JP4670323B2 - LIGHT EMITTING DEVICE, BACKLIGHT DEVICE FOR LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME, AND LIGHTING DEVICE - Google Patents

Description

  The present invention relates to a light-emitting device including an AlGaInP-based compound semiconductor light-emitting element and an AlGaInN-based compound semiconductor light-emitting element, a backlight device for a liquid crystal display device using the same, and an illumination device.

  Currently, cold cathode fluorescent lamps are widely used as the light source of backlight devices for liquid crystal display devices, but the demands for color reproducibility and responsiveness are becoming very severe as the applications of liquid crystal display devices expand. Given this, it is expected that it will be difficult to deal with in the future. Therefore, in recent years, attention has been focused on light sources using light emitting diodes (LEDs) of three primary colors of red (R), green (G), and blue (B) as light emitting elements. The LED has so-called wavelength selectivity that enables control of the emission wavelength by the mixed crystal composition of the active layer, and is excellent in color purity and high-speed response. Therefore, the three primary colors are mixed into white light. Is used as a light source of a backlight device for a liquid crystal display device, the color reproducibility and responsiveness of the liquid crystal display device can be greatly improved. Further, the LED is not limited to the use as a backlight device for a liquid crystal display device, and is expected to be applied to, for example, a display device and various illumination devices (see, for example, Patent Document 1).

  By the way, the LED light source has a problem in that the wavelength and the light emission efficiency are largely changed due to the temperature change as compared with the conventionally used cold cathode tubes. For example, when an LED is used as a light source of a backlight device for a liquid crystal display device, the temperature rises due to heat generation immediately after the power is turned on, and as a result, the color and brightness of the liquid crystal display device change and desired characteristics cannot be obtained. Occurs. In addition, if the light output of each color of the LED is monitored in real time in order to suppress the change in hue and the white light is maintained, there is a problem that the power consumption is greatly increased. This problem is particularly noticeable in a large system that requires a large number of LEDs, such as a large-screen liquid crystal display device.

Various heat dissipation measures have been proposed to avoid the above-described problems. For example, a heat dissipation mechanism is provided on the chip itself in which the LED is embedded to dissipate the heat generated by the LED onto a substrate or the like (see, for example, Patent Document 2 and Patent Document 3). However, when the heat is stored in the substrate, the temperature of the LED eventually increases, and the same problem as described above occurs. Therefore, in practice, a heat dissipation measure on the substrate side on which the LED is mounted is important. Therefore, for example, a heat sink is provided on the back surface of the substrate on which the LED is mounted, and heat generated by the element is efficiently released from the heat sink via the circuit board (see, for example, Patent Document 4 and Patent Document 5).
JP 11-340515 A JP 2003-188424 A JP 2002-359403 A JP 2002-33011 A JP 2003-92011 A

  However, even when the heat sinks described in Patent Document 4 and Patent Document 5 described above are used, for example, LEDs of three primary colors of RGB, such as a light emitting device, a backlight device for a liquid crystal display device, and a lighting device, are used as a substrate. However, the above-described problems such as a change in hue and a change in luminance are caused, and no effective solution has been found at present.

  Therefore, the present invention has been proposed in view of such a conventional situation, and a light-emitting device capable of suppressing a change in color and a luminance due to a temperature rise and reducing power consumption, and a It is an object of the present invention to provide a backlight device for a liquid crystal display device and an illumination device used.

  As a result of a long-term study conducted by the present inventors in order to solve the above-described problem, an AlGaInP-based compound semiconductor light-emitting device that is easily affected by a temperature rise is compared with another light-emitting device having a large calorific value such as an AlGaInN-based compound semiconductor light-emitting device. Has obtained the knowledge that heat radiation by different heat sinks is extremely effective in stabilizing the characteristics, and has completed the present invention.

  That is, a light-emitting device according to the present invention includes a plurality of types of light-emitting elements including at least an AlGaInP-based compound semiconductor light-emitting element, and a heat sink that dissipates heat generated from the light-emitting element, and corresponds to the AlGaInP-based compound semiconductor light-emitting element. Is thermally independent from a heat sink corresponding to another light emitting element having a larger calorific value than the AlGaInP-based compound semiconductor light emitting element. In addition, a backlight device for a liquid crystal display device according to the present invention includes the light emitting device as a light source. Furthermore, an illumination device according to the present invention includes the light emitting device.

