JP5286639B2 - Phosphor mixture, light emitting device, image display device, and illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device which has a high luminance and color rendering properties, and a little color shift of the emitted light, an image display and a lighting unit having the light-emitting device as a light source, and a phosphor mixture for obtaining the light-emitting device. <P>SOLUTION: The phosphor mixture contains at least two types of phosphors and satisfies formula (A): 0.85&le;BR(125)/BR(25)&le;1.15 and formula (B): -0.03&le;x<SB>1</SB>(25)-x<SB>1</SB>(125)&le;0.03 [wherein BR (25) is a brightness of the fluorescence obtained by being excited by a blue light having a peak wavelength of 455 nm at 25&deg;C; x<SB>1</SB>(25) is a chromaticity coordinate value x; BR (125) is a brightness of the fluorescence obtained by being excited by a blue light having a peak wavelength of 455 nm at 125&deg;C; and x<SB>1</SB>(125) is a chromaticity coordinate value x]. The light-emitting device uses the phosphor mixture. The image display and the lighting unit have this light-emitting device. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a phosphor mixture that absorbs visible light and emits longer wavelength visible light as a wavelength conversion material, and a combination of the phosphor mixture and a semiconductor light emitting device such as a light emitting diode (LED) or a laser diode (LD). In addition, the present invention relates to a light-emitting device that has high luminance and color rendering properties and has a stable temperature characteristic, so that the change in emission color is small, and an image display device and a lighting device using the light-emitting device.

  Conventionally, a white light emitting device composed of a combination of a semiconductor light emitting element such as a gallium nitride (GaN) light emitting diode (LED) and a phosphor as a wavelength conversion material has low power consumption and a long lifetime. It is known that. These light-emitting devices are attracting attention as light-emitting sources of image display devices and illumination devices by taking advantage of the above characteristics. Among them, a white light emitting device in which an In-doped GaN blue LED and a Ce-activated yttrium aluminum garnet yellow phosphor are combined can be cited as a typical light emitting device.

  However, conventionally, it has been pointed out that this light emitting device has a small amount of light in the red region (600 nm or more) and a small amount of light in the blue-green region (480 nm to 510 nm) and low color rendering. Further, in this light emitting device, when the current flowing through the light emitting device is increased in order to obtain a high amount of light, the fluorescence intensity of the phosphor decreases as the temperature of the phosphor increases due to the heat emitted from the light emitting device. A so-called temperature quenching phenomenon becomes remarkable. For this reason, when this light-emitting device is used, the mixed color balance of the blue light from the blue LED and the yellow light from the phosphor is shifted, and the emitted light color of the white light-emitting device is significantly shifted. Furthermore, since the average color rendering index Ra of the light-emitting device is low, and the change in the light-emitting color when using the light-emitting device is large, it is difficult to obtain a stable light-emitting color, and further improvements have been demanded.

In order to improve the problem of low color rendering of the light emitting device, Patent Document _{1, (Y 1-a-} b Gd a Ce b) 3 (Al 1-c Ga c) the _{5 O 12} based green phosphor emission color In addition to using (Ca _1-ab Sr _a Eu _b ) S: Eu ²⁺ red phosphors to increase the red component, and exciting these phosphors with a blue LED It is disclosed that a white light emitting device that emits synthetic light can be obtained.
Non-Patent Document 1 discloses a white light emitting device using SrGa ₂ S ₄ : Eu ²⁺ as a green phosphor and ZnCdS: Ag, Cl as a red phosphor, and Patent Document 2 discloses a green phosphor. (Sr, Ca, Ba) (Al, Ga) ₂ S ₄ : Eu ²⁺ and (Ca, Sr) S: Eu ²⁺ as a red phosphor are disclosed.
J. et al. Electrochem. Soc. Vol. 150 (2003) pp. H57-H60 JP 2003-243715 A Special Table 2002-53156

However, according to the prior art described in Patent Document 1, although the color rendering of the white light emitting device is improved by the combination of these phosphors, any of the phosphors to be combined is a substance that exhibits a temperature quenching phenomenon, When the value of the current flowing through the white light emitting device is increased, there is a problem that the luminous flux emitted from the light emitting device is lowered and the emission color is largely changed.
Moreover, since the red phosphor used is a sulfide-type red phosphor with low moisture resistance, the white phosphor is prone to deterioration and, in addition, its synthesis is difficult, resulting in high production costs. Has a problem of low durability and high price. Furthermore, since the emission color of the green phosphor used is biased to yellow, there is a problem in that the light emission in the blue-green region is insufficient and the color rendering is inferior.

Furthermore, in the prior art described in Non-Patent Document 1 and Patent Document 2, sufficient light flux and color rendering cannot be obtained even by a combination of these phosphors, and sulfides are likely to deteriorate during use of a white light emitting device. In addition, since any of these phosphors is a substance in which temperature quenching is remarkably observed, there has been a problem that the emission color changes greatly when the current to the white light emitting device increases.
An object of the present invention is to solve the above-described problems of the prior art, and to provide a light emitting device that has high luminance and color rendering properties and has little color misregistration. That is, the present invention provides a light emitting device that has high luminance, is close to natural light, and has little deviation in emission color due to increase or decrease in the amount of emitted light, and an image display device and an illumination device that use the light emitting device. .

  As a result of intensive studies to solve the above problems, the present inventor found that the ratio of luminance due to excitation with blue light at two different specific temperatures is within a predetermined range, and the difference in chromaticity coordinates at the specific temperature. It was found that by using a phosphor mixture having a brightness within a predetermined range, a light-emitting device having high luminance, high color rendering properties, and little color shift due to a change in the amount of light can be obtained.

That is, the gist of the present invention is as follows.
[1] A phosphor mixture containing at least two kinds of phosphors, wherein the phosphor brightness is obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm at 25 ° C. BR (25), The chromaticity coordinate value x is x ₁ (25), the luminance of fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm at 125 ° C. is BR (125), and the chromaticity coordinate value x is x ₁ (125). A phosphor mixture characterized by satisfying the following formulas (A) and (B):
(Equation 1)
0.85 ≦ BR (125) / BR (25) ≦ 1.15 (A)
−0.03 ≦ x ₁ (25) −x ₁ (125) ≦ 0.03 (B)

[2] The phosphor chromaticity coordinate value y obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm at 25 ° C. is y ₁ (25), and excited with blue light having a peak wavelength of 455 nm at 125 ° C. The phosphor mixture as described in [1] above, wherein the following formula (C) is satisfied when the chromaticity coordinate value y of fluorescence obtained is y ₁ (125).
(Equation 2)
−0.03 ≦ y ₁ (25) −y ₁ (125) ≦ 0.03 (C)

[3] The phosphor according to [1] or [2], wherein the phosphor mixture contains at least one green-based phosphor having a fluorescence intensity peak value in a wavelength range of 500 nm to 550 nm. blend.
[4] The phosphor according to [1] or [2], wherein the phosphor mixture contains at least one kind of red phosphor having a peak value of fluorescence intensity in a wavelength range of 610 nm to 680 nm. blend.

