WO2013035299A1 - 発光装置および光シート - Google Patents
発光装置および光シート Download PDFInfo
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- WO2013035299A1 WO2013035299A1 PCT/JP2012/005563 JP2012005563W WO2013035299A1 WO 2013035299 A1 WO2013035299 A1 WO 2013035299A1 JP 2012005563 W JP2012005563 W JP 2012005563W WO 2013035299 A1 WO2013035299 A1 WO 2013035299A1
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- diffraction grating
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- 238000009792 diffusion process Methods 0.000 claims abstract description 95
- 238000002834 transmittance Methods 0.000 claims abstract description 26
- 239000010410 layer Substances 0.000 claims description 211
- 239000011241 protective layer Substances 0.000 claims description 7
- 238000000605 extraction Methods 0.000 description 32
- 239000000758 substrate Substances 0.000 description 12
- 230000000694 effects Effects 0.000 description 9
- 230000003287 optical effect Effects 0.000 description 7
- 238000002474 experimental method Methods 0.000 description 5
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- 238000000034 method Methods 0.000 description 5
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- 239000011521 glass Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000005855 radiation Effects 0.000 description 2
- NCGICGYLBXGBGN-UHFFFAOYSA-N 3-morpholin-4-yl-1-oxa-3-azonia-2-azanidacyclopent-3-en-5-imine;hydrochloride Chemical compound Cl.[N-]1OC(=N)C=[N+]1N1CCOCC1 NCGICGYLBXGBGN-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005401 electroluminescence Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- 239000004065 semiconductor Substances 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/80—Constructional details
- 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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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
- G02B5/0252—Diffusing elements; Afocal elements characterised by the diffusing properties using holographic or diffractive means
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0273—Diffusing elements; Afocal elements characterized by the use
- G02B5/0278—Diffusing elements; Afocal elements characterized by the use used in transmission
Definitions
- the present application relates to a sheet and a light emitting device including the sheet.
- FIG. 1 schematically shows a cross-sectional structure of a general organic EL element.
- a conventional organic EL element has a structure in which an electrode 2, a light emitting layer 3, a transparent electrode 4 and a transparent substrate 5 are laminated on a substrate 1. The transparent substrate 5 is in contact with the air layer 6.
- the light emitter emits light at a point S inside the light emitting layer 3. A part of the generated light propagates in the direction of the air layer 6 as it is, and a part of the light propagates in the direction of the air layer 6 after being reflected by the electrode 2.
- the organic EL element shown in FIG. 1 light that can be extracted outside the element emits light at the point S and is incident on the interface between the air layer 6 and the transparent substrate 5 at an angle smaller than the critical angle ⁇ c. Limited to. If the light emission from the point S is isotropic, the interference effect of light is ignored, and the transmittance on the refractive surface is assumed to be 100% at an incident angle within the critical angle, the rate at which light can be extracted ( (Light extraction efficiency) ⁇ is expressed by 1-cos ⁇ c . For example, when the refractive index of the light emitting layer 3 is 1.7, the extraction efficiency ⁇ is less than 20%. As described above, the organic EL element generally does not have high light use efficiency.
- Patent Document 1 As a technique for more efficiently extracting light from such an organic EL element, there is a technique disclosed in Patent Document 1, for example.
- Patent Document 1 discloses an organic EL element in which light extraction efficiency is improved by forming a diffraction grating on a substrate interface or a reflection surface and changing an incident angle of light with respect to an interface where total reflection occurs.
- the diffraction efficiency and the diffraction angle when light passes through the diffraction grating structure depend on the wavelength and the incident angle of the light. For this reason, the intensity of the light emitted from the organic EL element changes with respect to the viewing angle (brightness unevenness). Further, when the illuminant generates white light, the color changes with respect to the viewing angle (color unevenness). Furthermore, even when the element is not emitting light, the light reflectance and reflection angle of the diffraction grating structure depend on the wavelength, so that the color of the organic EL element changes depending on the viewing angle, thereby deteriorating the appearance.
- One non-limiting exemplary embodiment of the present application provides a light sheet and a light-emitting device that can suppress uneven brightness and uneven color and improve light extraction efficiency.
- a light-emitting device which is one embodiment of the present invention includes a light-emitting layer, a diffraction grating structure including a diffraction grating, and a diffusion layer having a structure for diffusing light transmitted from one surface to the other surface.
