Patent examiners are under increasing pressure to quickly and accurately evaluate incoming patent applications within large databases. For each incoming patent application, they first extract a subset of possibly relevant patents through keyword-based search queries. These results are summarized in long lists, which provide only minimal information on each patent. To immediately determine whether a patent is possibly relevant or not, each patent needs closer examination by opening it and scanning through its content, including drawings. For large result lists, this is a time consuming and strenuous job in the current user interface. In this work, we explore the applicability of novel information visualization techniques and the use of touch-based interactions. Our findings are included in the prototype application TouchPat, a touch-based zoomable user interface for exploring large patent collections. TouchPat provides an overview of a patent collection up to 1000 patents, and allows examiners to use multi-touch interactions to explore and process it. To summarize the information, each patent is visualized with a symbolic thumbnail representation. We use semantic zooming to adapt the amount of meta information for each zooming level and make optimal use of the available space. This thesis describes the design and development approach of the TouchPat prototype application, the individual visualization and interaction techniques used and its evaluation with the patent experts. TouchPat is well received with patent experts, and its user interface experience encourages further improvement in the speed and accuracy of the patent examination process.