[5] A light emitting device comprising a light source that emits light when a drive current is passed, and at least one wavelength conversion material that emits light having different wavelengths by absorbing at least part of the light from the light source, The light-emitting device containing the fluorescent substance mixture in any one of said [1]-[4] as a wavelength conversion material.

[6] 17.5A / cm ² of the drive current density _x 2 (17.5) chromaticity coordinate x of the light emission obtained by, 70A / cm ² of the drive current of the light emitting obtained by density chromaticity coordinates x Wherein x ₂ (70) is satisfied, the following formula (D) is satisfied.
(Equation 3)
−0.006 ≦ x ₂ (17.5) −x ₂ (70) ≦ 0.006 (D)

[7] 17.5A / cm ² of the drive current density _y 2 (17.5) chromaticity coordinate y of the light emission obtained by, 70A / cm ² of the drive current of the light emitting obtained by density chromaticity coordinate value y The light emitting device according to [5] or [6] above, wherein y ₂ (70) satisfies the following formula (E):
(Equation 4)
−0.006 ≦ y ₂ (17.5) −y ₂ (70) ≦ 0.006 (E)

[8] An image display device comprising the light-emitting device according to any one of [5] to [7].
[9] An illumination device comprising the light-emitting device according to any one of [5] to [7].

  By using the phosphor mixture having the characteristics satisfying the predetermined relational expressions relating to the luminance and chromaticity coordinate values of the present invention, it is possible to obtain a light emitting device that has high luminance and color rendering properties and little color shift due to increase or decrease in the amount of light. In addition, it is possible to provide an image display device and a lighting device that include the light-emitting device, have excellent color reproducibility in a light emission color gamut, and have sufficient brightness.

The description of the constituent requirements described below is a typical example of the embodiment of the present invention, and is not limited to these contents.
The phosphor mixture of the present invention is a phosphor mixture containing at least two or more kinds of phosphors, and the fluorescence intensity obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm at 25 ° C. BR (25), the chromaticity coordinate value x is x ₁ (25), the brightness of the fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm at 125 ° C. is BR (125), and the chromaticity coordinate value x is x _1. When it is (125), it is a phosphor mixture satisfying the following formulas (A) and (B), preferably (C).

0.85 ≦ BR (125) / BR (25) ≦ 1.15 (A)
−0.03 ≦ x ₁ (25) −x ₁ (125) ≦ 0.03 (B)
−0.03 ≦ y ₁ (25) −y ₁ (125) ≦ 0.03 (C)

  The phosphor mixture of the present invention has a fluorescence brightness [BR (25)] obtained by excitation with blue light having a peak wavelength of 455 nm at 25 ° C. [125]. The ratio [BR (125) / BR (25)] of BR (125)] needs to satisfy the above formula (A). When this ratio is less than 0.85 or greater than 1.15, in a white light-emitting device using such a phosphor mixture, the current value passed through the blue LED to change the amount of light obtained therefrom is set. When the number is increased or decreased, there is a possibility that the obtained emission color is greatly changed and a stable emission color cannot be obtained.

  This is because when the amount of current flowing through the blue LED is increased or decreased to increase or decrease the amount of blue light, the temperature of the phosphor placed near the blue LED increases or decreases due to the increase or decrease in the amount of heat generated from the blue LED. This is because the fluorescence intensity from the body greatly deviates from the fluorescence intensity expected from the light quantity of the blue LED. That is, when the amount of current supplied to the blue LED is increased or decreased in an attempt to increase or decrease the amount of light of the white light emitting device, the color mixing balance between the emission intensity from the blue LED and the fluorescence intensity from the phosphor is lost, and the resulting white light emitting device The luminescent color changes greatly.

  Therefore, the luminance ratio [BR (125) / BR (25)] needs to be 0.85 or more and 1.15 or less, preferably 0.9 or more and 1.1 or less. More preferably, it is 0.9 or more and 1.05 or less. In order to obtain such a luminance ratio, it is preferable to select a phosphor constituting the phosphor mixture that has a small degree of so-called temperature quenching phenomenon in which the fluorescence intensity decreases as the temperature of the phosphor increases. .

In addition, the phosphor mixture of the present invention has x ₁ (25) as the chromaticity coordinate value x of fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm at 25 ° C., and blue light having a peak wavelength of 455 nm at 125 ° C. When the chromaticity coordinate value x of the fluorescence obtained by excitation is x ₁ (125), the difference [x ₁ (25) −x ₁ (125)] of the chromaticity coordinate value x is expressed by equation (B). -0.03 ≦ x ₁ (25) −x ₁ (125) ≦ 0.03 is satisfied. Further, the chromaticity coordinate value y of fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm at 25 ° C. is y ₁ (25), and the color of fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm at 125 ° C. When the degree coordinate value y is y ₁ (125), the difference [y ₁ (25) −y ₁ (125)] of the chromaticity coordinate value y is represented by the expression (C) −0.03 ≦ y ₁ (25) −y ₁ (125) ≦ 0.03 is preferably satisfied. When the difference between the chromaticity coordinate value x or the chromaticity coordinate value y is less than −0.03 or larger than 0.03, it becomes remarkable as the light quantity of the white light emitting device using this phosphor mixture increases or decreases. Cause color shift.

The difference [x ₁ (25) −x ₁ (125)] of the chromaticity coordinate value x and the difference [y ₁ (25) −y ₁ (125)] of the chromaticity coordinate value y are included in the phosphor mixture. This is caused by the fact that the degree of temperature quenching of each of the two or more types of phosphors greatly differs. That is, in a mixture containing two or more kinds of phosphors having different emission colors, when the degree of temperature quenching of the phosphors is different, for example, one phosphor has a small decrease in fluorescence intensity with an increase in temperature, and the other fluorescence. Assuming that the body is large, when these different light emission intensities are added together, the light emission color changes with the temperature rise and becomes different.
Therefore, the difference [x ₁ (25) −x ₁ (125)] of the chromaticity coordinate value x and the difference [y ₁ (25) −y ₁ (125) of the chromaticity coordinate value y accompanying the temperature change of the phosphor mixture. ] Is preferably as small as possible, that is, closer to zero, and is usually −0.03 or more and 0.03 or less, preferably −0.02 or more and 0.02 or less, more preferably −0.015 or more. 0.015 or less.

