JP5481825B2 - EL element and display device - Google Patents

Description

  The present invention relates to an EL element used for a flat panel display, for example, a backlight of a liquid crystal panel, an illumination light source, an electrical decoration, a sign light source, and a display device using the EL element.

  The organic EL element has a structure in which an element portion having an anode and a cathode and a light emitting layer containing a fluorescent organic compound sandwiched between the anode and the cathode is provided on one surface of a light-transmitting substrate. An organic EL element generates excitons by applying a DC voltage between an anode and a cathode, injecting electrons and holes into a light emitting layer and recombining them, and light generated when the excitons are deactivated. Light emission is generated using the release of.

  In such an EL element, there is a problem in that light from the light emitting layer is totally reflected by the light-transmitting substrate and a loss occurs. As a result of the loss, the external extraction efficiency of light is generally said to be about 20%. Therefore, there is a problem that the higher the brightness is, the more input power is required. In addition, when the input power is increased, the load on the element increases and the reliability of the element itself is lowered.

  Therefore, for the purpose of improving the external extraction efficiency of light, a lens sheet that forms fine irregularities is provided on the surface opposite to the surface on which the element portion of the light transmitting substrate is provided, and the light is once totally reflected by the light transmitting substrate. It has been proposed to extract light to the outside.

  FIG. 1 shows a cross-sectional view of an EL element provided with a conventional lens sheet. An element portion having an anode 3 and a cathode 4 and a light emitting layer 2 containing a fluorescent organic compound sandwiched therebetween is provided on the lower surface of the translucent substrate 1. A lens sheet in which a plurality of unit lenses 5 for forming fine irregularities on the translucent substrate 1a is formed on the upper surface of the translucent substrate 1 (the surface opposite to the surface on which the element portion is provided) is an adhesive layer 6. It is adhered by. The unit lens 5 in FIG. 1 has a cylindrical shape having two inclined surfaces and a top portion extending in a direction perpendicular to the paper surface to form a triangular pyramid. By arranging the unit lenses 5 in the lateral direction, it is possible to suppress the loss due to the total reflection of light and to increase the efficiency of taking out in the front direction.

  However, as shown in FIG. 1, when a lens sheet in which simple irregularities are formed by a cylindrical unit lens 5 having a triangular pyramid is used, the light intensity distribution within the viewing angle viewed from the observer side There is a problem that a lobe appears.

  FIG. 2 shows a simulation of the light intensity distribution within the viewing angle for the EL element of FIG. This simulation is performed in the case of using a lens sheet in which cylindrical-shaped unit lenses 5 are arranged in five rows of 150 μm. As shown in FIG. 2, large side lobes appear at an angle of about 70 degrees with respect to the front. For this reason, a phenomenon occurs in which the image becomes brighter or darker within the viewing angle.

In the lens sheet in which rounded unit lenses are arranged like a microlens shape, a gap must be provided between rounded unit lenses, and thus there is a problem that light is totally reflected in the gap. .
JP 2007-207471 A JP 2007-273275 A JP 2008-3515 A

  The present invention provides an EL element that can reduce a side lobe in a light intensity distribution within a viewing angle viewed from the observer side and improve light extraction efficiency, and a display device using such an EL element for a backlight unit. The purpose is to do.

The invention according to claim 1 is a translucent substrate, an element part provided on one side of the translucent substrate, an anode and a cathode, and a light emitting layer sandwiched therebetween, and the translucent substrate In the EL device having the lens portion and the lens sheet provided on the opposite surface, the lens sheet is adjacent to the plurality of cylindrical first lenses having two inclined surfaces and the top portion extending in the first direction. A second portion which is formed in a groove between two opposing inclined surfaces of the matching first lens and has two small inclined surfaces which are inclined in opposite directions along the first direction and whose top portion intersects the first direction. The ratio (S2 / S1) of the occupied area (S2) of the second lens to the occupied area (S1) of the first lens is 0.32. it is EL element which is a range of ～0.68

  The invention according to claim 2 is the EL element according to claim 1, wherein the first lens has a rounded top.

  A third aspect of the present invention is the EL element according to the first aspect, wherein the first lens has a curved surface.

  The invention according to claim 4 is the EL element according to claim 1, wherein any one of the anode and the cathode is light scattering.

  The invention according to claim 5 is the EL element according to claim 1, wherein any one of the anode and the cathode is light-transmitting.

  The invention according to claim 6 is characterized in that both the anode and the cathode are light transmissive, and has a light reflecting layer provided on the outer surface of the anode and the cathode on the outer side. The EL element described.

