JP2010205513A - El element and indication device using it, display device, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element having a lens sheet for improving light extraction efficiency at an observer's side, capable of lens molding even with a small curvature radius of a roundness at a tiptop of the lens, with a lens surface hardly damaged, and capable of improving light extraction efficiency. <P>SOLUTION: The EL element is provided with a translucent base material 11, a transparent anode 13 formed on one of the faces of the base material 11, a light-emitting layer 12 formed on a face of the anode 13 opposite to the base material 11, a cathode 14 formed on a face of the light-emitting layer 12 opposite to the anode 13, and a lens sheet 17 fitted to the other face of the base material 11 opposite to the anode 13. The lens sheet 17 contains lens elements 17b arrayed on and along the face of the lens sheet 17 opposite to the base material 11 for extracting light generated at the light-emitting layer 12 from the face of the lens sheet 17 opposite to the base material 11, with a curvature radius r of the tiptop of each lens element 17b as prisms of 1.5 μm or more and 2.5 μm or less. <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. 1, 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. 2 is formed by laminating a plurality of triangular cylindrical lens elements 5b shown in FIG. 2 on a 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. 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 light, a lens sheet 5 having a triangular cylindrical lens element 5b shown in FIG. 2 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 2007-207471 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 the 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. In the case of a triangular cylindrical shape as shown in FIG. 2, the front luminance increases as the tip is rounded to increase the extraction efficiency. However, the sharper the tip of the lens, the more smoothly it can be removed from the mold during lens molding, and the finer the lens pattern, the easier it is to scratch the lens after molding. Problems arise.

  The present invention has been made in order to solve the above-described problems, and there is a lens sheet for improving the light extraction efficiency on the observer side, and even if the curvature radius of the roundness of the apex of the lens is small, the lens An object of the present invention is to provide an EL element that can be molded, hardly scratches the lens surface, can improve the light extraction efficiency, an illumination light source such as a backlight unit for liquid crystal using the same, an electronic signboard, and a display device And

  The present invention includes a translucent substrate, a transparent anode formed on one surface of the substrate, a light emitting layer formed on the surface of the anode opposite to the substrate, and the light emitting layer. A cathode formed on a surface opposite to the anode; and a lens sheet provided on a surface of the substrate opposite to the anode, wherein the lens sheet is disposed on a surface of the lens sheet opposite to the substrate. And a lens element that takes out light generated in the light emitting layer from the surface of the lens sheet opposite to the base material, the lens element is a prism, and the apex radius of curvature r is 1.5 μm or more. The said subject was solved as being 2.5 micrometers or less.

  It is preferable that a lubricant is added to the lens element in the range of 0.1 wt% to 5.0 wt%. The lens sheet is preferably adhered to the surface of the substrate opposite to the anode with an adhesive layer. The EL element can be preferably used in a backlight device for a liquid crystal display, a digital signage device, and a lighting device. In a display device including an image display element that defines a display image according to transmission / light shielding in pixel units, the backlight device or the illumination device can be preferably used as a backlight on the back surface of the image display element. The EL element can be preferably used for the light extraction film. The apex angle of the prism is preferably 90 °.

  According to the present invention, even if the lens of the lens sheet for light extraction formed by arranging a plurality of lens elements that extract the light generated in the light emitting layer from the surface opposite to the one surface of the substrate is an acute angle, the lens is molded. Providing EL devices that can prevent scratches on the lens surface and improve light extraction efficiency, and lighting devices such as backlight units for liquid crystals using the same, electronic signage devices and display devices, and light extraction films can do.

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. 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.

  An embodiment for implementing an EL element according to the present invention will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view of the EL element shown in the first embodiment. As shown in FIG. 4, the EL element 10 shown in Embodiment 1 has a flat plate-like light-transmitting substrate 11 having a thickness, and on one surface of the light-transmitting substrate 11, A transparent anode 13 is formed corresponding to the pixel to be formed. 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. 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. 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.

