JP3962572B2 - Organic electroluminescence light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence (EL) light emitting device suitably used for consumer and industrial display devices (displays), light sources for printer heads, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, EL elements using electroluminescence can self-emit, have high visibility, and are completely solid, so that they have characteristics such as excellent impact resistance. The use as is attracting attention. In particular, an organic EL light emitting device using an organic compound as a light emitting material can greatly reduce the applied voltage, and can be thin and easy to reduce in size and reduce power consumption. It is planned.
[0003]
In such an organic EL light emitting device, a support substrate, an organic EL element, a color conversion layer, a sealing member, and the like are arranged in an order depending on the design of the device, but the organic EL element emits light. , These stacked members are transmitted. In particular, since organic EL elements are vulnerable to water and oxygen, a protective layer is provided to protect them from these.
[0004]
[Problems to be solved by the invention]
However, since the refractive index of the protective layer is different from the members above and below the protective layer, a difference in refractive index occurs at the interface. Due to this difference in refractive index, there is a problem that light is reflected at the interface and the amount of emitted light taken out is reduced. In addition, there is a problem that viewing angle characteristics deteriorate such that light interferes and the same color is recognized as a different color depending on the viewing angle.
[0005]
The present invention provides an organic EL light-emitting device that can prevent a decrease in light emission amount due to an interference effect caused by internal reflection of light, can extract more light to the outside, and has excellent viewing angle characteristics. Objective.
[0006]
The present inventors have found that the above problem can be solved by changing the refractive index of the protective layer provided in the organic EL light emitting device.
[0007]
[Means for Solving the Problems]
According to the present invention, the first member, the protective layer, and the second member are provided in this order in the light extraction direction, the refractive index of the first member is n1, and the refraction of the second member The refractive index at the x position of the protective layer is nx, which is different from n1, and in the thickness direction of the protective layer sandwiched between the first member and the second member, the refractive index is second from the x position of the protective layer. When the refractive index at the y position close to the member is ny, the refractive indexes nx and ny satisfying the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx | At least one set of organic electroluminescent light emitting devices is provided.
[0008]
An example of the relative relationship of the refractive index of the present invention is shown in FIG. In FIG. 1A, the refractive indexes n1 and n2 indicate the refractive indexes of the first member and the second member, respectively. When the refractive index of the first member and the second member is not constant, it is the refractive index at the interface with the protective layer. The refractive indexes nx and ny indicate the refractive indexes at the x position and the y position in the protective layer, respectively. The x position is an arbitrary position in the protective layer, and the y position is an arbitrary position closer to the second member than the x position in the thickness direction of the protective layer indicated by the arrow.
| N2-ny | <| n2-nx | means that nx is larger than ny and greater than n2, and | n1-ny |> | n1-nx | It means that the difference of is larger.
In the present invention, it is sufficient that at least one combination of nx and ny having such a relationship exists in the protective layer.
[0009]
For example, FIG. 1B shows a combination of nx and ny that is not in a relationship defined by the present invention. In this combination, | n2-ny | = | n2-nx | and | n1-ny | = | n1-nx |. Further, FIG. 1C shows another combination of nx and ny that is not related to the present invention. In this combination, | n2-ny |> | n2-nx | and | n1-ny | <| n1-nx |.
In the protective layer of the present invention, it is sufficient that at least one combination of nx and ny shown in FIG. 1 (a) is present, so that any refractive index of the protective layer has the relationship shown in FIG. 1 (a). Moreover, you may include the combination of nx and ny partially shown in FIG.1 (b) and / or FIG.1 (c). However, the present invention does not include those in which all the refractive indexes of the protective layer are in the relationship shown in FIG. 1B and / or FIG. 1C.
[0010]
In the present invention, the refractive index of the protective layer changes so that the refractive index difference between the protective layer and the first member and the refractive index difference between the protective layer and the second member become small. The refractive index of the protective layer is preferably changed approximately between n1 and n2.
“Change in refractive index” means that the refractive index increases or decreases generally from the first member toward the second member. The aspect of the refractive index change is not particularly limited. The example of the aspect of a change is shown to Fig.2 (a)-(d). 2A shows a linear change, FIG. 2B shows a curvilinear change, and FIGS. 2C and 2D show stepwise changes. The change in the refractive index may be a combination of these aspects. The refractive index of the protective layer is preferably changed gradually and continuously.
At the interface between the first member and the protective layer and at the interface between the second member and the protective layer, the refractive index at the interface of the protective layer is preferably equal to n1 and n2, respectively, Or smaller.
[0011]
By including the protective layer with the refractive index changed in this way, it is possible to prevent a decrease in the amount of light emission due to the interference effect due to the internal reflection of light, and to extract more light to the outside, and the color of the emission color The viewing angle dependence of the degree can be reduced, and an organic EL light emitting device excellent in viewing angle characteristics can be obtained.
[0012]
Moreover, unless the effect of this invention is impaired, you may provide another member or space | gap between a 1st member and a protective layer, and between a protective layer and a 2nd member. For example, when a gap is provided between the protective layer and the second member, and this gap can be regarded as being close to the refractive index 1, the gap can be considered as the second member, in which case n2≈ It is preferable that the refractive index is changed from n1 and is changed as described above.
[0013]
In another aspect of the present invention, the first electrode, the organic light emitting medium, the second electrode, the protective layer, and the color conversion layer are provided in this order in the light extraction direction, and the refractive index of the second electrode Is n1, the refractive index of the color conversion layer is n2 different from n1, the refractive index at the x position of the protective layer is nx, and in the thickness direction of the protective layer sandwiched between the second electrode and the color conversion layer When the refractive index at the y position closer to the color conversion layer than the x position of the protective layer is ny, the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx | It is an organic electroluminescence light-emitting device in which at least one set of refractive indexes nx and ny satisfying the above conditions.
[0014]
An example of this aspect is shown in FIGS. 3 (a) and 3 (b). FIG. 3A is a type in which light is extracted from above, and the support substrate 2, the first electrode 10, the organic light emitting medium 12, the second electrode 14, the protective layer 20, and the color in the direction of extracting the light indicated by the arrows. The conversion layer 22 and the sealing member 24 are provided in this order. FIG. 3B is a type in which light is extracted from below, and the first electrode 10, the organic light emitting medium 12, the second electrode 14, the protective layer 20, the color conversion layer 22, The support substrate 2 is provided in this order.