  The invention according to claim 7 is the EL device according to claim 1, wherein the light emitting layer includes a unit light emitting layer exhibiting two or more kinds of different emission colors.

  The invention according to claim 8 is the EL device according to claim 1, wherein the light emitting layer has a white light emission color.

  The invention according to claim 9 is the EL element according to claim 6, wherein the light reflecting layer is formed of a metal material.

  A tenth aspect of the present invention is a display device comprising: a display unit in which a plurality of EL elements according to any one of the first to ninth aspects are arranged; and a mechanism for driving the EL elements in pixels. .

  An eleventh aspect of the present invention is a display device comprising the backlight unit including the EL element according to any one of the first to ninth aspects and an image display panel.

  A twelfth aspect of the present invention is the display device according to the tenth aspect, wherein the image display panel is a liquid crystal display panel.

  Advantageous Effects of Invention According to the present invention, an EL element that can reduce side lobes in a light intensity distribution within a viewing angle viewed from the observer side and improve light extraction efficiency, and a display device using such an EL element for a backlight unit Can be provided.

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

  FIG. 3 shows a cross-sectional view of an EL element provided with a lens sheet according to an embodiment of the present invention. FIG. 4 is a perspective view of a lens sheet used in the EL element of FIG. FIG. 5 shows a plan view of a lens sheet used in the EL element of FIG.

  As shown in FIG. 3, an element portion having an anode 3 and a cathode 4 and a light emitting layer 2 containing a fluorescent organic compound sandwiched therebetween is provided on the lower surface of the translucent substrate 1. A lens sheet in which a plurality of first lenses 7 and a plurality of second lenses 8 are formed on a translucent substrate 1a on the upper surface of the translucent substrate 1 (the surface opposite to the surface on which the element portion is provided). Are bonded by an adhesive layer 6.

  With reference to FIG. 4, the shape of the 1st lens 7 and the 2nd lens 8 which comprise a lens sheet is demonstrated. One first lens 7 has two inclined surfaces p1 and p1 inclined in opposite directions, and has a cylindrical shape in which the apex r1 extends in the first direction (X direction in FIG. 4) to form a triangular pyramid. One second lens 8 is formed in a groove between two opposing inclined surfaces p1 and p1 of the adjacent first lenses 7 and 7, and tilts in opposite directions along the first direction (X direction). The top r2 has two small slopes p2 and p2 and extends in a second direction (Y direction) intersecting the first direction (X direction). Here, the term “small slope” for the second lens 8 indicates that the slope of the second lens 8 has a relatively small area compared to the slope of the first lens 7. Is intended.

  The angle formed by the inclined surface of the first lens 7 and the small inclined surface of the second lens 8 with respect to the main surface of the lens sheet (translucent substrate 1a) can be set in the range of 40 to 60 degrees. The highest efficiency is obtained when the apex angles of the first lens 7 and the second lens are 90 degrees. When the second lens 8 has a quadrangular pyramid shape, the front luminance can be increased compared to other polygonal pyramid shapes, and the light extraction efficiency can be increased. However, the shape of the second lens 8 is not particularly limited, and may be a conical shape, a hemispherical shape, a polygonal pyramid shape, or the like. The pitch of each lens is preferably set to 1 μm or more and 1 mm or less. When the lens pitch is 1 μm or less, a light diffraction phenomenon occurs. However, the diffusivity may be changed for each wavelength by making good use of this diffraction phenomenon.

  In the present invention, the ratio of the occupied area of the second lens 8 to the occupied area of the first lens 7 is designed to be 0.3 or more. The occupied area of the first lens 7 and the second lens 8 will be described with reference to FIG. The occupied area of the lens means a planar occupied area, that is, an occupied area when the lens is projected on a plane. In FIG. 5, the area S2 occupied by the second lens 8 is indicated by hatching. The occupied area S1 of the first lens 7 is a value obtained by subtracting the occupied area S2 of the second lens 8 from the total area of the lens sheet. The ratio of the occupied area in the present invention is S2 / S1, and this value may be 0.3 or more.

  Now, the height of the second lens 8 is the same as the height of the first lens 7, and the ends of two adjacent second lenses 8 at the groove between the two inclined surfaces facing each other of the adjacent first lenses 7. When the lens sheet is designed such that the portions are in point contact with each other, the ratio of the occupied area of the second lens 8 to the occupied area of the first lens 7 (S2 / S1) is 1. Such a lens sheet is considered to exhibit an optimum effect for reducing the side lobe in the light intensity distribution within the viewing angle viewed from the observer side.

