Organic EL Element and Lighting Device

Abstract

Provided is an organic EL element capable of emitting white light that is a white having a low color temperature and has a high color rendering index at a practical power efficiency.　The present invention comprises, in order from a light exit surface side, a translucent substrate, a translucent anode layer, a light-emitting functional layer, and a metal cathode layer. The light-emitting functional layer has a red / green light-emitting unit, a unit-connecting mechanism, and a blue light-emitting unit. The red / green light emitting unit comprises a mixed red / green phosphorescent light-emitting layer comprising a green phosphorescent light-emitting material, a red phosphorescent light-emitting material, and a phosphorescent light-emitting layer host material. The blue light-emitting unit comprises a blue fluorescent light-emitting layer and a HTL adjusting layer that is adjacent to the blue fluorescent light-emitting layer, and on the side having the unit connecting mechanism, has an average thickness of at least 50 nm. The present invention is configured so as to be able to emit white light from the light exit surface, said white light having a correlated color temperature TCP of 2200-3000K, a distance from the black body curve duv of at most 0.02, a color rendering index Ra of at least 80, and a melanopic ratio value of at most 0.65.

Description

Technical Field

[0001] The present invention relates to an organic EL element and a lighting device in which the organic EL element is mounted, and particularly to an organic EL element that emits a specific white light.

Background Art

[0002] An organic EL element is a semiconductor element that converts electrical energy into light energy. An organic EL device including this element has attracted attention as a light source that replaces an incandescent lamp or a fluorescent lamp and emits soft diffused light thinly and in a planar shape, and many studies have been conducted in recent years.

[0003] For example, a bottom emission type organic EL element generally has a transparent anode layer, a functional layer including at least a light emitting layer containing an organic compound, and a metal cathode layer laminated in this order on a glass substrate or a translucent resin film substrate serving as a base material. In the organic EL element, electrons and holes electrically excited by power supply between these electrodes recombine in the light emitting layer to emit light.

[0004] Toward the practical application of such an organic EL element, further improvements in efficiency, luminance, color rendering property, and furthermore, biological action effects have been demanded in recent years.

[0005] For example, Patent Document 1 discloses a light source module capable of achieving both a biological action effect of adjusting the circadian rhythm, which is an internal clock that completes one cycle in a 24-hour period, and good skin appearance. The light source module of Patent Document 1 includes a solid light emitting element and a wavelength conversion unit. The biological action degree (DIN) indicating the melatonin secretion inhibitory effect, which is calculated from the spectral distribution of the combined light emitted from the wavelength conversion unit, is at least 0.85, the correlated color temperature TCP of the combined light is 5000K or more and less than 7100K, and the preference index of skin color (PS), which is calculated from the spectral distribution of the combined light, is at least 60. Specifically, Patent Document 1 discloses a white light source capable of irradiating white light having a spectral distribution of the synthesized light with a first peak wavelength in the range of 400 nm to 470 nm, a second peak wavelength in the range of 471 nm to 550 nm, and a third peak wavelength in the range of 551 nm to 670 nm, an interval between the second peak wavelength and the third peak wavelength being in the range of 80 nm to 120 nm, an average color rendering evaluation number Ra conforming to JIS Z 8726 being 85, and a skin color preference index being 80.

[0006] Also, for example, Patent Document 2 discloses a light source module capable of achieving both a biological action effect of adjusting the circadian rhythm and good skin appearance. The light source module of Patent Document 2 includes a first light emitting device 1, a second light emitting device 2, and a third light emitting device 3 having different emission spectra from each other. The light source module of Patent Document 2 is calculated from the spectral distribution of the first synthesized light in which the light emitted from the first light emitting device 1 and the light emitted from the second light emitting device 2 are synthesized, and the biological action degree (DIN) showing a melatonin secretion inhibitory effect is 0.85 or more, the correlated color temperature TCP of the first synthesized light is 5000 K or more and 7100 K or less, the skin color preference index (PS) calculated from the spectral distribution of the first synthesized light is 60 or more, the DIN calculated from the spectral distribution of the second synthesized light in which the light emitted from the second light emitting device 2 and the light emitted from the third light emitting device 3 are synthesized is 0.25 or less, and the correlated color temperature TCP of the second synthesized light is 2000 K or more and 3250 K or less.

[0007] Specifically, Patent Document 2 discloses that the correlation temperature of the synthesized light is 2000K or more and less than 3250K, the spectral distribution of the synthesized light has a peak wavelength in the range of 400nm to 470nm, has a second peak in the range of 550nm to 670nm, uses a yellow phosphor having a peak wavelength in the range of 550nm to 600nm, and uses a red phosphor having a peak wavelength in the range of 630nm to 670nm for a light-emitting diode. And Patent Document 2 discloses that the average color rendering evaluation number Ra conforming to JIS Z 8726 is 80, it is a white light source of 2000K or more and less than 7100K, and alternately arranges a low color temperature TCP first light source (blue-red two-wavelength light source) and a high color temperature TCP second light source (blue-green two-wavelength light source), and lights a predetermined light source according to time. However, the light source module of Patent Document 2 has a problem that glare is likely to occur by switching between the first light source and the second light source.

[0008] Furthermore, as described in Non-Patent Document 1, it was reported by Brainard et al. in 2001 that the suppression of human melatonin secretion is affected by the blue light emission spectrum on the short wavelength side even at high illuminance or minimum illuminance, and also depends on the spectrum in the 460nm region on the slightly longer wavelength side. Subsequently, it was reported by Thapan et al. that it is related to intrinsically photosensitive retinal ganglion cells (ipRGC) containing a substance called melanopsin. In addition, Time Physiology Vol.14.No1 (2008) also describes the relationship between the blue region spectrum and human melatonin secretion suppression.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] Regarding the melatonin secretion related to the prior art described above, since the active time zone suppresses human melatonin secretion, high color temperature TCP lighting that enhances the blue light emission region is used. Also, humans produce melatonin that promotes sleep and go to bed when melatonin reaches its maximum secretion. When humans perceive light from their eyes, the secretion of melatonin is suppressed, and the secretion of melatonin is particularly affected by the spectral spectrum of the blue light emission region. From this, it is considered necessary to avoid suppressing melatonin secretion by using low color temperature TCP lighting with the blue light emission region cut as much as possible for night lighting.

