JP2006332202A - Light emitting device, manufacturing method thereof, and lighting apparatus using it, backlight for image display apparatus, and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make luminous intensity distribution constant and eliminate color spots in a light emitting device including a light source and a phosphor for absorbing at least a part of light from the light source, and emitting light having a different wavelength. <P>SOLUTION: When chromaticity coordinates are defined as (x<SB>0</SB>, y<SB>0</SB>) and (x<SB>60</SB>, y<SB>60</SB>) when there are given as 0° and 60° angles θ between an optical axis and a straight line connecting an observation point in an arbitrary plane including the optical axis and a light source, a square root of the sum of squares of differences (x<SB>0</SB>-x<SB>60</SB>) and (y<SB>0</SB>-y<SB>60</SB>) is set below 0.008. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device that emits light by a combination of a semiconductor light emitting device such as an LED (light emitting diode) and a plurality of types of phosphors.

  A semiconductor light emitting device in which a semiconductor light emitting device and a phosphor are combined has attracted attention as a new light source because the emission color can be freely changed by selecting the combination and type. That is, the wavelength of the primary light emitted from the semiconductor light emitting device is converted by the phosphor and extracted as secondary light, so that the degree of freedom in selecting the obtained wavelength can be greatly expanded.

  However, it has been pointed out that the semiconductor light-emitting device has unevenness of light emission. Specifically, for example, when the semiconductor light-emitting device is viewed from the light extraction direction, the emission color is different at the center of the light-emitting portion, that is, near the vertical upper side of the LED and the peripheral portion at the end. Has been pointed out. This problem can be a major obstacle when used as a light source such as illumination, which is expected as an application field of semiconductor light emitting devices. Human color sensation is particularly sensitive in white, so even a slight color difference feels reddish white, greenish white, yellowish white, etc. A semiconductor light emitting device as described above, in which the center portion where the LED chip is arranged is tinged with blue when viewed from the light emission observation surface side, and a yellow, green or red tinged portion is seen in the ring shape toward the peripheral direction. When applying to lighting, the emitted white light causes the light source chromaticity to change to a complementary color, which causes chromaticity spots to be felt, which strongly stresses human visual perception.

Furthermore, the color spots generated by directly looking at the light emission observation surface are not preferable in terms of quality as a light source, and color spots on the display surface when used in a display device, and errors in precision instruments such as optical sensors. This is also not preferable.
Several measures have already been proposed to improve the above problem. For example, in Patent Document 1, as a method paying attention to the structure of a semiconductor light-emitting device, when a plurality of types of phosphors are applied around the light-emitting element, mixing caused by differences in specific gravity and particle size of the respective phosphors It prevents spots. The structure is characterized in that a light emitting element is mounted in a form embedded in a mounting member, and a plurality of phosphors are coated on the substantially flat surface thus obtained. In this way, phosphors can be uniformly mixed or coated on a uniform layer, and light emission without color spots can be realized.

  In Patent Document 2, the following proposal has been made by paying attention to the particle size and shape of the phosphor. That is, the light emitting element absorbs at least a part of the light emitted from the light emitting element and emits light having a wavelength different from the absorbed light, and has an average particle diameter of 3 μm or more and a particle size distribution of 2 μm or less. A phosphor composed of phosphor particles having a particle size of 10% or less in volume distribution, a phosphor member made of a translucent material containing the phosphor, and the phosphor has at least a fracture surface. A first phosphor composed of fractured particles that absorb at least part of the light emitted from the light emitting element and emit light having a first wavelength different from the absorbed light, and a substantially regular crystal. A second phosphor that has a growth shape and absorbs at least part of the light emitted from the light emitting element and is composed of growing particles that emit light having a second wavelength different from the absorbed light. Especially Therefore, the color spots are said to be improved.

However, in either case, sufficient performance cannot be obtained, and it is not a sufficient solution for application of a semiconductor light-emitting device particularly in the illumination field.
JP 2000-31532 A JP 2004-161806 A

An object of the present invention is to make light distribution constant and eliminate color spots in a light emitting device including a light source and a phosphor that absorbs at least a part of light from the light source and emits light having different wavelengths. Is.
In the semiconductor light emitting device taken up in the present invention, the light emitted from the LED chip passes through a layer containing a phosphor (in many cases, a layer in which the phosphor is dispersed in a resin), and the light excites the phosphor during that time. Thus, the light emitted from the semiconductor light-emitting device is required to be uniform and uniform from any angle. However, a commercially available device can recognize a color difference depending on an angle even with the naked eye.

  More specifically, this semiconductor light emitting device is roughly divided into two systems. That is, there are a case where a part of the excitation light is used as one component of the extracted light and a system where the excitation light is shorter than the visible light and is not used as one component of the extracted light. In either case, the light emitted from the phosphor is repeatedly reflected by the phosphor or, if necessary, a filler (a bulking agent or a diffusing agent) contained in the phosphor-containing layer, and is sufficiently mixed. Necessary.

It is ideal that the phosphor absorbs the photon of the excitation light and emits the corresponding fluorescence as the photon, but the actual phosphor introduces the concept of efficiency because loss occurs in each process.
A part of the excitation light is absorbed by the phosphor, and the other part is reflected. The absorbed excitation light is converted into fluorescence according to the emission mechanism of the phosphor. At this time, the ratio of the number of photons emitted to the number of absorbed photons is called internal quantum efficiency and is generally defined. The generated fluorescence travels through the phosphor and is then emitted out of the phosphor. The emitted light is transmitted through the layer containing the phosphor, collides with other phosphors, and is reflected. If the number of collisions increases, it will be in the state of uniform diffuse reflection and color spots will not occur. That is, it is presumed that color spots are observed in the current semiconductor light emitting device because of the lack of balance between absorption, reflection and light emission.

