Safety glass refers to tempered glass, laminated glass and other glass products processed by the combination of tempered glass or laminated glass in accordance with the current national standards, such as safety insulating glass, etc. Safety glass can be made of ordinary glass, tempered glass, heat-enhanced glass, and also insulating glass according to different needs. Safety glass has good security, impact resistance and penetration resistance, with anti-theft, explosion-proof, impact resistance and other functions. It is due to its excellent characteristics that safety glass is widely used in the field of special equipment. Such as sightseeing elevators, escalators and other equipment.
Safety glass is about the safety of life and property, China will be the first batch of safety glass into the implementation of 3C certification of the product catalog. 3C certification is known as "China Compulsory Product Certification", it is our government to protect the personal safety of consumers and national security, strengthen product quality management, in accordance with laws and regulations to implement a product qualification Evaluation system, is the product into the market pass, is the firewall of safety.
At present, the 3C certification mark is mainly applied by pad printing method, screen printing, etching method and other methods. Among them, the pad printing method of ink layer thin, poor physical resistance, printing area by the glue head, steel plate limitations, can not print a large area of products. And screen printing speed is low, can not print very fine patterns, ink pollution of the environment, the cost of supplies is high.
Laser marking is a widely used technology in the production process, using the appropriate energy density, converging on the surface of the workpiece laser beam on the target surface scanning, so that the material undergoes physical or chemical changes, the formation of traces on the surface, thus forming the marking process. It is a non-contact marking method, compared with traditional processing methods, has a wide range of applications, marking speed, stable performance, high quality, low operating costs, low environmental pollution, easy to use computer control and synchronous operation with other equipment, etc., therefore, laser marking has become one of the important application areas of laser.
Laser marking technology can be used for marking transparent materials, in the traditional transparent material marking, there are three main methods: ① using CO2 laser for direct marking, but the method of marking the contrast is not high, in light-colored material is difficult to identify; ② using green laser for direct marking, but the cost of green laser equipment is high; ③ using inkjet + infrared laser marking, the method of ink consumption is larger, the cost of ink supplies is also higher. Ink consumables cost is also higher, and there is a certain amount of pollution to the environment, and the mark is not resistant to corrosion and water.
Laser black marking is to be processed under the sample and placed on top of the graphite sheet, so that it remains closely connected, and then the laser will be focused on the interface between the two, marking. The processing mechanism is the intense ablation of the graphite sheet by the laser, and the instantaneous high temperature and pressure at the contact surface, which makes the graphite particles detach from the surface of the graphite target at high speed and attach to the glass surface to achieve black marking. This method can be used on transparent materials such as glass. This method can achieve good quality and high contrast black marking on transparent materials such as glass, and the marked marks are waterproof and corrosion resistant. In addition, the graphite can be used repeatedly compared to the traditional inkjet method, so the cost of consumables is low.
In this paper, we propose to apply laser black marking to the 3C marking of safety glass by using MOPA pulsed fiber laser to achieve black marking on safety glass.
1、Experimental materials and methods
1.1 Experimental materials
Safety glass, especially laminated glass and insulating glass made of laminated glass has the best comprehensive performance. Laminated glass is made of two or more pieces of glass bonded together with synthetic resin and made of a kind of safety glass. The original piece of laminated glass is mainly ordinary glass. The most commonly used organic material in the middle is PVB (polyvinyl butyral), but also methyl methacrylate, silicone, polyurethane and so on. When the outer glass is impacted by the rupture, the broken piece is glued, only the formation of radiation cracks, not due to fragmentation caused by personal injury or death. The structure of laminated glass is shown in Figure 2.
1.2 Experimental method
The processing equipment for this experiment is shown in Figure 3. IPG's YLPM series ytterbium-doped fiber laser is used as the light source. The scanning oscillator is a high-speed oscillator from SCANLAB, with a maximum speed of 100 rad/s and a maximum scanning speed of 2000 mm/s. The graphite sheet is fixed on the XY table. The glass is placed on top of the graphite sheet, and the lower surface is in close contact with the graphite sheet, and the laser beam is focused at the intersection. After the laser marking is completed, the glass can be easily separated from the graphite sheet.
Since there was powder around the glass after laser marking. Therefore, after the experiment, then use acetone solution, deionized water each in turn for ultrasonic cleaning, each cleaning time is 5min, and finally dry treatment.
2、Results and discussion
2.1 The mechanism and process of laser black marking
The process of laser black marking can be summarized as the following steps. First, the pulsed laser irradiates the graphite flake target, which rapidly vaporizes to form graphite particles and forms a plasma cloud due to the high temperature. Then, as the pulsed laser continues to irradiate, the plasma cloud rapidly explodes and continues to absorb the laser energy, which results in high local temperature and high pressure. Subsequently, due to the high pressure and high temperature in the local area and the rapid expansion of the plasma, the graphite particles detach from the graphite target surface at a very fast rate and adhere to the softened glass surface, which eventually forms a black mark on the glass surface after cooling.
2.2 Laser black marking application
Through the laser black marking method, the scanning path of the laser beam is controlled by the vibrating lens, which makes the scanning path of the laser beam more flexible and can be processed on the laminated glass with the required pattern mark. As shown in Figure 5, the 3C logo and the 2D code pattern are processed on the glass. From the figure, we can see that the pattern logo is very delicate and of good quality. The QR code pattern can provide the information of glass manufacturer, production time, glass model, etc. In addition, the required decorative patterns or text information can be processed on the glass _ according to the demand to improve the beauty of safety glass.
3、Conclusion
In this paper, by using laser black marking method, high contrast black marks and patterns are realized on safety glass. This technology has the advantages of high contrast, low cost, no pollution, high flexibility and high processing efficiency compared with the traditional marking application scheme, which provides a new solution to the problem of applying marks on safety glass of special equipment.
