Colour technology


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Colour technology

  1. 1. Colour Technology
  2. 2. Why use Colours? Identification Branding Convey a Mood or a Style Choice
  3. 3. Introduction <ul><li>Assessment and Measurement of Colour. </li></ul><ul><li>Factors Affecting Colour Matching. </li></ul><ul><li>Methods of Colouring. </li></ul>
  4. 4. Colour Assessment <ul><li>Eyesight </li></ul><ul><li>Light Source </li></ul><ul><li>Size </li></ul><ul><li>Background Colour </li></ul><ul><li>Surface Finish </li></ul><ul><li>Metamerism </li></ul>observer object light source
  5. 5. Human Visual System
  6. 6. The Retina <ul><li>Retina uses special cells called “rods” and “cones” . </li></ul><ul><li>Rods “sees” in black, white & shades of grey and tell us the form or shape. (Super-sensitive allowing us to see when it's very dark.) </li></ul><ul><li>Cones “senses” colour but need more light. Three types and each is sensitive to one of three different colours - red, green, or blue. Together these can sense combinations of light waves. (To see millions of colours.) </li></ul><ul><li>Rods and cones together process the light to give you the total picture. </li></ul>
  7. 7. The Rods and Cones
  8. 8. The Rods and Cones 5 million per eye (more L and M cones than S cones) 100 million per eye Responsible for daylight (photopic) vision Responsible for low- level (scotopic) vision Cone function Rod function scotopic mesopic photopic luminance Cones Rods
  9. 9. Eyesight <ul><li>Individuals perceive colour differently. Is “ Sky Blue ” the same as “ Pale Blue ”? </li></ul><ul><li>How many People are Colour-Blind? </li></ul><ul><li>Experts are “turned in” to Colours. </li></ul>
  10. 10. Light source <ul><li>A red object in red light, appear red - as all the red light is reflected. </li></ul><ul><li>A red object in blue light, appear black - as no red light to reflect back. </li></ul><ul><li>The difference between say daylight and the Tungsten Lights used in homes, could be significant!! </li></ul>
  11. 11. Size <ul><li>A small area of colour may look very different to a large area of the SAME colour. </li></ul>Hence, it is important when decorating to paint a sufficiently large area.
  12. 12. Background colour <ul><li>Colours viewed against a strong, vivid coloured backgrounds, appears very different against a neutral or pastel coloured background. </li></ul>
  13. 14. Surface finish <ul><li>A high gloss finish always appears darker than a matt finish of the same colour. </li></ul>
  14. 15. Metamerism <ul><li>Change in appearance of a colour under different light source. </li></ul><ul><li>Describe the relative changes in colour between two samples, i.e. Good match in day light, different in fluorescent shop lighting. </li></ul><ul><li>Occurs when different colourants are used in each sample. </li></ul>
  15. 16. Colour Measurement <ul><li>Colour Space </li></ul><ul><li>Colour Measuring Devices </li></ul><ul><ul><li>Colorimeters </li></ul></ul><ul><ul><li>Spectrophotometers </li></ul></ul><ul><li>Metamerism </li></ul><ul><li>Light Sources and Illuminates </li></ul>
  16. 17. Colour
  17. 18. Colour Space <ul><li>To measure colour objectively, to communicate differences in quantifiable terms. </li></ul><ul><li>Principle is that all colours can be inside a “Colour Space” i.e. this space being a sphere. </li></ul><ul><li>Each colour can then be give a position in the colour space. </li></ul><ul><li>Differences between colours can be quantified by comparing the values of the co-ordinates. </li></ul>
  18. 19. Colour Space + L = Lightness - L* = Darkness + a* = Redness - a* = Greeness + b* = Yellowness - b* = Blueness +a* +b* -a* -b* L*=100 L*=0 L* L* -a* +a* -b* +b*
  19. 20. Colour Space - Delta E a* b*  C*  H* is the difference between two points in colour space, often use to determine a colour tolerance or specification. S C S H
  20. 21. Colour Space <ul><li>A different system (Yxy) is used for transparent colours. </li></ul><ul><li>Y = percentage of light transmitted </li></ul><ul><li>x = balance between blue and red light </li></ul><ul><li>y = balance between blue and green light </li></ul>
  21. 22. More on Metamerism <ul><li>Two colours with the same L*,a*,b* values which are arrived at by a different route will show metamerism. </li></ul><ul><li>Their colour will be different if the light source is changed. </li></ul>
  22. 23. Colour Measuring Devices <ul><li>Colorimeters </li></ul><ul><li>Filters the reflected lights into Red, Green an blue lights and measure the relative amounts of each, then calculates the numerical lab value. </li></ul>
  23. 24. Colour Measuring Devices <ul><li>Spectrophotometers </li></ul><ul><li>Measure the reflected lights at regular intervals across the visible spectrum, then produces a graph of the spectrum of light reflected by the colour called the Spectral Curve. </li></ul>
