Lighting device

Abstract

The present invention provides a lighting device that can suppress meat discoloration more effectively than conventional devices when irradiating meat with light emitted from a light source. [Solution] The lighting device is equipped with a light source whose target for light irradiation is meat. The spectral distribution of the light emitted from this light source includes a first peak of light intensity in the wavelength band of 430 nm to 470 nm, a second peak of light intensity in the wavelength band of 490 nm to 540 nm, and a third peak of light intensity in the wavelength band of 650 nm to 670 nm. The full width at half maximum of the third peak is 20 nm or less.

Description

Technical Field

[0001] The present disclosure relates to a lighting device for meat.

Background Art

[0002] Conventionally, lighting devices having a light source whose light irradiation target is meat such as beef, pork, chicken (for example, lean meat) are known.

[0003] For example, Patent Document 1 discloses a light emitting device having a light emitting element and two or more phosphors that are excited by the light from the light emitting element to emit fluorescence. In the emission spectrum of the mixed color light of the light emitting element and the phosphor, the emission of the light emitting element is taken as the first peak, 500 nm to 600 nm is taken as the second peak, 600 nm to 780 nm is taken as the third peak, and when the emission intensity of the first peak is set to 1, the emission intensity of the second peak is 0.4 to 0.7, the emission intensity of the third peak is 0.8 to 1.2, the minimum intensity between the first peak and the second peak is 0.1 to 0.3, and the minimum intensity between the second peak and the third peak is 0.1 to 0.3.

[0004] Patent Document 2 discloses a white light emitting device including a solid light emitting element that emits light in a wavelength region of 10 to 550 nm, an optical filter provided on the light emitting surface side of the solid light emitting element that reduces the transmission of light of a specific wavelength, and a wavelength conversion member provided between the solid light emitting element and the optical filter. The wavelength conversion member is excited by the light from the solid light emitting element and includes a first phosphor that converts light to light having a peak wavelength in a wavelength region of 630 to 680 nm and a second phosphor that converts light to light having a peak wavelength in a wavelength region of 500 to 550 nm, and the light intensities emitted from the first phosphor and the second phosphor are configured to be approximately the same. The optical filter is characterized by reducing the transmission of light in a wavelength region of 560 to 620 nm.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-136587 [Patent Document 2] Japanese Patent Publication No. 2012-204413 [Overview of the project] [Problems that the invention aims to solve]

[0006] As an example, this disclosure aims to provide a lighting device that can suppress meat discoloration more effectively than conventional devices when irradiating meat with light emitted from a light source. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the present disclosure is a lighting device equipped with a light source for which the light irradiated object is meat, wherein the spectral distribution of the emitted light of the light source is a first peak of light intensity in the wavelength band of 430 nm to 470 nm, a second peak of light intensity in the wavelength band of 490 nm to 540 nm, and a peak of light intensity in the wavelength band of 650 nm to 670 nm below It has a third peak in light intensity present in the wavelength band, and the full width at half maximum of the third peak is 20 nm or less. [Effects of the Invention]

[0008] One aspect of the present disclosure provides the effect of suppressing meat discoloration when the light emitted from the light source is irradiated onto the meat more effectively than in conventional methods. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a plan view of an example of a lighting device according to the first embodiment. [Figure 2] Figure 2 is a plan view of the comparison device. [Figure 3] Figure 3 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device of the first embodiment, compared with the spectral distribution of the light emitted from the light source of a conventional device. [Figure 4]Figure 4 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device of the first embodiment, compared with the spectral distribution of the light emitted from the light sources of the conventional device and the comparative device. [Figure 5] Figure 5 shows the results of the color rendering evaluation of the light source of the lighting device in the fourth embodiment of the first embodiment. [Figure 6] Figure 6 shows an example of a lighting device according to the second embodiment. [Figure 7] Figure 7 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device in the second embodiment, compared with the spectral distribution of the light emitted from the light source of a conventional device. [Figure 8] Figure 8 is a grayscale photograph comparing the surface changes of a beef sample when the light emitted from the light source of the lighting device in the second embodiment is irradiated onto the beef sample with the surface changes when the light emitted from the LED light source of a conventional device is irradiated onto the beef sample. [Modes for carrying out the invention]

[0010] When irradiating meat with light emitted from a lighting device, studies were conducted to suppress the discoloration of the meat while considering the color rendering properties of the light source for the meat, and the following findings were obtained.

[0011] With the advent of light-emitting diode (LED) light sources, the illumination of meat display cases has increased compared to the illumination of fluorescent lights used before. This is because the illumination of LED light sources installed in meat display cases has been increased, based on the understanding that consumers' desire to purchase meat increases when it appears more vivid.

[0012] However, while oxymyoglobin, the substance responsible for meat's vibrant red color, is relatively stable to light, the increasing intensity of LED light sources has led to concerns about meat discoloration caused by oxidation due to light exposure. As meat discoloration progresses, it can actually discourage consumers from buying meat. This, in turn, can contribute to an increase in meat waste.

[0013] Therefore, the present inventors have intensively studied the spectral distribution of the emitted light of the light source in order to suppress meat discoloration, and have arrived at one aspect of the present disclosure as follows.

