JP2009266388A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element in which a good visibility can be secured even in a bright place in the surrounding. <P>SOLUTION: In the organic EL element, its transparent substrate has a diffusion and condensing function, and its diffusion angle satisfies the following formulae: the formula (1): 0<πtan(α/2)tan(β/2)<0.015 (in the case the condensed light image is a circle or an ellipse); the formula (2): 0<4tan(α/2)tan(β/2)<0.015 (in the case the condensed light image is nearly rectangular). In the both formulae, α: a minimum diffusion angle of substrate, β: a diffusion angle in a measurement direction nearly crossing the measurement direction that gives the minimum diffusion angle α, and 0°<α≤β<180°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL element, and more particularly to an organic EL element that can ensure good visibility even in a bright place.

  An organic EL element is a self-light emitting element in which a light emitting layer mainly composed of an organic compound is sandwiched between a pair of electrodes, at least one of which is transparent, and a current is passed to cause the layer to emit light, and light is extracted from the transparent electrode side. is there. Since it has excellent response speed and can be driven at low voltage and surface light emission, it is highly expected to be applied to displays, backlights, etc. that are required to be thin and light. However, the organic EL element has a problem that the extraction efficiency of light emitted from the light emitting layer is low. One of the causes is that light incident on the transparent substrate serving as the light exit surface escapes from the light exit surface to the side surface due to total reflection or scattering. In addition, since the light emitting layer is thin, light incident from the outside is easily transmitted and reflected by the electrode layer, so that the display tends to be metallic and the visibility is not good.

As means for solving these problems, an organic EL element (Patent Documents 1 and 2) in which random dot-like irregularities are formed on a transparent substrate and an electrode and a light emitting layer are laminated thereon has been proposed. . However, in these methods, the degree of improvement in visibility is low in places where the surroundings are very bright such as outdoors. On the other hand, an organic EL element in which a light emitting surface having a roof-type unevenness is formed on an electrode has also been proposed (Patent Document 3). However, in this case, since regular irregularities are provided on the substrate, moire tends to occur on the field of view, and it becomes difficult to provide a light emitting surface free from spots.
JP 2000-40584 A JP 2004-349064 A JP-A-9-115667

  This invention is made | formed in view of this point, and it aims at providing the organic EL element which can ensure favorable visibility also in the place where the circumference | surroundings are bright.

The organic EL device of the present invention includes a transparent substrate, a transparent electrode formed on the transparent substrate, a light emitting layer containing an organic compound formed on the transparent electrode, and an electrode formed on the light emitting layer. In the organic EL element having the above, the transparent substrate has a light incident surface on which light of the light emitting layer is incident, a light output surface that emits the light, the light incident surface has an uneven shape, and When parallel light is incident on the light incident surface from the normal direction of the light incident surface, the shape of the diffused light when the light emitted from the light output surface is observed from the normal direction of the light output surface is It is characterized by being circular or elliptical and having a shape sufficient for the diffusion angle to satisfy the following formula (1).
0 <π tan (α / 2) tan (β / 2) <0.015 (1)
α: Minimum diffusion angle of substrate, 0 ° <α <180 °
β: diffusion angle in the measurement direction substantially orthogonal to the measurement direction giving the minimum diffusion angle α, 0 ° <β <180 °

The organic EL device of the present invention includes a transparent substrate, a transparent electrode formed on the transparent substrate, a light emitting layer made of an organic compound formed on the transparent electrode, and an electrode formed on the light emitting layer. In the organic EL element having the above, the transparent substrate has a light incident surface on which light of the light emitting layer is incident, a light output surface that emits the light, the light incident surface has an uneven shape, and When parallel light is incident on the light incident surface from the normal direction of the light incident surface, the shape of the diffused light when the light emitted from the light output surface is observed from the normal direction of the light output surface is It is substantially rectangular and has a sufficient shape so that the diffusion angle satisfies the following formula (2).
0 <4 tan (α / 2) tan (β / 2) <0.015 (2)
α: Minimum diffusion angle of substrate, 0 ° <α <180 °
β: diffusion angle in the measurement direction substantially orthogonal to the measurement direction giving the minimum diffusion angle α, 0 ° <β <180 °

  In the organic EL device of the present invention, the transparent substrate is a flat glass or a resin flat plate, and the surface has a non-planar speckle structure having an uneven pitch of 50 μm to 500 μm and a height of 0.7 μm to 20 μm. Preferably it is formed. In this case, the transparent substrate is preferably composed of flat glass or a resin flat plate, and a surface layer laminated on the flat glass or resin flat plate and having the non-planar speckle structure, or The transparent substrate is preferably composed of flat glass or a resin flat plate, and a transparent resin film laminated on the flat glass or resin flat plate and having the non-planar speckle structure.

