JP2005276976A - Led source and led lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED lighting device which uses only one kind of LED chip. <P>SOLUTION: The LED source is provided with an LED chip which emits a first light, and a wavelength converter which includes a phosphor for absorbing at least one part of the first light and emitting a second light whose wavelength is longer than that of the first light. The dominant wavelength of the first light is set, so that the absolute value of the gradient (ΔK/Δλ) of the curve which represents the wavelength dependency of the internal quantum efficiency of a phosphor may be included in the wavelength range which becomes 1%/nm or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an LED (Light Emitting Diode) light source and an LED illumination device that can change the light color by controlling an input current.

  In the LED illumination device, (1) a type of device that obtains white illumination light by combining a plurality of types of LEDs having different emission wavelength ranges, and (2) a white light is obtained by combining one type of LED and a phosphor. It can be roughly divided into types of devices.

  In the case of an LED illumination light source including a first LED chip that emits a first color and a second LED chip that emits a second color (a color different from the first color), the magnitude of the current that drives each LED chip The light color can be changed by changing the length or switching the LED chip to emit light. Such an illuminating device is disclosed in Patent Document 1, for example.

  Hereinafter, a conventional LED lighting device described in Patent Document 1 will be described with reference to FIG. As is apparent from the equivalent circuit shown in FIG. 1, this device includes first LED chips 301a and 301b that emit light of a first color and second LED chips 302a and 302b that emit light of a second color. The LED chips 301a, 301b, 302a, and 302b constitute a diode bridge that is opposed to each other.

  A portion connecting the anode of the first LED chip 301a and the cathode of the second LED chip 302b is connected to the power input terminal 303A, and a portion connecting the anode of the second LED chip 302a and the cathode of the first LED chip 301b is the power input terminal 303B. It is connected to the. The cathode of the first LED chip 301a and the anode of the first LED chip 301b are connected via a resistor R.

  In the LED lighting device having such a configuration, when a positive potential is applied to the power input terminal 303A and a negative potential is applied to the power input terminal 303B, two first LED chips connected in series via the resistor R Since current flows through 301a and 301b, the first LED chips 301a and 301b emit light.

  Next, when a negative potential is applied to the power input terminal 303A and a positive potential is applied to the power input terminal 303B, current flows through the two second LED chips 302a and 302b connected in series via the resistor R. 2LED chips 302a and 302b emit light.

In the conventional LED lighting device having the configuration of FIG. 1, it is possible to change the light color of the illumination light by selectively emitting light of the two types of LED chips as described above.
Japanese Patent Laid-Open No. 6-188457 (see paragraph numbers 0011 to 0014, FIG. 1)

  However, in the conventional LED lighting device having the circuit configuration shown in FIG. 1, there are two types (a plurality of first LED chips 301a and 301b that emit a first color and second LED chips 302a and 302b that emit a second color). If the LED chip is not used, the light color cannot be changed. For this reason, this type of LED lighting device has the problems of high cost, difficulty in miniaturization, and a complicated driving circuit.

  The present invention is made in order to solve the above-mentioned problems, and an object of the present invention is to use one type of LED chip and easily change the light color by controlling the drive current. The object is to provide a lighting device.

  The LED light source of the present invention includes an LED chip that emits first light, and a phosphor that emits second light having a wavelength longer than that of the first light by absorbing at least a part of the first light. An LED light source including a wavelength conversion unit including a wavelength conversion unit including a wavelength conversion unit that includes an absolute value of a slope of a curve indicating the wavelength dependence of the internal quantum efficiency of the phosphor so as to be included in a wavelength range of 1 [% / nm] or more. The primary wavelength of the first light is set.

  In a preferred embodiment, the LED chip changes the dominant wavelength of the first light by 5 nm or more according to an input current.

  In preferable embodiment, the said wavelength conversion part contains 2 or more types of fluorescent substance containing the said fluorescent substance.

  In a preferred embodiment, the LED chip is mounted on a substrate in a flip chip state.

  In a preferred embodiment, the substrate has a wiring pattern connected to the anode and cathode of the LED chip.

  The LED illumination device according to the present invention is an LED illumination device including any one of the LED light sources described above and a color temperature variable unit that changes a color temperature of light emitted from the LED light source, and the color temperature variable unit. Shifts the dominant wavelength of the light emitted by the LED chip, and changes the color temperature of the light emitted from the LED light source.

  In a preferred embodiment, the color temperature varying means has a circuit that supplies a current for driving the LED chip of the LED light source to the LED chip, and the LED chip emits light by changing the magnitude of the current. Shift the dominant wavelength of the light to be transmitted.

  In a preferred embodiment, the color temperature variable means has a temperature adjusting element that changes the temperature of the LED chip, and shifts the dominant wavelength of light emitted by the LED chip by changing the temperature.