As a result of intensive investigations focusing on this point, the present inventors have found that a phosphor that can be used in a semiconductor light emitting device without color spots includes a quantum reflection efficiency αr defined by (1-quantum absorption efficiency), The inventors have found that there is a specific relationship with the internal quantum efficiency ηi, and have reached the present invention.
Furthermore, in a light emitting device comprising a light source and a phosphor that absorbs at least a part of the light from the light source and emits light having a different wavelength, a straight line connecting an observation point in any plane including the optical axis and the light source When the angle between the optical axis and the optical axis is θ, there is a specific range between chromaticity coordinates (x ₀ , y ₀ ) when θ is 0 degrees and chromaticity coordinates (x ₆₀ , y ₆₀ ) when θ is 60 degrees. We found that there is a relationship and reached the present invention.

The present invention has been achieved based on such knowledge, and has the following gist.
(1) In a light emitting device including a light source and a phosphor that emits light having a different wavelength by absorbing at least a part of the light from the light source, the chromaticity coordinates when θ is 0 degrees are (x ₀ , y ₀ ). , Θ is chromaticity coordinates (x ₆₀ , y ₆₀ ) at 60 degrees, the square root of the sum of the squares of (x ₀ -x ₆₀ ) and (y ₀ -y ₆₀ ) is 0.008 or less. A light emitting device characterized by that. (Here, θ is an angle formed by a straight line connecting an observation point and a light source in an arbitrary plane including the optical axis and the optical axis.)
(2) The light emitting device according to (1), wherein a phosphor having a product of quantum reflection efficiency and internal quantum efficiency of 0.18 or more is used as the phosphor.
(3) The phosphor according to (1) or (2), wherein a phosphor having a quantum reflection efficiency of 0.3 or more is used as the phosphor.
(4) The light emitting device according to any one of (1) to (3), wherein a phosphor having an internal quantum efficiency of 0.3 or more is used as the phosphor.
(5) as a phosphor, the light emitting device according to a median diameter D ₅₀ is characterized by using a phosphor is 5μm or less (1) to (4).
(6) An illumination device using the light-emitting device according to any one of (1) to (5).
(7) A backlight for an image display device using the light emitting device according to any one of (1) to (5).
(8) An image display device using the light emitting device according to any one of (1) to (5).

  The light-emitting device of the present invention has no color spots, good light distribution characteristics, and can emit light uniformly. In addition, by using the light emitting device of the present invention, it is possible to obtain a high quality lighting device and an image display device having stable color reproducibility as compared with the conventional case.

The following embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (typical) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not specified by these contents.
The semiconductor light-emitting device of the present invention is a light-emitting device including a light source and a phosphor that absorbs at least part of light from the light source and emits light having different wavelengths.

[Phosphor]
The phosphor used in the present invention has a specific relationship between the quantum reflection efficiency αr defined by (1-quantum absorption efficiency) and the internal quantum efficiency ηi. That is, when the product K of αr and ηi is 0.18 or more, a semiconductor light-emitting device that is small enough to allow color spots can be obtained. K is preferably 0.19 or more, more preferably 0.2 or more. If K is smaller than 0.18, color spots are observed, which is not preferable. In addition, the quantum reflection efficiency αr and the internal quantum efficiency ηi are independently in the range satisfying K ≧ 0.18, αr ≧ 0.3, preferably αr ≧ 0.31, and ηi ≧ 0.3, preferably It is desirable that ηi ≧ 0.4. In addition, αr ≦ 0.6, preferably αr ≦ 0.5 is desirable, and ηi is usually as large as possible.

  Here, Table 1 and FIG. 3 show the results of measuring αr and ηi for three types of phosphors having different particle sizes. From this result, it is understood that the quantum reflection efficiency αr is larger as the particle is smaller. From this, one method for obtaining a phosphor with high quantum reflection efficiency is a method of reducing the particle size. For example, the particle size of the phosphor is 5 μm or less, preferably 4.5 μm or less.

The high quantum reflection efficiency of the phosphor means that the number of photons to be absorbed is small and the emission of fluorescence is also small. Therefore, in order to obtain a sufficient amount of light, a phosphor having high internal quantum efficiency, which is an index for efficiently converting absorbed photons into fluorescence, is required.
A method for obtaining the quantum reflection efficiency (αr = 1−quantum absorption efficiency αq) and internal quantum efficiency ηi of the phosphor defined in the present invention will be described below.

  First, a phosphor sample to be measured (for example, a powdered phosphor sample) is packed in a cell with a sufficiently smooth surface so that measurement accuracy is maintained, and a spectrophotometer with an integrating sphere etc. Attach to the meter. Examples of the spectrophotometer include MCPD2000 manufactured by Otsuka Electronics Co., Ltd. The reason for using an integrating sphere or the like is to allow all photons reflected from the sample and photons emitted from the sample by photoluminescence to be counted.

  A light source for exciting the phosphor is attached to the spectrophotometer. This light emission source is, for example, an Xe lamp or the like, and is adjusted using a filter or the like so that the emission peak wavelength is 400 nm. The sample to be measured is irradiated with light from the light source adjusted to have a wavelength peak of 400 nm, and the emission spectrum is measured. This measured spectrum actually includes the amount of excitation light reflected by the sample in addition to the photons emitted from the sample by photoluminescence with light from the excitation light source (hereinafter simply referred to as excitation light). Photon contributions overlap.

The absorption efficiency αq is a value obtained by dividing the number of photons N _abs of the excitation light absorbed by the sample by the total number of photons N of the excitation light.
First, the total photon number N of the latter excitation light is obtained as follows. That is, a substance having a reflectance R of approximately 100% with respect to excitation light, for example, a reflector such as Spectralon manufactured by Labsphere (having a reflectance of 98% with respect to excitation light of 400 nm) is used as the measurement object. Mount on a photometer and measure the reflection spectrum I _ref (λ). Here, the numerical value obtained from the reflection spectrum I _ref (λ) by the following (formula 1) is proportional to N.

