JP2010205511A - El element and display device using the same, display device, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element capable of alleviating side lobes of a field angle and improving light extraction efficiency. <P>SOLUTION: The EL element is provided with a transparent anode 13 formed on one of the faces of a translucent base material 11, a light-emitting layer 12 formed on the anode 13 of the base material 11, a cathode 14 formed on the light-emitting layer, and a lens sheet 17 for light extraction fitted to the other face of the base material 12 opposite to the anode 13, made by arraying a plurality of concave lens elements 17a for extracting light generated at the light-emitting layer 12 so as to be irradiated from the opposite face of the base plate 11 in a direction parallel with the opposite face of the base plate 11. When a pitch of the concave lens elements 17a is denoted by P, and a minimum distance between the light-emitting layer 12 and the concave lens element 17a is denoted be T, following relations shall be satisfied. P/T≤0.425. 0.05 mm≤P≤0.5 mm. 0.5 mm≤T≤4 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL (electroluminescence) element used for illumination light sources such as flat panel type display devices and liquid crystal backlight units, electrical decorations, light sources for signs, and the like, and in particular, can improve light extraction efficiency. The present invention relates to an EL element, a backlight device for a liquid crystal display using the EL element, a lighting apparatus using the EL element, a digital signage apparatus using the EL element, and a display apparatus using the EL element.

  In general, as shown in FIG. 9, the EL element has a structure in which a light-transmitting substrate 1 and a light-emitting layer 2 containing a fluorescent organic compound are sandwiched between an anode 3 and a cathode 4. The light is formed by laminating a plurality of triangular cylindrical lens elements 5b shown in FIG. 10 on the base material 5a on the surface opposite to the light emitting layer 2 of the translucent substrate 1. A lens sheet 5 for taking out is provided via an adhesive layer 6 (see Patent Documents 1 and 2). In such an EL element, a direct-current voltage is applied between the anode 3 and the cathode 4 to inject electrons and holes into the light emitting layer 2 and recombine to generate excitons. Light is emitted using the emission of light at the time of deactivation, and the light is emitted from the lens element 5 b of the lens sheet 5 through the translucent substrate 1.

  Conventionally, in such an EL element, when the light emitted from the light emitting layer 2 is emitted from the translucent substrate 1, there is a problem that the light is totally reflected on the translucent substrate 1 and the light is lost. The light extraction efficiency at this time is generally said to be about 20%. For this reason, there is a problem that the higher the luminance is, the more input power is required. Not only that, the load on the EL element increases and the reliability of the EL element itself is lowered.

  Therefore, for the purpose of improving the external extraction efficiency of the light, the lens sheet 5 having the triangular cylindrical lens element 5b shown in FIG. 10 is provided on the light emitting surface side of the translucent substrate 1, and the total reflection of the translucent substrate is performed. A method has been proposed in which a lost light beam is extracted to the outside.

JP 2006-79040 A JP 2006-119166 A

  In the conventional EL element described above, the light emitting layer 2 is sandwiched between the anode 3 and the cathode 4 on the translucent substrate 1, and a triangular cylindrical lens element is formed on the light emitting surface side of the translucent substrate 1. Since the lens sheet 5 having 5b is provided, total reflection of light can be suppressed and the lens sheet 5 can be taken out in the front direction.

  However, in the case of a simple quadrangular pyramid shape or a triangular cylindrical shape as shown in FIG. 8, there are unexpected light rays that are wasted in the lateral direction without proceeding in the visual direction of the viewer. For this reason, as shown in FIG. 11, the light intensity distribution emitted from the lens sheet has the highest light intensity when the viewing angle with respect to the visual direction of the viewer, that is, the visual direction F is 0 ° (corresponding to the axial direction). However, a small light intensity peak occurs around ± 90 ° from the front. That is, there is a problem in that light (side lobes) emitted wastefully from the lateral direction increases.

  In addition, when rounded lens elements such as a microlens shape are arranged, there is a problem that a gap is formed between the lens elements, and light rays are totally reflected in the gap, resulting in side lobes. .