  In a preferred embodiment, the temperature adjustment element has a heat sink.

  In a preferred embodiment, the temperature adjusting element has a Peltier element.

  In a preferred embodiment, the color temperature varying means is an LED lighting device capable of shifting the main wavelength of the LED element by 5 nm or more.

  According to the present invention, by utilizing the wavelength dependence of the internal quantum efficiency of the phosphor, the luminous efficiency of the phosphor is changed by controlling the dominant wavelength of the excitation light, and the spectrum of the illumination light emitted from the LED illumination light source The distribution can be changed. For this reason, it is possible to provide a small LED lighting device that can change the color temperature with a simple drive circuit at low cost without using a plurality of types of LED chips having different main wavelengths.

  First, the basic configuration of the LED illumination light source according to the present invention will be described with reference to FIGS. 2 (a) and 2 (b). Fig.2 (a) has shown the cross-sectional structural example of the LED illuminating device by this invention, and FIG.2 (b) has shown the planar structural example.

  The LED lighting apparatus shown in the figure is an LED chip 101 that converts current into light, and wavelength conversion that absorbs part of the light emitted from the LED chip 101 and emits light having a wavelength longer than the wavelength of the absorbed light. And a substrate 103 that supports the LED chip 101 and the wavelength conversion unit 102. The substrate 103 has power input terminals 303 </ b> A and 303 </ b> B that apply current to the LED chip 101. The power input terminals 303A and 303B are connected to a drive circuit (lighting circuit).

  The LED chip 101 mounted on the substrate 103 is covered with a wavelength conversion unit 102 formed from a resin containing phosphor. The LED chip 101 is typically composed of a compound semiconductor element having a substantially rectangular parallelepiped shape, for example, several mm square. The wavelength converter 102 has a cylindrical shape that completely covers the side surface of the LED chip 101, for example, as shown in FIG.

  The LED chip 101 is preferably mounted on the substrate 103 by flip chip mounting. In this case, the anode and cathode electrodes (not shown) of the LED chip 101 are in contact with the electrodes on the substrate 103 and are fixed to the main surface of the substrate 103 via an adhesive layer.

  The substrate 103 is a substrate on which, for example, a wiring pattern layer is formed, and is manufactured using a glass epoxy substrate or a metal base having high heat dissipation.

  In the example shown in FIGS. 2A and 2B, one LED chip 101 is arranged on one substrate 103, but a plurality of LED chips 101 are integrated on one substrate 103. Also good. In that case, the wavelength conversion unit 101 may be provided so as to cover each LED chip separately, or one wavelength conversion unit may cover a plurality of LED chips.

  In a preferred embodiment of the present invention, by applying a positive potential to the power input terminal 303A and a negative potential to the power input terminal 303B by the circuit shown in FIG. 2B, the LED chip 101 emits light with an input current of 5 mA, for example. Let Then, LED chip 101 radiates | emits the light which has a dominant wavelength in 500 nm or less, for example. At this time, the phosphor of the wavelength conversion unit 102 covering the LED chip 101 is excited by at least a part of the light emitted from the LED chip 101, converted into light having a wavelength longer than the main wavelength, and emitted. . As a result, the light emitted from the LED chip 101 and the light (fluorescence) generated from the phosphor are mixed to form illumination light.

  Next, the variable principle of the color temperature in the LED lighting device of the present invention will be described.

FIG. 3 is a graph showing the excitation wavelength dependence of internal quantum efficiency in a typical YAG phosphor ((Y, Gd) ₃ Al ₅ O ₁₂ : Ce, cerium-doped yttrium / aluminum / garnet). The horizontal axis of FIG. 3 indicates the wavelength of the excitation light, and the vertical axis indicates the internal quantum efficiency. The “internal quantum efficiency” is a value indicating the ratio of the photon number of fluorescence to the photon number of excitation light absorbed by the phosphor. When the internal quantum efficiency for a certain wavelength is high, the intensity of fluorescence increases even if the intensity of the excitation light of that wavelength is the same.

As can be seen from FIG. 3, there is a region in which the internal quantum efficiency varies greatly depending on the wavelength of the excitation light. Here, consider the change in internal quantum efficiency when the wavelength is slightly changed from a certain wavelength λ. S = ΔK / Δλ indicates the “gradient” of the internal quantum efficiency at the wavelength λ, where Δλ is the amount of change in wavelength and ΔK is the change in internal quantum efficiency corresponding to this change.

  The gradient S in the region I (wavelength: 380 to 410 nm) in FIG. 3 is positive, but the gradient S in the region II (wavelength: 350 to 370 nm) is negative. In the present invention, the phosphor is excited with light having a dominant wavelength in a region where the absolute value of the gradient S is large, such as the region I or region II. That is, when the wavelength conversion unit 102 is formed of a phosphor having the characteristics shown in FIG. 3, if the main wavelength of the LED chip 101 can be changed by several nm, the photon number that is wavelength-converted by the phosphor increases. Since it changes, it becomes possible to change the light color of illumination light in a wide range.