  In order to obtain a phosphor mixture having a small difference between the chromaticity coordinate value x and the chromaticity coordinate value y that accompanies such a temperature change, a plurality of phosphors having different fluorescent colors constituting the mixture are fluorescent by temperature quenching. It is preferable that the rate of change in intensity is substantially the same. When phosphors with almost the same rate of change in fluorescence intensity due to temperature quenching are combined, the white and other mixed colors obtained by adding the fluorescence intensities of the phosphors are almost the same regardless of temperature changes. It is possible to reduce the deviation of the emission color due to the temperature change accompanying the light quantity change.

  In the present invention, when measuring the luminance, chromaticity coordinate value x and chromaticity coordinate value y obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm, a cooling mechanism using a Peltier element and a heating mechanism using a heater are used. A fluorescence spectrophotometer equipped with a highly accurate double monochromator with sensitivity correction and wavelength correction is used. The brightness and chromaticity coordinate values are controlled by a cooling and heating mechanism, and after a sufficient time is maintained until it can be confirmed with a radiation thermometer that the phosphor surface temperature is constant at 25 ° C. or 125 ° C. Measure. In addition, in order to minimize the influence of the blue light that is the excitation light, the half width of the excitation light is narrowed to 20 nm or less, and the fluorescence spectrum of less than 470 nm is not used and only the fluorescence spectrum of 470 nm or more is used. The luminance Y, the chromaticity coordinate value x, and the chromaticity coordinate value y are calculated using the tristimulus values defined in JIS Z 8724.

  In order to obtain a light emitting device with particularly high color rendering properties among light emitting devices with little color shift, the phosphor mixture used for the light emitting device is at least a green phosphor having a peak value of fluorescence intensity in the wavelength range of 500 nm to 550 nm. It is preferable to contain one kind. 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 a display backlight, an image display device (display), and an illumination device that are 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.

As the green phosphor having a peak value of fluorescence intensity in the wavelength range of 500 nm to 550 nm that the phosphor mixture of the present invention may contain, the above formulas (A) and (B), preferably the above, Although it will not be restrict | limited especially if the formula (C) is satisfy | filled, since an oxide, nitride, and oxynitride are good in thermal stability, 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

Hereinafter, the general formula (1) will be described in more detail.
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 preferably contains at least Si from the viewpoint of luminous efficiency and the like, and usually 50 mol% of the tetravalent metal element represented by M ³ The above is 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 at least Ce as an emission center ion element in the host crystal represented by the general formula (1), and the emission center ion element is any one of M ¹ , M ² , and M ³ . The value of a to d varies within the above range by substituting for the position of the crystal lattice of the metal element or by arranging it in the gap between the crystal lattices, but the crystal structure of the phosphor is a garnet crystal The structure is generally a crystal structure of a body-centered cubic lattice with 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 to 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, Pr, Sm, Eu, Tb, Dy, and Yb. Divalent Mn, divalent to trivalent Eu, trivalent Tb, or trivalent Pr can be suitably contained.

The amount of Ce added as the luminescent center ion (activator) needs to be adjusted appropriately. If the amount of Ce added is too small, the amount of emitted light is too small and the light emission intensity is low, and if it is too large, the concentration quenching becomes large and the light emission intensity decreases. From the viewpoint of emission intensity, the concentration of Ce is preferably in the range of 0.0001 or more and 0.3 or less in terms of molar ratio to 1 mol of the base crystal represented by the general formula (1), 0.001 or more, The range of 0.1 or less is more preferable, and the range of 0.005 or more and 0.05 or less is more preferable.
Note that the phosphor containing at least Ce as the emission center ion in the host crystal represented by the general formula (1) is normally excited by light of 420 nm to 480 nm. The emission spectrum has a peak at 500 nm to 510 nm and has a wavelength component of 450 nm to 650 nm.

Next, the general formula (2) will be described in more detail.
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), where 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. It is preferable that it is Mg, Sr, Ca, or Zn, and Sr or 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 is selected from the group consisting of Al, Sc, Ga, Y, In, La, Gd, and Lu from the viewpoint of luminous efficiency and the like. At least one is preferable, 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 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. It is meant to be included in% or less.

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
The green phosphor suitably used in the present invention contains at least Ce as the luminescent center ionic element in the host crystal represented by the general formula (2), and the luminescent center ionic element is any one of M ⁴ and M ⁵ . The value of e to g varies within the above range by substituting it in the position of the crystal lattice of the metal element, or by arranging it in the gap between the crystal lattices, but e = 1, f = 2, It is preferable that g = 4.

  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 to 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, Pr, Sm, Eu, Tb, Dy, and Yb. Divalent Mn, divalent to trivalent Eu, trivalent Tb, or trivalent Pr can be suitably contained.

  The amount of Ce added as the luminescent center ion (activator) needs to be adjusted appropriately. If the amount of Ce added is too small, the amount of emitted light is too small and the light emission intensity is low, and if it is too large, the concentration quenching becomes large and the light emission intensity decreases. From the viewpoint of emission intensity, the concentration of Ce is preferably in the range of 0.0001 or more and 0.3 or less in terms of molar ratio with respect to 1 mol of the base crystal represented by the general formula (2), 0.001 or more, The range of 0.1 or less is more preferable, and the range of 0.005 or more and 0.05 or less is more preferable.

Among the phosphors containing at least Ce as the luminescent center ion in the host crystal represented by the general formula (2), Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce, Mg ₃ added Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce is preferred.
Among these, those to which Mg is added are preferable. Particularly, the Mg concentration is 0.001 or more, preferably 0.01 or more, and 0.5 or less, preferably 0.3 or less with respect to 1 mol of the base crystal. Some are preferred. Such phosphors include Ca _2.97 Ce _0.03 Sc _1.97 Mg _0.03 Si ₃ O ₁₂ , Ca _2.97 Ce _0.03 Sc _1.94 Mg _0.06 Si ₃ O ₁₂ , Ca _2.94 Ce _0.03 Sc _1.94 Mg _0.06 Si ₃ O ₁₂ , Ca _2.94 Ce _0.06 Sc _1.97 Mg _0.03 Si ₃ O ₁₂ , Ca _2.94 Ce _{0.06 Sc 1.94 Mg 0.06 Si 3 O 12} , Ca 2.94 Ce 0.06 Sc 1.9 Mg 0.1 Si 3 O 12, Ca 2.9 Ce 0.1 Sc 1.97 Mg 0.03 Fluorescence that can be expressed by Si ₃ O ₁₂ , Ca _2.9 Ce _0.1 Sc _1.94 Mg _0.06 Si ₃ O ₁₂ , Ca _2.9 Ce _0.1 Sc _1.9 Mg _0.1 Si ₃ O _12, etc. Use the body Masui.

