Abstract:     With the shortening of product life cycle, the increasing degree of technical complexity and the speed of knowledge upgrading, enterprises carry out extensive and in-depth cross-boundary external searches, identifying, acquiring, transforming and integrating knowledge from external knowledge sources has become an important means of improving innovation performance. Enterprises′ openness is an important factor affecting innovation performance. However, collaboration with external partners during the entire innovation process also significantly increases the risk of being imitated. The risk of imitation is more serious for companies participating in R&D collaboration, which may trigger the "open paradox". And the risks associated with the "open paradox" run through the entire innovation process. Although there is broad consensus on the positive role of external search in promoting innovation performance, there are still some unresolved issues regarding the appropriability strategy of enterprises cross-boundary and the way of external collaborative innovation management. It is needed to explore the use of formal and informal appropriability mechanisms at all phases of the innovation phase, and collaboration and appropriability strategies with different types of partners also require further research.
    Although scholars have studied the intricate relationship between openness and appropriability, so far, there have been few studies empirically explored the relationship between openness, appropriability and performance. Therefore, this study focuses on the impact of three different types of appropriability mechanisms: formal (patents, trademarks, designs and copyrights), semi-formal (contracts and trade-secrets) and informal (lead times and products complexity), and openness (in terms of collaboration depth with eight types of partners) on the two different types of innovation performance, such as efficiency and novelty, at different phases of the innovation funnel. This study aims to analyze the impact of appropriability mechanism and openness on innovation performance at different phases of the innovation funnel based on the theory of boundary-spanning search and protection of intellectual property rights, through the questionnaire survey data of 332 manufacturing companies from Guangdong province.
     The conclusions of this study are as follows: (1) In the creative phase of the innovation funnel, innovation efficiency is positively related to the use of semi-formal appropriability mechanisms (contracts and trade-secrets), but negatively related to the use of formal appropriability mechanisms, such as patents. Innovation novelty is positively related to the use of informal appropriability mechanisms, and positively related to openness to companies in other industries and universities  too; (2) In NPD and commercialization phase of the innovation funnel, openness to innovation intermediaries and consulting companies is related to innovation efficiency, and innovation novelty is negatively related to openness to suppliers; (3) In all phases of the innovation funnel, innovation efficiency is related to openness to customers, while innovation novelty is positively affected by openness to competitors and other industry companies. 
    The theoretical contribution of this study is as follows: (1) this is the first study to explore the relationship between appropriability mechanisms, openness, and innovation performance within the same framework, and to further analyze the appropriability mechanisms used at different phases of open innovation, has been clear about the different impacts of appropriability mechanisms at different phases on innovation performance, to help in the field of collaborative innovation research perspectives from general open innovation to the different phases of open innovation, reveal and prove the existence of differences effects of appropriability mechanisms at the different phases of open innovation, will help to deepen the study of open innovation, for the further exploration of the appropriability mechanisms of the entire phases of collaborative innovation in the future provides a new perspective. (2) the study introduced the knowledge protection theory, to distinguish three forms of appropriability mechanisms in collaborative innovation: formal (patents, trademarks, designs and copyrights), semi-formal (contracts and trade-secrets) and informal (lead times and products complexity),revealed the different protection mechanisms of intellectual property rights for collaborative innovation, and deepen the knowledge protection theory in the concrete application in the field of collaborative innovation, expand the theory of innovation appropriability research. (3) this study reveals the formal, semi-formal, and informal appropriability mechanisms at different phases of open innovation on collaborative innovation performance of the specific mechanism, for the appropriability mechanisms on innovation performance effect research provides new theoretical explanation, which deconstructs the open innovation from the theory level the appropriability mechanisms affect the black box of the performance of collaborative innovation, expand the connotation of the theory of open innovation.
      The management implications of this study are as follows: (1) when the enterprise adopting open innovation determines the impact of openness on different types of partners and the use of appropriability mechanisms on the innovation performance, it must distinguish each phase of the innovation funnel. In the creative phase, the use of all types of appropriability mechanisms and the openness of certain horizontal partners can have a significant impact on performance, while in NPD and commercialization phase, horizontal and vertical partners and informal appropriability mechanisms can affect innovation performance. The relationship between all appropriability mechanisms and innovation performance is stronger in the creative phase than in NPD and commercialization phase. In addition, the contrasting effect of formal appropriability mechanisms and semi-formal appropriability mechanisms on innovation efficiency has practical significance related to the so-called ‘open paradox’. (2) the contrasting effect of using formal and semi-formal appropriability mechanisms on innovation efficiency may also have an impact on the cost aspects of appropriability strategies. Although strong formal appropriability mechanisms may be required in the creative phase of the open innovation process, at the same time, the knowledge contained in new products or processes may be difficult to obtain patents in the creative phase, as this is not the case. As a result, the costs may outweigh the benefits when enterprises invest in a formal appropriability mechanisms, such as a patent, in the creative phase of open innovation. Therefore, managers should carefully choose expensive formal appropriability mechanisms to protect knowledge in the creative phase of collaborative innovation, and consider choosing semi-formal appropriability mechanisms such as contracts and trade-secrets.

Key words:  openness, appropriability mechanism, innovation performance, innovation funnel