The Japanese Patenting System


The Japanese patent system resembles the European patent system. However, there are some differences in patent numbering systems, and there have been recent changes to Japanese patent law.

Early Publication

Laid-open, unexamined Japanese patent applications (called 'Kokai') are published in Japanese 18 months after their earliest priority date. They are issued on a CD-ROM in mixed mode SGML-like format without search software. To access the information on disc you need:
(a) A subscription to the CD-ROM
(b) A computer with Japanese Windows
(c) Relevant search software.

This CD-ROM is issued twice weekly, and a total of approximately 350,000 kokai are issued every year. Derwent provides abstracts for all of these in the Derwent World Patents Index database. Full translations or machine-assisted translations are also available on request.

Kokai numbers start at zero every new year. A typical JPO unexamined patent issued in 1998 would have a number like this: h10123456A, where 'h' represents the emperor era Heisei, and the '10' header in the eight digit number represents the tenth year of the Heisei era. Derwent would input this number as jp 10123456-A.

Request For Examination

An unusual feature of the Japanese patent system is that applications are not automatically examined. The applicant has seven years from the filing date to file a request for examination. The patent is then usually examined in 24 to 30 months. However, as many applicants use this system to evaluate market developments, typical pendancy between filing and examination is five to seven years. Some patent applications can be processed much faster, being examined and published within 15 to 18 months of filing!


Recent changes to Japanese patent law in 1996 included the move from a pre-Grant patent opposition system (three months to file opposition) to a post-Grant opposition system (six months to file opposition, but the patent is valid until declared otherwise).

Under the old system, examined patents were published pre-grant (this second publication stage was called 'kokoku'). The last kokoku were issued in early 1996. Kokoku numbers started from zero every new year, so the JPO issued them with an Emperor year prefix.

A 1995 examined patent issued by the JPO would look like this: h07-12345 B2. Derwent World Patents Index would input this as JP9512345-B.

The last old-law Examined patents were published on 29 March 1996. The last JPO patent number for this publication date was JP96034772-B2. These old-law and, latterly, new-law examined Japanese patents are also issued on CD-ROM, with one disc per week since 1994.

Registered Patent Numbers

Under the old system unopposed patents would be assigned a seven digit registration number from a continuous series, but the patent was not republished under that number.
NOTE: This is a continuous number series which does not start from 0000001 each year and does not have a year prefix. If you are quoted a seven digit Japanese patent number like JP1,900,123, then you cannot order a copy of the text until you know the corresponding kokoku number for the registered patent up until 1996. Copies are available for registered patent numbers above 2,500,000.

This is because under the post grant opposition, the second publication stage now had a registered patent number assigned, starting with registered patent number 2500001.

The first new-law Granted patents were issued by the Japanese Patent Office on 29 May 1996. There was a nine week gap in publication between the last of the old-law and the first of the new-law B documents.

New Japanese Patent Numbers From January 2000

From 1 January 2000 the Japanese Patent Office will use the four digit Gregorian year in their numbering systems rather than the two digit Imperial year. From 1 January 2000 the following number formats will apply:

Type of Document Number Format
Patent applications Pyyyy-nnnnnn  
Utility model applications Uyyyy-nnnnnn  
Design applications Dyyyy-nnnnnn  
Published patents Pyyyy-nnnnnnA (patents based on PCTs begin with Pyyyy-500001A) Pyyyy-nnnnnnA  
Published utility models (utility models based on PCTs begin with Uyyyy-600001U utility model registrations start with 3000001) Uyyyy-nnnnnnU  
Published designs nnnnnnn

So, a patent application (Kokai) which may currently appear as 08-231479A would be given in the future as P2002-231479A.

Finding Japanese Patents

Searching Derwent World Patents Index is a good way to monitor the latest developments in Japanese technology, as all kokai have been covered since late 1995. If you need assistance in finding any Japanese patent, whether old or new, examined, unexamined or registered, Derwent staff would be delighted to help. We have experienced staff in London and Tokyo who can search in English or Japanese and, if necessary, provide part or full translations.

Machine-assisted translations of Japanese patents and PCT documents are also available, providing the opportunity to quickly scan and filter a selection of Japanese patents prior to (or instead of) investing in customised translations.