The organic EL device of the present invention includes a transparent substrate, a transparent electrode formed on the transparent substrate, a light emitting layer made of an organic compound formed on the transparent electrode, and an electrode formed on the light emitting layer. In the organic EL element having the above, the transparent substrate has a light incident surface on which light of the light emitting layer is incident, a light output surface that emits the light, the light incident surface has an uneven shape, and When parallel light is incident on the light incident surface from the normal direction of the light incident surface, the shape of the diffused light when the light emitted from the light output surface is observed from the normal direction of the light output surface is A circular or elliptical shape and the diffusion angle satisfies the following formula (1), or when a parallel ray is incident on the light incident surface from the normal direction of the light incident surface, When the emitted light is observed from the normal direction of the light exit surface, the shape of the diffused light is substantially rectangular. It becomes, and, because the diffusion angle has a sufficient shape to satisfy the following expression (2), can provide a device that better visibility in bright ambient light location can be obtained.
0 <π tan (α / 2) tan (β / 2) <0.015 (1)
0 <4 tan (α / 2) tan (β / 2) <0.015 (2)
α: Minimum diffusion angle of substrate, 0 ° <α <180 °
β: diffusion angle in the measurement direction substantially orthogonal to the measurement direction giving the minimum diffusion angle α, 0 ° <β <180 °

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

First, the transparent substrate will be described.
The transparent substrate used in the organic EL device of the present invention preferably has a total light transmittance of 80% or more, more preferably 85% or more, and still more preferably 90% or more. This is not the transmittance of each material but the transmittance of the entire laminate.

  This transparent substrate has a function of diffusing or condensing light incident from the light emitting layer into a circular shape, an elliptical shape, or a substantially rectangular shape. The approximate rectangle here refers to a rectangle with rounded corners. The concept of diffusion / condensing is shown in FIG. The light 1 incident from the lower surface of the transparent substrate is diffused and collected within a certain range by the transparent substrate 2 having a light control function. In order to define the degree of diffusion / condensation, a parameter called diffusion angle is used in the present invention. The diffusion angle is defined as the angle of incidence of the light incident from the direction perpendicular to the transparent substrate, passing through the transparent substrate 2 and emitted from the point O with respect to the incident angle, and measuring the luminance at the emission angle. This angle is an angle (FWHM: Full Width Half Maximum) that is twice the angle (half-value angle) at which the luminance attenuates to half of the peak luminance. In this measurement method, luminance is measured at equal angles on the circumference orthogonal to the plane centered on the point O on the plane of the transparent substrate 2, so that on the plane, the intersection of the plane and the measurement circumference A straight line is the measurement direction. Then, the brightness is measured by changing the direction by a certain angle on a straight line passing through the center O of the measurement circumference. In the present invention, this angle is a maximum of every 10 °, and the measurement direction is a minimum of 180 °. That is, it is synonymous with measuring the luminance of each point on the hemispherical surface S in FIG. Then, in each measurement direction, an angle (that is, a diffusion angle) at which the luminance becomes 1/2 of the peak luminance is determined. The FWHM can be obtained by measuring the light emission distribution of light incident from a normal angle of 0 ° using, for example, a variable angle color difference meter GC-5000L manufactured by Nippon Denshoku Industries Co., Ltd.

  Next, among these measured values, the minimum diffusion angle is defined as α, and the diffusion angle in a direction substantially orthogonal to the measurement direction giving α is defined as β. The diffusion angle β may not necessarily be the maximum value among the measured numerical values, but is at least α or more. In FIG. 1, the angle between 3a and 3a 'is α, and the angle between 3b and 3b' is β.

  When the transparent substrate of the present invention is irradiated with a parallel light beam such as a laser, the shape of the diffused light when the emitted light is observed from the light exit surface side with a line of sight parallel to the normal line of the light exit surface of the transparent substrate is , A circle or an ellipse, or a rectangle. In each of these cases, a relational expression with the diffusion angles α and β will be described.

