How does toughened film have bubble removal

In this era of particularly fast pace of life, we hold our mobile phones every day, often accidentally break the mobile phone, then we will put a toughened film on the mobile phone, but in the film process we will find that there will be a small bubble, so how do we remove these bubbles?
With a hard card: First use a hard card or bank card to pry open a corner close to the bubble, the bubble will disappear after full contact with the air. Then press the uncovered toughened film forward slowly with the bank card so that the uncovered part can also contact with the phone screen and bond together. Finally, use the bank card to gently scratch the phone screen, so that the overall look is very neat and comfortable. Advantages are simple, easy to find tools. The disadvantage is easy to scratch the toughened film.