Light-emitting devices using a light-emitting diode (LED) element have been widely used. A light-emitting device of a previous type has a structure in which an LED element 33 is bonded to a substrate 31 with a die bond adhesive 32, a p electrode 34 and an n electrode 35 thereon are wire-bonded to a connecting terminal 36 of the substrate 31 with a gold wire 37, and the whole LED element 33 is sealed with a transparent mold resin 38, as shown in FIG. 3. However, in the light-emitting device of FIG. 3, of light emitted by the LED element 33, the gold wire absorbs light having a wavelength of 400 to 500 nm that is emitted toward the top face side and the die bond adhesive 32 absorbs some light that is emitted toward the bottom face side. Therefore, there is a problem of reduction in the light-emitting efficiency of the LED element 33.
From the viewpoint of improvement of light-emitting efficiency on light reflection of the LED element, as shown in FIG. 4, flip-chip mounting of an LED element 33 has been proposed (Patent Literature 1). In this flip-chip mounting technique, bumps 39 formed are provided to a p electrode 34 and an n electrode 35, respectively, and a light-reflective layer 40 is provided on a bump-forming face of the LED element 33 so that the light-reflective layer 40 is insulated from the p electrode 34 and the n electrode 35. Then an anisotropic conductive paste 41 or an anisotropic conductive film (not shown) is used to connect or fix the LED element 33 and a substrate 31 by curing the anisotropic conductive paste 41 or anisotropic conductive film. Therefore, in the light-emitting device of FIG. 4, the light output upward the LED element 33 is not absorbed by the gold wire and most of the light output downward is reflected off the light-reflective layer 40 and is output upward. Thus, the light-emitting efficiency (light extraction efficiency) does not reduce.
In addition to the viewpoint of improvement of light-emitting efficiency of the LED element by light reflection, from the viewpoint of preventing the color of light output from the LED element from being changed by discoloring, by heat or light, an insulating resin component in the anisotropic conductive paste or the anisotropic conductive film that is used in mounting of the LED element, a two-liquid curable methyl silicone resin or a two-liquid curable phenyl silicone resin that has excellent heat resistance and light resistance is tried to be employed for the insulating resin component in the anisotropic conductive paste or the anisotropic conductive film.