JP6349771B2 - Lighting device - Google Patents

Description

  The present invention relates to an illumination device that excites a phosphor and outputs light.

  In order to show freshly lit meat (especially beef), the contrast between the reddish portion and the sashi portion of the meat is important. In other words, there is a need for lighting that shows the reddish red vividly but does not show the white color of the sardish red. In order to obtain this effect, a fluorescent lamp dedicated to meat has been conventionally used.

  However, from the viewpoint of ecology and energy saving, there has been an increasing demand to replace meat lighting with fluorescent light-emitting diode (LED) lighting. In order to realize LED lighting for meat, various methods have been studied (for example, refer to Patent Document 1). However, the performance of LED lighting is still inadequate as an illuminating device that shows meat freshly.

JP 2012-64888 A

  In view of the above problems, an object of the present invention is to provide an illuminating device that can show meat freshly using an LED.

According to one aspect of the present invention, a blue LED , a red LED having a peak wavelength of 645 nm or more and 675 nm or less, and a green light having a peak wavelength of 530 nm or more and 550 nm or less excited by light emitted from the blue LED. A green phosphor having a spectral half width of 60 nm or less that is emitted, the blue LED, and a cover resin disposed so as to cover the red LED ; and color rendering in the CIELAB (L ^* a ^* b ^* ) color space White output light in which coordinates (a ^* , b ^* ) corresponding to VS14 of the Munsell color sample used for the evaluation number CQS satisfy the relationship of b ^* ≧ −0.75 × a ^* + α (77 ≦ α ≦ 87) Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the illuminating device which can show meat freshly using LED can be provided.

It is typical sectional drawing which shows the structure of the illuminating device which concerns on embodiment of this invention. It is a graph which shows the spectral characteristic of myoglobin. It is a graph which shows the distribution in the CIELAB (L ^* a ^* b ^* ) color space of myoglobin. It is the graph which expanded the area A of FIG. It is a graph explaining the distribution change in CIELAB (L ^* a ^* b ^* ) color space when whitening is advanced. It is a graph which shows distribution on the CIELAB (L ^* a ^* b ^* ) color space of a meat fluorescent lamp and a high color rendering LED. It is a table | surface which shows the example of the color rendering index of a meat fluorescent lamp and high color rendering LED. It is a graph which shows the spectral characteristic of red LED used for the illuminating device which concerns on embodiment of this invention. It is a graph which shows the spectral characteristic of the light radiate | emitted from a green fluorescent substance. It is a typical top view which shows the structure of the illuminating device which concerns on embodiment of this invention. It is a typical top view which shows the other structure of the illuminating device which concerns on embodiment of this invention. It is a graph which shows the example which optimizes the spectral characteristic of the output light of the illuminating device which concerns on embodiment of this invention. It is a graph which shows the example which optimizes distribution in the CIELAB (L ^* a ^* b ^* ) color space of the output light of the illuminating device which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the shape, structure, arrangement, etc. of components. It is not specified to the following. The embodiment of the present invention can be variously modified within the scope of the claims.

  As shown in FIG. 1, the lighting device 1 according to the embodiment of the present invention includes a blue LED 10 that emits blue light, a red LED 20 that emits red light, and a cover resin disposed so as to cover the blue LED 10 and the red LED 20. 30. The cover resin 30 includes a green phosphor 41 that emits green light when excited by the light emitted from the blue LED 10 and a red phosphor 42 that emits red light. The illuminating device 1 shown in FIG. 1 has a structure in which a blue LED 10 and a red LED 20 are arranged on the bottom surface of a concave portion of a package 50 having a concave portion whose bottom is narrower than the opening. The recess of the package 50 is filled with the cover resin 30. Silicon resin or the like can be used for the cover resin 30.

As will be described in detail later, in the CIELAB (L ^* a ^* b ^* ) color space, the lighting device 1 has coordinates (a ^* , b ^* ) corresponding to the VS14 of the Munsell color sample used for the color rendering index CQS. The white output light L satisfying the relationship of b ^* ≧ −0.75 × a ^* + α (77 ≦ α ≦ 87) is output. As described above, in the lighting device 1 according to the embodiment of the present invention, the color rendering index CQS (Color Quality Scale) is used to set the color rendering properties of the output light L that is transmitted through the cover resin 30 and output. doing.

