A downlight is a lighting device which is mounted in advance on a ceiling, etc., of a building, and is used to create, for example, a warm atmosphere by illuminating a floor or a table, etc. (for example, refer to Patent document 1). A conventional lighting device to be used for a downlight includes, for example, a halogen lamp as a light source. A halogen lamp is a so-called point light source which emits light in various directions. In order to direct light from the halogen lamp toward a desired range, the lighting device is provided with a cone-shaped reflector.
However, a halogen lamp emits light by supplying electricity to a filament as a resistor and generates a large amount of heat along with luminescence. Therefore, as compared with a fluorescent lamp, for example, the energy efficiency is inferior.
In order to direct light emitted in various directions from the halogen lamp toward a desired direction, the reflector inevitably has a comparatively large shape which is parabolic in a cross section, for example. Therefore, to attach the lighting device, a corresponding space must be secured on the ceiling.
FIG. 48 is a sectional view showing an example of a conventional LED lamp which can be used as an alternative to a fluorescent lamp (for example, refer to Patent Document 1). The LED lamp X1 shown in this drawing includes a long rectangular substrate 191, a plurality of LED modules 192 mounted on the substrate 191, a heat radiation member 195 to which the substrate 191 is attached, a case 193 housing the substrate 191, and terminals 194. On the substrate 191, a wiring pattern not shown to be connected to the plurality of LED modules 192 and the terminals 194 is formed. The LED lamp X1 is arranged to make a plurality of LED modules 192 emit light by fitting the terminals 194 into slots of sockets of a general fluorescent lamp lighting fixture.
However, in the LED lamp X1, when it is turned on, individual LED modules 192 look like point light sources. Therefore, in order to make the appearance of the LED lamp X1 look like a fluorescent lamp, it is necessary to greatly diffuse light from the LED modules 192 by the case 193. As the diffusion effect by the case 193 increases, the transmittance of the case 193 decreases. This deteriorates the luminous efficiency of the LED lamp X1.
If the current to be supplied to each LED module 192 is increased to increase the luminance of the whole LED lamp X1, heat generation from the LED modules 192 improperly increases. This also deteriorates the luminous efficiency of the LED lamp X1.