Recent advancements in large language models (LLMs) have enabled their application across various domains. However, in the field of patent translation, Transformer encoder-decoder based models remain the standard approach, and the potential of LLMs for translation tasks has not been thoroughly explored. In this study, we conducted patent claim translation using an LLM fine-tuned with parallel data through continual pre-training and supervised fine-tuning, following the methodology proposed by Guo et al. (2024) and Kondo et al. (2024). Comparative evaluation against the Transformer encoder-decoder based translations revealed that the LLM achieved high scores for both BLEU and COMET. This demonstrated improvements in addressing issues such as omissions and repetitions. Nonetheless, hallucination errors, which were not observed in the traditional models, occurred in some cases and negatively affected the translation quality. This study highlights the promise of LLMs for patent translation while identifying the challenges that warrant further investigation.

This paper presents the submission of NTTSU for the constrained track of the English–Japanese and Japanese–Chinese at the WMT2025 general translation task.For each translation direction, we build translation models from a large language model by combining continual pretraining, supervised fine-tuning, and preference optimization based on the translation quality and adequacy.We finally generate translations via context-aware MBR decoding to maximize translation quality and document-level consistency.