[0011] In view of the above, an object of the present invention is to provide an organic EL element that emits white light with a lower color temperature than conventional ones and has high color rendering properties with practical power efficiency. Another object of the present invention is to provide a lighting device that can be fixed to the object to be visually recognized and can illuminate the object to be visually recognized with the organic EL panel in a desired posture.

Means for Solving the Problems

[0012] Regarding the above problems of the present invention, the inventor noted the Melanopic Ratio value as an index of the degree of stimulation to the retinal nerve cells of the eye because the production of melatonin in the body is derived from the stimulation to the retinal nerve cells of the eye. When introducing sleep, a measure was tried to reduce the intensity of the blue light emission spectrum in order to reduce the light in the blue region that acts to suppress melatonin production. However, when the intensity of the blue emission spectrum is reduced, in order to improve the power efficiency, it is necessary to enhance the green and red emission spectra, which results in a problem of a decrease in the average color rendering index Ra. On the other hand, when trying to adjust the average color rendering index Ra in the higher direction, it is necessary to weaken the intensities of the green and red emission spectra, which leads to a reduction in the intensity of the highly visible green emission, and the power efficiency is also likely to decrease.

[0013] Here, the Melanopic Ratio value is calculated by the Melanopic Ratio method. The Melanopic Ratio method is a simulation method, Tool Box, published by The WELL Building Standard (WELL).

[0014] Also, regarding the Melanopic Ratio value, it is necessary to weaken the blue emission intensity of the white light source.

[0015] The present invention relates to the balance of such low color temperature TCP, and specifically proposes a solution to the problem that the lack of light in the blue region causes defects in characteristics such as color rendering and Melanopic Ratio value.

[0016] Generally, the thinner the thickness of the blue emission layer and the lower the content of the blue emission material, the lower the blue emission intensity tends to be. However, in the conventional structure, as shown in FIG. 7, even when the fluorescent blue emission layer is designed to be 3 nm and the blue emission material is 1 wt%, the blue emission intensity is higher than expected, the color temperature TCP is below 3000K, but the Melanopic Ratio value is 0.632. Therefore, it is necessary to perform a new device design.

[0017] As a means to solve such various problems, the present invention aims to improve the efficiency, for example, by sufficiently separating the green and red phosphorescent units from the reflective cathode side so as to be less affected by plasmon loss. Also proposed is an organic EL device that emits white light, in which the hole transport layer on the blue unit side is an adjustment layer so as to weaken the blue light emission intensity and enable a distance duv from the blackbody radiation curve to be 0.02 or less.

[0018] One aspect of the present invention is an organic EL device having a light emitting surface and a back surface as both main surfaces, including a transparent substrate, a transparent anode layer, a light emitting functional layer, and a metal cathode layer in this order from the light emitting surface side, the light emitting functional layer having a hole transporting surface and an electron transporting surface as both surfaces, and having a green / red light emitting unit, a unit connection mechanism, and a blue light emitting unit, the unit connection mechanism being a mechanism that injects electrons to the green / red light emitting unit side and injects holes to the blue light emitting unit side when energized, the green / red light emitting unit having a hole transporting surface and an electron transporting surface as both surfaces, and including a green / red phosphorescent mixed light emitting layer containing a green phosphorescent material, a red phosphorescent material, and a phosphorescent light emitting layer host material, and emitting green light and red light when energized, the blue light emitting unit having a hole transporting surface and an electron transporting surface as both surfaces, and including a blue fluorescent light emitting layer that emits blue light when energized, and, adjacent to the blue fluorescent light emitting layer and on the unit connection mechanism side, an HTL adjustment layer as a hole transporting layer with an average thickness of 50 nm or more, and being capable of emitting white light having a correlated color temperature TCP of 2200K to 3000K, a distance duv from the blackbody radiation curve of the coordinate position in the CIE1931 chromaticity coordinate system of 0.02 or less, a color rendering index Ra of 80 or more, and a Melanopic Ratio value of 0.65 or less from the light emitting surface. That is, the present invention is an organic EL element having a light-emitting surface and a back surface as both main surfaces, and from the light-emitting surface, the correlated color temperature TCP is 2200K to 3000K, the distance duv from the blackbody radiation curve of the coordinate position in the CIE1931 chromaticity coordinate system is 0.02 or less, and the color rendering index Ra regarding color reproducibility is 80 or more, and emits white light with a Melanopic Ratio value, which is an index of the degree of stimulation to the retinal nerve cells of the eye, of 0.65 or less. From the light-emitting surface side in order, it includes a translucent substrate, a translucent anode layer, a light-emitting functional layer of a green / red light-emitting unit and a blue light-emitting unit having a hole-transporting surface and an electron-transporting surface as both surfaces and a unit connection mechanism, and a metal cathode layer. The unit connection mechanism is a mechanism that injects electrons into the green / red light-emitting unit side and injects holes into the blue light-emitting unit side when the organic EL element is energized. The green / red light-emitting unit has a hole-transporting surface and an electron-transporting surface as both surfaces and emits green light and red light. The blue light-emitting unit has a hole-transporting surface and an electron-transporting surface as both surfaces and includes a blue fluorescent light-emitting layer that emits blue light. Further, the green / red light-emitting unit includes a green / red phosphorescent mixed light-emitting layer including a green phosphorescent material, a red phosphorescent material, and a phosphorescent light-emitting layer host material. Furthermore, the blue light-emitting unit includes an HTL adjustment layer as a hole-transporting layer with an average thickness of 50 nm or more adjacent to the blue fluorescent light-emitting layer and on the unit connection mechanism side. It relates to an organic EL element.

