UV Glossary

A comprehensive list of UV industry related terms and their definitions;

Air deposition

The occurrence of airborne pollution (e.g. 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 specific 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

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 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 flowing 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

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.

Halogens

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. Mercury is harmful to aquatic wildlife and animals (including humans) that ingest it.

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 in the seal of 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

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

Psoralen (P) and ultraviolet A (UVA) therapy. This is a UV light therapy used to treat skin conditions such as eczema and vitiligo.

Quartz

A glass-like material made of silicon dioxide with various 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.

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).

Ozone Free UV Lamps

Lamps that do not produce any Ozone are manufactured using Ozone free quartz. This quartz transmits UV-A and UV-B, whilst blocking the high energy wavelengths that cause ozone generation, which pose a risk to humans. It is ideal for germicidal and curing applications and is best used when ozone extraction systems are not available.