[0014] That is, the first aspect of the present disclosure is a lighting device including a light source whose light irradiation target is meat, and the spectral distribution of the emitted light of the light source includes a first peak of the light intensity existing in a wavelength band of 430 nm or more and 470 nm or less, a second peak of the light intensity existing in a wavelength band of 490 nm or more and 540 nm or less, and a third peak of the light intensity existing in a wavelength band of 650 nm or more and 670 nm below and the half-value width of the third peak is 20 nm or less.

[0015] According to such a configuration, the lighting device of the present aspect can suppress meat discoloration more than conventionally when irradiating the meat with the emitted light of the light source.

[0016] Specifically, among the peaks of the light intensity of the above spectral distribution, by setting the light characteristics of the light source so that the half-value width of the third peak existing in the wavelength band of 650 nm or more and 670 nm below (red light) is 20 nm or less, the progress of meat discoloration caused by meat oxidation due to light irradiation can be reduced compared to the case where such light characteristics are not set. Details will be described in the first to third embodiments described later that verified the meat discoloration suppression effect.

[0017] The lighting device of the second aspect of the present disclosure is the lighting device of the first aspect, wherein the spectral distribution is determined so that a discoloration index that changes depending on the illuminance of the light source is less than a predetermined value, and the discoloration index may be derived based on an arithmetic expression in which the light intensity corresponding to a predetermined wavelength is an independent variable.

[0018] According to such a configuration, the lighting device of the present aspect can quantitatively predict the degree of progress of meat discoloration caused by meat oxidation due to light irradiation based on the arithmetic expression for deriving the discoloration index. A specific example of the "arithmetic expression" of the present disclosure will be described in the first embodiment described later.

[0019] In the third aspect of the present disclosure, the lighting device is such that, in the lighting device of the first aspect, the first ratio obtained by dividing the light intensity corresponding to the second peak by the light intensity corresponding to the first peak is between 0.5 and 4.0, and the allowable range of the second ratio obtained by dividing the light intensity corresponding to the third peak by the light intensity corresponding to the first peak can be derived based on a regression equation in which the first ratio is the independent variable.

[0020] With this configuration, the lighting device of this embodiment can appropriately maintain the color rendering of the light source to meat compared to when such light characteristics are not set, by setting the optical characteristics of the light source so that the light intensities of the first peak, second peak, and third peak in the spectral distribution are within the above-mentioned allowable range. Details will be explained in the fourth embodiment described later, in which the color rendering of the light source to meat is confirmed. Furthermore, a specific example of the "regression equation" of this disclosure will be explained in the fourth embodiment.

[0021] A lighting device according to a fourth aspect of this disclosure may include, in any one of the lighting devices according to the first to third aspects, a light source of the lighting device comprising a first light source that emits blue light, a second light source that emits green light, and a third light source that emits red light.

[0022] With this configuration, the lighting device of this embodiment includes a first light source that emits blue light, a second light source that emits green light, and a third light source that emits red light, thereby allowing the optical characteristics of the light source to be appropriately set so that the spectral distribution shows the first peak, second peak, and third peak.

[0023] A fifth aspect of the present disclosure is a lighting device in the fourth aspect, wherein the first light source comprises a blue light-emitting element, and the second and third light sources each comprise a blue light-emitting element and a phosphor that absorbs light energy from the blue light-emitting element and converts it into light of a predetermined wavelength.

[0024] A sixth aspect of the present disclosure is a lighting device in any one of the first to third aspects, in which the light source of the lighting device may include a red light source that emits red light and a white light source in which a white light-emitting element is covered with a wavelength cut filter.

[0025] With this configuration, the lighting device of this embodiment includes a red light source and a white light source in which a white light-emitting element is covered with a wavelength cut filter, thereby allowing the optical characteristics of the light source to be appropriately set so that the spectral distribution shows the first peak, second peak, and third peak.

[0026] The embodiments of this disclosure will be described below with reference to the attached drawings. The embodiments described below are specific examples of each of the above embodiments. Therefore, the numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are merely examples and do not limit the above embodiments. In addition, components in the following embodiments that are not described in the independent claims representing the highest-level concepts of this disclosure will be described as optional components. Also, in the drawings, components with the same reference numerals may not be described. Furthermore, the drawings are schematic representations of each component for ease of understanding, and the shapes and dimensional ratios may not be accurately represented.

[0027] (First Embodiment) [Configuration of Lighting Device A] Figure 1 is a plan view of an example of a lighting device according to the first embodiment.

[0028] In Figure 1, for convenience, the left-right direction of lighting device A is shown as in the figure. In the following explanation, this left-right direction will be referred to as the horizontal direction, and within the plane of Figure 1, the direction perpendicular to this horizontal direction will be referred to as the vertical direction (the same applies to Figure 2).

