Pearlescent pigment is a kind of gloss pigment: non-toxic, tasteless, acid and alkali resistant, non flammable, non explosive, non-conductive, non migrating, easy to disperse, with high heat resistance and weather resistance, which fully meets the strict requirements of environmental protection. Pearlescent pigment not only has the flashing effect of metal pigment, but also can produce the soft color of natural pearl. Its flashing effect is passive luminescence, that is to say, it will show the flashing effect under the condition of receiving light.
The main types of pearlescent pigments are: natural fish scale pearlescent pigment, bismuth oxychloride crystalline pearlescent pigment and mica coated pearlescent pigment. At present, pearlescent pigments produced and widely used in the world take natural mica flakes as the core (the size of mica is from 4um to 120um and the thickness is about 0.5um), and one or more layers of titanium or other metal oxides are coated on its surface through special chemical process.
The mica sheet coated with metal oxide is very smooth, so it has good light reflection performance and transparency, that is, only part of the light is reflected, and the transmitted light passes through the mica sheet to another layer, which can continue to be shot, resulting in multiple reflections on many layers. It is difficult for the eye to focus on a certain layer, which establishes the depth of light reflection. So you can see a wonderful deep shiny luster, which we call "pearlescent".
Flat sheet crystal should be the basic structural form of pearlescent pigment. Only in this way can the pearlescent luster be strongly reflected like a lens. The diameter thickness ratio of flat sheet crystal is preferably about 200, and the materials meeting this condition are very rare. The higher the degree of parallel orientation of flake pigments, the more obvious the pearlescent luster effect,
The pearlescent effect can be determined by the thickness of titanium dioxide coating. White pearlescent is formed by the reflection of the thinnest titanium dioxide layer. With the increase of coating thickness, the reflected light is white, yellow, gold, red, blue and green respectively.
In addition to its own color, iron oxide coating also has the above properties. Bronze color is formed by yellow absorbed by ferric oxide, while interference yellow is produced by the thickness of ferric oxide. Using the same principle, red copper and red can be obtained.
The color of pearlescent pigment is related to the base color. On the white substrate, the transmitted light can be seen at any angle, and the color is not obvious. If on a black or dark substrate, the transmitted light is absorbed by the substrate, and the interference color will be strong at the reflection angle.
Pearlescent pigments reflect light according to the mirror effect, so the interference color can be seen at the reflection angle, while the complementary color of the interference color can still be seen in the scattering angle direction because the light passes through the thin layer. For example, an interference red pearlescent pigment can be seen red at the reflection angle and green at the scattering angle. White pearlescent pigment is white at the reflection angle, and the color of substrate or colorant will be revealed at the scattering angle.
The three-dimensional effect of pearlescent pigment is different from that of metallic pigment due to its different angle and color. Commonly used metal pigments such as aluminum silver powder are opaque. Light cannot be transmitted. All light is reflected on the surface like a mirror, so it does not have the three-dimensional depth effect of multi-layer reflection of pearlescent pigment. When a light absorbing pigment is added to the pearlescent pigment, because the pearlescent pigment itself is transparent, the light is allowed to penetrate and reach the light absorbing pigment and then be reflected, and the color of the light absorbing pigment is strengthened and brighter. If the light absorbing pigment is added to the metal pigment, because the metal pigment itself is opaque, the light cannot pass through the metal sheet and reach the pigment, so the color is weakened. For example, aluminum powder itself is gray, so the color of light absorbing pigment becomes dull gray, just like mud.
Metallic pigments are similar to pearlescent pigments in shape and size. According to the mirror principle, the light is reflected, that is, the light is incident at an angle of 45 degrees and then reflected at an angle of 45 degrees. The observation angle increases, the reflected light weakens and the color darkens. When you observe the pigment coating from different angles, the color changes only in depth, not in different colors like pearlescent pigment.
Pearlescent pigments cannot be mixed with conventional opaque pigments, such as chromium, cadmium pigments and titanium dioxide. Ordinary metal pigments and ordinary iron oxide pigments are light scattering pigments. Their addition interferes with the light refraction of pearlescent pigments and reduces their pearlescent effect due to light scattering. Organic pigments with transparency and low hiding power, such as phthalocyanine blue and phthalocyanine green, are mixed with pearlescent pigments, and their pearlescent effect is good. Other organic pigments with high transparency, such as sun resistant bright red, quiridone and YONGGU violet, are used with pearlescent pigments, and their effect is also good. Hongrun pigments: 3132 scarlet powder, sun resistant scarlet BBN, sun resistant scarlet BBC, golden red C, sun resistant scarlet 2bp, lisol magenta 4bp, lisol treasure red BK, YONGGU red f3rk, YONGGU red f5rk, pigment red 122, Pigment Red 254, organic medium yellow, organic lemon yellow, sun resistant yellow G, YONGGU yellow 2G, YONGGU yellow HR, pigment yellow 81, pigment yellow 110, pigment yellow 139, pigment yellow 151, pigment yellow 180 YONGGU orange yellow G, pigment orange 64, phthalocyanine blue BGS, phthalocyanine green G, Pigment Violet 19, YONGGU violet RL and other organic pigments. Carbon black and ultramarine are special inorganic pigments. Although they are opaque and have high hiding power, they can absorb all transmitted light and strengthen the reflected light. Therefore, they can also be mixed with pearlescent pigments. And produce a bright additional color effect.
As a special effect pigment, pearlescent pigment has been more and more used in many industrial fields because of its unique and elegant luster and soft or flickering appearance effects caused by different colors and particle sizes.