  First, the case where the optical image is a circle or an ellipse will be described. Points 4a, 4a ′, 4b, and 4b ′ in FIG. 1 are intersection points of the hemispherical surface S, the light directions 3a and 3a ′ that give the diffusion angle α, and the light directions 3b and 3b ′ that give the diffusion angle β. . An ellipse passing through these and centering on the intersection of the hemispherical surface S and the normal H is a range in which a luminous flux having a luminance of 1/2 or more of the peak luminance is collected.

  When the light beam in this ellipse is projected onto a plane P that is in contact with the hemispherical surface S and parallel to the transparent substrate 2, the light image has the light directions 3 a and 3 a ′ giving the diffusion angle α and the diffusion angle β. It passes through the intersections 5a, 5a ', 5b and 5b' with the directions 3b and 3b 'of the light to be applied, and becomes an ellipse centered on the intersection of the plane P and the normal H. When the distance from the transparent substrate is 1, the area of this ellipse is given by π tan (α / 2) tan (β / 2). The narrower the area, the higher the light collecting property, and the wider, the higher the diffusibility.

In the case of the present invention, those having an elliptical area within the range of the following formula (5) can be used (where 0 <α ≦ β <180).
0 <π tan (α / 2) tan (β / 2) <0.015 (5)
The diffusion state includes isotropic diffusion and anisotropic diffusion. The isotropic diffusion is when α = β, and the light image projected on the plane P is circular, and its area is π tan2 (α / 2). In particular, when the optical image is a circle, the diffusion angles are almost the same in all measurement directions. On the other hand, anisotropic diffusion is in the case of α <β, and the light image projected on the plane P is elliptical, and the area is given by π tan (α / 2) tan (β / 2).

  Next, a case where the optical image is substantially rectangular will be described. A substantially rectangular shape means a rectangle with slightly rounded corners. The rectangle includes a rectangle and a square. Parallelograms and trapezoids do not belong to the category of the present invention. When the optical image projected on the plane P is a rectangle, 2 tan (α / 2) is the length of the short side of the rectangle, the long side orthogonal to this is 2 tan (β / 2), and the area of this rectangle is 4 tan (α / 2) tan (β / 2). In the case of a square, the area is 4 tan 2 (α / 2).

In the case of the present invention, those having the substantially rectangular area within the range of the following formula (6) can be used (where 0 <α ≦ β <180).
0 <4 tan (α / 2) tan (β / 2) <0.015 (6)
A case where the difference between α and β is large and the optical image is almost linear belongs to the category of the present invention.

  Regardless of whether the optical image is a circle, an ellipse, or a substantially rectangular shape, the range is set in consideration of the visibility of the element in the surrounding bright place. A preferred range is less than 0.006, and a more preferred range is less than 0.002.

  Examples of means for imparting the diffusion / condensing function as described above to the transparent substrate include optically controlling the surface structure of the transparent substrate. As an optical control method of the surface structure, it is preferable to provide a non-planar speckle structure on the surface. As described above, it is impossible to precisely control the condensing / diffusion, and the internal loss becomes large in the case of the irregular surface irregularities or the substrate in which the scattering agent is dispersed. If periodic irregularities are formed like a prism, moire tends to occur.

  The non-planar speckle structure is an uneven shape having a fine three-dimensional structure. This fine three-dimensional structure is composed of a plurality of uneven structures, and the height and pitch of the uneven shapes are irregular. The pattern is a pattern of random interference light that is generated when the coherent irradiation light is randomly scattered and the scattered waves are further superimposed, but by adjusting the size, shape, and direction of this pattern, the pattern is applied to the surface. The range of the diffusion angle of the transparent substrate can be controlled.

  The transparent substrate used in the present invention is preferably a transparent substrate whose diffusion angle is controlled by a non-planar speckle structure. In general, the range of the diffusion angle depends on the average size and shape of the speckle. If speckle is small, the angle range is wide. Further, if the speckle is an oblong in the horizontal direction, the shape of the angle distribution is an oblong in the vertical direction. Thus, the speckle pattern can be determined according to the desired directivity angle and diffusion angle. The diffusion angle may be controlled by changing the pitch, height, and aspect ratio of the concavo-convex structure, or may be controlled by changing the refractive index of the material forming the non-planar speckle structure. A detailed control method of the non-surface speckle structure that gives a predetermined diffusion angle is disclosed in Japanese Patent No. 3390954 and Japanese Patent Publication No. 11-513814.

