JP2013239551A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element capable of simultaneously changing brightness and color temperature of emitted light in one light emitting element, and a light emitting device in which the light emitting element is used.SOLUTION: A light emitting device includes a light emitting element and a drive circuit for driving the light emitting element by pulse current. The light emitting element includes: a blue light emitting diode 2; and a phosphor layer including a first phosphor 5 and a second phosphor 6, the first phosphor being disposed at an upper part of the blue light emitting diode, having an emission wavelength in the range from 580 nm or more to 650 nm or less, and having an afterglow time until the luminescent strength decreases to 10% of 5 ms or more and 10 ms or less, and the second phosphor being disposed at an upper part of the blue light emitting diode, having an emission wavelength in the range from 490 nm or more to 600 nm or less, and having an afterglow time until the luminescent strength decreases to 10% of 1 ns or more and 10 ns or less.

Description

  The present invention relates to a light emitting element using a light emitting diode (hereinafter referred to as a white LED) used for an illumination light source and the like, and a light emitting device using the light emitting element.

  In recent years, research and development of semiconductor elements composed of nitride semiconductors typified by gallium nitride (GaN) have been active. The nitride semiconductor includes aluminum nitride (AlN), GaN, indium nitride (InN), and mixed crystals thereof.

  A semiconductor light emitting device composed of a nitride semiconductor can emit light in a wide wavelength range from ultraviolet or blue to infrared regions by controlling the film composition. As an application example thereof, a visible light emitting diode using a nitride semiconductor has already been commercialized (for example, Non-Patent Document 1).

  FIG. 5 shows a cross-sectional configuration of a conventional white LED element.

  The white LED element shown in FIG. 5 includes a package 1, a blue LED chip 2, a lead terminal 3, and a wiring wire 4. Inside the package 1, a YAG phosphor 5 is sealed with a silicone resin 6. The YAG phosphor 5 is Y3Al5O12: Ce3 + yellow phosphor particles.

  In order to adjust the color tone of the illumination light together with the dimming function for adjusting the brightness when the white LED element is used for illumination, a light emitting device that combines a white LED and a red LED has been proposed. (For example, refer to Patent Documents 1, 2, and 3.)

JP 2004-103443 A JP 2005-101296 A JP 2008-300124 A

Shuji Nakamura et. al. , Jpn. J. et al. Appl. Phys. Vol. 34 (1995) L. 1332-L. 1335

  However, the above-described conventional light emitting device requires an LED element that emits two types of light emission wavelengths in order to change the color tone of light, and further requires a driving circuit for each of them, resulting in an increase in cost. Have.

  The present invention has been made to solve such problems, and a light-emitting element capable of changing the color temperature of emitted light simultaneously with luminance by a single light-emitting element by a simple method, and the same are used. A light-emitting device is provided.

  In order to solve the above-described conventional problems, the light emitting device of the present invention is a light emitting device using a blue light emitting diode and a white light emitting diode having a phosphor layer excited by blue light, and has a main emission wavelength of 580 nm or more and 650 nm. In the following, the first phosphor having an afterglow time of 5 ms to 10 ms and the main emission wavelength from 490 nm to 600 nm and the emission intensity are reduced to 10% until the emission intensity is reduced to 10%. A light emitting element having a phosphor layer composed of a second phosphor having an afterglow time of not less than 1 ns and not more than 10 ns, and a drive circuit for driving the light emitting element with a pulse current, the drive circuit having a pulse width By using a driving method using a modulation method, a light emitting device capable of adjusting a color temperature simultaneously with a light flux at the time of light emission can be realized.

  The light-emitting element of the present invention can realize a light-emitting element that can change the color temperature of emitted light simultaneously with luminance with one light-emitting element.

1 is a cross-sectional configuration diagram of a light-emitting element according to Embodiment 1 of the present invention. Sectional configuration diagram in order of steps of the method for manufacturing the light emitting element in the first embodiment of the present invention Block diagram of the light-emitting device according to Embodiment 1 of the present invention Schematic of drive pulse and afterglow characteristics of phosphor in Embodiment 1 of the present invention Cross-sectional configuration diagram of a light emitting device using a conventional LED

  A first aspect is a light-emitting device including a light-emitting element and a drive circuit that is driven by a pulse current that drives the light-emitting element. The light-emitting element is provided with a blue light-emitting diode and an upper portion of the blue light-emitting diode. A first phosphor having a light emission wavelength in a range of 580 nm to 650 nm and having an afterglow time of 5 ms to 10 ms until the light emission intensity is reduced to 10%; A phosphor having a second phosphor having an emission wavelength in the range of 490 nm to 600 nm and an afterglow time of 1 ns to 10 ns until the emission intensity decreases to 10%. Including layers.

  In the second aspect, the drive circuit drives using a pulse width modulation method.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
The light-emitting device of Embodiment 1 includes a light-emitting element and a drive circuit.

  1 is a cross-sectional configuration diagram of the light-emitting element of Embodiment 1. FIG.

  The light emitting element shown in FIG. 1 includes a package 1, a blue LED chip 2, a lead terminal 3, a wiring wire 4, and a phosphor layer 51. Blue light emitted from the blue LED chip 2 enters the phosphor layer 51. The blue light incident on the phosphor layer 51 is converted into white light by the phosphor layer 51 and emitted to the outside.

  The package 1 has a recessed part, for example. A blue LED chip 2 and a phosphor layer 51 that covers the top of the blue LED chip 2 are disposed in the recess of the package 1.

