JP2006261554A - Light emitting diode device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-luminance light emitting diode device where an uniform color balance is easily set and an unevenness of emitted light is eliminated. <P>SOLUTION: The light emitting diode device mixes the light emitted from a plurality of phosphors, and includes a light emitting diode emitting a primary light and a wavelength conversion portion which absorbs the primary light to emit a secondary light and contains a plurality of phosphor layers. The wavelength conversion portion includes a first phosphor layer to which the primary light emitted from the light emitting diode is incident first, and a second phosphor layer to which the primary light transmitting through the first phosphor layer is incident. The band gap energy that the phosphor of the second phosphor layer has is larger than the energy of peak wavelength the second light emitted from the first phosphor layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting diode device, and more particularly to a light emitting diode device including a light emitting diode element and two or more kinds of phosphors.

  As a next-generation light-emitting diode device that is expected to have low power consumption, small size, and high brightness, the development of a light-emitting diode device comprising a nanocrystalline phosphor and a light source that emits primary light that excites the phosphor is actively developed. Has been done. The use of nanocrystals for the phosphor is expected to improve the light emission efficiency as compared with conventional phosphors. Furthermore, since such a nanocrystal has a broad absorption band width compared to the absorption band width (energy width) required to excite a conventional phosphor, the tolerance for the wavelength width of the light source is high. Therefore, a semiconductor light emitting element or the like can be used as the light source. Examples of such light emitting diode devices include the following Patent Documents 1 and 2.

Patent Document 1 discloses a surface-mount type light-emitting diode device represented as a whole by 50 as shown in FIG. In the light emitting diode device 50, the blue light emitting diode chip 52 is die-bonded on the substrate 51 on which the circuit wiring 51a is formed by etching or the like, and the blue light emitting diode chip 52 is wired to the circuit wiring 51a by a gold wire. . Further, a lens holder 53 provided with a substantially cone-shaped recess 53 a is attached to the substrate 51 so as to surround the blue light emitting diode chip 52. A transparent resin such as an epoxy resin mixed with the YAG phosphor 54a is injected into the recess 53a by means of a potting mold or the like, and is thermally cured to form the lens 54.
In the light-emitting diode device 50, the blue light-emitting diode chip 52 is turned on to excite the YAG phosphor 54a composed of (Y, Gd) ₃ Al ₅ O ₁₂ : Ce by the emitted light having a wavelength of about 430 to 480 nm. Thus, yellow light having a wavelength of around 570 nm is emitted, and finally, white light (see spectrum curve B in FIG. 3) is obtained as a composite color.

Patent Document 2 discloses a light-emitting diode device including a wavelength conversion unit having a white phosphor mixed with a blue phosphor made of nanocrystals, and a light source that excites the wavelength conversion unit.
Japanese Patent No. 3428597 JP 11-340516 A

However, in the light emitting diode device 50 shown in Patent Document 1, peaks occur at wavelengths near 465 nm and 560 nm, and white light is obtained visually. However, when the spectrum distribution is verified, the red region has a wavelength of 620 nm or more. The output is relatively weak.
This means that when the light-emitting diode device 50 is used as illumination for a backlight light source of a color liquid crystal display, for example, red tends to be dark and color rendering is poor. Further, when the lens 54 is formed, the phosphor 54a having a high specific gravity is likely to be precipitated, causing a problem of color unevenness at the time of lighting, and that the lens 54 is yellowed in a relatively short time due to ultraviolet rays from the blue light emitting diode chip 52. There are also problems.

  On the other hand, in the light-emitting diode device described in Patent Document 2, white light is emitted by mixing red, green, and blue phosphors. Therefore, in order to obtain uniform white light, the entire region serving as the wavelength conversion unit is uniform. In addition, red, green, and blue phosphors must be mixed together, which makes it difficult to manufacture. When a green or red phosphor is formed on the blue phosphor, blue light emitted from the blue phosphor is absorbed by the green or red phosphor, and green light or red light is emitted. Similarly, when the red phosphor is formed on the green phosphor, the green light emitted from the green phosphor is absorbed by the red phosphor and the red light is emitted. As a result, the color balance of the light emitting diode device deviates from the set color, causing a problem that the luminance with respect to the set color is lowered.

  In view of the above problems, an object of the present invention is to provide a light emitting diode device that can easily set a color balance and has high luminance and eliminates uneven light emission.