  As a method for forming a speckle pattern, a means for recording a speckle pattern generated by interference exposure with a photoreactive resin is generally used. Although the recorded first pattern may be used as a final product as it is, a master type of this pattern is usually created and a copy thereof is used. Specifically, a submaster mold in which this pattern is recorded is manufactured, a metal is deposited on the submaster mold by a method such as electroforming, and a speckle pattern is transferred to the metal to manufacture a master mold. Then, the speckle pattern is transferred by performing a saddle shape with ultraviolet rays using the master mold. A detailed manufacturing method of this sub-master type is disclosed in Japanese Patent No. 3341519. All this content is included here.

In order to impart the non-planar speckle structure of the present invention to the surface of the transparent substrate, the following method may be mentioned.
(1) The surface of a glass substrate or a resin flat plate is softened by heating, and a speckle pattern master mold is pressed thereon to form a speckle pattern on the surface. Regarding this method, a detailed manufacturing method is described in JP-T-2002-523792.
(2) A polymer before curing is laminated on the surface of a glass substrate or a resin flat plate, and a speckle pattern master mold is pressed thereon to form a speckle pattern on the surface. Regarding the polymer, it is transparent, and is selected from thermosetting and photocurable. In the case of a glass substrate, a siloxane-based organic-inorganic hybrid polymer may be used. Regarding this method, a detailed manufacturing method is described in JP-T-2001-512245.
(3) A speckle pattern is recorded by laminating a photoreactive resin layer on the surface of a glass substrate or a resin flat plate and subjecting it to interference exposure.
(4) A resin film on which a speckle pattern is formed in advance is laminated on the flat plate surface.

  The speckle pattern size of the transparent substrate used in the present invention takes a random value when the interval between the peaks is 50 μm to 500 μm, and takes a random value when the height of the peaks is 0.7 μm to 20 μm. Yes, the range is defined in consideration of the color of the element due to interference and the roughness of the surface (definition of the element). A preferable range of the distance between the peaks is 100 μm to 400 μm. A preferable range of the height of the mountain is 1 μm to 10 μm.

Next, the material of the transparent substrate will be described.
As the material of the flat glass serving as the base of the transparent substrate, glass applicable to optical products, such as quartz glass, alkali-free glass, borosilicate glass, and aluminosilicate glass, is preferably used.

  In the case of a resin flat plate, a resin applicable to optical products is preferable. Specifically, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate phthalate (TAC) ), Cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, polyether ketone, polyimide, polyether sulfone (PES), polysulfones, poly Ether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic Le or polyarylates, polymethyl pentene or ARTON (trade name, manufactured by JSR Corporation), APEL (trade name, manufactured by Mitsui Chemicals, Inc.) film such as cycloolefin resins such. When the resin film itself on which the speckle pattern is formed is used as a transparent substrate, the film is preferably made of the above-mentioned material.

When a glass flat plate is not interposed in the transparent substrate, it is necessary that at least one of the resin flat plate and the resin film has at least one gas barrier layer. The light emitting layer of the organic EL is very easily deteriorated by oxygen or moisture, and thus the function of the gas barrier layer is to prevent these gases from entering. The required barrier property is preferably such that the water vapor permeability is 0.01 g / m ² · day · atm or less. More preferably, the oxygen permeability is 10 ⁻³ g / m ² / day or less, and the water vapor permeability is 10 −5 g / m ² / day or less. Examples of the material for the barrier layer include inorganic oxides such as SiOx, SiNx, and SiOxNy, organic-inorganic hybrid compounds formed by hydrolysis / condensation reactions of metal alkoxides, polysilazanes, layered silicon compounds (dispersions), and the like.

  The barrier layer can be formed by reactive sputtering, molecular beam epitaxy, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma polymerization method, plasma CVD method, laser CVD method, thermal CVD method. A coating method or the like is used. Moreover, the method which can form a film | membrane by application | coating of a dispersion liquid takes the method. There may be a plurality of barrier layers. Further, the bending durability is improved by providing a buffer layer such as a binder resin between the barrier layers. It may be provided on both surfaces of the resin film or the resin flat plate, and when both the resin film and the resin flat plate are used, a barrier layer may be provided on both of them. The thickness of the barrier layer is usually in the range of 0.01 μm to 0.2 μm. If it is too thin, the barrier property will be insufficient. If it is too thick, the barrier layer will be easily broken when bent, and flexibility cannot be expected.