[0019] The "correlated color temperature" referred to here means the correlated color temperature according to JIS Z 8725:2015. The "Melanopic Ratio value" can be obtained by the following formula (1).

[0020]

Equation

[0021] Here, Lamp represents the spectral distribution of the organic EL element, Circadian represents the sensitivity curve (absorbance) of ipRGC, which is a photoreceptor in the retina of mammals, and Visual represents the visual sensitivity curve in human photopic vision. Also, Lamp×Circadian represents the circadian response included in the spectral distribution of the organic EL element, and Lamp×Visual represents the visual sensitivity response included in the spectral distribution of the organic EL element.

[0022] According to this aspect, since white light with low blue emission intensity and high color rendering property is emitted, the load for visual recognition of objects including color tones is reduced, it is gentle to the eyes in the living environment at night, can contribute to improving the quality of sleep, and is suitable as wellness lighting.

[0023] Generally, when the amount of blue light emission is reduced, the emission balance is disrupted and the color rendering Ra value related to color reproducibility tends to decrease. Also, as illumination light, white light close to natural light (sunlight) is preferred. That is, the load required for visual recognition is small and it is not easy to get tired. As a measure related to such proximity, duv, which is the deviation (distance) from blackbody radiation that can be regarded as natural light, is used, and as illumination light, light with a small duv is preferred.

[0024] According to this aspect, the white light emitted from the light emitting surface has a Melanopic Ratio value of 0.65 or less, in addition to a color reproducibility of 80 or more and a duv within 0.02. Generally, when the emission intensity of green is reduced to decrease duv, the visual sensitivity decreases. However, according to this aspect, by adjusting the spectral intensity ratio of red and green, an organic EL element with a power efficiency within a practical range can be obtained. Also according to this aspect, it is a white light emitting organic EL element with good efficiency, luminance, and color rendering property, and an effect of reducing melatonin suppression can be expected.

[0025] According to this aspect, it includes a green-red mixed phosphorescent emission layer. That is, in this aspect, instead of a heterochromatic non-mixed sub-emission layer stacked type emission layer of a green phosphorescent emission layer and a red phosphorescent emission layer with an emission interface being the interface between a green phosphorescent emission layer containing a green phosphorescent material and a host material and not containing a red phosphorescent material and a red phosphorescent emission layer containing a red phosphorescent material and a host material and not containing a green phosphorescent material, it adopts a heterochromatic mixed single emission layer of a green-red mixed phosphorescent emission layer. That is, in this aspect, a green-red mixed phosphorescent emission layer containing a green phosphorescent material, a red phosphorescent material, and a phosphorescent emission layer host material constitutes a single layer. By doing so, the ratio of green phosphorescence to red phosphorescence can be kept constant without being affected by the position of the emission interface that moves depending on the current amount, and the change in color tone accompanying the magnitude of the current can be minimized. That is, high reliability can be ensured for color rendering properties and whiteness.

[0026] As described above, according to this aspect, it is white of a low color temperature TCP with less stimulation to the eyes and suppressed blue emission, and can emit white light with high color rendering properties at practical power efficiency. It is not only suitable as a warm color illumination light friendly to the eyes in a living environment at night, but also can emit white light that can contribute to improving the quality of sleep.

[0027] In a preferred aspect, the Melanopic Ratio value is 0.5 or less, the blue light emitting unit includes the blue fluorescent emission layer as the emission layer closest to the metal cathode layer, and the blue fluorescent emission layer includes a blue fluorescent material and a fluorescent emission host material.

[0028] According to this aspect, the effects of the present invention can be more effectively achieved.

[0029] In a more preferred aspect, the HTL adjustment layer includes a green fluorescent emission layer containing a green fluorescent material and a hole transporting fluorescent emission host material, and the maximum emission peak wavelength of the blue fluorescent material and the maximum emission peak wavelength of the green phosphorescent material are separated by 100 nm or more.

[0030] According to this aspect, it becomes a more efficient element.

[0031] A preferred aspect is that the spectrum of the white light has one blue emission peak in the range of 450 nm to 470 nm, one green emission peak in the range of 500 nm to 580 nm, and one red emission peak in the range of 590 nm to 630 nm, respectively. Further, when the blue emission peak intensity of the white light spectrum is set to 1, the intensity of the green emission peak is 2.5 times or more and 3.0 times or less.

[0032] According to this aspect, a higher-performance element can be obtained.

[0033] Further, the light-emitting functional layer preferably includes a relatively thin light-emitting layer with an average layer thickness of 5 nm or more and 30 nm or less. Due to the configuration of the present invention that can suppress the Melanopic Ratio value, it is possible to adjust the Melanopic Ratio value in the HTL adjustment layer of the fluorescent blue light-emitting unit where the blue fluorescent light-emitting layer emits blue light, which is adjacent to the cathode (metal cathode layer) side.

[0034] By the way, as described above, the organic EL element with the above-described aspect can suppress the suppression of melatonin secretion, so it is considered that it can prevent the subsequent sleep from being disturbed during work at night before going to bed, etc., and is considered suitable as illumination for objects to be visually recognized at night, etc. Also, if the organic EL panel equipped with the organic EL element with the above-described aspect can be changed to a desired position and a desired orientation with respect to the object to be visually recognized, its practicality is considered to be enhanced.