- the center wavelength of the emitted light is ⁇
- the period p of the diffraction grating is 1.0 ⁇ to 3.5 ⁇
- the diffusion layer has a haze of 80% or more and a total light transmittance of 80% or less.
- the light-emitting device of one embodiment of the present invention since the diffraction grating structure and the diffusion layer are provided, the light extraction efficiency can be improved, and uneven brightness and uneven color can be effectively suppressed.
- FIG. 1 It is a figure which shows the structure of a general organic EL element, and the mode of light propagation. It is a figure which shows typically the cross-section of 1st Embodiment of a light-emitting device.
- (A)-(e) is a figure which shows the pattern of a diffraction grating typically. It is a figure which shows the mode of the light which permeate
- (A) shows the diffraction pattern of light by a diffraction grating structure
- (b) And (c) is a schematic diagram which shows the cross-sectional structure and planar structure of a diffraction grating structure.
- (A) And (b) is a figure which shows the relationship between the period of a diffraction grating structure, light extraction efficiency, and a color difference in 1st Embodiment. It is a graph which shows the taking-out efficiency at the time of using the diffused layer of various haze and transmittance
- a light-emitting device which is one embodiment of the present invention includes a light-emitting layer, a diffraction grating structure including a diffraction grating, and a diffusion layer having a structure for diffusing light transmitted from one surface to the other surface.
- the center wavelength of the emitted light is ⁇
- the period p of the diffraction grating is 1.0 ⁇ or more and 3.5 ⁇ or less
- the diffusion layer has a haze of 80% or more and a total light transmittance of 80% or less.
- the diffraction grating structure may be located between the diffusion layer and the light emitting layer.
- the diffusion layer may be in contact with air.
- the light emitting device may further include a protective layer, the diffusion layer may be located between the protective layer and the diffraction grating structure, and the protective layer may be in contact with air.
- the light-emitting device further includes first and second electrodes that are in contact with the light-emitting layer and sandwich the light-emitting layer, and the first electrode is sandwiched between the diffusion layer and the light-emitting layer. It is transparent to the emitted light, and the diffraction grating structure may be provided at an interface in contact with the first electrode of the light emitting layer.
- the diffusion layer may be located between the diffraction grating structure and the light emitting layer.
- the light emitting device further includes first and second electrodes that are in contact with the light emitting layer and sandwich the light emitting layer, and the first electrode is sandwiched between the diffusion layer and the light emitting layer, and the light emitting layer
- the second electrode may be transparent to the light emitted from the light emitting layer, and the second electrode may reflect the light emitted from the light emitting layer.
- the light emitting layer may be located between the diffusion layer and the diffraction grating structure.
- the light-emitting device further includes first and second electrodes that are in contact with the light-emitting layer and sandwich the light-emitting layer, and the first electrode is sandwiched between the diffusion layer and the light-emitting layer. It is transparent to the emitted light, and the diffraction grating structure may be provided at an interface in contact with the second electrode of the light emitting layer.
- a sheet according to another embodiment of the present invention includes a diffraction grating structure including a diffraction grating, and a diffusion layer having a structure that diffuses light transmitted from one surface to the other surface, and the light emitted from the light emitting layer
- the diffraction grating has a period p of 1.0 ⁇ or more and 3.5 ⁇ or less, and the diffusion layer has a haze of 80% or more and a total light transmittance of 80% or less.
- FIG. 2 schematically shows a cross-sectional structure of the first embodiment of the light-emitting device according to the present invention.
- the light emitting device 101 includes an electrode 2 provided on the substrate 1, a light emitting layer 3 located on the electrode 2, an electrode 4 located on the light emitting layer 3, a layer 51 located on the electrode 4, and a layer 51.
- a diffraction grating structure 71 located above, a layer 52 located on the diffraction grating structure 71, and a diffusion layer 72 located on the layer 52 are provided.
- the light emitting layer 3 that emits white light is used.
- the light emitting device using the light emitting layer 3 include a light emitting device using an organic EL element.
- organic EL in order to obtain high luminous efficiency, the portion of the light emitting layer 3 may be composed of a plurality of layers, but in the following description, such a plurality of layers are collectively expressed as the light emitting layer 3.
- the electrode 2 and the electrode 4 may be in contact with the light emitting layer 3 and sandwich the light emitting layer 3 so as to be electrically connected to the light emitting layer 3.
