The development of modern car appearance is closely related to the development of glass technology. As early as more than 40 years ago, the front windshield of cars had adopted a single-piece curved windshield, and the flat windshield was gradually abandoned. Today's car windshields are generally made into a large curved surface with a certain curvature up, down, left and right. This kind of curved glass is a product with very high technical requirements, both in terms of processing and assembly, because it involves many issues such as vehicle type, strength, heat insulation, and assembly.
Car windshields use curved glass, first from the perspective of aerodynamics. Because the normal speed of modern cars mostly exceeds 100 kilometers per hour, the oncoming airflow flowing through the curved glass can reduce eddies and turbulence, thereby reducing air resistance. Coupled with the smooth transition between the edge of the window frame and the surface of the car body, the glass and the car body are integrated into one, visually not only feeling the overall coordination and beauty, but also reducing the wind resistance coefficient of the entire vehicle. In addition, curved glass has high strength and can use thinner glass, which is of certain significance for lightweighting cars.
The curved windshield of modern cars must have a high flatness at the curved corners without optical distortion. The objects outside will not be deformed or dazzled when viewed from any angle on the driver's seat. . In the past, car glass was usually decorated or protected with neat strips along the edge of the glass. Now the glass on cars uses ceramic glaze, the so-called "black border." Many car windshields are also coated, using a reflective coating process or improving the composition of the glass, allowing only the visible light of the sun to enter the cabin and blocking ultraviolet and infrared rays, which greatly reduces the heat suffering of the occupants. This kind of modern car glass, called "green glass", has been widely used.
The safety performance of car windshields is very important. Not to mention the danger to the body of the occupants if the safety performance is low, it is also harmful to the car itself. If the windshield has cracks or obvious shelter spots, it will be like a disfigured face, seriously damaging the appearance of the entire vehicle. Therefore, the safety requirements for car windshields must be very high. General automotive glass uses silica glass, the main component of which is silicon oxide, with a content of more than 70%, and the rest is composed of sodium oxide, calcium oxide, magnesium, etc., and is made through the float process. During the production process, the material melts when heated to a temperature of 1500°C. The solution is poured into the suspension tank (liquid tin) when passing through the refining zone at about 1300°C, and is cooled to about 600°C. At this stage, two parallel sides of particularly good quality are formed. The planar body (the upper surface is the solution plane and the lower surface is the upper surface of the liquid tin), passes through the cooling zone to form glass and is cut into specified sizes. The glass is then further processed into tempered glass (TSG) or laminated glass (LSG).
The finished product automotive glass should have no obvious bubbles or scratches in appearance. In order to ensure the quality of automotive glass, the industry divides automotive glass into four categories according to process processing: Class A and Class B laminated glass, regional tempered glass and tempered glass. Among them, Class A laminated glass has the highest safety performance. National standards stipulate that the front windshield must use Class A laminated glass, Class B laminated glass or regional tempered glass. Their codes in the certification marks are LA, LB, and Z. The certification marks are screen printed, sandblasted, etc. The process is permanently marked on the lower corner of the glass. The code for tempered glass is T, which can only be used in positions other than the front windshield. Glass with LA, LB, and Z marks can be applied to all glass positions in the car.
With the development of automotive glass technology, new windshield technologies are also emerging. For example, it can reduce the impact of sunlight on the interior of a car and improve the level of comfort. The currently widely used "green glass" uses a reflective coating process or improves the composition of the glass to allow only the visible light in the sun to enter the cabin and block ultraviolet and infrared rays. There is currently a kind of anti-infrared radiation silver film glass, which adds a silver-coated film to multiple pieces of laminated glass, and its infrared reflectivity is 48%. When sunlight passes through this seemingly ordinary glass, light and heat are reduced by 23%. This kind of glass actually plays the role of heat insulation and energy saving, which can relatively reduce air conditioning energy loss. In addition, car windshields in cold northern areas are prone to fogging and freezing. A heated car glass can solve this problem. In this kind of glass, extremely small and almost invisible electric heating wires are made into a wave shape and placed on the plastic mucosa in the laminated glass, and are connected to the circuit through resistors. The car window heating wire has a certain heating range and the thermal power can reach 3-5 watts/cm2, which plays the role of anti-frost, anti-fogging and anti-icing.