  For example, an AlGaInP-based compound semiconductor light-emitting device generally used as a red (R) LED is an AlGaInN-based compound semiconductor light-emitting device (B, G) generally used as a blue (B) and green (G) LED. Compared with this, the heat generation amount is small, and the peak wavelength and the light emission efficiency are easily affected by the temperature rise. Conventionally, since the AlGaInP-based compound semiconductor light-emitting device and the AlGaInN-based compound semiconductor light-emitting device are all dissipated by the same heat sink, the AlGaInP-based compound semiconductor light-emitting device is heated via the heat sink. There has been a problem of causing a large wavelength shift and a change in luminous efficiency.

  In the present invention, the heat sink of the AlGaInP-based compound semiconductor light-emitting element is thermally independent from other light-emitting elements that generate a larger amount of heat than the AlGaInP-based compound semiconductor light-emitting element, such as an AlGaInN-based compound semiconductor light-emitting element. The adverse effect on the AlGaInP-based compound semiconductor light-emitting device due to is suppressed, and as a result, the wavelength shift and the decrease in light emission efficiency of the AlGaInP-based compound semiconductor light-emitting device are suppressed. Since the AlGaInN-based compound semiconductor light-emitting element is relatively insensitive to temperature rise, changes in characteristics of the AlGaInN-based compound semiconductor light-emitting element due to the heat generated by the AlGaInN-based compound semiconductor light-emitting element itself hardly cause a problem. Therefore, as a whole light-emitting device in which other light-emitting elements such as an AlGaInP-based compound semiconductor light-emitting element and an AlGaInN-based compound semiconductor light-emitting element coexist, color and luminance are stabilized.

  According to the present invention, by making the heat sink of the AlGaInP-based compound semiconductor light-emitting device thermally independent from other light-emitting devices having a large calorific value, the wavelength shift and the change in light emission efficiency of the AlGaInP-based compound semiconductor light-emitting device are reduced. As a result, it is possible to provide a light emitting device that realizes stabilization of hue and luminance. Moreover, since the light-emitting device which concerns on this invention suppresses the hue change in use, it can aim at reduction of the power consumption required for the control which maintains a white point, for example. In addition, according to the present invention, by using the above-described light emitting device, it is possible to realize a backlight device and a lighting device for a liquid crystal display device that achieves power saving while achieving stabilization of color and luminance.

  Hereinafter, a light-emitting device to which the present invention is applied and a backlight device and a lighting device for a liquid crystal display device using the same will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view applied to a backlight device of a liquid crystal display device. The backlight device includes a light emitting device 1 serving as a light source and a reflection unit 2 that reflects and diffuses light emitted from the light emitting device 1 to form a planar light source.

  First, the light emitting device 1 constituting the backlight device will be described. The light emitting device 1 basically includes a plurality of light emitting elements 11 and a heat sink 12 that dissipates heat released from the light emitting elements 11.

  The light emitting element 11 has a chip shape that can be mounted on an arbitrary substrate (here, the bottom surface of the reflection unit) or the heat sink 12, and a light emitting diode (LED) having a compound semiconductor as a light emitting layer is sealed with a resin or the like. Stopped. The light-emitting element 11 includes an AlGaInP-based compound semiconductor as a light-emitting layer, a light-emitting element 11R including an LED whose emission color is red (hereinafter referred to as an AlGaInP-based light-emitting element 11R), and an AlGaInN-based compound semiconductor as a light-emitting layer. A light emitting element 11G (hereinafter referred to as an AlGaInN light emitting element 11G) having a green emission color and a light emitting element 11B (hereinafter referred to as AlGaInN) having an AlGaInN compound semiconductor as a light emitting layer and having a blue emission color. System light emitting element 11B). The color of each light emitting element 11 is mixed and becomes, for example, white light. In FIG. 1, the AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B are collectively shown as AlGaInP light emitting elements 11B and 2G. Actually, however, the AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B are different from each other. It is mounted as a separate light emitting element. The arrangement state of the light emitting elements 11 can be, for example, a line for each color extending in a direction perpendicular to the paper surface in FIG. 1, but is not limited thereto.

