This is due to the special structure of tempered glass. Whether it is physical tempered glass or chemically tempered glass, a stress layer is formed on the surface of the glass, and a tensile stress layer is formed inside. You can simply think of it as a sandwich cookie. When subjected to impact, the outer stress layer and the internal crack conduction velocity are different. Generally, the stress layer of the physical tempered glass is 1/23 of the internal tensile stress layer, and the chemically tempered glass stress layer is the internal tensile stress layer. 1/11 , and the crack propagation velocity on the surface and inside of ordinary glass is 1 , therefore, the stress layer outside the tempered glass has not spread far, and the layer inside has spread far. Just like the sandwich biscuit was shocked, the inside of the sandwich had cracked, and the biscuits outside were not much worse. Due to the presence of the stress layer, the impact force is mostly propagated internally. Because the tempered glass is high in strength, it is generally sufficient to allow the crack to propagate inside. If the impact is too large, it will break into small particles.