Further, among phosphors containing at least Ce as an emission center ion in the host crystal represented by the general formula (2), Ce _0.01 Ca _0.99 Sc ₂ O ₄ , Ce _0.007 Ca ₀ are particularly _{preferred. .993} Sc ₂ O ₄ and Ce _0.013 Ca _0.987 Sc ₂ O ₄ are preferred. Ce _0.01 Ca _0.94 Sr _0.05 Sc ₂ O ₄ , Ce _0.01 Ca _0.89 Sr _0.1 Sc ₂ O ₄ , Ce _0.01 Ca _{0. 84} Sr _0.15 Sc ₂ O ₄ is also an example of a preferred phosphor. These phosphors are preferable because the emission peak wavelength is relatively long and the luminance is high. Moreover, since the color purity of green can be improved by increasing Sr, it is preferable when used as an image display device.
In addition, these fluorescent substance may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  In the present invention, in order to obtain a light emitting device having particularly high color rendering properties among light emitting elements with little color misregistration, 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 a display backlight, an image display device (display), and an illumination device that are excellent in color reproducibility in the red region. When the peak value of the fluorescence intensity is shorter than 610 nm, the color reproducibility in the red region is lowered when used in combination with the blue LED, and when the wavelength is longer than 680 nm, the color rendering is increased. Tend to be lower.

As the red phosphor having a peak value of the fluorescence intensity in the wavelength range of 610 nm to 680 nm that can be contained in the phosphor mixture of the present invention, the above formulas (A) and (B), preferably Although it will not restrict | limit especially if the said formula (C) is satisfy | filled, since an oxide, nitride, and oxynitride are good in thermal stability, it is preferable. For example, MSi ₇ N ₁₀ : Eu, M ₂ Si ₅ N ₈ : Eu (where M represents one or more alkaline earth metals), preferably BaSi ₇ N ₁₀ : Eu, ( Ca, Ba, Sr) ₂ Si ₅ N ₈ : Eu and the like. 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 _a A _b D _c E _d X _e (3)
In the general formula (3), M is one or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. A represents one or more elements selected from the group consisting of divalent metal elements other than the M element, and D represents one or two elements selected from the group consisting of tetravalent metal elements. E represents one or more elements, E represents one or more elements selected from the group consisting of trivalent metal elements, and X represents one or more elements selected from the group consisting of O, N, and F Represents two or more elements.

Moreover, in said general formula (3), a, b, c, d, and e are numbers of the following ranges, respectively.
0.00001 ≦ a ≦ 0.1
a + b = 1
0.5 ≦ c ≦ 4
0.5 ≦ d ≦ 8
0.8 × (2/3 + 4/3 × c + d) ≦ e
e ≦ 1.2 × (2/3 + 4/3 × c + d)

  In the general formula (3), M is one or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. Among them, among them, one or more elements selected from the group consisting of Mn, Ce, Sm, Eu, Tb, Dy, Er, and Yb are preferable, and at least Eu is more preferable. .

  In the general formula (3), A is one or more elements selected from the group consisting of divalent metal elements other than the M element. Among them, Mg, Ca, Sr, and Ba It is preferable that it is 1 type, or 2 or more types of elements chosen from the group which consists of, and it is still more preferable that it is Ca.

  Further, in the general formula (3), D is one or more elements selected from the group consisting of tetravalent metal elements, among which Si, Ge, Sn, Ti, Zr, and Hf It is preferable that it is 1 type, or 2 or more types of elements chosen from the group which consists of, and it is still more preferable that it is Si.

  In the general formula (3), E is one or more elements selected from the group consisting of trivalent metal elements. Among them, B, Al, Ga, In, Sc, Y, It is preferably one or more elements selected from the group consisting of La, Gd, and Lu, and more preferably Al.

  Further, in the above general formula (3), X is one or more elements selected from the group consisting of O, N, and F. Among them, N may consist of N or N and O. preferable. When X consists of N and O, the ratio of O to (O + N) in the phosphor is preferably 0 <{(number of O atoms) / (number of O atoms + number of N atoms)} ≦ 0.5. If this value is too large beyond this range, the light emission intensity may be lowered. From the viewpoint of light emission intensity, this value is more preferably 0.3 or less, and 0.1 or less is more preferable because a red phosphor with good color purity having a light emission peak wavelength at a light emission wavelength of 640 nm to 660 nm is obtained. Further, by setting this value to 0.1 to 0.3, the emission peak wavelength can be adjusted to 600 nm to 640 nm, and a light emitting device with high luminance can be obtained because it approaches a wavelength region where human visibility is high. Therefore, it is preferable from another viewpoint.

  In the general formula (3), a represents the content of the element M serving as the emission center, and the ratio of the number of atoms M to (M + A) in the phosphor is a (where a = (number of M atoms)). / (Number of M atoms + number of A atoms)} is preferably 0.00001 or more and 0.1 or less. If the a value is smaller than 0.00001, the number of Ms as the light emission centers is small, and the light emission luminance may be lowered. When the a value is larger than 0.1, there is a risk that the brightness is lowered due to concentration quenching due to interference between M ions. In particular, when M is Eu, the a value is preferably 0.002 or more and 0.03 or less in that light emission luminance is increased.

  Further, in the above general formula (3), c is the content of D element such as Si, and is an amount represented by 0.5 ≦ c ≦ 4. Preferably, 0.5 ≦ c ≦ 1.8, more preferably c = 1. When c is smaller than 0.5 or larger than 4, the light emission luminance may be lowered. Further, in the range of 0.5 ≦ c ≦ 1.8, the emission luminance is high, and among them, c = 1 is particularly high.

  Furthermore, in the general formula (3), d is the content of E element such as Al, and is an amount represented by 0.5 ≦ d ≦ 8. Preferably, 0.5 ≦ d ≦ 1.8, more preferably d = 1. When the d value is smaller than 0.5 or larger than 8, there is a possibility that the light emission luminance is lowered. Further, in the range of 0.5 ≦ d ≦ 1.8, the light emission luminance is high, and in particular, d = 1 is particularly high in light emission luminance.

  Furthermore, in the above general formula (3), e is the content of X element such as N, and is 0.8 × (2/3 + 4/3 × c + d) or more, 1.2 × (2/3 + 4/3 × c + d) ) The amount shown below. More preferably, e = 3. If the value of e is out of the above range, the light emission luminance may decrease.

  Among the above compositions, a preferable composition having high emission luminance includes at least Eu in the M element, Ca in the A element, Si in the D element, Al in the E element, and N in the X element. Is included. Among them, an inorganic compound in which the M element is Eu, the A element is Ca, the D element is Si, the E element is Al, and the X element is N or a mixture of N and O is desirable. This phosphor is excited with light of at least 580 nm or less, and is most efficient particularly at 400 nm to 550 nm. The emission spectrum has a peak at 580 nm to 720 nm.