  The present invention was made to solve the above problems, and even if the lens sheet for improving the external extraction efficiency of light is on the viewer side, the side lobe of the viewing angle can be reduced, An object of the present invention is to provide an EL element capable of improving the light extraction efficiency, an illumination light source such as a liquid crystal backlight unit using the EL element, an electronic signboard, and a display device.

ことにより上記課題を解決した。 The present invention is an EL element, which is a translucent base material, a transparent anode formed on one surface of the base material, and a light emitting layer formed on the surface of the anode opposite to the substrate. A cathode formed on a surface of the light emitting layer opposite to the anode, and a lens sheet provided on a surface of the substrate opposite to the anode, wherein the lens sheet is opposite to the substrate. A periodic structure is provided on the surface of the lens sheet, and the light generated in the light emitting layer arranged along the surface is extracted from the surface of the lens sheet opposite to the base, and the period of the periodic structure is P, from the light emitting layer When the shortest distance from the periodic structure is T, the following formula is satisfied.

This solves the above problem.

ことがより好ましい。 In the present invention, when the period of the periodic structure is P and the shortest distance from the light emitting layer to the periodic structure is T, the following expression is satisfied.

It is more preferable.

  More preferably, the periodic structure of the lens sheet is a plurality of concave lens elements arranged along a plane. The lens sheet is preferably adhered to the surface of the substrate opposite to the anode with an adhesive layer. The concave lens element preferably has a concave spherical shape. The concave lens element preferably has a concave aspherical shape. The concave lens element preferably has a concave square pyramid shape. Preferably, the plurality of concave lens elements have a constant planar surface area and depth, and the array pitch of the plurality of concave lens elements is constant. It is preferable that a light diffusion member is provided on the surface of the lens sheet on the concave lens element side. It is preferable that the light diffusion member is bonded to the surface of the lens sheet on the concave lens element side through an adhesive layer.

  The EL element can be preferably used in a backlight device for a liquid crystal display, a digital signage device, a lighting device, and a light extraction film. In a display device including an image display element that defines a display image according to transmission / shading in pixel units, the backlight device or the illumination device can be preferably used on the back surface of the image display element.

  According to the present invention, the lens sheet for light extraction formed by arranging a plurality of concave lens elements that extract the light generated in the light emitting layer from the surface opposite to the one surface of the substrate is used as the anode of the base material. Since the structure is provided on the opposite surface, the EL element capable of reducing the side lobe of the viewing angle and improving the light extraction efficiency even when the lens sheet is on the viewer side, and the liquid crystal using the EL element Lighting devices such as backlight units for electronic use, electronic signage devices, display devices, and light extraction films can be provided.

It is a schematic sectional drawing which shows Embodiment 1 of the EL element which has the lens sheet for light extraction concerning this invention. 3 is a perspective view of a part of a light extraction lens sheet of an EL element according to Embodiment 1. FIG. It is a graph showing the relationship between the periodic structure P of the lens sheet for light extraction which concerns on this invention, the shortest distance T, and front luminance. It is a graph which shows the periodic structure P of the lens sheet for light extraction which concerns on this invention, and the suitable area | region of the shortest distance T. FIG. It is a schematic sectional drawing which shows Embodiment 2 of the EL element which has the lens sheet for light extraction concerning this invention. It is a schematic sectional drawing which shows Embodiment 3 of the EL element which has the lens sheet for light extraction concerning this invention. It is a graph which shows distribution of the light intensity with respect to the viewing angle of EL element in Embodiment 3 of this invention. It is a schematic sectional drawing which shows an example at the time of comprising a liquid crystal display device using the EL element with a light-diffusion member which concerns on this invention in Embodiment 4. It is a schematic sectional drawing of the EL element which has the lens sheet for light extraction in the past. It is a perspective view which shows an example of the lens sheet which consists of a triangular cylindrical lens element used for the conventional EL element. It is a graph which shows distribution of the light intensity with respect to the viewing angle of the conventional EL element.

