JP2007035313A - Light take-out film, translucent element with light take-out film, and electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light take-out film used for improving light take out efficiency of an electroluminescent element, hardly inducing fine crack and exfoliation on a transparent electrode, and to provide an electroluminescent element having high light take-out efficiency with little dark spot and shortening of life. <P>SOLUTION: The light take-out film composed of a single layer film or a lamination film of not less than two layers is used for the electroluminescent element. At least one layer out of the layers constituting the light take-out film has light dispersing function, and hardness of the light take-out film measured by nano-indentation method is 0.05 to 20 GPa. The electroluminescent element is formed by laminating a translucent element 4, the above light take-out films 5A, 5B, a first electrode layer 3, an electroluminescent layer 2, and a second electrode layer 1 in this sequence. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light extraction film used for an electroluminescence (EL) element. The present invention also relates to a light-transmitting film-equipped translucent body and an electroluminescence element having such a light-extracting film.

  In general, in an electroluminescent element used in an electroluminescence (EL) display, holes injected from an anode and electrons injected from a cathode are recombined in an electroluminescent layer, and an emission center is excited by the recombination energy. Have a light emission principle of emitting light.

  FIG. 2 is a schematic cross-sectional view showing a conventional general electroluminescence element, in which an electrode layer (cathode) 1, an electroluminescence layer 2, a transparent electrode layer (anode) 3, and a transparent body (transparent substrate) 4. Are stacked in this order.

  In an electroluminescence display, it is preferable that light emitted from the electroluminescence layer is efficiently extracted, but light having a large emission angle (light emitted at an angle close to the critical angle) is emitted from the emitted light. The light is totally reflected at the interface between the transparent substrate and air and travels while totally reflecting the inside of the transparent substrate in the plane direction. There is also guided light that is totally reflected at the interface between the transparent electrode layer and the transparent substrate and travels in the plane direction inside the transparent electrode or inside the transparent electrode and the electroluminescent layer. These guided light is absorbed inside the device. It is attenuated and cannot be taken out.

  Conventionally, because of these guided lights, the light extraction efficiency extracted from the transparent substrate of the electroluminescence element (the ratio of the light emitted from the electroluminescence layer extracted outside the electroluminescence element) is as low as about 20%. It was.

  Therefore, a technique for forming a layer or a light extraction film for improving the light extraction efficiency to the outside between the transparent substrate and the transparent electrode layer has been developed.

  For example, Patent Literature 1 describes an electroluminescence element having a light scattering portion on a light extraction surface. Patent Document 2 describes an electroluminescence element in which an intermediate layer having a refractive index smaller than that of a transparent electrode and larger than that of the transparent substrate is formed between the transparent electrode and the transparent substrate. In Patent Document 3, a transparent layer having a refractive index equal to or higher than that of the light-emitting layer and having a region that substantially disturbs the reflection / scattering angle of light inside is described as light from the transparent electrode. An electroluminescence element formed adjacent to the extraction surface side is described.

However, these techniques have a problem that fine cracks and peeling occur in the electrodes, and there is a drawback that the cracks and peeling cause dark spots and a reduction in life.
Japanese Patent No. 2931111 JP 2004-134158 A JP 2004-296429 A

  The present invention is a light extraction film used for improving the light extraction efficiency of an electroluminescent device, and does not induce fine cracks or peeling of the transparent electrode, has high light extraction efficiency, dark spots, and reduced lifetime It is an object of the present invention to provide a light extraction film capable of realizing an electroluminescent element with a small amount of light, a light-transmitting body with a light extraction film using the light extraction film, and an electroluminescent element.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used an optical extraction film having a hardness of 0.05 to 20 GPa according to the nanoindentation method, so that an electroluminescence element with less fine cracks and peeling of the electrode Has been found to be stable.

The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.
[1] A light extraction film composed of a single layer film or a laminated film of two or more layers used in an electroluminescence element, and at least one of the layers constituting the light extraction film is a layer having a light scattering function. A light extraction film, wherein the light extraction film has a hardness by a nanoindentation method of 0.05 to 20 GPa.
[2] The layer according to [1], wherein at least one of the layers constituting the light extraction film is a layer mainly composed of an inorganic oxide having a refractive index of 1.05 to 1.4. Light extraction film.
[3] The light extraction film according to [1] or [2], wherein at least one of the layers constituting the light extraction film is a layer having a refractive index of 1.43 to 2.2.
[4] The light extraction film according to [1] to [3], which has a thickness of 50 nm to 20 μm.
[5] A translucent body with a light extraction film, wherein the light extraction film according to [1] to [4] is formed on the translucent body.
[6] An electroluminescence element in which a light transmitting body, a light extraction film, a first electrode layer, an electroluminescence layer, and a second electrode layer are laminated in this order, and the light extraction film is [1] to [ 4] The electroluminescent element characterized by being the light extraction film | membrane as described in 4].