[0029] The lighting device A of this embodiment includes a light source 10 whose target for light irradiation is meat such as beef, pork, or chicken (for example, processed meat). In the example shown in Figure 1, the lighting device A includes a blue light source 11 that emits blue light, a red light source 12A that emits red light, and a green light source 13 that emits green light. The outer casings of the blue light source 11, the red light source 12A, and the green light source 13 are each made up of light-transmitting rod-shaped cylinders with an outer diameter of about 20 mm and a length in the left-right direction of about 150 mm. Inside each of these cylinders, a plurality of light-emitting elements (for example, LEDs) are arranged linearly at predetermined intervals in the left-right direction of the cylinder. In a plan view of the lighting device A, the vertical spacing between the cylinders is about 5 mm, and each cylinder is arranged so that its extension direction is horizontal. In Figure 1 (and Figure 2), for convenience, the outer casing structure of the cylinders is simply illustrated to show an example of the arrangement of light-emitting elements inside the cylinders.

[0030] In the blue light source 11, twelve blue LEDs 11B, which are an example of blue light-emitting elements, are arranged at regular intervals within a cylindrical body. These blue LEDs 11B have optical characteristics such that the light intensity of the spectral distribution of the emitted light shows a peak at a wavelength of approximately 445 nm. Such a blue light source 11 can be constructed using, for example, a product (C219) manufactured by Iida Lighting Co., Ltd., but is not limited to this.

[0031] In the red light source 12A, 16 red LEDs 12AR, which are an example of red light-emitting elements, are arranged within a cylindrical body at regular intervals. The distance between adjacent red LEDs 12AR is shorter than the distance between adjacent blue LEDs 11B. These red LEDs 12AR have optical characteristics such that the light intensity of the spectral distribution of the emitted light shows a peak at a wavelength of approximately 660 nm. The red LEDs 12AR can be obtained by coating a blue LED with an appropriate phosphor. Such a red light source 12A can be constructed using, for example, a product (660-4) manufactured by Iida Lighting Co., Ltd., but is not limited to this.

[0032] In the green light source 13, twelve green LEDs 13G, which are an example of green light-emitting elements, are arranged within a cylindrical body at regular intervals. The distance between adjacent green LEDs 13G is approximately the same as the distance between adjacent blue LEDs 11B. These green LEDs 13G have optical characteristics such that the light intensity of the spectral distribution of the emitted light shows a peak at a wavelength of approximately 530 nm. The green LEDs 13G can be obtained by coating a blue LED with an appropriate phosphor. Such a green light source 13 can be constructed using, for example, a product (G119) manufactured by Iida Lighting Co., Ltd., but is not limited to this.

[0033] [Configuration of the comparative lighting device (hereinafter referred to as the comparative device)] Figure 2 is a plan view of the comparison device.

[0034] The comparative device includes a light source 100 whose target for light irradiation is meat such as beef, pork, or chicken. In the example shown in Figure 2, this lighting device includes a blue light source 11 that emits blue light, a red light source 12B that emits red light, and a green light source 13 that emits green light. The blue light source 11 and the green light source 13 are the same as those in lighting device A, so a detailed explanation is omitted.

[0035] In the red light source 12B, twelve red LEDs 12BR, which are an example of red light-emitting elements, are arranged within a cylindrical body at regular intervals. The distance between adjacent red LEDs 12BR is approximately the same as the distance between adjacent blue LEDs 11B and adjacent green LEDs 13G. These red LEDs 12BR have optical characteristics such that the light intensity of the spectral distribution of the emitted light shows a peak at a wavelength of approximately 630 nm. The red LEDs 12BR can be obtained by coating a blue LED with an appropriate phosphor. Such a red light source 12B can be constructed using, for example, a product (R119) manufactured by Iida Lighting Co., Ltd., but is not limited to this.

[0036] [Configuration of a conventional lighting device (hereinafter referred to as "conventional device")] The conventional device used a commercially available LED light source for fresh food. Specifically, the LED light source consisted of BeeLIGHT's LED bulb "BH-2026H2Ra94," which has characteristics equivalent to a 150W reflector lamp, with a color temperature of 2800K and a flux density of 1360lm.

[0037] [Spectral characteristics of lighting device A] Figure 3 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device of the first embodiment, compared with the spectral distribution of the light emitted from the light source of a conventional device.

[0038] Figure 4 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device of the first embodiment, compared with the spectral distribution of the light emitted from the light sources of the conventional device and the comparative device.

[0039] In Figures 3 and 4, the spectral distribution of light was measured using a spectrophotometer (C-7000) manufactured by Sekonic Corporation. The photometric distance was set to the same distance as the light irradiation distance to the meat sample. In Figures 3 and 4, the horizontal axis represents the wavelength of light (nm), and the vertical axis represents the light intensity (W·m). -2 ·nm -1 ) has been taken.

[0040] As shown in Figures 3 and 4, the spectral distribution of the light emitted from the light source 10 of the lighting device A is as follows: a first peak P1 of light intensity in the wavelength band between 430 nm and 470 nm, a second peak P2 of light intensity in the wavelength band between 490 nm and 540 nm, and a peak between 650 nm and 670 nm below The device comprises a third peak P3 of light intensity present in the wavelength band, and the full width at half maximum (FWH) of the third peak P3 is 20 nm or less. The lower limit of the FWHH of the third peak P3 is not particularly limited, but may be, for example, around 10 nm. In other words, unless an appropriate wavelength cut filter is provided, it is difficult to make the FWHH of the third peak P3 less than 10 nm, so it is preferable that the FWHH of the third peak P3 is 10 nm or more and 20 nm or less.