In a normal LED illumination light source, since the light emission efficiency (lm / W) is most important, the phosphor is developed and adjusted so that its internal quantum efficiency is the highest. Therefore, when an LED illumination device is manufactured using a YAG phosphor ((Y, Gd) ₃ Al ₅ O ₁₂ : Ce) having an internal quantum efficiency characteristic as shown in FIG. 3, the main wavelength is set to 470 nm, for example. Such LED chip is adopted.

  Contrary to such conventional technical common sense, in the present invention, an excitation wavelength range in which the internal quantum efficiency of the phosphor greatly varies depending on the wavelength is used positively. More specifically, an excitation wavelength region in which the internal quantum efficiency of the phosphor changes by 5% or more with respect to an excitation wavelength change of 5 nm is used. That is, a region where the absolute value of the slope S [unit:% / nm] of the curve indicating the excitation wavelength dependence of the internal quantum efficiency is 1 [% / nm] or more is used. The larger the absolute value of the gradient S, the greater the change in internal quantum efficiency can be caused by slightly changing the dominant wavelength of light emitted from the LED chip. For this reason, the preferable lower limit of the absolute value of the gradient S is 2 [% / nm], and the more preferable lower limit is 3 [% / nm].

  Next, a method for changing the wavelength of excitation light applied to the phosphor will be described with reference to FIGS.

FIG. 4 is a graph showing how the spectrum of light emitted from an In _x Ga _1-x N-based blue LED chip changes depending on the input current. The vertical axis of the graph is the light intensity, and the horizontal axis is the wavelength. The input current is changed in 12 steps from 10 μA (microampere) to 50 mA (milliampere). The surface temperature of the LED chip is kept at 25 ° C. so that the temperature of the LED chip does not change due to the change of the input current. That is, the graph of FIG. 4 shows the current dependence of the dominant wavelength when the temperature of the LED chip is constant.

  As can be seen from FIG. 4, when the input current is in the range of 10 μm to 5 mA, the main wavelength of the LED chip hardly changes, but when the input current is increased from 5 mA to 50 mA, the main wavelength of the LED chip is shortened by about 5 nm. Can do. In this way, when the chip temperature is kept constant, the dominant wavelength shifts to the short wavelength side due to the increase of the injection current.

  On the other hand, FIG. 5 is a graph showing a synchrotron radiation spectrum when the input current is 20 mA and 80 mA without keeping the LED chip temperature constant. The main wavelength of the LED chip is shifted to the long wavelength side by about 5 nm by increasing the injection current from 20 mA to 80 mA. This shift direction is opposite to that shown in FIG. This shift occurs because the chip temperature is increased by increasing the current from 20 mA to 80 mA, and the cause is different from the shift shown in FIG.

  As is clear from the above description, the main wavelength of light emitted from the LED chip can be increased or decreased by 5 nm or more by adjusting the input current and temperature of the LED chip. Even if the spectral distribution of the light emitted from the LED chip is slightly changed, the light color of the illumination light can be controlled in a wide range by using the wavelength range in which the gradient of the internal quantum efficiency change of the phosphor is large. It becomes possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
Reference is first made to FIG. FIG. 6 shows a cross-sectional configuration of the first embodiment of the LED lighting device according to the present invention.

  The illustrated LED light source includes an LED chip 101 that converts current into light, and a wavelength conversion unit 102 that absorbs part of the light emitted from the LED chip 101 and emits light having a wavelength longer than the excitation light wavelength. And a substrate 103 that supports the LED chip 101 and the wavelength conversion unit 102. The substrate 103 has power input terminals 303A and 303B for supplying current to the LED chip 101. In the present embodiment, a reflector 601 having an opening surrounding the LED chip 101 and the wavelength conversion unit 102 is provided on the substrate 103. The opening of the reflecting plate 601 has an inner wall surface that is inclined in a concave shape, and this inner wall surface functions as a reflecting surface. The power input terminals 303A and 303B are connected to a circuit (not shown) that adjusts the current flowing through the LED chip 101.

  As the LED chip 101, it is preferable to use a small rectangular shape that can be easily mounted by a flip chip method. Specifically, it is preferable to use a chip having a side length of about 0.3 mm to 2 mm. The size of the LED chip 101 used in this embodiment is, for example, 0.3 mm × 0.3 mm × thickness 1 mm. As will be described later, the LED chip 101 is a blue-violet LED element having a dominant wavelength of 390 nm at an input current of 5 mA.