- the electrode 2 may be transparent to the light emitted from the light emitting layer 3. When light is not extracted from the substrate 1 side, the electrode 2 may be opaque to the light emitted from the light emitting layer 3.
- the substrate 1 supports the light emitting layer 3 sandwiched between the electrode 2 and the electrode 4.
- the material of the substrate 1 is not particularly limited, and a known support substrate such as glass can be used as the substrate 1.
- the light emitted from the light emitting layer 3 is transmitted through the diffraction grating structure 71, further through the diffusion layer 72, and then emitted to the air layer 6 outside the light emitting device 101.
- the layers 51 and 52 are appropriately used for the purpose of securing flatness, for the purpose of adhesion, for protection of two layers sandwiching each layer, and for protection.
- the layers 51 and 52 may be transparent to the light emitted from the light emitting layer 3. These layers may be omitted, or two or more layers 51 and 52 may be provided. That is, in the present embodiment, the diffraction grating structure 71 may be positioned between the diffusion layer 72 and the light emitting layer 3 so that light is emitted from the diffusion layer 72 to the air layer 6.
- the diffraction grating structure 71 has a sheet shape in this embodiment.
- the diffraction grating structure 71 has a structure in which a diffraction grating is formed in two dimensions.
- FIGS. 3A to 3E show examples of diffraction gratings arranged two-dimensionally.
- the diffraction grating structure 71 may be configured by various structures.
- an optical step may be formed by a difference in the refractive index of the material, for example, one of the region shown in white and the region shown in black is air and the other is made of glass or the like. Both of the regions shown are made of the same optical material, but optical steps may be formed by different heights (thicknesses).
- the diffusion layer 72 has a structure in which light transmitted from one surface to the other surface is diffused by refraction, and a known diffusion plate can be used.
- the light-emitting device 101 of the present embodiment exhibits an effect that cannot be obtained by itself by combining the diffraction grating structure 71 and the diffusion layer 72.
- the optical characteristics of the diffraction grating structure 71 and the diffusion layer 72 alone will be described, and the characteristics of the light emitting device 101 will be described. Note that in the calculations performed in the study described below, the light emitted from the light emitting layer is ignored for the light reflected or totally reflected at the interface where the medium is different, and only the transmitted light is handled.
- n 52 sin ⁇ m ⁇ n 51 sin ⁇ m ⁇ / p (2)
- the diffraction grating structure 71 includes a diffraction grating formed two-dimensionally in the xy direction.
- the period p of the grating is 2.0 ⁇ m and the thickness h is 0.6 ⁇ m.
- region filled with black is comprised with glass, and refractive index is 1.47.
- the refractive index of the white area is 1.78.
- FIG. 5A shows a radiation pattern of transmitted light. Since the diffraction grating structure 71 is composed of a square grating, four diffraction patterns were detected. From these diffraction patterns, it can be confirmed that light is diffracted in the direction ⁇ m satisfying the equation (2).
- the diffusion layer 72 diffuses light that is transmitted from one surface to the other by refraction.
- known structures for diffusing light are roughly classified into two types.
- One is a structure mainly utilizing a “refractive phenomenon” caused by light passing through a structure that is sufficiently large with respect to the wavelength of light (for example, having a size of 5 times or more of the wavelength).
- a prism structure and a structure in which particles of about 10 ⁇ m are dispersed on the structure surface or inside.
- the other is a structure that mainly uses the “diffraction phenomenon” caused by the passage of light through a structure having the size of the wavelength of light.
- a diffraction grating having a regular refractive index distribution with a period of about the wavelength, a minute random pattern of the order of the wavelength (structure disclosed in Japanese Patent Laid-Open No. 2009-217292), and the like can be given.
- the diffusion layer has a structure for diffusing light by utilizing the “refraction phenomenon” of the former light.
- the diffusion layer 72 for example, a diffusion sheet commercially available for use as a backlight of a liquid crystal display device can be used.
- the properties of the diffusing layer 72 may be defined by the total light transmittance when light is incident from the front (JIS K7361-1) and the haze (JIS K7136, ISO 14782) indicating the degree of light diffusion. it can.
- FIG. 6 shows the total light transmittance and haze value of various diffusion sheets having a diffusion structure.
- a diffusion sheet having various combinations of various light transmittances and haze values.