[0041] In contrast, as shown in Figure 3, in the spectral distribution of the emitted light from the LED light source of the conventional device, the light intensity in the wavelength band from 490 nm to 540 nm increases monotonically, so there is no peak in light intensity in the wavelength band from 490 nm to 540 nm. Furthermore, while there is a peak in light intensity in the wavelength band of approximately 630 nm, the light intensity in the wavelength band above approximately 630 nm decreases monotonically, so there is no peak in light intensity in the wavelength band from 650 nm to 670 nm. below There is no peak in light intensity in this wavelength band. Furthermore, the full width at half maximum of the light intensity peak at approximately 630 nm is greater than 20 nm.

[0042] As shown in Figure 4, the spectral distribution of the light emitted from the light source 100 of the comparison device is similar to the spectral distribution of the light emitted from the light source 10 of the illumination device A, with peaks in light intensity in the wavelength band from 430 nm to 470 nm and peaks in light intensity in the wavelength band from 490 nm to 540 nm. However, while there is a peak in light intensity in the wavelength band of approximately 630 nm, the light intensity in the wavelength band above approximately 630 nm decreases monotonically, therefore, from 650 nm to 670 nm... below There is no peak in light intensity in this wavelength band.

[0043] [First Example (Evaluation of meat discoloration by light irradiation from a lighting device)] <Method for deriving the fading index D> To quantitatively predict the degree of meat discoloration caused by light irradiation from lighting device A, the discoloration index D of the lighting device was derived through the following experiment.

[0044] The experiment used horse-derived myoglobin (manufactured by SERVA Electrophoresis, purchased from Fujifilm Wako Pure Chemical Industries). An appropriate amount of this horse-derived myoglobin was dissolved in distilled water, then reduced with sodium hydrosulfite, and the sodium hydrosulfite was removed using a desalting column. The myoglobin solution from which the sodium hydrosulfite had been removed was further diluted to a concentration of 1 mg / mL. The resulting myoglobin solution was 70% to 90% divalent myoglobin. Divalent myoglobin exists as oxymyoglobin in the atmosphere.

[0045] In the experiment, the oxidation rate of oxymyoglobin was evaluated under the illumination of light at various wavelengths or in darkness. The wavelengths of light irradiated onto the myoglobin solution were 450 nm, 580 nm, 600 nm, 615 nm, 630 nm, and 645 nm. Approximately 850 μm of myoglobin solution was dispensed into a semi-microcell, and the above wavelengths of light were irradiated using a fluorescence spectrophotometer FP-6500 (Jasco). The bandwidth of the light irradiated onto the myoglobin solution was set to approximately 10 nm. The degree of oxidation of myoglobin can be determined from the metmyoglobin ratio (MetMb(%)) calculated using the following formula (1) disclosed in the paper (Krzywicki (1982) The determination of haem pigments in meat. Meat Science, 7(1), 29-36.). MetMb(%)=100×(1.395-A572÷A525)...(1) In equation (1), "A572" refers to the absorbance of light with a wavelength of 572 nm, and "A525" refers to the absorbance of light with a wavelength of 525 nm.

[0046] Here, the time rate of change of the degree of oxidation of myoglobin obtained from equation (1) is calculated as the oxidation rate of myoglobin, and in this disclosure, the ratio of the oxidation rate of myoglobin under light irradiation to the oxidation rate of myoglobin under darkness is defined as the "degree of oxidation promotion" of myoglobin by light of each wavelength mentioned above. Then, the results in Table 1 below were obtained.

[0047] [Table 1]

[0048] Table 1 shows that the degree of oxidation of myoglobin by light with wavelengths above 615 nm is lower than that of light with wavelengths between 450 nm and 600 nm. Furthermore, the degree of oxidation of myoglobin by light at 645 nm is lower than that of light with wavelengths between 615 nm and 630 nm.

[0049] Therefore, in this disclosure, the fading index D of a lighting device, used to quantitatively predict the degree of meat fading caused by oxidation due to light irradiation by the lighting device, is defined as the sum of the values ​​obtained by multiplying the "degree of oxidation promotion" in Table 1 by the light intensity (light energy) obtained from the spectral distribution of the emitted light of the light source. In other words, the fading index D of the lighting device is derived based on the following equation (2), in which the light intensity W present at a predetermined wavelength is the independent variable. Such equation (2) is an example of the "calculation formula" in this disclosure. However, in evaluating fading suppression using the fading index D for each lighting device, the above light intensity changes depending on the illuminance of the lighting device, so it is necessary to keep the illuminance of each lighting device constant.

[0050]

number

[0051] In equation (2), "W (wavelength)" is the light intensity (W·m) corresponding to the wavelength (nm) in parentheses. -2 ·nm -1 ) and can be determined from the spectral distribution of light. The fading index D described above is illustrative and not limited to this example. For example, the selection of irradiation wavelengths in Table 1 is not necessarily limited to the wavelengths disclosed in Table 1.

