JP2009272069A - El element, backlight device for liquid-crystal display using the element, lighting device using the element, electronic advertising display device using the element, display device using the element, and optical sheet - Google Patents

Abstract

In an EL element in which a fine concavo-convex pattern is provided on a translucent substrate to enhance light extraction efficiency, side lobes in a viewing angle distribution are suppressed, and light extraction efficiency is further improved.
A translucent substrate 12 of an EL element 10 is provided with a fine concavo-convex pattern on an upper surface thereof. This fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions 24 in a plane, the unit convex portion 24 has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion 24 has a substantially V-shaped cross section. It has a plurality of vertices 28 divided by forming at least one groove 26 having a letter shape. By forming the grooves in this way, the shape of the top of the unit convex portion 24 is complicated, thereby suppressing side lobes in the viewing angle distribution and further improving the light extraction efficiency.
[Selection] Figure 1

Description

  The present invention relates to an EL (electroluminescence) element, a backlight device for a liquid crystal display using the EL element, an illumination device using the EL element, an electronic signage device using the EL element, and a display apparatus using the EL element. And an optical sheet. The EL device according to the present invention has excellent light extraction efficiency.

  A generally used EL element includes a light-transmitting substrate and a light-emitting laminated structure provided on one surface of the light-transmitting substrate. The light-emitting laminated structure includes an anode layer and an anode layer. A cathode layer and an EL (electroluminescence) light emitting layer sandwiched between the electrode layers. Then, a direct current voltage is applied between the anode layer and the cathode layer to inject electrons and holes into the EL light emitting layer, and excitons are generated by recombination thereof, and light generated when the excitons are deactivated. The EL light emitting layer is caused to emit light using the emission of light, and thus the light emitted from the light emitting laminated structure is incident on the light transmitting substrate through one surface of the light transmitting substrate, and the light transmitting substrate. And is emitted to the outside through the other surface of the translucent substrate.

  Conventionally, in an EL device having such a configuration, when light emitted from an EL light emitting layer and incident on a translucent substrate attempts to exit the air through the translucent substrate, a considerable portion of the light is There is a problem that light loss occurs due to total reflection on the surface of the translucent substrate. The light loss due to the total reflection may reach about 80% if no measures are taken. In this case, the light extraction efficiency from the EL element is about 20%. If the light extraction efficiency is low, a large amount of power must be input in order to obtain a required luminance, and this increases the load applied to the EL element, thereby reducing the reliability of the EL element.

  For the purpose of improving the light extraction efficiency of a surface light emitting device such as an EL device, an optical sheet on which a plurality of fine protrusions are formed is adhered to the surface of a light transmitting substrate of the surface light emitting device. Various optical sheets for this purpose have been conventionally proposed (see, for example, Patent Document 1 and Patent Document 2).

JP 2006-79040 A JP 2006-119166 A

  Among the conventional optical sheets used for this purpose, the fine uneven pattern of the optical sheet is composed of a plurality of fine quadrangular pyramidal unit convex portions arranged in a plane, and a plurality of fine triangular prism shapes The unit protrusions are arranged in a plane, and the unit protrusions are arranged in a plane (that is, a microlens array). However, there has been a problem that a side lobe appears in the viewing angle distribution from the observer side in the case of using a quadrangular pyramid-shaped unit convex portion or a triangular prism-shaped unit protrusion. In addition, since the lens element is rounded in the microlens array, a gap is formed between the arranged lens elements, and the light is totally reflected in the gap. There was a problem that decreased. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an EL element capable of suppressing side lobes in the viewing angle distribution and further improving the light extraction efficiency. It is to provide.

  The present invention has been made to solve the above problems, and an EL device according to the present invention includes a light-transmitting substrate and a light-emitting laminated structure provided on the first surface of the light-transmitting substrate, The light-emitting laminated structure includes a first electrode layer, a second electrode layer, and an EL (electroluminescence) light-emitting layer sandwiched between the electrode layers, and emitted from the light-emitting laminated structure. Light enters the translucent substrate through the first surface of the translucent substrate, passes through the translucent substrate, and exits to the outside through the second surface of the translucent substrate. In the EL device configured as described above, a fine uneven pattern for extracting light incident on the light transmissive substrate from the light emitting laminated structure to the second surface of the light transmissive substrate from the light transmissive substrate to the outside. The fine concavo-convex pattern has a plurality of fine unit convex portions arranged in a plane. The unit convex portion has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion has a plurality of grooves divided by forming at least one groove having a substantially V-shaped cross section. It has a vertex.