Here, the integration interval may be substantially performed only in the interval in which I _ref (λ) has a significant value.
The number of photons N _abs of the excitation light absorbed by the former sample is proportional to the amount obtained by the following (formula 2).

Here, I (λ) is a reflection spectrum when a target sample for which the absorption efficiency αq is to be obtained is attached. The integration range of (Expression 2) is the same as the integration range defined in (Expression 1). By limiting the integration range in this way, the second term of (Equation 2) corresponds to the number of photons generated by the target sample reflecting the excitation light, that is, out of all photons generated from the target sample. This corresponds to the one excluding the photons generated by the photoluminescence by the excitation light. Since an actual spectrum measurement value is generally obtained as digital data divided by a certain finite bandwidth with respect to λ, the integrals of (Equation 1) and (Equation 2) are obtained by the sum based on the bandwidth.
From the above, αq = N _abs / N = (Expression 2) / (Expression 1). The quantum reflection efficiency αr can be obtained by 1−αq.

Next, a method for obtaining the internal quantum efficiency ηi will be described. ηi is a value obtained by dividing the number of photons NPL generated by photoluminescence by the number of photons N _abs absorbed by the sample.
Here, NPL is proportional to the amount obtained by (Equation 3) below.

(Equation 3)
∫λ · I (λ) dλ (Formula 3)

  At this time, the integration interval is limited to the wavelength range of photons generated from the sample by photoluminescence. This is because the contribution of photons reflected from the sample is removed from I (λ). Specifically, the lower limit of the integration of (Expression 3) is the upper end of the integration of (Expression 1), and the upper limit is a range suitable for including a photoluminescence-derived spectrum.

Thus, ηi = (Expression 3) / (Expression 2) is obtained.
It should be noted that the integration from the spectrum that has become digital data is the same as the case where αq is obtained.
And the luminous efficiency of the fluorescent substance defined by this invention is calculated | required by taking the product of quantum absorption efficiency (alpha) q calculated | required as mentioned above and internal quantum efficiency (eta) i.

Here, in the present invention, the particle size is a value obtained from a volume-based particle size distribution curve. The volume-based particle size distribution curve is obtained by measuring the particle size distribution by a laser diffraction / scattering method. Specifically, in an environment of an air temperature of 25 ° C. and a humidity of 70%, hexametalin having a concentration of 0.05%. Each substance was dispersed in an aqueous sodium acid solution and measured with a laser diffraction particle size distribution analyzer (SALD-2000A) in a particle size range of 0.03 μm to 700 μm. Integrated value in the volume-based particle size distribution curve is referred to particle size value when the 50% and the median diameter D _50. Further, the particle size values when the integrated values are 25% and 75% are expressed as D ₂₅ and D ₇₅ , respectively, and defined as QD = (D ₇₅ −D ₂₅ ) / (D ₇₅ + D ₂₅ ). A small QD means a narrow particle size distribution.

  In the present invention, in order to obtain a light emitting device having a particularly high color rendering property among light emitting devices having few color spots, the phosphor mixture used in the light emitting device has a red color having a peak value of fluorescence intensity in a wavelength range of 610 nm to 680 nm. It is preferable to contain at least one phosphor. By using a red phosphor having a peak value of fluorescence intensity in such a wavelength range, it is possible to obtain a light emitting device with high color reproducibility in the red region such as orange, red, and deep red. By using this light emitting device, it is possible to obtain an image display device and an illuminating device excellent in color reproducibility in the red region. When the peak value of the fluorescence intensity is shorter than 610 nm or longer than 680 nm, the color reproducibility in the red region is lowered when used in combination with a blue LED.

The red phosphor having a peak value of fluorescence intensity in the wavelength range of 610 nm to 680 nm that can be contained as the phosphor of the present invention is not particularly limited, but oxides, nitrides, and oxynitrides are thermally stable. It is preferable because of its good properties. For example, MSi ₇ N ₁₀ : Eu, MSiN ₂ : Eu, M ₂ Si ₅ N ₈ : Eu (where M represents one or more alkaline earth metals), preferably BaSi ₇ N ₁₀ : Eu, CaSiN ₂ : Eu, (Ca, Ba, Sr) ₂ Si ₅ N ₈ : Eu, etc. Another example is a phosphor represented by the following general formula (3), and the phosphor mixture contains this phosphor, so that the luminance is high and the fluorescence intensity in the red region is high, This is preferable because temperature quenching is small.

_{^{M 6 h M 7 i M 8}} j M 9 k N m O n (3)

Wherein, ^{M 6} consists of at least Eu, Cr, Mn, Fe, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, as required one or more activator elements selected from Yb M ⁷ is one or more elements selected from Mg, Ca, Zn, Sr, Cd, and Ba, M ⁸ is one or more elements selected from Al, Sc, Ga, and In, M 7 ⁹ contains one or more elements selected from Si, Ti, Ge, Zr, and Hf. h, i, j, k, m, and n are values in the following ranges, respectively.

0.00001 ≦ h ≦ 0.1
0.5 ≦ i ≦ 2
0.5 ≦ j ≦ 2
0.5 ≦ k ≦ 2
1.5 ≦ m ≦ 6
0 ≦ n / (m + n) ≦ 0.5

Formula _⁽³⁾ red phosphor represented by ^{_{[M 6 h M 7 i M}} 8 j M 9 k N m O n] is to contain ^{M 6} is at least Eu in order to obtain red light emission Is necessary, but one or more activation elements selected from Cr, Mn, Fe, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, and Yb are added as necessary. Also good.

Regarding the other elements M ^{7 to} M ⁹ , 50 mol% or more of M ⁷ is Ca and / or Sr, 50 mol% or more of M ⁸ is Al, and 50 mol% or more of M ⁹ is Si and By doing so, a phosphor with high characteristics is generated, which is preferable.
M ⁷ is one or more elements selected from Mg, Ca, Zn, Sr, Cd, and Ba, but 50 mol% or more of M ⁷ is preferably Ca and / or Sr. Ca and / or Sr is preferable because emission intensity decreases and to be less than 50 mole% of M ^7. Ca and / or Sr is but more preferably be at least 60 mol% of ^{M 7,} further more preferably from Ca and / or Sr is more than 80 mol% of ^{M 7,} more preferably to 90 mol% , M ⁷ is most preferably Ca and / or Sr.