  According to the present invention, by using the light extraction film having a hardness of 0.05 to 20 GPa according to the nanoindentation method, an electroluminescent element with few fine cracks and peeling of the electrode can be stably produced. This is due to the use of a light extraction film having a hardness of 0.05 to 20 GPa by the nanoindentation method, so that the strain generated in each film or at the film interface in the lamination process of the electroluminescence element or the crack caused by this distortion This is thought to be due to the ability to reduce damage such as pinholes.

According to the present invention,
-Durability of elements (dark spots, reduction of lifetime reduction factors) is improved.
-It is possible to reduce changes in emission color and luminance with respect to the viewing angle caused by light interference.
-The accuracy to the uniformity of the film thickness of each layer in the electroluminescence element is eased, and the screen of the element, mass productivity, and cost reduction become easy.
Based on the above effects, it is possible to easily realize a highly efficient electroluminescence element with high light extraction efficiency.

  According to such an electroluminescent element of the present invention, a high luminance can be obtained with a low current amount, and thus a long-life element can be provided. In addition, since high luminance is obtained, an electroluminescence element useful as a light emitting body, such as a display application, an illumination application, or the like.

  The electroluminescence device of the present invention is a self-luminous device and can be used for a field emission display or a plasma display having a translucent material, and its industrial utility is very large.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. The content of is not specified.

[Light extraction film]
The light extraction film of the present invention is a light extraction film composed of only a single layer film or a laminated film of two or more layers used for an electroluminescence element, and is at least one of the layers constituting the light extraction film. A layer is a layer which has a light-scattering function, and the hardness by a nanoindentation method is 0.05-20GPa, It is characterized by the above-mentioned.

  The light extraction film referred to in the present invention is, for example, a translucent body (transparent substrate) of an electroluminescence element and an electrode layer (an electrode layer closer to the translucent body of two electrodes, and is usually an anode) (Hereinafter, sometimes referred to as “first electrode layer”)), and at least one layer of the film is a layer having a light extraction function.

  The hardness by the nanoindentation method is measured for a light extraction film composed of all layers existing between the translucent body and the first electrode layer, and has a light extraction function. As will be described later, it has a function of performing multiple scattering of emitted light by Mie scattering.

<Layer with light scattering function>
The layer having the light scattering function is a layer having a function of multiply scattering the emitted light by Mie scattering. By this light scattering function, the guided light in the thin film including the electroluminescence layer or the light oozing out of the guided light is emitted. It can be scattered in the light extraction direction.

  In a layer having a light scattering function, in order to efficiently perform multiple scattering, a scatterer (for example, a particle) or a scattering shape (for example, an uneven shape), a refractive index with a scatterer or a matrix around the scattering shape. It is necessary to optimally adjust the difference and the size of the scatterer or scattering shape. Here, the scatterer means a particle having a refractive index different from that of the periphery, such as particles dispersed in a matrix such as a resin.

  For example, the distance between the scatterers is preferably equal to or less than the scatterer size, and more preferably ½ or less of the scatterer size. The distance between the scatterers is preferably 1/10 or more of the emission wavelength. The distance between the scatterers can be confirmed by cross-sectional observation using a scanning electron microscope or transmission electron microscope, or by X-ray scattering measurement.

  The thickness of the layer having a light scattering function is preferably 100 nm or more, and more preferably 200 nm or more. When the thickness of the layer having the light scattering function is less than this lower limit, the multiple scattering property is lowered, and the scattering anisotropy is increased, so that the viewing angle dependency of luminance may appear. Further, the thickness of the layer having a light scattering function is preferably 50 μm or less, and more preferably 10 μm or less. If the thickness of the layer having the light scattering function exceeds this upper limit, the scattering characteristics change depending on the light path through which the emitted light passes through the layer having the light scattering function, and there is a possibility that the viewing angle dependency of the luminance appears as described above. .

  The light scattering function of the layer having a light scattering function is usually preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less in terms of average light transmittance. In consideration of loss of emitted light due to multiple scattering, the average light transmittance is usually preferably 25% or more, more preferably 40% or more. The parallel light transmittance of the layer having the light scattering function can be usually measured with a spectrophotometer.

Specifically, the layer having a light scattering function is preferably formed by adopting one of the following configurations (1) and (2) for the layer constituting the light extraction film.
(1) A light scattering function is imparted by incorporating transparent particles.
(2) A light scattering function is imparted by forming an uneven surface on the surface by polishing such as blasting.

  The layer (2) on which the concavo-convex surface is formed is preferably an irregular uneven structure interface layer. The irregular uneven structure interface means an aperiodic uneven structure interface. Conventionally, an advanced rough surface structure including a photonic crystal microlens has been proposed, but it is important that the uneven structure is irregular not only in terms of cost but also in terms of scattering anisotropy.