Further, as the red phosphor, a crystal close to a close-packed structure is preferable because it has good thermal stability. Further, those containing a tricoordinate nitrogen atom as the nitrogen atom contained in the red phosphor are preferable because of good thermal stability. Of the nitrogen atoms contained in the red phosphor, the content of tricoordinate nitrogen atoms is 20% or more, preferably 40% or more, and particularly preferably 60% or more. Here, M ₂ Si ₅ N ₈ : Eu (where M represents one or more alkaline earth metals) has a tricoordinate nitrogen atom content of 50%, and the above general formula The phosphor represented by (3), for example: (Ca, Sr) AlSiN ₃ : Eu, has a tricoordinate nitrogen atom content of 66%.

The particle size of the phosphor constituting the phosphor mixture of the present invention is usually 150 μm or less, preferably 50 μm or less, more preferably 30 μm or less. Beyond this range, when the white light emitting device is used, the emission color varies greatly, and when the phosphor and binder (sealing agent) are mixed, it becomes difficult to uniformly disperse the phosphor. There is a fear. The lower limit of the particle size is usually 1 μm or more, preferably 5 μm or more. Below this range, the luminous efficiency may be reduced. Further, it is preferable that the particle size distribution of the phosphor is relatively narrow.
These phosphors may be used alone or in combination of two or more in any combination and ratio.

  Depending on the balance of the luminous efficiency of the green phosphor and the red phosphor and how much the red phosphor absorbs the light emitted from the green phosphor, the green phosphor and the red phosphor When a mixture of phosphors is used, the green phosphor is usually 65% or more, preferably 70% or more, more preferably 80% by weight with respect to the total weight of the green phosphor and red phosphor. As mentioned above, it is preferable to contain 85% or more particularly preferably. When the weight percentage of the green phosphor is smaller than this range, a white light-emitting device having high luminance, high color rendering properties and a preferable white color cannot be obtained, and there is a possibility that a white light-emitting device with strong redness may be obtained. In order to obtain a white light emitting device, the weight percentage of the green phosphor is usually 99% or less, preferably 98% or less, more preferably 97% or less.

  Further, the absorption efficiency of the red phosphor at the emission wavelength from the semiconductor light emitting element is preferably larger than the absorption efficiency of the red phosphor at the emission peak wavelength of the green phosphor. The probability that the red phosphor is absorbed by the red phosphor and the red phosphor is excited to emit light, the emission from the green phosphor is absorbed by the red phosphor and the red phosphor is excited to emit light. This is preferable because a light-emitting element with higher probability and higher luminous efficiency can be obtained.

  The phosphor constituting the phosphor mixture of the present invention preferably has a luminous efficiency of 20% or more, more preferably 30% or more, still more preferably 40% or more, and the higher the luminous efficiency, the better. If the luminous efficiency of the phosphor is lower than 20%, a light emitting device with high luminance cannot be obtained. The luminous efficiency is defined as the quantum number of light emitted from the phosphor relative to the quantum number of light irradiated on the phosphor.

Hereinafter, a method of obtaining the luminous efficiency of the phosphor defined in the present invention by the product of the quantum absorption efficiency αq and the internal quantum efficiency ηi will be described.
First, a phosphor sample to be measured (for example, a powder form) is packed in a cell with a sufficiently smooth surface so that measurement accuracy is maintained, and is attached to a condenser such as an integrating sphere. Using a condenser such as an integrating sphere makes it possible to count all photons reflected from the sample and photoluminescence emitted from the sample, that is, eliminates photons that are not counted and fly out of the measurement system. Because.

  A light emission source for exciting the phosphor is attached to the integrating sphere. The light emission source is, for example, an Xe lamp or the like, and is adjusted using a filter, a monochromator, or the like so that the emission peak wavelength is, for example, 455 nm. The light from the light source adjusted so as to have a wavelength peak of 455 nm is applied to the sample to be measured, and the emission spectrum is measured using a spectroscopic measurement device such as MCPD2000 manufactured by Otsuka Electronics Co., Ltd. This measurement 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 Nabs 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. In other words, a reflector having a reflectance R of almost 100% with respect to the excitation light, for example, a reflector such as “Spectralon” manufactured by Labsphere (having a reflectance of 98% with respect to the excitation light of 450 nm) is used as a measurement target. It is attached to the spectrophotometer and the reflection spectrum Iref (λ) is measured. Here, the numerical value obtained from the reflection spectrum Iref (λ) by the following (formula 1) is proportional to N.

... (Formula 1)
Here, the integration interval may be substantially performed only in the interval where Iref (λ) has a significant value.

  The number of photons Nabs of the excitation light absorbed by the former sample is proportional to the amount obtained by the following (formula 2).

... (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 = Nabs / N = (Expression 2) / (Expression 1).

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

... (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 when αq is obtained.
And the luminous efficiency 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.

  The phosphor used in the present invention can be synthesized by a general solid phase reaction method. For example, it is manufactured by preparing a pulverized mixture by pulverizing and mixing a raw material compound constituting a phosphor element constituting a metal element source by a dry method or a wet method, and reacting the obtained pulverized mixture by heat treatment. be able to.

In the case of a nitride or oxynitride phosphor, an alloy containing at least two kinds of metal elements constituting the phosphor, preferably an alloy containing all of the metal elements constituting the phosphor, is obtained. The alloy can be manufactured by heat treatment under pressure in a nitrogen-containing atmosphere. An alloy containing a part of the metal element constituting the phosphor is prepared, and the obtained alloy is heat-treated in a nitrogen-containing atmosphere under pressure, and then a raw material that becomes the remaining metal element source constituting the phosphor It can also be produced by mixing with a compound and heat treatment. Thus, the phosphor manufactured through the alloy is a phosphor with few impurities and high luminance.
In addition, as a fluorescent substance which comprises the fluorescent substance mixture of this invention, if it is a range which does not impair the effect of this invention, you may contain fluorescent substance other than the fluorescent substance illustrated above.

[Explanation about light emitting device]
Hereinafter, the light emitting device of the present invention will be described. However, the description of the constituent requirements described below is a representative example of the embodiment of the light emitting device of the present invention, and the light emitting device of the present invention is not limited to these contents.
The light-emitting device of the present invention is a light-emitting device comprising a light source and at least one type of wavelength conversion material that emits light having different wavelengths by absorbing at least part of the light from the light source.
Here, any light source can be used as the light source as long as it emits light when a driving current is passed. For example, a semiconductor light emitting element that emits visible light, for example, a semiconductor light emitting element such as an LED or an LD can be used.

  As the wavelength conversion material used in the light emitting device of the present invention, any wavelength conversion material can be used as long as it absorbs at least part of light from the light source and emits light having a different wavelength. Usually, as the wavelength conversion material, a phosphor mixture containing at least two kinds of phosphors is used.

  Furthermore, the light-emitting device of the present invention includes a wavelength conversion material that absorbs visible light emitted from a light source such as a semiconductor light-emitting element and emits longer-wavelength visible light. This light-emitting device has little color misregistration. Therefore, the first light-emitting device of the present invention having such characteristics can be suitably used for an image display device such as a color liquid crystal display, a lighting device such as surface light emission, and the like.