  The invention according to claim 2 is further characterized in that an optical sheet on which the fine concavo-convex pattern is formed is attached to the second surface of the translucent substrate.

  The invention according to claim 3 is further characterized in that the fine concavo-convex pattern is directly formed on the second surface of the translucent substrate.

  The invention according to claim 4 is further characterized in that the apex of the unit convex portion is formed in a rounded shape.

  The invention according to claim 5 is further characterized in that a side surface of the unit convex portion is formed in a curved surface shape having a certain curvature.

  According to a sixth aspect of the present invention, the first electrode layer is a transparent electrode layer located on a side of the translucent substrate of both sides of the EL light emitting layer, and the second electrode layer is the EL element. It is an electrode layer located on the opposite side to the said translucent board | substrate of the both sides of a light emitting layer, It is characterized by the above-mentioned.

  The invention according to claim 7 is further characterized in that the second electrode layer is configured to scatter-reflect light incident on the surface of the second electrode layer from the EL light emitting layer.

  According to an eighth aspect of the present invention, the second electrode layer is a transparent electrode layer, and a light reflective element is provided on a side of the second electrode layer opposite to the EL light emitting layer. The distance between the element and the EL light emitting layer is set such that the light reflected by the surface does not substantially cause optical interference.

  The invention according to claim 9 is further characterized in that the EL light emitting layer is a laminate composed of at least two kinds of light emitting material layers having different light emission colors.

  The invention according to claim 10 is further characterized in that a light emission color of the EL light emitting layer is white.

  The invention according to claim 11 is further characterized in that the light reflective element is made of a metal material.

  A twelfth aspect of the present invention is a backlight device for a liquid crystal display device using the EL element according to any one of the first to thirteenth aspects as a light emission source.

  A thirteenth aspect of the invention is an illuminating device using the EL element according to any one of the first to thirteenth aspects as a light source.

  A fourteenth aspect of the present invention is an electronic signage apparatus using the EL element according to any one of the first to thirteenth aspects as a light source.

  A fifteenth aspect of the present invention is a display device characterized in that the EL element according to any one of the first to thirteenth aspects is configured to drive a pixel.

  The invention according to claim 16 is an optical sheet, and the optical sheet has a fine concavo-convex pattern formed on one surface of the optical sheet, and the fine concavo-convex pattern includes a plurality of fine unit convex portions arranged in a plane. The unit convex portion has a substantially quadrangular pyramid shape, and the top of the unit convex portion has a plurality of apexes divided by forming at least one groove having a substantially V-shaped cross section. It is characterized by having.

  The invention according to claim 17 is further characterized in that the apex of the unit convex portion is formed in a rounded shape.

  The invention according to claim 18 is further characterized in that a side surface of the unit convex portion is formed in a curved surface shape having a constant curvature.

  According to the EL element according to the present invention, and according to the backlight device for liquid crystal, the lighting device, the electronic signage device, the display device, or the optical sheet according to the present invention, the fine concavo-convex pattern of the translucent substrate has a plurality of patterns. Fine unit convex portions are formed in a planar arrangement, the unit convex portions are substantially quadrangular pyramid shapes, and at the top of the unit convex portions, at least one groove having a substantially V-shaped cross section is formed. It has a plurality of vertices divided by. By forming the groove in this way, the shape of the top of the unit convex portion is complicated, thereby suppressing side lobes in the viewing angle distribution and further improving the light extraction efficiency.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the EL element 10 according to the first embodiment of the present invention. The EL (electroluminescence) element 10 includes a translucent substrate 12 and a light emitting laminated structure 14 provided on the first surface (lower surface in the drawing) of the translucent substrate 12. The translucent substrate 12 may be a glass substrate or a plastic substrate, provided that the total light transmittance is 50% or more so that light from the light-emitting laminated structure 14 can be transmitted as much as possible. It is preferable to form with the material which can be used.