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

(Embodiment 1)
Embodiment 1 of an EL element according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of the EL element shown in the first embodiment, and FIG. 2 is a perspective view of a part of a light extraction lens sheet of the EL element shown in the first embodiment. As shown in FIG. 1, the EL element 10 shown in Embodiment 1 has a flat plate-like light-transmitting substrate 11 having a thickness, and is formed on one surface of the light-transmitting substrate 11. A transparent anode 13 is formed corresponding to the power pixel. Further, a light emitting layer 12 containing a fluorescent organic compound is formed on the surface of the anode 13 opposite to the light base material 11. Further, a cathode 14 is formed on the surface of the light emitting layer 12 opposite to the anode 13 so as to sandwich the light emitting layer 12 between sandwiches. The use of the carrier transport layer, the electron transport layer, the hole transport layer, or both carrier transport layers is not particularly limited, and can be used according to convenience. Further, a lens sheet 17 for extracting light is bonded to the surface of the translucent substrate 11 opposite to the anode 13 through an adhesive layer 16.

  As shown in FIGS. 1 and 2, the lens sheet 17 faces the surface of the translucent base film 17a and the base film 17a opposite to the adhesive layer 16, and is in a two-dimensional direction along the surface. And a plurality of concave lens elements 17b having a concave quadrangular pyramid shape having a constant depth and formed at a constant pitch. The concave lens element 17 b is for taking out the light generated in the light emitting layer 12 so as to be emitted from the surface opposite to the one surface of the translucent substrate 11. In the lens sheet 17, an arbitrary lens element such as a convex lens element can be adopted as the lens element in addition to the concave lens element. However, it is preferable to adopt a concave lens element that further increases the front luminance. .

  In the EL element 10 including the lens sheet 17 formed by arranging a plurality of concave lens elements 17b having a concave quadrangular pyramid shape, a rapid luminance change such as a side lobe hardly occurs in the viewing angle. Thereby, even when the lens sheet is on the viewer side, the side lobe of the viewing angle can be reduced, and the light extraction efficiency can be improved. Further, such an EL element 10 can be used as a backlight device for a liquid crystal display, and can also be used as an electronic signboard device or a lighting device or a light extraction film.

ここでいう周期構造のピッチとは、連続して配置されたレンズ素子が形成する周期構造である。周期構造は、単位レンズ素子で周期構造が形成される場合は、レンズ素子の幅が、周期構造のピッチに相当する。複数のレンズ素子で周期構造が形成される場合は、複数のレンズ素子が形成するグループの端部から端部までが周期構造のピッチに相当する。上述の周期構造を、周期構造のピッチにてシフトした場合、隣接する周期構造と同位置になる。周期構造のピッチは、ある一方向と、一方向に垂直に交わる他の方向において、ほぼ同一であることが好ましい。あるいは、ある一方向と、一方向に垂直に交わる他の方向において、周期構造のピッチが異なっていてもよい。 Here, when the pitch of the periodic structure of the lens sheet 17 is P and the shortest distance from the light emitting layer to the periodic structure is T, light can be efficiently extracted when the relationship of the following expression is satisfied.

Here, the pitch of the periodic structure is a periodic structure formed by continuously arranged lens elements. When the periodic structure is formed of unit lens elements, the width of the lens element corresponds to the pitch of the periodic structure. When the periodic structure is formed by a plurality of lens elements, the end to end of the group formed by the plurality of lens elements corresponds to the pitch of the periodic structure. When the above-mentioned periodic structure is shifted by the pitch of the periodic structure, it is in the same position as the adjacent periodic structure. It is preferable that the pitch of the periodic structure is substantially the same in one direction and the other direction perpendicular to the one direction. Alternatively, the pitch of the periodic structure may be different between one direction and another direction perpendicular to the one direction.