As shown in this figure, in the organic electroluminescence light emitting device, when a color conversion layer 22 is provided, a device capable of full color display is obtained. However, it is of course possible to provide a plurality of types of organic luminescent media so as to emit a plurality of luminescent colors without providing the color conversion layer 22 so that color display is possible.
[0015]
Yet another aspect of the present invention is that the first electrode, the organic light emitting medium, the second electrode, the protective layer, and the sealing member are provided in this order in the light extraction direction, and the refractive index of the second electrode is n1, the refractive index of the sealing member is n2 different from n1, the refractive index at the x position of the protective layer is nx, and in the thickness direction of the protective layer sandwiched between the second electrode and the sealing member, When the refractive index at the y position closer to the sealing member than the x position of the protective layer is ny, the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx | It is an organic electroluminescence light-emitting device in which at least one set of refractive indexes nx and ny to be satisfied exists.
[0016]
An example of this aspect is shown in FIG. FIG. 3C is a type in which light is extracted from above, and the support substrate 2, the first electrode 10, the organic light emitting medium 12, the second electrode 14, the protective layer 20, The stop member 24 and the color conversion layer 22 are provided in this order.
[0017]
According to still another aspect of the present invention, the first electrode, the organic light emitting medium, the second electrode, the protective layer, and the support substrate are provided in this order in the light extraction direction, and the refractive index of the second electrode is n1. The refractive index of the supporting substrate is n2, which is different from n1, the refractive index at the x position of the protective layer is nx, and the thickness of the protective layer sandwiched between the second electrode and the supporting substrate is When the refractive index at the y position closer to the support substrate than the x position is ny, the refractive index nx satisfying the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx | And ny are organic electroluminescence light emitting devices.
[0018]
An example of this aspect is shown in FIG. FIG. 3D is a type in which light is extracted from below, and the first electrode 10, the organic light emitting medium 12, the second electrode 14, the protective layer 20, the support substrate 2, the color in the direction in which the light indicated by the arrow is extracted. The conversion layer 22 is provided in this order.
[0019]
Still another aspect of the present invention is that the first electrode, the organic light emitting medium, the second electrode, the color conversion layer, the protective layer, and the support substrate are provided in this order in the light extraction direction, and the color conversion layer is refracted. The refractive index of the supporting substrate is n2 different from n1, the refractive index at the x position of the protective layer is nx, and the protective layer is protected in the thickness direction of the protective layer sandwiched between the color conversion layer and the supporting substrate. When the refractive index at the y position closer to the support substrate than the x position of the layer is ny, the refraction satisfies the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx | It is an organic electroluminescence light emitting device in which at least one set of ratios nx and ny exists.
[0020]
An example of this aspect is shown in FIG. FIG. 3 (e) is a type in which light is extracted from below, and the first electrode 10, the organic light emitting medium 12, the second electrode 14, the color conversion layer 22, the protective layer 20, in the direction of extracting the light indicated by the arrows, The support substrate 2 is provided in this order.
[0021]
The smaller the refractive index difference at the interface between the protective layer and the member in contact therewith, the better. The absolute value of the difference in refractive index is preferably less than 0.2, and more preferably less than 0.1.
Moreover, it is preferable that n1> n2 and nx> ny.
When the refractive index has such a relationship, since the refractive index of the first member, the protective layer, and the second member decreases in the same direction as the light extraction direction, more light can be extracted to the outside. . Further, it is more preferable that n1> nx> ny> n2.
[0022]
When the refractive index difference is in such a range, the reflectance at the interface can be made smaller, so that more light can be extracted outside.
Further, when the refractive index difference is in such a range, excellent viewing angle characteristics can be obtained, so that even when the emission color is viewed obliquely, the same color as when viewed from the front can be recognized. Furthermore, total reflection at the interface between the protective layer and the member sandwiching the protective layer can be mitigated. This improves the light extraction efficiency. In particular, when the refractive index of the second member is as small as 1.5 or less, the effect of alleviating total reflection is great. For example, when the second member is a gap, the light extraction efficiency can be greatly improved by using the protective layer of the present invention.
[0023]
When light passes through the interface between the two layers a and b made of materials having different refractive indexes, the reflectance R at the interface (reflectance with respect to light perpendicular to the interface) and the refraction of the material at the two layers Rate n_aAnd n_bIs expressed by the following equation.
R = (n_a-N_b)²/ (N_a+ N_b)²
Therefore, as understood from this relational expression, the refractive index n of the material in the two layers_aAnd n_bThe smaller the difference is, the lower the reflectivity R at the interface, and the greater the amount of light transmitted through the interface.
[0024]
Moreover, it is preferable that a protective layer contains a porous layer.
By including the porous layer, the viewing angle dependence of the emission color can be reduced by the light scattering effect. Further, since the refractive index can be reduced, it is easy to change the refractive index of the protective layer.
[0025]
Moreover, it is preferable that a porous layer is an airgel.
By constituting the porous layer from airgel, the refractive index can be made close to 1.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each member of the organic EL light emitting device of the present invention will be described.
1. Organic EL device
(1) Organic light emitting medium
The organic light-emitting medium can be defined as a medium including an organic EL light-emitting layer capable of EL emission by recombination of electrons and holes. Such an organic light-emitting medium can be configured, for example, by laminating the following layers on the anode layer as the first electrode.
(1) Organic EL light emitting layer
(2) Hole injection layer / organic EL light emitting layer
(3) Organic EL light emitting layer / electron injection layer
(4) Hole injection layer / organic EL light emitting layer / electron injection layer
(5) Organic semiconductor layer / organic EL light emitting layer
(6) Organic semiconductor layer / electron barrier layer / organic EL light emitting layer
(7) Hole injection layer / organic EL light emitting layer / adhesion improving layer
Among these, the configuration (4) is usually preferably used because it can obtain higher light emission luminance and is excellent in durability. Furthermore, an inorganic semiconductor layer and an inorganic insulating layer may be interposed between the organic light emitting medium and the electrode.
