at present，The commonly used method for producing vacuum collector tubes in China is still multi-layer aluminum-nitrogen/Manufacturing technology of aluminum solar selective absorption coating。This technology was developed by Professor Yin Zhiqiang and his colleagues at Tsinghua University1984Annual Invention，1985Annual application for national patents，1987Approved annually（Patent number：ZL851001424）。

　　The basic principle of this technology is inside the coating machine，Setting up a magnetron sputtering system for a single cylindrical aluminum target。Loading dozens of glass tubes into the coating machine as inner tubes for heat collection tubes at once，stay“planet”Under the transmission of the mechanism，Glass tubes undergo revolution and rotation。Vertical cylindrical aluminum target at the center position，Non reactive sputtering deposition of aluminum substrate in argon gas，Inject nitrogen with controllable flow rate again，Preparation of multi-layer aluminum—Nitrogen composite film material as absorption layer。

　　This is called gradient aluminum-nitrogen、Manufacturing Technology of Aluminum Solar Selective Absorption Coating，Its solar absorption ratio can reach0。93，Launch ratio0。05（80℃）。This is the first time in the world that only one metal material has been used，Selective absorption coatings for both metal substrates and composite thin film materials。Tsinghua Sunshine Company uses this technology to produce the Sun Le brand Purple Gold series vacuum collector tubes，Tested by the National Light Industry Glass Product Quality Supervision and Testing Center，Its solar absorption ratioα=0。95（AM1。5）；Hemispherical emissivity ratioεh= 0。050（80℃±5℃）。