缺乏政策引导的低碳技术创新存在技术和环境的双重外部性,双重外部性严重抑制了企业的低碳技术创新活力。为探讨低碳发展和知识产权保护政策的实施是否有效缓解了低碳技术创新的双重外部性,以2007—2021年A股上市的高碳排企业及全国主要城市为样本,运用双重差分和三重差分方法进行了考察。研究发现:(1)低碳城市试点政策和知识产权示范城市政策在城市层面和企业层面均有效缓解了低碳技术创新的双重外部性,在克服了内生性及多重稳健性检验后该结论依然成立,进一步的异质性研究发现,两项政策对位于“胡焕庸线”以东、非国有、轻污染、初创型企业的低碳技术创新有更好的促进效果;(2)机制检验表明,低碳发展和知识产权保护政策分别通过提升企业环境注意力和创新注意力缓解了低碳技术创新双重外部性;(3)政策叠加作用检验结果显示,两项政策存在协同作用效果,且协同作用的成效大于政策各自独立的作用效果。本文的研究深化了低碳发展情境下的企业竞争理论,拓展了低碳技术创新外部性问题的研究边界,探索了多重政策协同效果的研究思路与方法,为未来相关政策体系的建构及完善提供了理论参考及经验证据。

Lack of policy guidance in low-carbon technology innovation poses dual externalities in terms of technology and environment, which severely inhibits the vitality of enterprises in low-carbon technology innovation. To explore whether the implementation of low-carbon development and intellectual property protection policies effectively alleviates the dual externalities of low-carbon technology innovation, this study examined a sample of high-carbon emission enterprises listed on A-share markets and major cities across China from 2007 to 2021, by using the Difference-in-Differences (DID) and difference-in-differences-in-differences (DDD) methods. The findings are as follows: (1) Both the low-carbon city pilot policy and the intellectual property demonstration city policy effectively alleviate the dual externalities of low-carbon technology innovation at both the city and enterprise levels. This conclusion remains valid after addressing endogeneity and undergoing multiple robustness tests. Further heterogeneity studies revealed that these two policies have a better effect on promoting low-carbon technology innovation in enterprises located east of the "Hu Line", non-state-owned enterprises, lightly polluting enterprises, and startups. (2) The mechanism tests indicated that low-carbon development and intellectual property protection policies alleviate the dual externalities of low-carbon technology innovation by enhancing enterprises' environmental attention and innovation attention, respectively. (3) The results of policy interaction tests showed that there is a synergistic effect between the two policies, and the effectiveness of this synergy is greater than the individual effects of each policy. This research will deepen the understanding of enterprise competition theory in the context of low-carbon development, expand the research boundaries of externality issues in low-carbon technology innovation, explore the research ideas and methods for the synergistic effects of multiple policies, and provide theoretical references and empirical evidence for the construction and improvement of relevant policy systems in the future.