[Characteristics of light emitting device]
A light-emitting device of the present invention is a light-emitting device containing the phosphor mixture described above, wherein a chromaticity coordinate value x of light emission obtained at a driving current density of 17.5 A / cm ² is x ₂ (17.5), When the chromaticity coordinate value x of light emission obtained at a driving current density of 70 A / cm ² is x ₂ (70), the light-emitting element satisfies the following formula (D).
(Equation 8)
−0.006 ≦ x ₂ (17.5) −x ₂ (70) ≦ 0.006 (D)

More preferred light-emitting element, 17.5A / cm ² of the chromaticity coordinate value y of the light emission obtained at a drive current density _{y 2 (17.5), 70A /} cm 2 of light emission colors obtained by the drive current density When the degree coordinate value y is y ₂ (70), the light emitting element satisfies the following formula (E).
(Equation 9)
−0.006 ≦ y ₂ (17.5) −y ₂ (70) ≦ 0.006 (E)

That is, the chromaticity coordinate value x and chromaticity of light emission obtained at a driving current density of 70 A / cm ² with respect to the chromaticity coordinate value x and chromaticity coordinate value y of light emission obtained at a driving current density of 17.5 A / cm ^2. The shift amount of the coordinate value y, that is, the difference between the chromaticity coordinate values [x ₂ (17.5) −x ₂ (70)] and / or [y ₂ (17.5) −y ₂ (70)] Is preferably within ± 0.006. When the deviation of the chromaticity coordinate value of the light emission accompanying the change of the driving current density is larger than ± 0.006, the color deviation increases when the driving current density is changed in order to control the amount of emitted light. Becomes unstable.

The smaller the shift amount between the chromaticity coordinate value x and the chromaticity coordinate value y, the better. The shift amounts [x ₂ (17.5) −x ₂ (70)] and [y ₂ (17.5) −y ₂ (70)] is more preferably within ± 0.005, even more preferably within ± 0.004, and even more preferably within ± 0.003. Further, it is preferable that both of the deviations [x ₂ (17.5) −x ₂ (70)] and [y ₂ (17.5) −y ₂ (70)] are within ± 0.006, It is more preferably within ± 0.005, even more preferably within ± 0.004, and even more preferably within ± 0.003.

[Example of specific configuration of light-emitting device]
The light emitting device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of a light-emitting device composed of a phosphor as a wavelength conversion material and a semiconductor light-emitting element, and FIG. 2 is a surface in which the light-emitting device shown in FIG. 1 is incorporated. It is typical sectional drawing which shows one Example of a light-emitting illuminating device. 1 and 2, 1 is a light emitting device, 2 is a mount lead, 3 is an inner lead, 4 is a semiconductor light emitting element, 5 is a phosphor-containing resin part, 6 is a conductive wire, 7 is a molding member, and 8 is a surface. A light emitting illumination device, 9 is a diffusion plate, and 10 is a holding case.

  As shown in FIG. 1, the light-emitting device 1 of the present invention has a general bullet shape, and a semiconductor light-emitting element 4 made of a GaN-based blue light-emitting diode or the like is disposed in the upper cup of the mount lead 2. It is fixed by being coated with the phosphor-containing resin portion 5. The phosphor-containing resin portion 5 is formed by mixing and dispersing the phosphor mixture of the present invention in a binder such as an epoxy resin or an acrylic resin and pouring the mixture into a cup. On the other hand, the semiconductor light-emitting element 4 and the mount lead 2 are electrically connected by a mounting member such as silver paste, and the semiconductor light-emitting element 4 and the inner lead 3 are electrically connected by a conductive wire 6, which are entirely made of epoxy resin or the like. Covered and protected by a mold member 7.

  FIG. 2 shows a surface-emitting illuminating device 8 incorporating the light-emitting device 1. As shown in FIG. 2, a rectangular holding case 10 in which the inner surface of the illuminating device is light-impermeable such as a white smooth surface. A large number of light-emitting devices 1 are arranged on the bottom surface, and a power source and a circuit (not shown) for driving the light-emitting device 1 are provided on the outside, and milky white is placed at a position corresponding to the lid portion of the holding case 10. A diffusion plate 9 such as an acrylic plate is fixed for uniform light emission.

Then, the surface emitting illumination device 8 is driven to apply blue voltage to the semiconductor light emitting element 4 of the light emitting device 1 to emit blue light or the like, and a part of the emitted light is converted in wavelength in the phosphor-containing resin portion 5. The phosphor mixture as a material absorbs and emits light having a longer wavelength. On the other hand, light emission with high color rendering properties is obtained by mixing with blue light or the like that is not absorbed by the phosphor. And is emitted upward in the drawing, and illumination light with uniform brightness is obtained within the surface of the diffusion plate 9 of the holding case 10.
Similarly, the light emitting device of the present invention can be incorporated as a light source of an image display device such as a color liquid crystal display.

[light source]
The light source is not particularly limited as long as it emits light when a driving current is passed, but it is preferable to use a light source having a light emission peak wavelength in the ultraviolet to visible light region. The emission peak wavelength of the light source is usually in the range of 370 nm or more, preferably 380 nm or more, and usually 500 nm or less, preferably 480 nm or less. When exceeding the upper limit of this range or falling below the lower limit, it becomes difficult to obtain a light emitting element with high luminous efficiency.
As long as the excitation light source has an emission peak wavelength in this range, a semiconductor light emitting device, a lamp, an electron beam, plasma, an electroluminescence device, and the like can be used, and in particular, a light emitting diode (LED) or a laser diode (LD) It is preferable to use the semiconductor light emitting element.

Examples of the material of the semiconductor light emitting device having the emission peak wavelength in the ultraviolet to visible light region include various semiconductors such as boron nitride (BN), silicon carbide (SiC), ZnSe, GaN, InGaN, InAlGaN, AlGaN, BAlGaN, and BInAlGaN. be able to. These elements can contain Si, Zn, or the like as an impurity element to serve as a light emission center. Among them, a nitride semiconductor containing Al or Ga, represented by In _X Al _Y Ga _1-XY N (where 0 <X <1, 0 <Y <1, X + Y ≦ 1), or In or A nitride semiconductor containing Ga (hereinafter sometimes referred to as “(In, Al, Ga) N-based compound semiconductor”) is capable of efficiently emitting short wavelengths of visible light from the ultraviolet region. Since it is possible to emit light stably even with respect to changes in temperature and driving current, it is suitable as a material for the light emitting layer.

