Luminous paint

As luminous paint denotes a coating that emits more visible light than is incident from the outside, ie more than by directed or diffuse reflection as would be possible with reflectors. Fluorescent colors are dyed with fluorescent pigments.

The required energy can be provided on the basis of different physical principles:

• Fluorescent paint converts invisible UV light into visible light
• Phosphorescent stores energy, which has been incorporated in the light, and outputs it with a time delay again
• Radioactive luminous color, in which the energy directly or indirectly derived from the radioactive decay of a substance

Fluorescent colors

Fluorescent colors ( neon colors ) walk by the blue fluorescence and near-UV region of the daylight in light of longer wavelength (typically cyan, yellow and red ) around. Yellow and red is much brighter perceived by the eye at the same light intensity (V- lambda curve of the sense of sight ). This (higher proportion of blue in daylight ) is achieved a significant increase in contrast especially in cloudy weather and at dusk. Fluorescent colors are used as signal colors, such as high visibility vests or warning surfaces on emergency vehicles of the emergency services.

Afterglow

Phosphorescent (but not " night colors' ) store incident light in the form of excitation energy ( phosphorescence) and give this a time delay. Most consist of these colors in a reducing atmosphere annealed alkaline earth sulphides ( CaS, SrS or BaS ) with low foreign metal components, such as manganese.

Such phosphorescent inks are used for the marking of emergency exits and for various jewelry and decorative objects ( "Glow -in- the-dark " products ) are used.

Radioactive luminous colors

A radioactive luminous paint always consists of a radioactive substance, formerly mostly radium salt, until a few years later either a tritium compound or Promethiumsalz, and a fluorescent substance such as zinc sulfide. The radioactive radiation excites the fluorescent substance to this (luminescence ).

The fluorescent substances or other additional materials used are often of phosphorescence in the situation. Therefore - apart from Steady - to keep a strong, decreasing within seconds afterglow after exposure to light at first.

The direct radiation from the radioactive substances used today for light colors has, since only alpha emitters and low energy beta emitters are used in air has a range of only a few centimeters. A shield is already achieved by a transparent cover. However, out of neon colors a radiation hazard if it crumbles, because the radioactive substance can then be incorporated. Older watches luminescent hands, dials and scales contained partly radioactive substances with far reaching radiation. These represent particularly a danger, if the objects are constantly worn on the body.

Previously, especially the workers were at risk, the painted the dials, while the brush with the mouth anfeuchteten ( Radium Girls). Among these workers tongue and lower jaw cancer was a common occupational disease that eventually caused you to recognize the dangers of radiation.

In the second half of the 20th century, radioactive, radium -containing fluorescent paint was used on a large scale in the military to make switches and controls in the dark recognizable. In the early 2000s public health by military radar systems and have been studied fell in the same train also potential cancer by fluorescent colors in the German Army in the discussion.

Similar techniques

• Retroreflection (cats eyes, reflectors, reflector foil )
• Tritium gas light source - special light sources that shine for years without power supply