  24. 25. Colour Measuring Devices <ul><li>Spectrophotometers more accurate than colorimeters. </li></ul><ul><li>Spectrophotometers better at identifying metamerism than colorimeters. </li></ul><ul><li>Differences between the human eye and colour measuring devices > Possible to have an accurate reading but does not visually look right!!!! </li></ul>
  25. 26. Light sources and illuminants <ul><li>The three most widely used are; </li></ul><ul><li>D65 Simulation of Daylight (Artificial Daylight). </li></ul><ul><li>A Normal domestic tungsten light. </li></ul><ul><li>TL84 Standard fluorescent tube used in most shops and showrooms. </li></ul>
  26. 27. Colour Matching <ul><li>Standard Colour Systems </li></ul><ul><li>The Material </li></ul><ul><li>Colorants </li></ul><ul><li>Legal Restrictions </li></ul>
  27. 28. Standard Colour Systems <ul><li>Colours presented as printed paper patterns books. (RAL and PANTONE system.) </li></ul><ul><li>Building industry has its own set of BS colours. </li></ul><ul><li>NCS (Scandinavian) a measuring system rather than a fixed set of colours. </li></ul>
  28. 29. The Material <ul><li>Processing temperatures and chemical characteristics, means a colourant can work in one polymer, but degrade or discolour in another. </li></ul><ul><li>The more different the standard material is to the match material, the less likely an accurate match. </li></ul><ul><li>A painted sheet match to Nylon 6.6, the colourants used in paint will not survive 290 o C. </li></ul>
  29. 30. The colourants-Pigments <ul><li>Very fine powdered chemicals dispersed in the polymers. </li></ul><ul><li>Poor dispersion results in a weaker colour and often a grainy surface. </li></ul><ul><li>Inorganic pigments are mineral based, i.e. Metal Oxides & Sulphides. </li></ul><ul><li>Organic pigments are chemical compounds, less heat stable and more difficult to disperse. Usually give richer and more vivid colours. Less pigment is required. </li></ul>
  30. 31. The colourants-Dyes <ul><li>Chemical substances that dissolves in the polymer. </li></ul><ul><li>Chemically interact, as such allows light to pass through. When use in transparent materials remain transparent. </li></ul><ul><li>A limit how much dye can be added to a polymer, the dye can bleed out! </li></ul><ul><li>Insoluble in Polyolefins. </li></ul>
  31. 32. Legal Restrictions <ul><li>Food, Medical and Toy - mainly base on purity and inability to extract the colourant from the finish item. </li></ul><ul><li>Cadmium pigments - base on the premise when the Plastic part is incinerated, they can release Cadmium metals. Applies mainly in the packaging industry. </li></ul><ul><li>If a colour is required for safety purposes, then Cadmium pigments can be use regardless of the Cadmium legislation. </li></ul><ul><li>Many companies have a “Cadmium Free” policy regardless of the details of the legislation. </li></ul>
  32. 33. Methods of colouring <ul><li>Dry Colour </li></ul><ul><li>Masterbatch </li></ul><ul><li>Liquid Colour </li></ul><ul><li>Fully Compounded Colour </li></ul>
  33. 34. Dry Colour or Dry Blend <ul><li>The colourants are mixed with the polymer. Some dispersion aids may be added and often a “wetting agent” to help bind the powder onto the surface. </li></ul><ul><li>Advantages : Cheap because the conversion cost is low. Quick to prepare. Very small lot. </li></ul><ul><li>Disadvantages : Can be very Messy, can affect drying, colour can vary with different machine due to dispersion. </li></ul>
  34. 35. Masterbatch <ul><li>Compounds contains very high levels of colourants (up to 80%), then mixed at a fixed ratio to give a specific colour. </li></ul><ul><li>“ Polymer Specific” - Carrier is the same material as the base material. </li></ul><ul><li>“ Universal” - Carrier will readily mix with a wide variety of polymers. </li></ul><ul><li>Advantages : Better colour control, cleaner and less drying problems than Dry-colour. A stock range of colours and specific colours can be develop. </li></ul><ul><li>Disadvantages : May not always be compatible with the base polymer. Accuracy depends on the Moulder with mixing. </li></ul>
  35. 36. Liquid colour <ul><li>Similar to masterbatches, contains a high level of colourants, but the carrier is a liquid. </li></ul><ul><li>Advantages : Better colour control than Dry blend. More even distribution than masterbatch. Stock range of colours. </li></ul><ul><li>Disadvantages : Special dosing equipment is required. Spillage is messy. Colour can depends on processing. Properties can be affected by the liquid carrier. </li></ul>
  36. 37. Fully compounded colour <ul><li>The colourants are added to the base Polymers, then extruded to encapsulate the colour into the polymer and is fully dispersed. </li></ul><ul><li>Advantages : Specific, accurate and controlled colours. The performance of the compounds is more predictable. Ease of handling. </li></ul><ul><li>Disadvantages : Less flexible than the other methods. </li></ul>
  37. 38. A Polymer for Every Application