1、 The origin of glass beads as reflective materials
Glass beads have been used as reflective materials for decades. In 1950, Dr. Dong Qifang, a Chinese American scientist, developed Directional Glass Beads, and then developed a series of reflective materials such as reflective cloth. Nowadays, these reflective materials are widely used in traffic signs and safety signs.
In the early stage, due to the weakness of basic industries such as chemical industry, there was no way to solve the problem of raw materials such as special coatings and glass beads, and there was no fixed production equipment, which limited the industrialization process of reflective materials under certain conditions. In the 1990s, great progress has been made in the reflective materials with micro beads, such as advertising grade reflective film, engineering grade reflective film and high strength reflective film. Meanwhile, reflective cloth, reflective leather, reflective fusing and reflective thermal film are also introduced. By the end of 1990s, glass bead reflective products were basically mature in China.
2、 Principle of glass bead as reflective material
The reflective material made of glass beads can reflect the light from all directions back to the origin, which is the highest reflective material in the world. The reflective performance is greater than 400cpl, and the maximum reflective performance is greater than 1000col. It has the excellent performance of high reflectivity, strong weather resistance and large reflective angle.
Glass bead reflective material is based on the principle of micro prism reflection. We all know that the reflection of light has diffuse reflection and specular reflection. Why can the retro reflective material return the light according to its original path? In fact, this is mainly due to the high refractive index glass beads contained in them. When a beam of light irradiates the front surface of the micro bead at any angle within a certain range, due to the high refraction of the micro bead, it concentrates on the reflection layer on the back surface of the micro bead. The reflection layer reflects the light back parallel to the direction of the incident light, forming a regression reflection. When many glass beads reflect at the same time, there will be a bright scene ahead.
The experimental results show that when the refractive index of the glass bead is close to 1.9, the incident light can focus on the back surface of the glass bead, and the regression reflection effect is the best. When the refractive index is less than ｏｒ greater than 1.9, the incident line will focus on the outside and inside of the glass microsphere, and the regression reflection effect will be reduced The refractive index of glass beads is usually between 1.9 and 2.1, and its diameter is usually less than 0.8 mm. If a reflective layer is added behind the glass beads, the effect of regression reflection is better.
3、 Production principle and application field
How to produce such magic glass beads The production process is as follows: firstly, the raw materials are melted into liquid glass at a very high temperature. The liquid glass passes through a special nozzle to form many fog like droplets. These droplets automatically form regular spheres under the action of surface tension. After cooling, they are treated to obtain glass beads with particle size distribution between 10-200 microns.
Glass beads can be used to make many retroreflective materials, such as luminous cloth, reflective coating, reflective ink and so on. These materials are widely used in public security, transportation, fire control, railway, coal mine and other departments. They can be seen in labor protection products and civil products. Drivers who drive at night are likely to cause traffic accidents due to the influence of vehicle lights, roadside lights, high-rise searchlights and neon advertising lights. The bright light emitted by the reflective material sign board under the illumination of the lamp is particularly eye-catching, which can remind the driver to pay attention to the relevant road information and improve the driving safety. In rain, fog, sand and other low visibility weather, reflective materials can highlight its value. Therefore, many developed countries stipulate that the road and railway traffic signs must use reflective materials before and after the body. The international maritime life-saving agency also stipulates that life-saving equipment must be equipped with reflective materials to facilitate search and rescue work at night. Now many companies use reflective materials to decorate their products, so that on the basis of beauty and practicality, it also increases the safety function.
Glass beads, a magical reflective material, bring us many conveniences in our production and life, and there are many places for us to develop and explore.