The wavelength conversion unit 102 is preferably formed of a columnar resin and covers the periphery of the LED chip 101. In the present embodiment, the phosphor of the wavelength conversion unit 102 is a YAG phosphor ((Y, Gd) ₃ Al ₅ O ₁₂ : Ce), and the wavelength dependence of the internal quantum efficiency is as shown in FIG. . The wavelength changing unit 102 of this embodiment can be formed by, for example, a screen printing method. In this case, a phosphor paste made of a resin material or the like is applied onto a metal mask (stencil plate) by a member such as a squeegee, and a resin portion having a shape defined by a hole provided in the metal mask is formed on an arbitrary surface on the substrate 103. Can be formed in position. The weight ratio of the phosphor contained in the resin paste is adjusted to, for example, about 15 to 85%.

  The substrate 103 of this embodiment is formed from a glass epoxy substrate. For example, the substrate 103 has a thickness of 1 mm and a planar size of 5 mm square. The size of the substrate 103 is set to an arbitrary size depending on the application. A substrate of several centimeters to several tens of centimeters may be used so that a large number of LED chips can be mounted.

  The reflection plate 601 is formed from a metal plate (thickness of about 1 mm) such as aluminum and bonded to the main surface of the substrate 103. The reflection plate 601 reflects light emitted in the horizontal direction out of the light emitted from the LED chip 101 and the phosphor 102 and deflects it in the direction in which the illumination object is located. Thereby, the light extraction efficiency is improved. Note that the opening of the reflecting plate 601 may be filled with another resin. If a lens shape is given to the resin, the light collection rate can be further increased.

  The power input terminals 303A and 303B on the substrate 103 are respectively connected to the anode and cathode of the LED chip 101 as shown in FIG. The power input terminals 303A and 303B are each connected to a drive circuit (color temperature varying means). The magnitude of the current flowing through the LED chip 101 is controlled to an arbitrary level within a predetermined range by adjusting the potential difference applied to the power input terminals 303A and 303B by the drive circuit.

  Hereinafter, the operation of the LED lighting device shown in FIG. 6 will be described.

  When a positive potential is applied to the power input terminal 303A and a negative potential is applied to the power input terminal 303B by the drive circuit, a current flows between the anode and the cathode of the LED chip 101. Due to this current, charges (electrons and holes) are injected into the active layer of the LED chip 101, so that light generated by recombination is emitted from the LED chip 101. Light having a spectrum shown in FIG. 8 is emitted from the LED chip 101 used in this embodiment. The vertical axis of the graph of FIG. 8 is the relative energy (%) of the emitted light, and the horizontal axis is the wavelength (nm). As can be seen from FIG. 8, the light emitted from the LED chip 101 has a dominant wavelength at 390 mm (input current: 5 mA).

  Since the light emitted from the LED chip 101 has a spectrum as shown in FIG. 8, the phosphor of the wavelength conversion unit 102 is mainly excited by light having a wavelength of 390 mm and has a wavelength longer than the main wavelength of the LED chip 101. Fluoresce. As shown in FIG. 3, the internal quantum efficiency of the phosphor in the present embodiment exhibits an internal quantum efficiency of about 30% at and around the wavelength of 390 nm, and the gradient S is about +3 [% / nm]. From this phosphor, yellow light having a peak at 570 nm is emitted.

  As a result of mixing of the light emitted from each of the LED chip 101 and the phosphor 102, the illumination light has a spectral distribution having two peaks as shown in FIG. The vertical axis of the graph of FIG. 9 is the relative energy (%) of the illumination light, and the horizontal axis is the wavelength (nm).

  Next, the magnitude of the input current is increased from 5 mA to 40 mA while applying a positive potential to the power input terminal 303A and a negative potential to the power input terminal 303B. Then, the magnitude of the current flowing through the LED chip 101 increases, causing a change in the emission wavelength. FIG. 10 shows a spectrum of light emitted from the LED chip 101 when the input current is 40 mA. As can be seen from FIG. 9, the dominant wavelength is 395 nm, an increase of 5 nm compared to the dominant wavelength (390 nm, FIG. 8) when the input current is 5 mA.

  The phosphor of the wavelength conversion unit 102 is excited mainly by light having a wavelength of 395 mm, and emits fluorescence having a longer wavelength than the main wavelength of the LED chip 101. As shown in FIG. 3, the internal quantum efficiency of the phosphor of the present embodiment exhibits an internal quantum efficiency of about 45% at a wavelength of 395 nm and in the vicinity thereof.

  As a result of mixing the light emitted from each of the LED chip 101 and the phosphor 102, the illumination light has a spectral distribution having two peaks as shown in FIG. Comparing the spectral distribution of FIG. 11 with the spectral distribution of FIG. 9, it can be seen that as the input current increases from 5 mA to 40 mA, the relative energy of emission at a wavelength of 570 nm increases by about 10%. As a result, the color temperature of the illumination light changes significantly. That is, by changing the input current from 5 mA to 40 mA, the light component in the wavelength region where the internal quantum efficiency of the yellow phosphor is high increases, so the proportion of yellow light emitted from the phosphor increases, and the color temperature Will drop.