  For photoreactive resins that form speckle patterns, the exposed areas become insoluble due to photocrosslinking reactions such as polyvinyl cinnamate and polyvinyl azide benzal, or the exposed areas become insoluble due to photopolymerization reactions such as acrylamide. The negative ones such as o-quinonediazide novolak resin, and the positive ones in which the quinonediazide group is easily soluble by generating a carboxylic acid by photolysis can be used.

  When the transparent substrate is entirely made of resin, the organic EL element is flexible and lightweight, and is less likely to be damaged, which is suitable for mobile use.

Next, the transparent electrode will be described.
As the transparent electrode, an ITO (indium / tin oxide) film, an IZO (indium / zinc oxide) film, or the like is used. As a method for forming the electrode layer, a general film forming method such as a sputtering method, a vacuum evaporation method, or a CVD method is used. Although the thickness of a transparent electrode layer is suitably selected in the range of 0.01 micrometer-1 micrometer, Preferably it is 0.03 micrometer-0.5 micrometer.

Next, the light emitting layer will be described.
Examples of the luminescent material are as follows. Examples of low molecular weight light emitting substances include 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolato) aluminum complex, tris (4-methyl). -8-quinolate) aluminum complex, bis (8-quinolate) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolate) aluminum complex, tris (4-methyl-5-cyano-8-quinolate) Aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4-Cyanophenyl) phenolate] aluminum complex, tris (8-quino) Norato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, poly-2,5-diheptyloxy-para-phenylene vinylene Etc.

  Also, coumarin phosphors, perylene phosphors, pyran phosphors, anthrone phosphors, polyphyrin phosphors, quinacridone phosphors, N, N′-dialkyl-substituted quinacridone phosphors, naphthalimide phosphors, A material obtained by dispersing a low molecular weight light-emitting substance such as an N, N′-diaryl-substituted pyrrolopyrrole-based phosphor or a phosphorescent light-emitting material such as an Ir complex in a polymer can also be used.

  Polymer light-emitting substances include polystyrene, polymethyl methacrylate, polyvinyl carbazole, poly (2-decyloxy-1,4-phenylene), and poly [2,5-bis- [2- (N, N, N-triethylammonium). Ethoxy] -1,4-phenyl-alt-1,4-phenylylene] dibromide, poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylenevinylene], poly [5-methoxy -(2-propanoxysulfonide) -1,4-phenylenevinylene], poly [2,5-bis- (hexyloxy) -1,4-phenylene- (1-cyanovinylene)], poly (9,9 -Dioctylfluorene), 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, 4,4'-bis (2,2'-diph) Nirubiniru) biphenyl, etc. polyspirofluorene the like.

  As a method for forming the light emitting layer, in addition to the sputtering method, the vacuum evaporation method, and the CVD method, a method in which the light emitting layer is dissolved in a solvent and applied by dipping, spin coating, casting, bar coating, roll coating or the like is also used. Although the thickness of a light emitting layer is suitably selected in the range of 0.01 micrometer-1 micrometer, Preferably it is 0.05 micrometer-0.2 micrometer.

  In order to improve the light emission efficiency, it is possible to insert another compound layer between the light emitting layer and the electrode. When the light emitting layer is a polymer compound, it is preferable to provide a hole injection layer or an electron injection layer between the light emitting layer and the electrode. The hole injection layer is provided between the anode and the light emitting layer, and the electron injection layer is provided between the cathode and the light emitting layer. For this, a substance having high carrier mobility and suitable matching with the electrode is selected. Specific examples of the hole injection layer material include polyaniline and polythiophene, and specific examples of the electron injection layer material include Ba and Ca.

