WO2014185063A1 - 有機エレクトロルミネッセンス素子及び照明装置 - Google Patents
有機エレクトロルミネッセンス素子及び照明装置 Download PDFInfo
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
- H10K50/13—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit
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- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
- H10K50/13—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit
- H10K50/131—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit with spacer layers between the electroluminescent layers
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- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
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- H10K50/00—Organic light-emitting devices
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- H10K50/85—Arrangements for extracting light from the devices
- H10K50/854—Arrangements for extracting light from the devices comprising scattering means
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- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/30—Devices specially adapted for multicolour light emission
- H10K59/32—Stacked devices having two or more layers, each emitting at different wavelengths
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2105/00—Planar light sources
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2115/00—Light-generating elements of semiconductor light sources
- F21Y2115/10—Light-emitting diodes [LED]
- F21Y2115/15—Organic light-emitting diodes [OLED]
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- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/12—Passive devices, e.g. 2 terminal devices
- H01L2924/1204—Optical Diode
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- H10K2102/00—Constructional details relating to the organic devices covered by this subclass
- H10K2102/301—Details of OLEDs
- H10K2102/302—Details of OLEDs of OLED structures
- H10K2102/3023—Direction of light emission
Definitions
- the present invention relates to an organic electroluminescent device and a lighting device using the same.
- organic electroluminescent element As an organic electroluminescent element (hereinafter, also referred to as "organic EL element”), it is general to have a structure in which an anode made of a transparent electrode, a hole transport layer, a light emitting layer, an electron injection layer and a cathode are sequentially laminated on the surface of a transparent substrate.
- organic EL element light emitted from the light emitting layer is extracted to the outside through the transparent electrode and the transparent substrate by applying a voltage between the anode and the cathode.
- an organic EL element In the case of producing various colors as light emission colors in an organic EL element, it is performed to mix the light emission colors of light emitting materials having different wavelengths. In particular, in order to obtain light emission of a color important for lighting applications, for example, mixing of three colors of red light emission, green light emission and blue light emission is performed.
- a fluorescent light emitting material and a phosphorescent light emitting material are known.
- an organic EL element having a multi-unit structure in which a fluorescent light emitting unit and a phosphorescent light emitting unit are laminated has been proposed (see, for example, Japanese Patent No. 4408382 and Japanese Patent No. 4797438).
- the organic EL element having a multi-unit structure is also called a so-called tandem element, and has a structure in which light emission is performed for each light emitting unit, so that an element configuration suitable for each light emitting unit can be formed. There is.
- This invention is made in view of said situation, and it aims at providing the organic electroluminescent element and illuminating device with high luminous efficiency.
- the present invention relates to an organic electroluminescent device.
- the organic electroluminescent device comprises at least three light emitting units.
- the plurality of light emitting units have one or more short wavelength light emitting units having a weight average light emission wavelength ⁇ S of 380 nm or more and less than 550 nm represented by the following formula (1), and a weight average light emission wavelength ⁇ S represented by the following formula (1) And a plurality of long wavelength light emitting units of 550 nm or more and 780 nm or less.
- the number of long wavelength light emitting units is greater than the number of short wavelength light emitting units.
- P ( ⁇ ) represents the spectral intensity at each wavelength.
- the present invention relates to a lighting device.
- a lighting device comprises the above-mentioned organic electroluminescent device.
- the organic electroluminescent element and illuminating device with high luminous efficiency can be obtained.
- FIG. 7 is composed of FIGS.
- FIG. 7 is a graph showing an example of the absorption spectrum of the organic material.
- FIG. 7A is an overall view
- FIG. 7B is an enlarged view.
- FIG. 8 is composed of FIGS. 8A and 8B.
- FIG. 8 shows an example of the relationship between the light emission angle and the light quantity distribution.
- FIG. 8A is a schematic view of a light distribution pattern.
- FIG. 8B is a graph of radiant flux ratio.
- FIG. 9 is composed of FIGS. 9A and 9B.
- FIG. 9 is an explanatory view for explaining an example of the concavo-convex structure.
- FIG. 9A is a plan view
- FIG. 9B is a cross-sectional view.
- FIG. 10 is composed of FIGS. 10A and 10B.
- FIG. 10 is a plan view showing an example of the concavo-convex structure 10.
- FIG. 10A is an example of a square grid.
- FIG. 10B is an example of a hexagonal grid
- the organic EL element is provided with at least three light emitting units 1.
- the plurality of light emitting units 1 has one or more short wavelength light emitting units 1S having a weight average light emitting wavelength ⁇ S of 380 nm or more and less than 550 nm shown by the formula (1), and a weight average light emitting wavelength ⁇ S shown by the formula (1) And a plurality of long wavelength light emitting units 1L of 550 nm or more and 780 nm or less.
- the number of long wavelength light emitting units 1L is larger than the number of short wavelength light emitting units 1S. According to this organic EL element, by forming the long wavelength light emitting unit 1L more than the short wavelength light emitting unit 1S, it is possible to enhance the overall light emission efficiency. Therefore, an organic EL element having high luminous efficiency can be obtained.
- FIG. 1 shows an example of the layer configuration of an organic electroluminescent element (organic EL element).
- the organic EL element is provided with at least three light emitting units 1.
- the number of light emitting units 1 is three.
- the number of light emitting units 1 may be four or more.
- the number of light emitting units 1 is preferably seven or less, more preferably five or less, and four or less. More preferably, three are even more preferred.
- the light emitting unit 1 is a laminated structure having a function of emitting light when a voltage is applied between an anode and a cathode.
- the structure having a plurality of light emitting units 1 is called a multi-unit structure.
- a plurality of light emitting units 1 overlapping in the thickness direction are electrically connected in series between one anode and one cathode.
- the light emitting unit 1 has a light emitting layer 5.
- the light emitting layer 5 is a layer containing a light emitting material (dopant).
- the light emitting layer 5 is composed of a light emitting material and a host material that receives the light emitting material.
- the light emitting layer 5 may have a single layer structure or a multilayer structure.
- the plurality of light emitting units 1 are disposed so as to be sandwiched between a pair of electrodes.
- One of the pair of electrodes is an anode, and the other is a cathode.
- the plurality of light emitting units 1 are disposed between the light transmitting electrode 2 and the light reflecting electrode 3.
- Light transmission includes transparency and translucency.
- the anode may be configured of the light reflective electrode 3 and the cathode may be configured of the light transmissive electrode 2.
- An intermediate layer 4 is provided between the adjacent light emitting units 1.
- the intermediate layer 4 is a layer which can give electrons to the light emitting unit 1 on the anode side and can give holes to the light emitting unit 1 on the cathode side.
- the intermediate layer 4 can be composed of a charge generation layer. Since the intermediate layer 4 is a layer disposed between the two light emitting units 1, generally, the number of the intermediate layers 4 is smaller by one than the number of light emitting units 1.
- a plurality of (two or more) intermediate layers 4 are provided in the organic EL device having three or more light emitting units 1. In the organic EL device having three or more light emitting units 1, a plurality of (two or more) intermediate layers 4 are provided. In FIG. 1, the number of intermediate layers 4 is two.
- a laminated structure from the light transmitting electrode 2 to the light reflecting electrode 3, that is, the light transmitting electrode 2, the plurality of light emitting units 1 and the plurality of intermediate layers 4, and the light reflecting electrode 3 are organic light emitting laminates. Configured.
- the organic light emitting laminate is a laminate that generates light by application of a voltage.
- the organic light emitting laminate is formed on the substrate 6.
- the light transmitting electrode 2 is disposed on the side of the substrate 6 of the organic light emitting laminate.
- the substrate 6 is a base material that supports the organic light emitting laminate.
- the light transmissive electrode 2, the plurality of light emitting units 1, and the light reflective electrode 3 are supported by a substrate 6.
- layers may be formed in order from the substrate 6 side.
- the substrate 6 is preferably light transmissive. Of course, it may be a structure (top emission structure) in which light is extracted from the side opposite to the substrate 6. In that case, the substrate 6 can be disposed on the light reflective electrode 3 side of the organic light emitting laminate.
- a light diffusion layer 7 is provided between the substrate 6 and the light transmitting electrode 2.
- the organic EL element preferably has a light diffusion layer 7 between the substrate 6 and the light transmitting electrode 2.
- the light diffusion layer 7 has a function of extracting more light traveling obliquely with respect to the substrate 6. By having the light diffusion layer 7, the light extraction property can be enhanced. Of course, the light diffusion layer 7 may be provided as needed.
- the light emitting unit 1 preferably has a charge transfer layer 8 for transferring charges to the light emitting layer 5.
- a charge transfer layer 8 for transferring charges to the light emitting layer 5.
- a layer that promotes the movement of holes from the anode or the intermediate layer 4 to the light emitting layer 5 can be provided on the anode side of the light emitting layer 5 (in this example, the light transmitting electrode 2 side).
- the hole transport layer 8 h is provided on the light transmitting electrode 2 side of the light emitting layer 5.
- a hole injection layer may be further provided between the hole transport layer 8 h and the electrode, and between the hole transport layer 8 h and the intermediate layer 4. As a result, the hole injection property can be enhanced, and charge transfer can be made smoother.
- a layer that promotes the movement of electrons from the cathode or the intermediate layer 4 to the light emitting layer 5 can be provided on the cathode side (the light reflective electrode 3 side in this example) of the light emitting layer 5.
- the electron transport layer 8 e is provided on the light reflective electrode 3 side of the light emitting layer 5.
- An electron injection layer may be further provided between the electron transport layer 8 e and the electrode, or between the electron transport layer 8 e and the intermediate layer 4. As a result, the injection of electrons can be enhanced and charge transfer can be made smoother.
- each configuration can be numbered from the light reflective electrode 3 side.
- This organic EL element has three light emitting units 1. Therefore, it can be said that the three light emitting units 1 are arranged in the order of the first light emitting unit 1a, the second light emitting unit 1b, and the third light emitting unit 1c from the light reflective electrode 3 side.
- This organic EL element has two intermediate layers 4. Therefore, it can be said that the two intermediate layers 4 are disposed in the order of the first intermediate layer 4a and the second intermediate layer 4b from the light reflective electrode 3 side.
- the first intermediate layer 4a is an intermediate layer 4 disposed between the first light emitting unit 1a and the second light emitting unit 1b.
- the second intermediate layer 4 b is an intermediate layer 4 disposed between the second light emitting unit 1 b and the third light emitting unit 1 c.
- the light emitting layer 5 included in the first light emitting unit 1a is defined as a first light emitting layer 5a.
- the light emitting layer 5 included in the second light emitting unit 1 b is defined as a second light emitting layer 5 b.
- the light emitting layer 5 included in the third light emitting unit 1c is defined as a third light emitting layer 5c.
- the plurality of light emitting units 1 are composed of one or more short wavelength light emitting units 1S and a plurality of long wavelength light emitting units 1L.
- the plurality of light emitting units 1 is preferably one aspect including one short wavelength light emitting unit 1S and two long wavelength light emitting units 1L.
- the organic EL element has one short wavelength light emitting unit 1S and two long wavelength light emitting units 1L. When the number of light emitting units 1 is three, light extraction can be enhanced with a simpler structure.
- the short wavelength light emitting unit 1S is a light emitting unit 1 having a weighted average light emission wavelength ⁇ S of 380 nm or more and less than 550 nm, which is represented by the following formula (1).