  The heat sink 12 can be used without particular limitation as long as it can dissipate the heat generated by the light emitting element 11. For example, a heat sink composed of metal, ceramic, silicon, or the like can be used. For example, a metal layer is sandwiched between a pair of insulating layers. It is preferable to use a heat sink having a wiring pattern corresponding to the light emitting element 11 and serving as a circuit board and a heat sink. Further, as shown in FIG. 1, fins 13 may be provided on the surface (back surface) opposite to the mounting surface of the light emitting element 11 of the heat sink 12 to further enhance the heat dissipation of the heat sink 12.

  In the present invention, heat dissipation from the region of the heat sink 12 related to heat dissipation of the AlGaInP light emitting element 11R and other light emitting elements (AlGaInN light emitting element 11G and AlGaInN light emitting element 11B) having a larger calorific value than the AlGaInP light emitting element 2R. Ensure that the regions involved are thermally independent of each other. For example, the heat sink 12 is separated and is composed of a heat sink 12a and a heat sink 12b that are thermally independent from each other, and one of the heat sinks 12a is in thermal contact with the AlGaInP light emitting element 11R, and the other light emitting element (AlGaInN based) The other heat sink 12b is preferably in thermal contact with the light emitting element 11G and the AlGaInN light emitting element 11B). The AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B, which are other light emitting elements, may correspond to, for example, a common heat sink 12b or may dissipate heat separately by corresponding different heat sinks.

  Note that the state in which the AlGaInP light emitting element 11R is thermally independent from the other light emitting elements is the heat sink 12a corresponding to the AlGaInP light emitting element 11R and the heat sink 12b corresponding to the other light emitting elements. When light is emitted, it means that the temperature of each heat sink is different. The heat sink temperature here is not the heat sink temperature immediately after the light emitting element 11 emits light, but the temperature after the light emitting element 11 maintains light emission for an appropriate time and the heat sink is heated to reach equilibrium by the heat generated by the light emitting element 11. Say.

  When the mounting surface of the light emitting element 11 is tilted from the horizontal plane, as shown in FIG. 1, the AlGaInP light emitting element 11R and the heat sink 12a on which the light emitting element 11 is mounted have other light emitting elements (AlGaInN light emitting element 11G and AlGaInN light emitting). The element 11B) or another light emitting element is preferably disposed below the heat sink 12b on which the element is mounted. By disposing the AlGaInP light emitting element 11R and the heat sink 12a below, the temperature rise of the AlGaInP light emitting element 11R and the heat sink 12a due to convection of air heated by another light emitting element or the heat sink 12b can be suppressed.

  Next, the reflection unit 2 constituting the backlight device will be described. The reflection unit 2 has a function of shielding, mixing, and diffusing the light emitted from the light emitting device 1 and is arranged for the purpose of reducing color unevenness, luminance unevenness, and the like of a liquid crystal display using the backlight device. The reflection unit 2 includes, for example, a light-shielding reflection plate 21 that shields and reflects light emitted from the light-emitting element 11, a reflection plate 22 that reflects light reflected by the light-shielding reflection plate 21 to the front surface, and a light guide reflection plate 21 on the front surface. A light guide color mixing plate 23 that mixes and guides each color, a diffusion plate 24 disposed on the front surface of the light guide color mixing plate 23, and a housing 25 that supports them are configured. The light emitting element 11 is mounted inside the bottom surface 25a. The bottom surface 25 a of the reflection unit 2 and the heat sink 12 are in thermal contact with each other, and heat generated by the light emitting element 11 is transmitted to the heat sink 12. Needless to say, the reflection unit 2 is not limited to the configuration shown in FIG.