  Moreover, as a preferable structure of the semiconductor light emitting device, a homostructure having a MIS junction, a PIN junction, a pn junction, or the like, a heterostructure, or a double hetero configuration is exemplified. In the semiconductor light emitting device, various emission wavelengths can be selected depending on the material of the semiconductor layer and the mixed crystal ratio. Further, the output can be further improved by adopting a single quantum well structure or a multiple quantum well structure in which the active layer is formed in a thin film in which a quantum effect is generated.

  Of these, (In, Al, Ga) N-based LEDs and LDs using (In, Al, Ga) N-based compound semiconductors are preferred. This is because (In, Al, Ga) N-based LEDs and the like have much larger light output and external quantum efficiency than SiC-based LEDs that emit light in this region, and are combined with wavelength conversion materials such as phosphors. This is because very bright light emission can be obtained with very low power. For example, for a current load of 20 mA, the (In, Al, Ga) N system usually has a light emission intensity more than 100 times that of the SiC system, and is more sensitive to changes in temperature and drive current during use than the GaAs system. It can emit light stably.

In (In, Al, Ga) N-based LEDs, etc., those having an Al _{X ′} Ga _{Y ′} N light emitting layer, a GaN light emitting layer, or an In _{X ′} Ga _{Y ′} N light emitting layer are preferable. 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. In (In, Al, Ga) N-based LDs, In _X Ga _Y N A multi-quantum well structure having a GaN layer and a GaN layer 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 (In, Al, Ga) N-based LED, those in which these light emitting layers are doped with Zn or Si or those without a dopant are preferable for adjusting the light emission characteristics.

The (In, Al, Ga) N-based LED has these light emitting layer, p layer, n layer, electrode, and substrate as basic components, and the light emitting layer is an n-type and p-type Al _X Ga _Y N layer. , A GaN layer or an In _X Ga _Y N layer sandwiched heterostructure is preferable because of high luminous efficiency, and a heterostructure having a quantum well structure has higher luminous efficiency. More preferred. As the substrate, materials such as sapphire, spinel, SiC, Si, ZnO, GaAs, and GaN are preferably used, and sapphire, ZnO, GaN, and the like are particularly preferably used.

The shape and size of the semiconductor light emitting element are not particularly limited, but a rectangular shape having a side perpendicular to the direction of flow of the drive current and having a side of usually 100 μm or more, preferably 200 μm or more can be used. For example, “ES-CEBL912” manufactured by EPISTAR, “C460MB” manufactured by Cree, or the like can be used.
Further, one semiconductor light emitting element may be used alone, or two or more semiconductor light emitting elements may be used in combination. Furthermore, only one type of semiconductor light emitting element may be used, or two or more types may be used in combination.

The drive current density of the light source is the drive current per unit area of the surface perpendicular to the flow direction of the drive current, and the value of the drive current passed through the light source is divided by the area of the surface perpendicular to the flow direction of the drive current. Can be obtained. When two or more semiconductor light emitting elements are connected in parallel and used, the value of the drive current passed through the light source can be obtained by dividing the sum of the area of the plane perpendicular to the drive current flow direction.
Further, the light source can have a structure capable of efficiently releasing heat by providing a heat sink or devising a package, if necessary.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[Example 1]
The phosphor mixture was obtained by mixing so that the weight percentage of the first phosphor was 94% and the weight percentage of the second phosphor was 6%. Here, as the first phosphor, the luminous efficiency when excited with light having a wavelength of 455 nm is 46%, and Ce as an activator is 0.06 mol (0.02 mol relative to 1 mol of the chemical composition formula Ca). Mol), an oxide phosphor having a chemical composition of Ca ₃ Sc ₂ Si ₃ O ₁₂ and having an emission peak wavelength at 505 nm was used. Further, the second phosphor has a luminous efficiency of 54% when excited with light having a wavelength of 455 nm, contains 0.008 mol of Eu as an activator, has a chemical composition of CaAlSiN ₃ , and has a chemical composition of 650 nm. A nitride phosphor having an emission peak wavelength was used.

The luminance and chromaticity coordinate value x obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm were measured while controlling the temperature so as to keep the temperature constant stepwise up to 160 ° C. The measurement result of luminance is shown in FIG. As a result, when the luminance [BR (25)] at 25 ° C. is 1, the luminance [BR (125)] at 125 ° C. is 0.92, and the luminance ratio [BR (125) / BR (25 )] Was 0.92. In addition, the chromaticity coordinate value x [x ₁ (25)] at 25 ° C. is 0.404, and the chromaticity coordinate value x [x ₁ (25)] at 125 ° C. is 0.418. The difference [x ₁ (25) −x ₁ (25)] between the values x was 0.014. Regarding the measurement of luminance and chromaticity coordinate value x, in order not to be affected by the excitation light having a wavelength of 455 nm, the fluorescence spectrum of less than 470 nm from the phosphor mixture is not counted and only the fluorescence spectrum of 470 nm or more is used. And calculated.

  In addition, a bullet-type white light emitting device was produced by the following procedure. First, an LED that emits light at a wavelength of 460 nm (“C460MB” manufactured by Cree) was mounted on a cup portion of a frame for a bullet-type LED using a conductive mounting member made of silver paste. Next, the electrode of the LED and the inner lead were bonded using Au wire. Then, a mixture of a phosphor and a resin (hereinafter referred to as a phosphor paste) obtained by thoroughly mixing an epoxy resin at a ratio of 10 g with 1 g of the phosphor mixture is used as a cup of a frame on which an LED is mounted. Poured into the part. This was held at 120 ° C. for 1 hour to cure the epoxy resin. Next, the frame on which the LED and the phosphor were mounted as described above was inserted into a bullet type mold into which epoxy resin was poured, and held at 120 ° C. for 1 hour. After the resin was cured, it was removed from the mold to obtain a shell-type white light emitting device.

The white light emitting device thus obtained was driven at a current density of 17.5 A / cm ^{2 to} 70 A / cm ² at a current of 10 mA to 40 mA at room temperature (about 24 ° C.), and all the light emission from the white light emitting device was achieved. Was received by an integrating sphere and introduced into a spectroscope by an optical fiber, and an emission spectrum was measured. As emission spectrum data, a numerical value of emission intensity was recorded every 5 nm in the range of 380 nm to 780 nm. As a result, when this white light emitting device is driven at a current of 10 mA, the chromaticity coordinate values x and y are 0.288 and 0.308, respectively, and when driven at a current of 40 mA, the chromaticity coordinate values x and y are respectively It was 0.291 and 0.309. This is because the shift amount of the chromaticity coordinate value [x] with respect to the driving current of the blue LED in the range of 10 mA to 40 mA, that is, the change in the current density range of 17.5 A / cm ^{2 to} 70 A / cm ^2. ₂ (17.5) -x ₂ (70)] and [y ₂ (17.5) -y ₂ (70)] are extremely small, 0.003 and 0.001, respectively, and the amount of emitted light accompanying the increase or decrease of the drive current. It shows that the color shift is very small with respect to the change of.