- the long wavelength light emitting unit 1L is a light emitting unit 1 having a weighted average light emitting wavelength ⁇ S represented by the following formula (1) of 550 nm or more and 780 nm or less. That is, the short wavelength light emitting unit 1S is a light emitting unit 1 mainly emitting light having a wavelength shorter than 550 nm in the visible light region, and the long wavelength light emitting unit 1L is light having a long wavelength of 550 nm or more in the visible light region.
- the light emitting unit 1 mainly emits light.
- the weighted average emission wavelength ⁇ S is a wavelength represented by the following formula (1), and is obtained by integrating the emission spectrum.
- P ( ⁇ ) represents the spectral intensity at each wavelength.
- (lambda) shows a wavelength and is a variable from 380 (nm) to 780 (nm).
- the weighted average emission wavelength ⁇ S is a wavelength obtained by weighting and averaging each wavelength by the light intensity.
- the weighted average emission wavelength ⁇ S is obtained from the emission spectrum of the light emitting unit 1.
- the weighted average emission wavelength ⁇ S of the light emitting unit 1 is defined as the wavelength in each light emitting unit 1.
- the weighted average emission wavelength of the light emitting material is the weighted average emission wavelength ⁇ S of the light emitting unit 1.
- the weighted average light emission wavelength of the light emission spectrum produced by mixing the light emitting materials in the light emitting unit 1 is the weight average light emitting wavelength of the light emitting unit 1 It becomes ⁇ S.
- the number of light emitting materials is two or more, the case where there are a plurality of light emitting layers 5 and the case where one light emitting layer 5 includes a plurality of light emitting materials are included.
- the number of long wavelength light emitting units 1L is larger than the number of short wavelength light emitting units 1S.
- the number of long wavelength light emitting units 1L is two
- the number of short wavelength light emitting units 1S is one
- the number of long wavelength light emitting units 1L is larger than the number of short wavelength light emitting units 1S.
- the three light emitting units 1 are configured by one short wavelength light emitting unit 1S and two long wavelength light emitting units 1L. Even when the number of light emitting units 1 is four or more, similarly, the plurality of light emitting units 1 is configured such that the number of long wavelength light emitting units 1L is larger than the number of short wavelength light emitting units 1S. .
- the light emission efficiency of the long wavelength light emitting unit 1L is preferably higher than the light emission efficiency of the short wavelength light emitting unit 1S.
- the light emission efficiency of the long wavelength light emitting unit 1L is set to that of the short wavelength light emitting unit 1S. It can be easily made higher than the light emission efficiency.
- the long wavelength light emitting units 1L with higher light emission efficiency can be increased to enhance the overall light emission efficiency, and the light extraction property is high.
- the element can be configured. Further, by providing a plurality of long wavelength light emitting units 1L, it is easy to adjust the light emission color to various colors, and it is possible to obtain an organic EL element having a wide color reproduction region. Therefore, it is possible to obtain an organic EL element having high light emission efficiency and excellent color development. Particularly when used in lighting applications, it is possible to realize highly efficient light emission.
- the overall efficiency may be reduced due to the low efficiency light emitting unit, but in the above organic EL element, the number of light emitting units is set as described above. Thus, the light emission efficiency is improved as compared to the prior art. In addition, it is possible to obtain an organic EL element having a long life and a small color shift, which is important in lighting applications.
- the first light emitting unit 1 a and the second light emitting unit 1 b are configured by the long wavelength light emitting unit 1 L
- the third light emitting unit 1 c is configured by the short wavelength light emitting unit 1 S. Therefore, the number of long wavelength light emitting units 1L is larger than the number of short wavelength light emitting units 1S.
- the arrangement of the long wavelength and the short wavelength in the light emitting unit 1 is not limited to this.
- the light emitting unit 1 of any one of the first light emitting unit 1a, the second light emitting unit 1b and the third light emitting unit 1c is composed of the short wavelength light emitting unit 1S, and the remaining two light emitting units 1 May be configured by the long wavelength light emitting unit 1L.
- the plurality of light emitting units 1 preferably include one or more light emitting units 1 including a plurality of light emitting materials.
- the light emitting unit 1 includes a plurality of light emitting materials, the light emitting properties of the respective light emitting materials can be compensated to emit light, so that the light emitting efficiency can be enhanced.
- light emission can be performed at a voltage lower than that when one light emitting material is used, or the light emitting property is not intentionally reduced for color adjustment. Get better.
- the number of light emitting units 1 including a plurality of light emitting materials may be one, two, or three or more.
- the number of types of light emitting materials is two.
- one light emitting material can be made to function mainly as a light emitting color
- the other light emitting material can be made to function as an aid for creating the light emitting color of the light emitting unit 1. Therefore, the luminescent color of the light emitting unit 1 can be easily adjusted, and the color adjustment of the whole can be easily performed.
- the number of light emitting units 1 including two types of light emitting materials may be one, two, or three or more. For example, in the example of FIG. 1, when the number of light emitting units 1 including two types of light emitting materials is two, it is preferable because design becomes easy and color adjustment becomes easy.
- the plurality of light emitting units 1 is an aspect preferably including a phosphorescent light emitting unit and a fluorescent light emitting unit.
- the phosphorescent light emitting unit is a light emitting unit 1 having a phosphorescent light emitting material.
- the fluorescent unit is a light emitting unit 1 having a fluorescent material.
- the first light emitting unit 1 a and the second light emitting unit 1 b can be configured by phosphorescent light emitting units.
- the third light emitting unit 1c can be configured by a fluorescent light emitting unit.
- the phosphorescent unit preferably contains only a phosphorescent material as a luminescent material.
- the fluorescent unit preferably contains only a fluorescent material as a light emitting material.
- the difference of the luminous efficiency and the life is seen by the difference of the fluorescence and the phosphorescence, and the light emitting material of all colors is unified by either the phosphorescence or the fluorescence to obtain high performance light emission It's not easy.
- a short wavelength light emitting material exhibiting a blue color
- its selection becomes difficult.
- a short wavelength fluorescent light emitting material generally has a property of having a long life but low luminous efficiency.
- it is difficult to obtain a phosphorescent light emitting material having a long life and a short wavelength though the light emitting efficiency of the phosphorescent light emitting material is high. Therefore, a multi-unit structure having a phosphorescent light emitting unit and a fluorescent light emitting unit is advantageous in terms of achieving both life and luminous efficiency.
- the long wavelength light emitting unit 1L is preferably configured of a phosphorescent light emitting unit. Thereby, the efficiency can be improved. In addition, the service life can be extended.
- the short wavelength light emitting unit 1S is preferably composed of a fluorescence light emitting unit. Thus, light emission can be obtained more efficiently with a long lifetime.
- the number of phosphorescent units is preferably greater than the number of fluorescent units. Thereby, the light emission efficiency can be further enhanced. As described above, when light emission of a short wavelength is obtained by a fluorescence light emission unit and light emission of a long wavelength is obtained by a phosphorescence light emission unit, it is possible to achieve both long life and high efficiency.
- the number of phosphorescence light emitting units may be three or more. Further, a plurality of fluorescent light emitting units may be provided such that the number of phosphorescent light emitting units is larger than the number of fluorescent light emitting units.
- the light emitting material is included in the light emitting layer 5 in the light emitting unit 1. Any appropriate light emitting material can be used as the light emitting layer 5. Examples of light emitting materials include red light emitting materials, green light emitting materials, blue light emitting materials, yellow light emitting materials, orange light emitting materials, and purple light emitting materials. These light emitting materials are classified according to the color exhibited by the light emitted upon light emission. Of course, light emitting materials of other colors may be used. When visible light is divided into red (R), green (G), and blue (B), red, green, and blue are in order from the long wavelength side. Thus, the red light emitting material tends to produce the long wavelength light emitting unit 1L.
- the blue light emitting material tends to create the short wavelength light emitting unit 1S.
- Green light emitting materials can be long wavelengths or short wavelengths.
- the light emitting unit 1 including both the red light emitting material and the green light emitting material tends to be the long wavelength light emitting unit 1L.
- the light emitting unit 1 including both the blue light emitting material and the green light emitting material tends to be the short wavelength light emitting unit 1S.
- the light emitting layer 5 in the light emitting unit 1 may be a single layer or multiple layers.
- the light emitting layer 5 may include only one light emitting material, or may include a plurality of light emitting materials. When a plurality of light emitting materials are included, the light emitting layer 5 may be configured as a mixed layer in which a plurality of light emitting materials are mixed in a single layer, or a stacked structure in which a plurality of layers including one light emitting material are stacked. Can.
- the long wavelength light emitting unit 1L for example, a single layer of red light emitting material, a single layer of green light emitting material, a layer of red light emitting material and a layer of green light emitting material as a light emitting material, red light emitting material and green light emitting material
- a structure such as a layer mixed with and can preferably be used.
- lamination of a red light emitting material layer and a blue light emitting material layer, a layer in which a red light emitting material and a blue light emitting material are mixed, a layer using a yellow light emitting material, orange light emission Layers using materials, etc. can be used.
- the weight average emission wavelength ⁇ S may be 550 nm or more as one whole long wavelength light emitting unit 1L.
- the short wavelength light emitting unit 1S for example, as a light emitting material, a single layer of blue light emitting material, a single layer of green light emitting material, lamination of a layer of blue light emitting material and a layer of green light emitting material, blue light emitting material and green light emitting material A structure such as a layer mixed with and can preferably be used.
- light emitting materials other than these may be used.
- the weight average emission wavelength ⁇ S may be less than 550 nm as one entire short wavelength light emitting unit 1S.
- the shape of the light emission spectrum and the weighted average light emission wavelength of the light emission unit 1 can also change strictly depending on optical interference, the refractive index of the substrate 6 used, the light extraction structure, the viewing angle, and the like.
- the weighted average emission wavelength of the light emitting unit 1 may be the weighted average emission wavelength of an element having a single unit structure in which the light emitting unit 1 is taken out to form an element. That is, the weighted average emission wavelength ⁇ S is obtained as follows. First, an emission spectrum in the front direction is obtained with a simple structure (a single unit structure laminated on a glass substrate, which does not include a concavo-convex structure for light extraction, etc.) that enables Fresnel analysis.
- this emission spectrum is divided by the frontal spectrum obtained when all the wavelengths have the same intensity with Fresnel analysis software capable of optical interference calculation. Further, the interference is canceled and the integrated average wavelength of the extracted spectrum is calculated. The wavelength calculated in this manner is the weighted average emission wavelength ⁇ S.
- the spectrum obtained in this manner is highly correlated with the unique spectrum of the light emitting material.
- the structure of the light emitting layer 5 is changed based on the organic EL element having the layer structure shown in FIG. 2 to design the organic EL element, and the above-mentioned structure is preferable, and a further preferable embodiment will be described.
- the organic EL element of FIG. 2 has a configuration in which the light diffusion layer 7 is removed from the organic EL element of FIG. 1, and other than that, it has the same layer configuration as the organic EL element of FIG. However, the emission wavelength of the light emitting layer 5 is appropriately changed.
- the same components as those in FIG. 1 are assigned the same reference numerals and descriptions thereof will be omitted. By omitting the light diffusion layer 7, the element can be simplified and a suitable design can be performed.
- the substrate 6 glass which is a light transmitting substrate was used.
- ITO was used as the light transmitting electrode 2
- Al was used as the light reflecting electrode 3.
- the materials can be changed as appropriate if the configuration requirements of each element are satisfied.
- an organic EL element was produced in which the first light emitting unit 1a and the second light emitting unit 1b were used as the long wavelength light emitting unit 1L, and the third light emitting unit 1c was used as the short wavelength light emitting unit 1S.