  The light emitting laminated structure 14 includes a first electrode layer 16, a second electrode layer 18, and an EL light emitting layer 20 sandwiched between the two electrode layers 16 and 18. One of the two electrode layers 16 and 18 is an anode layer, and the other is a cathode layer. A direct current voltage is applied between the anode layer and the cathode layer to inject electrons and holes into the EL light emitting layer 20, and excitons are generated by recombination thereof. The EL light emitting layer 20 is caused to emit light by utilizing the emission of. The light-emitting laminated structure 14 may be further provided with a hole transport layer, a hole injection layer, an electron transport layer, an electron injection layer, etc., which are well known and are essential to the present invention. Since it is not so important and may be provided as necessary, description thereof will be omitted here.

  The 1st electrode layer 16 is an electrode layer located in the translucent board | substrate 12 side of the both sides of the EL light emitting layer 20, and this is a transparent electrode layer. The transparent electrode layer can be, for example, a layer in which an ITO film, an IZO film, or the like is formed by a dry process such as a vapor deposition method or a sputtering method. However, the film forming material is not limited to these, and other materials can be used as long as they are transparent and have electrical conductivity. The film thickness is desirably 1 μm or less. This is because, although the electrical conductivity is improved as the film thickness is increased, there is a problem that local spikes easily enter the transparent electrode layer and the total light transmittance is reduced. When the height of the protrusion reaches 100 nm, for example, the local spike may cause a problem in the subsequent film formation process.

  The second electrode layer 18 is an electrode layer that is located on the opposite side of the EL light emitting layer 20 from the translucent substrate 12. The second electrode layer 18 is configured to scatter and reflect light incident from the EL light emitting layer 20 onto the surface of the second electrode layer 18. The light emitted from the EL light emitting layer 20 is transmitted through the first electrode layer 16 which is a transparent electrode layer and emitted from the light emitting laminated structure 14. The light emitted from the light emitting laminated structure 14 is incident on the light transmissive substrate 12 through the first surface of the light transmissive substrate 12, passes through the light transmissive substrate 12, and passes through the light transmissive substrate 12. The light is emitted to the outside of the EL element 10 through the second surface (the upper surface in the drawing). The fact that the second electrode layer 18 scatters and reflects light brings about an effect of reducing unevenness in light intensity distribution in the EL element 10, and further scatters retroreflected light rays from the unit convex portions 24 described later. This brings about the effect of returning to the translucent substrate 12.

  The EL light emitting layer 20 may have a single layer structure or a multilayer structure composed of two or more kinds of light emitting material layers having different emission colors. The EL light emitting layer 20 may be a white light emitting layer, or may be a light emitting layer of blue, red, yellow, green, or the like. In the case of a white light emitting layer having a multilayer structure, the structure of the EL light emitting layer 20 is, for example, ITO / CuPc (copper phthalocyanine) / α-NPD doped with rubrene 1% / dinactylanthracene doped with perylene 1% doped / Alq 3. / Lithium fluoride / Al as the cathode may be used. However, the present invention is not limited to this configuration, and an arbitrary configuration using an appropriate material that can set the wavelength of light emitted from the light emitting layer to R (red), G (green), and B (blue) is adopted. It is possible. Further, when used in a full-color display application, full-color display can be performed by separately applying three types of light emitting materials corresponding to R, G, and B, or by superimposing a color filter on white light.

  On the upper surface of the translucent substrate 12, a fine uneven pattern is provided for extracting light incident on the translucent substrate 12 from the light-emitting laminated structure 14 to the outside from the translucent substrate 12. In the illustrated example, the fine uneven pattern is provided on the upper surface of the translucent substrate 12 by sticking the optical sheet 22 on which the fine uneven pattern is formed on the upper surface of the translucent substrate 12. However, a fine concavo-convex pattern may be directly formed on one surface of the translucent substrate 12 without using an optical sheet. The optical sheet 22 has a fine concavo-convex pattern formed on the first surface (the upper surface in the drawing). The fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions 24 in a plane. The unit convex portion 24 has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion 24 has a plurality of vertices 28 divided by forming at least one groove 26 having a substantially V-shaped cross section. The pitch P of the fine concavo-convex pattern can be determined as appropriate. However, considering the prevention of image blur by aligning with the pixel structure in a recent display, the pitch is preferably 10 μm or more and 500 μm or less, and 10 μm or more and 400 μm or less. It is more preferable.