[0027]
(I) Material
Examples of the light emitting material in the organic light emitting medium include p-quarterphenyl derivatives, p-quinkphenyl derivatives, benzothiazole compounds, benzimidazole compounds, benzoxazole compounds, metal chelated oxinoid compounds, and oxadiazole compounds. , Styrylbenzene compounds, distyrylpyrazine derivatives, butadiene compounds, naphthalimide compounds, perylene derivatives, aldazine derivatives, pyrazirine derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, styrylamine derivatives, coumarin compounds, aromatic dimethylidin compounds, One kind alone or a combination of two or more kinds such as a metal complex having an 8-quinolinol derivative as a ligand, a polyphenyl compound, and the like can be given.
[0028]
Among these organic light-emitting materials, 4,4′-bis (2,2-di-t-butylphenylvinyl) biphenyl (DTBPBBi), 4,4′-bis ( 2,2-diphenylvinyl) biphenyl (DPVBi) and derivatives thereof are more preferred.
Further, an organic light emitting material having a distyrylarylene skeleton or the like is used as a host material, and the host material is doped with a strong fluorescent dye from blue to red as a dopant, for example, a coumarin-based material, or a fluorescent dye similar to the host It is also suitable to use together. More specifically, it is preferable to use the above-described DPVBi or the like as the host material and N, N-diphenylaminobenzene (DPAVB) or the like as the dopant.
In addition to the low molecular weight material (number average molecular weight of less than 10,000) as described above, it is also preferable to use a polymer material (number average molecular weight of 10,000 or more).
Specific examples include polyarylene vinylene and derivatives thereof (PPV), polyfluorene and derivatives thereof, and fluorene-containing copolymers.
[0029]
(Ii) thickness
Moreover, there is no restriction | limiting in particular about the thickness of an organic luminescent medium, For example, it is preferable that thickness is 5 nm-5 micrometers.
The reason for this is that when the thickness of the organic light emitting medium is less than 5 nm, the light emission luminance and durability may be reduced. On the other hand, when the thickness of the organic light emitting medium exceeds 5 μm, the value of the applied voltage increases. Because there is.
For these reasons, the thickness of the organic light emitting medium is more preferably 10 nm to 3 μm, and further preferably 20 nm to 1 μm.
[0030]
(2) Electrode
Hereinafter, the anode layer and the cathode layer as electrodes will be described. In the present invention, the first electrode and the second electrode correspond to both the anode layer and the cathode layer depending on the configuration of the organic EL element.
[0031]
(I) Anode layer
For the anode layer, it is preferable to use a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (for example, 4.0 eV or more). Specific examples thereof include indium tin oxide (ITO), indium zinc oxide (IZO), and tin oxide (SnO).₂), A transparent conductive material such as zinc oxide (ZnO), a single type of gold, platinum, palladium, or a combination of two or more types.
[0032]
Moreover, when using an anode layer as a 2nd electrode, it is preferable to make the said anode layer into a transparent electrode. Transparent electrode materials include ITO, IZO, and SnO.₂, ZnO and other transparent conductive materials. Among these, IZO (refractive index: 2.1) is more preferable because it is easy to adjust the refractive index when extracting light.
[0033]
When extracting light from the anode layer side, the refractive index of the anode layer is preferably 1.6 to 2.2, and more preferably 1.7 to 2.1.
[0034]
As a method for forming the anode layer, a vacuum deposition method, a sputtering method, an ion plating method, an electron beam deposition method, a CVD method (Chemical Vapor Deposition), an MOCVD method (Metal Oxide Chemical Vapor Deposition), a plasma CVD method, and the like. The method which can form into a film in the dry state is mentioned.
[0035]
The thickness of the anode layer is not particularly limited, but is preferably 10 to 1,000 nm, and more preferably 10 to 200 nm, for example.
[0036]
(Ii) Cathode layer
For the cathode layer, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture or a content thereof having a small work function (for example, less than 4.0 eV).
Specific examples thereof include sodium, sodium-potassium alloy, cesium, magnesium, lithium, aluminum-lithium alloy, magnesium-silver alloy and other alkali metals, alkaline earth metals, alloys containing these, aluminum, aluminum oxide, Indium, rare earth metals, mixtures of these metals or alloys and organic light-emitting medium materials, mixtures of these metals or alloys and organic electron transporting compounds, and mixtures of metal compounds and organic electron transporting compounds, alone or A combination of two or more types can be mentioned. Furthermore, it is a laminated body of an inorganic compound layer / electrically conductive compound, and an alkali metal compound or an alkaline earth metal compound may be used as the inorganic compound layer.
[0037]
Further, the film thickness of the cathode layer is not particularly limited as in the case of the anode layer, but is specifically preferably 10 to 1,000 nm, and more preferably 10 to 200 nm.
In particular, when the cathode layer is used as a light transmissive material, the following transparent cathode is preferable.
(1) Thin film or island film of 0.1 to 15 nm thickness of the metal
(2) The laminate using an inorganic compound layer
(3) Mixed layer of metal, alloy, metal compound and organic electron transport compound
A transparent conductive material may be further laminated for the purpose of imparting electrical conductivity to the above (1) to (3) or protecting from oxygen and water. About the refractive index of such a transparent cathode, it determines with the refractive index of the outer surface, A preferable value is 1.6-2.2, Furthermore, a preferable value is 1.7-2.1.
[0038]
2. Protective layer
The protective layer is a layer that protects the organic EL element from water and oxygen, and is an intermediate layer that is interposed between the first member and the second member as described above.
(1) Change in refractive index
The method for changing the refractive index of the protective layer is not particularly limited. As a method of changing the refractive index, (i) a method in which the component ratio of the material of the protective layer is continuously changed so that the refractive index is continuously different, and (ii) two or more layers having different refractive indexes. And (iii) a method in which minute holes are provided in the protective layer and the ratio of the holes is changed.