[0035] One aspect of the present invention derived based on the above idea is an illumination device including an organic EL panel having the above organic EL element, a holding portion for holding the organic EL panel, a fixing portion for sandwiching a part of the object to be visually recognized, and a connecting portion connecting the holding portion and the fixing portion and capable of changing the position and orientation of the holding portion with respect to the fixing portion, and capable of irradiating light from the organic EL panel toward the object to be visually recognized.

[0036] The "object to be visually recognized" as used herein refers to an object or structure that a user visually recognizes, for example, furniture such as books and desks.

[0037] According to this aspect, by attaching it to the object to be visually recognized with a fixing part and lighting the organic EL panel toward the object to be visually recognized, even when the object to be visually recognized is viewed just before going to bed at night, the burden on the user's eyes is small, and it is possible to suppress a decrease in the quality of sleep due to suppression of melatonin production by light. According to this aspect, since the position and orientation of the holding part with respect to the fixing part can be changed by the connecting part, the object to be attached can be illuminated with the organic EL panel in a desired posture.

Effects of the Invention

[0038] The organic EL element of the present invention is white light of a low color temperature TCP with suppressed blue light emission, which has little stimulation to the eyes related to melatonin secretion and generation, and can emit white light with high color rendering properties at practical power efficiency. Therefore, the load for visual recognition of objects including color vision is reduced, and it is not only suitable as warm-color illumination light that is gentle on the eyes in a living environment at night, but also can suppress unfavorable effects on the depth of sleep and the nerve cells of the retina of the eyes. As a result, it can contribute to improving the quality of sleep and is suitable as wellness lighting for further improving the living environment. According to the lighting device of the present invention, it can be fixed to an object to be visually recognized such as this, and the organic EL panel can illuminate the object to be visually recognized in a desired posture.

Brief Description of the Drawings

[0039]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0040] Hereinafter, embodiments of the present invention will be described in detail.

[0041] (Organic EL element 10) As shown in Fig. 1(a), the organic EL element 10 of the first embodiment of the present invention is a member having a planar spread, with a light-emitting surface 12 and a back surface 13 as both main surfaces, and emitting white light from a light-emitting region 11 on the light-emitting surface 12, and is preferably a plate-like member. Since the organic EL element 10 has a specific structure, it emits white light suitable for wellness lighting with practical power efficiency.

[0042] The white light emitted from the light-emitting surface 12 of such an organic EL element 10 has a correlated color temperature TCP of 2200K to 3000K, a distance duv from the blackbody radiation curve of the coordinate position in the CIE1931 chromaticity coordinate system of 0.02 or less, and a color rendering Ra value (average color rendering evaluation number) related to color reproducibility of 80 or more. Further, the white light has a Melanopic Ratio value, which is an index related to the stimulation of retinal nerve cells in the eye, of 0.65 or less, preferably 0.5 or less, with practical power efficiency and is suitable for wellness lighting.

[0043] From the viewpoint of suppressing the occurrence of DS (dark spots) and shortening of the element life, as shown in Fig. 1, the organic EL element 10 preferably includes a sealing layer 7 that covers the entire surface of the light-emitting region 11 on the back surface side when viewed in plan.

[0044] The white light preferably has a spectrum with one blue emission peak in the range of 450 nm to 470 nm, one green emission peak in the range of 500 nm to 580 nm, and one red emission peak in the range of 590 nm to 630 nm. When the blue emission peak intensity is set to 1, it is more preferable that the intensity of the green emission peak is 2.5 times or more and 3.0 times or less.

[0045] As shown in FIG. 1(b), the organic EL element 10 includes a light-transmitting substrate 2, a light-transmitting anode layer 3, a light-emitting functional layer 4 having a unit connection mechanism, and a metal cathode layer 5 in this order from the light-emitting surface 12 side to the back surface 13 side, and the overlapping portions of these coincide with the light-emitting region 11 in a plan view.

[0046] The unit connection mechanism is a mechanism having a function of connecting between a plurality of light-emitting units 4A and 4B included in the light-emitting functional layer 4. One feature of the light-emitting functional layer 4 is that it includes specific green-red light-emitting units 4A and blue light-emitting units 4B as light-emitting units. By including these light-emitting units 4A and 4B, the connection function of the unit connection mechanism is manifested, and the green-red light-emitting unit 4A and the blue light-emitting unit 4B are electrically connected.

[0047] (Light-emitting units 4A, 4B) The light-emitting units 4A and 4B generally have a hole-transporting surface and an electron-transporting surface as both surfaces, mainly composed of organic compounds, and are composed of a plurality of layers having hole-transporting properties, electron-transporting properties, and both charge-transporting properties (also referred to as bipolar) capable of transporting charges of these holes and electrons.

[0048] As such organic compounds, known ones such as low molecular weight dye materials and conjugated polymer materials generally used in organic EL elements can be used, and they can be formed into films by appropriately known methods such as vacuum evaporation, sputtering, CVD, and various coating methods. However, from the viewpoint of obtaining high-performance elements, it is preferable to form films by vacuum evaporation.

[0049] In addition, such light-emitting units 4A and 4B may have, in addition to a light-emitting layer that actually emits light in the layer, a plurality of layers such as a hole injection layer (hereinafter sometimes referred to as HIL), a hole transport layer (hereinafter sometimes referred to as HTL), an electron transport layer (hereinafter sometimes referred to as ETL), and an electron injection layer (hereinafter sometimes referred to as EIL) as layers that do not actually emit light. These layers other than the light-emitting layer mainly have a function of promoting light emission in the light-emitting layer, and in this specification, the transport layers that do not emit light and the layers that have both a light-emitting and transport function are collectively referred to as a hole transport layer and an electron transport layer. That is, the hole transport layer refers to a layer that transports holes to the light-emitting layer regardless of whether it emits light itself and assists the light emission of the light-emitting layer. The electron transport layer refers to a layer that transports electrons to the light-emitting layer regardless of whether it emits light itself and assists the light emission of the light-emitting layer.