  That is, the present invention is a light emitting diode device that mixes light emitted from a plurality of phosphors, a light emitting diode element that emits primary light, and a plurality of fluorescent light that absorbs primary light and emits secondary light. A wavelength conversion unit including a body layer, wherein the wavelength conversion unit includes a first phosphor layer on which primary light emitted from the light emitting diode first enters and a second light on which primary light transmitted through the first phosphor layer enters. A light emitting diode device comprising: a phosphor layer, wherein a band gap energy of a phosphor of the second phosphor layer is larger than an energy of a peak wavelength of secondary light emitted from the first phosphor layer. is there.

  Thus, according to the present invention, since the secondary light emitted from the first phosphor layer is not absorbed by the second phosphor layer, the secondary light has high brightness, no bias, and easy balance adjustment. Is obtained. As a result, it is possible to provide a high-intensity light-emitting diode device that can easily set the color balance and has no color unevenness.

  FIG. 1 is a cross-sectional view of the light emitting diode device according to the present embodiment, indicated as a whole by 10. The light emitting diode device 10 includes a semiconductor substrate 1 made of, for example, silicon. On the semiconductor substrate 1, a light emitting diode element 2 and a lens holder 3 provided with a substantially cone-shaped recess 4 so as to surround the light emitting diode element 2 are attached. In the lens holder 3, a wavelength conversion unit 8 and a lens unit 9 are provided. The lens unit 9 is made of, for example, an epoxy resin. The wavelength conversion unit 8 includes a red phosphor 5, a green phosphor 6, and a blue phosphor 7, absorbs at least part of the primary light emitted from the light emitting diode element 2, and is longer than the peak wavelength of the primary light. Secondary light having a peak wavelength is emitted.

As the light emitting diode element 2, for example, a GaN light emitting diode having a peak wavelength at 465 nm, a ZnO light emitting diode, a diamond light emitting diode, or the like is used.
Further, for the phosphors 5 to 7, InN-based nanocrystals can be used. There are theories that InN has a band gap of 2.05 eV in the bulk structure and the theory that it has a band gap of 0.6 to 0.8 eV. In either case, the particle size is small ( When nanocrystallization is performed, the band gap can be controlled in the range from blue to red by the quantum effect.

  Here, the “nanocrystal” refers to a crystal in which confinement of excitons and increase in band gap due to the quantum size effect are observed by reducing the crystal size to about the exciton Bohr radius. Specifically, a spherical portion made of a material having a small band gap is covered with a covering portion made of a material having a large band gap.

The wavelength conversion unit 8 has a red phosphor 5 having a particle size that emits red light, and a red phosphor 5 that is an InN-based nanocrystal having the largest particle size; The green phosphor 6 and the blue phosphor 7 which is an InN-based nanocrystal having the smallest particle size and emitting blue light are laminated in an acrylic resin.
These phosphors 5 to 7 are stacked with a red phosphor 5, a green phosphor 6, and a blue phosphor 7 in the order close to the light emitting diode element 2 that is a light source. As materials for the phosphors 5 to 7, in addition to InN, materials such as Si, Zn _1-x Cd _x Se, or the like that have at least an absorption band in the blue to near-ultraviolet region in bulk can be used.

  Such phosphors 5 to 7 having different particle sizes can be produced by a chemical synthesis method, an ion implantation method, or the like. In addition, the wavelength conversion part 8 is not only the one in which the phosphors 5 to 7 are directly stacked, the one in which the phosphors 5 to 7 are directly stacked is embedded with silicon resin, or the phosphors 5 to 7 are not only silicon resins. It can be formed from those embedded in other organic or inorganic materials.

  In the light emitting diode device 10, the wavelength conversion unit 8 is mixed in the recess 4, a transparent resin such as an epoxy resin is injected by means such as potting mold, and thermosetting is performed to form the lens unit 9.

As described above, the phosphors 5 to 7 are laminated with the red phosphor 5, the green phosphor 6, and the blue phosphor 7 in the order close to the light emitting diode element 2 that is a light source (in the order of the optical path). That is, the phosphors 5 to 7 are laminated in order from the longer peak wavelength of the secondary light. In this way, the occurrence of uneven color can be prevented by laminating the phosphors in layers.
In this case, by stacking nanocrystals having different particle diameters in the order of the optical path, the phosphors having the larger particle diameters are stacked in the order of decreasing, so that the red phosphor 5, the green phosphor 6, and the blue phosphor 7 can be stacked in this order. .