[0039]
Specific examples of the protective layer obtained by the method (i) include SiO._xN_yAlO_xN_y, SiAlO_xN_yEtc. Of these, SiO_xN_yIs a high refractive index SiO_xAnd low refractive index SiN_yThese ratios are calculated from the proportion of SiH as the raw material._FourAnd N₂The refractive index is changed by continuously changing the ratio. For example, if x is increased in the range of 0 <x ≦ 2 and 0 <y ≦ 3/2, a low refractive index is obtained. If y is increased, a high refractive index is obtained, and a value of 1.5 to 2.3 is arbitrarily set. Can be set. SiO_xN_yCan be formed by, for example, a CVD method or the like, similarly to the method of forming the anode. For example, when the film is formed by the CVD method, it is changed by adjusting the gas flow rate. Further, when F is added, a low refractive index is obtained. For example, SiOF (F-added SiO_x), F-added AlO_x, F-added SiO_xN_yAnd a refractive index of 1.3 to 1.5 can be realized.
[0040]
As a specific example of the protective layer obtained by the method (ii), SiO 2 is formed on the first member._xN_y/ SiO_x, SiO_xN_y/ Transparent resin, SiO_xN_y/ Sealing liquid or transparent resin / sealing liquid laminated.
In this case, the refractive index of each layer is preferably smaller than that of the first member and larger than that of the second member, and more preferably smaller from the first member toward the second member.
[0041]
(2) Material
Examples of the material for the protective layer include transparent resins, sealing liquids, and transparent inorganic substances.
In the transparent resin and the sealing liquid, it is preferable to use an aromatic ring-containing compound, a fluorene skeleton-containing compound, a bromine-containing compound, or a sulfur-containing compound as a main component, or to add as a refractive index adjusting agent. This is because such a compound has a relatively high refractive index value and can flexibly adjust the refractive index of the protective layer as necessary.
[0042]
Furthermore, it is also preferable to add a compound having a high refractive index, for example, a metal compound such as alkoxytitanium (dimethoxytitanium or diethoxytitanium) or the like in the transparent resin or the sealing liquid constituting the protective layer.
Thus, by adding alkoxy titanium or the like, the refractive index of the transparent resin or the sealing liquid can be further increased.
[0043]
Examples of the transparent resin that can be used as the material for the protective layer include the following compounds.
Polyphenyl methacrylate (refractive index: 1.57)
Polyethylene terephthalate (refractive index: 1.58)
Poly-o-chlorostyrene (refractive index: 1.61)
Poly-o-naphthyl methacrylate (refractive index: 1.61)
Polyvinyl naphthalene (refractive index: 1.68)
Polyvinylcarbazole (refractive index: 1.68)
Fluorene skeleton-containing polyester (refractive index: 1.61-1.64)
[0044]
Moreover, when using transparent resin for the material of a protective layer, it is also preferable to comprise this from ultraviolet curable resin, visible light curable resin, thermosetting resin, or an adhesive using them. Specific examples thereof include LUX TRACK LCR0278, 0242D (all manufactured by Toa Gosei Co., Ltd.), TB3102 (epoxy system: manufactured by ThreeBond Co., Ltd.), Benefix VL (acrylic system: manufactured by Adel Co., Ltd.), etc. Commercial products.
[0045]
Further, as a transparent inorganic material that can be used as a material constituting the protective layer, SiO 2₂, SiO_x, SiO_xN_y, Si_ThreeN_Four, Al₂O_ThreeAlO_xN_yTiO₂TiO_x, SiAlO_xN_yTiAlO_xTiAlO_xN_y, SiTiO_x, SiTiO_xN_yEtc.
In addition, when using a transparent inorganic material for the material of the protective layer, it is preferable to form the film at a low temperature (100 ° C. or less) and at a low film formation rate so as not to deteriorate the organic EL element. A method such as sputtering, vapor deposition, or CVD is preferred.
Moreover, it is preferable that these transparent inorganic substances are amorphous because they have a high blocking effect on moisture, oxygen, low-molecular monomers, and the like, and control deterioration of the organic EL element.
[0046]
Further, examples of the sealing liquid that can be used as a material constituting the protective layer include fluorinated hydrocarbons and oligomers of fluorinated olefins.
[0047]
(3) Refractive index
The refractive index of the protective layer is particularly preferably 1 to 2.3, and more preferably 1 to 1.9.
[0048]
(4) Thickness
Moreover, there is no restriction | limiting in particular about the thickness of a protective layer, For example, it is preferable to set thickness to 10 nm-1 mm.
The reason for this is that when the thickness of the protective layer is less than 10 nm, the amount of moisture and oxygen permeation may increase. On the other hand, when the thickness of the protective layer exceeds 1 mm, the film thickness increases as a whole and the groove type This is because there are cases in which it cannot be realized.
For this reason, the thickness of the protective layer is more preferably 10 nm to 100 μm.
[0049]
(5) Porous layer
The protective layer preferably includes a porous layer from the viewpoint of a low refractive index. Examples of components of such a porous layer include aerogels and xerogels.
As an example, a porous airgel layer will be described in detail. The airgel layer is obtained by converting silica gel obtained by hydrolysis and polymerization reaction of alkoxysilane into alcohol or CO2.₂It can be obtained by drying in a supercritical state above the critical point of the solvent in the presence of the solvent. The refractive index of the airgel layer is 1.03 to 1.4.
[0050]
3. Color conversion layer
The color conversion layer absorbs light emitted from the organic EL element and converts it into a desired light emission color in the case of a phosphor layer having a function of emitting longer wavelength fluorescence or absorbs light emitted from the organic EL element. It may be a color filter. For example, a phosphor layer may be used to convert blue light into green light or red light, or a color filter may be used to extract red, green, and blue light from white light, improving color purity. Therefore, a color filter or a phosphor layer may be used for incident light of the three primary colors of light.
The color conversion layer may be laminated by combining a color filter and a phosphor layer in order to improve color reproducibility, but this laminate may be used as the color conversion layer.
[0051]
Each color conversion layer is preferably arranged corresponding to the position of the light emitting region of the organic EL element, for example, the intersection of the first electrode and the second electrode.
With this configuration, when the organic EL light emitting layer emits light at the intersection of the first electrode and the second electrode, each color conversion layer receives the light and emits light of different colors (wavelengths). Can be taken out.
In this case, in particular, when the organic EL element emits blue light and can be converted into green and red light emission by the color conversion layer, even one organic EL element has blue, green, and red light. Since three primary colors of light can be obtained and full color display is possible, it is preferable.