  In order for the emitted light to reduce total reflection at the interface, the surface roughness Ra of the uneven surface is preferably 10 nm or more, and more preferably 100 nm or more. Further, from the viewpoint of light emission bleeding, the surface roughness Ra is preferably 10 μm or less, and more preferably 1 μm or less. The surface roughness Ra of the concavo-convex surface is several times under the condition of one scanning distance of 0.5 μm using a P-15 type contact surface roughness meter manufactured by KLA-Tencor based on the standard defined in JIS B0601. A value obtained by calculating the measured average value.

  The irregular uneven structure interface can be formed by performing polishing treatment such as blasting on the layer constituting the light extraction film, but can also be formed by making transparent particles exist at the interface.

The transparent particles of the layer containing the transparent particles (1) are particles that have no or little absorption in the visible light region. For example, TiO ₂ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , Ta ₂ Examples thereof include O ₃ , ZnO ₂ , Sb ₂ O ₃ , ZrSiO ₄ , zeolite, or a porous material thereof, inorganic particles based on them, and organic particles such as acrylic resin, styrene resin, and polyethylene terephthalate resin. Among these, TiO ₂ , SiO ₂ , porous SiO ₂ , ZrO ₂ , Al ₂ O ₃ , and zeolite particles are preferable.

  In order to cause effective Mie scattering, the particle size of these transparent particles is usually 100 nm or more, preferably 250 nm or more, more preferably 300 nm or more, and usually 20 μm or less, more preferably 10 μm or less.

  The layer containing transparent particles may contain two or more kinds of transparent particles of different materials, and may contain transparent particles having different particle sizes.

  The layer containing transparent particles is usually a light multiple scattering layer formed by applying a coating liquid in which transparent particles are dispersed in a matrix precursor to the surface on which this layer is formed.

  Here, the matrix precursor is preferably a precursor that can form a matrix having a refractive index difference with the transparent particles of usually 0.01 or more, and this refractive index difference is more preferably 0.03 or more, more preferably. Is 0.05 or more, and the upper limit is preferably less than 2, more preferably less than 1.5, and still more preferably less than 1. If this refractive index difference is too low, it becomes difficult to obtain effective Mie scattering, and if the refractive index difference is too large, backscattering increases, and there is a possibility that the light extraction rate cannot be sufficiently obtained.

  Specifically, the matrix precursor can be selected according to the transparent particles, but as a general-purpose material, for example, a reaction of a sol-gel precursor such as a silicate oligomer, a monomer of a thermosetting resin or a UV curable resin, or the like. Or a precursor of a resin melt or a precursor containing these as a main component.

  Examples of a method for applying a coating solution in which transparent particles are dispersed in a matrix precursor include spin coating, dip coating, die coating, casting, spray coating, and gravure coating. Of these methods, spin coating, dip coating, and die coating are preferred from the viewpoint of film uniformity.

  The transparent particle content in the layer containing the transparent particles needs to be adjusted so that Mie scattering is multiple-scattered.

  The layer containing the transparent particles may be formed by applying a coating liquid in which transparent particles are dispersed in a matrix precursor onto the light transmitting body by the above coating method or the like. You may form similarly above.

<Layers other than the layer having the light scattering function of the light extraction film>
The light extraction film of the present invention may have the layers described below in addition to the layer having the light scattering function. Moreover, the layer described below may serve as the layer which has a light-scattering function. In addition, the light extraction film | membrane of this invention may have another layer other than the layer explained in full detail below.

(Low refractive index layer)
The light extraction film of the present invention has a refractive index of 1.05 to 1.4 as at least one layer constituting the light extraction film, and a layer mainly composed of an inorganic oxide (hereinafter referred to as “low refractive index”). It is preferable to have a layer). In the present invention, the “refractive index” means one measured by an optical technique such as a spectroscopic ellipsometer, reflectance measurement or prism coupler, preferably one measured by a spectroscopic ellipsometer or prism coupler. Say.

  The refractive index of the low refractive index layer is usually 1.05 or more, preferably 1.10 or more, usually 1.4 or less, preferably 1.3 or less. As the refractive index of the low refractive index layer is lowered, the light extraction efficiency is improved. However, if the refractive index is lower than the lower limit, the mechanical strength of the light extraction film may be deteriorated.

  Specifically, the material constituting the low refractive index layer is inorganic oxide such as silicon oxide, aluminum oxide, titanium oxide or zirconium oxide, fluoride resin such as cyclic Teflon, magnesium fluoride or the like. Is preferred. Among these, from the viewpoint of chemical resistance and heat resistance, a low refractive index layer mainly composed of an inorganic oxide such as silicon oxide, aluminum oxide, titanium oxide, or zirconium oxide is preferable. The inorganic oxide is particularly preferably an inorganic oxide having a porous structure.