[0050] (Unit connection mechanism) The unit connection mechanism has a function of connecting between the green-red light-emitting unit 4A and the blue light-emitting unit 4B. Specifically, when the organic EL element 10 is energized, it has a function of injecting electrons to the green-red light-emitting unit 4A side and injecting holes to the blue light-emitting unit 4B side.

[0051] (Transparent substrate 2) The transparent substrate 2 is a member having a planar spread and made of a light-transmitting material, and can be a glass substrate or a resin film substrate. From the viewpoint of suppressing moisture intrusion into the organic EL element 10 that causes performance degradation, a glass substrate is preferable for the transparent substrate 2, and it can also be a flexible substrate.

[0052] (Transparent anode layer 3) As the material of the transparent anode layer 3, transparent conductive metal oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO2), and zinc oxide (ZnO) can be adopted. From the viewpoint of obtaining a high-performance element, highly transparent ITO or IZO is preferable.

[0053] (Green-red light-emitting unit 4A) The green-red light-emitting unit 4A has a green-red phosphorescent mixed light-emitting layer 4AGR that emits green light and red light, has a hole-transporting surface with hole-transporting properties and an electron-transporting surface with electron-transporting properties as both surfaces, and the green-red phosphorescent mixed light-emitting layer 4AGR contains a green phosphorescent material, a red phosphorescent material, and a phosphorescent light-emitting layer host material. The green-red light-emitting unit 4A preferably includes, in order from the side of the translucent anode layer 3, a hole injection layer 4A1, a hole transport layer 4A2, a green-red phosphorescent mixed light-emitting layer 4AGR, an electron transport layer 4A3, and an electron injection layer 4A4.

[0054] It is preferable that the maximum emission peak wavelength of this green phosphorescent material is separated from the maximum emission peak wavelength of the blue fluorescent material described later by 100 nm or more.

[0055] (Blue light-emitting unit 4B) As shown in FIG. 1(b), the blue light-emitting unit 4B includes a blue fluorescent light-emitting layer 4BB that emits blue light, has a hole-transporting surface with hole-transporting properties and an electron-transporting surface with electron-transporting properties as both surfaces, and adjacent to the blue fluorescent light-emitting layer 4BB and on the unit connection mechanism side, includes an HTL adjustment layer 4B1 as a hole-transporting layer with an average thickness of 50 nm or more.

[0056] The blue fluorescent light-emitting layer 4BB is preferably the light-emitting layer closest to the metal cathode layer 5, includes a blue fluorescent material and a fluorescent light-emitting host material, and the fluorescent light-emitting host material of the blue fluorescent light-emitting layer 4BB is an electron-transporting host material.

[0057] The HTL adjustment layer 4B1 includes a light-emitting layer of a color different from blue, and may include, for example, a green light-emitting layer that emits green light. The HTL adjustment layer 4B1 preferably includes a hole-transporting green fluorescent light-emitting layer that includes a green fluorescent material and a hole-transporting fluorescent light-emitting host material.

[0058] The blue light-emitting unit 4B preferably includes, for example, in order from the side of the translucent anode layer 3, a hole injection layer 4B2, an HTL adjustment layer 4B1, a blue fluorescent light-emitting layer 4BB, an electron transport layer 4B3, and an electron injection layer 4B4.

[0059] (Metal cathode layer 5) The metal cathode layer 5 can be formed using various metal materials. Among them, white lustrous metals are preferred, and among these, silver (Ag) and aluminum (Al) are more preferred.

[0060] (Out-Coupling layer) For the organic EL element 10, in order to improve the angular dependence optical characteristics of its luminance and color, it is preferable to provide an out-coupling layer 6 (OCL) on the outermost surface of the region including at least the light-emitting region 11 on the light-emitting surface 12 side.

[0061] Hereinafter, the layers and materials used above will be described in detail.

[0062] (Hole injection layer) The hole injection layer is, for example, a layer that takes in holes from the positive electrode (transparent anode layer 3) and injects holes into the hole transport layer. Also, from the viewpoint of improving luminance by improving the transparency of the hole injection layer, a material obtained by doping a hole transporting material with an electron-accepting dopant can also be preferably adopted. The hole injection layer preferably has an average thickness of 0.1 nm or more and 20 nm or less.

[0063] (Hole transport layer) The hole transport layer is a layer that efficiently transports holes from the hole injection layer side to the light-emitting layer while restricting the movement of electrons to the positive electrode (transparent anode layer 3) side. Known hole transporting materials can be used as the material of the hole transport layer. The hole transport layer preferably has an average thickness of 1 nm or more and 200 nm or less.

[0064] (Light-emitting layer) The light-emitting layer is generally a layer in which a light-emitting material is doped into a host material having hole transporting properties or electron transporting properties, and is a layer in which holes flowing in from the hole transport layer and electrons flowing in from the electron transport layer are combined by applying an electric field to generate light-emitting excitons. The light-emitting layer preferably has an average thickness of 1 nm or more and 40 nm or less.

[0065] (Electron transport layer) The electron transport layer is a layer that efficiently transports electrons from the electron injection layer side to the light-emitting layer while restricting the movement of electrons to the negative electrode (metal cathode layer 5) side. As the material of the electron transport layer, known electron transporting materials can be used. The electron transport layer preferably has an average thickness of 1 nm or more and 200 nm or less.

[0066] (Electron injection layer) The electron injection layer is, for example, a layer that takes in electrons from the negative electrode (metal cathode layer 5) and injects electrons into the electron transport layer. From the viewpoint of improving the luminance by improving the transparency of the electron injection layer, those obtained by doping an electron transporting material with an electron donating dopant can also be preferably adopted as the electron injection layer. The electron injection layer preferably has an average thickness of 0.1 nm or more and 20 nm or less.