  However, the ratio of the occupied area of the second lens 8 to the occupied area of the first lens 7 (S2 / S1) can be designed to be smaller than 1, and the value of (S2 / S1) is 0.3 or more. If present, the effect of eliminating side lobes in the light intensity distribution within the viewing angle can be obtained. Actually, considering the ease of designing the lens sheet, the ratio of the occupied area of the second lens 8 to the occupied area of the first lens 7 (S2 / S1) is usually designed to be smaller than 1. .

  FIG. 6 shows a simulation of the light intensity distribution within the viewing angle for an example of the EL element according to the present invention. In this simulation, the cylindrical first lenses 7 having a triangular pyramid are arranged in five rows of 150 μm, and the height of the first lens 7 is higher than that of the first lens 7 in the groove between the two inclined surfaces facing each other. This is performed for a case where a lens sheet in which five second lenses each having a low value are formed is used. As shown in FIG. 6, the light intensity decreases almost monotonously without increasing in the viewing angle range from the front to the side, there is no side lobe in the light intensity distribution within the viewing angle, and the light intensity distribution is broad. Become.

  Note that the value of (S2 / S1) may exceed 1 and become about 1.1 depending on the processing accuracy of a stamper used for manufacturing a lens sheet, which will be described later. Therefore, the value of (S2 / S1) in the present invention may be in the range of 0.3 to 1.1, and more preferably in the range of 0.4 to 0.9.

  In FIG. 3, a lens sheet having a multilayer structure in which a plurality of first lenses 7 and a plurality of second lenses 8 are formed on a translucent substrate 1a is used, but the lens sheet may have a single layer structure. The material of the translucent substrate 1a is not particularly limited, but typically, a polyethylene terephthalate resin is used. The first lens 7 and the second lens 8 are made of a resin, for example, a thermoplastic resin such as an acrylic resin, a polycarbonate resin, a styrene resin, an acrylic styrene copolymer resin, a thermoplastic resin such as a polyethylene terephthalate resin, or an ultraviolet curable resin. Also, ionizing radiation curable resins such as electron beam curable resins are used.

  The lens sheet can be formed, for example, by a method using a stamper. As the stamper, for example, a flat stamper or a roll stamper can be used. The method using the roll stamper is superior in productivity as compared with the method using the flat stamper.

  The roll stamper can be manufactured, for example, by the following method. First, a roll having a copper plating layer formed on the roll surface is prepared. Next, using a cutting tool, the copper plating layer on the roll surface is cut along one direction to form a groove, and then the copper plating layer on the roll surface is cut along a direction orthogonal to form the groove. . By these cutting processes, grooves corresponding to the first lens and grooves corresponding to the second lens are formed on the roll surface.

  Next, for example, a thermoplastic resin is used as a material for the lens, and the heated stamper is pressed against the thermoplastic resin to transfer the concavo-convex structure of the stamper to the resin, and is removed from the stamper to obtain a lens sheet. Alternatively, an ultraviolet curable resin is supplied between the translucent substrate and the stamper, the ultraviolet curable resin is irradiated with ultraviolet rays and cured, and then the cured ultraviolet curable resin is removed from the stamper together with the substrate. Get.

  As described above, when a stamper is formed by cutting a copper plating layer formed on the roll surface with a cutting tool, depending on the processing accuracy, each groove corresponding to the height of each of the first lens and the second lens is formed. The depth may not be as designed, and a first lens and a second lens having various dimensions may be formed.

  FIG. 7 shows a cross-sectional view of an EL device according to another embodiment of the present invention. In this EL element, dimensions such as height and pitch of the plurality of first lenses 7 are variously different.

  FIG. 8 is a perspective view of a lens sheet according to another embodiment of the present invention. In this lens sheet, not only the dimensions such as the height and pitch of the plurality of first lenses 7 are different, but also the dimensions such as the height and pitch of the plurality of second lenses 8 are different. Yes. There is also a portion where the height of the second lens 8 is higher than the height of the first lens 7.

  In the present invention, even if the first lens and the second lens constituting the lens sheet are formed with various dimensions, the ratio of the occupied area of the second lens to the occupied area of the first lens is 0. If it is .3 or more, the effect of reducing the side lobe in the light intensity distribution within the viewing angle viewed from the observer side can be obtained.

  Hereinafter, a lens sheet according to another embodiment of the present invention will be described.