FIG. 3 shows simulation results when the pitch P of the periodic structure and the shortest distance T from the light emitting layer to the periodic structure are changed. The graph is graphed based on the maximum value of the front luminance when the shortest distance T is the same. From this result, it is confirmed that the front luminance varies depending on the value of P / T. In particular, it is confirmed that the front luminance decreases when P / T exceeds 0.425. For this reason, when selecting the pitch P of the periodic structure, it is necessary to determine the pitch P so that the front luminance does not decrease. When P / T exceeds 0.425, the luminance drop exceeds 10% with respect to the maximum value. Therefore, P / T needs to be 0.425 or less.
The simulation was performed using geometric optics. The shape of the concave lens element was simulated in a quadrangular pyramid shape with an apex angle of 90 degrees with a square bottom surface. The unit concave lens element is a periodic structure, and the length of one side of the bottom surface is a pitch P of the periodic structure. The refractive index of the concave lens element was 1.50.
In the case of adopting the quadrature shape in the shape of the concave lens element, it is preferable to make the bottom surface square because the light distribution from the EL element can be made symmetric.
In addition, in the case of adopting the quadrature shape in the shape of the concave lens element, by making the bottom surface rectangular and making the apex angle different between the short side direction of the rectangle and the long side direction, The light distribution can be made asymmetric. Depending on the installation location of the EL element, an asymmetric light distribution may be preferred. For example, when used as a backlight source of a liquid crystal display, a normal display requires a horizontal viewing angle rather than a vertical viewing angle with respect to the display. Liked. In such a case, it is possible to adjust the light distribution by appropriately designing the rectangular short side and long side length of the bottom surface of the quadrangular pyramid shape.
The refractive index of the concave lens element is preferably 1.45 to 1.60. If the refractive index is less than 1.45, the difference in refractive index from air is insufficient, so that light cannot be refracted in the front direction, which is not preferable. If the refractive index exceeds 1.60, the difference in refractive index with air becomes excessive and total reflection occurs, and the efficiency is reduced because the concave lens element is not emitted to the air side but returned to the back side. It is not preferable.

  In addition, the maximum luminance when the shortest distance T is the same is P / T is 0.025 or more and within 0.2, and therefore, the front luminance can be increased more efficiently by making it within the above-described range. It becomes possible.

  The pitch P of the periodic structure is preferably 50 μm or more and 500 μm or less. When the pitch P of the periodic structure is less than 50 μm, the influence of the light diffraction effect due to the miniaturization of the periodic structure is increased, and color dispersion and a decrease in front luminance occur, which is not preferable. When the pitch P of the periodic structure exceeds 500 μm, the pitch of the periodic structure becomes excessive, and the difference in surface area between the surface having the lens element and the surface having no lens element of the lens sheet 17 becomes excessive, and the lens sheet This is not preferable because 17 warp is greatly generated. When the lens sheet base material and the lens element are formed of different materials in the lens sheet 17 by using a UV molding method or the like, if the pitch of the periodic structure is excessive, the lens element is excessively contracted and the lens sheet 17 is warped. It is not preferable because it occurs greatly.

  The shortest distance T is mainly determined by the thickness of the translucent substrate 11. The shortest distance T is preferably 0.5 mm or greater and 4 mm or less. When the shortest distance T is less than 0.5 mm, the thickness of the translucent substrate 11 is less than 0.5 mm and the rigidity is insufficient, so that the impact resistance is deteriorated or the lens sheet 17 is warped. Since it occurs, it is not preferable. When the shortest distance T exceeds 4 mm, the thickness of the translucent substrate 11 exceeds 4 mm, which is not preferable because the weight increases.

FIG. 4 shows a graph showing the above relationship. By creating the surrounding structure of the lens sheet in the region A shown in FIG. 4, it is possible to improve the front luminance, and at the same time, it is possible to obtain a highly rigid and lightweight illumination.
The lens sheet 17 may be provided with a rib on the lens element in order to improve the friction resistance. By providing the rib, when the lens sheet 17 comes into contact with an external object, the lens sheet 17 comes into contact with the rib located outside the lens element, so that the lens element is not contacted and the lens element is prevented from being damaged. Can do. Since the rib does not contribute to the change of the light in the front direction, it is not regarded as a periodic structure of the lens element.