  As described above, in the LED lighting device of the present embodiment, the relative energy of the fluorescence emitted from the phosphor can be greatly changed by adjusting the input current and slightly shifting the emission wavelength of the LED chip. . This is realized for the first time by actively using a region in which the internal quantum efficiency of the phosphor greatly varies depending on the wavelength.

  In this embodiment, an LED having a dominant wavelength of 390 nm is used as the LED chip 101. However, the present invention is not limited to this, and an LED element having a dominant wavelength in the range of 310 nm to 440 nm is used. Can do. However, when the LED chip 101 that emits blue light is used, it is preferable to use an LED chip having a dominant wavelength of light emission of about 440 nm. On the other hand, when blue is supplemented with fluorescence, the dominant wavelength of the LED chip 101 may be in the ultraviolet region, for example, in the range of 310 nm to 420 nm.

  The phosphor 102 is not necessarily a YAG phosphor having a main wavelength of 570 nm, and may be another phosphor having a main wavelength in the range of 540 to 600 nm.

  In the present invention, the relative energy of the light emitted from the phosphor is greatly changed by shifting the main wavelength of the light emitted from the LED chip by 5 nm. For this reason, it is preferable that the gradient (wavelength dependence) of the internal quantum efficiency of the phosphor is large in the vicinity of the main wavelength. In the present embodiment, the main wavelength of the LED chip is adjusted to a wavelength region having a gradient of 5 [% / nm], and this gradient is preferably 7 [% / nm] or more, and 10 [% / nm]. nm] or more.

  In the above embodiment, the light color change in the case where the input current is increased has been described. However, the light color can be changed in reverse by decreasing the input current. In addition, when an LED chip having a dominant wavelength in the negative wavelength range is used instead of the slope of the curve shown in FIG. 3, if the dominant wavelength is increased by increasing the current, the yellow light emitted from the phosphor is increased. Since the ratio decreases, it is possible to realize a light color change opposite to that of the above-described embodiment. In this way, when the main wavelength of the light emitted from the LED chip is increased by increasing the input current, the ratio of the yellow light emitted from the phosphor of the wavelength conversion unit is reduced. The color temperature can be increased in a region where the luminous efficiency increases.

(Embodiment 2)
A second embodiment of the LED lighting device according to the present invention will be described with reference to FIG. FIG. 12 shows the internal quantum efficiency of a phosphor having characteristics different from those shown in FIG.

  The LED lighting device of the present embodiment has a configuration similar to the configuration shown in FIG. 6. The difference between the present embodiment and the first embodiment is that the main wavelength is 490 nm (input) in this embodiment. The blue LED chip 101 having a current of 5 mA) is used, and the phosphor of the wavelength conversion unit 102 has the internal quantum efficiency characteristics shown in FIG. As is apparent from the graph of FIG. 12, when the excitation wavelength is 490 nm or more, the internal quantum efficiency of this phosphor decreases rapidly.

  In the present embodiment, when the input current is 5 mA, light having a dominant wavelength is emitted from the LED chip 101 to 490 mm. The wavelength converter 102 covering the periphery of the LED chip 101 emits fluorescence having a peak at 570 nm when excited mainly by light of 490 mm.

  When the input current increases to 40 mA, the dominant wavelength of the light emitted from the LED chip 101 is shifted from 490 nm to 495 mm. Compared to illumination light when the input current is 5 mA, the relative energy of light having a wavelength of 570 nm is reduced by 15% in the illumination light when the input current is 40 mA. As a result, the color temperature of the illumination light is significantly increased. That is, by increasing the input current from 5 mA to 40 mA, the yellow fluorescence is reduced and the color temperature is increased.

  As described above, according to the LED illumination device of the present embodiment, the LED chip using the phosphor having the internal quantum efficiency characteristics as shown in FIG. 12 and having the main wavelength in the portion where the internal quantum efficiency has a large gradient. By adopting, the light color can be adjusted only by the change of the input current. In the present embodiment, the color temperature can be increased when the current for driving the LED chip is increased, and it can be preferably used as an LED illumination light source. That is, the illumination light that was yellow and white at low currents (when dark), and bluish white at high currents (when bright), the tendency of humans to feel uncomfortable (Klinnikov's pleasant / uncomfortable curve) The change of the light color according to the above can be realized.