  FIG. 9A is a cross-sectional view showing a lens sheet in which the first lens 7 and the second lens 8 contain diffusible fine particles. By mixing diffusible fine particles into the first lens 7 and the second lens 8, the angular dependence of the emitted light can be relaxed, and the light intensity distribution within the viewing angle can be controlled.

  FIG. 9B is a cross-sectional view showing a lens sheet in which the translucent substrate 1a contains diffusible fine particles. By mixing diffusible fine particles into the translucent substrate 1a, the angle dependence of the emitted light can be relaxed, and the light intensity distribution within the viewing angle can be controlled.

  FIG. 9C is a cross-sectional view showing a lens sheet in which the tops of the first lens 7 and the second lens 8 are rounded. In this way, by rounding the tops of the first lens 7 and the second lens 8, the abrasion resistance of the lens sheet can be improved.

  FIG. 10A is a cross-sectional view showing a lens sheet in which one inclined surface of the first lens 7 is a curved surface. The second lens 8 may also have the same shape as the first lens 7. FIG. 10B is a cross-sectional view showing a lens sheet in which both inclined surfaces of the first lens 7 are curved surfaces. The second lens 8 may also have the same shape as the first lens 7. In this way, by providing a certain curvature on the slope of the first lens 7 (and the second lens 8), the light intensity distribution within the viewing angle can be advantageously controlled.

  Hereinafter, EL elements according to other embodiments of the present invention will be described.

  FIG. 11 is a cross-sectional view showing an EL element in which at least one of the anode and the cathode (here, the cathode 4 on the outside) is light scattering. Thus, by making an electrode light-scattering, the light intensity distribution nonuniformity in an EL element can be reduced. In addition, the retroreflected light from the lens sheet is further scattered and returned to the exit surface.

  FIG. 12 is a cross-sectional view showing an EL element in which at least one of the anode and the cathode (in this case, the anode 3 inside) is a light transmissive electrode. In this EL element, light emitted from the light emitting layer 2 is emitted from the anode 3, and there is a lens sheet on the extension in the direction, and light can be extracted.

  FIG. 13 is a cross-sectional view showing an EL device having a light reflecting layer 9 provided on the outer surface of the cathode 4 on the outside, in which both the anode 3 and the cathode 4 are light transmissive. The distance between the light reflecting layer 9 and the light emitting layer 2 is set so that substantially no optical interference occurs. The material of the light reflecting layer 9 is not particularly limited, but a simple metal such as Al, Zr, Ti, Y, Sc, Ag, In, alkali metal, alkaline earth metal, rare earth metal, or an alloy of these metals, or oxide , Halides, combined use of metal-doped organic layers, and the like. In this EL element, optical interference can be reduced by controlling the distance between the light reflecting layer 9 and the light emitting layer 2, and stray light having angle dependency and wavelength dependency can be reduced.

  FIG. 14 is a cross-sectional view showing an EL element in which a thin film transistor (TFT) layer 10 is provided on the outside of an element portion having an anode 3 and a cathode 4 and a light emitting layer 2 sandwiched between them. A plurality of EL elements are arranged in the element portion. The TFT layer 10 is formed on the lower substrate 11. By providing the TFT layer 10 in this way, it can also be used as an active matrix type display in which a plurality of arranged EL elements are driven. Note that the EL element according to the present invention is not limited to an active matrix type, and can also be used as a passive type display. In that case, the anode 3 and the cathode 4 are formed in a stripe structure.

  FIG. 15 is a cross-sectional view showing a liquid crystal display device using the EL element according to the present invention in the backlight unit of the liquid crystal panel 12. A plurality of EL elements are arranged in the backlight unit of the liquid crystal display device. As described above, the liquid crystal display device using the backlight unit including the EL element according to the present invention has a structure more than that using the backlight unit including the cold cathode tube (CCFL) as the light source as in the past. Thinning can be achieved and power consumption can be reduced. Further, since there is substantially no unevenness of the light source, a diffusion plate and a lens sheet for reducing the lamp image as in the conventional case are not necessary, and the cost is reduced.

  FIG. 16 is a cross-sectional view showing an EL element in which a light diffusion layer is provided near the tip of the lens sheet. In this EL element, the light extracted from the lens sheet can be scattered by the light diffusion layer 15. In addition, there is also an advantage that the adhesion force is increased by a protrusion near the tip of the lens sheet.

  Examples of the present invention will be described below.

Example 1
As shown in FIG. 4, the cylindrical first lenses 7 forming a triangular pyramid are arranged in five rows of 150 μm, and the first lens 7 is inserted into a groove between two opposed inclined surfaces of the adjacent first lenses 7. A lens sheet in which five second lenses each having a low height were formed.