  In the light emitting device 1 of the present invention, the heat sink 12a involved in heat dissipation of the AlGaInP light emitting element 11R is separated from the heat sink 12b involved in heat dissipation of the AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B, which are other light emitting elements. And is thermally independent. Here, since the AlGaInP light emitting element 2R has a smaller amount of heat generation than the AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B, the temperature of the heat sink 12 that finally reaches when the light emitting element 11 emits light is the AlGaInP light emitting element. The heat sink 12a corresponding to the element 2R is lower than the heat sink 12b. The temperature difference between the heat sink 12a and the heat sink 12b is, for example, 10 ° C. or higher, more preferably 20 ° C. or higher. Therefore, by making the heat sink 12a corresponding to the AlGaInP light emitting element 2R thermally independent from the heat sink 12b corresponding to the AlGaInN light emitting element 11G and the AlGaInN light emitting element 11B, the temperature rise of the AlGaInP light emitting element 2R is increased. It is possible to suppress the wavelength shift of the AlGaInP-based light emitting element 11R and a significant decrease in light emission efficiency. Therefore, it is possible to prevent a change in color and luminance of the light emitting device 1 as a whole and stabilize temperature characteristics.

  In addition, when a backlight device for a liquid crystal display is configured by combining the light emitting device 1 with the reflection unit 2 or the like, occurrence of problems such as a change in hue and a change in luminance during use of the liquid crystal display is prevented, and the display characteristics of the liquid crystal display are displayed. Can be improved. Further, since the change in the hue of the backlight device is reduced, the need for control to maintain the desired whiteness is reduced, and the power consumption required for control can be reduced. Therefore, the backlight device to which the present invention is applied is suitable for a large system that requires a large number of light emitting elements 1 as a backlight, for example, a backlight for a 30-inch class large-screen liquid crystal display device.

  In the above description, the heat sink 12 is structurally separated into the heat sink 12a and the heat sink 12b, and the AlGaInP light emitting element 11R and other light emitting elements are associated with each other. 12, the structure of the heat sink 12 is limited if the region involved in heat dissipation of the AlGaInP-based light emitting element 11R and the region involved in heat dissipation of the AlGaInN-based light emitting elements 2G, 2B are thermally independent. It is not a thing. For example, the heat sink 12a and the heat sink 12b may be structurally connected or common as long as they are thermally independent from each other.

  Next, a modification of the light emitting device and the backlight device using the light emitting device will be described with reference to FIG. In the following, members similar to those of the light emitting device and the backlight device shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

In the light emitting device 1 of the modified example, the air cooling fan 14 is disposed close to the heat sink 12a corresponding to the AlGaInP-based light emitting element 11R, and the heat sink 12a is forcibly cooled. The air cooling fan 14 is preferably configured to control the temperature of the heat sink 12a while monitoring the heat sink temperature output from a temperature sensor (not shown) attached to the heat sink 12a.
Further, in the reflection unit 2, a part of the housing 25 is opened and a ventilation path 26 is provided on the mounting surface side of the light emitting element 11. For example, the lower side wall 25b of the AlGaInP-based light emitting element 2R is opened to serve as an intake port 27a, and the bottom surface 25a above the AlGaInP-based light emitting device 2R is opened to serve as an exhaust port 28a. The AlGaInN light emitting elements 2G and 2B are also provided with an intake port 27b and an exhaust port 28b. A heat insulating material 29 separates the air passage 26a of the AlGaInP light emitting element 2R and the air passage 26b of the AlGaInN light emitting elements 2G and 2B.

  In the light emitting device 1 of the modified example, since the air cooling fan 14 is installed and the temperature of the heat sink 12a is controlled by the air cooling fan 14, the heat dissipation of the AlGaInP light emitting element 2R is further improved, the wavelength shift of the AlGaInP light emitting element 11R, A decrease in luminous efficiency can be more reliably suppressed.

  As described above, the example in which the backlight device of the liquid crystal display is configured by the light emitting device of the present invention has been described, but the present invention is not limited to this, and a plurality of types of light emitting elements including an AlGaInP light emitting element and a heat sink are provided. Needless to say, the present invention can be applied to, for example, a light-emitting device that does not have a reflection unit or the like, and various illumination devices. In addition, when applied to a lighting device with power consumption of 10 W or more, preferably 20 W or more, the effect of the present invention can be obtained effectively.

  Specific examples to which the present invention is applied will be described based on experimental results. In addition, this invention is not limited to description of a following example.

  Below, the problem in the conventional light-emitting device (conventional example) which used R, G, B LED as a light source is demonstrated first, and the backlight apparatus (Example) of this invention is demonstrated after that.