- the diffraction grating structure 71 used in the experiment has the structure shown in FIGS. One side of the square shape as a unit of the diffraction grating is 0.6 ⁇ m, and the period p is 1.2 ⁇ m.
- the diffusion layer 72 the sheet 14 shown in FIG. 6 was used.
- a structure in which the semicylindrical prism 8 is attached to the layer 51 (hereinafter referred to as a planar structure), and a structure in which the semicylindrical prism 8 is attached to the diffraction grating structure 71 via the layer 51 (diffraction).
- the diffraction grating structure 71 was measured on a plane (0-degree direction) perpendicular to the y-axis shown in FIG. 5C and a plane (45-degree direction) inclined 45 degrees in the y-axis direction.
- FIG. 7B shows a graph in which the transmittance of light transmitted through these structures is plotted with respect to the incident angle.
- the diffraction grating structure 71 has the structure described with reference to FIGS. 5B and 5C, the period p is 1 ⁇ m, and the height h is 0.6 ⁇ m.
- the light distribution in the layer 51 is isotropic, that is, it is assumed that light having the same intensity exists at any angle, and the wavelength of the light is 565 nm.
- FIG. 8B shows a polar coordinate display of the light distribution of light that passes through the diffraction grating structure 71 and the layer 52 and emerges in the air layer 6. From this result, it can be seen that the intensity of the extracted light is greater in the case where the light is extracted than in the case where the diffraction grating structure 71 is not provided. However, there is an angle at which the strength suddenly increases. This means that there is a luminance unevenness in which the luminance changes depending on the viewing angle. Further, since the diffraction condition of the formula (2) depends on the wavelength, the position of this peak also depends on the wavelength of the transmitted light. Therefore, when white organic EL is used, it means that color unevenness in which the color changes depending on the angle also occurs. Such a characteristic is caused by the diffraction of light expressed by the equation (2). Therefore, similar characteristics are exhibited even when the diffraction grating structure 71 is arranged so as to be in direct contact with the air layer.
- FIG. 9B shows a polar coordinate display of the light distribution of the light transmitted through the diffusion layer 72 and coming out of the air layer 6. It can be seen that the intensity of the extracted light is increased as compared with the distribution without the diffusion layer 72. In addition, unlike the case where a diffraction grating is used, it can be seen that the curve indicating the light distribution is smooth and does not cause luminance unevenness. However, since the transmittance of the diffusion layer 72 is 75%, the total amount of transmitted light does not increase much compared to the case where the diffusion layer 72 is not provided.
- the diffraction grating structure 71 when the diffraction grating structure 71 is provided in the light emitting device, the amount of transmitted light increases depending on the angle, but unevenness in color and brightness occurs. Further, if the diffusion layer 72 is provided in the light emitting device, a uniform light distribution can be obtained, but the total transmitted light amount does not increase significantly. On the other hand, according to the light emitting device 101 of the present embodiment, it is possible to increase the light extraction efficiency with an excellent light distribution.
- 10A and 10B show the relationship between the period of the diffraction grating structure 71, the light extraction efficiency, and the color difference, respectively, in the light emitting device 101 of this embodiment.
- the maximum change amount ⁇ u′v ′ of (u′v ′) with respect to the viewing angle was plotted. That is, the larger the value of ⁇ u′v ′, the greater the color changes (the color unevenness increases) depending on the viewing angle.
- the diffraction grating structure 71 has the structure shown in FIGS.
- the sheet 14 (FIG. 10A) and the sheet 7 (FIG. 10B) in FIG. 6 were used.
- the sheet 14 has the highest extraction efficiency among the sheets 1 to 15 as a single sheet.
- the sheet 7 has the smallest color difference ⁇ u′v ′ among the sheets 1 to 15 as a single sheet. Details will be described later.
- the center wavelength of the light emitted from the light emitting layer 3 is 565 nm.
- the central wavelength is defined so that the sum of the intensities of light having a wavelength larger than that wavelength in the spectrum is equal to the sum of the intensities of light having wavelengths smaller than that wavelength.
- the extraction efficiency was plotted as a value where the efficiency of an organic EL element having no extraction structure was 1.
- the light intensity of all the diffraction gratings from 0.3 ⁇ m to 12 ⁇ m measured is higher than that of the structure having only the diffraction grating structure.
- the extraction efficiency is improved.