[0052] <Evaluation results of lighting equipment based on fading index D> Using equation (2), the fading index D was calculated when the illuminance (Lux) of the emitted light from the light source 10 of lighting device A, the light source 100 of the comparison device, and the LED light source of the conventional device was 10,000, and the result was as follows. ·Lighting device A: Fading index D=0.98 Comparison device: Fading index D=1.91 • Conventional device: Fading index D = 2.60 From this, it can be seen that lighting device A, the comparative device, and the conventional device have small fading index D in this order (fading index D of lighting device A (=0.98) < fading index D of comparative device (=1.91) < fading index D of conventional device (=2.60)), so lighting device A can suppress meat fading more effectively than the comparative device and the conventional device. For example, if the fading index D of the light emitted by lighting device A is less than a predetermined value when the illuminance (Lux) is 10000, it is considered that the effect of suppressing meat fading by the emitted light can be appropriately exerted. The "predetermined value" can be, for example, about 1.9, but is not limited to this.

[0053] [Second Example (Evaluation of Meat Color under Light Irradiation by Lighting Device A)] In the second embodiment, the following meat samples (beef and pork samples) were used, and the color tone of the meat samples under light irradiation from the LED light source 10 of lighting device A was evaluated in comparison to the color tone of the meat samples under light irradiation from a conventional device. <Meat sample> • Beef sample: The outer thigh meat was uniformly processed into a mince of approximately 3 mm in size, and the resulting chunks were placed in appropriate containers and then placed in a display case maintained at approximately 4°C. • Pork sample: Pork shoulder was uniformly minced to a size of approximately 3 mm, and the resulting chunks were placed in appropriate containers and then placed in a display case maintained at approximately 4°C. <Analyzer> A spectrophotometer (CM-5) manufactured by Konica Minolta Japan, Inc. was used as the analytical device for measuring the color tone of meat samples. A D65 light source was used as the observation light source, the measurement window was 8 mm, and the field of view for total internal reflection measurement was 10°. <Evaluation Method> The color of meat under light irradiation was evaluated by measuring the redness (a*) and color difference (ΔE*) five times each after a predetermined period had elapsed since the start of storage of the meat sample. The average value of these measurement data was then processed appropriately. The predetermined period was 3 days (2 days in between) for beef samples and 1 day (the following day) for pork samples. A higher redness (a*) indicates a redder meat sample, and a higher color difference (ΔE*) indicates a greater color difference in the meat sample. <Evaluation Results> Beef sample When a beef sample was irradiated with light using illumination device A, the color difference (ΔE*) was found to be reduced by approximately 38.6% compared to when the beef sample was irradiated with light using a conventional device. Furthermore, when the beef sample was irradiated with light using illumination device A, the redness (a*) of the beef sample was improved by approximately 30% compared to when the beef sample was irradiated with light using a conventional device. These evaluation results confirm, through color evaluation of the beef sample, that irradiating a beef sample with light using illumination device A can suppress the progression of discoloration of the beef sample compared to when the beef sample was irradiated with light using a conventional device. • Pork sample When pork samples were irradiated with lighting device A, the color difference (ΔE*) was found to be reduced by approximately 23.4% compared to when pork samples were irradiated with conventional equipment. Furthermore, when beef samples were irradiated with lighting device A, the redness (a*) of the beef samples was improved by approximately 13% compared to when beef samples were irradiated with conventional equipment. These evaluation results confirm, through color evaluation of pork samples, that irradiating pork samples with lighting device A can suppress the progression of discoloration compared to irradiating pork samples with conventional equipment.

[0054] [Third Example (Evaluation of Meat Color under Light Irradiation of the Comparative Device)] In the third embodiment, the same beef sample as described above was used, and the color tone of the beef sample under light irradiation from the light source 100 of the comparison device was evaluated in comparison with the color tone of the beef sample under light irradiation from the conventional device. The analytical device and evaluation method are the same as described above, so their explanation is omitted. <Evaluation Results> When a beef sample was irradiated with light using the comparative device, the color difference (ΔE*) was reduced by only about 4.3% compared to when the beef sample was irradiated with light using the conventional device. Furthermore, when the beef sample was irradiated with light using the comparative device, the redness (a*) of the beef sample was improved by only about 0.4% compared to when the beef sample was irradiated with light using the conventional device. From these evaluation results, it was possible to verify through the color evaluation of the beef sample that irradiating the beef sample with light using the comparative device does not improve the progression of discoloration of the beef sample at all compared to when the beef sample was irradiated with light using the conventional device. In other words, from these evaluation results, it was found that to suppress the progression of discoloration of the beef sample, the spectral distribution of the emitted light above 650 nm and above 670 nm is important. below It was found that a peak in light intensity (third peak P3) exists in this wavelength band, and that it is necessary to set the full width at half maximum (FWH) of this third peak P3 to a desired value.