  The film thickness of the low refractive index layer is usually 50 nm or more, preferably 100 nm or more, more preferably 400 nm or more, usually 2 μm or less, preferably 1.5 μm or less, more preferably 1 μm or less. If the film thickness of the low refractive index layer is below this lower limit, the light extraction effect may be reduced, and if it exceeds the upper limit, the uniformity of the film may be reduced.

  The low refractive index layer can be usually formed by a coating process such as spin coating, dip coating, or die coating, or a vacuum process such as vapor deposition or sputtering.

  The low refractive index layer may be formed directly on the translucent body, or may be formed on other layers constituting the light extraction film.

(High refractive index layer)
The light extraction film of the present invention has a layer having a refractive index of 1.5 to 2.2 (hereinafter referred to as “high refractive index layer”) as at least one layer constituting the light extraction film. Preferably it is.

  The refractive index of this high refractive index layer is usually 1.43 or more, preferably 1.6 or more, more preferably 1.7 or more, usually 2.2 or less, preferably 2.0, more preferably 1.9 or less. It is. If the refractive index of the high-refractive index layer is below this lower limit, the guided light is confined inside the thin film, which may reduce the light extraction effect. If the upper limit is exceeded, light absorption occurs in the visible wavelength region, resulting in a semiconductor. And may adversely affect the life and reliability of the electroluminescent device.

  The high refractive index layer is preferably adjacent to the first electrode layer in order to extract guided light traveling in the plane direction inside the thin film including the electroluminescence layer. However, as described later, it is preferable to provide a gas barrier layer between the high refractive index layer and the first electrode layer.

  The high refractive index layer may be formed of a plurality of films, and in this case, the refractive index indicates an average value of the plurality of films.

  In the present invention, in order to move guided light in the thin film including the electroluminescence layer into the high refractive index layer, the high refractive index layer is preferably a layer having a refractive index equivalent to that of the first electrode layer. . In the present specification, “equivalent refractive index” means that the difference between one refractive index and the other refractive index is less than 0.3, preferably 0.2 or less, particularly preferably 0.1 or less. That means.

  The high refractive index layer is usually provided on the light extraction surface side, that is, the translucent body side with respect to the first electrode layer. In this case, the high refractive index layer preferably has insulating properties. However, the high refractive index layer may be provided on the electroluminescent layer side of the first electrode layer. However, when it is provided on the electroluminescence side, it is not a layer positioned between the translucent body and the first electrode layer, and thus does not correspond to the layer constituting the light extraction film in the present invention. In addition, it is more preferable that an insulating high refractive index layer is provided on the light extraction surface side of the first transparent electrode layer in terms of increasing light extraction efficiency.

As the high refractive index layer, a film formed by a sol-gel reaction or a film formed by a vacuum process is used, and materials thereof include SiN _x O _y (x and y are arbitrary numbers of 0 or more, respectively), TiO ₂ , Examples thereof include inorganic oxide materials such as ZrO ₂ and zeolite, organic materials such as thermosetting resins, UV curable resins, and conductive resins, and composite materials thereof. The high refractive index layer may be a laminated film in which these materials are laminated. The material of the high refractive index layer is not particularly limited, but it is important that the high refractive index layer has a refractive index equivalent to that of the first electrode layer. Therefore, in the low refractive index matrix such as acrylic resin or silicate, TiO It is also preferable to adjust the refractive index by adding high refractive index fine particles such as ₂ , Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₃ .

  The high refractive index layer can be usually formed by a coating process such as spin coating, dip coating, or die coating, or a vacuum process such as vapor deposition or sputtering.

  The thickness of the high refractive index layer is usually 200 nm or more, preferably 600 nm or more, usually 50 μm or less, preferably 10 μm or less. If the thickness of the high refractive index layer is less than this lower limit, there is a possibility that the black spots and the lifetime will be reduced during light emission, and if it exceeds the upper limit, there is a possibility that the transmittance will be reduced and light emission bleeding may be caused. Moreover, there is a risk that internal stress increases, distortion increases, and this causes damage.

(Gas barrier layer)
The light extraction film in the present invention, particularly when having the high refractive index layer, partly or entirely of the high refractive index layer has a chemical adverse effect on the first electrode layer, and is dark during electroluminescence emission. It is preferable to have a gas barrier layer between the first electrode layer and the high-refractive index layer because of the possibility of spot generation and life reduction. Here, the gas barrier layer refers to a layer having a water vapor transmission rate of usually 0.5 g / m ² / day or less, preferably 0.5 g / m ² / day or less.