  The phosphor layer 51 has a first phosphor layer and a second phosphor layer.

  The first phosphor layer has a first phosphor and a silicone resin 6 that covers the first phosphor. The first phosphor is sealed with a silicone resin 6.

  The first phosphor is composed of the YAG phosphor 5. The first phosphor has an emission wavelength in the range of 580 nm to 650 nm, and the afterglow time until the emission intensity decreases to 10% is 5 ms to 10 ms.

  The second phosphor layer has a second phosphor and a silicone resin 8 that covers the second phosphor. The second phosphor is sealed with a silicone resin 8.

  The second phosphor is composed of the R phosphor 7. The R phosphor is Ba2ZnS3: Mn2 + red phosphor particles. The second phosphor has a light emission wavelength in the range of 490 nm to 600 nm and a second phosphor having an afterglow time of 1 ns to 10 ns until the emission intensity is reduced to 10%. .

  Hereinafter, a method for manufacturing the light emitting device configured as described above will be described with reference to the drawings.

  FIG. 2A to FIG. 2C show cross-sectional configurations in the order of steps of the method for manufacturing the light emitting device according to the first embodiment.

  As shown in FIG. 2A, a blue LED chip is mounted on a package, and wiring wires are connected to lead terminals by wire bonding.

  Next, as shown in FIG. 2B, a phosphor paste in which YAG phosphor is dispersed in silicon resin by 10 wt% is applied to the inside of the package by potting, and is heated and dried to form a yellow phosphor layer.

  Thereafter, as shown in FIG. 2C, a light emitting element can be manufactured by attaching a phosphor sheet in which an R phosphor is dispersed in 0.4 wt% silicon resin to the upper part of the package.

  FIG. 3 is a block diagram showing the configuration of the light emitting device according to the first embodiment which includes a drive circuit for driving the light emitting element and the light emitting element.

  As shown in FIG. 3, the light emitting device includes a white LED element 301, a pulse current generation circuit 302, a timing controller 303, and a dimming volume 304.

  The pulse frequency of the pulse current generation circuit 302 connected to the white LED element 301 and the ON / OFF duty ratio are controlled by the timing controller 303, and the duty ratio is adjusted by the dimming volume 304 to flow to the white LED element 301. The brightness can be varied by changing the average current value.

  FIG. 4 shows an example of a timing chart showing drive pulses for driving the light emitting elements and light emission timing.

  Since the YAG phosphor 5 uses the Ce3 + fd transition which is the emission center, the afterglow time is as short as several ns to 10 ns. On the other hand, the R phosphor 7 has a long afterglow time of 1 ms to 10 ms because the dd transition of Mn2 +, which is the emission center, is a forbidden transition. When the current pulse frequency is driven at about 100 Hz, if the duty ratio is small, the ratio of the amount of light from the R phosphor with long afterglow to the amount of light of the entire light emitting element increases. On the other hand, when the duty ratio is large, the amount of light from the R phosphor with a long afterglow is saturated, and the amount of light from the YAG phosphor with a short afterglow increases in proportion to the duty ratio. The ratio of the light from the R phosphor in the area is reduced.

  Table 1 shows each duty of the driving pulse, the luminous flux of the light emitting element, and the color temperature when the light emitting device of the first embodiment is driven at 100 Hz.

  As can be seen from Table 1, when the duty ratio is 5%, the luminous flux from the light emitting element is small and the color temperature is as low as 2200K. As the duty ratio is increased, the luminous flux increases and the color temperature increases. At 100%, the color temperature is as high as 7000K.

  As described above, the light-emitting device of Embodiment 1 has a natural brightness that the color temperature is low when the luminous flux is small, that is, when the light source is dark, and the color temperature is high when the luminous flux is large, that is, when the light source is bright. A light-emitting device can be realized with a simple element configuration and a control circuit. In addition, it is possible to realize a light emitting device having excellent dimming property at low cost.

  In this embodiment, the Y phosphor is applied as the phosphor of the light emitting element, and then the R phosphor sheet is bonded. However, the present invention is not limited to this configuration, and the YAG phosphor and the R phosphor are combined. The mixed phosphor paste may be applied in the package.

  Alternatively, the YAG phosphor paste may be applied after applying the phosphor paste containing the R phosphor before applying the YAG phosphor.

  The light-emitting device according to the present invention can realize a light-emitting element that can change the color temperature of emitted light simultaneously with luminance with a single light-emitting element, and has excellent dimming properties at low cost. It can be applied to uses such as displays.

1 Package 2 Blue LED Chip 3 Lead Terminal 4 Wiring Wire 5 YAG Phosphor 6 Silicone Resin 7 R Phosphor 8 Silicone Resin 51 Phosphor Layer 301 LED Element 302 Pulse Current Generation Circuit 303 Timing Controller 304 Dimming Volume

Claims (2)

A light-emitting device comprising a light-emitting element and a drive circuit driven by a pulse current that drives the light-emitting element,
The light emitting element is
A blue light emitting diode,
A first phosphor disposed on the blue light emitting diode and having a light emission wavelength in the range of 580 nm to 650 nm and having an afterglow time of 5 ms to 10 ms until the light emission intensity decreases to 10%. And a second light emitting diode disposed at an upper portion of the blue light emitting diode, having an emission wavelength in a range of 490 nm to 600 nm and having an afterglow time of 1 ns to 10 ns until the emission intensity is reduced to 10%. A light emitting device including a phosphor layer having a phosphor. The light-emitting device according to claim 1, wherein the drive circuit is driven using a pulse width modulation method.

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