Coating & Laminating
conductor after being doped.
Polymer or plasticised semi-conductors do not have to be manufactured by the laborious and time consuming photo-masking process and are categorised as being a printed electronic product with coating being an important process. A custom bespoke VCM pilot/production line coater has been designed, developed and supplied by RK Print Coat Instruments to a customer for this purpose. Coating, especially coating thin onto thin materials at high machine speeds requires some care and attention. Thinner substrates can deform and wrinkle far easier than thicker substrates. Thinner webs require lower tension levels, especially with regard to extensible films. Lower tension levels (and machine speed) avoid necking down of the substrate.
Coating voids, wrinkles and gauge band variations due to rollers that have become misaligned are certainly speed and quality limiters. It’s worth noting however, that wrinkles and coating voids can be due to other causes. Thinner webs are more prone to be less uniform and are more easily affected by heat, moisture and solvents, which can be problematic when drying or curing and when coating and laminating.
Substrates and inks and coatings can sometimes baffle the printer/converter. Optical brighteners added to certain papers can affect spectrometer readings. In applications where flexo is the print process of choice such as paperboard and corrugated applications and when providing a
customer with a colour match it is essential that the sample given is identical to the stock that will be commercially printed upon.
Colour communication, sample preparation devices such as the FlexiProof for all flexo pre-press applications and for ink/coating/ adhesive producers and suppliers is useful for evaluating colour: visually and on-screen and for highlighting and as an aid to resolving print related conundrums.
Printing a given colour on Kraft, mottled or clay-coated sheets will yield quite different shades even when printing with the same colour. The reason being that sheets with high absorption properties will produce a weaker looking colour. Conversely sheets with lower absorption properties will produce a stronger looking colour. If a clay coated substrate is used the ink may not even penetrate the surface.
When coating a moving web uniformity across the width of the web is essential. Coating uniformly with no variation in the transverse or machine direction depends on every element associated with the coater functioning harmoniously. Speed of throughput may create difficulties. Air entrapment in webs as they flow over rolls may cause slippage between web and roll face. Poor tension control limits throughput for a variety of reasons, one of which is that there is a greater risk of web breaks, wrap around driven rollers and a higher level of waste.
Generally, problems associated with tension
control limits the ability to run at high machine speeds. Inappropriate or poorly controlled tension it could be argued has a bigger impact on the commercial effectiveness of a converter when undertaking short run work.
The reason being that the increased frequency of product changeover and make-ready coupled with process irregularities can slow production down still further, increasing the risk that the converter will miss deliveries.
Coating thin and at speed gives converters and manufactures pause for thought. Many coating lines are designed to operate within a reasonable product and process window. That window may be limited when it comes to functioning efficiently and delivering thin film and specialist products using a standard production line coating system. There are many different coating applicator technologies to chose from. They all have advantages and disadvantages; no single method is suitable for every application. They differ with regard to optimum coating deposition, viscosity and line speed capability. An unsuitable coating choice jeopardises product quality and performance; it can also be a speed limiter. Custom designed the VCM can be configured to incorporate a wide range of print, coat and laminating technology. It is sturdily constructed and incorporates the best available web handling and control technology. The framework is also designed to allow for modification in the future if operational circumstances change.
32
July/August 2023
www.convertermag.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