As a material for forming the gas barrier layer, ZrC ₂ , TiO ₂ , Al ₂ O ₃ , CeO ₂ , TiN, Ta ₂ O ₅ , SiO _x N _y , SiN, SiO _x , SnO ₂ , Sb ₂ O ₅ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O _{3 and the} like, or a mixture thereof, but these are not limited, and any of them can be used as long as it is visible and has no absorption or at least a dense film structure, particularly an inorganic compound. Is preferably the main component.

  The gas barrier layer preferably has low visible absorption, but the absorption loss per 100 nm thickness of the gas barrier layer is usually 10% or less, more preferably 5% or less, and particularly preferably 1% or less.

  The thickness of the gas barrier layer is not particularly limited, but considering gas barrier properties, it is usually 20 nm or more, preferably 50 nm or more, particularly preferably 100 nm or more, usually 10 μm or less, preferably 1 μm or less. If the thickness of the gas barrier layer is less than this lower limit, the gas barrier property may be lowered. If the upper limit is exceeded, internal stress and internal strain increase, and the film may be damaged or the optical characteristics may be adversely affected.

  The gas barrier layer is preferably formed by a vacuum process such as vapor deposition or sputtering.

The refractive index of the gas barrier layer is preferably the same as that of the first electrode layer. However, when the film thickness is 200 nm or less, for example, a low refractive index of fluoride compounds such as MgF ₂ and NaF ₂ , nanoporous materials, etc. It is also possible to use materials.

<Laminated structure>
When the above-described layers are stacked as the light extraction film, the stacking order is preferably the following order between the transparent body and the first electrode layer. Absent.
(1) Translucent body / low refractive index layer / layer having light scattering function / first electrode layer
(2) Translucent body / low refractive index layer / layer having light scattering function / high refractive index layer / first electrode layer
(3) Translucent body / low refractive index layer / layer having light scattering function / high refractive index layer / gas barrier layer / first electrode layer
(4) Translucent body / layer having light scattering function / first electrode layer

<Hardness of light extraction film by nanoindentation method>
The light extraction film of the present invention is a single-layer film or a laminated film composed of the above-mentioned layers, but has a hardness of 0.05 to 20 GPa by a nanoindentation method. That is, the light extraction film of the present invention preferably has a hardness by the nanoindentation method of 0.05 to 20 GPa by selecting the material of the layer constituting the light extraction film or selecting the layer structure. It is formed. As a method for obtaining such a light extraction film, for example, a film containing porous silica and inorganic particles is formed, a film made of inorganic particles is formed, or a film made of porous silica is formed. The method of letting you do is mentioned.

  The hardness of the light extraction film of the present invention by the nanoindentation method is 0.05 GPa or more, preferably 0.1 GPa or more and 20 GPa or less, preferably 15 GPa or less. If the hardness of the light extraction film exceeds this upper limit, in the lamination process of the electroluminescence element, distortion occurs in each layer, which may cause dark spots at the time of light emission. This is not preferable because the process suitability of the electroluminescence element is poor.

  In the present invention, the hardness measurement of the light extraction film by the nanoindentation method is performed as follows.

(Nanoindentation hardness measurement method, measurement conditions)
The nanoindentation method is used as a method for measuring the hardness of the light extraction film of the present invention. This method is a method capable of performing the mechanical strength with high accuracy. The measurement is performed by press-fitting a fine tip for nanoindenter onto the sample surface (light extraction film surface) and calculating the hardness from the load-displacement curve. Here, the sample is a light extraction film with a translucent body, and the sample surface is the surface of the light extraction film.

  As a specific measuring method, a Triscope from Hystron is attached to a Nanoscope III from Digital Instrument, a 90 ° tip (total angle of 90 °) is used as a measuring tip, and a tip contact depth of 20 to 25 nm on the sample surface. In order to achieve a degree, the measurement load is 80 to 100 μN, and three points are performed on one sample, and the average value of the hardness is used as the hardness defined in the present invention. Here, the reproducibility is confirmed by the fact that the loading curves match when the set load is changed. In addition, it is necessary to adjust the chip contact depth and the measurement load in order to reduce the influence of the light transmitting material underlying the light extraction film on the chip to be used. Also, a Berkovich chip (total angle: 142.3 °) is required. It is also possible to use it. The hardness of the fused quartz that is the standard sample is set to be 10.42 GPa (90 ° chip) or 11.3 GPa (using Berkovich chip).

<Thickness of light extraction film>
The film thickness as the light extraction film (total thickness of the layers constituting the light extraction film) is preferably 50 nm or more, more preferably 200 nm or more, most preferably 400 nm or more, preferably 50 μm or less, more preferably 20 μm or less, More preferably, it is 15 micrometers or less, Most preferably, it is 5 micrometers or less. If the film thickness of the light extraction film exceeds this upper limit, the strain in the light extraction film increases, which may adversely affect the electroluminescence element such as a dark spot in the lamination process when forming the light extraction film. On the other hand, if the thickness of the light extraction film is below this lower limit, the effect of improving the light extraction efficiency may be reduced.

