UV Technical Glossary

Alpha-Cure UV GlossaryA comprehensive list of UV industry related terms and their definitions;

Air deposition  The  occurrence of airborne pollution (eg. mercury) falling to the ground in precipitation, dust, due to gravity. Also known as  “atmospheric deposition”.

Conformal Coating  A  protective non-conductive dielectric layer that is applied onto the printed circuit board assembly to protect the electronic assembly from damage due to contamination, salt spray, moisture, fungus, dust and corrosion caused by harsh or extreme environments.

Devitrification  Crystallisation of a formerly non-crystalline (amorphous) glass such that its ability to transmit a range of  electromagnetic radiation  (e.g. UV) is greatly reduced.

Dichroic  Describes materials with the property to selectively reflect or transmit a particular wavelength range. Dichroic UV reflectors that reflect less long wavelength radiation such as  IR  are called “cold mirrors” while those that reflect more are called “hot mirrors”.

Dielectric  An electrical insulator that can be polarised by an applied  electric field.

Dielectric Strength  The maximum  electric field  a material can withstand intrinsically before it breaks down and becomes a conductor of electricity.

Discharge Tube  / UV Lamp  Is a lamp envelope containing electrodes, a starting gas that is ionised by an electric field and other additives. The additive atoms / ions are  excited  to high energies and emit a UV photon as they return to their  ground state.

Doped Lamp  Also known in the industry as a metal halide lamp, contains an additive, such as gallium or iron, to alter the spectral output in order to cure different types of inks / coatings / adhesives.

Electric Arc  An electric current involving an ionised gas, such as argon, leading to the formation of a plasma arc.

Electric field  In simple cases, the electric field between two points is the voltage between those points divided by the distance between them.

Electrical Ballast  / Choke  / Transformer A device to prevent excess  current into a lamp and can also assist in  lamp ignition.

Electromagnetic Spectrum / Radiation  The entire range of all possible  electromagnetic radiation. This includes gamma rays, X-rays,  ultraviolet, visible light, infra-red, microwaves and radio waves.

Elemental (Metallic) Mercury  Is one of the three chemical forms of mercury,  which usually causing health effects  when inhaled  in vapour form. Exposures can occur when elemental mercury is spilled or products that contain elemental mercury break and expose mercury to the air, particularly in warm or poorly-ventilated indoor spaces.

Ground State  The lowest energy state of an electron.

Halogen  Chemical elements in Group XVII of the periodic table, including fluorine, chlorine, bromine, iodine and astatine.

Infra-Red (IR)The band of the  electromagnetic spectrum  ranging between 750nm to 1mm.

Isopropyl (Isopropanol) Alcohol  A colourless and relatively non-toxic alcohol. It evaporates quickly and can dissolve various oils, so is useful for cleaning quartz cooling tubes, UV reflectors and UV lamp bodies.

Metal Halide  A chemical compound involving a metal and a  halogen.

Methylmercury  An organic mercury compound formed through microbial activity when mercury is introduced to a water supply. This is harmful  to aquatic wildlife and animals (including humans) that ingest them.

Molybdenum  A silvery metal with the chemical symbol Mo and atomic number 42. It has the  sixth-highest  melting point  of any element. It is frequently used for making steel alloys as well as in the seal for UV lamps due to its relatively low thermal expansion and high electrical conductivity.

Nanometre (nm)  A term used in industry to measure specific wavelengths of the electromagnetic radiation spectrum – One billionth of a metre, 1 millimetre = 1000th of a metre, 1 micrometre = 1000th of a millimetre, 1 nanometre = 1000th of a micrometre  One billionth of a metre, 1 millimetre = 1000th of a metre, 1 micrometre = 1000th of a millimetre, 1 nanometre = 1000th of a micrometre

Noble Gases  Chemical elements in Group XVIII of the periodic table with similar properties such as being odourless, colourless and of low reactivity. This includes helium, neon, argon, krypton, xenon and radon.

Photo-Initiator  A compound that undergoes chemical reaction(s) when subjected to  electromagnetic radiation.

Photopolymerisation  Is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.

Phototherapy  the use of UV light in the treatment of physical or mental illness.

Photochemotherapy  Also known as PUVA is the use of UV light in the treatment of cancer.

PUVA  stands for psoralen (P) and ultraviolet A (UVA) therapy. This is a UV Light therapy  used to treat skin contritions such as eczema and vitiligo.

Quartz  A glass-like material made of silicon dioxide (SiOâ‚‚) with various different forms. It has low thermal expansion and a very high melting point of around 1665 °C.  The 'fused quartz' form transmits UV very effectively.

Spectral Enhancement  Moving  the electromagnetic radiation  output of the UV lamp, by doping with certain additives. This may include increasing the intensity of the radiation, or shifting  the range of  wavelengths (nm) of the radiation.

Thin Layer Chromatography (TLC)  A process involving UV light which chemists use to  identify the components in a mixture.

Transformer  An electrical device used to step-up or step-down the voltage of alternating currents.

Tungsten  Is a  chemical element  with the chemical symbol  W  and  atomic number  74. Tungsten and its alloys are used in numerous applications such as  light bulb  filaments, and it is used to make UV lamp electrodes owing to  having the  highest boiling point of any metal.

Tungsten Electrodes  A conductor through which electricity enters a UV lamp.

UVA  Also known as “Longwave UV”. UVA has a wavelength range of  400 — 315  nm. It is  the least harmful of the three UV wavelengths but can still  contribute to the ageing of skin, DNA damage and possibly skin cancer. UVA  lamps are used for curing of inks, adhesives and coatings and specifically;  screen printing and flexo printing.

UVB  Also known as “Midwave UV” or “Medium Wave UV”. UVB has a wavelength range of 315 – 280 nm. It is  more dangerous than UVA and is responsible for burning the skin among other things. In industry UVB lamps are used for curing of inks, adhesives and coatings and specifically clear coatings and thin ink layers.

UVC  Also known as “Shortwave UV”. UVC has a wavelength range of 280 – 100 nm. It  is the most harmful  and highest energy of the three UV wavelengths. In industry UVC is used for water and air disinfection as it can render micro-organisms harmless.

UV Coating  Refers to treatment of a substrate with UV radiation to cure the surface or protect the underlying material from its harmful effects.

UV Curing  Is a photochemical reaction (photopolymerisation) when specialised coatings are exposed to UV light they cure, instead of relying on heat and time to evaporate carriers like in solvent-based coatings.

Wavelength  A property of  electromagnetic radiation – by altering the wavelength (nm) you can cure / disinfect  various  types of substrates.

WEEE  The  Waste Electrical and Electronic Equipment Directive  (WEEE Directive) is the  European Community  directive 2002/96/EC on  waste electrical and electronic equipment  (WEEE).