- the first light emitting unit 1a and the second light emitting unit 1b were configured by phosphorescent light emitting units
- the third light emitting unit 1c was configured by fluorescent light emitting units.
- the long wavelength light emitting unit 1L was configured by a phosphorescent light emitting unit
- the short wavelength light emitting unit 1S was configured by a fluorescent light emitting unit.
- Table 1 shows an outline of the light emitting material used for the design of the organic EL element.
- the first light emitting unit 1a is a unit containing only a green light emitting material
- the second light emitting unit 1b is a unit containing only a red light emitting material
- the third light emitting unit 1c is a unit containing only a blue light emitting material .
- the first light emitting unit 1a and the second light emitting unit 1b are a unit including a red light emitting material and a green light emitting material
- the third light emitting unit 1c is a unit including a blue light emitting material.
- the first light emitting unit 1a and the second light emitting unit 1b by changing the ratio of the light emitting materials of red and green, one light emitting material of red and green is made the main light emitting component, and the other light emitting material is made. It can be an auxiliary component.
- the color of the main light emitting component is mainly emitted.
- the auxiliary component has a function of assisting the light emission of the main light emission component.
- Comparative Example 1 two organic EL elements were designed for the light emitting unit 1.
- FIG. 3 shows the layer configuration of the organic EL element of Comparative Example 1 of the invention. About the same composition as FIG. 1, the same numerals are attached and explanation is omitted.
- the first light emitting unit 1a is a unit including a red light emitting material and a green light emitting material
- the second light emitting unit 1b is a unit including a blue light emitting material.
- the same light emitting material was used as the light emitting material. That is, the same red light emitting material, the same green light emitting material, and the same blue light emitting material were used. This makes it possible to make comparisons due to differences in layer configuration rather than light emitting materials.
- Table 2 shows an outline of each light emitting unit 1 in the element examples 1 and 2 and the comparative element example 1.
- EQE is the external quantum efficiency when each unit is evaluated alone.
- the weighted average emission wavelength ⁇ S is calculated for each unit.
- the weight average light emission wavelength can be varied in the range of 580 to 650 nm depending on the ratio of the red light emitting material to the green light emitting material. That is, the wavelength can be adjusted by the ratio of the red light emitting material to the green light emitting material. The same applies to the first light emitting unit 1a of the comparative element example 1.
- Table 3 shows the results of elements in which color adjustment was performed based on the element examples 1 and 2 and the comparative element example 1, changing the external quantum efficiency (EQE), changing the emission intensities of red and green.
- EQE is a value for each of red (R), green (G) and blue (B).
- whiteness is indicated as + when white is recognized, and white which is more white is indicated as ++.
- white which is more white is indicated as ++.
- ⁇ which describes what color is exhibited.
- FIG. 4 shows CIE chromaticity coordinates (CIE 1931 chromaticity coordinates).
- CIE 1931 chromaticity coordinates the horizontal axis is CIE-x, and the vertical axis is CIE-y.
- the positions of the color coordinates of the light emitted from each of the element examples and the comparison element examples are indicated by points.
- About (x, y) (0.35, 0.35) is about the center of the white region.
- color adjustment (adjustment of emission intensities of red and green) is performed so as to be in a white region.
- color adjustment (adjustment of emission intensities of red and green) is performed so that whiteness is further enhanced.
- the efficiency tends to be increased by setting the number of light emitting units 1 to three and the number of long wavelength light emitting units 1L more than the number of short wavelength light emitting units 1S. . It is considered that this is because the total quantum efficiency is apparently improved by providing two long wavelength light emitting units 1L as compared to the case where one long wavelength light emitting unit 1L is provided. Furthermore, the device example 2-2 in which a plurality of light emitting materials are included in one light emitting unit 1 has higher efficiency than the device example 1-1 in which a single light emitting material is used for each light emitting unit 1.
- the light emitting unit 1 including two types of light emitting materials (red and green), and being able to perform color adjustment without reducing the light emission efficiency of red or green. It is thought that it is because it can. That is, it can be said that light emission can be performed by sufficiently extracting the performance of each light emitting material.
- the ratio of the light emission intensity of red and green can be swung large.
- Element Example 2-1 shows that pink light emission is possible with a color slightly different from white.
- Element Example 2-3 shows that green-yellow light emission is possible with a color slightly deviated from white.
- white in lighting applications includes various whites. Yellowish white, reddish white, greenish white, and bluish white are included in white for lighting applications.
- White light refers to light containing light in the visible region.
- the white color of the organic EL element may have a color temperature of 1500 K or more and 10000 K or less. Candlelight colors are included in the white.
- the device examples 1 and 2 are merely examples, and the color reproduction range of the light emission color can be further expanded by adjusting the combination of the light emitting materials and the quantum efficiency.
- the color temperature of the luminescent color of the organic EL element is preferably one of 2500 K or less.
- Illumination having a color temperature of 2500 K or less is advantageous for use of an organic EL element.
- Luminescent colors with a color temperature of 2500 K or less are difficult to achieve with LEDs of inorganic materials, and even if they are achieved, their efficiency is very poor.
- wavelength conversion from blue to red is required in order to obtain an emission color of 2500 K or less, and the loss at that time is large.
- Colors with a color temperature of 2500 K or less are easy to give to people and are suitable for lighting applications.
- blue light which is often contained in light of high color temperature, suppresses the secretion of a hormone called melatonin that induces sleep, and adversely affects biological rhythm such as sleep disorder (circadian rhythm).
- melatonin a hormone that induces sleep
- a phenomenon called blue hazard has also been reported, which reaches the retina with high energy and stimulates to adversely affect the eye.
- light with a color temperature of 2500 K or less tends to settle down and can suppress adverse effects such as high color temperature. If you receive light with a color temperature of 2500 K or less before going to bed, you can easily get a good sleep. Lighting with a color temperature of 2500 K or less is useful for human health.
- the color temperature of the luminescent color of the organic EL element is preferably 1,500 K or more. By setting the color temperature to 1500 K or more, it is possible to obtain an emission color more suitable for lighting applications. From that point of view, the color temperature is more preferably 1800 K or more.
- the color temperature of the luminescent color of the organic EL element is preferably 2300 K or less, more preferably 2000 K or less.
- a more preferable aspect of the luminescent color of the organic EL element can be defined by the spectrum of light.
- the light quantity up to a wavelength of 600 to 700 nm is more preferably 5 times to 50 times the light quantity up to a wavelength of 400 to 500 nm.
- the former wavelength range is a red component
- the latter wavelength range is a blue component. Therefore, in this aspect, it can be said that the red component is more than the blue component. This makes it easier for the luminescent color to approach the candlelight color.
- the color rendering property is likely to be enhanced by the increase of the red component.
- the light quantity is determined by the integral value of the spectrum of light. The same applies to the following.
- the light quantity at a wavelength of 600 to 700 nm is more preferably 1.5 times to 5 times the light quantity at a wavelength of 500 to 600 nm.
- the former wavelength range is a red component
- the latter wavelength range is a green component. Therefore, in this aspect, it can be said that the red component is more than the green component. This makes it easier for the luminescent color to approach the candlelight color.
- the color rendering property is likely to be enhanced by the increase of the red component.
- the amount of light at a wavelength of 600 to 700 nm is 5 to 50 times the amount of light at a wavelength of 400 to 500 nm, and 1.5 to 5 times the amount of light at a wavelength of 500 to 600 nm It is further preferred that This makes it easier for the luminescent color to approach the candlelight color.
- the light quantity of wavelength 380 nm or less is preferably 0.001 times or less of the light quantity of wavelength 600 to 700 nm.
- the light of wavelength 380 nm or less is ultraviolet light. By reducing the amount of ultraviolet light, it is less likely to adversely affect the human body.
- the light quantity of wavelength 780 nm or more is preferably 0.01 times or less of the light quantity of wavelength 600 to 700 nm.
- the light of wavelength 780 nm or more is infrared light.
- Infrared light is absorbed by the skin and causes heat damage to the human body.
- the light of the candle contains much infrared light.
- the organic EL element can emit a light emitting color that is low in infrared light and has a color similar to that of a candle. Therefore, it is possible to effectively obtain excellent light emission for illumination that is unlikely to adversely affect the human body.
- the red component increases, and the candle-like emission color becomes easier to approach. It is further preferable to have the largest peak of the spectrum in the wavelength range of 600 to 700 nm. In addition, it may have a peak of the spectrum in the wavelength range of 500 to 600 nm. When the luminescent color contains a green component, the illumination can be enhanced.
- the luminescent color of the organic EL element be a candlelight color.
- the light of a candle is easy to give people peace.
- the color of candlelight tends to be less than 2500K.
- candles are difficult to use as lighting devices in modern times.
- the light of the candle contains much infrared light, if the light of the candle is reproduced as it is, the human body may be adversely affected.
- the organic EL element can safely obtain light of the same color as a candle.
- a candlelight-like luminescent color simulated to the luminescent color of a candle can be efficiently obtained.
- the candlelight color means that the color of the light emitted from the organic EL element is similar to the color of the light of the candle in human perception.
- the spectrum of the light of the organic EL element may be different from the spectrum of the light of the candle. In the organic EL element, light with less infrared light can be obtained with the same color as the light of the candle.
- Organic EL devices are advantageous over inorganic LEDs in that they can efficiently obtain light emission colors that give people peace of mind.
- Inorganic LEDs usually contain a large amount of blue components. Therefore, even if the color temperature is reduced by mixing colors or wavelength conversion, the blue component contained in the luminescent color suppresses the secretion of melatonin.
- the organic EL element it is easy to obtain light emission with little blue component. When the blue component is low, the action to suppress the secretion of melatonin is reduced.
- the organic EL element can obtain light with little ultraviolet light.
- the organic EL element can obtain a luminescent color that has a good influence on the human body both psychologically and physically.
- the number of light emitting units is preferably 3 to 7. As a result, both the color rendering properties represented by Ra and R9 tend to be high. Further, when the number of light emitting units is 7 or less, practicability is enhanced.
- Table 4 shows the evaluation results of the organic EL element in which the color temperature of the luminescent color is 2500 K or less.
- the element examples P1 to P5 are based on the organic EL element having the layer configuration of FIG. 2, and when the number of light emitting units 1 is increased, the light emitting unit 1 is interposed between the third light emitting unit 1c and the light transmitting electrode 2 It is configured to be added.
- the total number of light emitting units 1 is three.
- the total number of light emitting units is four in the element example P2, five in the element example P3, six in the element example P4, and seven in the element example P5.
- the light emitting unit 1 closest to the light transmitting electrode 2 is configured as a fluorescent light emitting unit containing a blue light emitting material.
- all the light emitting units 1 other than the light emitting unit 1 closest to the light transmitting electrode 2 have a phosphor having a light emitting layer containing a red light emitting material and a light emitting layer containing a green light emitting material It is configured as a light emitting unit.
- the film thickness of the light emitting layer is relatively thin such as several hundreds nm, and is very close to the wavelength of light (wavelength propagating in the medium), so thin film interference occurs inside the organic EL element.
- the internal light emission interferes with the film thickness of the organic layer, and the intensity of the emitted light greatly increases and decreases.
- light (direct light) directly from the light emitting layer to the light extraction side and light reflected from the light emitting layer after going from the light emitting layer to the reflective electrode are then taken out. Interference with light going to the side (reflected light) interferes and strengthens each other.