M ⁸ is one or more elements selected from Al, Sc, Ga, and In, but it is preferable that 50 mol% or more of M ⁸ be Al. Al is preferable because emission intensity decreases and to be less than 50 mole% of M ^8. 80 mol% or more of M ⁸ is more preferably Al, more preferably 90 mol% or more, and most preferably all M ⁸ is Al.

M ⁹ is one or more elements selected from Si, Ti, Ge, Zr, and Hf, but it is preferable that 50 mol% or more of M ⁹ is Si. Si is undesirably emission intensity decreases and to be less than 50 mole% of M ^9. 80 mol% or more of M ⁹ is more preferably Si, more preferably 90 mol% or more, and most preferably all M ⁹ is Si.
In the general formula (3), h, i, j, k, m, and n representing the metal element composition ratio are preferably adjusted to be in the following numerical ranges.

0.00001 ≦ h ≦ 0.1
0.5 ≦ i ≦ 2
0.5 ≦ j ≦ 2
0.5 ≦ k ≦ 2
1.5 ≦ m ≦ 6
0 ≦ n / (m + n) ≦ 0.5

  h is in the range of 0.00001 ≦ h ≦ 0.1. If h is too small beyond this range, sufficient emission intensity cannot be obtained. On the other hand, if h is too large, concentration quenching increases. This is not preferable because the emission intensity is lowered. For the same reason, h is preferably 0.004 ≦ h ≦ 0.06, more preferably 0.006 ≦ h ≦ 0.04, and 0.008 ≦ h ≦ 0.02. Is most preferred.

i is in the range of 0.5 ≦ i ≦ 2, but if this range is exceeded and i is too small, the emission intensity is low, and if too large, the emission intensity is low. From the viewpoint of light emission intensity, i is preferably 0.75 ≦ i ≦ 1.5, and more preferably 0.9 ≦ i ≦ 1.1.
j is in the range of 0.5 ≦ j ≦ 2, but if this range is exceeded and j is too small, the emission intensity will be low, and if too large, the emission intensity will be low. From the viewpoint of light emission intensity, j is preferably 0.75 ≦ j ≦ 1.5, and more preferably 0.9 ≦ j ≦ 1.1.

k is within the range of 0.5 ≦ k ≦ 2, but if this range is exceeded and k is too small, the emission intensity will be low, and if too large, the emission intensity will be low. From the viewpoint of light emission intensity, k is preferably 0.75 ≦ k ≦ 1.5, and more preferably 0.9 ≦ k ≦ 1.1.
Although m is in the range of 1.5 ≦ m ≦ 6, if this range is exceeded and m is too small, the emission intensity is low, and if it is too large, the emission intensity is low. From the viewpoint of light emission intensity, m is preferably 2 ≦ m ≦ 4, and more preferably 2.5 ≦ m ≦ 3.5.

  The value of [n / (m + n)] is in the range of 0 and ≦ n / (m + n) ≦ 0.5. If this value exceeds the range and is too large, the light emission intensity decreases. From the viewpoint of emission intensity, the value of [n / (m + n)] is preferably 0.5 or less, more preferably 0.3 or less, and 0.1 or less is a color purity having an emission peak wavelength at an emission wavelength of 640 to 660 nm. Therefore, it is more preferable because it is a red phosphor with good quality. In addition, by setting the value of [n / (m + n)] to 0.1 to 0.3, the emission peak wavelength can be adjusted to 600 to 640 nm, and light emission with high luminance is achieved in order to approach a wavelength range where human visibility is high. Since an apparatus is obtained, it is preferable from another viewpoint.

Said red fluorescent substance can also be used 1 type or in mixture of 2 or more types.
In order to obtain a light emitting device having a high color rendering property particularly in a green region such as blue green, green, and yellow green among light emitting devices with few color spots, the phosphor mixture used in the light emitting device has a wavelength range of 500 nm to 550 nm. It is preferable to contain a green phosphor having a peak value of fluorescence intensity. By using a green phosphor having a peak value of fluorescence intensity in such a wavelength range, it is possible to obtain a light emitting device with high color reproducibility for a green region such as blue green, green, and yellow green. By using this light emitting device, it becomes possible to obtain an image display device and an illuminating device excellent in color reproducibility in the green range. When the peak value of the fluorescent intensity of the green phosphor is shorter than 500 nm or longer than 550 nm, the color reproducibility of the green region is lowered when used in combination with a blue LED, which is not preferable.

Although it does not restrict | limit especially as a green type fluorescent substance which has the peak value of fluorescence intensity in the wavelength range of 500 nm-550 nm which the fluorescent substance of this invention can contain, Good thermal stability is an oxide, nitride, and oxynitride. Therefore, it is preferable. For _{example, MSi 2 N 2 O 2:} Eu, MSi-Al-O-N: Ce, MSi-Al-O-N: Eu ( where M is one or more alkaline earth metals Preferably, SrSi ₂ N ₂ O ₂ : Eu, Ca—Si—Al—O—N: Ce, Ca—Si—Al—O—N: Eu, and the like. As another example, a phosphor containing at least Ce as the emission center ion in the host crystal represented by the following general formula (1) or (2) has high luminance and high fluorescence intensity in the green region. It is preferable because the temperature quenching is small.

M ¹ _a M ² _b M ³ _c O _d (1)
Here, M ¹ is a divalent metal element, M ² is a trivalent metal element, M ³ is a tetravalent metal element, and a, b, c, and d are numbers in the following ranges, respectively.