  FIG. 2 is a perspective view showing the shape of the unit convex portion 24 of the optical sheet 22. In the illustrated example, two grooves 26 are formed so as to be orthogonal to the top of each unit projection 24 so that each unit projection 24 has four vertices 28. However, the method of forming the groove is not limited to this, and grooves having various depths, pitches, and opening angles extending in various directions can be provided. The optical sheet 22 having such a configuration can be manufactured using a UV curable resin, an electron beam curable resin, or the like. Alternatively, the optical sheet 22 having such a structure is made of PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer, and the like. It can also be manufactured by injection molding or hot press molding.

  Returning to FIG. 1, the second surface of the optical sheet 22 (the surface opposite to the surface on which the unit convex portions 24 are formed) is the surface of the translucent substrate 12 via the adhesive layer 30. (Upper surface in the figure) is attached. The adhesive layer 30 may be an adhesive layer or an adhesive layer. The surface of the unit convex portion 24 defines an interface with air. This interface is inclined with respect to the side surface (upper surface in the drawing) of the translucent substrate 12, and, as shown in FIG. 3, the action of extracting light from the translucent substrate 12 to the outside by the inclined interface. Is obtained.

  As a pressure-sensitive adhesive or adhesive for forming the adhesive layer 30, urethane-based, acrylic-based, rubber-based, silicone-based, vinyl-based resins, or the like can be used. In addition, as the pressure-sensitive adhesive or adhesive, one that is pressed and adhered in a one-pack type or one that is cured by heat or light can be used, and one that is cured by mixing two liquids or a plurality of liquids. It can also be used. In addition, as a method for forming the adhesive layer 30, there are a method in which the adhesive layer 30 is directly applied to a bonding surface, and a method in which a dry film prepared in advance is bonded. When the adhesive layer is prepared as a dry film, it is preferable because it can be easily handled in the manufacturing process.

  According to the above configuration, the fine concavo-convex pattern provided on the upper surface of the translucent substrate 12 is formed by arranging a plurality of fine unit convex portions 24 in a plane, and the unit convex portions 24 are substantially formed. It has a quadrangular pyramid shape, and the top of the unit convex portion 24 has a plurality of vertices 28 divided by forming at least one groove 26 having a substantially V-shaped cross section. And the groove | channel 26 is formed in this way, The shape of the top part of the unit convex part 24 is complicated. In order to show the effect obtained by this, an optical sheet 22 ′ having a simple square pyramid-shaped unit convex portion 24 ′ as shown in FIG. 4 is provided, and otherwise the same as the EL element 10 of FIG. With the EL element 10 ′ having the configuration as a comparative example, the light intensity with respect to the viewing angle was obtained by simulation for both the EL element 10 of FIG. 1 and the EL element 10 ′ of this comparative example. The simulation results are shown in the graphs of FIGS. 5A and 5B. In the EL element 10 ′ of the comparative example, as shown in the graph of FIG. 5B, although the light extraction efficiency is improved, side lobes are generated in the viewing angle distribution. Therefore, as the viewing angle changes, The phenomenon of brightening or darkening at a certain angle occurs. On the other hand, in the EL element 10 according to the present invention, as shown in the graph of FIG. 5A, side lobes in the viewing angle distribution are suppressed, light extraction efficiency is improved, and the viewing angle distribution is broadened. be able to.

  6 is a side view of an optical sheet 22-1 according to another configuration example that can be used in place of the optical sheet 22 shown in FIGS. The optical sheet 22-1 has a fine concavo-convex pattern formed on the first surface (the upper surface in the drawing), similarly to the optical sheet 22 of FIGS. The fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions 24 in a plane. The unit convex portion 24 has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion 24 has a plurality of vertices 28 divided by forming at least one groove 26 having a substantially V-shaped cross section. However, in this optical sheet 22-1, the apex 28 of the unit convex portion 24 having a substantially quadrangular pyramid shape is formed in a rounded shape, and the shape of the apex 28 of the unit convex portion 24 is as described above. By adopting a simple shape, the above-described operational effects are further strengthened.