  The translucent substrate 11 may be glass or plastic. In order to transmit the light from the light emitting layer 12 as much as possible, the total light transmittance is preferably 50% or more.

  Examples of the light emitting layer 12 include white, blue, red, yellow, and green. Therefore, for example, as an example of a structure for displaying white, ITO / CuPc (copper phthalocyanine) / α-NPD is doped with 1% rubrene, 1% doped with dioctylanthracene, 1% doped with perylene, Alq3, lithium fluoride, and Al as a cathode. A configuration can be mentioned. However, the present invention is not limited to this configuration, and materials may be appropriately selected so that the wavelengths of light emitted from the light emitting layer are R, G, and B. Further, when used in a full-color display application, full-color display is possible by separately applying R, G, and B, or by superimposing a color filter on white light.

  The transparent anode 13 is made of ITO, IZO or the like formed by a dry process such as vapor deposition or sputtering. Here, the material to be deposited is not limited to the above-described materials, and any material that is transparent and has electrical conductivity may be used. The thickness is preferably about 10,000 mm or less. If it is too thick, the electrical conductivity is improved, but local spikes are likely to enter the transparent electrode, and the total light transmittance is reduced. If the height of the protrusion of the local spike is, for example, about 100 nm, a problem may occur in the subsequent film forming process.

  The adhesive layer 16 is formed using an adhesive or an adhesive. Urethane, acrylic, rubber, silicone, and vinyl resins can be used for the pressure-sensitive adhesive and adhesive. In addition, as the pressure-sensitive adhesive or adhesive, one that is pressed and adhered in a one-pack type, one that is cured by heat or light, and one that is cured by mixing two liquids or a plurality of liquids is used. Can do. As a method for forming the adhesive layer 16, there are a method in which the adhesive layer 16 is directly applied to a bonding surface and a method in which a dry film prepared in advance is bonded. When the adhesive layer 16 is prepared as a dry film, it is preferable because it can be easily handled in the manufacturing process.

  The unit lens as described above is molded on the base film 17a using a UV curable resin or a radiation curable resin, or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethylmethacrylate), COP ( Cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc., and the like by an extrusion molding method, injection molding method, or hot press molding method well known in the art. Form.

(Embodiment 2)
Embodiment 2 of the EL element according to the present invention will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view of the EL element shown in the second embodiment. As in the case shown in FIG. 1, the EL element 10 shown in FIG. 5 includes a translucent substrate 11, a transparent anode 13 formed on one surface of the translucent substrate 11, and the anode. A light emitting layer 12 formed on the surface of the light emitting substrate 12 opposite to the anode 13, a cathode 14 formed on the surface of the light emitting layer 12 opposite to the anode 13, and an anode 13 of the light transmitting substrate 11 opposite to the anode 13. And a light-extracting lens sheet 17 bonded to the surface of the lens sheet 17 via an adhesive layer 16, and a light diffusing member 18 provided on the surface of the lens sheet 17 on the concave lens element 17 b side. Is.

  In the EL element 10 shown in the second embodiment, the light generated in the light emitting layer 12 is randomly diffused by the fine concave lens element 17 b of the lens sheet 17, and the light on the surface of the lens sheet 17. The light is emitted from the emission surface.

  Therefore, according to the EL element 10 shown in the second embodiment, the same effects as those of the first embodiment can be obtained, and by providing the light diffusing member 18, the viewing angle can be increased and the color tone can be uniform. In addition, since the concave lens element 17a is not exposed on the light emitting surface of the EL element 10, dirt and the like are less likely to adhere to the light emitting surface. Further, since the light emitting surface of the EL element 10 is flat, it is possible to provide a hard coat or to join the flat surface. Further, such an EL element 10 can be used as a backlight device for a liquid crystal display, and can also be used as an electronic signboard device or a lighting device or a light extraction film.

