hardening (positive copy) of the silicone layer or by releasing (negative copy). It can also be carried out using spark erosion (outdated, former DI technology) or by thermal ablation (abrasion) using laser beams (IR laser) (both negative). In the second case it is part of up-to-date CtP working processes (Computer to Plate, direct imaging from data). Thermal ablation is currently one of the sharpest imaging techniques. It is therefore intended for modern fine screen processes, be it as a periodically structured (AM, amplitude modulated) or non-periodically structured (FM, frequency modulated) screening.

In a typical case, the application rollers of the plate surface offer a 6 - 8 µm thick coating of printing ink. An ink coating of 3 - 4 µm thickness remains adhered to the deepest image points. This makes printed surfaces very sharp at the edges and accurately dyed, one of the greatest strengths of waterless offset printing. Dot gain, which is typical of such processes as "wet offset" (over-inking of the areas to be printing and flooding into non-printing areas) is unknown, in other words never or virtually never present. In comparison with wet offset, the application consistency of the dot size increases, therefore achieving a higher quality consistency. As only the ink is applied to the plate (no dampening solution), the printing image is stabilised within fewer rotations of the cylinder, therefore reducing start-up waste to a minimum.

According to current understanding, the waterless flat printing process works by virtue of the fact that the silicone with its low surface tension prevents coating with ink that has a higher surface tension. However, the difference between the silicone and the area to be printed is only around 15 mN/m. According to general knowledge (Zisman) a coating fluid (in this case the ink) should have a lower surface tension than the solid material to be coated (the plate).

The interfacial tensions (between ink and respective surfaces - to be printed or not) are very hard to specify and here for the sake of simplicity disregarded as influencing variables (that means invariably treated as a constant). The surface tension of the ink (i.e. with the air) drops as it is heated up more quickly than that of the silicone to be used. Even at relatively low temperatures, e.g. from 32°C, ink can therefore be accepted in places by the silicone coating, therefore tones the plate punctiformly or even continuously. For this reason it is necessary in offset printing to keep the temperature in the inking system and on the printing plate constant with cooling rollers. The more energy that is introduced to the machine (running speed, running duration), the more likely toning problems are to arise and the more effectively the plate and rollers must be cooled.

Advantages of TORAY Waterless

Low start-up waste (e.g. 10 signatures instead of as many as 200)
Precision printing out of dots, better fine drawing, lower dot gain, designed for particularly fine screens (max. 300 lines/cm instead of 120 in wet offset) but also for FM screens thanks to improved reproduction of the pixel-fine dots of the periodic screen
Straightforward printing of fine reverse type in full tone areas
Printing with thicker ink layers possible, therefore higher density values with brilliant printing results. Useful for highly pigmented HiFi scales
Simpler machine construction due to lack of dampening unit and peripheral devices (preparation and control as well as disposal of dampening solution)
Lower expenditure on maintenance and cleaning of presses
No corrosion of steel parts caused by acidic dampening solution
No more gauge-pin problems relating to dimensional stability caused by the influence of the dampening solution.
Improved printability of short grain (paper fibres in running direction of press)
No more emission problems due to lack of isopropanol in the dampening solution
No trapping, better consistency across the print run of inks printed together in the screen
Fewer potential error sources, as there is no longer dampening solution to have an influence on ink drying
The oxidation of metallic inks, e.g. offset silver, is no longer possible

Disadvantages of waterless offset printing

Plates are more expensive due to the design with a silicone rubber coating
Printing inks are more expensive as they are not yet produced in sufficiently large quantities, lack of competition
Plates are harder to correct
The printing process is temperature-sensitive and requires greater investment in cooling units
In alternate operation (conventional/waterless) still generally higher cost levels; not everyone is prepared to pay for the improved print quality
Up to now only printed products where significant advantages exist are covered, such as high quality short print runs, commercial printing and printing on non-absorbent substrates. Great success in newspaper printing, thanks to better print quality of advertisements, the option of also using newspaper printing presses for other top quality printed products, lower incidence of waste.
Not yet widespread in the packaging sector, with the exception of printing on thin sheet metal, e.g. foodstuff packaging materials
Less removal of badly bonded paper fibres as the breaking up effect of the dampening solution is not present, tendency for more formation of paper scraps

Thanks to the lack of dampening solution, a large number of economic and ecological advantages also arise that will be even more important in future.

Economic advantages:

No need for water tests and expensive dampening solution additives and alcohol
No drying delays caused by the dampening solution in the printing ink, especially when printing on non-absorbent surfaces (oxidative drying)
No colour variations due to absorption of water by the printing ink (emulsifying)
No longer any need to set up the dampening system
No gauge-pin problems caused by the influence of the dampening solution on the paper
No ink misting spraying of printing inks in web offset printing

Ecological advantages:

No emissions harmful to the environment due to the use of volatile organic compounds (VOC emissions caused by alcohol) in the dampening solution.
No longer need to comply with waste water regulations because of the dampening solution
Dosing equipment for additives and alcohol no longer necessary
No more equipment for the recycling and reconditioning of the dampening solution

As in waterless printing, higher ink density values are possible, the colour spectrum is also greater compared with conventional methods
by up to 20%.