[0055] [Fourth embodiment (Color rendering of light source 10 of lighting device A)] In the fourth embodiment, the acceptable range of the color (light color) of the light emitted by the light source 10 itself was derived as follows, from the viewpoint of maintaining the color rendering properties of the light source 10. <Evaluation Method> The ratio of the light intensity of the green light source 13 (530 nm; green light) to the light intensity of the blue light source 11 (445 nm; blue light) (hereinafter referred to as the first ratio) is changed in steps from "1 / 2", "2 / 3", "1", "3 / 2", "2", "3", and "4". In other words, the first ratio corresponds to the value obtained by dividing the light intensity corresponding to the second peak P2 by the light intensity corresponding to the first peak P1.

[0056] Then, when the first ratio was fixed to one of "1 / 2", "2 / 3", "1", "3 / 2", "2", "3", and "4", the light intensity of the red light source 12A (660nm; red light) was adjusted steplessly, and the light emitted from the light source 10 of the illumination device A was irradiated onto the same beef sample as above. At this time, consumers visually observed the irradiated beef sample and confirmed the ratio of the light intensity of the red light source 12A to the light intensity of the blue light source 11 (hereinafter referred to as the second ratio) that could maintain the willingness to purchase the beef sample. In other words, the second ratio corresponds to the value obtained by dividing the light intensity corresponding to the third peak P3 by the light intensity corresponding to the first peak P1.

[0057] The smaller the second ratio, the less red component is in the light emitted from the light source 10 of lighting device A, which may result in the beef sample not looking like meat. The timing at which the second ratio reached this state was defined as the lower limit of the light intensity of the red light source 12A.

[0058] The larger the second ratio, the greater the red component of the light emitted from the light source 10 of lighting device A, which may result in the beef sample not being clearly visible. The point at which the second ratio reached this state was set as the upper limit of the light intensity of the red light source 12A.

[0059] Three experiments were conducted to confirm the upper and lower limits of the second ratio described above, and the average value of these experimental data was calculated. Light intensity was adjusted using a spectrophotometer (C-7000) manufactured by Sekonic Corporation. <Evaluation Results> Figure 5 shows the results of the color rendering evaluation of the light source of the lighting device in the fourth embodiment of the first embodiment. The horizontal axis of Figure 5 is plotted as the first ratio x, and the vertical axis is plotted as the second ratio y. In Figure 5, the second ratio y corresponding to the upper and lower limits of the light intensity of the red light source 12A is plotted when the first ratio x is fixed to one of "1 / 2", "2 / 3", "1", "3 / 2", "2", "3", and "4".

[0060] Regression analysis was performed on the plotted data in Figure 5, and the results are shown in Figure 5 as the line L1 of regression equation (3) below, which represents the upper limit of the second proportion y, and the line L2 of regression equation (4) below, which represents the lower limit of the second proportion y. Regression equations (3) and (4) are examples of "regression equations" in this disclosure. • Upper limit of the second ratio y: y = 5.6069x - 0.0873 ... (3) • Lower limit of the second ratio y: y = 1.9869x - 0.5747 ... (4) In equation (3), "5.6069" and "-0.0873" are regression coefficients. "5.6069" is the slope that shows the relationship between the first proportion x and the second proportion y, and "-0.0873" is the value of the second proportion y when the first proportion x is zero.

[0061] In equation (4), "1.9869" and "-0.5747" are regression coefficients. "1.9869" is the slope that shows the relationship between the first proportion x and the second proportion y, and "-0.0873" is the value of the second proportion y when the first proportion x is zero.

[0062] Furthermore, as shown in the shaded area of ​​Figure 5, when the first ratio x is between 0.5 and 4.0, the allowable range TA of the second ratio y can be derived based on regression equations (3) and (4). Thus, the lighting device A of the fourth embodiment can appropriately maintain the color rendering of the light source 10 for beef compared to when such light characteristics are not set, by setting the optical characteristics of the light source 10 so that the light intensities of the first peak P1, the second peak P2, and the third peak P3 are within the allowable range TA.

[0063] (Second Embodiment) [Configuration of Lighting Device B] Figure 6 shows an example of a lighting device according to the second embodiment.

[0064] In Figure 6, the left-right direction of lighting device B is shown as shown in the figure. In the following explanation, this left-right direction will be referred to as the horizontal direction, and the direction perpendicular to this horizontal direction within the plane of Figure 6(a) will be referred to as the vertical direction.

[0065] Figure 6(a) shows a plan view of lighting device B, and Figure 6(b) shows a side view of the white light source 14 of lighting device B, viewed from the side. However, for convenience, the wavelength cut filters 20, 21, 22, 23, 24, 30, 31, and 32 of the white light source 14 are omitted from Figure 6(a).

[0066] The lighting device B of this embodiment includes a light source 50 whose target for light irradiation is meat such as beef, pork, or chicken. In the example shown in Figure 6, the lighting device B includes a light source 10 which comprises a red light source 12A that emits red light and a white light source 14 in which a white LED, which is an example of a white light-emitting element, is covered with multiple wavelength cut filters 20, 21, 22, 23, 24, 30, 31, and 32. The red light source 12A of lighting device B is the same as the red light source 12A of lighting device A, so a detailed explanation is omitted.