[0067] (Hole transporting material) As the hole transporting material, for example, triphenylamine-based compounds, carbazole-based compounds, etc. can be adopted.

[0068] (Electron transporting material) As the electron transporting material, for example, quinolinolato-based metal complexes, anthracene-based compounds, oxadiazole-based compounds, triazole-based compounds, phenanthroline-based compounds, silole-based compounds, etc. can be adopted.

[0069] (Light-emitting material) The light-emitting materials include fluorescent materials and phosphorescent materials which generally have higher luminous efficiency than the former.

[0070] As red fluorescent light-emitting materials, rubrene, DCM, DCM2, DBzR, etc. can be adopted.

[0071] As green fluorescent light-emitting materials, coumarin 6, C545T, etc. can be adopted.

[0072] As the blue fluorescent emitting material, perylene 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1-biphenyl (BCzVBi), 4,4'-bis[4-(di-p-toluidino)styryl]biphenyl (DPAVBi), etc. can be adopted.

[0073] As the red phosphorescent emitting material, iridium complexes such as (bzq)2Ir(acac), (btp)2Ir(acac), Ir(bzq)3, Ir(piq)3, etc. can be adopted.

[0074] As the green phosphorescent emitting material, iridium complexes such as (ppy)2Ir(acac), Ir(ppy)3, etc. can be adopted.

[0075] As the blue phosphorescent emitting material, iridium complexes such as FIrpic, FIr6, Ir(Fppy)3, etc. can be adopted.

[0076] (Electron accepting dopant) As the electron accepting dopant, tetracyanoquinodimethane-based compounds, molybdenum oxide (MoO3), tungsten oxide (WO3), vanadium oxide (V2O5), etc. can be adopted.

[0077] (Electron donating dopant) As the electron donating dopant, alkali metals, alkaline earth metals, rare earth metals, compounds of these metals, phthalocyanine complexes having these metals as the central metal, dihydroimidazole compounds, etc. can be adopted.

[0078] According to the organic EL element 10 of the present embodiment, since white light with low blue emission intensity and high color rendering property is emitted, the load for visual recognition of objects including color tones is reduced, it is gentle to the eyes in the living environment at night, and it can contribute to improving the quality of sleep, and it is suitable as wellness lighting.

[0079] According to the organic EL element 10 of the present embodiment, the green-red light emitting unit 4A includes a green-red phosphorescent mixed light emitting layer 4AGR containing a green phosphorescent material, a red phosphorescent material, and a phosphorescent light emitting layer host material. Therefore, the ratio of green phosphorescence to red phosphorescence is kept constant without being affected by the position of the light emitting interface that moves depending on the current amount, and the change in color tone accompanying the magnitude of the current can be minimized. That is, high reliability can be ensured for color rendering properties and whiteness.

[0080] According to the organic EL element 10 of the present embodiment, since the green-red light emitting unit 4A is located on the light emitting side (the glass substrate 2 side) with respect to the blue light emitting unit 4B, the blue light emitted by the blue light emitting unit 4B passes through the green-red light emitting unit 4A and is emitted. Therefore, the blue light emission spectrum intensity can be reduced.

[0081] Subsequently, the lighting device 100 using the organic EL element 10 of the present embodiment will be described.

[0082] As shown in FIG. 2, the lighting device 100 includes an organic EL panel 101, a holding portion 102, a clip portion 103 (fixing portion), and a connecting portion 104, and illuminates the object to be visually recognized 200 with the organic EL panel 101. The organic EL panel 101 has the organic EL element 10 and a battery portion (not shown), and it is possible to irradiate diffused light from the light emitting surface 105 by supplying the power stored in the battery portion to the organic EL element 10. The battery portion is preferably a secondary battery that can be charged and discharged, and more preferably a lithium ion secondary battery from the viewpoint of being lighter in weight.

[0083] The holding portion 102 is a portion that holds the organic EL panel 101. The clip portion 103 is a fixing portion that is fixed to the object to be visually recognized 200 by sandwiching a part of the object to be visually recognized 200. The connecting portion 104 is a portion that connects the holding portion 102 and the clip portion 103 and can change the position and orientation of the holding portion 102 with respect to the clip portion 103, and is specifically a flexible arm.

[0084] Next, a case where the lighting device 100 of the present embodiment is attached to and used on a book, which is an example of the object to be visually recognized 200, will be described.

[0085] As shown in FIG. 2, the cover 201 of the book, which is the object to be visually recognized 200, is sandwiched by the clip portion 103, and the organic EL panel 101 is oriented such that the light emitting surface 105 faces the paper surface 202 of the book by adjusting the position and orientation of the connecting portion 104. Then, the organic EL panel 101 is turned on to irradiate the paper surface 202 with light.

[0086] According to the lighting device 100 of the present embodiment, by attaching it to the cover 201 of the object to be visually recognized 200 with the clip portion 103 and orienting the organic EL panel 101 toward the paper surface 202 of the object to be visually recognized 200, even when looking at the paper surface 202 of the object to be visually recognized 200 just before going to bed at night, the burden on the user's eyes is small, and it is possible to suppress a decrease in the quality of sleep due to suppression of melatonin production by light.

[0087] In the above-described embodiment, the HTL adjustment layer 4B1 included the green fluorescent light emitting layer, but the present invention is not limited to this. The HTL adjustment layer 4B1 may not include the green fluorescent light emitting layer. That is, the HTL adjustment layer 4B1 may not emit light.

[0088] In the above-described embodiment, the clip portion 103 was used as the fixing portion, but the present invention is not limited to this. The fixing portion may be other fixing means such as a screw or a hook.