<Light extraction film density>
The light extraction film of the present invention preferably has a density changing in the film thickness direction. The light extraction film whose density changes in the film thickness direction may be a laminated film composed of a plurality of layers having different densities. In the case of a light extraction film composed of a single layer film, the density changes within the layer. Preferably it is.

  Here, the film thickness direction means a direction perpendicular to the film surface, and the density changes toward the light extraction surface side, so that strain in the light extraction layer in the lamination process can be dispersed. it is conceivable that. Although the change is not particularly limited, it is preferable that the light extraction surface side has a lower density, that is, the density gradually decreases from the first electrode layer side toward the light transmitting body side.

[Translucent material with light extraction film]
The translucent body with a light extraction film of the present invention is formed by forming the above-described light extraction film of the present invention on a translucent body.

  When such a translucent body with a light extraction film of the present invention is used for an electroluminescence element, a high-luminance electroluminescence element can be stably produced.

  As a method for forming the light extraction film on the light transmitting body, each of the above-described layers constituting the light extraction film is formed by a coating process such as spin coating, dip coating, or die coating, or a vacuum process such as vapor deposition or sputtering. The method of doing is mentioned.

  The translucent material forming the light extraction film usually means a material that becomes a substrate of the electroluminescence element.

  Usually, the refractive index of this translucent body is 1.4 or more, preferably 1.45 or more, more preferably 1.47 or more, most preferably 1.5 or more, usually less than 1.9, preferably less than 1.80. More preferably, it is less than 1.75, and most preferably less than 1.65.

As the translucent body having such a refractive index, a transparent substrate made of a general-purpose material can be used. For example, various types of shot glass such as BK ₇ , SF ₁₁ , LaSFN ₉ , BaK ₁ , F ₂ , synthetic phased silica glass, optical crown glass, low expansion borosilicate glass, sapphire glass, soda glass, alkali-free glass, etc. Acrylic resins such as polymethyl methacrylate and crosslinked acrylate, aromatic polycarbonate resins such as bisphenol A polycarbonate, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, amorphous polyolefin resins such as polycycloolefin, epoxy resins, styrene such as polystyrene Examples thereof include a resin, a polysulfone resin such as polyethersulfone, and a synthetic resin such as polyetherimide resin, and may be a laminate of these. Of these, shot glass, synthetic phased silica glass, optical crown glass, low expansion borosilicate glass, soda glass, alkali-free glass, acrylic resin, aromatic polycarbonate resin, polysulfone resin, and amorphous polyolefin resin are preferable. When a resin is used as a light-transmitting material, the glass transition point (Tg) is usually 120 ° C. or higher, preferably 150 ° C. or higher, more preferably 170 ° C. or higher, from the suitability for assembling the element.

  In addition, on the surface of these translucent bodies, that is, the surface on the light extraction side (the side opposite to the light extraction film forming surface), an optical film such as an antireflection film, a circularly polarizing film, or a retardation film depending on the purpose and application. May be formed or pasted together. Further, the surface of the light transmitting body may be provided with an uneven structure interface as described in detail in the layer having the light scattering function of the light extraction film, and the light scattering function may be further provided.

  The thickness of the translucent body is usually 0.1 mm or more and 10 mm or less. From the viewpoint of mechanical strength and gas barrier properties, the thickness of the translucent material is preferably 0.2 mm or more, and is usually 5 mm or less, preferably 3 mm or less from the viewpoint of weight reduction and light transmittance.

[Electroluminescence element]
The electroluminescence element of the present invention is an electroluminescence element in which a transparent body, the light extraction film of the present invention, the first electrode layer, the electroluminescence layer, and the second electrode layer are arranged in this order. The electroluminescent element of the present invention is only required to arrange the light transmitting body, the light extraction film, the first electrode layer, the electroluminescent layer, and the second electrode layer in this order. And may have other layers.

  1A and 1B are schematic cross-sectional views showing an embodiment of the electroluminescence element of the present invention. 1A and 1B includes a second electrode layer (cathode) 1, an electroluminescence layer 2, a first electrode layer (anode) 3, light extraction films 5A and 5B, and a transparent body. (Transparent substrate) 4 is laminated in this order. In the light extraction film 5A of the electroluminescence element of FIG. 1A, a layer 7 having a light scattering function and a low refractive index layer 6 are formed from the first electrode layer 3 side. In the light extraction film 5B of the electroluminescence element of FIG. 1B, a high refractive index layer 8, a layer 7 having a light scattering function, and a low refractive index layer 6 are formed from the first electrode layer 3 side.