[0067] The white light source 14 comprises multiple white LED chips 14W, each approximately 5mm x 2.5mm in size, arranged at equal intervals in the left-right direction on a substrate of approximately 10mm x 300mm. In the example shown in Figure 6, 12 white LED chips 14W are arranged on the substrate, and the white LED chips 14W are numbered sequentially from the left edge of the substrate, as follows: white LED chip 14W(1), 14W(2), ... 14W(12). In a plan view of the lighting device B, the vertical distance between the red light source 12A and the white light source 14 is approximately 20mm, and both are arranged so that their extension direction is horizontal. Such a white light source 14 can be constructed using, for example, a white LED bar (5700K) manufactured by Riken Dengu Manufacturing Co., Ltd., but is not limited to this.

[0068] The white LED chip 14W(1) and the white LED chip 14W(2) are covered with a wavelength cut filter 20. The wavelength cut filter 20 can be constructed using, for example, a bandpass filter (cutoff wavelength: 580nm) manufactured by Riken Dengu Manufacturing Co., Ltd., but is not limited to this.

[0069] The white LED chip 14W(3) is covered with a wavelength cut filter 30. The wavelength cut filter 30 can be constructed using, for example, a suitable yellow film (cutoff wavelength: 450nm), but is not limited to this.

[0070] The white LED chip 14W(4) is covered with a wavelength cut filter 21. The optical characteristics of the wavelength cut filter 21 are the same as those of the wavelength cut filter 20, so a description is omitted.

[0071] The white LED chips 14W(5) and 14W(8) are covered with a wavelength cut filter 31. The optical characteristics of the wavelength cut filter 31 are the same as those of the wavelength cut filter 30, so a detailed explanation is omitted.

[0072] White LED chips 14W(6) and 14W(7) are covered by wavelength cut filter 22 and the wavelength cut filter 31 described above. The optical characteristics of wavelength cut filter 22 are the same as those of wavelength cut filter 20, so a description is omitted.

[0073] The white LED chip 14W(9) is covered with a wavelength cut filter 23. The optical characteristics of the wavelength cut filter 23 are the same as those of the wavelength cut filter 20, so a description is omitted.

[0074] The 14W (10) white LED chip is covered with a wavelength cut filter 32. The optical characteristics of the wavelength cut filter 32 are the same as those of the wavelength cut filter 30, so a detailed explanation is omitted.

[0075] The white LED chip 14W(11) and the white LED chip 14W(12) are covered with a wavelength cut filter 24. The optical characteristics of the wavelength cut filter 24 are the same as those of the wavelength cut filter 20, so a description is omitted.

[0076] [Conventional device configuration] The configuration of the conventional device is the same as that of the first embodiment, so a description will be omitted.

[0077] [Spectral characteristics of illumination device B] Figure 7 shows an example of the spectral distribution (light spectrum) of the light emitted from the light source of the lighting device in the second embodiment, compared with the spectral distribution of the light emitted from the light source of a conventional device.

[0078] In Figure 7, the spectral distribution of light was measured using a spectrophotometer (C-7000) manufactured by Sekonic Corporation. The photometric distance was set to the same distance as the light irradiation distance to the meat sample. The horizontal axis of Figure 7 represents the wavelength of light (nm), and the vertical axis represents the light intensity (W·m). -2 ·nm -1 ) has been taken.

[0079] As shown in Figure 7, the spectral distribution of the light emitted from the light source 50 of lighting device B is as follows: a first peak P1 of light intensity in the wavelength band between 430 nm and 470 nm, a second peak P2 of light intensity in the wavelength band between 490 nm and 540 nm, and a peak between 650 nm and 670 nm. below The device comprises a third peak P3 of light intensity present in the wavelength band, and the full width at half maximum (FWH) of the third peak P3 is 20 nm or less. The lower limit of the FWHH of the third peak P3 is not particularly limited, but may be, for example, around 10 nm. In other words, unless an appropriate wavelength cut filter is provided, it is difficult to make the FWHH of the third peak P3 less than 10 nm, so it is preferable that the FWHH of the third peak P3 is 10 nm or more and 20 nm or less.

[0080] In contrast, as shown in Figure 7, in the spectral distribution of the emitted light from the LED light source of the conventional device, the light intensity in the wavelength band from 490 nm to 540 nm increases monotonically, so there is no peak in light intensity in the wavelength band from 490 nm to 540 nm. Furthermore, while there is a peak in light intensity in the wavelength band of approximately 630 nm, the light intensity in the wavelength band above approximately 630 nm decreases monotonically, so there is no peak in light intensity in the wavelength band from 650 nm to 670 nm. belowThere is no peak in light intensity in this wavelength band. Furthermore, the full width at half maximum of the light intensity peak at approximately 630 nm is greater than 20 nm.

[0081] [Example (Evaluation of meat discoloration by light irradiation with lighting device B)] <Evaluation of lighting device B using fading index D> The method for deriving the fading index D in the embodiment is the same as in the first embodiment, so the explanation will be omitted.