[0052]
(1) Material
When the color conversion layer is composed of a phosphor layer, the material is not particularly limited. For example, the color conversion layer is composed of only a fluorescent dye and a resin, or a fluorescent dye. And / or a solid state dissolved or dispersed in a binder resin.
When the color conversion layer is made of a color filter, the material is not particularly limited. For example, the color conversion layer is made of a color pigment, or a resin and a color pigment, and the resin and the color pigment are color pigments. Can be obtained by dissolving or dispersing in a pigment resin and / or a binder resin.
[0053]
A specific fluorescent dye will be described. As a fluorescent dye for converting purple light emission from near ultraviolet light to blue light emission in an organic EL element, 1,4-bis (2-methylstyryl) benzene (Bis-MBS), trans Examples thereof include stilbene dyes such as -4,4'-diphenylstilbene (DPS) and coumarin dyes such as 7-hydroxy-4-methylcoumarin (coumarin 4).
[0054]
As for the fluorescent dye in the case where blue, blue-green or white light emission in an organic EL element is converted into green light emission, for example, 2,3,5,6-1H, 4H-tetrahydro-8-trifluoromethylquinolyl Dino (9,9a, 1-gh) coumarin (coumarin 153), 3- (2'-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6), 3- (2'-benzimidazolyl) -7-N, N- Examples thereof include coumarin dyes such as diethylaminocoumarin (coumarin 7), other basic coumarin dye-based dyes such as basic yellow-51, and naphthalimide dyes such as solvent yellow-11 and solvent yellow-116.
[0055]
In addition, regarding a fluorescent dye in the case where light emission from blue to green or white light emission in an organic EL element is converted into light emission from orange to red, for example, 4-dicyanomethylene-2-methyl-6- (p -Cyanine dyes such as -dimethylaminostyryl) -4H-pyran (DCM), 1-ethyl-2- (4- (p-dimethylaminophenyl) -1,3-butadienyl) -pyridinium perchlorate Examples include pyridine dyes such as (pyridine 1), rhodamine dyes such as rhodamine B and rhodamine 6G, and oxazine dyes.
[0056]
Furthermore, various dyes (direct dyes, acid dyes, basic dyes, disperse dyes, etc.) can also be selected as fluorescent pigments if they are fluorescent.
In addition, fluorescent pigments are kneaded in advance into pigment resins such as polymethacrylates, polyvinyl chloride, vinyl chloride vinyl acetate copolymers, alkyd resins, aromatic sulfonamide resins, urea resins, melanin resins, and benzoguanamine resins. It may be converted.
[0057]
On the other hand, the binder resin is preferably a transparent material (light transmittance in visible light is 50% or more). Examples thereof include transparent resins (polymers) such as polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose.
[0058]
Preferable examples of the pigment used for the color filter include phthalocyanine, quinacridone, anthraquinone, pyrrolo-pyrrole and the like.
[0059]
A photosensitive resin to which a photolithography method can be applied is also selected in order to separate and arrange the color conversion layers in a plane. For example, photocurable resist materials having reactive vinyl groups such as acrylic acid, methacrylic acid, polyvinyl cinnamate, and ring rubber are listed. Moreover, when using a printing method, the printing ink (medium) using transparent resin is selected. For example, polyvinyl chloride resin, melamine resin, phenol resin, alkyd resin, epoxy resin, polyurethane resin, polyester resin, maleic acid resin, polyamide resin monomer, oligomer, polymer, or polymethyl methacrylate Transparent resins such as polyacrylate, polycarbonate, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose and the like can be used.
[0060]
(2) Formation method
In the case where the color conversion layer is mainly composed of a fluorescent dye or a dye, it is preferable to form a film by vacuum deposition through a mask from which a desired color conversion layer pattern can be obtained.
On the other hand, when the color conversion layer is made of a fluorescent dye or dye pigment and a resin, the fluorescent dye or dye pigment, the resin and an appropriate solvent are mixed, dispersed or solubilized to form a liquid, and the liquid is The film is formed by a method such as coating, roll coating, or casting, and then patterned into a desired color conversion layer pattern by a photolithography method, or patterned into a desired pattern by a method such as ink jet or screen printing. A conversion layer is preferably formed.
[0061]
(3) Thickness
The thickness of the color conversion layer is not particularly limited as long as it sufficiently receives (absorbs) light emitted from the organic EL element and does not hinder the function of color conversion. For example, the thickness of the color conversion layer is 10 nm to 1,000 μm. The thickness is preferably 0.1 μm to 500 μm, more preferably 2 μm to 100 μm.
This is because when the thickness of the color conversion layer is less than 10 nm, the mechanical strength may be reduced or it may be difficult to laminate. On the other hand, when the thickness of the color conversion layer exceeds 1 mm, the light transmittance is remarkably lowered, the amount of light that can be taken out to the outside is reduced, or it is difficult to make the organic EL light emitting device thinner. .
[0062]
(4) Refractive index
When the color conversion layer is the second member, the refractive index of the color conversion layer is preferably smaller than the refractive indexes of the first member and the protective layer. The refractive index of the color conversion layer is preferably 1.5 to 1.8, and more preferably 1.5 to 1.7.
When the color conversion layer is the first member, the refractive index of the color conversion layer is preferably larger than the refractive indexes of the protective layer and the support substrate. The refractive index of the color conversion layer is preferably 1.6 to 2.3, and more preferably 1.7 to 2.1.
[0063]
5. Sealing member
The sealing member is preferably provided so as to cover at least the light emitting region of the organic EL display device in order to prevent moisture from entering the organic light emitting medium.
As such a sealing member, the same kind of material as that of the support substrate can be used. In particular, a glass plate or a ceramic substrate having a high moisture or oxygen blocking effect can be used. Further, the form of the sealing member is not particularly limited, and for example, a plate shape or a cap shape is preferable. For example, when it is plate-shaped, the thickness is preferably set to a value within the range of 0.01 to 5 mm.
Further, it is preferable that the sealing member is provided with a groove or the like in a part of the support substrate and is press-fitted into the groove, or is fixed to a part of the support substrate using a photo-curing adhesive or the like. It is also preferable to fix.