- the optical film thickness (optical distance) derived by multiplying the refractive index n by the film thickness d between the light emission source and the surface of the reflective layer is 1 / 4 ⁇ of the wavelength ⁇ of light. It is designed to be approximately equal to the odd multiple. Thereby, the component amount of light emitted from the substrate in the front direction becomes the maximum value. It is a so-called cavity design. This method does not mean that the light is amplified internally, but it means changing the direction of the light and intensifying the light in a specific direction, for example, the front direction that is likely to extract the light into the atmosphere. .
- phase shift of light does not become ⁇ , and refraction and extinction in the organic layer and the reflection layer become involved, and more complicated behavior is exhibited.
- the phase shift of light at this time can be expressed as ⁇ .
- the element In the organic EL element, the element can be designed using this phase shift ⁇ .
- phase shift ⁇ ( ⁇ S ) at the weighted average emission wavelength ⁇ S is expressed by the following equation (4).
- n 1 and k 1 represent the refractive index and extinction coefficient of the layer in contact with the light reflection layer, respectively
- n 2 and k 2 represent the refractive index and extinction coefficient of the light reflection layer, respectively 1 , n 2 , k 1 and k 2 are functions of ⁇ S.
- the light reflection layer is formed of the light reflective electrode 3.
- phase shift ⁇ ( ⁇ S ) a cavity condition in which the interference becomes stronger in the light emitting layer 5 of the L-th light emitting unit 1 from the light reflective electrode 3 is considered.
- a position at an odd multiple of 1 ⁇ 4 ⁇ of the wavelength ⁇ of light is preferable. Therefore, the ideal position where the cavity effect can be obtained can be expressed by the following equation using the weighted average emission wavelength ⁇ S.
- n ( ⁇ S) is at the wavelength lambda S, the average refractive index of the medium filling the space between the light reflecting electrode 3 to the light emitting layer 5.
- d L is a distance between the light reflective electrode 3 and the light emitting layer 5. This distance represents a physical distance. It can be said that the product of the refractive index and the physical distance, that is, the above equation (6) represents an optical distance. Also, it can be said that m indicates the order of the cavity.
- the average refractive index of the medium in the layer constituting the organic EL element is determined by the following formula (7).
- d represents the thickness of the individual layers constituting the medium
- n represents the refractive index of the individual layers constituting the medium
- m is an integer of 1 or more and indicates a number sequentially given to each layer. That is, d, n and m in this formula have nothing to do with other formulas.
- the average refractive index of the medium can be said to be the average value of the refractive index of the medium at the weighted average emission wavelength ⁇ S of the spectrum of the light emitting material. In other words, it is the average value of the refractive index weighted by the thickness.
- the organic EL element can be designed by focusing on the distance from the light emitting position to the light reflective electrode 3 in consideration of the principle of interference. Since the emission spectrum obtained from the light emitting layer 5 has a certain width, the order of the cavity, that is, the order of the interference should be as small as possible. This is because as the order of the cavity increases, the shift between the short wavelength and the long wavelength of the spectrum increases, which makes it difficult to obtain an enhancing effect by interference, which may cause a decrease in efficiency and a decrease in viewing angle characteristics.
- the optical path length changes according to the viewing angle, that is, the advancing angle of light. Therefore, it is preferable to perform cavity design in consideration of them. Specifically, it is preferable to correct the above equation (5) which is the cavity condition of light emitted toward the front.
- the organic EL element it is preferable to keep all the light emitting layers 5 within the secondary cavity conditions. It is because light extraction property can be improved by containing in a cavity of lower order. And, in consideration of light from an oblique direction, it is preferable to deviate from the preferred cavity design in the frontal direction. At that time, it is preferable to shift within a range in which the coefficient 0.5 before ⁇ S in the above equation (5) is further increased by about 0.25 in consideration of interference of light in the oblique direction.
- the distance d F between the light-emitting layer 5 of the light-emitting unit 1 farthest from the light-reflecting electrode 3 and the light-reflecting electrode 3 satisfy the conditions of the following formulas (2) and (3) .
- all the light emitting layers 5 are contained in the secondary cavity, and the effect of enhancing light by interference is enhanced, so that the light extraction efficiency can be improved.
- ⁇ ( ⁇ S ) is a phase shift that occurs in the light reflective electrode 3.
- n ( ⁇ S ) is the average refractive index of the medium at the wavelength ⁇ S that fills the space from the light reflective electrode 3 to the light emitting layer 5.
- ⁇ ( ⁇ S ) and n ( ⁇ S ) indicate values at the weighted average emission wavelength ⁇ S.
- the distance d F between the light-emitting layer 5 of the light-emitting unit 1 farthest from the light-reflecting electrode 3 and the light-reflecting electrode 3 satisfies the conditions of equations (2) and (3). Is preferred.
- the light emitting layer 5 farthest from the light reflective electrode 3 can be disposed closer to the light reflective electrode 3, so that the light extraction property can be further improved.
- the light emitting layer 5 is based on the position of the center of its thickness and is light reflective.
- the electrode 3 is based on the surface on the light emitting layer 5 side.
- the center of the thickness of the multiple light emitting layer 5 is used as a reference. That is, the distance d can be more accurately referred to as the distance from the surface of the light reflective electrode 3 on the light emitting layer 5 side to the thickness center of the light emitting layer 5.
- Reference to the surface of the light reflective electrode 3 will be understood from the fact that light is reflected on the surface of the reflective layer.
- the light emitting layer 5 be strictly a light emitting center which is a recombination point of electrons and holes, the recombination point can be changed depending on the characteristics of the material or the device.
- the thickness of the light-emitting layer 5 is often thin as a proportion of the whole, so the reference position may be considered as the center of the light-emitting layer 5.
- the light emission center may be used as a reference for the distance d.
- the luminescent center may be a surface (a surface on the light reflective electrode 3 side or a surface on the light transmissive electrode 2 side) or a layer interface (layers of the light emitting layer 5 of multiple layers) Interface with) and so on.
- the light emitting unit 1 closest to the light reflective electrode 3 is preferably composed of the short wavelength light emitting unit 1S.
- Light of short wavelength is easily affected by interference, and by arranging the short wavelength light emitting unit 1S near the light reflecting layer, more light of the short wavelength light emitting unit 1S can be extracted. Therefore, the light extraction can be enhanced.
- the light reflective electrode 3 constitutes a cathode
- the short wavelength light emitting unit 1S is the light emitting unit 1 closest to the cathode, and the electron injection property can be improved. Therefore, an element that can be driven at a lower voltage can be configured.
- the plurality of light emitting units 1 are arranged in the order of the light emitting unit 1 including a green light emitting material, the light emitting unit 1 including a blue light emitting material, and the light emitting unit 1 including a red light emitting material from the light reflective electrode 3 side. Is a preferred embodiment.
- the light can be extracted more easily, so that the light extraction can be further improved. This is because when the short wavelength material is disposed near the light reflective electrode 3, preferable conditions for interference can be easily set.
- the three light emitting layers 5 can be easily accommodated in the secondary cavity, the light extraction efficiency can be easily improved.
- a plurality of light emitting units 1 are arranged in the order of the light emitting unit 1 including a blue light emitting material, the light emitting unit 1 including a red light emitting material, and the light emitting unit 1 including a green light emitting material from the light reflective electrode 3 side.
- the light can be extracted more easily, so that the light extraction can be further improved. This is because when the short wavelength material is disposed near the light reflective electrode 3, preferable conditions for interference can be easily set.
- the three light emitting layers 5 can be easily accommodated in the secondary cavity, the light extraction efficiency can be easily improved.
- a device example 2A was produced based on the device example 2-2 described above. Moreover, the element which changed the structure of the light emission unit 1 from the element example 2 as element example 3 and 4 was designed.
- Table 5 shows an outline of the element configuration.
- the first light emitting layer 5a is disposed in the vicinity of the primary cavity
- the second light emitting layer 5b is disposed in the vicinity of the secondary cavity
- the third light emitting layer 5c is the third in the device example 2A. It was arranged around the cavity.
- the first light emitting layer 5a is arranged around the primary cavity
- the second light emitting layer 5b is arranged around the secondary cavity
- the third light emitting layer 5c is arranged around the secondary cavity.
- the first light emitting layer 5a is arranged around the primary cavity
- the second light emitting layer 5b is arranged around the primary cavity
- the third light emitting layer 5c is arranged around the secondary cavity.
- the viewing angle characteristics of the organic EL element are expressed using a color difference ( ⁇ u′v ′).
- This ⁇ u′v ′ is the root mean square ( ⁇ u ′ ⁇ 2 + ⁇ v ′ ⁇ 2) ⁇ (1/2) of the amount by which the u′v ′ coordinate of the chromaticity deviates from the average value in the range of the viewing angle of 80 ° from the front. Means the maximum value of).
- ⁇ is a symbol indicating a multiplier.
- the range of .DELTA.u'v ' is the entire element in the case of including the light diffusion layer 7 or the like, and in a simplified system, the lower the better. Therefore, the viewing angle characteristics were also evaluated.
- Table 6 shows the results of comparing the characteristics of the device examples 2A, 3 and 4 produced. From Table 6, an element in which the third light emitting unit 1c is designed under the condition of the secondary cavity periphery than the element example 2A in which the third light emitting unit 1c farthest from the light reflective electrode 3 is the condition around the tertiary cavity In Examples 3 and 4, it was confirmed that both the efficiency and the viewing angle characteristics were improved.
- the light emitting unit 1 including a green light emitting material, the light emitting unit 1 including a blue light emitting material, and the light emitting unit 1 including a red light emitting material are arranged in this order from the light reflective electrode 3 side. And it was confirmed that the viewing angle characteristics are excellent.
- a green light emitting material is a main component
- a red light emitting material is a main component
- the light emitting unit 1 including the blue light emitting material is disposed in the first light emitting unit 1a, and the light intensity of the short wavelength is increased and the color temperature is relatively compared to the other device examples. It was confirmed that high luminescent color could be obtained.
- a red light emitting material is a main component
- a green light emitting material is a main component.
- the relational expression of the distance d F that is preferably satisfied by the light emitting layer 5 of the light emitting unit 1 farthest from the light reflective electrode 3 can be expressed as in the following formula (8) from the formulas (2) and (3) .
- the preferable condition of the distance d F is a function of the wavelength ⁇ S.
- the organic EL element it is possible to optimize the position of the light emitting layer 5 of the light emitting unit 1 farthest from the light reflective electrode 3 using the above-mentioned relational expression.
- FIG. 5 is a graph showing the relationship between the wavelength ⁇ S and the distance d F in the light emitting layer 5 (third light emitting layer 5 c) of the light emitting unit 1 farthest from the light reflective electrode 3.
- the preferable value of the distance d F can be changed depending on the material of the light reflective electrode 3 and the refractive index of the organic material.
- the light reflective electrode 3 (cathode) is Ag.
- the refractive index of the medium is about 1.8 to 1.9 although it varies depending on the wavelength. Even if these matters are taken into consideration, the influence of these matters on the light extraction property is small compared to the design of the distance d F , so the light extraction property can be improved by satisfying the relationship of the equation (8). It is possible.
- the relationship represented by this graph can be used for the arrangement of the light emitting layer 5 of the light emitting unit 1 farthest from the light reflective electrode 3.
- the light interference action in consideration of the light in the oblique direction is used. Therefore, the light emitted to the outside can be efficiently increased. Further, since light in oblique directions is taken into consideration, it is possible to suppress the difference in color caused by the viewing angle. As a result, it is possible to obtain an organic EL element having a high light extraction efficiency and an excellent light emission characteristic in which the viewing angle dependency is suppressed.
