Abstract: Through a model of quality ladder, this paper analyses the effect of duopoly’s research behavior and patent-licensing behavior to subgame perfect Nash equilibrium in the cases of cumulative innovation and isolated innovation, then studies the relevant optimal patent breath on that basis. The results show that the optimal patent breath changes to reflect changes in research efficiency of market, regardless of the type of innovation. Compared with the isolated innovation, the optimal patent breath may narrower or wider, it depend on the change of research efficiency, so patent system of isolated innovation may not apply to cumulative innovation.

摘要： 本文通过一个质量梯模型，分别分析了孤立创新框架下和累积创新框架下双寡头厂商的研发行为和专利许可行为对子博弈精炼纳什均衡的影响，然后在此基础上分析了相关的最优专利宽度。结果表明，无论在何种创新框架下，最优专利宽度都随着市场研发效率的变化而改变。与孤立创新框架相比，累积创新框架下最优专利宽度可能较宽也可能较窄，主要取决于不同时期市场研发效率的变化，因此孤立创新框架下的专利制度可能并不适用于累积创新。

关键词: 专利许可, 专利宽度, 孤立创新, 累积创新, Patent-licensing, Patent Breath, Isolated Innovation, Cumulative Innovation