  As shown in FIG. 4, the lens sheet 17 is formed on the surface opposite to the adhesive layer 16 of the base film 17a and the base film 17a at a constant pitch in a two-dimensional direction along the surface. And a plurality of lens elements 17b having a concave quadrangular pyramid shape with a constant depth. The lens element 17b having an inverted quadrangular pyramid shape 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.

  The lens element 17b has a structure with a sharper apex angle than the conventional cylindrical lens element. In the EL element 10 including the lens sheet 17 formed by arranging the lens elements 17b having a sharp apex angle, the brightness in the front direction is higher than that of the conventional lens element, but the part is peeled off from the mold during lens molding. Have a problem. In addition, as an apex angle, 50 degrees-130 degrees are preferable for the reason of the brightness | luminance increase of a front direction, and since 90 degrees has the highest brightness | luminance, 90 degrees can be used preferably.

  In general, the lens sheet 17 is cut into a predetermined shape after manufacturing, becomes an EL element 10 through transportation and assembly to an assembly factory, and is displayed and used after transportation to a store. In all these processes, the surface of the lens sheet 17 is exposed to the risk of being damaged by vibrations or the like. If the lens sheet 17 is scratched, the light transmitted through the scratch is irregularly reflected, which causes a significant decrease in optical performance. Regarding the scratches, the conventional cylindrical lens element has the same concern, but as the tip pattern becomes finer, the scratches are likely to be attached.

  In order to prevent this, a hard coat treatment that physically hardens the surface having an optical shape is effective. However, this method is not a highly versatile method because it is necessary to provide a coating step. In addition, the method of attaching the protective film to the surface of the lens sheet 17 increases the number of steps for removing the protective film when the optical sheet is used, and the protective film is eventually discarded. It is hard to say that it is an efficient method.

  In the present invention, a lubricant and a mold release agent are added to the lens element 17b in order to solve the problem of poor peeling from the mold during lens molding and ease of scratching that occur with the complication and miniaturization of the lens shape. Measures were taken by including.

  Although there is no restriction | limiting in the material used for the lens element 17b in this embodiment, since it is meaningless to employ | adopt the structure of this embodiment with the raw material which is hard to be damaged, it is appropriate to use the material whose pencil hardness is 4H or less.

  The base film 17a and the lens element 17b constituting the lens sheet 17 may be made of different materials or may be integrally molded with the same material. As the main material of the lens sheet 17, for example, polycarbonate, acryl-styrene copolymer, polystyrene, styrene-butadiene-acrylonitrile copolymer, or cycloolefin polymer may be used. The lens sheet 17 may include transparent particles dispersed in a main material, and the refractive index of the main material and the refractive index of the transparent particles are different. The difference between the refractive index of the main material and the refractive index of the transparent particles is preferably 0.01 or more. If the difference in refractive index is smaller than this, sufficient light scattering performance cannot be obtained. Further, the refractive index difference is 0.5 or less. The average particle size of the transparent particles is preferably 0.5 μm to 30.0 μm.

  As the transparent particles, transparent particles made of an inorganic oxide or transparent particles made of a synthetic resin can be used. For example, examples of the transparent particles made of an inorganic oxide include particles made of silica, alumina or the like. Further, transparent particles made of synthetic resin include acrylic particles, styrene particles, styrene acrylic particles and crosslinked products thereof; melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP ( Examples thereof include fluorine-containing polymer particles such as tetrafluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer), and silicone resin particles. These transparent particles may be used as a mixture of two or more kinds. Alternatively, the plate-like member constituting the lens sheet 17 may have a structure having a fine cavity containing air in the main material, and the diffusion performance is improved by the difference in refractive index between the main material and air. Obtainable. The lens sheet 17 may have a single layer structure or a multilayer structure, and may include a transparent layer.

  The lens sheet 17 can be manufactured by an extrusion method, a casting method, or an injection method. As the plate-like member for manufacturing the lens sheet 17, a member having a thickness of 12 μm or more and 1 mm or less can be used. When the thickness is less than 12 μm, there is no rigidity that can withstand the processing by the above-described manufacturing method, and when the thickness exceeds 1 mm, there is no flexibility that can withstand the processing.

