1. Field of the Technology
The technology presented herein relates to a semiconductor light-emitting device (hereinafter, referred to an “LED”).
2. Description of the Related Art
By using FIGS. 4A to 4C, conventional LEDs having a plurality of LED chips (for example, refer to Japanese Unexamined Patent Publication No. 2006-310613 and Japanese Unexamined Patent Publication No. 2004-274027) will be described. FIG. 4A is a plan view showing a structure of the conventional LED and FIGS. 4B and 4C are cross-sectional views along lines I-I and II-II, respectively, of FIG. 4A.
As shown in FIGS. 4A, 4B, and 4C, the conventional LED includes a blue LED chip 3B to emit blue light, a green LED chip 3G to emit green light and a red LED chip 3R to emit red light on a substrate 1. The substrate 1 has a first terminal 1a and a second terminal 1b for every LED chip 3. Each LED chip 3 is placed on the first terminal 1a. Each LED chip 3 has two electrodes, and a first conductive wire 5a electrically connects one electrode of the two electrodes and the first terminal 1a, and a second conductive wire 5b electrically connects the other electrode of the two electrodes and the second terminal 1b. The LED chips 3B, 3G and 3R are sealed with a transparent resin sealing layer 7. When a voltage is applied between the first terminal 1a and the second terminal 1b, the LED chips 3B, 3G and 3R emit blue, green and red lights L, respectively.
In such an LED, it is known that light of arbitrary color, for example white light, is obtained by mixing the blue, green and red lights.
However, a spectrum of the white light obtained by mixing the lights L emitted from the LED chips 3B, 3G and 3R has three peaks with narrow width as shown in FIG. 5, and such white light has a bad color rendering property.
There is known a technology in which as shown in FIG. 6, in order to improve a color rendering property, an exciting LED chip 3E to emit light (for example, blue light) for exciting a fluorescent substance is provided in place of the green LED chip 3G, and a fluorescent substance layer 9 is formed by applying a fluid material (hereinafter, referred to as a “fluorescent substance material”) containing a fluorescent substance to the exciting LED chip 3E and curing the material. Spectra of the white light obtained in using a green fluorescent substance and in using both a yellow fluorescent substance and a green fluorescent substance are shown in FIGS. 7A and 7B, respectively. As shown in FIGS. 7A and 7B, it has been found that a width of a central peak becomes broad in either case and a color rendering property is improved by a combination of the exciting LED chip 3E and the fluorescent substance layer 9.
Since the fluorescent substance material has fluidity, when the fluorescent substance material is applied to the exciting LED chip 3, it may spread as shown in FIG. 8 and adhere to the LED chip 3 to which the fluorescent substance material is not applied. In this case, there may arise problems that emission intensity is reduced and control of color temperature becomes difficult.
The technology presented herein was made in view of the above circumstances, and it is a feature of an example embodiment presented herein to provide an LED which can prevent a fluorescent substance material from adhering to an LED chip whose emitted light is not wavelength-converted by a fluorescent substance layer.