The Wonderful World of Colour
Sue Williams reports on this SDC London region event which took place in March 2014.
Richard Straughan, President of the SDC and a member of the London Region gave the Ismar Glasman Memorial lecture, entitled The Wonderful World of Colour.
Richard talked about how colour is very important, it constantly surrounds us and we use it in virtually every area of our lives, it is used to convey moods and individuality. Underground maps would be impossible to use without it. We use it for brand and product recognition. Colour allows us to know that a fruit is ripe.
Colour is used in symbolism such as hot colours like reds and oranges to evoke anger and strength whereas blues and greens can evoke calm moods and feelings of tranquility. Our association with colour has to be modified when you change cultures, in the West we relate black to a colour of mourning but in China it is white.
Colour is used heavily in advertising and all of us have come to make instant associations in supermarkets with economy, luxury, diet, healthy, eco friendly etc from the colour of the packaging.
Each colour has its own wavelength and frequency. Colours that we see are created by the way light is absorbed by and reflected by the object, so dark colours absorb more and reflect less and light colours reflect more and absorb less. But what about colours that we can’t see? Generally colours are defined by what we can see but if we cannot see it, is it a colour?
Textiles Coloration has been and still is the major part of Richard’s business life. However over the last few years he has been very interested in the many and varied uses of dyes and pigments outside of textiles and the way these colours are adapted for use. Richard broke his lecture down into four areas:
- Textiles – a brief summary of the dyeing and printing of cellulose (cotton) with Reactive dyes.
- OLED (Organic Light Emitting Diode) – used in TV Screens and Monitors
- Security pigments
- Molecular imaging – a new technology which has a growing impact on our lives
1. Textiles Printing Cellulosics
Designers are looking for deeper, richer and brighter shades on cotton with better fastness and lower environmental impact.
The current state of the business is that the conventional dyes ie MCT – Mono Chloro Triazine and are generally known as the Reactive P Type – are still the major dyestuff to be applied, as they still give the best results in pale shades and bright shades. The new generation of Reactive dyes, which are bi or tri functional, are employed for very deep shades. They have much higher fixation which results in deeper shades with better wash off properties saving customer time, energy and water which provides cost savings. This new generation of dyes are used with the conventional type to achieve certain shade such as a bright red to enhance the shade or bright blue to make a brighter navy shade. There are no bright colours in this new range but they present very big savings for navies, browns, burgundy and bottle greens and with better fastness.
Digital printing is a market which is growing very fast because:
- from design to print is almost instant with no costs for engraving etc
- higher print definition can be achieved giving more design opportunities
- short runs are possible without big cost implication
- machine speeds are increasing and will result in higher productivity and lower print cost.
The next step may well be machines combining 3D printing and digital printing
The target was low temperature dyeing with a warm wash off at 40⁰C but it is proving difficult to meet the high fastness demanded by retailers. With regards to Jet dyeing this project will require customers to have dyeing machines with a good transportation system that can give smooth running of fabric at such a low temperature. Dyeing at 60⁰C and washing off at 60⁰C has and is being achieved for pale shades and selected medium shades. These dyes were launched by Huntsman. To date this has not been achieved for medium to dark shades and is top of the wish list for all dye houses. Ultra Deep Shades are being achieved with lower amounts of dyestuff eg if we use the benchmark of CI Reactive Yellow 145 150% , Red 195 150% and Blue 222 as these dyes are available from all major players. The new ultra deep dyes can save up to 50% in colour consumption plus wash off is quicker due to such high fixation value when compared with the above benchmark items. There have been a small number of new items introduced in Brill Colours but nothing outstanding. There is only one fluorescent dye, a Yellow from Dystar, with no competitors. Recently a short range of dyes for dark shades have been introduced, which can be used for dyeing by exhaust, continuous and printing methods. One dye, three methods with excellent fixation, good wash off and high wet fastness.
OLED means Organic light Emitting Diode and this market is dominated by the Japanese, Korean, Taiwanese and Chinese. It was interesting that in the past the UK had and may still have many patents surrounding this screen technology.
For many years the pigments employed for OLED screens were made in Japan and now they are made in Japan and South Korea. Pigments have high light fastness and the technology is required to make the pigments to a very small particle size and shape. Recently Wiseman Chemicals in Korea introduced dyestuffs into this market. The advantage is higher clarity of colour (cleaner brighter screens); faster refresh time, lower energy consumption. The first maker to adopt this technology was Samsung and TVs started to arrive in the EU in approximately November 2012. These new screens are a hybrid in that they use pigment Blue and Yellow and Red which are dyes. The reason is that there is no dye with good enough light fastness to match the blue pigment at present.
3. Organic Phosphors & Security Material
Used for bank notes, passports, security tags etc. They are Nano Organic Metal Complex for Special Pigments. Many of these pigments are based on rare earth materials and NIR pigments are often substituted, copper phthalocyanines.