  FIG. 7 is a side view of an optical sheet 22-2 according to still another configuration example that can be used in place of the optical sheet 22 shown in FIGS. The optical sheet 22-2 has a fine uneven pattern formed on the first surface (the upper surface in the drawing), similarly to the optical sheet 22 of FIGS. The fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions 24 in a plane. The unit convex portion 24 has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion 24 has a plurality of vertices 28 divided by forming at least one groove 26 having a substantially V-shaped cross section. However, in this optical sheet 22-2, the side surface of the unit convex portion 24 having a substantially quadrangular pyramid shape is formed in a curved shape having a certain curvature. By making the shape of the side surface of the unit convex portion 24 such a shape, it becomes possible to appropriately control the viewing angle distribution of the EL element.

  FIG. 8 is a sectional view of an EL element 40 according to the second embodiment of the present invention. The EL element 40 has the same configuration as that of the EL element 10 according to the first embodiment, and is different from the EL element 40 in that the second electrode layer 18 is a transparent electrode and the EL emission of the second electrode layer 18 is different. The light-reflective element 34 is provided on the side opposite to the layer 20. The interval between the light reflecting element 34 and the EL light emitting layer 20 is set to an interval at which the light reflected on the surface does not substantially cause optical interference. Various highly reflective materials can be used as the material of the light reflective element 34, such as aluminum, zirconium, titanium, yttrium, scandium, silver, indium, various alkali metals, various alkaline earth metals, Various metal materials such as rare earth metals, simple metals or alloys, oxides or halides, and metal-doped organic materials containing these metals can be used, and other materials can also be used. It is. Further, by appropriately setting the interval between the light reflective element 34 and the EL light emitting layer 20, it is possible to reduce optical interference and to reduce stray light having angle dependency and wavelength dependency. Become.

  Since the EL element described above has an excellent light extraction efficiency, it is suitable for use as a light source of a lighting device, and a lighting device having such a configuration is also included in the scope of the present invention. The EL element described above can be suitably used for various other purposes.

  FIG. 9 is a cross-sectional view of an active matrix display device 42 configured by attaching a TFT layer 36 to the back surface of the EL element 10 shown in FIG. 1 and driving the EL element 10 with pixels. In addition, the display device configured as described above is also included in the scope of the present invention. Furthermore, the EL element according to the present invention can be used not only in an active matrix type display device but also in a passive type display device. In that case, the first electrode layer and the second electrode layer of the EL element are used. May be a stripe type structure, and such a display device is also included in the scope of the present invention.

  FIG. 9 is a cross-sectional view of a backlight device for a liquid crystal display device using the EL element 10 shown in FIG. 1 as a light emission source. The EL element 10 illuminates the liquid crystal panel 44 from behind. Yes. The backlight device configured as described above is also included in the scope of the present invention. By using the EL element according to the present invention as a light source of a backlight device for a liquid crystal display device, the structure is made thinner and the power consumption is reduced as compared with a backlight device using a cold cathode fluorescent lamp as a light source. Can also be reduced. In addition, since there is virtually no light source unevenness, a diffusion plate and a lens sheet for reducing the lamp image are not required, which contributes to cost reduction.

  The EL element according to the present invention can also be suitably used as a light emission source of a digital signage apparatus, and the electronic signage apparatus configured as such is also included in the scope of the present invention.

  The optical sheet itself used in the EL element according to the present invention described above also constitutes the subject of the present invention. That is, the optical sheet according to the present invention has a fine concavo-convex pattern formed on one sheet surface, and the fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions in a plane, The unit convex portion has a substantially quadrangular pyramid shape, and the top portion of the unit convex portion has a plurality of vertices divided by forming at least one groove having a substantially V-shaped cross section. It is a feature.

  In the EL element according to the present invention described above, a light diffusion layer may be provided on the fine concavo-convex pattern provided on the second surface (upper surface in the drawing) of the translucent substrate 12. FIG. 11 shows a configuration example in the case where such a light diffusion layer 46 is provided in the EL element 10 of FIG. The light diffusion layer 46 is attached to the fine concavo-convex pattern through the adhesive layer 48, and the top of the unit convex portion 24 constituting the fine concavo-convex pattern is immersed in the adhesive layer 48. According to this configuration, since the light extracted through the unit convex portion 24 is diffused by the light diffusion layer 46, the viewing angle distribution is further improved, and further, contact damage to the top of the unit convex portion 24 is prevented. Is done.