(Embodiment 3)
Embodiment 3 of the EL element according to the present invention will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view of the EL element shown in the third embodiment. As in the case shown in FIG. 1, the EL element 10 shown in FIG. 6 includes a translucent base material 11, a transparent anode 13 formed on one surface of the translucent base material 11, and the anode A light emitting layer 12 formed on the surface of the light emitting substrate 12 opposite to the anode 13, a cathode 14 formed on the surface of the light emitting layer 12 opposite to the anode 13, and an anode 13 of the light transmitting substrate 11 opposite to the anode 13. And a light extraction lens sheet 17 bonded to the surface of the lens sheet 17 via an adhesive layer 16, and the light diffusion member 18 is bonded to the surface of the lens sheet 17 on the concave lens element 17 b side via an adhesive layer 19. Has been.

  In such an EL element 10 shown in the third embodiment, the same effect as in the second embodiment can be obtained, and the surface of the lens sheet 17 on the concave lens element 17b side of the light diffusion member 18 through the adhesive layer 19 is obtained. By adhering to, the adhesion strength between them can be increased. Thereby, as shown in FIG. 7, appearance of a side lobe can be suppressed and a uniform viewing angle can be ensured. Further, such an EL element 10 can be used as a backlight device for a liquid crystal display, and can also be used as an electronic signboard device or a lighting device or a light extraction film.

  The light diffusing member 18 shown in FIGS. 5 and 6 preferably has a haze value of 20% or more. When the haze value is less than 20%, the diffusion performance becomes insufficient and the uniformity of in-plane luminance is deteriorated, which is not preferable. The light diffusing member 18 is formed by dispersing a light diffusing region in a transparent resin. As the transparent resin, a thermoplastic resin, a thermosetting resin or the like can be used. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, an epoxy acrylate resin, a polystyrene resin, a cycloolefin polymer, Methyl styrene resin, fluorene resin, polyethylene terephthalate (PET), polypropylene, acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer, and the like can be used.

The light diffusion region is preferably made of light diffusion particles. This is because suitable diffusion performance can be easily obtained. As the light diffusing particles, transparent particles made of an inorganic oxide or a resin can be used. As the transparent particles made of an inorganic oxide, for example, silica, alumina or the like can be used. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine / formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Fluoropolymer particles such as fluoroethylene / hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene / tetrafluoroethylene copolymer), silicone resin particles, and the like can be used. Moreover, you may use combining 2 or more types of transparent particles from the transparent particle mentioned above. Furthermore, the size and shape of the transparent particles are not particularly defined.

  When light diffusing particles are used as the light diffusing region, the thickness of the light diffusing member is preferably 0.05 mm to 5 mm. When the thickness of the light diffusing member is 0.05 mm to 5 mm, optimum diffusion performance and brightness can be obtained. On the other hand, if the thickness is less than 0.05 mm, the diffusion performance is insufficient, and if it exceeds 5 mm, the amount of resin is large, resulting in a decrease in luminance due to absorption.

  In the case where a thermoplastic resin is used as the transparent resin, air bubbles may be used as the light diffusion region. That is, the internal surface of the bubble formed inside the thermoplastic resin causes diffused reflection of light, and a light diffusing function equivalent to or higher than that when the light diffusing particles are dispersed can be exhibited. Therefore, it becomes possible to make the film thickness of the light diffusing member thinner.

Examples of such a light diffusing member include white PET and white PP. White PET is a resin that is incompatible with PET, and fillers such as titanium oxide (TiO ₂ ), barium sulfate (BaSO ₄ ), and calcium carbonate are dispersed in PET, and then the PET is stretched by a biaxial stretching method. By doing so, bubbles are generated around the filler to form.

