In recent years, a lighting device such as a bulb-type LED lamp having a light source of light-emitting diode has been used for various lighting fixtures as an alternative light source to a filament light bulb. The light-emitting diode is a semiconductor light-emitting element which has long life and low power consumption. When such type of lighting device with a light source of light-emitting diode is manufactured, the lighting device needs to be designed to be small in size and lead to improved productivity for mass production by taking the advantages of the light-emitting diode, and to produce a luminous flux comparable to that of a filament light bulb.
JP-A 2008-91140 (KOKAI) describes an LED light bulb and a lighting fixture, which include light-emitting diodes mounted on a substrate, a power supply device to turn on the light-emitting diodes, a cover to house the power supply device, the cover having a base mounted on one side and the substrate attached on the other side, and a translucent globe provided to cover the light-emitting diodes.
Also, JP-A 2003-59330 (KOKAI) describes an LED lighting fixture using a plate-shaped LED module mounted with multiple light-emitting diodes. The LED module is provided with a terminal block to directly connect an electric supply wire to the LED module, and thereby can be easily connected to the electric supply wire.
In the LED lighting fixture described in JP-A 2003-59330 (KOKAI), however, the electric supply wire to the light-emitting diodes are routed through the outside of a substrate from the back side of the substrate to the terminal block provided on the front surface of the substrate. The electric supply wire thus projects outward from the peripheral edge of the substrate. In order to mount the LED module on a lighting fixture body, the outer diameter dimensions of the fixture body must be inevitably large enough to provide an electrical insulation distance between the fixture body and the electric supply wire. The fixture body cannot be designed to be small in size.
JP-A 2003-59330 (KOKAI) also states that the electric supply wire may be designed to be connected to the terminal block from the back side of the substrate. However, if the lighting fixture is designed in such a manner, the wire will be interposed between the back side of the substrate and the fixture body which supports the substrate.
For this reason, if the LED light bulb described in JP-A 2008-91140 (KOKAI) is to be configured by using the light-emitting module described in JP-A 2003-59330 (KOKAI), the substrate cannot be in close contact with a base when being supported by the base because the electric supply wire resides between the back side of the substrate and the fixture body.
Consequently, heat of the light-emitting diodes mounted on the substrate cannot be effectively conducted to the fixture body which is composed of a metal having a high thermal conductivity, such as aluminum. This reduces light-emitting efficiency of the light-emitting diodes and thereby makes it difficult to achieve predetermined luminous flux.
Furthermore, when the electric supply wires are connected to the back side of the substrate, the connection must be made beforehand because the connection cannot be made once the substrate is fixed to the fixture body.
In this case, the substrate suspended in the air due to being connected with the electric supply wire is to be installed to the fixture body. When the substrate is fixed to the fixture body, the electric supply wire may break due to an external force applied to the connection portion, or the electric supply wire may come off from a quick connect terminal of the terminal block. Thus, such a lighting fixture is unsuitable for mass production.