[0089] In the above-described embodiment, the case where the object to be visually recognized 200 is a book has been described, but the present invention is not limited to this. The object to be visually recognized 200 may be any object that the user visually recognizes and can be fixed by the fixing portion.

[0090] In the above-described embodiments, as long as it is included in the technical scope of the present invention, each component can be freely replaced or added between the embodiments.

Example

[0091] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. It should be noted that the present invention is not limited to the following examples, and can be appropriately modified and implemented without changing the gist.

[0092] (Example 1) The organic EL element 10 of Example 1 has a structure as shown in the cross-sectional configuration diagram of FIG. 8. On the element formation surface of the glass substrate 2, an ITO layer 3 is formed as a translucent anode layer 3 in sequence. Next, on this ITO layer 3, a green-red phosphorescent unit 4A, a blue-green fluorescent unit 4B, and an Al layer 5 are formed as a metal cathode layer 5 in sequence, and a two-layer stacked element of anode layer 3 / green-red phosphorescent unit 4A / unit connection mechanism / blue-green fluorescent unit 4B / cathode layer 5 is fabricated.

[0093] Here, as this blue-green fluorescent unit 4B, in order to reduce the deviation duv from blackbody radiation while alleviating the increase in the intensity of blue light due to reflection at the metal cathode layer 5, adjacent to the blue fluorescent light-emitting layer 4BB and on the unit connection mechanism side, it includes an 80-nm HTL adjustment layer 4B1 that also functions as a green light-emitting layer as a thicker hole-transporting layer, and the blue fluorescent light-emitting layer 4BB in the blue-green fluorescent unit 4B is 27 nm.

[0094] Also here, in the green-red phosphorescent unit 4A, the green-red phosphorescent mixed light-emitting layer is 15 nm and the ETL on the cathode layer side is 50 nm.

[0095] FIGS. 3 and 4 show the current density of 3 mA / cm of the organic EL element of this Example 1 2 It is the front emission spectrum during lighting, and FIG. 4 is the blue region spectrum of FIG. 3. That is, FIG. 4 has the scale changed in accordance with the blue emission spectrum on the vertical axis.

[0096] The color temperature TCP of the emitted light of the organic EL element of Example 1 calculated from the spectrum of FIG. 3 was 2250K, the deviation duv from blackbody radiation was 0.011, the color reproducibility Ra was 80, and the Melanopic Ratio value, which is an index of the degree of stimulation to the retinal nerve cells of the eye, was 0.208. Also, from FIG. 4, it can be seen that the organic EL element of Example 1 has one blue emission peak in the range of 450 nm to 470 nm. The measurement results of each are summarized in Table 1 together with those of other Examples and Comparative Examples.

[0097]

Table 1

[0098] (Comparative Example 1) The organic EL element of Comparative Example 1 is a super high color rendering element with a color temperature exceeding 3000K. Using the same glass substrate 2, ITO layer 3, and Al layer 5 as in Example 1, as the light-emitting functional layer 4, from the ITO layer 3 side to the Al layer 5 side, a blue light-emitting unit 4B and a green / red light-emitting unit 4A are formed in this order to form a two-layer stacked element of anode layer 3 / blue light-emitting unit 4B / green / red light-emitting unit 4A / cathode layer 5. That is, the green / red light-emitting unit 4A is provided on the Al layer 5 side with respect to the blue light-emitting unit 4B, which is different from Example 1 in that no unit connection mechanism is provided.

[0099] Similar to Example 1, when calculated from the front emission spectrum of the organic EL element of Comparative Example 1, the color temperature TCP was 3526K, duv was 0.013, Ra was 89, and the Melanopic Ratio value was 0.605.

[0100] (Example 2) As the organic EL element of Example 2, it is the same as Example 1 except that the thickness of the HTL adjustment layer is 90 nm and the cathode layer side ETL is 70 nm.

[0101] FIG. 5 is the front emission spectrum when the current density of the organic EL element of this Example 2 is 3 mA / cm 2 during lighting.

[0102] Similar to Example 1, when the current density is 3 mA / cm 2When the organic EL element of Example 2 was lit, the color temperature TCP was 2350K, duv was 0.00018, Ra was 88, and the Melanopic Ratio value was 0.407, as calculated from the front emission spectrum.

[0103] (Comparative Example 2) As the organic EL element of Comparative Example 2, it is made the same as in Example 1, except that the thickness of the HTL adjustment layer is 40 nm and the thickness of the ETL on the cathode layer 5 side is 50 nm.

[0104] Fig. 6 shows the front emission spectrum at a current density of 3 mA / cm² of the organic EL element of this Comparative Example 2 when lit. 2 when lit.

[0105] Similar to Example 1, when calculated from the front emission spectrum of the organic EL element of Comparative Example 2, the color temperature TCP was 3516K, duv was -0.00195, the color reproducibility Ra was 90, and the Melanopic Ratio value was 0.681.

[0106] (Example 3) As the organic EL element of Example 3, it is made the same as in Example 1, except that the thickness of the HTL adjustment layer is 55 nm, the blue fluorescent emission layer in the blue fluorescent unit 4B is 3 nm, the concentration of the blue light-emitting material is 1 wt%, the green and red phosphorescent emission layer in the green and red phosphorescent unit 4A is 23 nm, and the thickness of the ETL on the cathode layer 5 side is 70 nm.

[0107] Fig. 7 shows the front emission spectrum at a current density of 3 mA / cm² of the organic EL element of this Example 3 when lit. 2 when lit.

[0108] Similar to Example 1, when calculated from the front emission spectrum of the organic EL element of Example 3, the color temperature TCP was 2921K, duv was -0.009, Ra was 94 which is good, but the Melanopic Ratio value was 0.632.

