Obtaining sufficient competitive intelligence is a critical factor in helping business managers gain and maintain competitive advantages. Patent data is an important source of competitive intelligence that enterprises can use to gain a strategic advantage. Under existing approaches, to detect changes in patent trends, business managers must rely on comparing two patent analysis charts of different time periods, it requires human effort and time. In this paper, we propose a patent trend change mining (PTCM) technique that can identify changes in patent trends without the need for specialist knowledge. We apply the PTCM approach to Taiwan's semiconductor industry to discover changes in four types of patent trends: the R&D activities of a company, the R&D activities of the industry, company activities in the industry and industry activities generally. The change mining approach generates competitive intelligence to help managers develop appropriate business strategies based on their findings.