Searching for Prior Art

This document provides some basic guidelines on how to perform a prior art search. It offers suggestions on what you need to do before using Derwent Innovations Index.


What is Prior Art?

Broadly speaking, prior art is all public documents, both domestic and foreign, that may be referred to in a patent application or an examination report. Prior art must support a patent applicant's claim that the invention is novel, useful, and non-obvious. It includes patent documents, journal articles, technical publications, disclosures, and other public information.

Derwent Innovations Index brings together over 22 million patent records enabling you to launch an extensive prior-art search. Powerful searching tools allow you to retrieve patent records based on search queries that search the Derwent Innovations Index patent database.

For those institutions that have a subscription to Derwent Chemistry Resource, additional search tools allow you to retrieve over 2 million compounds from the chemical structure database. Moreover, the product offers you the option to combine patent data searches with chemical data searches to create combination searches that include both patent and compound records.of new ideas.


What is Prior Art Searching?

A prior art search is an organized review of patent documents, journal articles, technical publications, disclosures, and other public information. A good prior art search will reveal if an invention has patent protection. It is the best way to determine if an invention is novel, useful, and non-obvious. It can also reveal if an invention infringes on an existing patent, thus possibly resulting in a legal challenge.


What is the Purpose of Prior Art Searching?

Prior art searching is a required step in the patent application process. A good prior art search can determine if an idea is worth the time, money, and effort of developing an invention already patent protected. Knowing that a patent already exists may also prevent you from bringing a product to market after a competitor's product or from launching a product that is obsolete before it hits the market. It may also help you write a better patent application.

Below are some reasons for conducting a prior art search.

  • To assess the relevance of your work in a particular technology field.

  • To see if someone else has joined the race, someone else has taken the same approach, or the concept has already been mentioned in another patent.

  • To exhaustively search for anything remotely similar that might be cited by a patent examiner or to repeat the research stage patent search aims.

  • To watch for signs of potential imitators, the emergence of competitors attracted by the new market, or new uses for patented technology through citation analysis.

  • To determine if an R&D concept is already protected by a patent, or if patent protection may have expired so that the invention is available for use.


How Do I Develop a Search Strategy?

Searching worldwide patent documents and technical literature should always be done at the start of any R&D effort in order to avoid wasteful and costly duplication.

The first step in conducting a prior art search is to determine the scope of the search. The scope and focus of the search will depend on the subject matter (for example, electrical, chemical, engineering, etc.) and the information sought. Determine early in the process how to budget your time to cover the scope of your search. The results of any search will depend on how much time is spent on actual research.

The second step is to determine what type of search you intend to perform. Derwent Innovations Index offers Search and Advanced Search.

As a starting point, consider the following options.

  • What sources can be consulted before a search? For example: inventor, company, academic institution, private research organization, nonprofit agency, etc.

  • What prior art did the inventor, company, institution, or organization rely on when filing the patent application? For example: patent documents, journal articles, technical publications, disclosures, and other public information.

  • Which companies, institutions, private research organizations, academic institutions, etc. were involved in developing the idea and/or the invention?

Did You Know ... Patent records in Derwent Innovations Index include both a Patents Cited and an Articles Cited feature that lists the patents and articles cited by the examiner and the inventor. The Patents Cited feature lists all the patents that have been cited in a particular patent; whereas the Articles Cited feature lists all the articles cited in a particular patent. Links to the Full Record of cited patents are available within Derwent Innovations Index.


What Should I Do Before I Begin?

Before beginning the actual search, write down as much information as possible. Here are some suggestions.

Topic (Search Terms)

Think of common terms and phrases to describe the invention and how the invention will function or be used. If your search finds too many records, review a few records to learn the best search terms to use in later searches. Eliminate any common terms that will result in too many results such as "computer". Instead, use more specific phrases such as "computer application".

Use search operators and wildcards to further define your search criteria. For example, a Topic search on diabet* AND insulin* finds patent records in which the terms diabetes, diabetic, insulin, and insulin-dependent appear in the title and/or abstract of a patent record.


Patent Numbers

Write down any known patent numbers to begin a search. Write down all patent numbers listed on the Full Record. They can be later used to find additional patent records in a Search function.

The Full Record also displays the number of patents cited by the inventor / examiner. Search on all cited patents. Links from these cited patents will take you to the Full Record of these records.



Write down the names of any inventors who have developed similar chemical and non-chemical inventions. You can use these names to begin your initial search.

Many patents list the names of more than one inventor. Write down the name of each inventor listed on the Full Record. Later searches may uncover records in which a particular inventor is the sole inventor of an invention.



Write down the names of any companies, organizations, and institutions that have developed similar patents. You can use these names to begin your initial search.

Write down the names of any inventor whose name appears on a patent filed by a particular company, organization, and institution. Write down the names of any inventors that have been cited on a patent by the organization and/or patent examiner.


Derwent Codes / Other Codes

Write down the following codes:

  • International Patent Classification
  • Derwent Class
  • Derwent Manual
  • Primary Accession Number

These codes can be found in the Full Record. They can be later used to find additional prior art records in an Advanced Search.

Use wildcards to include searches for related patent documents. For example, a search on the Derwent Manual Code T01-C03* finds patents with the code T01-C03C, T01-C03CA, T01-C03C1, etc.



Write down the following dates:

  • Application
  • Publication
  • Filing Details
  • Priority

These dates can be found on the Full Record. They can be later used to find additional prior art records in an Advanced Search.


What Types of Prior Art Searches Are There?

Generally speaking, prior art searches fall under the following categories.

  • Novelty
  • Validity
  • Infringement
  • State-of-the-art


Novelty Search

A novelty search is done before you file a patent application. It is intended to determine if an invention has been granted patent protection in the United States, Great Britain, Japan, and elsewhere. Remember, a single prior art source can be used by the patent examiner as the basis for rejecting a patent application. A combination of several prior art sources may be sufficient to reveal every obvious aspect of an invention, thus forming the basis for a rejection.


Validity Search

A validity search is done to assess all prior art considered by the patent examiner before the issuance of a patent. This type of search can determine if significant prior art literature was overlooked during the patent application process. Any overlooked prior art may be sufficient to invalidate the patent if, had the examiner been aware of it, the patent would not have been issued.


Infringement Search

An infringement search focuses on current (that is, unexpired) patents in a particular country where you intend to market a product. Its purpose is to find patents that may be infringed by a new invention. In other words, to protect yourself from possible litigation, you need to perform an infringement search to uncover existing patents that are protected by the patent laws of a particular country.

In the United States, patents are granted for a period of 20 years from the filing date or 17 years from the date the patent was made public. The time period in other countries, however, may differ. Therefore, an infringement search need not go back farther than a patent's term.


State-of-the-art Search

This is the broadest and most general type of prior art search. Some searches look for worldwide technological trends, others look for current prior art to increase awareness of what the competition is doing, while others look for subjects of interest that can encourage the development