  Conventionally, a color rendering index CRI (Color Rendering Index) has been used as a color rendering index. However, when the illumination light for meat using LEDs is set based on the color rendering index R9 representing the red component using the color rendering index CRI, the effect obtained with the fluorescent lamp for meat Cannot be reproduced. This is considered to be due to the following reason.

  In the Ra evaluation system based on the color rendering index CRI, the color rendering property is calculated by the distance from the true value in the color space. However, when the color shifts to the higher saturation, the color tone is better for the human eye even if the shift from the true value is the same as when the shift is lower. It is likely to be visible. For this reason, even if the color rendering property is evaluated with reference to the color rendering index CRI and the illumination light is set, it is difficult to show the meat with good freshness.

  Specifically, when the output light of LED illumination was set based on the color rendering index CRI, the contrast between the reddish portion of meat and the white sashi portion was insufficient. In addition, when the color temperature is set to be low so as to make the reddish portion appear vividly, there is a problem that the white color cannot be seen vividly. Even with LED lighting, which is said to have high color rendering properties, sufficient effects could not be obtained.

For this reason, the present inventors paid attention to the color rendering index CQS as a new index to replace the color rendering index CRI in order to evaluate the color rendering property of the illumination light for meat. More specifically, the coordinates (a ^* , b ^* ) corresponding to VS1 to VS15 of the Munsell color sample used for the color rendering evaluation number CQS are used as an index of the output light L of the lighting device 1. Details will be described below.

  The red component of meat consists of a water-soluble protein called myoglobin (Mb). Myoglobin is formed from a porphyrin cyclic compound complexed with iron and globin (protein), and plays a role in storing oxygen in muscle. The freshest state of myoglobin is reduced RMb, which is not supplied with oxygen but consumes stored oxygen. The fresh state is then oxygen-type OMb that binds to oxygen rather than oxidation at the surface layer. The reduced RMb and the oxygen OMb are fresh, and the red color of the meat is vivid. Thereafter, myoglobin shifts to meth-type MMb which turns brownish brown due to degradation due to auto-oxidation.

FIG. 2 shows the spectral characteristic of reduced RMb as characteristic S1, the spectral characteristic of oxygen-type OMb as characteristic S2, and the spectral characteristic of meth-type MMb as characteristic S3 (the same applies hereinafter). The present inventors investigated the reflection spectrum of myoglobin in each state of reduced RMb, oxygen-type OMb, and meth-type MMb. Specifically, the reflection spectrum was examined in the CIELAB (L ^* a ^* b ^* ) color space in correspondence with the VS value of the Munsell color sample used for the color rendering index CQS. As a result, as shown in FIG. 3, it was confirmed that the slope between VS10 and VS14 is almost the same between the reduced RMb and the oxygen OMb. Here, “inclination between VS10 and VS14” is an inclination with respect to the a ^* axis of an imaginary line connecting the coordinates of VS10 to VS14 in the CIELAB (L ^* a ^* b ^* ) color space. In FIG. 3, the coordinates of VS10 to VS14 of the reduced type RMb, the oxygen type OMb, and the meth type MMb are surrounded by a broken line.

As shown in FIG. 3, it was confirmed that there is a large difference in the coordinates (a ^* , b ^* ) of VS14 between reduced RMb, oxygen-type OMb, and metho-type MMb. That is, it was found that the value of VS14 is extremely important in the difference in appearance between met-type MMb, fresh reduced RMb, and oxygen-type OMb.

Here, an area (first quadrant) including VS10 to VS14 in the CIELAB (L ^* a ^* b ^* ) color space is defined as area A as shown in FIG. FIG. 4 shows an enlarged view of the area A. The average slope between VS10 and VS14 for oxygen type OMb is -0.75. An imaginary line connecting the coordinates of VS10 to VS14 with respect to the oxygen type OMb shown in FIG. 4 is represented by b ^* = − 0.75 × a ^* + 86.22. On the other hand, CIELAB (L ^* a ^* b ^* ) by this oxygen type OMb is a notation of red component of meat to the last, and if it tries to develop into white illumination without impairing this color component as much as possible, the first quadrant is always L ^* a ^* b ^* move in the direction of contraction, the second and fourth quadrants move in the direction of expansion. Whitening requires a certain color balance. From these scrutiny, the lighting device 1 outputs white output light L in which VS10 to VS14 are maintained at b ^* = − 0.75 × a ^* + α (77 ≦ α ≦ 87). Hereinafter, an imaginary line represented by b ^* = − 0.75 × a ^* + α in the area A is referred to as “border line B”. The border line B shown in FIG. 4 is a straight line represented by b ^* = − 0.75 × a ^* + 86.22 connecting the coordinates of VS10 to VS14 with respect to the oxygen type OMb.

