Phosphor mixture, light-emitting device, image display and lighting unit

Abstract

A light-emitting device having a high luminance and emitting a light more similar to the natural light and having a little color shift due to the variation of the emitted light amount. The device comprises a light source which emits light when a drive current is applied and at least one wavelength conversion material emitting a light of a wavelength different from that of the light emitted from the light source when it absorbs at least a part of the light from the light source. The expressions (D), (E) are satisfied where x1 (17.5) is the chromaticity coordinate value x of the light emitted at a drive current density of 17.5 A / cm<2>, y1(17.5) is the chromaticity coordinate value y thereof, x1 (70) is the chromaticity coordinate value x of the light emitted at a drive current density of 70 A / cm<2>, and y1 (70) is the chromaticity coordinate value y thereof. -0.006 = x1(17.5) -x1(70) =0.006 (D) -0.006 = y1(17.5) -y1(70) =0.006 (E).

Description

technical field [0001] The present invention relates to a light emitting device, a white light emitting device, and an illuminating device and an image display device using the above device. In particular, it relates to a light emitting device and a white light emitting device that combine a light source such as a light emitting diode (LED) or a laser diode (LD) with a wavelength conversion material such as a phosphor that absorbs light emitted from the light source and emits light of a different wavelength. , and an illumination device and an image display device using the above device. Background technique [0002] Conventionally, it is known that a white light-emitting light-emitting device composed of a semiconductor light-emitting element such as a gallium nitride (GaN)-based light-emitting diode (LED) and a phosphor as a wavelength conversion material has low power consumption and a long life. [0003] However, it has been pointed out that this light-emitting device h...

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Problems solved by technology

[0019] However, according to the prior art described in Patent Document 1, although the color rendering properties of a white light emitting device are improved by combining these phosphors, there is still a problem that all phosphors in combination exhibit a significant temperature extinction phenomenon. When the current value flowing in the white light emitting device is increased, the luminous flux emitted by the light emitting device decreases, and at the same time, a large deviation occurs in the luminous color

[0020] In addition, the red phosphor used is a sulfide-based red phosphor with low moisture resistance, so it is easy to age, and its synthesis is difficult, so its production cost is high, and the white light-emitting device obtained by using this red phosphor also has low durability. And the problem of high price

In addition, the light emission color of the green phosphor used is yellowish, so it also has the problem of insufficient light emission in the blue-green region and poor color rendering.

[0021] In addition, in the prior art described in Non-Patent Document 1 and Patent Document 2, there is a problem that sufficient luminous flux and color rendering properties cannot be obtained even by combining these phosphors, and sulfides tend to deteriorate when used in a white light emitting device. , and these phosphors are substances that obviously exhibit temperature extinction, so when the current to the white light emitting device increases, a large deviation occurs in the luminous color

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