- the interference design can be performed in consideration of the deviation from the cavity design in the front direction.
- the factor a is introduced as an index that represents the deviation from the cavity design in the front direction.
- the equation of the cavity design using the factor a can be expressed by the following equations (9) and (10) by modifying the equation (5).
- m is an integer of 1 or more.
- n ( ⁇ S ) is the average refractive index of the medium that fills the space between the light reflective electrode 3 and the light emitting layer 5 of the Lth light emitting unit 1 from the light reflective electrode 3 at the wavelength ⁇ S.
- d L is a distance between the light reflective electrode 3 and the light emitting layer 5 of the Lth light emitting unit 1 from the light reflective electrode 3.
- the factor a is expressed as a L because it represents that it is the factor a of the light emitting layer 5 of the L-th light emitting unit 1 from the light reflective electrode 3.
- Factor a in the first light-emitting unit 1a is represented as a 1.
- Factor a in the second light-emitting unit 1b is expressed as a 2.
- Factor a in the third light emitting unit 1c is expressed as a 3.
- the factor a can usually be expressed as a value of 0 or more and 0.5 or less. That is, the factor a has a relationship of 0 ⁇ a ⁇ 0.5.
- the condition that a is equal to or greater than 0.5 is for the cavity design of the next order. That is, the number of m is increased by one and considered.
- a can be, for example, 0.01 or more, and more preferably, 0.03 or more.
- This condition is a condition in which the optimum cavity condition in the front direction is corrected in consideration of the fact that the peak of the light amount is obtained in the 45 ° direction.
- the factor a is preferably a ⁇ 0.25, more preferably a ⁇ 0.2.
- the factor a is preferably a ⁇ 0.35, more preferably a ⁇ ⁇ ⁇ 0.4.
- Cavity design using factor a can be used when it is desired to enhance the color rendering of the organic EL element.
- a plurality of light emitting units 1 includes at least two or more light emitting units 1 including the same light emitting material, it is possible to perform design using factor a.
- the green light emitting material used in the first light emitting unit 1a and the green light emitting material used in the second light emitting unit 1b are the same green light emitting material.
- the red light emitting material used in the first light emitting unit 1a and the red light emitting material used in the second light emitting unit 1b are the same red light emitting material. Therefore, it is possible to improve the color rendering using factor a.
- the design of color rendering will be described below.
- the first light emitting unit 1 a which is the light emitting unit 1 closest to the light reflective electrode 3 and the second light emitting unit 1 b disposed adjacent to the first light emitting unit 1 a.
- the relationship between the first light emitting unit 1a and the second light emitting unit 1b will be described, the relationship between the first light emitting unit 1a and the third light emitting unit 1c and / or the second light emitting unit 1b and the third light emission It is applicable also in relation to unit 1c.
- the first light emitting unit 1a utilizes a primary cavity
- the second light emitting unit 1b utilizes a secondary cavity.
- the formula of the cavity design using the factor a can be expressed by the following formulas (11) and (12).
- n ( ⁇ S ) is the average refractive index of the medium that fills between the light reflective electrode 3 and the light reflective electrode 3 to the light emitting layer 5 of the first light emitting unit 1 a at the wavelength ⁇ S .
- d 1 is the distance between the light reflective electrode 3 and the light emitting layer 5 of the first light emitting unit 1 a from the light reflective electrode 3.
- a 1 is a factor a in the light emitting layer 5 of the first light emitting unit 1 a.
- the formula of the cavity design using the factor a can be expressed by the following formulas (13) and (14).
- n ( ⁇ S ) is the average refractive index of the medium that fills the space between the light reflective electrode 3 and the light reflective electrode 3 to the light emitting layer 5 of the second light emitting unit 1 b at the wavelength ⁇ S .
- d 2 is the light reflective electrode 3, the distance between the light reflective electrode 3 and the light-emitting layer 5 of the second light-emitting unit 1b.
- a 2 is a factor a in the light emitting layer 5 of the second light-emitting unit 1b.
- the values of the factor a be slightly different in the plurality of light emitting units 1 containing the same light emitting material.
- the interference condition is deviated, and the emission spectrum of the extracted light becomes slightly different. Then, since the valley of the wavelength of the light taken out as a whole can be filled, the color rendering can be improved.
- the deviation of the factor a can be expressed as the absolute value
- ⁇ a a 2 -a 1 .
- the wavelength of the light extracted from the first light emitting unit 1a and the wavelength of the light extracted from the second light emitting unit 1b mutually compensate to fill the valley of the spectrum, so the color rendering property is effective. Can be enhanced. That is, the peak of the spectrum in which the intensity of the light emitting material is increased due to the interference is slightly shifted by the light emitting unit 1. Therefore, in the entire emission spectrum, the design is such that the valley of the wavelength is filled. As a result, it is possible to obtain an emission spectrum in which the valleys are reduced, and it is possible to obtain emission with high color rendering.
- the effect of color rendering can be obtained higher.
- the weighted average emission wavelength ⁇ S of the light emitting unit 1 is obtained when it is made into a single unit, and the wavelengths of light when actually taken out may be different.
- both factors a satisfy 0 ⁇ a ⁇ 0.2. That is, in the relationship between the first light emitting unit 1a and the second light emitting unit 1b, 0 ⁇ a 1 ⁇ 0.2 and 0 ⁇ a 2 ⁇ 0.2. Thereby, color rendering can be improved more efficiently.
- both factors a satisfy 0.4 ⁇ a ⁇ 0.5 in consideration of the difference between the factors a. That is, in the relationship between the first light emitting unit 1a and the second light emitting unit 1b, 0.4 ⁇ a 1 ⁇ 0.5 and 0.4 ⁇ a 2 ⁇ 0.5. Thereby, color rendering can be improved more efficiently.
- of the difference of the factor a is 0.15 or less.
- the same light emitting material may be any of a red light emitting material, a green light emitting material, and a blue light emitting material.
- the same light emitting material is preferably a green light emitting material, which is one embodiment. Since green has high visibility, it is possible to enhance the light emitting property of the high visibility region. The overall color rendering can be improved.
- the same light-emitting material is preferably a red light-emitting material, which is a preferred embodiment. Since red has a large effect on color rendering properties, light emitting properties in a region having a large effect of color rendering Can improve the overall color rendering.
- two or more light emitting units 1 in which the red light emitting material and the green light emitting material are the same are provided.
- color rendering can be further improved.
- the weighted average emission wavelength of the light emitting unit 1 be the same.
- the distance between the light reflective electrode 3 (cathode) and the light emitting layer 5 was changed to produce element examples 5-1, 5-2, and 5-3.
- the position of the third light emitting layer 5c is fixed, and the positions of the first light emitting layer 5a and the second light emitting layer 5b are adjusted.
- conditions in which light is reinforced due to interference are considered.
- adjustment was made to make the valleys of the spectrum smaller, and the color rendering index Ra, which is an index of color rendering in an organic EL element, was evaluated.
- Table 7 shows the results of evaluation of the element example 2A and the element examples 5-1, 5-2, and 5-3.
- the difference of the factor a between the first light emitting unit 1a and the second light emitting unit 1b having the same light emitting material (red light emitting material and green light emitting material) (A 2 -a 1 ) is 0.05 or more in absolute value. Then, it was confirmed that Ra is increased due to peak deviation, and the color rendering property is improved.
- FIG. 6 is a graph showing the relationship between the factor a and the wavelength ⁇ S in the light emitting unit 1 including the red light emitting material and the green light emitting material.
- the weighted average emission wavelength ⁇ S of the light emitting unit 1 is determined without excluding the interference.
- the factor a becomes 0.05 or more
- the wavelength ⁇ S shifts to the long wavelength side. That is, the wavelength of the extracted light is increased. Therefore, the difference of the wavelengths ⁇ S tends to be large, and the color rendering can be more enhanced.
- wavelength (lambda) S in the 1st light emission unit 1a and the 2nd light emission unit 1b is 610 nm in wavelength, and is the same. This is because the interference condition is eliminated as much as possible, and the wavelength is obtained in a single unit. Therefore, in the multi-unit element, the actually extracted wavelength is slightly shifted by the above design.
- the difference of the factor a is preferably 0.05 or more.
- the difference of the factor a is set, an increase in intensity occurs due to interference, and while the same light emitting material is used, the valley of the spectrum can be further reduced to efficiently improve the color rendering.
- FIG. 7 is a graph showing an example of the absorption spectrum of the organic material.
- FIG. 7 is composed of FIGS. 7A and 7B.
- FIG. 7A is an overall view
- FIG. 7B is an enlarged view.
- FIG. 7 shows the wavelength dependency of the absorption spectrum obtained from the transmission and reflection spectra of the organic material used in the device example 2.
- FIG. 7A shows a wavelength of 300 to 800 nm
- FIG. 7B shows a pickup of a wavelength of 400 to 700 nm in FIG. 7A.
- the absorption in the short wavelength region is large.
- the dopant of the long wavelength material has a property of slightly absorbing the short wavelength light and emitting the light of the above wavelength. Therefore, as the number of long wavelength light emitting units 1L is increased, the relative long wavelength components become larger and the light extraction efficiency is further amplified.
- FIG. 8 shows an example of the relationship between the light emission angle and the light quantity distribution.
- FIG. 8 is composed of FIGS. 8A and 8B.
- FIG. 8A shows a light distribution pattern.
- FIG. 8B is a graph of radiant flux ratio.
- the light amount in each angle is drawn as a distance from the center, with the light in the front direction as the center and the light amount in each angle being drawn.
- the horizontal axis indicates the emission angle
- the vertical axis indicates the relative amount of light (radiant flux ratio).
- the base indicates the intensity of light from which the interference condition has been removed.
- the light extraction structure can be configured by the light diffusion layer 7 provided between the substrate 6 and the light transmitting electrode 2.
- the light diffusion layer 7 is an internal extraction structure. In the internal extraction structure, light can be efficiently extracted by suppressing total reflection on the substrate 6.
- the light extraction structure on the outer side may be provided on the outside of the substrate 6 (the side opposite to the light transmitting electrode 2).
- the light extraction structure on the outer side can be composed of a light scattering film or the like. A more preferable configuration of the light diffusion layer 7 will be described later.
- the material which comprises an organic EL element is demonstrated.
- the organic EL element may be formed of any appropriate material that is usually used to manufacture an organic EL element.
- a glass substrate can be used as the substrate 6. Soda glass can be used as the glass. Although alkali-free glass may be used, soda glass is generally inexpensive and advantageous in cost. In the case where the light diffusion layer 7 is provided, even if soda glass is used, since the light diffusion layer 7 is present as a base layer of the organic layer, the effect of alkali diffusion to the light transmission electrode 2 such as ITO can be obtained. It can be suppressed.
- the light diffusion layer 7 can be formed, for example, of a thin film obtained by blending scattering particles in a base material and applying the mixture.
- the refractive index of the base material of the light diffusion layer 7 should be as high as possible, and is preferably equal to or higher than the organic material used for the organic EL element.
- the material which does not absorb light as much as possible is preferable.
- Resin can be used as a base material.
- the refractive index may be increased by mixing a high refractive index inorganic material such as TiO 2 with the base material.
- a short circuit is likely to occur.
- the scattering particles are not particularly limited as long as the scattering particles exhibit the function of diffusing light together with the base material, but it is preferable that the scattering particles do not absorb light.