2.7 ≦ a ≦ 3.3
1.8 ≦ b ≦ 2.2
2.7 ≦ c ≦ 3.3
11.0 ≦ d ≦ 13.0

M ⁴ _e M ⁵ _f O _g (2)
Here, M ⁴ represents a divalent metal element, M ⁵ represents a trivalent metal element, and e, f, and g are numbers in the following ranges, respectively.

0.9 ≦ e ≦ 1.1
1.8 ≦ f ≦ 2.2
3.6 ≦ g ≦ 4.4
A suitable green phosphor used in the present invention contains at least Ce as a luminescent center ion in a host crystal represented by the following general formula (1), wherein M ¹ is a divalent metal element, M ² represents a trivalent metal element, and M ³ represents a tetravalent metal element.

M ¹ _a M ² _b M ³ _c O _d (1)
Here, M ¹ in the general formula (1) represents a divalent metal element, but at least one selected from the group consisting of Mg, Ca, Zn, Sr, Cd, and Ba from the viewpoint of luminous efficiency and the like. Preferably, Mg, Ca, or Zn is more preferable, and Ca is particularly preferable. In this case, Ca may be a single system or a composite system with Mg. Basically, M ¹ is preferably selected from the preferable elements exemplified here, but may contain other divalent metal elements as long as the performance is not impaired.

Further, M ² in the general formula (1) is a trivalent metal element, but in the same manner as described above, a group consisting of Al, Sc, Ga, Y, In, La, Gd, and Lu from the viewpoint of luminous efficiency and the like. At least one selected from the group consisting of Al, Sc, Y, or Lu is more preferable, and Sc is particularly preferable. In this case, Sc may be a single system or a composite system with Y or Lu. Basically, M ² is preferably selected from the preferable elements exemplified here, but may contain other trivalent metal elements as long as the performance is not impaired.

M ³ in the general formula (1) is a tetravalent metal element, but from the same aspect, it is preferable to contain at least Si, and usually 50 mol% or more of the tetravalent metal element represented by M ³ Si, preferably 70 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more, is Si. The tetravalent metal element other than Si of M ³ is preferably at least one selected from the group consisting of Ti, Ge, Zr, Sn, and Hf, and consists of Ti, Zr, Sn, and Hf. It is more preferably at least one selected from the group, and Sn is particularly preferable. In particular, it is preferable that M ³ is Si. Basically, M ³ is preferably composed of the preferred elements exemplified here, but may contain other tetravalent metal elements as long as the performance is not impaired.

Here, including in a range not impairing performance means that other elements are usually 10 mol% or less, preferably 5 mol% or less, more preferably, with respect to each of the metal elements of M ¹ , M ² and M ^3. Means containing 1 mol% or less.
In the general formula (1), a, b, c, and d are numbers in the following ranges, respectively.

2.7 ≦ a ≦ 3.3
1.8 ≦ b ≦ 2.2
2.7 ≦ c ≦ 3.3
11.0 ≦ d ≦ 13.0

The green phosphor of the present invention contains a luminescent center ion element in the host crystal represented by the general formula (1), and the luminescent center ionic element is any metal element of M ¹ , M ² , or M ^3. The value of a to d varies within the above range by substituting it for the position of the crystal lattice or by placing it in the gap between the crystal lattices, but the crystal structure of the phosphor is a garnet crystal structure In general, it has a body-centered cubic lattice crystal structure of a = 3, b = 2, c = 3, and d = 12.

  Further, the luminescent center ion element contained in the compound matrix of this crystal structure contains at least Ce, and Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, It is also possible to include one or more divalent or tetravalent elements selected from the group consisting of Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. In particular, it is possible to include one or more divalent to tetravalent elements selected from the group consisting of Mn, Fe, Co, Ni, Cu, Sm, Eu, Tb, Dy, and Yb. Mn, 2 to 3 valent Eu, or 3 valent Tb can be suitably contained.

Ce as the luminescent center ion is an activator. If the concentration of Ce is too small, the amount of the activator that emits light is too small and the light emission intensity is low, and if it is too large, the concentration quenching increases and the light emission intensity decreases. From the viewpoint of light emission intensity, the concentration of Ce is preferably in the range of 0.0001 or more and 0.3 or less, and 0.001 or more and 0.1 or less in terms of a molar ratio with respect to 1 mole of the metal element of M ^{1 to} M ³ Is more preferable, and the range of 0.005 or more and 0.05 or less is still more preferable.

A preferred green phosphor of the present invention contains at least Ce as a luminescent center ion in a host crystal represented by the following general formula (2), wherein M ⁴ is a divalent metal element, M ⁵ represents a trivalent metal element.

M ⁴ _e M ⁵ _f O _g (2)
Here, M ⁴ in the general formula (2) is a divalent metal element, but at least one selected from the group consisting of Mg, Ca, Zn, Sr, Cd, and Ba from the viewpoint of luminous efficiency and the like. Preferably, Mg, Ca, or Zn is more preferable, and Ca is particularly preferable. In this case, Ca may be a single system or a composite system with Mg. Basically, M ⁴ is preferably selected from the preferable elements exemplified here, but may contain other divalent metal elements as long as the performance is not impaired.

Further, M ⁵ in the general formula (2) is a trivalent metal element, but from the same aspect, at least 1 selected from the group consisting of Al, Sc, Ga, Y, In, La, Gd, and Lu. It is preferably a seed, more preferably Al, Sc, Y, or Lu, and Sc is particularly preferable. In this case, Sc may be a single system or a composite system with Y or Lu. Basically, M ⁵ is preferably selected from the preferable elements exemplified here, but may contain other trivalent metal elements as long as the performance is not impaired.

Here, including in a range that does not impair the performance means that other elements are usually 10 mol% or less, preferably 5 mol% or less, more preferably 1 mol with respect to the metal elements of M ⁴ and M ^5. Say to include below.
In the general formula (2), the element ratios represented by e, f, and g are preferably numbers in the following ranges, respectively, from the viewpoint of light emission characteristics.

