A brief A-Z of terms used in our industry.
Adhesion is the bond made between two dissimilar materials caused by molecular interactions between the adhesive and the surface of the substrate. The force of a molecular bond is measured in Newtons per 25mm2 and the strength can be measured using various tests such as 90o peel adhesion (See Fig.1 below).
Peel adhesion tests, where the force required to peel the media defines how strong the adhesive is are commonly used for self-adhesive vinyl and films. The results can be catergorised as:
Adhesion failure results in delamination of the film and adhesive from the substrate.
Adhesives come in various forms and each vinyl or film will have the right adhesive properties to match the material characteristics:
The angle of the cutting blade is measured in o degrees. The correct blade angle depends entirely on the material being cut. Here is a general guideline:
Product | Blade Angle |
---|---|
Standard Signmaking Vinyl | 45o |
Heat Transfer Flex Films | 45o |
Flock | 60o |
Reflective Vinyl | 60o |
Floor Laminate | 60o |
Sandblast Films | 60o |
Magnetic | 60o |
Calendered films are the most commonly used type by signmakers and large format printers. They start life as solid granules that are melted and compounded with heat and pressure in a mixing unit. This is then extruded, being drawn through a series of temperature controlled rollers which stretches and flattens it to a uniform thickness; typically between 70µ - 100µ. Calendered films come in two main catergories; monomeric and polymeric.
Cast films are made differently to calendered films, starting off as a liquid which is then poured onto a casting sheet before moving slowly through a set of temperature controlled ovens where the liquid evaporates leaving behind an extremely thin layer. This then gets rolled; typically to 50µ or even as thin as 30µ. Cast films have little internal tension and are dimensionally stable, so shrinkage is barely perceptible. Cast films are thinner and softer, they are highly flexible and easier to apply over 3D curved surfaces using heat. With a durability in excess of 10 years, cast vinyl offers ultimate durability.
CMYK stands for Cyan, Magenta, Yellow and Black (K stands for key as it was the black plate that was called to key plate on old printing presses) and printers lay down these colours in layers of dots (see dpi below) to produce the colour that the eye will see. This mode is used for all litho and digital printing.
Cohesion is the bonding of the particles within the adhesive that holds it together, gives it internal strength and prevents it from splitting and leaving a residue.
Shear adhesion tests are ideal for measuring the cohesive properties of a bond either horizontally or vertically which is commonly used for double sided tapes (See Fig.2 below).
Cohesion failure results in the physical separation of the adhesive which will leave a residue.
Some plastic films with a low surface energy can be made more receptive to printing inks, coatings and adhesives by passing the material through a corona treatment process. This modifies the surface energy to improve adhesion and is done during production by converting standard electricity into high frequency power and delivering it to the surface by means of a ceramic or metal electrode over an air gap.
The cutting force value is measured in grams (gf) and depends entirely on the material being cut and the angle of the blade being used. Here is a general guideline:
Product | Grams of Force Value (gf) |
---|---|
Standard Signmaking Vinyl | 30-100 |
Heat Transfer Flex Films | 30-100 |
Flock | 80-160 |
Reflective Vinyl | 100-350 |
Floor Laminate | 100-350 |
Sandblast Films | 100-500 |
Magnetic | 150-600 |
DPI stands for Dots per Inch and refers to the amount of printed dots in an inch of the print. The larger the DPI, the higher number of dots and the clearer the print will be.
Usually, the higher the DPI, the higher quality of print and this is important for large format graphics but it is not always necessary to print at the highest DPI. If the print is small, using a high DPI may just be a waste of ink and might result in poor drying times.
This stands for 'grams per square metre' and is the weight measure for various non-adhesive flexible media such as paper, canvas and banner.
The European measurement commonly used to display the thickness of a vinyl film. 1 micron (µ) equals one thousandth of a millimetre, 0.001mm. A typical 75µ vinyl is therefore thinner than one tenth of a mm.
The American measurement commonly used to display the thickness of a vinyl film and not to be confused with mm. 1 mil (one thousandth of an inch) equals 0.0254mm. A typical 75µ vinyl could therefore be described a 3 mil.
Monomeric grade PVC is the most economical and least durable, best suited to interior and short-term exterior applications (4 years for Black & White, 3 years for colours) on to flat 1D and slightly curved 2D surfaces.
The monomeric plasticisers used in their production to make the film softer and more flexible have a low molecular weight which after time, slowly migrates to the surface of the film causing it to shrink and become brittle. These films are therefore not suitable for demanding exterior applications such as vehicle graphics or fascia signage as it will almost certainly start shrink back from the edges to reveal the adhesive beneath. Once this starts, any dirt in the atmosphere will quickly create a dirty grey outline around the graphics and eventually, the vinyl will begin to flake off like peeling paint.
The offset value is the distance from the centre of the blade to the cutting edge of the blade and is specified by the manufacturer of the blade. The offset determines the blade's turning radius and how it compensates for distance while turning corners.
A term used to describe how light is either blocked or passes through a vinyl or film. For our industry is can be broken down to:
Polymeric grade vinyl uses polymeric plasticisers that have a more complex molecular chain meaning that they shrink back at a slower rate. This makes them more durable and with better UV and temperature resistance, suitable for longer term use outdoors on 1D and 2D surfaces (10 years for Black & White, 8 years for colours). If used on more complex curves, it is still recommended to cut and overlap seams as opposed to heating a stretching like you can a cast film (see below).
Raster images are pixel based and are best used when printing non line art images such as photographs as it is possible to include chromatic graduation and complex composition. Raster files are resolution specific meaning that they are intended to be displayed at one specific resolution. Increasing the image size will result in a loss of quality with images looking jagged and decreasing the size will result in blurry less crisp images. Raster file types include TIFF, JPEG, GIF, PNG and BMP and are also the most common type of file for displaying web graphics on screen.
Liners fall in to two catergories:
RGB stands for Red, Green and Blue and represents colours of light that is viewable on a screen or monitor making it perfect for use on website and digital advertising.
If a graphic file is sent to print using RGB colour mode it will look very different that if it was sent over in CMYK format. This is because the printer has to change the image to CMYK to be able to process it correctly so it is always recommended that when sending artwork to print that it is done in CMYK mode.
There are two factors that will determine how strong the adhesive needs to be to stick to a particular surface. These are the finish of the surface and the surface energy.
Tack refers to the initial stickiness of the adhesive and indicates how quickly a bond is formed when brought into contact with the substrate. There are various factors than can influence initial tack such as the surface energy of the substrate and temperature.
Vector images are based on mathematical formula that define geometric curves, circle, polygons and lines. Because of this vector graphics are best used for line art graphics such as logos, icons, charts and text. They are much more versatile than raster graphics and flexible so that graphics can be resized indefinitely without the loss of quality. Vector file types include EPS, AI, PDF & SVG.
If you would like to add to or can suggest any changes to these pages please feel free to contact us
Call us on 01858 431642 , we're always happy to help!
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