Note that the intercept α, which is the intersection of the border line B with the b ^* axis, is set according to the desired color temperature for the output light L, as will be described later. The larger the intercept α, the lower the color temperature.

As shown in FIG. 3 and FIG. 4, in VS10 to VS13, the difference between the reduced RMb or oxygen type OMb and the meth type MMb is small. For this reason, in the lighting device 1, the coordinates (a ^* , b ^* ) are set so that at least VS14 does not become smaller than the border line B represented by b ^* = − 0.75 × a ^* + α. That is, in the lighting device 1, the coordinates (a ^* , b ^* ) corresponding to the VS14 of the Munsell color sample used for the color rendering index CQS in the CIELAB (L ^* a ^* b ^* ) color space are shown in Expression (1). The white output light L that satisfies the relational expression is output:

b ^* ≧ −0.75 × a ^* + α (1)

FIG. 5 shows a graph of the distribution change in the CIELAB (L ^* a ^* b ^* ) color space when whitening is advanced. The average slope line B0 shown in FIG. 5 is a straight line represented by b ^* = − 0.75 × a ^* + 86.22 defined by VS10 to VS14 for the oxygen type OMb. As whitening proceeds, the distribution in the CIELAB (L ^* a ^* b ^* ) color space approaches point symmetry about the origin. That is, as shown by the arrows in FIG. 5, the distribution is reduced so as to approach the origin in the first quadrant and the third quadrant, and the distribution is widened away from the origin in the second quadrant and the fourth quadrant. Therefore, in the area A that is the first quadrant, the border line B is set so that the intercept α is smaller than the average inclined line B0.

That is, the border line B maintains the inclination (b ^* / a ^* = − 0.75) of VS10 to VS14 of the oxygen type OMb, and the VS10 of the reduced type RMb and the oxygen type OMb even when the whitening is advanced. It is set to include all of VS14. As described above, in the lighting device 1, the output light L is set so that VS10 to VS14 are equal to or greater than the border line B considering the change in distribution in the CIELAB (L ^* a ^* b ^* ) color space due to whitening. Yes.

  The intercept α shown in Equation (1) is set according to the desired color temperature for the output light L. Specifically, 77 ≦ α ≦ 87, which corresponds to 6500K to 2500K. The larger the intercept α, the lower the color temperature of the output light L.

In general, there is a restriction of desired chromaticity (color temperature) in LED for lighting. Formula (1) is a borderline on the CIELAB (L ^* a ^* b ^* ) color space for making the red component of meat look vivid, but at the same time, it must satisfy the use as white illumination. Therefore, a range occurs in α. That is, α is determined for the desired chromaticity, and the expression (1) is fixed. If the line is below this line, the vividness of the red component of myoglobin is lost. . However, due to chromaticity restrictions, the upper limit is naturally determined corresponding to each desired chromaticity. In this sense, the expression (1) is a border line that sets the lower limit of the expression of the red component based on the oxygen type OMb.

In the following, it will be described that the effect of vividly showing the red color of meat by a meat fluorescent lamp conventionally used is difficult to realize with a high color rendering LED. FIG. 6 shows an example in which the distribution of meat fluorescent lamps and high color rendering LEDs on the CIELAB (L ^* a ^* b ^* ) color space is compared. In FIG. 6, the characteristic of the meat fluorescent lamp is P1, the characteristic of the high color rendering LED whose average color rendering index Ra is 85 (hereinafter referred to as “LED1”) is P21, and the high color rendering LED whose average color rendering index Ra is 95. The characteristic of (hereinafter referred to as “LED2”) is indicated as P22.