- the light diffusion layer 7 can be formed by applying the material of the light diffusion layer 7 to the surface of the substrate 6. The material may be applied by spin coating, or coating methods such as slit coating, bar coating, spray coating, or inkjet may be used depending on the application, substrate size, and the like. A preferred form of the light diffusion layer 7 will be described later.
- the organic light emitting laminate has a structure in which an organic EL layer is formed between an anode and a cathode.
- the organic EL layer is defined as a layer between the anode and the cathode.
- the organic EL layer has a plurality of light emitting units 1.
- the light emitting unit 1 can be configured to include, for example, a hole transport layer, a light emitting layer 5, an electron transport layer, and an electron injection layer from the anode side.
- the light transmissive electrode 2 can be configured as an anode
- the light reflective electrode 3 can be configured as a cathode.
- the anode is an electrode for injecting holes, and it is preferable to use an electrode material composed of a metal having a large work function, an alloy, an electroconductive compound, or a mixture thereof, and having a HOMO (Highest Occupied Molecular Orbital) level It is preferable to use one having a work function of 4 eV or more and 6 eV or less so that the difference between
- the electrode material of the anode is, for example, a metal oxide such as ITO, tin oxide, zinc oxide or IZO, a metal compound such as copper iodide, a conductive polymer such as PEDOT or polyaniline, or any acceptor. Examples thereof include conductive light transmitting materials such as conductive polymers and carbon nanotubes.
- the anode may be formed on the surface of the light diffusion layer 7 provided on the substrate 6 as a thin film by a sputtering method, a vacuum evaporation method, a coating method, or the like.
- the sheet resistance of the anode is preferably several hundreds ⁇ / sq or less, particularly preferably 100 ⁇ / sq or less.
- the film thickness of the anode is set to 500 nm or less, preferably 10 to 200 nm. The thinner the anode, the better the light transmittance, but the sheet resistance increases in inverse proportion to the film thickness. Therefore, when the area of the organic EL element is increased, the voltage is increased and the uniformity of luminance uniformity is not uniform. (Due to uneven current density distribution due to voltage drop).
- auxiliary wiring such as metal on the transparent anode.
- a material excellent in conductivity is desirable, and Ag, Cu, Au, Al, Rh, Ru, Ni, Mo, Cr, Pd or the like or an alloy of these, for example, MoAlMo, AlMo, AgPdCu or the like may be used.
- MoAlMo, AlMo, AgPdCu or the like may be used.
- a metal having a high reflectance as much as possible.
- ITO Indium Tin Oxide
- the crystallization improves the conductivity and relaxes the trade-off conditions. Further, since the structure becomes dense, the effect of suppressing the transfer of outgassing (such as water) generated when a resin is used for the light diffusion layer 7 to the organic EL layer is also expected.
- the material used for the hole injection layer can be formed using a hole injection organic material, a metal oxide, a so-called acceptor organic material or inorganic material, a p-doped layer or the like.
- the hole-injecting organic material is, for example, a material having a hole-transporting property, a work function of about 5.0 to 6.0 eV, and a strong adhesion to the anode.
- CuPc, starburst amine, etc. are examples thereof.
- the hole-injectable metal oxide is, for example, a metal oxide containing any of molybdenum, rhenium, tungsten, vanadium, zinc, indium, tin, gallium, titanium, and aluminum.
- oxides of a plurality of metals other than the oxides of only one metal such as indium and tin, indium and zinc, aluminum and gallium, gallium and zinc, titanium and niobium, etc.
- the hole injection layer made of these materials may be formed by a dry process such as evaporation or transfer, or formed by a wet process such as spin coating, spray coating, die coating, or gravure printing. It may be a membrane.
- the material used for the hole transport layer can be selected, for example, from the group of compounds having a hole transportability.
- the compound of this type include 4,4′-bis [N- (naphthyl) -N-phenyl-amino] biphenyl ( ⁇ -NPD), N, N′-bis (3-methylphenyl)-(1 1,1′-biphenyl) -4,4′-diamine (TPD), 2-TNATA, 4,4 ′, 4 ′ ′-tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (MTDATA)
- CBP 4,4′-N, N′-dicarbazole biphenyl
- any material known as a material for an organic EL element can be used.
- a light emitting material selected from among these compounds it is also preferable to appropriately mix and use a light emitting material selected from among these compounds.
- a light emitting material selected from among these compounds not only compounds that produce fluorescence, as typified by the above compounds, but also material systems that emit light from spin multiplets, such as phosphorescent materials that produce phosphorescence, and a site made of them in a part of the molecule Compounds can also be suitably used.
- the light emitting layer 5 made of these materials may be deposited by a dry process such as vapor deposition or transfer, or may be deposited by a wet process such as spin coating, spray coating, die coating or gravure printing. It may be a membrane.
- the intermediate layer 4 can be formed of a material capable of generating a charge for each light emitting unit 1. In order to extract light, it is preferable to have light transparency.
- the intermediate layer 4 can be formed of a metal thin film. Silver, aluminum, etc. are illustrated.
- the intermediate layer 4 may be configured using an organic material.
- the intermediate layer 4 can also be configured by a metal oxide layer.
- the intermediate layer 4 can be made of ITO or the like.
- the material used for the electron transport layer can be selected from the group of compounds having an electron transport property.
- this type of compound include metal complexes known as electron transporting materials such as Alq 3 and compounds having a heterocycle such as phenanthroline derivatives, pyridine derivatives, tetrazine derivatives, oxadiazole derivatives, etc. Rather, it is possible to use any of the commonly known electron transport materials.
- the material of the electron injection layer is, for example, metal fluorides such as lithium fluoride and magnesium fluoride, metal halides such as metal chlorides represented by sodium chloride and magnesium chloride, aluminum, cobalt, zirconium, titanium, Oxides, nitrides, carbides, oxynitrides, etc.
- insulators such as magnesium, iron oxide, aluminum nitride, silicon nitride, silicon carbide, silicon oxynitride, boron nitride, etc., silicon compounds such as SiO 2 and SiO, carbon compounds, etc. It can be used. These materials can be formed into thin films by vacuum evaporation, sputtering, or the like.
- the cathode is an electrode for injecting electrons into the light emitting layer, and it is preferable to use an electrode material composed of a metal, an alloy, an electrically conductive compound having a small work function, and a mixture thereof, and LUMO (Lowest Unoccupied Molecular Orbital) It is preferable to use one having a work function of 1.9 eV or more and 5 eV or less so that the difference with the level does not become too large.
- an electrode material of the cathode for example, aluminum, silver, magnesium and the like, and alloys of these with other metals, such as magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy can be mentioned as an example.
- metal conductive materials, metal oxides, etc., and mixtures of these with other metals for example, an extremely thin film composed of aluminum oxide (here, a thin film of 1 nm or less capable of flowing electrons by tunnel injection) A laminated film with a thin film made of aluminum can also be used.
- the organic light emitting laminate is preferably sealed by a sealing material.
- the organic EL layer is weak to water and the like, and in order to avoid contact with air, the organic EL layer side of the substrate 6 is sealed using cap glass or the like in a glove box under dew point management (eg -70 ° C. or less).
- dew point management eg -70 ° C. or less.
- the above organic EL element has three or more light emitting units 1, so the total thickness of the organic light emitting laminate tends to be larger than that of a single unit or a double unit. Therefore, further effects can be obtained.
- the current density can be reduced, and the sheet resistance value required for driving can be relaxed. That is, driving is possible even if the sheet resistance value is relatively high. Therefore, element design is facilitated, and light extraction efficiency can be enhanced.
- the sheet resistance value required for driving can be relaxed similarly to the increase in area (the increase in light emitting area).
- the thickness of the organic light emitting laminate is increased, resistance to a short circuit due to a foreign matter can be enhanced. This is because the thickness of the laminated structure is increased and the distance between the electrodes is increased, so that it is difficult to make the leak path of the current through the foreign matter. Therefore, the reliability of the organic EL element can be improved.
- the organic EL element of FIG. 1 has a light diffusion layer 7.
- the light diffusion layer 7 preferably includes the first transparent material layer 7 a and the second transparent material layer 7 b from the substrate 6 side. Thereby, the concavo-convex structure 10 can be easily formed at the interface between the two layers.
- the second transparent material layer 7 b preferably has a refractive index larger than that of the substrate 6. Thereby, the refractive index difference can be reduced to further enhance the light extraction efficiency. It is preferable that the concavo-convex structure 10 be formed at the interface between the first transparent material layer 7a and the second transparent material layer 7b. Light is diffused by the concavo-convex structure 10 by the light diffusion layer 7 having a multilayer structure having the concavo-convex structure 10 at such an interface, so that the light extraction property can be further enhanced.
- the second transparent material layer 7b functions as a covering layer to flatten the uneven structure 10, so that the light emitting laminate can be stabilized. It can be provided. Therefore, the disconnection defect and the short defect resulting from the unevenness can be suppressed. Further, when the covering layer is provided, even when the uneven structure 10 having a large height (depth) is provided, the light emitting laminate can be favorably laminated. Thus, the second transparent material layer 7b can function as a planarization layer and is preferable. In addition, since the two transparent material layers are transparent and light transmissive, light can be effectively extracted.
- the second transparent material layer 7 b preferably has a refractive index of 1.75 or more in the visible light wavelength region. Thereby, the refractive index difference can be further reduced, the total reflection loss can be suppressed at a wide angle, and more light can be extracted.
- the refractive index of the substrate 6 is, for example, in the range of 1.3 to 1.55.
- the upper limit of the refractive index of the second transparent material layer 7b is not particularly limited, and may be, for example, 2.2 or 2.0. Further, it is preferable to reduce the difference in refractive index between the light transmitting electrode 2 which is an adjacent layer. For example, this refractive index difference can be made 1.0 or less.
- the first transparent material layer 7a preferably has a refractive index in the visible light wavelength range of 1.3 to 1.5. Thereby, more light can be extracted.
- the difference in refractive index between the first transparent material layer 7a and the substrate 6 should be small. For example, this refractive index difference can be made 1.0 or less. It is also preferable that the refractive index of the first transparent material layer 7 a be smaller than the refractive index of the substrate 6. In that case, total reflection at the interface between the first transparent material layer 7 a and the substrate 6 can be suppressed.
- the first transparent material layer 7 a may have a refractive index higher than that of the substrate 6.
- the light transmittance of the first transparent material layer 7a should be high.
- the first transparent material layer 7a may have a transmittance of 80% or more, preferably 90% or more of visible light.
- the light diffusion layer 7 can configure, for example, the first transparent material layer 7a as a low refractive index layer and the second transparent material layer 7b as a high refractive index layer.
- the level of the refractive index may be relative to the transparent material layers.
- the light diffusion layer 7 (the first transparent material layer 7a and the second transparent material layer 7b) is preferably formed of a resin.
- the refractive index can be easily adjusted, and the formation of the asperities and the flattening of the asperities can be easily performed.
- a resin material is used, one having a relatively high refractive index can be easily obtained.
- the resin can form a layer by application, it is possible to more easily form a layer having a flat surface by allowing the resin to enter the recess.
- the 1st transparent material layer 7a As a material used for the 1st transparent material layer 7a, organic resin, such as an acryl type and an epoxy type, is illustrated. In addition, additives for curing the resin (curing agent, curing accelerator, curing initiator, etc.) may be added to the resin.
- inorganic materials are illustrated as materials other than resin. For example, spin-on glass can be used to form the first transparent material layer 7a.