  When using a plurality of phosphors to form a color conversion multi-layer in which color conversion thin film layers each containing one kind of phosphor are laminated, the phosphors in each layer are considered in consideration of the ultraviolet light transmittance of each phosphor. The ultraviolet light transmittance is preferably increased from the lower layer on the substrate 1 side (light emitting diode element 2 side) toward the upper layer.

Moreover, it is preferable that the average particle diameter of the phosphor in each layer decreases from the lower layer on the substrate 1 side (light emitting diode element 2 side) toward the upper layer. As a result, it is possible to efficiently irradiate the uppermost phosphor layer with ultraviolet rays and further prevent the ultraviolet rays from leaking outside the apparatus.
For example, when using the red phosphor 5, the blue phosphor 6, and the green phosphor 7, it is preferable to stack the red phosphor 5, the green phosphor 6, and the blue phosphor 7 in this order from the substrate 1 side. The center particle diameter of the substance is preferably in the relationship of red phosphor> green phosphor> blue phosphor.

  Moreover, it is preferable that the density of the phosphor in each layer decreases from the lower layer on the substrate 1 side (light emitting diode element 2 side) toward the upper layer. As a result, it is possible to efficiently irradiate the uppermost phosphor layer with ultraviolet rays and further prevent the ultraviolet rays from leaking outside the apparatus.

  The red phosphor 5, the green phosphor 6, and the blue phosphor 7 may have the same film thickness, but the amount of primary light absorbed by each phosphor is adjusted by changing the film thickness. Also good.

  In FIG. 1, since the layers of the red phosphor 5, the green phosphor 6, and the blue phosphor 7 are laminated from the substrate 1 side, the particle sizes of the phosphors 5 to 7 are set on the lower layer side ( It becomes smaller in order from the semiconductor chip 2 side) to the upper layer side.

  The phosphors 5 to 7 absorb all light having energy larger than the band gap of the phosphors 5 and develop secondary light having a wavelength corresponding to the band gap. FIG. 2 is a schematic view showing such a light emitting process.

As shown in FIG. 2, the primary light (excitation light) incident on the wavelength conversion unit 8 composed of the phosphors 5 to 7 is incident on both the phosphor having a large band gap Eg _{1 and} the phosphor having a small band gap Eg _2. And excite them. Eventually, the secondary light emitted from each of the phosphors 5 to 7 is mixed, thereby producing a predetermined color.

In the schematic diagram of FIG. 2, when a phosphor having a large band gap Eg ₁ (for example, blue) is excited and emits secondary light, the secondary light is re-emitted to a phosphor having a small band gap Eg ₂ (for example, red). Will be absorbed. As a result, color development from a phosphor having a large band gap Eg ₁ (for example, blue) is reduced, and desired color development cannot be obtained as a whole of the light emitting diode device.

On the other hand, in the light emitting diode device 10 according to the present embodiment, as shown in FIG. 1, the red phosphor 5, the green phosphor 6, and the blue phosphor 7 are arranged from the side closer to the light emitting diode element 2 that is a light source. Are stacked in this order.
In such a structure, a part of the excitation light (primary light) emitted from the light emitting diode element 2 is first absorbed by the red phosphor 5 to emit red light (secondary light).
Next, the remaining components of the excitation light are absorbed by the green phosphor 6 and green light (secondary light) is emitted. At this time, the energy of the red light (secondary light) is smaller than the energy of the band gap of the green phosphor 6, so that it is transmitted without being absorbed by the green phosphor 6.
Further, the remaining components of the excitation light are absorbed by the blue phosphor 7 and blue light (secondary light) is emitted. At this time, the energy of red light (secondary light) or green light (secondary light) is smaller than the band gap energy of the blue phosphor 7, and thus is transmitted without being absorbed by the blue phosphor 7.
Finally, white light is emitted by mixing each secondary light emitted from these phosphors.

  As described above, in the light emitting diode device 10 according to the present embodiment, the phosphors 5 to 7 are stacked in such a manner that the band gap becomes smaller in order from the side closer to the light emitting diode element 2. The secondary light emitted from the light source is not reabsorbed by other phosphors, and a set color balance can be easily obtained, and an illuminating device having a high brightness of the set color can be obtained. Moreover, the setting of the color balance can be easily and independently controlled only by changing the film thickness and density of each phosphor 5-7.

