Currently, we are expected to shift economic, social, and industrial structures, which have depended on fossil fuels since the Industrial Revolution, into structures driven by clean energy through green transformation (GX). With the Paris Agreement of 2015, the world has been moving toward carbon neutrality. As pointed out by Sueyoshi and Goto (2019), Japan has historically faced various environmental problems, along with industrialization. Therefore, Japan has also made a “2050 Carbon Neutrality Declaration” in 2020. The declaration indicated that “the goal is to reduce overall greenhouse gas emissions to zero by 2050, that is, to achieve a carbon-neutral, decarbonized society in 2050”. The trend toward a decarbonized society has become irreversible in Japan. Most recently, based on the “GX Promotion Law” enacted in May of the previous year, the GX Promotion Strategy was approved by the Cabinet of Ministers, and all the moves toward GX are taking shape. The Green Transformation Technologies Inventory (GXTI), released by the JPO shows how various GX technologies can be categorized, and how patent documents related to each category of GX technology can be searched. GXTI helps enterprises and others to objectively explain their GX efforts. GXTI categorizes GX technologies and searches for patent documents pertinent to the five respective GX technology categories: energy supply; energy saving; electrification; demand-supply flexibility; batteries; energy storage; CO 2 reduction in the non-energy sector; and capture, storage, utilization, and removal of greenhouse gas.

On the other hand, patents are the most common method in the automotive industry to protect intellectual property ( Borgstedt et al., 2017), and patent analysis has been used to evaluate the competitiveness of firms, develop technology plans, prioritize research and development (R&D) investment, and monitor technological change in firms ( Yoon and Park, 2004). Japanese respondents also reported patents as being as effective as other mechanisms for protecting product innovation. Furthermore, patents are the most important channel of information flow in Japan ( Cohen et al., 2002). Although Jiang et al. (2022) have searched for “green” patents in the vehicle powertrains field, and Jiang et al. (2023) collected cited information about them, there have not been reports of research on GX patents, because of a delay in the development of a database, which is a void that we are trying to fill. We generated this dataset for GX patent applications of Japanese corporations and published GX patents in Mendeley Data, which is available to everyone. The full dataset may be used to conduct further searches, such as natural language analysis and machine learning, on patent description documents as well as statistical data analysis for empirical economics. This dataset may also be merged with many other databases such as the EPO’s PATSTAT database and the Corporate Social Responsibility Database of Toyo Keizai Inc. We expect our dataset to be meaningful for forecasting the development of new technologies and encouraging environmental innovation.

We generated this dataset by searching for GX patent applications of Japanese corporations on the Japan Platform for Patent Information (J-PlatPat). The search formulas are published at https://www.jpo.go.jp/e/resources/statistics/gxti.html and use a combined search strategy of International Patent Classification (IPC) codes and keywords. Applications of similar methods that have been previously reported include those of Jiang et al. (2022), the authors proposed a method of combining IPC and keywords to define “green” patents in vehicle powertrain systems, based on data of patent applications to the Japan Patent Office as recorded in EPO’s PATSTAT. ¹ Borgstedt et al. (2017) proposed a search strategy using IPC-classes and keywords is introduced that reveals all relevant patents and clearly differentiated four vehicle powertrain technologies. And Mirzadeh Phirouzabadi et al. (2020) introduced a database using a combined search strategy of keywords and IPC codes.

From the present search, we obtained 37,476 patent applications by 298 corporations during the period 1999–2022. When analyzing patents, it is necessary to consider the social situation of each country, including language background ( Jiang et al., 2022). Thus, since the names of Japanese corporates are written in both kanji and katakana, when we searched for one corporate’s patents, we searched in both kanji and katakana. ² The name list of corporations and their industry sectors was supplied by Toyo Keizai Inc., a leading business publisher in Japan, with the most well-known comprehensive database of Japanese companies. Most companies are listed in the first section of the Tokyo Stock Exchange Market ( Sueyoshi and Goto, 2019). Figure 1 aggregates the sampled patents by the industry sector.

From this figure, we can see that most GX patents were from the transportation equipment sector, there are 20,385 patents, account for 54%, and second-most common sector of GX patents was the electrical appliances sector, there are 6,290 patents, account for 17%. The number of GX patents from the metal products, Glass & Stone products, non-ferrous metals, and chemistry sectors was also over 1000. There are comparatively few GX patents from the retail, banking, securities, and commodity futures sectors.

Figure 2 shows the yearly number of GX patent applications for the period 1999–2022. As shown, the number increased every year until peaking in 2012, after which it remained relatively stable for several years and then decreased from 2019 because of a delay in opening in J-PlatPat.

Table 1 lists the top 10 companies in terms of the number of patents owned. As shown, in our sample, Toyota Motor Corporation owns the most GX patents (11,514), followed by Mitsubishi Electric Corporation (4,443), Honda Motor Co., Ltd. (4,011), and Nissan Motor Corporation (3,256), who also had numerous GX patents.