Discussion on the most flaming interference color

Discussion on light interference color changing ink

light interference color changing ink (referred to as light changing ink, also known as optical color changing ink) is a new type of ink with dynamic color changing effect, which came out in the 1990s. The pictures and texts printed with it can change different colors from different perspectives. As a result, the universal tensile testing machine can not be carried out, especially when it is observed at about 0 ° and at about 60 °, it will show two very distinct colors. This discoloration effect comes from the light interference pigment in the ink

what is light interference pigment? This should start with the color of nature. As we all know, color is the photosensitive response of eyes and brain to the visible spectrum (wavelength range 400 ~ 700nm). When white light (such as natural light) shines on an object, we only feel the light of the reflected wavelength ("reflected color") on the surface of the object, and the other wavelengths are absorbed by the object and cannot be felt. The absorption and reflection of light waves by different objects are very different, so everything in the world has its own characteristics. "Reflected color" is determined by the internal characteristics of the object. No matter how the angle of observation and the direction of the light source change, the color of the object remains unchanged. "Interference color" on the contrary, it does not belong to the characteristics of the object itself, but is the color presented due to the physical effect of light interference. For example, soap bubbles do not absorb light and are colorless and transparent, but when their thickness meets the conditions of light interference, they will show rainbow like colors. "Interference color" can change color with the change of light incidence angle and observation angle, which can not be achieved by "reflection color"

light interference pigment is a masterpiece of human imitation of nature. Thin film optics, which is based on the principle of parallel plate multi beam interference, seeks high resolution of data acquisition and accelerates the construction of 8 South China Sea development equipment manufacturing and logistics support bases and oil and gas processing bases, which are the theoretical basis of artificial "interference color". Thin film optics realizes the human desire to control and select the reflection spectrum and optical properties of the object surface. Figure 1 is a schematic diagram of a multilayer optical film structure (the film thickness is in nanometers) (only the reflected light and related physical quantities related to us are discussed here, and the complex film calculation expressions are omitted). According to the thin film optical theory, the amplitude vectors of the reflected light of the incident light on the interface of each layer of thin film are R1 and r2e-2i respectively δ 1、…、rk＋1e－2i（ δ 1＋ δ 2＋…＋ δ k) Among them, R1, R2, A. improper adjustment of switch position: B. inside the control switch (poor contact or stuck moving parts)..., rk + 1 are the functions of refractive indexes N0 and N1, N1 and N2,..., NK + 1 and NK on both sides of the interface, called reflection coefficient. δ Is the phase difference between each reflected light: δ 1=2π/λ· N1d1cos θ 1、…、 δ k=2π/λ· Nkdkcos θ K where: λ Is the wavelength of incident light, D1 and DK are the thickness of the first film and K film respectively, θ 1、 θ K is the incident angle of light in the first layer and the k-th layer respectively（ θ 1、 θ 2、…、 θ K by θ 0 and N0, N1,..., NK)

the reflectivity r of multilayer optical films is the reflection coefficient R (i.e. N1,..., NK) and phase difference δ (i.e λ、θ 0 and D1,..., DK). Based on this, we analyze as follows:

① For a certain film system structure (designed and formed as required), the material n and thickness d of the film layer and the incident medium N0 are known constants, and its surface reflectance R is only the wavelength of the incident light λ And incident angle θ Function of 0. Given a θ 0, you can get that the membrane system is in this θ Reflection spectrum curve distributed by wavelength under the condition of 0. That is, each determined film system has a specific reflection spectrum. And the reflection spectrum will vary with the incident angle θ 0 changes. This is the reason why the "interference color" produced by the artificial film system can change color with the change of light incidence angle and observation angle

②. We can design the film system according to the needs, reasonably calculate the selected film material and film thickness, and change the values of N and D to achieve the predetermined reflection spectrum and optical performance indicators. Realize people's desire to control and select the reflection spectrum and optical properties of the object surface

light interference pigments are produced by grinding, grading, surface treatment and a series of pigmentation treatments of optical films with interference structure. It successfully utilizes the characteristics of optical thin films that can produce various dynamic interference colors. This unique flake pigment maintains all the optical properties of the optical film. As long as the observation angle is different from the incident angle of light, each piece of pigment will reflect colorful colors like a mirror. Accurate use of light interference technology can accurately control the change of color

optical thin films are formed by alternately depositing materials with different refractive indices on the same carrier under high vacuum according to the requirements of film structure. The material is evaporated to the carrier in the form of molecules or atoms. In order to ensure the uniformity and compactness of the film, the consistency of evaporation rate must be strictly controlled; In order to control the color index of the film system, the error of the film thickness must be controlled within angstrom (1 angstrom =10-1 nm =10-7 mm). This shows the precision and particularity of optical film production

on the premise that the film system design meets the spectral requirements, the number of film layers should be as few as possible to reduce the production cost. At present, the ideal light interference pigment film system is the five layer symmetrical structure shown in Figure 2. The thickness of the film system is about 1 micron. In the middle is an opaque reflecting layer (which can be regarded as the common substrate of the upper and lower interference cavities), and on both sides are symmetrical transparent colorless dielectric layers and translucent metal layers, so that the upper and lower sides of the film have the same interference color. Changing the thickness of the transparent medium layer can change the color of the film system to obtain various colors of light interference pigments. As the film system is made under high vacuum, all colorless or transparent inorganic materials are used. The generated light interference pigment has stable performance, compact structure, no fading, strong weather resistance, good shear resistance, and can be arbitrarily crushed according to the requirements of ink for particle size

at present, there are interference pigments made by using natural mica sheet and metal aluminum sheet as the substrate and chemical coating method in the world; There are also interference pigments made by using the characteristics of liquid crystal chips. However, it cannot be compared with light interference pigments in terms of color types and physical properties. They are mainly used in the coating industry, which is difficult to meet the stringent requirements of printing inks for sheet pigments

the dynamic discoloration effect of printing products with light variable ink cannot be copied with high-definition scanners, color copiers and other equipment; In addition, its design and production technology are highly professional; The manufacturing process is complex; Huge investment; It is difficult to copy, so it is used in currency anti-counterfeiting by more than 70 countries in the world. Since the 99 version of RMB 100 was used, the anti-counterfeiting mark has not been imitated on the counterfeit currency, and has become an important publicity mark to identify the true and false RMB in newspapers and periodicals. In addition, it can also be widely used in the anti-counterfeiting of all kinds of securities, famous trademarks, certificates, bills, product packaging and other printed materials

at present, only the United States can produce thin-film light interference pigments in the world, and only a few companies use American pigments to produce light change inks. Huizhou Huayang Optical Technology Co., Ltd. has successfully independently developed and mass produced light interference pigments and light change inks, and its products have reached the international advanced level. At present, it has been used in the anti-counterfeiting printing of many famous cigarette packages and important certificates. (Dazhe (Wuxi) Ink Co., Ltd.)