  First, LEDs of each emission color of R, G, and B were prepared. For example, an AlGaInP LED having a wavelength of 630 nm was selected as the red LED, an AlGaInN LED having a wavelength of 525 nm was selected as the green LED, and an AlGaInN LED having a wavelength of 460 nm was selected as the blue LED. These are examples of selecting a wavelength that substantially corresponds to an NTSC ratio of 100%. The peak wavelength and energy efficiency of these LEDs at room temperature are as shown in Table 1 below, for example.

  Further, the wavelength and energy efficiency of these LEDs in an environment of 60 ° C. are as shown in Table 2 below, for example. FIG. 3 shows the relationship between the temperature of each LED and energy efficiency, and FIG. 4 shows the relationship between the temperature of each LED and the emission wavelength.

  From the comparison between Table 1 and Table 2, it can be seen that the energy efficiency of the LED decreases and the emission wavelength also shifts as the temperature rises. Such a change accompanying the temperature rise is mainly caused by the material of the active layer and the cladding layer constituting the LED. Further, from Table 1, Table 2, FIG. 3 and FIG. 4, it can be seen that the wavelength shift and the energy efficiency decrease due to the temperature increase are particularly remarkable in the AlGaInP-based LED.

<Conventional example>
Next, a backlight device having a structure similar to that of the backlight device shown in FIG. 1 was manufactured using commercially available LEDs (power consumption per unit: 1 W or less). As the LEDs, 35 AlGaInP red LEDs, 70 AlGaInN green LEDs, and 35 AlGaInN blue LEDs were used. However, the backlight device produced here is different from the backlight device of FIG. 1 in that all LEDs correspond to one heat sink and dissipate heat, and corresponds to the conventional example. The drive current of each LED in this backlight device was fixed at 350 mA, and the luminance was adjusted by PWM modulation. In such a backlight device, the power consumption required for realizing a luminous flux of 5000 lm at room temperature is roughly estimated as shown in Table 3 below. Note that 5000 lm corresponds to the amount of backlight light necessary for a 30-inch class liquid crystal television.

  Next, the backlight device corresponding to the conventional example described above was actually operated. Immediately after the operation, that is, immediately after the lighting of the LED, the heat sink temperature gradually increased and finally exceeded 60 ° C. Further, the color of the backlight device immediately after the operation (room temperature) was white, but gradually changed to blue-green as time passed. As described above, the backlight device of the conventional example changes in light emission color during use and lacks stability.

  Further, in the conventional backlight device, a system that monitors the light output of each of the R, G, and B LEDs in real time was used to maintain a desired white point. As a result, the heat sink temperature gradually increased and eventually exceeded 60 ° C. The light output and power consumption of the backlight device at this time are shown in Table 4 below.

  As is apparent from the comparison between Table 3 and Table 4, in the conventional backlight device, as a result of maintaining the white color by using a system that monitors the light output of the R, G, and B color LEDs in real time, the red color is obtained. The power consumption of the LED is greatly increased compared to the other colors of LEDs. The reason why the power consumption of the red LED has greatly increased is that the red LED, which is most susceptible to temperature, is mounted on the same heat sink as the AlGaInN-based LED (green LED and blue LED) with the highest power consumption and heat generation. This is because the LED is heated and the efficiency of the red LED is reduced.

<Example 1>
Next, examples of the present invention will be described. In Example 1, a backlight device having the same structure as that of FIG. 1 was manufactured using the same kind and number of LEDs as in the conventional example. The backlight device of Example 1 is different from the conventional backlight device in that the green LED and the blue LED are radiated by the same heat sink and only the red LED is radiated by a heat sink different from the green LED and the blue LED. It is.

  The backlight device of Example 1 was actually operated under the same conditions as in the conventional example. The characteristics immediately after operation (room temperature) of the backlight device of Example 1 are shown in Table 5 below.

  Further, when the operation of the backlight device of Example 1 was maintained, the temperature of the heat sink corresponding to the green LED and the blue LED increased with time and exceeded 60 ° C., whereas the heat sink corresponding to the red LED. The temperature increased only to about 40 ° C.

  As in the case of the conventional example, in the backlight device of Example 1, control was performed to monitor the light output and maintain the white point. The characteristics of the backlight device of Example 1 at this time are shown in Table 6 below.