  As shown in FIG. 5, on the plane, the length of the apex r2 of the second lens 8 is set to 80% of the interval between the apexes of the two adjacent first lenses 7, and the adjacent first lenses 7 are adjacent to each other. The lens sheet was designed such that the second lenses 8 are formed at a uniform pitch and spaced apart from each other in the groove between the two opposing slopes. In this case, the ratio of the occupied area of the second lens 8 to the occupied area of the first lens 7 (S2 / S1) is about 0.47.

  When the light intensity distribution within the viewing angle was simulated for the EL element using this lens sheet, no side lobe was found in the light intensity distribution as shown in FIG.

Other Embodiments In a lens sheet designed similar to the above in which the length of the apex r2 of the second lens 8 is 90% of the interval between the apexes of two adjacent first lenses 7, (S2 / S1) is It becomes about 0.68.

  In a lens sheet designed similar to the above in which the length of the apex r2 of the second lens 8 is 70% of the interval between the apexes of two adjacent first lenses 7, (S2 / S1) is about 0.32. It becomes.

  Similarly, when the light intensity distribution within the viewing angle was simulated for EL elements using these lens sheets, no side lobe was observed in the light intensity distribution.

Sectional drawing of the EL element which provided the conventional lens sheet. The figure which simulated light intensity distribution within a viewing angle about the EL element of FIG. Sectional drawing of the EL element which provided the lens sheet which concerns on one Embodiment of this invention. The perspective view which shows the lens sheet used in one Embodiment of this invention. The top view which shows the lens sheet used in one Embodiment of this invention. The figure which simulated the light intensity distribution within a viewing angle about the EL element of FIG. Sectional drawing of the EL element which concerns on other embodiment of this invention. The perspective view which shows the lens sheet used in other embodiment of this invention. Sectional drawing which shows the lens sheet used in other embodiment of this invention. Sectional drawing which shows the lens sheet used in other embodiment of this invention. Sectional drawing of the EL element which concerns on other embodiment of this invention. Sectional drawing of the EL element which concerns on other embodiment of this invention. Sectional drawing of the EL element which concerns on other embodiment of this invention. Sectional drawing which shows the display apparatus using the EL element which concerns on this invention. Sectional drawing which shows the liquid crystal display device which used the EL element which concerns on this invention for the backlight unit. Sectional drawing of the EL element which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Translucent substrate, 1a ... Translucent base material, 2 ... Light emitting layer, 3 ... Anode, 4 ... Cathode, 5 ... Unit lens, 6 ... Adhesive layer, 7 ... 1st lens, 8 ... 1st Lens, 9 ... Light reflecting layer, 10 ... Thin film transistor (TFT) layer, 11 ... Lower substrate, 12 ... Liquid crystal panel, 15 ... Light diffusion layer.

Claims (12)

An element portion having a light-transmitting substrate, an anode and a cathode, and a light-emitting layer sandwiched between the anode and the cathode, provided on one surface of the light-transmitting substrate; In an EL element having a lens sheet provided,
The lens sheet is formed in a groove portion between a plurality of cylindrically shaped first lenses having two inclined surfaces and a top portion extending in a first direction, and two adjacent inclined surfaces of the adjacent first lenses, A plurality of second lenses having two small slopes inclined in opposite directions along the first direction and having a top portion extending in a second direction intersecting the first direction, A ratio (S2 / S1) of an area (S2) of the second lens to an area (S1) of the second lens is in a range of 0.32 to 0.68 .   The EL device according to claim 1, wherein the first lens has a rounded top.   The EL device according to claim 1, wherein the first lens has a curved surface.   2. The EL device according to claim 1, wherein any one of the anode and the cathode is light scattering.   2. The EL device according to claim 1, wherein one of the anode and the cathode is light transmissive.   2. The EL device according to claim 1, wherein both of the anode and the cathode are light-transmitting and have a light reflection layer provided on an outer surface of the anode and the cathode on the outer side.   The EL device according to claim 1, wherein the light emitting layer includes a unit light emitting layer exhibiting two or more different emission colors.   The EL device according to claim 1, wherein the light emitting layer emits white light.   The EL device according to claim 6, wherein the light reflecting layer is made of a metal material.   10. A display device comprising: a display unit in which a plurality of EL elements according to claim 1 are arranged; and a mechanism for driving the EL elements with pixels.   A display device comprising: a backlight unit including the EL element according to claim 1; and an image display panel.   The display device according to claim 11, wherein the image display panel is a liquid crystal panel.

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