Just as there will be natural monopoly in some industries, the emergence of patent rights is also based on the particularity of the industry. Patent rights are generally limited to 15 years, which is a compromise. If patents are not protected, new achievements will be imitated by other enterprises, and enterprises committed to innovation will invest in vain, and the industry will have no incentive to innovate. A long-term patent right will lead to monopoly. Therefore, patents have a time limit, so that innovative enterprises can obtain excess profits within the time limit.