0.9 ≦ e ≦ 1.1
1.8 ≦ f ≦ 2.2
3.6 ≦ g ≦ 4.4

  Further, the luminescent center ion contained in the compound matrix of this crystal structure contains at least Ce, and Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Sm are included for fine adjustment of the luminescent properties. , Eu, Tb, Dy, Ho, Er, Tm, and Yb, and may include one or more divalent to tetravalent elements selected from the group consisting of Mb, Fe, Co, and Ni. , Cu, Sm, Eu, Tb, Dy, and Yb can contain one or more divalent or tetravalent elements selected from the group consisting of divalent Mn, and bivalent Eu. Or trivalent Tb can be suitably added.

Ce of the luminescent center ion is an activator. If the concentration of Ce is too small, the amount of the activator that emits light is too small and the light emission intensity is low, and if it is too large, the concentration quenching increases and the light emission intensity decreases. From the viewpoint of light emission intensity, the concentration of Ce is preferably in the range of 0.0001 or more and 0.3 or less, and 0.001 or more and 0.1 or less in terms of a molar ratio with respect to 1 mol of M ^{4 and} M ⁵ metal elements. Is more preferable, and the range of 0.005 or more and 0.05 or less is still more preferable.
Said green fluorescent substance can also be used 1 type or in mixture of 2 or more types.

The blue phosphor having a peak value of fluorescence intensity in the wavelength range of 440 nm to 490 nm that can be contained as the phosphor of the present invention is not particularly limited, but oxides, nitrides, and oxynitrides are thermally stable. Is preferable.
M ₅ (PO ₄ ) ₃ (X): Eu ²⁺ as a blue phosphor
[Wherein M represents at least one of the metals Ba, Ca or in combination with Sr, and X represents at least one of halogen F or Cl],
ZnS: Ag,
M ^* ₃ MgSi ₂ O ₈ : Eu ²⁺
[Wherein M ^* represents at least one of the metals Ba, Ca, Sr or a combination thereof],
And M ^** MgAl ₁₀ O ₁₇ : Eu ²⁺
[Wherein M ^** represents at least one of the metals Eu and Sr, or a combination with Ba].

Said blue fluorescent substance can also be used 1 type or in mixture of 2 or more types.
The phosphor is preferably dispersed in the resin after performing a known surface treatment such as calcium phosphate treatment as necessary.

[Light emitting device]
The light-emitting device of the present invention includes a light source and a phosphor that emits light having a different wavelength by absorbing at least a part of the light from the light source. _{When the} chromaticity coordinates (x ₆₀ , y ₆₀ ) at ₀ , y ₀ ) and θ are 60 degrees, the square root of the sum of the squares of (x ₀ −x ₆₀ ) and (y ₀ −y ₆₀ ) is 0. .008 or less.

Preferably, the square root is 0.0075 or less. If the square root exceeds 0.008, light distribution characteristics are insufficient and color spots may occur, which is not preferable. Here, θ is an angle formed by a straight line connecting an observation point and a light source in an arbitrary plane including the optical axis and the optical axis. X ₀ , y _0, x ₆₀ , and y ₆₀ are based on the CIE 1931 color system.
In the present invention, the reason why the chromaticity coordinate values when θ is 0 degree and 60 degrees is adopted is that the illuminance at an angle exceeding 60 degrees is generally reduced to a practical level. The light distribution characteristics can be measured using, for example, an LED light distribution measuring device: OL770 MULTI-CHANNEL SPECTRORADIOMETER manufactured by OPTRONIC LABORATORIES.

In the present invention, the light source for irradiating the phosphor with light preferably generates light having a wavelength of 360 nm to 490 nm. Specific examples of such a light source include a light emitting diode (LED) or a laser diode (LD). A laser diode is more preferable because it consumes less power. Of these, GaN LEDs and LDs using GaN compound semiconductors are preferred. This is because GaN-based LEDs and LDs have significantly higher light emission output and external quantum efficiency than SiC-based LEDs that emit light in this region, and are extremely bright with very low power when combined with the phosphor. This is because light emission can be obtained. For example, for a current load of 20 mA, the GaN system usually has a light emission intensity 100 times or more that of the SiC system. GaN-based LEDs and LDs preferably have an Al _X Ga _Y N light emitting layer, a GaN light emitting layer, or an In _X Ga _Y N light emitting layer. Among the GaN-based LEDs, those having an In _X Ga _Y N light-emitting layer are particularly preferable because the emission intensity is very strong, and in the GaN-based LD, the multiple quantum of the In _X Ga _Y N layer and the GaN layer A well structure is particularly preferable because the emission intensity is very strong. In the above, the value of X + Y is usually a value in the range of 0.8 to 1.2. In the GaN-based LED, those in which the light emitting layer is doped with Zn or Si or those without a dopant are preferable for adjusting the light emission characteristics. A GaN-based LED has these light-emitting layer, p-layer, n-layer, electrode, and substrate as basic components, and the light-emitting layer is composed of n-type and p-type Al _X Ga _Y N layers, GaN layers, or In _X Those having a heterostructure sandwiched between Ga _Y N layers and the like have high luminous efficiency, and those having a heterostructure in a quantum well structure have higher luminous efficiency and are more preferable.

  In the present invention, it is particularly preferable to use a surface-emitting type illuminant, particularly a surface-emitting GaN-based laser diode, as the light source, since this increases the luminous efficiency of the entire light-emitting device. A surface-emitting type illuminant is an illuminant that emits strong light in the surface direction of a film. In a surface-emitting GaN-based laser diode, the crystal growth of a light-emitting layer or the like is controlled, and a reflective layer or the like is successfully performed. By devising, the light emission in the surface direction can be made stronger than the edge direction of the light emitting layer. Compared with the type that emits light from the edge of the light-emitting layer by using a surface-emitting type, the emission cross-sectional area per unit light emission can be increased. Can be made very large and the irradiation efficiency can be improved, so that stronger luminescence can be obtained from the phosphor.