- the period is in the range of 0.55 ⁇ m or more and 2 ⁇ m or less, it is understood that the extraction efficiency exceeding the highest extraction efficiency obtained in the structure having only the diffraction grating structure or the diffusion sheet can be obtained.
- the color difference ⁇ u′v ′ is greatly improved particularly in the range where the period of the diffraction grating is small, compared to the structure having only the diffraction grating structure. More specifically, the color difference ⁇ u′v ′ is small in the structure having only the diffraction grating structure or in all the ranges where the period is 0.3 ⁇ m or more and 12 ⁇ m or less. Furthermore, when the period of the diffraction grating is 0.55 ⁇ m or more and 2 ⁇ m or less, a color difference smaller than the smallest color difference obtained in the structure having only the diffraction grating structure or the structure having only the diffusion sheet can be obtained.
- the diffraction grating is compared with the light emitting device having only the diffraction grating structure as the light extraction structure.
- the period is 0.3 ⁇ m or more and 12 ⁇ m or less, improvement in extraction efficiency and color difference is observed.
- the period of the diffraction grating is 0.55 ⁇ m or more and 2 ⁇ m or less, the light extraction efficiency and the color difference are improved even when compared with the light emitting device having only the diffusion sheet.
- the above experiment was performed in a light emitting device having a center wavelength of 565 nm.
- the same characteristics can be obtained by changing the period condition of the diffraction grating so as to be proportional thereto. That is, when the center wavelength of the light emitted from the light emitting layer 3 is ⁇ , the period of the diffraction grating is preferably 0.5 (0.3 / 0.565) ⁇ to 21 (12 / 0.565) ⁇ , 1.0 (0.55 / 0.565) ⁇ or more and 3.5 (2 / 0.565) ⁇ or less is more preferable.
- the diffraction efficiency of the diffraction grating is proportional to the height and refractive index difference of the diffraction grating structure 71. For this reason, in terms of increasing the diffraction efficiency, it is preferable that the height of the diffraction grating structure and the refractive index difference be large.
- the periodic pattern of the diffraction grating affects only the azimuth direction of the diffracted light, the extraction efficiency does not affect much.
- a periodic pattern in which a lot of diffracted light is generated is preferable, and a triangular lattice in which six diffracted lights are generated is preferable.
- FIGS. 11 and 12 show the extraction efficiency and the color difference ⁇ u′v ′ when the diffusion layer 72 having various haze and transmittance is used.
- the data at the left end shows the measurement results using the structure not including the diffusion layer 72 and the diffraction grating structure 71 and the structure including only the diffraction grating structure 71 without including the diffusion layer 72.
- the period of the diffraction grating is 1.2 ⁇ m
- the height is 1.0 ⁇ m
- the refractive index difference in the diffraction grating is 0.32 (1.46 and 1.78).
- the extraction efficiency and the color difference are improved as compared with the structure not including the diffraction grating structure 71. Further, in the sheet 6 to the sheet 15, the extraction efficiency and the color difference are greatly improved as compared with the structure not including the diffusion layer 72.
- the haze value of these sheets is 80% or more as shown in FIG. Therefore, it can be seen that the haze of the diffusion layer 72 is preferably large in order to improve the extraction efficiency and reduce the color difference.
- the present configuration having the sheets 1 to 5 whose total light transmittance is higher than those of the sheets 6 to 15 is less effective in improving the extraction efficiency and reducing the color difference than the sheets 6 to 15.
- the sheet 5 has a haze exceeding 80%
- the extraction efficiency of the present configuration having the sheet 5 is almost the same as the structure without the diffusion layer 72, and the color difference is not sufficiently small.
- the haze value is 80% or more but also the total light transmittance is preferably relatively small in order to improve the extraction efficiency and reduce the color difference.
- the diffusion layer 72 used in this embodiment has a high haze and a large diffusion spread angle.
- the reflection component increases due to diffusion, so that the total light transmittance is inevitably lowered.
- the total light transmittance is preferably not large.
- the diffusion layer 72 has a haze of 80% or more and a total light transmittance of 80% or less.
- FIG. 13 and FIG. 14 show the angle dependency of luminance and color difference. From FIG. 13 and FIG. 14, it can be seen that the light emitting device of this embodiment has high luminance and small color difference when viewed from any angle. Furthermore, it can be seen that the light extraction efficiency and the color difference change smoothly with respect to the angle, and the luminance unevenness and the color unevenness are effectively suppressed.