Average Solid Ink Densities
	Donnelley Bayshore	Conventional* Waterless
Black	1.63	2.10
Cyan	1.19	1.57
Magenta	1.35	1.70
Yellow	1.10	1.13
*Average of customer specified densities.

Due to the lack of dampening solution, which has an unfavourable effect on the dot count and colour gradient, substantially higher resolution can be achieved (up to 760 lines per inch = 300 lines per cm) which opens up new vistas in printed products.

The advantages listed, the increasing significance of environmental laws and the improved print quality, as well as the ease of operation of printing press for waterless offset printing make this procedure all the more interesting for many applications.

What is needed for the development of a TORAY waterless printing plate?

Printing plates for conventional wet offset are developed using a developer solution.

For TORAY waterless plates with a silicone layer as the non-printed area, you need a pre-treatment and after-treatment for the development of the printing plate.

1. Transparent protective film

2. Silicone rubber layer

3. Light-sensitive photopolymer coating

4. Primer coating

5. Aluminium substrate

Simplified representation of a CTP laser-imaging system. Easily visible are the deeper printing parts in the non-printing, ink repellent silicone layer.

Ecology: How much developer is required for printing plate development?

The chemicals are to be found in the circuit
Tankful of pre-treatment = 20 litres in the activator station
Tankful of after-treatment = 20 litres in the dyeing station
Minimal fresh water infeed for rinsing between pre- and after-treatment

Further advantages:

Approx. 5,000 m2 waterless plates can be developed with one tankful. To extend its service life, the pre-treatment can be replenished with an additive. Developer strength can be checked with a test kit.
Very low expenditure on cleaning and maintenance in comparison with wet offset
Developing machines have a long-lasting design

The development process can take place manually or in the developing machine. Manually the developer is fed through with a tampon and then dyed. The development process mostly takes place mechanically with developing machines specially designed for the purpose.

The developing fluid applied allows the silicone rubber layer on the printing plate to swell up at the non-exposed points, this is then washed off with rotating brushes manually or in the developing machine.

Finally manual or machine rinsing takes place with water. The silicone rubber constituents loosened in this way are environmentally neutral and can be washed down the drain with the water. The remaining, hardened silicone layer (non-printing areas) is about 2 micrometers higher than the photopolymer layer now exposed. As opposed to conventional printing plates, in the case of waterless offset printing, it is not the raised layer but the deeper layer that accepts the ink, which leads to an increased ink supply and therefore higher density.

The plate is dyed with the after-treatment during development. The photopolymer layer accepts the ink and the printing points become visible. Rubber coating plates as with conventional plate development is not required.

If the developing machine is regularly maintained, with the two developer solutions required (pre-treatment and after-treatment) approximately 5,000 m2 of printing plate can be developed (depending on the number of plates that are developed within a specific period of time).

Here we are differentiating between 2 printing plates, CTP (digital computer to plate) and conventional (analogue using film).

Which printing plates need which chemicals?

- For the manual development of positive analogue printing plates:

"HP-7N" developer
"MD-20" dye solution
Manual developing tampon

- For the manual development of negative analogue printing plates:
"PTS-1" pre-treatment solution
"WH-3" after-treatment solution
Manual developing tampon

- For the machine development of positive analogue printing plates:
"PP-1" pre-treatment solution
"PA-1" after-treatment solution

- For the machine development of negative analogue printing plates:
"NP-1" pre-treatment solution
"NA-1" after-treatment solution
"NA-X" after-treatment solution (dye without heavy metals)

- For the machine development of positive CTP printing plates:
"DP-1" pre-treatment solution
"PA-F" after-treatment solution

- Most-used additives/cleaning agents of TORAY Waterless
"PC-1" plate cleaner
"PC-2" plate cleaner for UV printing
PC-SPECIAL plate cleaner with antitone
"PC-SPECIAL UV" plate cleaner with antitone
"CS-1" plate conserver
PRINTON antitone paste turns conventional inks into waterless inks
Kit-pH, measurement kit for measuring developer strength of NP-1 and DP-1 pre-treatments

Übersicht der TORAY Wasserlos-Chemie

DP-1	CTP machine pre-treatment solution
PA-F	CTP machine after-treatment solution
PP-1	Positiv analog machine pre-treatment solution
PA-1	Positiv analog machine after-treatment solution
NP-1	Negative analog machine pre-treatment solution
NA-1	Negative analog machine after-treatment solution
NA-X	Negative analog machine after-treatment solution (no toxic dye)
HP-7N	Positiv analog manual developer solution
MD-20	Positiv analog manual dye solution
PTS-1	Negative analog manual pre-treatment developer
WH-3	Negative analog manual after-treatment developer
PC-1	Plate cleaner
PC-2	Plate cleaner for U.V. print
PC-SPECIAL	Plate cleaner with antiton
PC-SPECIAL U.V.	Plate cleaner for U.V. inks with antiton
CS-1	Plate conserver