  Details of each layer will be described below.

<Translucent body>
The light-transmitting body is as described above as the light-transmitting body of the light-transmitting film-attached light-transmitting body of the present invention, and is usually preferably a substrate for an electroluminescence element. It may be a top emission type element provided with a protective cover on top. In this case, it is preferable that the light transmitting body becomes a protective cover. The material of the protective cover is not particularly limited as long as it is transparent, and examples thereof include various resin materials such as thermoplastic resins and thermosetting resins, and coating materials such as sol-gel films.

<Light extraction film>
The light extraction film is the above-described light extraction film of the present invention, and is usually formed on a light transmitting body. This forming method is as described in detail for the light-transmitting film-attached light-transmitting body.

<First electrode layer>
The first electrode layer is usually an electrode layer that acts as an anode of the electroluminescence element, and is usually a transparent electrode. As the first electrode layer, indium oxide to which tin is added (commonly referred to as ITO), zinc oxide to which aluminum is added (commonly referred to as AZO), zinc oxide to which indium is added (common name) A composite oxide thin film such as IZO) is preferably used. In particular, ITO is preferable.

  In the case where the first electrode layer is a transparent electrode layer having no light scattering function, the parallel light transmittance in the visible light wavelength region is preferably as large as possible, for example, 50 to 99%. The preferable lower limit of the parallel light transmittance is 60%, more preferably 70%.

The electrical resistance of the first electrode layer is preferably as small as the sheet resistance value, but is usually 1 to 100Ω / □ (= 1 cm ² ), and the upper limit is preferably 70Ω / □, more preferably 50Ω / □. is there.

  The thickness of the first electrode layer is usually 0.01 to 10 μm as long as the light transmittance and the surface resistance value described above are satisfied, but its lower limit is preferably 0.03 μm from the viewpoint of conductivity, 0.05 μm is more preferable. On the other hand, from the viewpoint of light transmittance, the upper limit is preferably 1 μm, and more preferably 0.5 μm.

  The first electrode layer is formed into a pattern necessary as an electrode of an electroluminescent element by a photolithography method, an ink jet, or the like using a coating liquid of a conductive material. The line width after patterning is typically about 1 to 10 μm, but is not limited thereto. As the coating solution for forming the first electrode layer, for example, a fine particle in which ITO fine particles are dispersed in an organic solvent together with a conductive polymer or other resin binder, or a conductive polymer material can be used. It is not limited.

<Electroluminescence layer>
The electroluminescent layer is formed by a material that exhibits a light emission phenomenon when an electric field is applied, and may have a single layer structure or a multilayer structure in which functions are separated. In the case of a multilayer structure, layers such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are used. As a material used for the electroluminescence layer, a conventionally used organic electroluminescence material can be used. For example, activated zinc oxide ZnS: X (where X is an activated element such as Mn, Tb, Cu, Sm), CaS: Eu, SrS: Ce, SrGa2S4: Ce, CaGa2S4: Ce, CaS: Conventionally used inorganic electroluminescent materials such as Pb and BaAl2S4: Eu, aluminum complexes of 8-hydroxyquinoline, aromatic amines, organic electroluminescent materials of low molecular dyes such as anthracene single crystals, poly (p-phenylene) Vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene], poly (3-alkylthiophene), conjugated polymer organic electroluminescent materials such as polyvinylcarbazole, and the like. However, it is not limited to these. In addition to these luminescent compounds, materials capable of phosphorescence emission from a triplet state or compounds derived from these fluorescent dyes can be used.

  The thickness of the electroluminescence layer is usually 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, usually 1000 nm or less, preferably 500 nm or less, more preferably 200 nm or less.

  The electroluminescence layer can be formed by a vacuum film formation process such as vapor deposition or sputtering, or a coating process using chloroform or the like as a solvent.

<Second electrode layer>
A 2nd electrode layer is a cathode in an electroluminescent element normally. The material used as the cathode is preferably a metal having a low work function or a compound thereof. In particular, aluminum, tin, magnesium, indium, calcium, gold, silver, copper, nickel, chromium, palladium, platinum, magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy, etc. preferable.

  The thickness of the second electrode layer is not particularly limited, but is usually 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, usually 1000 nm or less, preferably 500 nm or less, more preferably 300 nm or less.

  The second electrode layer can be formed by a vacuum film formation process such as vapor deposition or sputtering.

For the purpose of protecting the cathode made of a low work function metal, a metal layer having a high work function and stable to the atmosphere is laminated on the surface of the second electrode layer opposite to the electroluminescent layer. It is effective in increasing the performance. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used. Further, the efficiency of the device is improved by inserting an ultra-thin insulating film (film thickness: 0.1 to 5 nm) such as LiF, MgF ₂ , or Li ₂ O at the interface between the second electrode layer and the electroluminescence layer. be able to.