  As shown in FIG. 6, in the illumination by LED1 and LED2, compared with the meat fluorescent lamp, the distributed area is narrow and the saturation is insufficient. This is because high color rendering LEDs place importance on spectral continuity. In particular, the difference in distribution is large in a region surrounded by a broken line including VS14. FIG. 7 shows the color rendering index R9 (red component) of the meat fluorescent lamp, LED1, and LED2. In the case of a meat fluorescent lamp, the color rendering index R9 is -91, indicating a unique numerical value compared to a high color rendering LED. As described above, it is difficult to obtain the effect of the meat fluorescent lamp by the high color rendering LED.

  As described above, a high color rendering LED that places importance on spectral continuity has low saturation, and it is difficult to develop a bright red color. Therefore, in order to make red appear vivid, it is effective to make the peak value of the spectral intensity stand out by using a light source or a phosphor that outputs light having a narrow spectral half width.

  In the illuminating device 1, the spectral characteristic that emphasizes the peak value at the red wavelength is realized by reducing the intensity near 600 nm corresponding to the yellow wavelength band, that is, between the green wavelength band and the red wavelength band. . Thereby, the illuminating device 1 outputs the output light L in which the coordinate corresponding to VS14 satisfies Formula (1).

  Specifically, a red LED 20 that outputs red light having a narrow spectrum half width is used. For example, an LED of an aluminum, indium, gallium, phosphorus (AlGaInP) type whose emission spectrum peak value wavelength (hereinafter referred to as “peak wavelength”) is 645 nm or more and 675 nm or less is shown in FIG. Used for red LED20.

Further, as the green phosphor 41, a green phosphor having a spectral half width of green light that is excited and output by the blue LED 10 is as narrow as possible. FIG. 9 shows an example in which emission spectra of green phosphors are compared. In FIG. 9, the characteristic G1 is the spectral characteristic of β sialon (β-SiAlON), the characteristic G2 is the spectral characteristic of barium orthosilicate (BOS), and the characteristic G3 is the spectral characteristic of yttrium aluminum garnet (YAG). It is. As shown in FIG. 9, in these phosphors, β-SiAlON is preferably used as the green phosphor 41 because the half-width of the spectrum is the narrowest in β-SiAlON. The peak wavelength of the green light output from β-SiAlON is in the range of 530 nm to 550 nm and the spectral half width is about 40 nm. For example, an oxynitride material such as (Si, AL) ₆ (O, N) ₈ : EU is used for the green phosphor 41. Further, a thiogallate green phosphor, such as (Sr, Ca) Ga ₂ S ₄ : Eu, may be used for the green phosphor 41. The spectral half width of the green phosphor 41 is preferably 60 nm or less.

  In addition, in order to ensure the brightness of the output light L of the illuminating device 1, it is preferable to select the green fluorescent substance 41 from the fluorescent substance which carries out an allowable transition. For the same reason, the red LED 20 emits light by direct transition, and it is preferable to select a red LED having a double hetero (DH) structure.

  Further, from the viewpoint of adjusting the chromaticity, it is preferable to add a phosphor that outputs a small amount of deep red light to the cover resin 30. In other words, the cover resin 30 contains the red phosphor 42 that emits red light having a longer peak wavelength than the peak wavelength of the output light of the red LED 20 when excited by the emitted light of the blue LED 10. Thereby, the effect which the red of the meat irradiated by the illuminating device 1 seems to increase further is acquired. As the red phosphor 42, for example, a nitride-based red phosphor (CASN) can be employed.

  As described above, in the luminaire 1, VS <b> 10 to VS <b> 14 of the output light L are adjusted to the border line B or higher. For example, the following combinations can be adopted for the lighting device 1. That is, a blue LED having a peak wavelength of about 440 nm to 460 nm is used as the blue LED 10, and a red LED made of AlGaInP is used as the red LED 20. For example, an LED made of indium gallium nitride (InGaN) can be used as the blue LED 10. Further, β-SiAlON is used as the green phosphor 41 included in the cover resin 30. Furthermore, the cover resin 30 contains a nitride-based red phosphor (CASN) as the red phosphor 42 excited by blue light. The content of the red phosphor 42 in the cover resin 30 is about 0.02% by weight.