  When forming the lens sheet 17 by the above method, if a lubricant and a mold release agent are added in the range of 0.1 wt% to 5 wt%, the gold at the time of lens molding that occurs with the miniaturization of the lens shape The problems of poor peeling from the mold and ease of scratching can be improved. The function of the lubricant is closely related to the friction phenomenon that occurs between the objects, and it has a great effect on adjusting the frictional force between the polymer material and the processing machine during processing. make it easier. In addition, there is also an effect of improving the surface of the lens sheet after molding, which increases the slipperiness and prevents the tip of the lens element from being chipped and damaged.

  When the amount added is less than 0.1 wt%, the mold release property and the slipperiness of the resin composition may not be sufficiently improved. On the other hand, from the viewpoint of suppressing the occurrence of excessive bleed out, it is preferably 5 wt% or less. That is, the bleed out refers to a phenomenon in which components contained in the resin composition ooze out on the surface of the molded product. When excessive bleed out occurs, the appearance quality of the molded product may be impaired. In addition, the slidability and releasability are not dramatically improved. Rather, the amount added excessively may be wasted and increase the manufacturing cost.

  As the types of lubricants, hydrocarbons, fatty acids, fatty acid amides, esters, alcohols and the like can be raised as general lubricants, and known ones can be used. For example, stearin Various waxes such as zinc oxide, stearamide, kaunauba wax, mondan wax, polyethylene wax, paraffin wax, higher fatty acid alcohol, organopolysiloxane, anionic surfactant, cationic surfactant, amphoteric surfactant And nonionic surfactants, fluorine surfactants, organic carboxylic acids and derivatives thereof, fluorine resins, silicone resins, phosphate ester compounds, and organic or inorganic fine particles.

  The lens sheet 17 may be manufactured by a UV curing method. When prepared by the UV curing method, a UV curable resin is applied onto the lens substrate 17a which is a sheet-like substrate, a mold having a desired shape is pressed, and then UV irradiation is performed to form a lens substrate. A lens sheet 17 composed of 17a and a lens element 17b is obtained. As the sheet-like substrate, PET (polyethylene terephthalate), polycarbonate, acrylic, polypropylene films and the like well known in the art can be used. Here, when a lubricant and a mold release agent are added to the UV curable resin in the range of 0.1 wt% to 5 wt%, the lens shape becomes complicated and becomes finer. It is possible to improve the problem of peeling failure and ease of scratching.

  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 it becomes possible if materials are 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.

  If the lens sheet 17 according to the present embodiment is used, it is assumed that there is an impact such as vibration or dropping when transported or stored in a state where a plurality of manufactured lens sheets 17 are stacked and stored in a box or the like. However, since the slipperiness of the contacted part is improved, the optical element 17b is hardly damaged even if it is rubbed. In addition, even when something comes into contact with or collides with the surface of the lens sheet 17 in the state in which the lens sheet 17 is incorporated, the surface of the lens element 17b is improved so that the lens element 17b is not damaged. Not likely to occur.

Examples will be described below.
(Manufacturing method of optical sheet according to Comparative Examples 1 to 4 and Examples 1 to 4)
First, molds A, B, C, and D for preparing a lens sheet are prepared. The shape of the mold roll A is formed by arranging 90 ° prisms having a pitch of 66 μm and a tip curvature radius r of 5.0 μm. The shape of the mold roll B is formed by arranging 90 ° prisms having a pitch of 66 μm and a tip curvature radius r of 2.5 μm. The shape of the die roll C is formed by arranging 90 ° prisms having a pitch of 66 μm and a tip curvature radius r of 1.5 μm. The shape of the die roll D is formed by arranging 90 ° prisms having a pitch of 66 μm and a tip curvature radius r of 0.5 μm.