  When the light emitting layer is a low molecular weight compound, it is preferable to further provide a transport layer between the light emitting layer and the injection layer. As the transport layer, a substance having a high carrier mobility is selected. Specific examples of the hole transport layer material include N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (abbreviated as TPD), Diamine derivatives such as N, N′-diphenyl-N, N′-bis (α-naphthyl) -1,1′-biphenyl-4,4′-diamine (abbreviated as α-NPD), 4,4 ′, 4 “-Tris (3-methylphenylphenylamino) -triphenylamine, starburst amine, etc. Specific examples of the electron transport layer include tris (8-quinolinol) aluminum complex (Alq3), 2- (4 -Biphenylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, bis {2- (4-t-butylphenyl) -1,3,4-oxadiazole} -m -Oxanes such as phenylene Examples include diazole derivatives, triazole derivatives, quinolinol-based metal complexes, etc. The thicknesses of the injection layer and the transport layer are appropriately determined to be about 0.01 μm to 0.1 μm.

Next, the metal electrode will be described.
Examples of the material for the metal electrode include Au, Pt, Ni, W, Cr, Mo, Fe, Co, Cu, Pd, Al, and alloys made of elements selected from these. To form the electrode film, sputtering, vapor deposition or the like is used. The thickness is appropriately selected in the range of 0.01 μm to 1 μm, preferably 0.05 μm to 0.2 μm.

  The organic EL element of the present invention is formed by sequentially laminating the above-mentioned layers. That is, a transparent substrate whose surface is optically controlled is disposed at the bottom, and a transparent electrode, a light emitting layer, and a metal electrode are laminated on the surface on which the uneven surface is formed. A transport layer / injection layer is appropriately inserted between the light emitting layer and the electrode. The optically controlled surface is at the outermost surface. The periphery is sealed with a passivation film to prevent gas intrusion. The material of the passivation film is almost the same as the material of the gas barrier film described above, an inorganic oxide such as SiOx, SiNx, SiOxNy, or an organic-inorganic hybrid compound formed by hydrolysis / condensation reaction of metal alkoxide, polysilazane, layered Examples thereof include silicon compounds (dispersions).

Next, the effect of the organic EL of the present invention will be described.
When the display using the organic EL element is used outdoors for mobile purposes, it has a problem in that the surroundings are bright and the contrast of the screen is lowered, resulting in poor visibility. On the other hand, the organic EL element of the present invention has an unexpected effect that visibility in the outdoors is improved. Although the reason for this is not clear, it is considered that the characteristics of the light emission surface of the organic EL element of the present invention have a strong light collecting function and thus provide high contrast despite the influence of external light. As the condensing function, it is considered that the same effect can be obtained by making the light emitting surface into a prism shape as in the technique described in Patent Document 3 described above. However, an element having regular unevenness avoids the generation of moire. hard. Since the light emission surface of the organic EL element of the present invention does not have a regular structure, it is possible to achieve both the visibility of the screen and the high contrast. Conventionally, in order to adjust the contrast, a circularly polarizing plate and a color filter have been used together. However, in the organic EL element of the present invention, it is not necessary to use these components only for adjusting the contrast.

Examples carried out to clarify the effects of the present invention will be described below.
[Example]
The luminance was measured using a two-dimensional color luminance meter (CA2000) manufactured by Konica Minolta. An organic EL element that emits white light was prepared as follows.

On a transparent alkali-free glass substrate (thickness: 1.0 mm), a diffusion sheet Light Shaping Diffusers manufactured by Luminit, USA, with 60 ° isotropic diffusion was pasted without an air layer (π tan (α / 2) tan (Β / 2) = 1.05). On top of this, ITO was deposited as a transparent electrode for the anode to a thickness of 0.01 μm by sputtering. The sheet resistance value at this time was 20 Ω / cm ² . Next, 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine is used as the hole injecting material, and the hole injecting material is deposited to a thickness of 60 nm. Thus, a hole injection layer was formed. Similarly, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl as a host and rubrene as a dopant were co-evaporated to form a first light emitting layer having a thickness of 20 nm. Formed.

  Next, 4,4′-bis (2,2′-diphenylvinyl) biphenyl as the host and 1,4-bis [4- (N, N-diphenylaminostyrylbenzene)] as the dopant were co-deposited. Thus, a second light emitting layer having a thickness of 40 nm was formed. This formed the white light emitting layer. Thereafter, tris (8-quinolinol) aluminum was deposited to a thickness of 20 nm to form an electron injection layer. Magnesium and silver were simultaneously deposited by vacuum deposition to form a cathode. The periphery of this laminate was sealed with a passivation film to produce an organic EL element.