When a surface emitting type light source is used as the light source, the phosphor is preferably formed in a film form by mixing with a resin or the like. As a result, since the cross-sectional area of the light from the surface-emitting type phosphor is sufficiently large, the irradiation cross-sectional area of the phosphor from the light source increases per unit amount of phosphor, so that the intensity of light emitted from the phosphor is increased. can do.
Further, when a surface emitting type light source is used as a light source and a phosphor is mixed with a resin or the like to form a film (phosphor film), the phosphor film is directly formed on the light emitting surface of the light source. It is preferable to have a shape in which is contacted. Contact here refers to creating a state in which the light source and the phosphor film are in close contact with each other without air or gas. As a result, it is possible to avoid a light amount loss in which light from the light source is reflected by the film surface of the phosphor film and oozes out, so that the light emission efficiency of the entire apparatus can be improved.

  When the phosphor powder is dispersed in the resin, part of the light is reflected and the direction of the light can be changed to some extent, so that the light is mixed and the light distribution tends to be uniform. Therefore, it is preferable to use a phosphor film in which phosphor powder is dispersed in a resin. Further, when the phosphor powder is dispersed in the resin, since the total irradiation area of the phosphor film from the light source is increased, there is an advantage that the emission intensity from the light source can be increased. Examples of resins that can be used in this case include silicon resins, epoxy resins, polyvinyl resins, polyethylene resins, polypropylene resins, polyester resins, and the like. May be silicon resin or epoxy resin. When the phosphor powder is dispersed in the resin, the weight ratio of the phosphor powder to the entire resin is usually 0.1 to 20%, preferably 0.3 to 15%, more preferably 0.5 to 10%. It is. If the phosphor is too much, the luminous efficiency may be reduced due to aggregation of the powder, and if it is too little, the luminous efficiency may be lowered due to light absorption or scattering by the resin. Further, a bulking agent or a diffusing agent may be added to prevent color spots.

As specific extenders or diffusing agents, barium titanate, titanium oxide, aluminum oxide, silicon oxide and the like are preferably used. As a result, a light emitting device having good directivity can be obtained.
An extender or diffusing agent having a particle size of 1 nm to 1 μm has a low interference effect on the light wavelength from the semiconductor light emitting device, but can increase the resin viscosity without reducing the luminous intensity. This makes it possible to disperse the phosphor in the resin almost uniformly in the syringe and maintain the state when arranging the phosphor-containing resin by potting or the like, and the particle size is relatively difficult to handle. Even when a large phosphor is used, it is possible to produce with high yield. Thus, since the action of the extender or the diffusing agent varies depending on the range of the particle diameter, it can be selected or combined according to the method of use.

FIG. 1 is a diagram schematically showing a main part of an embodiment of a light emitting device of the present invention.
The light emitting device 1 of the present embodiment includes a frame 2, a blue LED (blue light emitting unit) 4 that is a light source, and a fluorescent light emitting unit 5 that absorbs part of light emitted from the blue LED 4 and emits light having different wavelengths. Become.
The frame 2 is a resin base for holding the blue LED 4 and the fluorescent light emitting unit 5. On the upper surface of the frame 2, a trapezoidal concave section (recess) 3 having an opening on the upper side in the figure is formed. Thereby, since the frame 2 has a cup shape, the light emitted from the light emitting device can have directivity, and the emitted light can be used effectively.

In addition, an electrode (not shown) to which electric power is supplied from the outside of the light emitting device is provided at the bottom of the concave portion 3, and electric power can be supplied to the blue LED 4 from this electrode.
Furthermore, the inner surface of the recess 3 of the frame 2 is made of a material having a high light reflectance in the entire visible light range. As a result, the light hitting the inner surface of the recess 3 of the frame 2 can be emitted from the light emitting device 1 in a predetermined direction. The electrodes are plated with a metal having a high reflectivity for visible light in general.

  A blue LED 4 is installed as a light source at the bottom of the recess 3 of the frame 2. The blue LED 4 is an LED that emits blue light when supplied with electric power. Part of the blue light emitted from the blue LED 4 is absorbed as excitation light by the light emitting substance (here, fluorescent substance) in the fluorescent light emitting unit 5, and another part is directed in a predetermined direction from the light emitting device. To be released.

  In addition, as described above, the blue LED 4 is installed at the bottom of the recess 3 of the frame 2. Here, a silver paste (a mixture of silver particles in an adhesive) is placed between the frame 2 and the blue LED 4. ) 6, whereby the blue LED 4 is installed on the frame 2. Further, the silver paste 6 also plays a role of efficiently radiating heat generated in the blue LED 4 to the frame 2.

  Further, a gold conductive wire 7 for supplying power to the blue LED 4 is attached to the frame 2. That is, the blue LED 4 and the electrode (not shown) provided on the bottom of the recess 3 of the frame 2 are connected by wire bonding using the wire 7, and the blue LED 4 is energized by energizing the wire 7. The blue LED 4 emits blue light. One or a plurality of wires 7 are attached according to the structure of the blue LED 4.

  Further, the concave portion 3 of the frame 2 is provided with a fluorescent light emitting portion 5 that absorbs part of the light emitted from the blue LED 4 and emits light having a different wavelength. The fluorescent light emitting unit 5 is formed of a phosphor and a transparent resin. The phosphor is a substance that is excited by blue light emitted from the blue LED 4 and emits light having a wavelength longer than that of the blue light. The fluorescent substance which comprises the fluorescent light emission part 5 may be one type, and may be a mixture which consists of two or more, and the sum total of the light which the blue LED 4 emits, and the light which the fluorescent substance light emission part 5 emits becomes a desired color. Choose to be. The color is not limited to white, but may be yellow, orange, pink, purple, blue-green, or the like. Further, it may be an intermediate color between these colors and white. Further, the transparent resin is a binder of the fluorescent light emitting unit 5, and here, a synthetic resin capable of transmitting visible light over the entire wavelength region is preferable.