- the light extraction efficiency is improved, and the luminance unevenness and the color unevenness can be effectively suppressed.
- FIG. 15 schematically shows a cross-sectional structure of a second embodiment of the light-emitting device according to the present invention.
- the light emitting device 103 further includes a layer 53 positioned on the diffusion layer 72, and is different from the first embodiment in that the layer 53 is an air layer 6.
- the layer 53 is, for example, a protective layer for protecting the diffusion layer 72 from the outside.
- the layer 53 is substantially equivalent to being present.
- the layer 53 can be regarded as a diffusion layer in which the diffusion layer 72 and the layer 53 are integrated.
- the light emitting device of this embodiment can achieve the same effect as that of the first embodiment except that a loss of about several percent is caused thereby.
- FIG. 16 schematically shows a cross-sectional structure of a third embodiment of the light-emitting device according to the present invention.
- the light emitting device 104 is different from the first embodiment in that the positions of the diffraction grating structure 71 and the diffusion layer 72 are interchanged and the electrode 2 has reflectivity.
- the diffusion layer 72 is positioned between the diffraction grating structure 71 and the light emitting layer 3. Further, the electrode 2 has a structure that reflects light emitted from the light emitting layer 3.
- the light emitting device 104 the light reflected to the light emitting layer 3 side by the diffraction grating structure 71 and the diffusion layer 72 can be reflected again to the diffusion layer 72 side by the electrode 2 and can be emitted to the outside.
- the bias of the light distribution is further reduced. Therefore, a light emitting device in which light distribution unevenness and color unevenness are further suppressed as compared with the first embodiment is realized.
- FIG. 17 schematically shows a cross-sectional structure of a fourth embodiment of the light-emitting device according to the present invention.
- the light emitting device 105 is different from the first embodiment in that a diffraction grating structure 71 is provided at the interface between the light emitting layer 3 and the electrode 4.
- the diffraction grating structure 72 is a structure in which a periodic optical path length difference is provided, it can be formed at the interface between the light emitting layer 3 and the electrode 4 or at the interface between the electrode 4 and the light emitting layer 3. it can. More specifically, the diffraction grating structure 72 can be formed by periodically etching the surface of the light emitting layer 3 and the surface of the electrode 4 and embedding with a material having a refractive index different from that of the light emitting layer 3 and the electrode 4. . Alternatively, it is possible to form the light emitting layers 3 and 4 in a periodic pattern using a mask having a fine pattern such as anodized porous alumina.
- FIG. 18 schematically shows a cross-sectional structure of a fifth embodiment of the light-emitting device according to the present invention.
- the light emitting device 106 is different from the first embodiment in that the diffraction grating structure 71 is provided at the interface between the light emitting layer 3 and the electrode 2.
- the present invention is not limited to the above embodiment, and various modifications are possible.
- there is one diffraction grating structure 71 and one diffusion layer 72 but two or more light emitting devices may be included.
- a diffraction grating may also be configured in the stacking direction to realize a three-dimensional diffraction grating structure as a whole.
- the first to fifth embodiments may be combined.
- the vertical cross-sectional shape of the diffraction grating structure and the diffusion layer is not limited to a rectangular shape, but may be a trapezoidal shape or a conical shape, and the slope may be curved.
- slopes and curves are created at the corners. As long as the characteristics of the diffraction grating and the random structure as described in the above embodiments are not lost due to these factors, those shapes are included in the embodiments of the present invention.
- the present invention has been described as a light emitting device.
- the structure of the present invention can be applied to various surface light emitting elements and can be combined with various surface light emitting elements. You may implement this invention as a light sheet.
- the light emitting device and the light sheet disclosed in the present application are suitably used for various light emitting devices, and can be suitably used for a surface light emitting device, for example, an organic EL element.
