In recent years, it has been desired to reduce the weight of a vehicle, and for this purpose, the reduction in weight of respective parts which make up a vehicle is in progress. Lamps are included in those parts which are required to be reduced in weight.
In general, a vehicle lamp includes a lamp body which is opened at a front thereof, a front cover which is attached to the lamp body so as to close the front opening portion, an extension, a reflector, a light source, electric components and the like. In order to reduce the total weight of such a vehicle lamp, it is considered to be effective to reduce the weight of the lamp body which is generally formed from a resin material and which occupies a relatively large portion of the total weight of the vehicle lamp.
On the other hand, in a resin molded part which is formed from a resin material, if the resin molded part is formed only from a resin, a sufficient strength would not be obtained, and therefore, it is general practice to add a filling material (a filler) to a base resin. As a preferable filler for such a resin molded part which is required to have a certain mechanical strength, there has been used a mineral filler like talc which has a relatively large specific weight.
Therefore, in order to achieve a reduction in weight of the resin molded part which is formed from a resin material while maintaining the mechanical strength, it is considered to be effective to use a filler having a smaller specific weight.
Patent Document 1 discloses a technique to obtain a molded part from a resin composition which contains a polypropylene and a plant fiber.