This paper highlights concerns about the overlapping of copyright and trademark rights, and their potential to undermine the intended limited duration of copyright protections. Martin Senftleben, the author of the paper, argues that the practice of combining copyright and trademark protection has become common – especially in character merchandising. An example given is Mickey Mouse, where not only the name but also several drawings are registered as trademarks, which allows Disney to extend certain protections beyond the expiration of the original copyright.
Senftleben argues that this creates a “corrosive effect” in that trademarks can be used to continue protecting cultural expressions well after the copyright has expired. This prevents these works from fully entering the public domain, and hinders cultural remix and reuse since trademark infringement claims can be used to control use and interpretation. The analysis in the paper focuses on the resulting impoverishment of the public domain after the expiration of copyright, and offers proposals aimed at mitigating the impact of trademark rights to ensure they do not overly restrict other expressions post-copyright expiry.

See paper here https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4689838