  FIG. 2 is a schematic view showing a surface-emitting illuminating device 8 which is an embodiment of an illuminating device using the light-emitting device of the present invention, and has a rectangular holding case whose inner surface is light-impermeable such as a white smooth surface. A large number of light-emitting devices 1 are arranged on the bottom surface of 10, a power source and a circuit (not shown) for driving the light-emitting device 1 are provided on the outside thereof, and a portion corresponding to the lid portion of the holding case 10 is provided. A diffusing plate 9 such as a milky white acrylic plate is fixed for uniform light emission.

  An image display device using the light emitting device of the present invention includes at least a light source (excitation source) and a phosphor. Examples of the image display device include a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), and the like. It can also be used for a backlight for an image display device.

Example 1
A light emitting device having the same configuration as that shown in FIG. 1 was manufactured and its light distribution characteristics were evaluated. Note that, among the components of the light emitting device manufactured in Example 1, those corresponding to those illustrated in FIG. 1 are appropriately indicated in parentheses.
First, a frame (2) having a cup-shaped recess (3) was prepared. A light emitting diode (4) was die-bonded to the bottom of the recess (3) as a light source emitting light at a wavelength of 450 nm to 470 nm using a silver paste (6) as an adhesive. At this time, the silver paste (6) used for die bonding was applied thinly and uniformly in consideration of heat dissipation of the heat generated in the light emitting diode (4). This was heated at 150 ° C. for 2 hours to cure the silver paste (6), and then the light emitting diode and the frame electrode were wire bonded. As the wire (7), a gold wire with a diameter of 25 μm was used.

As the blue LED (4), 460 MB manufactured by Cree was used. As the luminescent material of the fluorescent light emitting part (5), Ca _0.992 Eu _0.008 AlSiN ₃ (D ₅₀ = 2.6 μm) emitting light having a wavelength of about 520 nm to 760 nm was used. The weight ratio of epoxy resin, curing agent, aerosil, and phosphor contained in the fluorescent light emitting part (5) is 100: 70: 0.5: 3.4, and these are fully sold and mixed to create a phosphor slurry. did. The amount of phosphor added is 2.0% by weight.

The phosphor slurry was poured into the recess (3) of the frame (2), and was heated and cured.
Next, the entire frame was molded with epoxy resin. A cup-shaped mold was used for forming the mold part.
This light-emitting device was made to emit light by supplying power to the blue LED (4). At this time, the light distribution characteristic of the light emitted from the light emitting device was measured using an LED light distribution measuring device: OL770 MULTI-CHANNEL SPECTRORADIOMETER manufactured by OPTRONIC LABORATORIES. The light distribution measurement results are shown in Table 2.

Comparative Example 1
A light emitting device was produced in the same manner as in Example 1 except that 2.5 wt% of phosphor Ca _0.992 Eu _0.008 AlSiN ₃ having D ₅₀ = 5.1 μm was used as the phosphor. The light distribution measurement results are shown in Table 2.

Comparative Example 2
A light emitting device was produced in the same manner as in Example 1 except that 3.2 wt% of the phosphor Ca _0.992 Eu _0.008 AlSiN ₃ having D ₅₀ = 6.8 μm was used as the phosphor. The light distribution measurement results are shown in Table 2.

Comparative Example 3
Using 460 MB of Cree as the blue LED (4), 10% by weight of YAG: Ce, Tb phosphor (D ₅₀ = 6.0 μm) emitting light having a wavelength of about 480 nm to 720 nm was used as the phosphor. A light emitting device was produced in the same manner as in Example 1 except for the above. The light distribution measurement results are shown in Table 2.

Reference Example For a commercially available white LED (manufactured by Nichia Chemical Co., Ltd., surface mount LED, NSCW310 BF3), the light distribution was measured in the same manner as in Example 1. The light distribution measurement results are shown in Table 2.

  From the above results, it is clear that the LED according to the present invention has a constant light distribution and few color spots.

It is sectional drawing which shows typically the principal part of the light-emitting device as embodiment of this invention. It is typical sectional drawing which shows one Example of the surface emitting illumination device incorporating the light-emitting device shown in FIG. It is a figure which shows the relationship between the particle diameter of fluorescent substance, and (internal quantum efficiency (eta) i x quantum reflection efficiency (alpha) r).

Explanation of symbols

1: Light emitting device 2: Frame 3: Trapezoidal concave section 4: Blue LED
5: Fluorescent light emitting part 6: Silver paste 7: Conductive wire 8: Surface emitting illumination device 9: Diffuser 10: Holding case

Claims (8)

In a light emitting device including a light source and a phosphor that absorbs at least a part of light from the light source and emits light having a different wavelength, chromaticity coordinates when θ is 0 degrees are (x ₀ , y ₀ ), and θ is When the chromaticity coordinates (x ₆₀ , y ₆₀ ) at 60 degrees are used, the square root of the sum of the squares of (x ₀ -x ₆₀ ) and (y ₀ -y ₆₀ ) is 0.008 or less. A light emitting device.
(Here, θ is an angle formed by a straight line connecting an observation point and a light source in an arbitrary plane including the optical axis and the optical axis.) The light emitting device according to claim 1, wherein a phosphor having a product of quantum reflection efficiency and internal quantum efficiency of 0.18 or more is used as the phosphor. The light emitting device according to claim 1 or 2, wherein a phosphor having a quantum reflection efficiency of 0.3 or more is used as the phosphor. The light emitting device according to any one of claims 1 to 3, wherein a phosphor having an internal quantum efficiency of 0.3 or more is used as the phosphor. As the phosphor, the light emitting device according to any one of claims 1 to 4 median diameter D ₅₀ is characterized by using a phosphor is 5μm or less. An illumination device using the light-emitting device according to claim 1. 6. A backlight for an image display device, wherein the light-emitting device according to claim 1 is used. An image display device using the light-emitting device according to claim 1.

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