  FIG. 3 shows a spectrum of white light emitted from the light emitting diode device, where the horizontal axis indicates the wavelength and the vertical axis indicates the relative intensity. 3, A is the emission spectrum of the light emitting diode device 10 (FIG. 1) according to the present embodiment, and B is the emission spectrum of the conventional light emitting diode device (FIG. 4).

In the light emitting diode device 10 according to the present embodiment, since the secondary light is prevented from being reabsorbed on the long wavelength side, the light emission intensity is relatively higher than that in the past, particularly in the region where the wavelength is longer than 600 nm. It is high. Further, in the light emitting diode device 10, since the wavelength conversion section 8 is doped with a YAG phosphor having two kinds of dopants Ce and Pr (double dope), a new peak appears in the vicinity of a wavelength of 620 nm. .
As a result, the light emitting diode device 10 according to the present embodiment has improved whiteness and becomes a light source that is more suitable for illumination than in the past.

  In FIG. 3, the wavelength 465 nm corresponds to blue light, the wavelength 560 nm corresponds to green light, and the wavelength 620 nm corresponds to red light.

It is sectional drawing of the light emitting diode apparatus concerning embodiment of this invention. It is a schematic diagram which shows the light emission mechanism of the fluorescent substance concerning embodiment of this invention. It is a graph which shows the light emission spectrum characteristic of the light emitting diode apparatus concerning embodiment of this invention, and the conventional light emitting diode apparatus. It is sectional drawing of the conventional light emitting diode apparatus.

Explanation of symbols

1: substrate, 2: light-emitting diode element, 3: lens holder, 4: recess, 5: red phosphor, 6: green phosphor, 7: blue phosphor, 8: wavelength conversion unit, 9: lens unit, 10: Light emitting diode device

Claims (11)

A light emitting diode device for mixing colors emitted from a plurality of phosphors,
A light emitting diode element that emits primary light;
A wavelength conversion unit including a plurality of phosphor layers that absorbs the primary light and emits secondary light; and
The wavelength conversion unit includes a first phosphor layer on which the primary light emitted from the light emitting diode is first incident, and a second phosphor layer on which the primary light transmitted through the first phosphor layer is incident. ,
The light emitting diode device, wherein the band gap energy of the phosphor of the second phosphor layer is larger than the energy of the peak wavelength of the secondary light emitted from the first phosphor layer.   The light emitting diode device according to claim 1, wherein the first phosphor layer and the second phosphor layer have substantially the same film thickness.   The amount of primary light absorbed in each of the first phosphor layer and the second phosphor layer is adjusted by changing the film thicknesses of the first phosphor layer and the second phosphor layer. The light-emitting diode device according to claim 1.   The light emitting diode device according to claim 1, wherein the particle diameters of the phosphors included in the first phosphor layer and the second phosphor layer are substantially uniform.   2. The light emitting diode device according to claim 1, wherein an average particle diameter of the phosphor contained in the first phosphor layer is larger than an average particle diameter of the phosphor contained in the second phosphor layer.   The average particle diameter of the granular phosphor contained in the first phosphor layer and the granular phosphor contained in the second phosphor layer is in the range of about 10 nm to about 100 nm. Item 6. The light-emitting diode device according to Item 4 or 5.   The light emitting diode device according to claim 1, wherein the density of the phosphor contained in the first phosphor layer is higher than the density of the phosphor contained in the second phosphor layer.   The first phosphor layer is composed of a red phosphor layer, the second phosphor layer is composed of a green phosphor layer, and further, on the opposite side of the first phosphor layer with the second phosphor layer sandwiched therebetween, The light emitting diode device according to claim 1, further comprising a blue phosphor layer that is a third phosphor layer.   Red light is emitted as secondary light from the red phosphor, green light is emitted as secondary light from the green phosphor, and blue light is emitted as secondary light from the blue phosphor. The light emitting diode device according to claim 8.   The light emitting diode device according to any one of claims 1 to 8, wherein a wavelength of primary light emitted from the light emitting diode element is in a range of about 250 nm to about 365 nm. The light-emitting diode device according to claim 1, wherein the phosphor is a nanocrystal.

Images