  In the present embodiment, an LED having a dominant wavelength of 490 nm is used as the LED chip 101, but the present invention is not limited to this. When using the phosphor showing the internal quantum efficiency as shown in FIG. 12, an LED chip having a dominant wavelength in the range of 480 nm to 520 nm can be used. Further, the phosphor is not limited to the phosphor showing the internal quantum efficiency as shown in FIG. 12, and other phosphor materials may be used as long as the phosphor has a main wavelength of 540 to 600 nm.

(Embodiment 3)
FIG. 13 shows a third embodiment of the LED lighting device according to the present invention.

  In this embodiment, the LED chip 101 is a normal chip, and the power input terminals 303A and 303B are constituted by lead frames. The power input terminal 303B and the LED chip 101 are electrically connected by a wire 1201. Furthermore, the LED chip 101 is fixed inside a cup-shaped reflector 601 and is covered with a wavelength conversion unit 102 made of a resin containing a phosphor. The LED chip 101 and the cup-shaped reflector 601 are completely covered with a mold resin 1202 having a lens function.

  Although the LED lighting device of this embodiment is a bullet type, the main wavelength of the light radiated | emitted can be shifted by the increase in input current similarly to Embodiment 1. FIG. However, since the structure has a lead frame, heat dissipation is poor, and heat generated by the LED chip 101 is not quickly released to the outside. As a result, when the input current is increased, the temperature of the LED chip 101 is likely to rise, and the main wavelength of the light emitted from the LED chip is easily shifted to the longer wavelength side. Thus, the color temperature of the illumination light can be changed in the present embodiment as in the first embodiment.

(Embodiment 4)
FIG. 14 shows a fourth embodiment of the LED lighting device according to the present invention.

  The configuration of the present embodiment is different from the configuration of the second embodiment in that a means for adjusting the temperature of the LED chip 101 is provided. That is, the LED light source of the present embodiment includes a heat sink 1301 that is in contact with the back surface of the substrate 103 as shown in FIG. 14, and has a mechanism that promotes heat dissipation of the heat sink 1301 by cold air (atmospheric atmosphere at room temperature). Yes. The substrate 103 is also formed from a metal composite substrate having excellent thermal conductivity.

  The LED chip 101 and the wavelength conversion unit 102 in the present embodiment have the same configuration as the LED chip 101 and the wavelength conversion unit 102 in the first embodiment.

  According to the configuration of the present embodiment, even if the LED chip 101 generates heat as the input current increases, the heat flows to the heat sink 1301 via the metal composite substrate 103 having high thermal conductivity and is quickly dissipated. . The heat sink 1301 is cooled by cold air, and the temperature of the LED chip 101 is kept at room temperature (25 ° C.).

  According to the LED illumination device having such a configuration, the emission spectrum of the LED chip 103 is hardly affected by heat and changes depending only on the magnitude of the input current. When the input current is increased with the chip temperature kept constant, the dominant wavelength of light emitted from the LED chip tends to shift to the short wavelength side as described above.

  In this embodiment, when a positive potential is applied to the power input terminal A and a negative potential is applied to the power input terminal B, when the input current is set to 5 mA, the LED chip 101 emits light having a dominant wavelength at 390 mm. However, when the input current is increased from 5 mA to 40 mA, the dominant wavelength of the light emitted from the LED chip is shortened from 390 nm to 385 mm as shown in FIG.

  For this reason, when the input current is 5 mA, the phosphor of the wavelength converter 102 is mainly excited by light of 390 mm and emits yellow light having a main wavelength of 570 nm. However, when the input current is increased from 5 mA to 40 mA, the wavelength conversion is performed. The phosphor of the unit 102 is mainly excited by light of 385 mm and emits yellow light having a main wavelength of 570 nm. The internal quantum efficiency of the phosphor when the wavelength is 390 nm is about 30%, whereas the internal quantum efficiency of the phosphor when the wavelength is 385 nm is about 10%. The intensity of fluorescence emitted from the phosphor changes due to the shift of the dominant wavelength. Since the light emitted from the LED chip 101 and the light emitted from the phosphor 102 are superimposed to form illumination light, the light color of the illumination light changes due to the change in the ratio of fluorescence.

  In this embodiment, the relative energy of light at a wavelength of 570 nm is reduced by about 10% by increasing the input current, and the color temperature can be greatly increased. As described above, in the present embodiment, while using the LED chip and the phosphor in the first embodiment, not only the input current but also the chip temperature is controlled to provide illumination light according to the Krynikov comfort / discomfort curve. be able to.

  The method for controlling the temperature of the LED chip 101 is not limited to the above method. The temperature of the LED chip 101 and / or the substrate 103 may be adjusted with high accuracy using a Peltier element.

(Embodiment 5)
FIG. 15 shows a fifth embodiment of the LED lighting device according to the present invention.

  The configuration of the present embodiment is different from the configuration of the second embodiment in that the second phosphor 1401 of the wavelength conversion unit 102 is mixed. The dominant wavelength of fluorescence emitted by the second phosphor 1401 used in this embodiment is 420 to 480 nm.