  Further, when the average color rendering index Ra was determined by the method defined in JIS Z 8726 for this white light-emitting device, Ra was 90, indicating good color rendering properties. This white light emitting device has a significantly high average color rendering index as compared with a quasi-white light emitting device combining a blue LED and an yttrium aluminum garnet phosphor, which is a conventional product, and exhibits good light emission.

In addition, for comparison with the light emitting device of the present invention, the luminescence intensity was measured for a pseudo white light emitting device combining a blue LED and a yttrium aluminum garnet phosphor as a conventional product, and the chromaticity coordinate value was obtained. As a result, when driven at a current of 10 mA, the chromaticity coordinate values x and y are 0.321 and 0.314, respectively, and when driven at a current of 40 mA, the chromaticity coordinate values x and y are 0.314, 0,. 306, and the deviation amount of the chromaticity coordinate value [x ₂ (17] with respect to the driving current of the blue LED in the range of 10 mA to 40 mA, that is, the change in the current density of 17.5 A / cm ^{2 to} 70 A / cm ² _{.5) -x 2 (70)]} , [y 2 (17.5) -y 2 (70)] , respectively -0.007, large as -0.008, the change in light emission amount caused by the increase and decrease of the drive current On the other hand, the color shift was very large as compared with the light emitting device of the present invention.

  The luminance and chromaticity coordinate value x obtained by exciting the yttrium aluminum garnet-based phosphor with blue light having a peak wavelength of 455 nm while heating to 160 ° C. were measured. The measurement result of luminance is shown in FIG. As a result, when the luminance [BR (25)] at 25 ° C. is 1, the luminance [BR (125)] at 125 ° C. is 0.68, and the luminance ratio [BR (125) / BR (25 )] Was 0.68, and the temperature quenching was large. As described above, the temperature quenching of the yttrium aluminum garnet phosphor is one of the causes of a large color shift with respect to the change in the amount of emitted light accompanying the increase or decrease of the drive current of the white light emitting device. The average color rendering index Ra of this conventional product was as low as 79.

  From the above results, by using the phosphor mixture of the present invention and the light emitting device incorporating the phosphor mixture, the color shift is small and stable with respect to the change in the amount of emitted light due to the increase or decrease of the drive current, compared with the conventional product. It is apparent that an image display device having excellent color reproducibility and an illumination device having high color rendering properties and little color shift with respect to changes in environmental temperature and light emission amount can be obtained.

It is typical sectional drawing which shows one Example of the light-emitting device comprised from the fluorescent substance mixture of this invention as a wavelength conversion material, and a semiconductor light-emitting device. It is typical sectional drawing which shows one Example of the surface emitting illumination device incorporating the light emitting element shown in FIG. Phosphor mixture with conventional products in which擬白color light emitting device yttrium aluminum garnet are incorporated into phosphor of Example 1 (Y, Gd) 3 Al 5 O 12: shows the temperature dependence of the intensity of fluorescence of _Ce . In the figure, the solid line represents the phosphor mixture of Example 1, and the dotted line represents the yttrium aluminum garnet phosphor.

Explanation of symbols

1: Light emitting device
2: Mount lead
3; Inner lead
4; Semiconductor light emitting device
5; Phosphor-containing resin part
6; Conductive wire
7: Mold member
8; Surface emitting lighting device
9: Diffuser
10: Holding case

Claims (8)

A phosphor mixture containing at least two kinds of phosphors, wherein the phosphor mixture is a green phosphor having a peak value of fluorescence intensity in a wavelength range of 500 nm to 550 nm and represented by the following general formula (1) And at least one red phosphor having a peak value of fluorescence intensity in the wavelength range of 610 nm to 680 nm and represented by the following general formula (3): And the phosphor brightness obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm at 25 ° C. is BR (25), the chromaticity coordinate value x is x ₁ (25), and at 125 ° C. The following formulas (A) and (B) are satisfied when the luminance of fluorescence obtained by excitation with blue light having a peak wavelength of 455 nm is BR (125) and the chromaticity coordinate value x is x ₁ (125): A phosphor mixture.
(Equation 1)
0.85 ≦ BR (125) / BR (25) ≦ 1.15 (A)
−0.03 ≦ x ₁ (25) −x ₁ (125) ≦ 0.03 (B)
M ¹ _a M ² _b M ³ _c O _d (1)
(In the general formula (1), M ¹ represents Ca, M ² represents Sc, M ³ represents Si, 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 _a Ab _b D _c E _d X _e (3)
(In the above general formula (3), M represents Eu, A represents Ca and / or Sr,
D represents Si, E represents Al, X represents N, a, b, c, d, and e are each
It is a number in the following range.
0.00001 ≦ a ≦ 0.1
a + b = 1
0.5 ≦ c ≦ 4
0.5 ≦ d ≦ 8
0.8 × (2/3 + 4/3 × c + d) ≦ e
e ≦ 1.2 × (2/3 + 4/3 × c + d)) The phosphor chromaticity coordinate value y obtained by exciting the phosphor mixture with blue light having a peak wavelength of 455 nm at 25 ° C. is y ₁ (25), and obtained by exciting it with blue light having a peak wavelength of 455 nm at 125 ° C. The phosphor mixture according to claim 1, wherein the following formula (C) is satisfied when the chromaticity coordinate value y of fluorescence is y ₁ (125).
(Equation 2)
−0.03 ≦ y ₁ (25) −y ₁ (125) ≦ 0.03 (C)   The phosphor mixture according to claim 1 or 2, wherein the green phosphor is 65% or more by weight with respect to the total weight of the green phosphor and the red phosphor.   A light emitting device comprising: a light source that emits light when a drive current is passed through; and at least one type of wavelength conversion material that absorbs at least part of light from the light source and emits light having a different wavelength. A light emitting device comprising the phosphor mixture according to claim 1. 17.5A / cm _x 2 (17.5) chromaticity coordinate x of the light emission obtained at a drive current density of ^2, 70A / cm ² of the chromaticity coordinates x of the light emission obtained at a drive current density _{x 2} The light-emitting device according to claim 4, wherein, when (70) is satisfied, the following formula (D) is satisfied.
(Equation 3)
−0.006 ≦ x ₂ (17.5) −x ₂ (70) ≦ 0.006 (D) 17.5A / cm _y 2 (17.5) chromaticity coordinate y of the light emission obtained at a drive current density of ^2, 70A / cm ² of the chromaticity coordinate value y of the light emission obtained at a drive current density _{y 2} The light-emitting device according to claim 4, wherein the following formula (E) is satisfied when (70) is satisfied.
(Equation 4)
−0.006 ≦ y ₂ (17.5) −y ₂ (70) ≦ 0.006 (E)   An image display device comprising the light-emitting device according to claim 4.   An illumination device comprising the light-emitting device according to claim 4.