  Each of these mold rolls A, B, C, and D was arranged as a first mold roll in the vicinity of the extruder. The thermoplastic polycarbonate resin sheet was melted and molded by an extruder, and before the thermoplastic polycarbonate resin sheet was cooled and cured, it was molded by the first mold roll to obtain an extruded sheet having a lens, respectively. . As the thermoplastic polycarbonate, M1201Z manufactured by Teijin Chemicals Ltd. was used, and the thickness was adjusted to 320 μm. When making Comparative Examples 1, 2, 3, and 4, no lubricant is added. When Examples 1, 2, 3, and 4 are made, lubricant is appropriately added in the range of 0.1% to 5.0%. To create a lens sheet.

(Brightness measurement of each lens sheet)
Each of the obtained lens sheets was incorporated in an EL element as shown in FIG. 4, and the front luminance was measured with EZ-Contrast (product of ELDIM). Here, the luminance when the radius of curvature r of the prism apex is 5.0 μm was set to 1, and the luminance ratio was calculated based on this. The results are shown in Table 1 below together with the results of moldability and evaluation of scratches.

(Evaluation of damaged lens sheet)
Each of the obtained optical sheets in Comparative Examples 1 to 4 and Examples 1 to 4 is stacked 30 times, wrapped with a vinyl sheet, and this vinyl sheet is stacked and stored in a cardboard box. Of cushioning material. The cardboard box was subjected to a vibration test to evaluate whether or not each lens sheet was damaged on the lens element 17b. In the initial stage, a lens sheet having no scratch was packed, unpacked after the vibration test, and the number of scratched optical sheets was counted. In the vibration test, the random vibration specified in Appendix A Table 1 of JIS Z 0232 was applied. The vibration was performed for 30 minutes only in the normal direction (z direction) of the surface having the lens portion of the lens sheet. For the evaluation of the presence or absence of scratches, the lens sheet after vibration test is incorporated into the EL element, and there is a scratch if it is visible from any of the range of ± 80 ° in the vertical and horizontal directions with respect to the normal of the lens sheet center It was. The results are shown in Table 1. Those in which no defects were visually recognized were regarded as acceptable.

  From Table 1, even if the lubricant is not added, even if it can be molded, scratches are caused by the vibration test, and as the radius of curvature r at the apex decreases, the moldability deteriorates and the number of scratches by the vibration test increases. I understood. In addition, it was found that for those to which a lubricant was added, if the radius of curvature r at the apex of the prism lens was 1.5 μm or more and 2.5 μm or less, there was no problem in moldability and no damage was caused by a vibration test. When the curvature radius r of the prism lens apex is 0.5 μm, even if 5.0% or more is added, the number of scratches due to the vibration test cannot be eliminated, and the lens sheet becomes cloudy and has a good effect. I couldn't see it.

  In addition, as described above, such an EL element 10 can be used as a backlight device for a liquid crystal display, and can also be used as a digital signage device, a lighting device, or a light extraction film.

  In addition, the lens sheet used this time is an example, and is not limited only to the configuration according to the present invention.

DESCRIPTION OF SYMBOLS 1 Translucent substrate 2 Light emitting layer 3 Anode 4 Cathode 5 Lens sheet 5a Base material 5b Cylindrical lens element 6 Adhesive layer 10 EL element 11 Translucent base material 12 Light emitting layer 13 Anode 14 Cathode 15 Diffusion element 16 Adhesive layer 17 Lens sheet 17a Base film 17b Lens element

Claims (9)

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 is arranged along a surface of the lens sheet opposite to the base material, and includes a lens element that extracts light generated in the light emitting layer from the surface of the lens sheet opposite to the base material,
2. The EL element according to claim 1, wherein the lens element is a prism, and a curvature radius r of the apex of the prism is 1.5 μm or more and 2.5 μm or less.   The EL element according to claim 1, wherein a lubricant is added to the lens element in a range of 0.1 wt% to 5.0 wt%.   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.   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 4 or the illumination device according to claim 6 on a back surface of the image display element.   A light extraction film using the EL element according to claim 1.   The EL element according to claim 1, wherein an apex angle of the prism is 90 °.

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