  The main wavelength of light emitted from the LED chip 101 is set in the range of 310 nm to 430 nm. Therefore, the blue light emission is not the light emission of the LED chip 101 but is supplemented by using the second phosphor 1401.

  When the first phosphor of the wavelength converter 102 is a YAG phosphor, the light emitted from the YAG phosphor has a small blue light component. For this reason, when the LED chip 101 having the dominant wavelength in the above wavelength range is used, the light color of the illumination light becomes yellowish and greatly deviates from the black body locus only with the YAG phosphor.

  In this embodiment, the light color is adjusted by additionally using the second phosphor 1401. It is preferable that the main wavelength of light emitted by the second phosphor 1401 is adjusted to be within a range of 420 to 480 nm.

  As shown in FIG. 16, the addition of the third phosphor 1501 having a fluorescence dominant wavelength in the range of 600 to 700 nm further increases the degree of freedom in adjusting the light color and color rendering.

  As can be seen from the above description, an LED illumination device having various characteristics can be realized depending on the type of phosphor and the presence or absence of a temperature control mechanism.

  Table 1 below shows the presence / absence of the temperature control mechanism, the main wavelength shift, the quantum efficiency of the phosphor, and the like for the examples (samples 1 to 5) and the comparative example (sample 6) of the present invention.

  Samples 1 to 3 in Table 1 are obtained by mounting a substrate on which an LED chip is mounted on a small heat sink. On the other hand, samples 4 to 6 are obtained by providing a Peltier element on a substrate on which an LED chip is mounted. In Samples 1 to 3, when the input current is increased, the temperature rise due to heat generation of the LED chip cannot be prevented, and the chip temperature rises. On the other hand, in Samples 4 to 6, the chip temperature can be maintained at about room temperature by the action of the Peltier element. For this reason, there is a difference in the behavior of whether the main wavelength at high current (40 mA) becomes longer or shorter than the main wavelength at low current (5 mA). Table 1 shows the dominant wavelengths at low current and high current. Due to the increase in current, in samples 1 to 3, the dominant wavelength is increased by 5 nm, while in samples 4 to 6, the dominant wavelength is decreased by 5 nm. In said samples 1-6, LED chip is covered with the wavelength conversion part containing the yellow fluorescent substance which shows the internal quantum efficiency of FIG. In Samples 1, 2, 4, and 5, in addition to this yellow phosphor, a blue phosphor having an internal quantum efficiency shown in FIG. 17 is added to the wavelength converter. Since the internal quantum efficiency of the blue phosphor has wavelength dependency as shown in FIG. 17, it increases or decreases as shown in Table 1 below due to the shift of the main wavelength. In Table 1, “Up” means that the internal quantum efficiency increases with the main wavelength shift shown in Table 1, and “Down” means that the internal quantum efficiency decreases. In sample 6 as a comparative example, the dominant wavelength is 430 nm, and therefore the change in quantum efficiency of the yellow phosphor using this light as excitation light is smaller than in the example.

  Table 2 shows the light color of the light emitted from the LED illumination device (mixed light of the LED chip and the fluorescent light) when the injection current is increased from 5 mA to 40 mA for the samples 1 to 6 having the above-described configuration. Is shown (the light color when the injection current is 5 mA is “white”). The rightmost column of Table 2 shows the psychological pleasure and discomfort that a person feels from the illumination light with changes in brightness and light color. In the table, “◯” indicates a comfortable case, and “Δ” indicates a case that is neither pleasant nor unpleasant.

  Table 3 shown below shows changes in color temperature and the like in the case of samples B1 to B4 when the main wavelength of light emitted from the LED chip is shifted by increasing the input current from 5 mA to 40 mA. Sample A shows the color temperature and the like when the input current is 5 mA. When the input current is 5 mA, the dominant wavelength of the light emitted from the LED chip is 310 nm, and the color temperature of the illumination light (LED light + yellow fluorescence + red fluorescence) obtained from Sample A is 5960K (light color is white). .

  Sample B1 shows data when the input current is increased from 5 mA to 40 mA in the LED illumination light source having the same structure as Sample A. The main wavelength of light emitted from the LED chip when the input current is 40 mA is 315 nm. In sample B1, the internal quantum efficiency of the yellow phosphor at the main wavelength of 315 nm is reduced to 91.76% of the value in sample A. ing. Further, the internal quantum efficiency of the blue phosphor at the main wavelength of 315 nm is increased to 101.55% of the value in the sample A. As a result of the shift of the dominant wavelength in this way, the color temperature of the illumination light of the sample B1 rises to 6992K (light color is bluish white), and the color temperature difference becomes 1032K.