  Note that the second electrode layer may be formed using a transparent electrode material such as indium oxide or zinc oxide to which indium is added, and light may be extracted from the second electrode layer side.

<Applications of electroluminescence elements>
By forming the light extraction film of the present invention, it is possible to stably produce an electroluminescent device having high light extraction efficiency, high brightness and long life. It can also be applied to efficient display applications, lighting applications, and other light emitters.

  EXAMPLES Next, although an Example demonstrates this invention more specifically, this invention is not limited to a following example, unless the summary is exceeded.

Example 1
Pluronic (polypropylene glycol-ethylene oxide copolymer) and a partially hydrolyzed silica are mixed in ethanol, spin-coated on alkali-free glass (translucent material), heated and fired to form a porous silica film. A low refractive index layer is formed, and a partially hydrophobized porous silica film is obtained by silylation treatment. The low refractive index layer obtained by a Woollam spectroscopic ellipsometer has a refractive index of about 1.20 and a film thickness of about 890 nm.

  On this porous silica film, by spin-coating a precursor coating liquid in which titania particles (average particle size 260 nm) are dispersed in a silicate oligomer, a light scattering function having a light scattering function with an average light transmittance of 55% is provided. Forming a layer having. The thickness of the layer having the light scattering function is about 350 nm.

  The hardness of the light extraction film comprising a low refractive index layer and a layer having a light scattering function is measured by attaching a nanoindent measuring device (TriboScope made by Hysitron) to Nanoscope III made by Digital Instruments. Using a 90 ° chip, the surface of the light extraction film (transparent electrode lamination side) is press-fitted with a load of 80 μN and calculated from a load-displacement curve. The same measurement is performed at three places, and the average value is 9.2 GPa.

  On this light extraction film, ITO is sputtered at a film thickness of 120 nm at room temperature to form a first electrode layer, a hole injection layer, a hole transport layer, a light emitting layer; a tris (8-hydroxyquinolinato) aluminum complex film Evaporation is performed with a thickness of 150 nm to form an electroluminescence layer. Thereafter, Al is vapor-deposited on the electroluminescence layer to a thickness of 80 nm to form a second electrode layer, thereby forming an organic electroluminescence element.

  The initial luminance of the obtained organic electroluminescence device is improved by about 1.3 times compared to the luminance of the device of Comparative Example 1 described later. In addition, the number of black spots with a diameter of 0.5 mm or more when emitting light is 3 or less in a 5 cm square. One week later, when the light is emitted again, the number of black spots having a diameter of 0.5 mm or more is 4 or less in a 5 cm square.

(Comparative Example 1)
On the opposite side of the light extraction surface of the alkali-free glass, ITO is sputtered at a film thickness of 120 nm at room temperature to form a transparent electrode layer. Further, a hole injection layer, a hole transport layer, a light emitting layer; Tris (8-hydroxyquinolinate) ) An aluminum complex is deposited with a thickness of 150 nm to form an electroluminescence layer. Thereafter, Al is deposited to a thickness of 80 nm on the electroluminescence layer to form an organic electroluminescence element. The number of black spots having a diameter of 0.5 mm or more when the element emits light is 2 or less in a 5 cm square.

It is typical sectional drawing of the electroluminescent element which concerns on embodiment. It is typical sectional drawing of a common electroluminescent element.

Explanation of symbols

1 Electrode layer (second electrode layer: cathode)
2 Electroluminescence layer 3 Transparent electrode layer (first electrode layer: anode)
4 Translucent body (transparent substrate)
5A, 5B Light extraction film 6 Low refractive index layer 7 Layer having light scattering function 8 High refractive index layer

Claims (6)

A light extraction film composed of a single layer film or a laminated film of two or more layers used for an electroluminescence element,
At least one of the layers constituting the light extraction film is a layer having a light scattering function,
A light extraction film, wherein the light extraction film has a hardness of 0.05 to 20 GPa according to a nanoindentation method.   2. The light extraction film according to claim 1, wherein at least one of the layers constituting the light extraction film is a layer mainly composed of an inorganic oxide having a refractive index of 1.05 to 1.4. .   The light extraction film according to claim 1 or 2, wherein at least one of the layers constituting the light extraction film is a layer having a refractive index of 1.43 to 2.2.   The light extraction film according to any one of claims 1 to 3, wherein the thickness is 50 nm to 20 µm.   The light extraction film according to any one of claims 1 to 4, wherein the light extraction film is formed on the light transmission body.   An electroluminescent element comprising a light transmitting body, a light extraction film, a first electrode layer, an electroluminescence layer, and a second electrode layer laminated in this order, wherein the light extraction film is any one of claims 1 to 4. 2. An electroluminescent device, which is the light extraction film according to item 1.

Images