Their uniqueness is their emission and excitation wavelengths also their reflectance and absorption peaks, together with their unique fastness performance. Security Pigments are invisible to visible light. They have unique reflectance to give read points for banks to try to prevent counterfeit or passport fraud. Many features are not detectable by the human eye. Generally they are invisible in daylight and do not show their true colours until they are exposed to UV light. However an NIR Blue pigment is a very pale blue in daylight and black when exposed to Infra red.
A Red pigment was shown under daylight and under UV the full bright Red shade is exposed. It is excited at 365 and emits in the visible range at 618 nm. Richard showed other pigments giving different effects. Fastness properties were shown which are totally different to textiles. The soap solution test was shown which changed the printed shade dramatically. Ideally the shade change should be small however this disadvantage can be used as a unique security feature.
NIR pigments properties: they are durable and stable in chemicals (Acid, Alkali, Treat of soap) and solvents, excellent light fastness, cannot be reproduced, quick detection and various colors are available – Yellow green, Red, Green, Blue & Violet. In this case shown the NIR Pigment is very pale blue and when mixed with a conventional pigment can slightly change the resultant in daylight but when passed under NIR at certain wavelength eg 880 or 1050nm it shows black. In this case the NIR is only in this area. Richard showed examples of a NIR red pigment and a NIR Blue pigment, absorbing 880 and reflecting over 1000 nm. Intaglio inks can be used with security features, in the case shown a White NIR ink is used so that images in daylight are pale but in NIR they appear black as it absorbs the light. Richard then demonstrated various passports and visas and stamps under daylight and under UV.
4. Molecular Imaging
Molecular Imaging is the detection of diseases at the molecular level, a technology discovered by Dr Roger Tsien of UCSD University of California in San Deigo in 2008 when he extracted fluorescent material from jellyfish. He was awarded The Nobel Prize in Chemistry for his work. Molecular Imaging allows visual diagnoses of diseases sooner, all at the cell and DNA level. In the long term, this will bring about reformation of the current medical insurance structure as well as reduced overall social costs. Molecular Imaging is already being used in many applications, from basic lab research to clinical. M.I fills in for the shortcomings of other diagnostic methods, acting as a complementary method to others, better established rather than being competitive.
Optical Imaging; Magnetic Resonance Imaging; Ultrasound Imaging; PET (Positron Emission Tomography Nuclear medicine functional imaging technique that produces a 3 dimensional image of functional processes in the body); SPECT (Single Photon Emission Computed Tomography) a type of Nuclear Imaging Test that shows how blood flows through tissues and organs; CT (Computerised Tomography) commonly known as a cat scan this uses X rays and a computer to produce detailed images of the inside of the body.
This technology has its roots in the manufacturing techniques developed during the Industrial Revolution. Various chromophores bind with specified proteins of cancer cells to react as visual feedback. What they do is apply the macro manufacturing technology and apply it at the micro, molecular level, creating fluorescent results instead of color. This technology is still in development, but should be familiar to people in the industry due to the many similarities to traditional textile dye development procedure.
There are many colors of the spectrum available for every application’s requirements. Blues, oranges, greens… Richard talked of the different colours and their use. He showed a section of pigs dyed lymph node. Water solubility is important as the human body is mainly water. Bio med dyes were discussed as competitive, high quality and not mass produced.
M.I. is going beyond simply diagnosing diseases. Instruments are evolving to combine diagnoses and treatment in one procedure. Compared to conventional, multi-step (slow) breast cancer diagnosis methods, M.I. is faster, more comfortable for the patient, and boasts a higher standard of accuracy in targeting cancer cell locations.
Dr Roger Tsien has published a paper on lymph-node contrast surgery for pre clinical trials. Previously a very sensitive area for surgery due to the high risk of damage, the visual contrast provided through dyes allows the surgeon to see precisely where he needs to operate and this minimises unwanted tissue disturbance.
Dr Frangioni, a Professor at Harvard University and a notable M.I. scientist, uses M.I. machinery and this was shown. Also a slide showed pictures extracted from a colour video against pictures under NIR Fluoroecence then with the colour video and NIR merged showing fluorescent green areas which is highlighting the area where the surgeon would operate. M.I. has gone beyond in vitro diagnostics, animal testing and is now entering in vivo trials.
Members of our modern society with higher quality food and medical technology are now living longer. However, that life must be healthy for it to not burden loved ones. COLOR diagnostic technology can reduce the cost of medical treatments as well as increase the likelihood of recovery through early detection and treatment. M.I. technology will increase the quality of our lives.
The materials used in M.I. are some of the most valuable per unit weight on Earth. At 200,000 $ per gm!!
Richard concluded his talk by thanking everyone for the opportunity to speak and with a special thanks to Mr JJ Na of BioActs Ltd for providing the very special data for the Molecular Imaging data.
Regular SDC events take place – check out the SDC website for details: http://www.sdc.org.uk/event/
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