  Unlike the samples A and B1, the samples B2 to B4 are the results of calculating how the color temperature and the like change when the internal quantum efficiency changes greatly as shown in Table 3. As can be seen from Table 3, when the internal quantum efficiency of the phosphor changes by ± 10% with respect to the value in Sample A in accordance with the main wavelength change (5 nm change) of the LED chip, the color temperature is 1000 K with respect to the reference value. Increase or decrease.

  As described above, by appropriately combining phosphors having various characteristics, it is possible to control the light color of the illumination light over a wide range only by changing the wavelength of the light emitted from the LED chip by about 5 nm. In addition, the kind of fluorescent substance used for the wavelength conversion part 102 is not limited to 1-3 types, Four or more types may be sufficient.

  The LED illumination device of the present invention is useful as a general illumination device because it can change the light color of illumination light using one type of LED chip.

It is an equivalent circuit diagram of a conventional LED lighting device capable of adjusting the color temperature. (A) is sectional drawing which shows the structure of the LED lighting apparatus by this invention, (b) is the top view. It is a graph which shows the wavelength dependence of the internal quantum efficiency of a YAG fluorescent substance. It is a grab which shows the main wavelength of light emission of the LED chip with respect to input current. It is a grab which shows the main wavelength of light emission of the LED chip with respect to the heat_generation | fever by input current. It is sectional drawing which shows the LED lighting apparatus in Embodiment 1 of this invention. 7 is an equivalent circuit of the embodiment shown in FIG. 6. It is a graph which shows the spectral distribution of light emission of the LED chip which has a dominant wavelength in 390 nm. In Embodiment 1, it is a graph which shows the spectral distribution of light emission of an LED illuminating device when an input electric current is 5 mA. It is a graph which shows the spectral distribution of light emission of the LED chip which has a dominant wavelength in 395 nm. In Embodiment 1, it is a graph which shows the spectral distribution of light emission of an LED illuminating device when input current is 40 mA. It is a graph which shows the wavelength dependence of the internal quantum efficiency of the fluorescent substance in Embodiment 2 of this invention. It is sectional drawing which shows the LED lighting apparatus in Embodiment 3 of this invention. It is sectional drawing which shows the LED lighting apparatus in Embodiment 4 of this invention. It is sectional drawing which shows the LED lighting apparatus in Embodiment 5 of this invention. The figure which shows the cross section of the LED lighting apparatus in Embodiment 6 of this invention. It is a graph which shows the wavelength dependence of the internal quantum efficiency of a blue fluorescent substance.

Explanation of symbols

101 LED chip 102 Wavelength conversion unit 103 Substrate 301a First LED chip 301b First LED chip 302a Second LED chip 302b Second LED chip 303A Power input terminal A
303B Power input terminal B
601 Reflector 1201 Wire 1202 Mold resin 1301 Heat sink 1302 Cold air 1401 Second phosphor 1501 Third phosphor

Claims (11)

An LED chip that emits first light; and a wavelength conversion unit that includes a phosphor that absorbs at least a part of the first light and emits second light having a longer wavelength than the first light. An LED light source comprising:
The primary wavelength of the first light is set such that the absolute value of the slope of the curve indicating the wavelength dependence of the internal quantum efficiency of the phosphor is included in a wavelength range of 1 [% / nm] or more. light source.   The LED light source according to claim 1, wherein the LED chip changes a dominant wavelength of the first light by 5 nm or more according to an input current.   The LED light source according to claim 1, wherein the wavelength conversion unit contains two or more kinds of phosphors including the phosphor.   The LED light source according to claim 1, wherein the LED chip is mounted in a flip chip state on a substrate.   The LED light source according to claim 4, wherein the substrate has a wiring pattern connected to an anode and a cathode of the LED chip. LED light source according to claims 1 to 5,
Color temperature variable means for changing the color temperature of light emitted from the LED light source;
An LED lighting device comprising:
The color temperature varying unit is an LED lighting device that shifts a main wavelength of light emitted from the LED chip and changes a color temperature of light emitted from the LED light source. The color temperature varying means has a circuit for supplying a current for driving the LED chip of the LED light source to the LED chip,
The LED lighting device according to claim 6, wherein a main wavelength of light emitted from the LED chip is shifted by changing a magnitude of the current. The color temperature variable means has a temperature adjusting element that changes the temperature of the LED chip,
The LED lighting device according to claim 6 or 7, wherein a main wavelength of light emitted from the LED chip is shifted by changing the temperature.   The LED lighting device according to claim 6, wherein the temperature adjustment element has a heat sink.   The LED lighting device according to claim 6, wherein the temperature adjustment element includes a Peltier element.   The LED illumination device according to any one of claims 6 to 10, wherein the color temperature varying means can shift the dominant wavelength of the LED element by 5 nm or more.