[0082] Using the above equation (2), the fading index D when the illuminance (Lux) of the emitted light from the light source 50 of lighting device B and the LED light source of the conventional device is 10,000 was calculated as follows. ·Lighting device B: Fading index D=1.79 • Conventional device: Fading index D = 2.60 From this, it follows that lighting device B and the conventional device have smaller fading index D in this order (fading index D of lighting device B (=1.79) < fading index D of conventional device (=2.60)), so lighting device B can suppress meat fading compared to the conventional device. For example, if the illuminance (Lux) of the light emitted from the light source 50 of lighting device B is 10,000, and the fading index D is less than a predetermined value, it is considered that the effect of suppressing meat fading by the emitted light can be appropriately exerted. The "predetermined value" can be, for example, about 1.9, but is not limited to this. <Visual observation and evaluation of beef samples using light irradiation from lighting device B> Figure 8 is a grayscale photograph comparing the surface changes of a beef sample when irradiated with light emitted from the light source of the lighting device in the second embodiment with the case when irradiated with light emitted from the LED light source of a conventional device. In the embodiment, the grayscale photographs show the surface changes of a beef sample placed in a showcase maintained at approximately 4°C, taken at regular intervals (1 day in this case) from the start of storage of the beef sample to a predetermined period (4 days in this case). Color versions of these photographs were submitted separately in the submission form.

[0083] By referring to the color diagram attached to the property submission form, it is clear that when the light emitted from light source 50 of lighting device B is shone on the beef sample, the change in the red color of the beef sample is smaller compared to when the light emitted from the LED light source of the conventional device is shone on the beef sample. From this, it was possible to verify by visual observation that lighting device B can suppress meat discoloration compared to the conventional device.

[0084] Furthermore, a market survey was conducted targeting consumers who regularly purchase meat, asking them "If these were the same price, which would you buy?" regarding beef samples illuminated by the light emitted from the light source 50 of lighting device B (hereinafter referred to as the beef sample of this embodiment) and beef samples illuminated by the light emitted from the LED light source of the conventional device (hereinafter referred to as the beef sample of the conventional example).

[0085] As a result, on the first day of storage of the beef samples, two consumers selected the conventional beef sample, and four consumers selected the beef sample of this embodiment. In contrast, after four days from the start of storage of the beef samples, eight out of nine consumers selected the beef sample of this embodiment.

[0086] These market research findings indirectly support the conclusion that lighting device B is superior to conventional devices in both suppressing meat discoloration and maintaining color rendering.

[0087] From the above description, many improvements and other embodiments of the disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. The details of its structure and / or function can be substantially modified without departing from the spirit of the disclosure. [Industrial applicability]

[0088] One aspect of this disclosure can be used, for example, in a lighting device that can suppress meat discoloration more effectively than conventional devices when irradiating meat with light emitted from a light source. [Explanation of Symbols]

[0089] 10:Light source 11: Blue light source 11B: Blue LED 12A: Red light source 12AR: Red LED 12B: Red light source 12BR: Red LED 13: Green light source 13G: Green LED 14: White light source 14W: White LED equipped chip 20: Wavelength cut filter 21: Wavelength cut filter 22: Wavelength cut filter 23: Wavelength cut filter 24: Wavelength cut filter 30: Wavelength cut filter 31: Wavelength cut filter 32: Wavelength cut filter 50:Light source 100: Light source A:Lighting device B:Lighting device

Claims

1. A lighting device equipped with a light source whose target for light irradiation is meat, The spectral distribution of the light emitted from the aforementioned light source comprises a first peak of light intensity in the wavelength band between 430 nm and 470 nm, a second peak of light intensity in the wavelength band between 490 nm and 540 nm, and a third peak of light intensity in the wavelength band between 650 nm and 670 nm. The full width at half maximum of the third peak is 20 nm or less. A lighting device in which, assuming that the light intensity units W·m⁻²·nm⁻¹ corresponding to wavelengths of 450 nm, 580 nm, 600 nm, 615 nm, 630 nm, and 645 nm of the emitted light from the light source are W(450), W(580), W(600), W(615), W(630), and W(645), respectively, the spectral distribution is determined such that the fading index D, derived by the following formula, is less than 1.9 when the emitted light from the light source is 10,000 Lux. D = 2.16 x W (450) + 4.93 x W (580) + 2.94 x W (600) + 1.69 x W (615) + 1.24 x W (630) + 0.92 x W (645)

2. The first ratio obtained by dividing the light intensity corresponding to the second peak by the light intensity corresponding to the first peak is 0.5 or more and 4.0 or less. The lighting device according to claim 1, wherein the allowable range of the second ratio obtained by dividing the light intensity corresponding to the third peak by the light intensity corresponding to the first peak is derived based on a regression equation in which the first ratio is the independent variable.

3. The lighting device according to claim 1 or 2, wherein the light source comprises a first light source that emits blue light, a second light source that emits red light, and a third light source that emits green light.

4. The lighting device according to claim 3, wherein the first light source comprises a blue light-emitting element, and the second and third light sources each comprise a blue light-emitting element and a phosphor that absorbs light energy from the blue light-emitting element and converts it into light of a predetermined wavelength.

5. The lighting device according to claim 1 or 2, wherein the light source comprises a red light source that emits red light and a white light source in which a white light-emitting element is covered with a wavelength cut filter.

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