Stealth camouflage coatings are generally composed of film-forming substances, pigments, solvents and additives. The film-forming substance determines whether the camouflage can be firmly adhered to the camouflage target, and the camouflage pattern and color sprayed by different pigments are the key to achieve visible light stealth.
1. Film-forming substances
Alkyd resins and acrylic resins were generally used as the film-forming materials of coatings in the early days; such as the alkyd camouflage enamel paint in the United States, the air-drying matte camouflage paint in the United Kingdom, the F1 camouflage paint in France, and the C5350 air-drying alkyd camouflage paint in Sweden. (Equipped with the Swedish Army) and so on. With the development of material technology, in the late 1980s, it was developed to use polyurethane resin or acrylic polyurethane hybrid resin.For example, the United States, the United Kingdom, Canada and other countries have successively researched and developed chemical warfare agent-resistant aliphatic polyurethane camouflage coatings, and Western European countries are also common Using a three-color deformation camouflage paint made up of polyurethane and acrylate base materials plus brown, black and green pigments, the German T-72MG tank is coated with this three-color camouflage paint. This Western European three-color paint puts forward more reasonable classification and requirements for the types of camouflage colors, chromaticity coordinates and visible light and near-infrared brightness factors, which improves the camouflage performance, and the mechanical properties and use performance of the paint are also greatly improved. It satisfies the requirements of anti-toxic agent penetration and easy surface toxic agent cleaning, and represents the advanced level of today's optical camouflage coatings. The representative product of this type of optical camouflage coating is the chemical warfare agent resistant aliphatic urethane coating produced by Hentzen Chemical Coatings, USA.
2. Camouflage patterns and colors
The color of the camouflage paint pattern patch and the size of the patch are the keys to the effect of invisibility. The pigments suitable for visible light stealth are yellow, dark green, light green, brown, brown, black, chromium oxide green, carbazole violet, and iron oxide pigments. Due to the differences in the air, ground, and water battlefield environments, the camouflage patterns and colors used by the army, navy, and air force are also different. The ground equipment generally chooses green, brown, desert yellow, black and other camouflage patterns and colors that are similar to the battlefield environment such as woodland and desert. For example, Russia and some countries with rich forest resources in Europe mostly use jungle three-color or four-color camouflage paint with sawtooth and leaf-shaped stains, while Saudi Arabia and other Middle Eastern countries use three-color or six-color desert camouflage paint developed by the United States. Israel uses three-color desert camouflage of sandy yellow, visual color, and green, while the U.S. military uses both four-color jungle deformation camouflage and six-color desert camouflage paint.
The air force’s battlefield environment is the sky, and different camouflage colors are selected for different parts of the combat aircraft according to the difference in detection angles. The upper part of the aircraft: dark green, dark green, sky gray, medium blue, sea blue, etc. The lower part of the aircraft: sky gray, medium gray, matte white, milky white or light blue; engine tail nozzle: iron gold. For navy ships, the variegated camouflage such as the "dazzling camouflage" adopted by the United Kingdom and the United States during World War II is not ideal for the camouflage effect of ships, so all countries in the world now generally use gray monochrome painting . Because the observation angle of the detection system is multi-directional, including high altitude, water surface and underwater, the ship should also adopt slightly different color configurations in different parts. The light hull color of the ship is generally light gray, medium gray, and dark gray. The dark hull color is dark sea gray. For the hull below the waterline, the bottom red plate is deck yellow or deck gray. The pattern and color of the camouflage paint for individual camouflage uniforms are basically the same as those of combat equipment. However, the new digital camouflage introduced by the United States in 2002 has not yet seen reports of its use on combat equipment. The basic colors of the new digital camouflage are green, brown, brown and black, which are combined according to the specific application environment. Different from the traditional patch camouflage, what constitutes the new digital camouflage pattern is not the color patch, but the "pixel" point. At present, the United States has developed jungle digital camouflage and desert digital camouflage, and new gray digital patterns for urban environments are under development.
3. Visible light absorber (dye)
Visible light absorbers, also known as visible light absorbing dyes, are one of the functional dyes that have been studied more in the field of dye chemistry in recent years. Such dyes can be used as sensitizing dyes, photochromic compounds for erasable optical discs, secondary write optical storage materials, photosensitizers in photodynamic therapy, laser protection absorption dyes, and infrared absorption dyes for electronic phases, etc. It has a wide application market and huge application potential. At present, with the continuous expansion of laser applications in military and civilian fields, the demand for laser protection has become increasingly prominent. The laser protection wavelength is shifted from the traditional visible light region to the near-infrared light region. From the perspective of technical feasibility and economy, organic absorbing dyes are the main way to achieve wide-spectrum protection of near-infrared lasers. The current main technical requirements for this type of near-infrared laser protective dyes include: near-infrared (700~1400mm) broadband strong absorption (lge=≥4), no or weak absorption in the visible light region, good light, thermal and chemical stability, and Organic matrix materials have good compatibility and low toxic and side effects on the human body. In addition, this type of dye can also be used as near-infrared stealth materials, near-infrared laser absorbers and stealth materials.