  In the backlight device of the conventional example, when the control to maintain the white point was performed, the power consumption of the red LED increased more than double compared to immediately after the operation (room temperature), whereas in the backlight device of Example 1, The increase in power consumption of the red LED was suppressed to about 40%.

  From Example 1 above, by mounting only red LEDs with low power consumption near room temperature on a heat sink different from other LEDs, it is possible to suppress the temperature rise of the red LEDs and reduce power consumption. Was confirmed.

<Example 2>
In Example 2, a backlight device having the same structure as that in FIG. 2 was manufactured using the same kind and number of LEDs as in the conventional example and Example 1. In the backlight device of Example 2, a heat sink is attached to a heat sink on which a red LED is mounted, and an air cooling fan is further attached. The backlight device of Example 2 was actually operated under the same conditions as in the conventional example and Example 1 while operating the air cooling fan to cool the heat sink on which the red LED was mounted. When the operation of the backlight device of Example 2 was maintained, the temperature of the heat sink on which the red LED was mounted was about 30 ° C., and the temperature increase was further suppressed. Further, as in the case of the conventional example and the first embodiment, the white point is controlled in the backlight device of the second embodiment. The characteristics of the backlight device of Example 2 at this time are shown in Table 7 below.

  As is clear from Table 7, in the backlight device of Example 2, the increase in power consumption of the red LED compared with immediately after the operation is about 20%, and the characteristic change of the red LED is further effectively suppressed. I understand that. Further, the backlight device of Example 2 was operated without monitoring the light output and maintaining the white point, and the light emission color of the backlight device at this time was observed. As a result, a decrease in the amount of change in the white point was observed as compared with the case where the same study was performed with the conventional backlight device. Therefore, it was confirmed that the backlight device of the present invention is excellent in hue stability.

It is a principal part schematic sectional drawing which shows an example of the backlight apparatus to which this invention is applied. It is a principal part schematic sectional drawing which shows the other example of the backlight apparatus to which this invention is applied. It is a characteristic view which shows the relationship between the temperature of LED, and external energy efficiency. It is a characteristic view which shows the relationship between the temperature of LED, and the peak wavelength of LED.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting device, 2 Reflection unit, 11 Light emitting element, 11R AlGaInP type light emitting element, 11G * 11B AlGaInN type light emitting element, 12 Heat sink, 13 Fin, 14 Air-cooling fan, 21 Light-shielding reflecting plate, 22 Reflecting plate, 23 Light guide color mixing plate , 24 Diffusion plate, 25 Housing, 26 Air passage, 27 Air inlet, 28 Air outlet, 29 Heat insulating material

Claims (7)

A plurality of types of light-emitting elements including at least an AlGaInP-based compound semiconductor light-emitting element, and a heat sink for dissipating heat generated from the light-emitting element provided corresponding to the light-emitting element, wherein the mounting surface of the light-emitting element is inclined from a horizontal plane A light emitting device,
The heat sink corresponding to the AlGaInP-based compound semiconductor light-emitting device and the AlGaInP-based compound semiconductor light-emitting device have a larger amount of heat generation than the other light-emitting devices that generate a larger amount of heat than the AlGaInP-based compound semiconductor light-emitting device and the AlGaInP-based compound semiconductor light-emitting device. A light emitting device characterized by being thermally independent from a heat sink corresponding to another light emitting element and disposed below.   2. The light emitting device according to claim 1, wherein the other light emitting element is an AlGaInN-based compound semiconductor light emitting element.   2. The light emitting device according to claim 1, wherein a heat sink corresponding to the AlGaInP-based compound semiconductor light emitting element is separated from a heat sink corresponding to the other light emitting element.   4. The light emitting device according to claim 3, further comprising a cooling device for forcibly cooling a heat sink corresponding to the AlGaInP-based compound semiconductor light emitting element.   The light-emitting device according to claim 4, wherein the cooling device controls the temperature of the heat sink while monitoring the temperature of the heat sink.   6. A backlight device for a liquid crystal display device, comprising the light emitting device according to claim 1 as a light source.   An illumination device comprising the light-emitting device according to claim 1.