According to the ROC Patent Act, a purely functional design applied to an article is not patentable subject matter for a design patent. However, if some of the features disclosed by the drawings of a design patent are functional features, should the functional features be taken as part of the basis for comparison with prior art in determination of whether the functional design also contributes novelty or creativeness to the design or for comparison with a product that is accused of infringing the design patent in determination of whether the accused product adopts the same or similar design and thus constitutes infringement?
The key to the above issue is, according to the Patent Act, to determine whether the "functional feature" is a "purely functional feature." In other words, even though the feature can perform a certain function, it is still not a purely functional feature, and thus should be included among the design features which serve as the basis for determining novelty and/or creativeness of the design patent or for comparison with suspected product for infringement assessment purpose, as long as the designer to some extent, has room to decide the design by selection from different shapes and/or arrangements (of patterns or the like) to create a different visual effect. (IP Court Judgment No. 104-Administrative-Patent-Suit-32 holds the same.) The recent court practice further adopts the criterion "whether the questioned functional design feature has a unique visual effect relative to conventional art (which is not necessarily a cited prior art reference)."
For instance, IP Court Judgment No. 106-Civil-Patent-Appeal-Yi-1 rendered on 28 September 2017 holds: "though the inlet and the outlet elements of the engine cooling tank are set for its functional purpose, the arrangement of the element locations and the number of the elements can be decided or re-arranged through design to create visual effects. (Note: the court is also of the opinion that the inlet, the outlet and the fluid entrance structure occupy a large portion of the whole tank in appearance.) They need to be included in the materials in determining patent infringement and patent validity. As to the threaded hole and the fastener (i.e., a polygonal nut), they are nothing but conventional art and come from a "must-fit" design, so they are purely functional and shall not serve to determine the claim scope." IP Court Judgment No. 104-Administrative-Patent-Suit-115 rendered on 15 July 2016 states: "the shapes of the teeth of the gear, regardless of whether the teeth look like the teeth of a spur gear or a bevel gear, are general selection from conventional mechanical art and cannot create sufficient visual effects...the chamfer of the teeth is to reduce friction in rotation, which is conventional art and functional; it creates no visual effect on the whole appearance."
It is worth noting that in the two cases, it is not necessarily the case that any disclosure in the cited or submitted references that is the same as or similar to the functional feature in question leads to the conclusion that the feature is purely functional. Rather, it is based on the judge's (or the patent examiner's) knowledge or understanding of conventional art; if the functional feature is considered to have no unique visual effect relative to the conventional art, it will not be deemed meaningful in determination of the claim scope. Though the source of the judge's or examiner's knowledge or understanding of conventional art could be previous exposure to various prior art documents (not necessarily from the case pending before them), from the position of a patentee or design patent applicant, it is advisable to collect and voluntarily submit objective evidence (such as books or documents relating to conventional art) to explain how the design is different from conventional art in shape or arrangement of elements and what unique visual effect is created in order to obtain a favorable judgment.