- Examples of the material of the second transparent material layer 7 b include resins in which high refractive index nanoparticles such as TiO 2 are dispersed.
- the resin may be an organic resin such as an acrylic resin or an epoxy resin.
- additives for curing the resin (curing agent, curing accelerator, curing initiator, etc.) may be added to the resin.
- the material other than the resin such as an inorganic film and composed of SiN, such as a membrane of an inorganic oxide (such as SiO 2) are exemplified.
- the surface (the surface on the side of the light transmitting electrode 2) of the light diffusion layer 7 formed by the coating of the second transparent material layer 7b is a flat surface. Therefore, a short circuit failure and a stacking failure can be suppressed, and the light emitting laminate can be formed more stably.
- the second transparent material layer 7 b may not be provided as long as the light emitting performance and the like are not affected even if the second transparent material layer 7 b is not provided. If the second transparent material layer 7 b is not provided, the number of layers can be reduced, and thus the device can be manufactured more easily. For example, if the height of the uneven shape of the first transparent material layer 7a does not affect the film formation of the upper layer, the second transparent material layer 7b may not be provided. Even in the case where the second transparent material layer 7 b is not provided, it is possible to enhance the light extraction property by the light diffusion layer 7 configured by the concavo-convex structure 10. However, as described above, it is preferable to form the second transparent material layer 7b in order to suppress a short failure and a disconnection failure.
- the first transparent material layer 7 a and the second transparent material layer 7 b can be provided on the surface of the substrate 6 by applying the materials.
- An appropriate coating method can be adopted as the method of applying the material, and spin coating may be used, or methods such as slit coating, bar coating, spray coating, ink jet etc. are adopted according to the application and substrate size, etc. can do.
- the concavo-convex structure 10 between the first transparent material layer 7a and the second transparent material layer 7b can be formed by an appropriate method.
- particles such as beads can be mixed with the transparent material to form asperities due to the shape of the particles.
- fine irregularities can be formed efficiently and accurately.
- the fine unevenness can be formed with high accuracy by using the imprint method.
- one uneven area may be constituted by one dot for printing.
- the imprinting method is preferably one that can form a fine structure, and for example, a method called nanoimprinting can be used.
- the imprinting method is roughly divided into a UV imprinting method and a thermal imprinting method, and either of them may be used.
- a UV imprint method can be used.
- the uneven structure 10 can be formed by printing (transferring) the unevenness simply by the UV imprint method.
- a film mold is used which is molded from a Ni master mold in which a rectangular (pillar) structure having a period of 2 ⁇ m and a height of 1 ⁇ m is patterned. Then, a UV curable transparent resin for imprinting is applied to a substrate, and a mold is pressed against the resin surface of the substrate.
- the mold is peeled off after curing of the resin.
- the mold is preferably subjected to release treatment (fluorine-based coating agent or the like) in advance, whereby the mold can be easily peeled off from the substrate.
- the uneven shape of the mold can be transferred to the substrate.
- corrugation corresponding to the shape of the uneven structure 10 is provided in this mold. Therefore, when the unevenness of the mold is transferred, the desired unevenness is formed in the layer of the transparent material. For example, by using a mold in which concave portions are randomly allocated to each section and formed, it is possible to obtain the uneven structure 10 to which convex portions are irregularly allocated.
- FIG. 9 is an example of the uneven structure 10 of the light diffusion layer 7.
- FIG. 9 is composed of FIGS. 9A and 9B.
- the concavo-convex structure 10 in the light diffusion layer 7 preferably has a structure in which a plurality of convex portions 11 or concave portions 12 are arranged in a plane. As a result, it is possible to enhance the diffusion of light without depending on the angle and to extract more light to the outside.
- the surface on which the plurality of projections 11 or the recesses 12 are disposed may be a surface parallel to the surface of the substrate 6.
- FIG. 9 shows that the plurality of convex portions 11 are arranged in a plane.
- the concavo-convex structure 10 may have a structure in which a plurality of convex portions 11 and concave portions 12 are arranged in a plane.
- FIG. 9 shows the concavo-convex structure 10 by a pattern, and the boundaries of the sections are drawn by solid lines. The portion where the convex portion 11 is continuous and the portion where the concave portion 12 is continuous may not actually have a boundary.
- convex portions 11 or concave portions 12 for one section are randomly allocated to grid-like sections and arranged Is preferred.
- An example of a grid-like section is one in which one section is a square. More preferably, the square is a square. In this case, it becomes a matrix grid (square grid) in which a plurality of quadrilaterals are spread in all directions.
- Another example of grid-like sections is one in which one section is hexagonal. More preferably, the hexagon is a regular hexagon.
- honeycomb lattice hexagonal lattice
- the lattice may be a triangular lattice in which triangles are spread, but the square lattice or the hexagonal lattice facilitates control of the unevenness.
- the concavo-convex structure 10 of FIG. 9 is formed by allocating a plurality of convex portions 11 having substantially the same height to each section (grid-like section) of concavities and convexities in a matrix shape and arranging them in a plane. . And the concavo-convex structure 10 is formed so that the area ratio of the convex part 11 in the unit area in planar view is substantially the same in each area. By providing such a concavo-convex structure 10, the light extraction property can be efficiently improved.
- FIG. 9A shows a state as viewed from a direction perpendicular to the surface of the substrate 6, and FIG. 9B shows a state as viewed from a direction parallel to the surface of the substrate 6.
- FIG. 9A sections in which the convex portions 11 are provided are indicated by oblique lines. Lines L1, L2 and L3 in FIG. 9A correspond to lines L1, L2 and L3 in FIG. 9B, respectively.
- the convex portions 11 are allocated and arranged in a matrix-like concavo-convex section in which a plurality of squares are vertically and horizontally arranged like squares (matrix type). It is formed. Each uneven area is equally formed in area.
- One of the convex portion 11 and the concave portion 12 is assigned to one section (one uneven section) of the uneven portion.
- the assignment of the projections 11 may be regular or irregular.
- FIG. 9 the form to which the convex part 11 is allocated at random is shown. As shown in FIG.
- the convex portion 11 is formed by the material constituting the concavo-convex structure 10 protruding toward the light transmitting electrode 2 side. Further, the plurality of convex portions 11 are provided with substantially the same height.
- the heights of the convex portions 11 are substantially equal means, for example, the convex portions within ⁇ 10% of the average height, or preferably within ⁇ 5%, when the heights of the convex portions 11 are averaged. 11 heights may fit and be aligned.
- the cross-sectional shape of the convex part 11 is a rectangular shape in FIG. 9B, it may be an appropriate shape such as a fold, an inverted triangle, or a trapezoidal shape.
- the convex portions 11 are connected to form a large convex portion.
- the concave portion 12 is connected to form a large concave portion.
- the number of connected convex portions 11 and the number of recessed portions 12 is not particularly limited, but may be 100 or less, 20 or less, or 10, for example, because there is a possibility that the fine uneven structure 10 can not be obtained if the number of connected pieces increases.
- the following can be appropriately set.
- a design rule may be provided to invert the next region (convex in the case of concave, concave in the case of convex) in the case where three or more or two or more of the recesses 12 or the projections 11 continue. By this rule, the light diffusion effect is enhanced, and improvement in efficiency and color difference can be expected.
- the area ratio of the convex portion 11 in the unit area is formed to be substantially the same in each area.
- FIG. 9A a total of 100 uneven sections, 10 vertical and 10 horizontal, are illustrated, and such an area of 100 partitions can be used as a unit area.
- the area ratio at which the convex portion 11 is formed is substantially equal for each unit region. That is, as shown in FIG. 9A, assuming that 50 convex portions 11 are provided in the unit area, about 50 (about 45, for example) are formed in other areas having the same number of uneven sections and the same area. There may be provided up to 55 or 48 to 52 convex portions 11.
- the unit area is not limited to 100 divisions, and can be sized as appropriate for the number of divisions.
- the number of sections may be 1000, 10000, 100000, or more.
- the area ratio of the convex portion 11 may be slightly different depending on how the region is taken, in this example, the area ratio is made to be substantially the same.
- the upper and lower limits of the area ratio are preferably 10% or less of the average, more preferably 5% or less, still more preferably 3% or less, and still more preferably 1% or less. More preferable. By equalizing the area ratio, it is possible to improve the light extraction more uniformly in the plane.
- the area ratio of the projections 11 in the unit area is not particularly limited, but is, for example, in the range of 20 to 80%, preferably in the range of 30 to 70%, and more preferably 40 to 60%. It can be set within the range.
- the convex portions 11 and the concave portions 12 are one aspect preferable to be randomly allocated and disposed in the unit area. Thereby, a plurality of light can be extracted more independently of the angle. Thereby, the structure is particularly suitable for the organic EL element for illumination.
- the uneven structure 10 is preferably a fine uneven surface. Thereby, light extraction can be further enhanced.
- a minute uneven structure can be formed by setting one section of the unevenness to a square range of 0.1 to 100 ⁇ m on one side.
- One side of the square forming one section of the unevenness may be 0.4 to 10 ⁇ m.
- the unit area can be a square area of 1 mm long ⁇ 1 mm wide, or a square area of 10 mm long ⁇ 10 mm wide.
- the concavo-convex structure 10 may not be provided with a material that constitutes the concavo-convex structure 10.
- the lower layer (the first transparent material layer 7a) in the concavo-convex structure 10 may be a layer in which a large number of fine projections 11 are dispersed in an island shape over the entire surface.
- the second transparent material layer 7 b may be in direct contact with the substrate 6 in the portion of the recess 12.
- the height of the convex portion 11 is not particularly limited, but may be, for example, in the range of 0.1 to 100 ⁇ m. Thereby, the uneven structure 10 having high light extraction property can be obtained. For example, when the height of the convex portion 11 is in the range of 1 to 10 ⁇ m, fine irregularities can be formed with high accuracy.
- the plurality of convex portions 11 constituting the concavo-convex structure 10 may have the same shape.
- the convex part 11 is provided in the whole of one uneven
- the planar shape of the convex portion 11 may be another shape. For example, it may be circular or polygonal (triangular, pentagonal, hexagonal, octagonal, etc.).
- the three-dimensional shape of the convex portion 11 may be an appropriate shape such as a cylindrical shape, a prismatic shape (triangular pyramid, a quadrangular prism, etc.), or a pyramid shape (triangular pyramid, a square pyramid, etc).
- the concavo-convex structure 10 is a form that is preferably formed as a diffractive optical structure. At this time, it is preferable that the convex portions 11 be provided with a certain regularity so as to have a diffractive structure. In the diffractive optical structure, it is more preferable that the convex portions 11 be formed with periodicity.
- the light diffusion layer 7 has a diffractive optical structure, the light extraction property can be improved.
- a light extraction layer such as an optical film
- the period P of the two-dimensional concavo-convex structure 10 (in the case of a structure without periodicity, the average period of the concavo-convex structure)
- This range may be set when the wavelength of light emitted from the light emitting layer is in the range of 300 to 800 nm.
- the geometrical optical effect that is, by increasing the area of the surface where the incident angle is less than the total reflection angle, the light extraction efficiency is improved or the light having the total reflection angle or more by the diffracted light is extracted. Light extraction efficiency can be improved.
- the effective refractive index in the vicinity of the concavo-convex structure decreases gradually as the distance from the surface of the substrate increases. . Therefore, a thin film layer having a refractive index intermediate between the refractive index of the medium of the layer forming the concavo-convex structure and the refractive index of the covering layer or the anode is interposed between the substrate and the uneven coating layer or the anode. And it is possible to reduce Fresnel reflection.