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Abstract
Description
θc=sin-1(n0/nk) (1)
図2は、本発明による発光装置の第1の実施形態の断面構造を模式的に示している。発光装置101は、基板1上に設けられた電極2と、電極2上に位置する発光層3と、発光層3上に位置する電極4と、電極4上に位置する層51と、層51上に位置する回折格子構造71と、回折格子構造71上に位置する層52と、層52上に位置する拡散層72とを備える。
回折格子構造71として、特許文献1に開示された回折格子の特性を検討した結果を説明する。図4示すように、周期pの回折格子を有する回折格子構造71が屈折率n51である層51および屈折率n52である層52に挟まれた構造において、層51から回折格子構造71に光が角度θで入射する場合について考える。このとき、層52では式(2)を満たす角度θmの方向にm次(mは整数)の回折光が生じる。
n52sinθm-n51sinθ=mλ/p (2)
上述したように、拡散層72は、屈折により一方の面から他方の面へ透過する光を拡散させる。一般に、公知の光を拡散させる構造としては、大きく2つに分類される。
回折格子構造71および拡散層72の光取り出しの特性について行った実験結果を説明する。実験に用いた回折格子構造71は、図5(b)、(c)に示す構造を備えている。回折格子の単位となる正方形の形状の一辺は0.6μmであり、周期pは1.2μmである。拡散層72には、図6に示すシート14を用いた。
図15は、本発明による発光装置の第2の実施形態の断面構造を模式的に示している。発光装置103は、拡散層72上に位置する層53をさらに備え、層53が空気層6としている点で第1の実施形態と異なる。層53はたとえば、拡散層72を外部から保護するための保護層である。
図16は、本発明による発光装置の第3の実施形態の断面構造を模式的に示している。発光装置104は、回折格子構造71と拡散層72との位置が入れ替わっている点、電極2が反射性を有する点で第1の実施形態と異なる。
図17は、本発明による発光装置の第4の実施形態の断面構造を模式的に示している。発光装置105は、回折格子構造71が発光層3と電極4との界面に設けられている点で第1の実施形態と異なる。
図18は、本発明による発光装置の第5の実施形態の断面構造を模式的に示している。発光装置106は、回折格子構造71が発光層3と電極2との界面に設けられている点で第1の実施形態と異なる。
n3(sinθm-sinθ)=mλ/p (3)
2 電極
3 発光層
4 電極
6 空気層
51、52、53 層
71 回折格子構造
72 拡散層
Claims (10)
- 発光層と、回折格子を含む回折格子構造と、一方の面から他方の面へ透過する光を拡散させる構造を有する拡散層を備え、
前記発光層から出射する光の中心波長はλであり、
前記回折格子の周期pは、1.0λ以上3.5λ以下であり、
前記拡散層は、80%以上のヘーズおよび80%以下の全光線透過率を有する、発光装置。 - 前記回折格子構造は前記拡散層および前記発光層の間に位置している、請求項1に記載の発光装置。
- 前記拡散層は空気と接している、請求項2に記載の発光装置。
- 保護層をさらに備え、
前記拡散層は前記保護層および前記回折格子構造の間に位置しており、前記保護層は空気と接している請求項2に記載の発光装置。 - 前記発光層に接しており、前記発光層を挟む第1及び第2の電極をさらに備え、
前記第1の電極は拡散層と前記発光層に挟まれており、前記発光層から出射する光に対して透明であり、
前記回折格子構造は前記発光層の前記第1電極と接する界面に設けられている請求項2から4のいずれかに記載の発光装置。 - 前記拡散層は前記回折格子構造および前記発光層の間に位置している、請求項1から5のいずれかに記載の発光装置。
- 前記発光層に接しており、前記発光層を挟む第1及び第2の電極をさらに備え、
前記第1の電極は前記拡散層と前記発光層に挟まれており、前記発光層から出射する光に対して透明であり、
前記第2の電極は、前記発光層から出射する光を反射する請求項6に記載の発光装置。 - 前記発光層は前記拡散層と前記回折格子構造の間に位置している、請求項1に記載の発光装置。
- 前記発光層に接しており、前記発光層を挟む第1及び第2の電極をさらに備え、
前記第1の電極は拡散層と前記発光層に挟まれており、前記発光層から出射する光に対して透明であり、
前記回折格子構造は前記発光層の前記第2電極と接する界面に設けられている請求項8に記載の発光装置。 - 回折格子を含む回折格子構造と、一方の面から他方の面へ透過する光を拡散させる構造を有する拡散層を備え、
前記発光層から出射する光の中心波長はλであり、
前記回折格子の周期pは、1.0λ以上3.5λ以下であり、
前記拡散層は、80%以上のヘーズおよび80%以下の全光線透過率を有する、シート。
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