  By the way, the light of the red LED 20 that is easily transmitted at a long wavelength and has high saturation is likely to be a spot, and color mixing is difficult. However, in view of the quality of the lighting device 1, it is preferable that the light emitting point of the red LED 20 is not visible from the outside. For this reason, mixing the scattering material into the cover resin 30 is effective for preventing the lighting device 1 from generating a light emitting point.

  As the scattering material, a silica-based scattering material or the like can be employed. In addition, when the content rate of a scattering material is too low, the effect which scatters red light is low, and there exists a possibility that the light emission point may arise in the cover resin 30. On the other hand, if the content ratio of the scattering material of the cover resin 30 is too high, problems in manufacturing such as difficulty in molding due to the viscosity of the cover resin 30 becoming high. According to the study by the present inventors, the content of the scattering material in the cover resin 30 is preferably about 15 to 35% by weight.

  All the above materials are arranged in the same package 50 to constitute the lighting device 1. In FIG. 10, the example of the top view of the illuminating device 1 is shown. In the illumination device 1 shown in FIG. 10, the blue LED 10 and the red LED 20 mounted on the package 50 are connected in series with an electrode 60 that is connected to a power source (not shown) that supplies a drive current. Further, as shown in FIG. 11, the blue LED 10 connected to the electrode 61 and the red LED 20 connected to the electrode 62 may be connected in parallel.

In the illumination device 1, the spectral characteristics of the output light L and the distribution in the CIELAB (L ^* a ^* b ^* ) color space can be optimized by setting the specification of the blue LED 10. For example, the size of the blue component and the green component of the output light L can be adjusted by appropriately selecting the number of blue LEDs 10, the drive current ratio between the blue LED 10 and the red LED 20, the wavelength of the output light of the blue LED 10, and the like. . Thereby, for example, the intensity near 600 nm is lowered as shown by the arrow in FIG. Thus, the peak value of red light can be made to stand out by lowering the minimum value of the spectral intensity between the peak wavelength Pg corresponding to green light and the peak wavelength Pr corresponding to red light. As a result, as indicated by an arrow in FIG. 13, the coordinates (a ^* , b ^* ) corresponding to VS14 in the CIELAB (L ^* a ^* b ^* ) color space move so as to increase in the a ^* direction. In other words, the red color can be shown more freshly.

As described above, the lighting device 1 according to the embodiment of the present invention has coordinates (a) corresponding to the VS14 of the Munsell color sample used for the color rendering index CQS in the CIELAB (L ^* a ^* b ^* ) color space. ^* , B ^* ) outputs white output light L satisfying the relationship of b ^* ≧ −0.75 × a ^* + α (77 ≦ α ≦ 87). According to the illuminating device 1, the peak value of the spectral characteristics is made to stand out in the wavelength band corresponding to the red color of the output light L, and the coordinates of the VS 14 can be increased in the a ^* direction in the CIELAB (L ^* a ^* b ^* ) color space. Thereby, red of meat can be shown vividly while white parts such as sashi are vividly shown. As a result, it is possible to provide the lighting device 1 that shows fresh meat using LEDs.

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 ... Lighting device 10 ... Blue LED
20 ... Red LED
30 ... Cover resin 41 ... Green phosphor 42 ... Red phosphor 50 ... Package

Claims (5)

A blue LED,
A red LED having a peak wavelength of 645 nm or more and 675 nm or less;
A green phosphor that emits green light having a peak wavelength of not less than 530 nm and not more than 550 nm when excited by the emitted light of the blue LED, and covers the blue LED and the red LED; With placed cover resin
With
In the CIELAB (L ^* a ^* b ^* ) color space, the coordinates (a ^* , b ^* ) corresponding to VS14 of the Munsell color sample used for the color rendering index CQS are b ^* ≧ −0.75 × a ^* + α ( 77 ≦ α ≦ 87), which outputs white output light satisfying the relationship. The lighting device according to claim 1 , wherein the green phosphor is β-SiAlON. The lighting device according to claim 1 , wherein the red LED is an AlGaInP-based LED. Wherein the cover resin, said excited blue LED of the emitted light, wherein the peak wavelength than the peak wavelength of the output light of the red LED further comprises a red phosphor for emitting red light of a long wavelength Item 4. The lighting device according to any one of Items 1 to 3 . 5. The illumination device according to claim 1, wherein a peak wavelength of the blue LED is 440 nm or more and 460 nm or less.

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