[0064]
When the sealing member is the second member, the refractive index of the sealing member is preferably smaller than the refractive indexes of the first member and the protective layer. The refractive index of the sealing member is preferably 1.4 to 1.8, and more preferably 1.4 to 1.6.
[0065]
6). Support substrate
The support substrate in the organic EL light emitting device is a member for supporting the organic EL element, the protective layer, and the like, and therefore it is preferable that the support substrate is excellent in mechanical strength and dimensional stability.
Examples of such a support substrate include a support substrate made of an inorganic material, such as a glass plate, a metal plate, and a ceramic plate. Preferred inorganic materials include glass material, silicon oxide, aluminum oxide, titanium oxide, and oxide. Yttrium, germanium oxide, zinc oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, lead oxide, sodium oxide, zirconia, sodium oxide, lithium oxide, boron oxide, silicon nitride, soda lime glass, barium strontium Examples thereof include contained glass, lead glass, aluminosilicate glass, borosilicate glass, and barium borosilicate glass.
Preferred organic materials constituting the support substrate include polycarbonate resin, acrylic resin, vinyl chloride resin, polyethylene terephthalate resin, polyimide resin, polyester resin, epoxy resin, phenol resin, silicone resin, fluororesin, polyvinyl alcohol Examples of such resins include polyvinyl resins, polyvinyl pyrrolidone resins, polyurethane resins, epoxy resins, cyanate resins, melamine resins, maleic resins, vinyl acetate resins, polyacetal resins, and cellulose resins.
[0066]
When the support substrate is the second member, the refractive index of the support substrate is preferably smaller than the refractive indexes of the first member and the protective layer. The refractive index of the support substrate is preferably 1.4 to 1.8.
In addition, with such a support substrate, reflection on the substrate surface can be suppressed even when EL light emission is taken out through the support substrate.
For reference, the preferable refractive index of the substrate is as follows.
Methyl methacrylate resin: 1.49
Silicon oxide (SiO₂: 1.54
Boron oxide (B₂O_Three): 1.77
Glass: 1.49-1.50
Tetrafluoroethylene resin: 1.49
[0067]
[Embodiment 1]
FIG. 4 is a schematic view showing one embodiment of the organic EL light emitting device of the present invention. In the drawings, the same reference numerals denote the same members, and descriptions thereof are omitted.
The organic EL light emitting device 100 includes a TFT 6 embedded in an electrical insulating film (including a gate insulating film) 4, an interlayer insulating film 8, an organic EL element 16, a contact hole 18, a protective layer 20, a color conversion on a support substrate 2. A layer 22 and a sealing member 24 are provided. The organic EL element 16 sandwiches the organic light emitting medium 12 between the first electrode 10 and the second electrode 14. The TFT 6 and the organic EL element 16 are electrically connected by the contact hole 18. The arrows in the figure indicate the direction in which light is extracted.
The refractive index of the second electrode 14 is n1, the refractive index of the color conversion layer 22 is n2, and n1> n2. The refractive index at an arbitrary position x in the protective layer 20 is nx, and the refractive index at an arbitrary position y is ny. The position y is a position closer to the color conversion layer 22 than the position x in the thickness direction of the protective layer 20 sandwiched between the second electrode 14 and the color conversion layer 22. In this embodiment, the refractive index of the protective layer 20 decreases from n1 to n2 from the second electrode 14 toward the color conversion layer 22. Therefore, there is at least one combination of nx and ny that satisfies the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx |.
[0068]
FIG. 5 is a schematic view showing another embodiment of the organic EL light emitting device of the present invention. In the organic EL light emitting device 200 shown in this figure, the color conversion layer 22 is provided outside the sealing member 24 (opposing member).
In the organic EL light emitting device 200, the refractive index of the second electrode 14 is n1, the refractive index of the sealing member 24 is n2, and n1> n2. The refractive index at an arbitrary position x in the protective layer 20 is nx, and the refractive index at an arbitrary position y is ny. The position y is a position closer to the sealing member 24 than the position x in the thickness direction of the protective layer 20 sandwiched between the second electrode 14 and the sealing member 24. In this embodiment, the refractive index of the protective layer 20 decreases from n1 to n2 from the second electrode 14 toward the sealing member 24. Therefore, there is at least one combination of nx and ny that satisfies the relationship of | n2-ny | <| n2-nx | and | n1-ny |> | n1-nx |.
[0069]
【Example】
[Example 1]
A glass substrate with a transparent electrode (Corning 7059) having a length of 25 mm, a width of 75 mm, and a thickness of 1.1 mm was cleaned with isopropyl alcohol and UV, and then the substrate was placed in a vacuum deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.). Fixed to the holder. The transparent electrode was ITO and the film thickness was 130 nm.
[0070]
Subsequently, copper phthalocyanine (CuPC) and 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD) are used as hole injection materials on a heating board made of molybdenum in a vacuum deposition apparatus. 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVBi) as an organic light emitting material, tris (8-quinolinol) aluminum (Alq) as an electron injection material, and Li as an alkali metal source. Further, an Al alloy (Si content: 5% by weight) as a material for the lower electrode (cathode) was mounted on the heating board.
[0071]
In this state, the vacuum degree of the vapor deposition apparatus is 655 × 10.^-7The pressure was reduced to Pa, and the layers were laminated by a single vacuum drawing without breaking the vacuum state in the middle from the cathode to the formation of the hole injection layer so that the following deposition rate and film thickness were obtained. During the deposition of Alq, the Li source was also heated to form a mixture of the electron injection material and the alkali metal at a molar ratio of 1: 1.
CuPC: Deposition rate of 0.1 to 0.3 nm / sec. , Film thickness 30nm
NPD: Deposition rate of 0.1 to 0.3 nm / sec. , Film thickness 40nm
DPVBi: Deposition rate of 0.1 to 0.3 nm / sec. , Film thickness 50nm
Alq: Li: Deposition rate 0.1 to 0.3 nm / sec. , Film thickness 20nm
Al: Si alloy: Deposition rate of 1.0 to 2.0 nm / sec. , Film thickness 10nm
[0072]
Next, the substrate was moved to a sputtering apparatus, and IZO (refractive index 2.1) of the upper electrode (anode) was formed by sputtering and laminated to 200 nm to produce an organic EL element.