  The light diffusing layer 46 relaxes the angle dependence and wavelength dependence of the viewing angle, and is also effective when simply expanding or controlling the viewing angle. The light diffusion layer 46 is preferably a layer having a haze value of 20% or more. If the haze value is less than 20%, there is a problem that the light diffusion performance is insufficient and the uniformity of in-plane luminance is deteriorated. There is a risk. The light diffusion layer 46 may be, for example, a layer containing fine particles of an inorganic material or an organic material. Examples of the fine particles in this case include titanium oxide, barium sulfate, magnesium carbonate, zinc oxide, clay, aluminum hydroxide. Further, white or transparent fine particles such as zinc sulfide, silica and silicone can be used, and metal particles such as aluminum and silver can also be used. Further, only one type of white or transparent particles or metal particles may be used, or a plurality of types may be mixed and used.

  The light diffusion layer 46 can be configured as a sheet-like light diffusion member, and the light diffusion member can be formed by dispersing light diffusion particles in a transparent resin, for example. In this case, as the transparent resin, a thermoplastic resin, a thermosetting resin, or the like can be used. More specifically, for example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, an epoxy An acrylate resin, a polystyrene resin, a cycloolefin polymer, a methylstyrene resin, a fluorene resin, polyethylene terephthalate (PET), polypropylene, an acrylonitrile styrene copolymer, an acrylonitrile polystyrene copolymer, or the like can be used. 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. The thickness of the sheet-like light diffusing member having the above configuration is preferably 0.05 mm to 5 mm. By doing so, suitable diffusion performance and luminance can be obtained. If the thickness of the light diffusing member is less than 0.05 mm, the diffusing performance may be insufficient. On the other hand, if the thickness exceeds 5 mm, the amount of resin is so large that the luminance may decrease due to absorption. .

  Alternatively, when the light diffusing layer 46 is formed by sticking a sheet-like light diffusing member, the sheet-like light diffusing member is formed as a sheet in which fine bubbles are included in a thermoplastic resin. It can also be. That is, the inner surface of fine bubbles formed inside the thermoplastic resin causes diffused reflection of light, and a light diffusing function equivalent to or higher than that when 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. For white PET, a resin that is incompatible with PET, titanium oxide (TiO2), barium sulfate (BaSO4), fillers such as calcium carbonate are dispersed in PET, and then the PET is stretched by a biaxial stretching method. Thus, bubbles are generated around the filler. In addition, the light diffusing member made of the thermoplastic resin having such a configuration may be extended at least in the uniaxial direction, and bubbles may be generated around the filler by extending in the at least uniaxial direction. it can. Examples of the thermoplastic resin in this case include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexane dimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, Polyester resins such as low-glycol copolymer polyester resin and fluorene copolymer polyester resin, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene , Polyamides, polyethers, polyesteramides, polyetheresters, polyvinyl chloride, cycloolefin polymers, and their components Copolymers, also can be used as mixtures of these resins are not particularly limited. Moreover, it is preferable that the thickness of the sheet-like light diffusing member enclosing such fine bubbles is 25 μm to 500 μm. When the thickness of the light diffusing member is less than 25 μm, the sheet is insufficiently squeezed and wrinkles are likely to occur in the manufacturing process and display. On the other hand, when the thickness exceeds 500 μm, there is no particular problem with optical performance, but there is a possibility that inconveniences such as difficulty in processing into a roll shape due to increase in rigidity.

