Laser Reactive
Laser Coding Systems
SILTECH LIMITED
Silmark
About Silmark
The on-line coding methods commonly used for the pharmaceuticals, foods and confectionary industries are Ink-jet, Thermal-transfer (including hot stamping), and Laser-ablative coding. These methods present a variety of problems: maintenance, line down-time, taint, need for extraction, etc. All these disadvantages add up to a simple conclusion: it is better to banish the problems of printing (ribbons, inks, solvents, maintenance, cost of thermal heads, unreliability, etc.) from the production lines where sensitive products like foods and pharmaceuticals are packaged.
Furthermore it is better to banish these technologies in order to remove maintenance and line down-time and the need to employ an inks technician. The Siltech IR coding system, Silmark, offers this solution and more: significant cost savings for most normal production lines can be offered, together with an opportunity to improve on the quality of the code produced. In addition, see below, several other advantages over conventional coding technologies are found, one being: Silmark is more environmentally friendly than the competitive technologies: no solvents, no taint, no waste. In short, Silmark is greener.
The space allocated on a package for the batch code, sell-by date, etc. is usually a small patch printed in a light colour to give good contrast to the (normally) black print. In the case of laser ablative printing the patch is usually of a darker ink which ablates to form a contrast with the underlying substrate; it is ugly and poor quality. With Silmark, this patch is white or lightly-coloured IR-sensitive ink, and on exposure to a threshold dose of infrared radiation, the ink turns black to give the code. The patch is printed down by flexography, screen or gravure as the packaging is made, and the add-on cost is very small.
Application
The print engine for the Silmark system comprises of a robust, low-power CO2 (10000nm wavelength) laser (Ref 5). It can operate in either the dot-matrix mode or it can be continuous-wave. In this latter mode, improved quality of print is obtained. Because of the low output of the laser, (less than 20W), highly reliable, maintenance-free, operation is offered. Silmark can operate in the continuous wave, scribe, mode and coding onto moving lines at up to 400ft/minute (120m/min) is possible. This speed caters for over 95% of filling lines. For higher speeds than this, the dot matrix mode is suggested. For the average filling line an investment of £14-18k (c.f. Inkjet £10-14k) would be required, but the payback time would usually be less than 10 months.
Features
• Silmark is a non-contact printing technology (as is ink-jet).
• Silmark offers numerous advantages over ink-jet: it gives better print quality, improved reliability, higher speeds and lower cost. It requires no inks or solvents on the packing line and produces no waste: it is “greener”.
• Silmark is suitable for all types of substrate including carton board, corrugate, paper, film, etc.
• Silmark banishes the need for inks, solvents, printing technicians, etc. from sensitive packaging areas. This is particularly important for the food and pharmaceutical industries.
Shelf Life
The ink will have a shelf life of 6 months provided the container remains tightly sealed.
It should be stored under cool conditions and be well stirred prior to use.
Packaging
Silmark inks are supplied in multiples of 5kg, 10kg and 20kg.
Technical Specification
Colour - White/Off-white opaque, or tinted as required
Solids - 45-47% approx.
Viscosity - 60-80s Zahn 2 cup @ 20C (Flexo)
pH - 7.5–8.5
Diluent - Water. The ink is supplied press-ready and should not be diluted. Please refer to Siltech Ltd.
Wash-down - Water. Should the ink set on the press, dilute ammonia solution should be tried, or “Thermal Wash” (available from Siltech).
Activation Energy - The ink will image above a threshold energy depending upon speed required. A 20-30W output is usually sufficient.
It is possible to overprint with a thermally-resistant varnish to enhance scuff resistance. Siltech can offer an appropriate varnish.
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Introduction
Application
Technical