[0073]
Next, as a transparent inorganic film on the upper electrode of the organic EL element, SiO_xN_y(O / O + N = 50%: Atomic ratio) (refractive index: 1.70) was formed to a thickness of 300 nm by low-temperature plasma CVD. The gas source at this time is silane, N₂, O₂The RF output was 30 W. Further, Benefix VL (acrylic visible light curable transparent adhesive as transparent resin: manufactured by Adel Co., Ltd., refractive index 1.57) is cast, and a glass substrate (refractive index 1.53) is used as a sealing member. The organic EL display device was manufactured by stacking and irradiating visible light from a sealing member with a halogen lamp to cure the adhesive. Where SiO_xN_yThe laminate of the Benefix VL layer is a protective layer.
[0074]
Next, a voltage of DC 12 V is applied between the upper electrode (anode, IZO) and the lower electrode (cathode, Al: Si) of the obtained organic EL display device through an active matrix (transistor) circuit. Was emitted.
When the luminance was measured using a color difference meter CS1000 (manufactured by Minolta Co., Ltd.), it was 195 cd / m.²In addition, the efficiency was 4.6 cd / A. Further, the CIE chromaticity coordinates for the obtained blue (blue) light emission are X = 0.15, Y = 0.16, and the change of the chromaticity coordinates is 0 in the range of the viewing angle of −70 ° to 70 °. It was confirmed that there was almost no less than 0.01. Here, the angle when the luminescent color was viewed from the front was defined as 0 °, and the angle when the luminescent color was viewed obliquely was defined as the viewing angle.
[0075]
[Comparative Example 1]
In Example 1, SiO_xN_yAn organic EL display device was produced in the same manner as in Example 1 except that the film was not formed, and the performance was measured. As a result, the efficiency was 3.8 cd / A, which was inferior to Example 1.
[0076]
[Comparative Example 2]
In Example 1, the protective layer is SiO_xN_yAn organic EL display device was produced in the same manner as in Example 1 except that the transparent resin and the sealing member were not used. In addition, the performance of the obtained device₂Was measured in the same manner as in Example 1. As a result, the efficiency was as low as 3.6 cd / A, and the chromaticity measured from the front was (0.16, 0.18), but when observed obliquely from 30 °, the chromaticity was (0.13, 0.13). 0.12), and the viewing angle characteristic was also inferior to that of Example 1.
[0077]
[Example 2]
In Example 1, SiO_xN_yThe composition of SiO at the interface with the upper electrode_0.1N_1.0SiO at the interface with the transparent resin_1.7N_0.1As described above, an organic EL display device was fabricated in the same manner as in Example 1 except that the amount ratio of the source gas used for CVD was controlled. SiO_xN_yThe refractive index was 2.1 at the interface with the upper electrode and 1.6 at the interface with the transparent resin. Si gas source is silane, and nitrogen gas source is N.₂As an oxygen gas source, O₂The RF output is 50 W and the ratio of oxygen flow rate to nitrogen flow rate (O₂: N₂) Was first set to 1:12, and gradually changed to 20: 1.
When the performance of the obtained device was measured in the same manner as in Example 1, it was improved to 5.0 cd / A compared with the comparative example.
[0078]
[Example 3]
A tetramethoxysilane oligomer (trade name: Methyl silicate 51, manufactured by Korto Co., Ltd.) and methanol on a glass substrate with a transparent electrode (Corning 7059) (refractive index 1.53) having a length of 25 mm, a width of 75 mm, and a thickness of 1.1 mm. A solution prepared by mixing A at a mass ratio of 47:81 and an alkoxysilane solution prepared by mixing water, 28 mass% ammonia water, and methanol B mixed at a mass ratio of 50: 1: 81 at a mass ratio of 16:17. 700min^-1Spin coating was performed at a rotation speed of 10 seconds. Subsequently, after alkoxysilane was gelled, it was immersed in a curing solution of water: 28% by mass ammonia water: methanol = 162: 4: 640 (mass ratio) and cured at room temperature for one day and night. Next, the thin gel compound thus cured was dipped in a 10% by mass isopropanol solution of hexamethyldisilazane for hydrophobization treatment. The thin-film gel compound thus formed on the glass substrate was immersed in isopropanol and washed, and then placed in a high-pressure vessel. The inside of the high-pressure vessel was filled with liquefied carbon dioxide, and conditions of 80 ° C. and 16 MPa. And a silica airgel layer having a film thickness of 30 μm. When the refractive index of this layer was measured, it was as small as 1.1.
[0079]
Next, on the silica airgel layer, SiO_1.6F_0.1Was provided with a film thickness of 100 nm by plasma CVD. Source gases include silane and O₂, F₂Was used to control the quantity ratio. The refractive index of this layer was 1.41. Furthermore, continuously F₂The flow rate of N, then N₂The flow rate of SiOF / SiO_x~ SiO_xN_yAnd the refractive index changed. Thus, a protective layer was formed. Its structure is airgel / SiOF / SiO_x~ SiO_xN_yAnd SiO_xN_yThe surface composition was x = 0.1 and y = 1.0. SiO_xN_yThe refractive index of was 2.1.
[0080]
Next, after providing a transparent electrode (IZO) (refractive index 2.1) with a film thickness of 100 nm on the protective layer, each organic layer was provided in the same manner as in Example 1. Further, a Li fluoride layer 1 nm / Al 100 nm was provided thereon as a cathode to produce an organic EL display device. When the performance of the obtained device was evaluated in the same manner as in Example 1, a high efficiency of 7.1 cd / A was obtained.
[0081]
【The invention's effect】
According to the present invention, it is possible to provide an organic EL light emitting device that can prevent a decrease in light emission amount due to an interference effect caused by internal reflection of light, extract more light to the outside, and has excellent viewing angle characteristics. .
[Brief description of the drawings]
FIG. 1a is a diagram showing an example of a relative relationship of refractive indexes according to the present invention.
FIG. 1b is a diagram showing combinations of nx and ny that are not in a relationship defined by the present invention.
FIG. 1c is a diagram showing another combination of nx and ny that is not related to the present invention.
FIG. 2a is a diagram showing a mode of a linear change in the refractive index of a protective layer.