  In addition, the light-diffusion member consisting of a thermoplastic resin should just be extended | stretched by at least 1 axial direction. This is because bubbles can be generated around the filler by stretching in at least one axial direction. Examples of the thermoplastic resin include polyethylene terephthalate (PET), polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, sporoglycol copolymer polyester. Resins, polyester resins such as fluorene copolymer polyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene, polyamide, polyether , Polyesteramides, polyetheresters, polyvinyl chloride, cycloolefin polymers, and copolymers containing these as components, Such as a mixture of these resins can be used are not particularly limited.

  When bubbles are used as the light diffusion region, the thickness of the light diffusion member is preferably 25 μm to 500 μm. When the thickness of the light diffusing member is less than 25 μm, the sheet is not sufficiently squeezed and wrinkles are likely to occur in the manufacturing process and display, which is not preferable. In addition, when the thickness of the diffusion base material exceeds 500 μm, there is no particular problem with optical performance, but it is difficult to process into a roll shape due to increased rigidity, and slits cannot be easily formed. This is not preferable because the advantage of thinness obtained in this manner is reduced.

(Embodiment 4)
8 uses the EL element 10 with the light diffusing member 18 shown in FIG. 5 as a light source for illumination, and uses this light source for illumination as a backlight. 26 corresponding to the image display elements described in the above-mentioned range are arranged opposite to each other, whereby a liquid crystal display device 27 is configured.

  Note that the liquid crystal display device 27 can be configured by using the EL element 10 with the light diffusion member 18 shown in FIG. 6 as a lighting device and using the lighting device as a backlight device of the liquid crystal panel 26.

DESCRIPTION OF SYMBOLS 1 ... Translucent board | substrate 2, 12 ... Light emitting layer 3, 13 ... Anode 4, 14 ... Cathode 5 ... Lens sheet 5a ... Base material 5b ... Lens element 10- .... EL element 11 ... Translucent substrate 12a ... Light beam 17 ... Lens sheet 17a ... Base film 17b ... Lens element 18 ... Light diffusion member 19 ... Adhesive layer 26 ... Liquid crystal panel 27 ... Liquid crystal display

Claims (15)

A translucent substrate;
A transparent anode formed on one side of the substrate;
A light-emitting layer formed on the surface of the anode opposite to the substrate;
A cathode formed on a surface of the light emitting layer opposite to the anode;
A lens sheet provided on the surface of the substrate opposite to the anode,
The lens sheet has a periodic structure in which the light generated in the light emitting layer is arranged along the surface of the lens sheet opposite to the base material and is extracted from the surface of the lens sheet opposite to the base material,
When the period of the periodic structure is P and the shortest distance from the light emitting layer to the periodic structure is T, the following formula

An EL element characterized by satisfying: When the period of the periodic structure is P and the shortest distance from the light emitting layer to the periodic structure is T, the following formula

The EL element according to claim 1, wherein:   2. The EL element according to claim 1, wherein the periodic structure of the lens sheet is a plurality of concave lens elements arranged along a plane.   2. The EL element according to claim 1, wherein the lens sheet is bonded to a surface of the base material opposite to the anode with an adhesive layer.   The EL element according to claim 3, wherein the concave lens element has a concave spherical shape.   The EL element according to claim 3, wherein the concave lens element has a concave aspherical shape.   The EL element according to claim 3, wherein the concave lens element has a concave quadrangular pyramid shape.   The planar surface area and depth of the plurality of concave lens elements are constant, and the arrangement pitch of the plurality of concave lens elements is constant. EL element of description. 9. The EL element according to claim 3, wherein a light diffusion member is provided on a surface of the lens sheet on the concave lens element side. The EL element according to claim 9, wherein the light diffusing member is bonded to a surface of the lens sheet on the concave lens element side through an adhesive layer.   A backlight device for a liquid crystal display, comprising the EL element according to claim 1.   An electronic signboard device comprising the EL element according to claim 1.   An illumination device comprising the EL element according to claim 1. An image display element that defines a display image according to transmission / light shielding in pixel units,
A display device comprising the backlight device according to claim 11 or the illumination device according to claim 13 on a back surface of the image display element.   A light extraction film comprising the EL element according to claim 1.

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