It is sectional drawing of the EL element which concerns on the 1st Embodiment of this invention. It is the perspective view which showed the unit convex part of the optical sheet in the EL element of FIG. It is a figure for demonstrating the external extraction of the light in the EL element of FIG. It is sectional drawing of the EL element of a comparative example. It is the graph which showed the viewing angle distribution of the EL element of FIG. It is the graph which showed the viewing angle distribution of the EL element of FIG. It is sectional drawing of the optical sheet which concerns on another structural example which can be used instead of the optical sheet of FIG. It is sectional drawing of the optical sheet which concerns on another structural example which can be used instead of the optical sheet of FIG. It is sectional drawing of the EL element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the display apparatus using the EL element of FIG. It is sectional drawing of the backlight apparatus using the EL element of FIG. It is the figure which showed the structure which attached the light-diffusion layer to the EL element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 EL element 12 Translucent board | substrate 14 Light emission laminated structure 16 1st electrode layer 18 2nd electrode layer 20 EL light emitting layer 22, 22-1, 22-2 Optical sheet 24 Unit convex part 26 Groove | move 28 Vertex 30 Adhesive layer 34 Light reflective element 40 EL element 42 Display device 44 Liquid crystal panel 46 Light diffusion layer 48 Adhesive layer

Claims (18)

A translucent substrate and a light-emitting laminated structure provided on the first surface of the translucent substrate, the light-emitting laminated structure comprising: a first electrode layer; a second electrode layer; and An EL (electroluminescence) light emitting layer sandwiched therebetween, and light emitted from the light emitting laminated structure is incident on the light transmitting substrate through the first surface of the light transmitting substrate. In the EL element configured to pass through the translucent substrate and emit to the outside through the second surface of the translucent substrate,
On the second surface of the translucent substrate, a fine uneven pattern is provided for extracting light incident on the translucent substrate from the light emitting laminated structure to the outside. The pattern is formed by arranging a plurality of fine unit protrusions in a plane, the unit protrusions are substantially in the shape of a quadrangular pyramid, and the top of the unit protrusions is at least one having a substantially V-shaped cross section. It has a plurality of vertices divided by forming a groove of a book,
An EL element.   The EL element according to claim 1, wherein an optical sheet on which the fine concavo-convex pattern is formed is attached to the second surface of the translucent substrate.   2. The EL element according to claim 1, wherein the fine concavo-convex pattern is directly formed on the second surface of the translucent substrate.   2. The EL element according to claim 1, wherein the vertex of the unit convex portion is formed in a rounded shape.   2. The EL element according to claim 1, wherein a side surface of the unit convex portion is formed in a curved shape having a constant curvature.   The first electrode layer is a transparent electrode layer positioned on a side of the light-transmitting substrate among both sides of the EL light emitting layer, and the second electrode layer is the transparent electrode layer on both sides of the EL light emitting layer. 2. The EL element according to claim 1, wherein the EL element is an electrode layer located on the side opposite to the optical substrate.   The EL device according to claim 6, wherein the second electrode layer is configured to scatter-reflect light incident on the surface of the second electrode layer from the EL light emitting layer.   The second electrode layer is a transparent electrode layer, and a light-reflective element is provided on the opposite side of the second electrode layer from the EL light-emitting layer, and between the light-reflective element and the EL light-emitting layer. 2. The EL element according to claim 1, wherein the interval is set to an interval at which light reflected by the surfaces does not substantially cause optical interference.   2. The EL device according to claim 1, wherein the EL light emitting layer is a laminate composed of at least two kinds of light emitting material layers having different light emission colors.   The EL element according to claim 1, wherein an emission color of the EL light emitting layer is white.   2. The EL device according to claim 1, wherein the light reflective element is made of a metal material.   A backlight device for a liquid crystal display device, wherein the EL element according to any one of claims 1 to 11 is used as a light source.   12. An illuminating device comprising the EL element according to claim 1 as a light source.   An electronic signboard device comprising the EL element according to claim 1 as a light source.   12. A display device comprising the EL element according to claim 1 so as to drive a pixel. In the optical sheet,
A fine concavo-convex pattern is formed on one of the sheet surfaces, and the fine concavo-convex pattern is formed by arranging a plurality of fine unit convex portions in a plane, and the unit convex portions are substantially in the shape of a quadrangular pyramid. And the top of the unit convex portion has a plurality of vertices divided by forming at least one groove having a substantially V-shaped cross section.
An optical sheet characterized by that.   The optical sheet according to claim 16, wherein the vertex of the unit convex portion is formed in a rounded shape.   The optical sheet according to claim 16, wherein a side surface of the unit convex portion is formed in a curved shape having a constant curvature.

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