FIG. 2b is a diagram showing an aspect of a curved change in the refractive index of the protective layer.
FIG. 2c is a diagram showing a mode of stepwise change in the refractive index of the protective layer.
FIG. 2d is a diagram showing another stepwise change of the refractive index of the protective layer.
3a is a schematic view showing an embodiment of an organic EL light emitting device according to the invention of claim 2. FIG.
3b is a schematic view showing another embodiment of the organic EL light emitting device according to the invention of claim 2. FIG.
3c is a schematic view showing an embodiment of an organic EL light emitting device according to the invention of claim 3. FIG.
FIG. 3d is a schematic view showing one embodiment of an organic EL light emitting device according to the invention of claim 4;
FIG. 3e is a schematic view showing one embodiment of an organic EL light emitting device according to the invention of claim 5.
FIG. 4 is a schematic view showing one embodiment of an organic EL light emitting device of the present invention.
FIG. 5 is a schematic view showing another embodiment of the organic EL light emitting device of the present invention.
[Explanation of symbols]
100,200 Organic EL light emitting device
2 Support substrate (second member)
10 First electrode
12 Organic light-emitting media
14 Second electrode (first member)
16 Organic EL elements
20 Protective layer
22 color conversion layer (first member) (second member)
24 Sealing member (second member)
n1 Refractive index of the second electrode
n2 refractive index of sealing member or color conversion layer
nx Refractive index at the x position of the protective layer
ny The refractive index at the y position of the protective layer

Claims (8)

The first member, the protective layer, and the second member are provided in this order in the light extraction direction,
By increasing or decreasing the refractive index of the protective layer from the first member toward the second member, the refractive index difference at the interface between the protective layer and the first member, the protective layer and the second member Reduce the refractive index difference at the interface of the member,
The refractive index of the first member is n1, the refractive index of the second member is n2, which is different from n1, the refractive index at the x position of the protective layer is nx, and the first member and the When the refractive index at the y position closer to the second member than the x position of the protective layer is ny in the thickness direction of the protective layer sandwiched between the second members, | n2-ny | <| n2- nx |, and, | n1-ny |> | n1-nx | refractive index nx and ny satisfy the relationship exists at least one set,
The organic electroluminescent light-emitting device in which the said protective layer contains a porous layer . The first electrode, the organic light emitting medium, the second electrode, the protective layer, and the color conversion layer are provided in this order in the light extraction direction.
By increasing or decreasing the refractive index of the protective layer from the second electrode toward the color conversion layer, the refractive index difference at the interface between the protective layer and the second electrode, and the protective layer and the color conversion layer Reduce the refractive index difference at the interface,
The refractive index of the second electrode is n1, the refractive index of the color conversion layer is n2, which is different from n1, the refractive index at the x position of the protective layer is nx, the second electrode and the color When the refractive index at the y position closer to the color conversion layer than the x position of the protective layer is ny in the thickness direction of the protective layer sandwiched between the conversion layers, | n2-ny | <| n2-nx | and, | n1-ny |> | n1-nx | refractive index nx and ny satisfy the relationship exists at least one set,
The organic electroluminescent light-emitting device in which the said protective layer contains a porous layer . The first electrode, the organic light emitting medium, the second electrode, the protective layer, and the sealing member are provided in this order in the direction of extracting light,
By increasing or decreasing the refractive index of the protective layer from the second electrode toward the sealing member, the refractive index difference at the interface between the protective layer and the second electrode, and the protective layer and the sealing member Reduce the refractive index difference at the interface,
The refractive index of the second electrode is n1, the refractive index of the sealing member is n2, which is different from n1, the refractive index at the x position of the protective layer is nx, and the second electrode and the sealing member When the refractive index at the y position closer to the sealing member than the x position of the protective layer is ny in the thickness direction of the protective layer sandwiched between the stop members, | n2-ny | <| n2-nx | and, | n1-ny |> | n1-nx | refractive index nx and ny satisfy the relationship exists at least one set,
The organic electroluminescent light-emitting device in which the said protective layer contains a porous layer . The first electrode, the organic light emitting medium, the second electrode, the protective layer, and the support substrate are provided in this order in the direction of extracting light,
The refractive index of the protective layer increases or decreases from the second electrode toward the support substrate, so that the refractive index difference at the interface between the protective layer and the second electrode and the interface between the protective layer and the support substrate are increased. Reduce the refractive index difference,
The refractive index of the second electrode is n1, the refractive index of the support substrate is n2, which is different from n1, the refractive index at the x position of the protective layer is nx, and the second electrode and the support substrate When the refractive index at the y position closer to the support substrate than the x position of the protective layer is ny in the thickness direction of the protective layer sandwiched between | n2-ny | <| n2-nx | n1-ny |> | n1- nx | refractive index nx and ny satisfy the relationship exists at least one set,
The organic electroluminescent light-emitting device in which the said protective layer contains a porous layer . The first electrode, the organic light emitting medium, the second electrode, the color conversion layer, the protective layer, and the support substrate are provided in this order in the direction of extracting light,
Refractive index of the protective layer, by increases or decreases from the color conversion layer toward the support substrate, and the refractive index difference at the interface between the protective layer and the color conversion layer, bending at the interface of the support substrate and the protective layer folding Reduce the rate difference,
The refractive index of the color conversion layer is n1, the refractive index of the support substrate is n2, which is different from n1, and the refractive index at the x position of the protective layer is nx, and is sandwiched between the color conversion layer and the support substrate. In the thickness direction of the protective layer, when the refractive index at the y position closer to the support substrate than the x position of the protective layer is ny, | n2-ny | <| n2-nx | and | n1- ny |> | n1-nx | refractive index nx and ny satisfy the relationship exists at least one set,
The organic electroluminescent light-emitting device in which the said protective layer contains a porous layer .   The absolute value of the refractive index difference at the interface between the protective layer and the first member and the absolute value of the refractive index difference at the interface between the protective layer and the second member are less than 0.2. 2. The organic electroluminescence light emitting device according to 1.   It is n1> n2 and is nx> ny, The organic electroluminescent light-emitting device as described in any one of Claims 1-6. The organic electroluminescence light emitting device according to any one of claims 1 to 7 , wherein the porous layer is an airgel.

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