[0109] (Comparative Example 3) As an organic EL element of the low color temperature TCP 2250K-class element of Comparative Example 3, the same procedure as in Example 1 is carried out except that the thickness of the HTL adjustment layer is 8 nm.

[0110] Similar to Example 1, when calculated from the front emission spectrum of the organic EL element of Comparative Example 3, the color temperature TCP was 2273K, duv was 0.019, the color rendering property Ra was 78, and the Melanopic Ratio value was 0.204.

[0111] (Summary of Examples and Comparative Examples) The Melanopic Ratio value of the high color rendering element of more than 3000K in Comparative Example 1 was 0.605, but it was suppressed to 0.208 in the organic EL element of Example 1. Further, the Melanopic Ratio value of the organic EL element of Example 2 of the present invention was 0.407.

[0112] In the emission spectrum of the high color rendering element of more than 3000K in Comparative Example 1, the intensity ratio of blue: green: red is 1: 1.5: 2.5, and in the emission spectrum of the low color temperature TCP 2250K-class element of Comparative Example 3, the intensity ratio of blue: green: red is 1: 19: 36. In order to reduce the deviation (distance) of blackbody radiation and lower the luminous intensity of green, the visual sensitivity decreases. However, in order to increase the power efficiency as much as possible, in the element of Example 2, the spectral intensity ratio of red and green was adjusted to (red: green) 1.8: 1.

[0113] Further, by suppressing the blue emission intensity, it is possible to suppress the stimulation to the retina nerve cells during sleep or the like. As an index of the degree of stimulation to the retina nerve cells, there is a Melanopic Ratio value, and the element according to the example is designed so that the value becomes small.

[0114] Regarding the organic EL element of Example 3, generally, when the thickness of the blue emission layer is reduced or the content rate of the blue emission material is decreased, the blue emission intensity tends to decrease. However, in the organic EL element whose spectrum is shown in FIG. 7 of Example 3, the fluorescent blue emission layer is 3 nm and the blue emission material is 1 wt%. The organic EL element of Example 3 had a higher blue emission intensity than expected, and the color temperature TCP was 3000 K or lower, but the Melanopic Ratio value was 0.632. Therefore, from the viewpoint of solving the problems of the present invention, the organic EL element of Example 1 is considered to be superior.

Explanation of Signs

[0115] 10. White light-emitting organic EL element 2. Transparent substrate (glass substrate) 3. Transparent anode layer (ITO layer) 4. Light-emitting functional layer 4A. Green / red light-emitting unit 4B. Blue light-emitting unit 4B1. HTL adjustment layer 4BB. Blue fluorescent light-emitting layer 5. Metal cathode layer 6. Out-coupling layer 7. Encapsulation layer 100. Lighting device 101. Organic EL panel 102. Holding part 103. Clip part 104. Connection part 105. Light-emitting surface 200. Object to be visually recognized

Claims

1. An organic EL element having a light emitting surface and a back surface as both main surfaces, including a transparent substrate, a transparent anode layer, a light emitting functional layer, and a metal cathode layer in this order from the light emitting surface side, wherein the light emitting functional layer has a green-red light emitting unit, a unit connection mechanism, and a blue light emitting unit, the unit connection mechanism is a mechanism that injects electrons into the green-red light emitting unit side and injects holes into the blue light emitting unit side when energized, the green-red light emitting unit includes a green-red phosphorescent mixed light emitting layer containing a green phosphorescent material, a red phosphorescent material, and a phosphorescent light emitting layer host material, and emits green light and red light when energized, the blue light emitting unit includes a blue fluorescent light emitting layer that emits blue light when energized and an HTL adjustment layer adjacent to the blue fluorescent light emitting layer on the unit connection mechanism side, the HTL adjustment layer is a hole transporting layer having an average thickness of 50 nm or more, from the light emitting surface, white light having a correlated color temperature TCP of 2200 K to 3000 K, a distance duv from the black body radiation curve of the coordinate position in the CIE1931 chromaticity coordinate system of 0.02 or less, a color rendering index Ra of 80 or more, and a Melanopic Ratio value of 0.65 or less can be emitted, the Melanopic Ratio value is calculated by the following formula (1), and the organic EL element. 【Number 1】 Here, Lamp represents the spectral distribution of the organic EL element, Circadian represents the sensitivity curve of ipRGC, and Visual represents the visual sensitivity curve in the photopic vision of humans.

2. the Melanopic Ratio value is 0.5 or less, the blue light emitting unit includes the blue fluorescent light emitting layer as the light emitting layer closest to the metal cathode layer, the blue fluorescent light emitting layer includes a blue fluorescent material and a fluorescent light emitting host material, and the organic EL element according to claim 1.

3. the HTL adjustment layer includes a green fluorescent light emitting layer containing a green fluorescent material and a hole transporting fluorescent light emitting host material, the maximum emission peak wavelength of the blue fluorescent material and the maximum emission peak wavelength of the green phosphorescent material are separated by 100 nm or more, and the organic EL element according to claim 2.

4. the spectrum of the white light has one blue emission peak in the range of 450 nm to 470 nm, one green emission peak in the range of 500 nm to 580 nm, and one red emission peak in the range of 590 nm to 630 nm, respectively. Furthermore, in the spectrum of the white light, when the emission intensity of the blue emission peak is set to 1, the emission intensity of the green emission peak is 2.5 times or more and 3.0 times or less. The organic EL element according to any one of claims 1 to 3.

5. An organic EL panel having the organic EL element according to any one of claims 1 to 4, a holding portion that holds the organic EL panel, a fixing portion that is fixed to an object to be visually recognized, and the holding portion and the fixing portion are connected, and a connecting portion that can change the position and orientation of the holding portion with respect to the fixing portion. An illumination device capable of irradiating light from the organic EL panel toward the object to be visually recognized.

Images