- the period P in the range of ⁇ / 4 to 100 ⁇ , reflection (total reflection or Fresnel reflection) can be suppressed, and light extraction efficiency can be improved.
- the period P is smaller than ⁇ , only the Fresnel loss suppression effect can be exhibited and the light extraction effect may be reduced.
- it exceeds 20 ⁇ it is required to increase the height of the unevenness correspondingly (to obtain a phase difference), and there is a possibility that the flattening in the covering layer (the second transparent material layer 7b) is not easy.
- the period P is set to, for example, ⁇ to 20 ⁇ .
- the uneven structure 10 may be a boundary diffraction structure.
- the boundary diffraction structure may be formed by arranging the convex portions 11 at random.
- the boundary diffraction structure it is possible to use a structure in which a diffraction structure partially formed in a minute region in a plane is disposed on one side.
- the structure may be a structure in which a plurality of independent diffraction structures are formed in the plane.
- the boundary diffractive structure due to the fine diffractive structure, it is possible to take out light utilizing diffraction, and to suppress the intensification of the diffractive action of the entire surface to reduce the angular dependence of the light. Therefore, the light extraction effect can be enhanced while suppressing the angular dependence.
- the convex portions 11 and the concave portions 12 are randomly disposed as shown in FIG. 9, if the convex portions 11 or the concave portions 12 are too continuous, there is a possibility that the light extraction property can not be sufficiently improved. Therefore, it is preferable to provide a rule that the same block (one of the convex portion 11 and the concave portion 12) is not continuously arranged in a predetermined number or more. That is, the convex portions 11 are arranged so as not to be continuously arranged in the same direction in the grid direction in the same direction, and the concave portions 12 are not continuously arranged in the same direction in the same direction in the same direction. It is preferable that it is arrange
- the angular dependence of the luminescent color can be reduced. Ten or less are preferable, as for the predetermined number which the convex part 11 and the recessed part 12 do not line up continuously, eight or less are more preferable, five or less are more preferable, and four or less are still more preferable.
- the plurality of convex portions 11 or concave portions 12 preferably have an axial length of an inscribed ellipse or a diameter of an inscribed circle in a range of 0.4 to 4 ⁇ m when viewed in a direction perpendicular to the surface of the substrate 6 .
- the plurality of convex portions 11 at this time are considered as convex portions in which the convex portions 11 are continuously connected and enlarged.
- the plurality of recesses 12 at this time are considered to be recesses formed by connecting the recesses 12 continuously.
- the inscribed ellipse and the inscribed circle can be drawn with virtual lines in plan view seen from the direction perpendicular to the surface of the substrate 6.
- FIG. 10 Each example of the uneven structure 10 is shown in FIG.
- the concavo-convex structure 10 is controlled such that the same blocks (convex parts 11 and concave parts 12) do not line up in the same direction with a predetermined number or more, while the arrangement has randomness.
- FIG. 10A three or more blocks are not aligned in the same direction
- FIG. 10B four or more blocks are not aligned in the same direction.
- the average of the number of arranged blocks can be represented by an average pitch.
- the block is the convex portion 11 or the concave portion 12 assigned to one section.
- the average pitch can be expressed using the width w of one block.
- the concavo-convex structure 10 in FIG. 10B has a hexagonal grid structure and an average pitch of 3 w.
- the plurality of convex portions 11 or concave portions 12 preferably have an axial length of an inscribed ellipse or a diameter of an inscribed circle of 0. 0 when viewed from a direction perpendicular to the surface of the substrate 6. It is in the range of 4 to 4 ⁇ m.
- the width w means the width of one section of the concavo-convex structure 10.
- the width w is the length of one side of the square.
- the width w is the distance between the two opposing sides.
- the width w is preferably 0.1 to 100 ⁇ m, and more preferably 0.4 to 10 ⁇ m.
- a lighting device can be obtained by using the organic EL element as described above.
- the lighting device may include, for example, an organic EL element, a power supply, a switch, and an electrical wiring that electrically connects these.
- the lighting device can be configured as a white light lighting device. However, even if it is white light emission, adjustment of the light emission color is possible, and it can emit light of various color temperatures required for lighting applications. For example, in the classification of color temperature, colors such as light bulb color, warm white, white, daylight white, daylight color can be emitted. And, with the above-mentioned organic EL element, it is possible to provide a lighting device having a high light extraction efficiency and an excellent viewing angle characteristic.
- FIG. 11 is an example of the lighting device 100.
- the lighting device includes an organic EL element 101, a housing 102, a plug 103, and a wiring 104.
- a plurality of (four) organic EL elements 101 are disposed in a plane.
- the organic EL element 101 is housed in a housing 102. Electricity is supplied through the plug 103 and the wiring 104, the organic EL element 101 emits light, and light is emitted from the lighting device 100.
Abstract
Description
図2に示す層構成の有機EL素子を基本として、発光層5の構成を変更して、有機EL素子を設計し、上記の構成が好ましいこと、及びさらに好ましい態様を説明する。図2の有機EL素子は、図1の有機EL素子から光拡散層7を除いた構成となっており、それ以外は、図1の有機EL素子と同じ層構成となっている。ただし、発光層5の発光波長等は適宜変更を加える。図1の構成と同じ構成については同じ符号を付して説明を省略する。光拡散層7を省略することにより、素子を単純化して好適な設計を行うことができる。
有機EL素子の発光色の色温度は2500K以下であることが好ましい一態様である。それにより、高効率の照明装置を実現することが可能である。色温度が2500K以下の照明は有機EL素子の使用が有利である。色温度が2500K以下の発光色は、無機材料のLEDでは、実現しにくく、実現したとしても効率が非常に悪い。無機材料のLEDでは、2500K以下の発光色にするために、青から赤に波長変換することが求められ、その際のロスが大きいためである。
有機EL素子は、発光層の膜厚が数百nmと比較的薄く、光の波長(媒質内を伝播する波長)と非常に近いため、有機EL素子内部で薄膜干渉が生じる。その結果、有機層の膜厚によって内部の発光が干渉し、出射する光の強度が大きく増減する。出射する光の強度を最大限に高めるためには、発光層から光取り出し側へ直接向かう光(直接光)と、発光層から反射性の電極へ向かった後にこの電極で反射されてから光取り出し側へ向かう光(反射光)とが、干渉しあって強めあうようにする。光が反射層において反射すると、その前後で位相シフトπが生じる。そこで、理想モデルにおいては、発光源と反射層の表面との間の膜厚dに屈折率nを乗じて導出される光学膜厚(光学的距離)が、光の波長λの1/4πの奇数倍と略等しくなるように設計される。これにより、基板から正面方向に出射する光の成分量が極大値となる。いわゆるキャビティ設計である。この方法は、光が内部で増幅されることを意味するわけではなく、光の方向を変更させ、特定の方向、例えば、大気中へ光を取り出しやすい正面方向への光を強めることを意味する。しかしながら、実際には、光の位相シフトはπとはならず、有機層及び反射層における屈折、消衰が関わってくることとなり、より複雑な挙動を示す。このときの光の位相シフトをφと表すことができる。有機EL素子ではこの位相シフトφを用いて素子を設計することができる。
有機EL素子の光取り出し設計における、さらに好ましい関係を説明する。
上記の有機EL素子では、長波長発光ユニット1Lの数が短波長発光ユニット1Sの数よりも多いため、長波長側の成分が相対的に多くなる構成となっている。そのため、内部で吸収される成分が相対的に小さく光取出し効率が高くなる。これは、一般的に材料を構成する有機材料、電極を構成する材料、および光取出し構造を構成する部材すべてにおいて、一般的に短波長成分の方が吸収が多いことから理解される。
有機EL素子を構成する材料を説明する。有機EL素子は、有機EL素子を製造するために通常用いられる適宜の材料で形成され得る。
光拡散層7の好ましい一例を以下に説明する。図1の有機EL素子は、光拡散層7を有している。
上記のような有機EL素子を用いることにより、照明装置を得ることができる。照明装置は、例えば、有機EL素子と、電源と、スイッチと、これらを電気的に接続する電気配線とを備えていてよい。照明装置は、白色発光の照明装置として構成することができる。ただし、白色発光といっても、発光色の調節が可能であり、照明用途として求められる種々の色温度の光を発することができる。例えば、色温度の分類において、電球色、温白色、白色、昼白色、昼光色などの色を発することができる。そして、上記の有機EL素子では、光取り出し効率が高く、視野角特性に優れた照明装置を提供することが可能である。
1S 短波長発光ユニット
1L 長波長発光ユニット
2 光透過性電極
3 光反射性電極
5 発光層
6 基板
7 光拡散層
Claims (10)
- 複数の前記発光ユニットは、複数の発光材料を含む前記発光ユニットを1以上有する、請求項1に記載の有機エレクトロルミネッセンス素子。
- 発光色の色温度は2500K以下である、請求項1又は2に記載の有機エレクトロルミネッセンス素子。
- 複数の前記発光ユニットは、1つの前記短波長発光ユニットと、2つの前記長波長発光ユニットとで構成されている、請求項1~3のいずれか1項に記載の有機エレクトロルミネッセンス素子。
- 複数の前記発光ユニットは、光透過性電極と光反射性電極との間に配置され、
前記光反射性電極に最も近い前記発光ユニットは、前記短波長発光ユニットにより構成されている、請求項1~5のいずれか1項に記載の有機エレクトロルミネッセンス素子。 - 複数の前記発光ユニットは、光透過性電極と光反射性電極との間に配置され、
前記光透過性電極、複数の前記発光ユニット、及び、前記光反射性電極は、基板に支持されており、
前記基板と前記光透過性電極との間に、光拡散層を有する、請求項1~6のいずれか1項に記載の有機エレクトロルミネッセンス素子。 - 複数の前記発光ユニットは、光透過性電極と光反射性電極との間に配置され、
複数の前記発光ユニットは、前記光反射性電極側から、緑色発光材料を含む前記発光ユニット、青色発光材料を含む前記発光ユニット、及び、赤色発光材料を含む前記発光ユニット、の順に配置されている、請求項1~7のいずれか1項に記載の有機エレクトロルミネッセンス素子。 - 複数の前記発光ユニットは、光透過性電極と光反射性電極との間に配置され、
複数の前記発光ユニットは、前記光反射性電極側から、青色発光材料を含む前記発光ユニット、赤色発光材料を含む前記発光ユニット、及び、緑色発光材料を含む前記発光ユニット、の順に配置されている、請求項1~7のいずれか1項に記載の有機エレクトロルミネッセンス素子。 - 請求項1~9のいずれか1項に記載の有機エレクトロルミネッセンス素子を備えた照明装置。
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US14/787,337 US9786859B2 (en) | 2013-05-17 | 2014-05-13 | Organic electroluminescent element and lighting device |
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Also Published As
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KR20150142009A (ko) | 2015-12-21 |
CN105165123B (zh) | 2017-06-23 |
JPWO2014185063A1 (ja) | 2017-02-23 |
JP6308475B2 (ja) | 2018-04-11 |
DE112014002456B4 (de) | 2017-07-13 |
KR101716701B1 (ko) | 2017-03-15 |
US9786859B2 (en) | 2017-10-10 |
DE112014002456T5 (de) | 2016-01-28 |
US20160064682A1 (en) | 2016-03-03 |
CN105165123A (zh) | 2015-12-16 |
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