  An element of the present invention was prepared by pasting a light emitting surface of a diffusion sheet Light Shaping Diffusers manufactured by Luminit, Inc., 5 ° isotropic diffusion without using an air layer (πtan (α / 2) tan). (Β / 2) = 0.006).

[Comparative Example 1]
An organic EL device was prepared in the same manner as in the example except that nothing was attached to the surface of the glass substrate.

[Comparative Example 2]
A prism sheet having a pitch of 50 μm and an apex angle of 90 ° was affixed to the outermost surface of the glass substrate, and an organic EL device in which an electrode layer and the like were laminated on the uneven surface in the same manner as in the example was produced.

Next, when the brightness of each element was adjusted to 100 cd / m ² and the visibility in a sunny day was visually evaluated, the organic EL element of the example had spots on the light-emitting surface. However, the device of Comparative Example 1 had a light exit surface that was very inferior in visibility. In the element of Comparative Example 2, moire was generated depending on the viewing angle, and a uniform light exit surface could not be obtained.

  The present invention can be applied as a light source of a backlight unit or a lighting fixture, but is particularly suitable for a backlight unit for mobile devices used outdoors.

It is a figure which shows the definition of the diffusion angle used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incident light 2 Board | substrate 3a, 3a 'Outgoing light which gives minimum diffusion angle (alpha) 3b, 3b' Outgoing light which gives diffusion angle (beta) substantially orthogonal to the direction which gives minimum diffusion angle (alpha) 4a, 4a 'Hemispherical surface S and diffusion angle Intersections 4b, 4b 'with hemispherical surface S and light directions 3b, 3b' providing diffusion angle β 5a, 5a 'with plane P and diffusion angle α Intersections with extension lines of light directions 3a, 3a '5b, 5b' Intersections of plane P and extension lines of light directions 3b, 3b 'giving diffusion angle β

Claims (5)

In the organic EL device having a transparent substrate, a transparent electrode formed on the transparent substrate, a light emitting layer containing an organic compound formed on the transparent electrode, and an electrode formed on the light emitting layer, The transparent substrate has a light incident surface on which light from the light emitting layer is incident and a light output surface from which the light is emitted, the light incident surface has an uneven shape, and the normal direction of the light incident surface Then, when parallel light is incident on the light incident surface, the shape of the diffused light when the light emitted from the light exit surface is observed from the normal direction of the light exit surface is circular or elliptical, and An organic EL device having a sufficient shape so that the diffusion angle satisfies the following formula (1).
0 <π tan (α / 2) tan (β / 2) <0.015 (1)
α: Minimum diffusion angle of substrate, 0 ° <α <180 °
β: diffusion angle in the measurement direction substantially orthogonal to the measurement direction giving the minimum diffusion angle α, 0 ° <β <180 ° In the organic EL element having a transparent substrate, a transparent electrode formed on the transparent substrate, a light emitting layer made of an organic compound formed on the transparent electrode, and an electrode formed on the light emitting layer, The transparent substrate has a light incident surface on which light from the light emitting layer is incident and a light output surface from which the light is emitted, the light incident surface has an uneven shape, and the normal direction of the light incident surface Therefore, when parallel light is incident on the light incident surface, the shape of the diffused light when the light emitted from the light exit surface is observed from the normal direction of the light exit surface is substantially rectangular, and the diffusion An organic EL element having an angle sufficient to satisfy the following formula (2).
0 <4 tan (α / 2) tan (β / 2) <0.015 (2)
α: Minimum diffusion angle of substrate, 0 ° <α <180 °
β: diffusion angle in the measurement direction substantially orthogonal to the measurement direction giving the minimum diffusion angle α, 0 ° <β <180 °   The transparent substrate is a flat glass or a resin flat plate, and a non-planar speckle structure having a concavo-convex pitch of 50 μm to 500 μm and a height of 0.7 μm to 20 μm is formed on the surface thereof. The organic EL element according to claim 1 or 2.   4. The organic material according to claim 3, wherein the transparent substrate comprises a flat glass or a resin flat plate, and a surface layer laminated on the flat glass or resin flat plate and having the non-planar speckle structure. EL element.   The said transparent substrate is comprised from a flat glass or a resin flat plate, and the transparent resin film laminated | stacked on this flat glass or a resin flat plate, and having the said non-planar speckle structure. Organic EL element.

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