JP2012243495A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element improved in light extraction efficiency and also reduced in color shifts, with a simplified constitution.SOLUTION: In a light emitting element 10 including, on a transparent substrate, a light extraction surface having an uneven structure, the uneven structure is formed of a plane part 20b and a recessed part 20a recessed from the plane part 20b, a proportion of the area of the plane part 20b relative to an area obtained by projecting the light extraction surface in the direction perpendicular to the plane part 20b is 0-25%, an aspect ratio of the depth h2 of the recessed part 20a relative to the length d2 of an opening of the recessed part 20a is 0.25-0.3, and, when n represents a refractive index of the transparent substrate, a light distribution in air of the transparent substrate is less than 1/n.

Description

  The present invention relates to a light emitting element having a light extraction surface with a concavo-convex structure.

  At present, organic light-emitting elements and LEDs (Light Emitting Diodes) are attracting attention as thin light-emitting materials. For example, an organic light emitting device can obtain high luminance with low power, and is excellent in terms of visibility, response speed, life, and power consumption. On the other hand, the light use efficiency of the organic light emitting device is about 20%, and the loss in the device is large.

  FIG. 23 is a schematic cross-sectional view of a conventional organic light emitting device. The organic light emitting device 100 includes a metal electrode 101, an organic light emitting layer 102 having a refractive index of about 1.8, a transparent electrode 103 having a refractive index of about 1.8, and a refractive index of about 1.5 in order from the lower layer in the figure. The transparent substrate 104 is laminated. The arrows 110a to 110e in the figure indicate characteristic light among the light generated from the organic light emitting layer 102.

  The light 110a is light in a direction perpendicular to the organic light emitting layer 102 which is a light emitting surface, and is transmitted through the transparent substrate 104 and extracted to the light extraction side (air side). The light 110b is light that is incident on the interface between the transparent substrate 104 and air at a shallow angle less than the critical angle, and is refracted at the interface between the transparent substrate 104 and air and extracted to the light extraction side. The light 110c is light that is incident on the interface between the transparent substrate 104 and air at an angle deeper than the critical angle, and is light that is totally reflected at the interface between the transparent substrate 104 and air and cannot be extracted to the light extraction side. The loss due to this is called substrate loss, and there is usually a loss of about 20%.

  The light 110 d is light that satisfies the resonance condition among light incident on the interface between the transparent electrode 103 and the transparent substrate 104 at an angle deeper than the critical angle, and is totally reflected at the interface between the transparent electrode 103 and the transparent substrate 104. The light is generated in a waveguide mode and confined in the organic light emitting layer 102 and the transparent electrode 103. The loss due to this is called waveguide loss, and there is usually a loss of about 20 to 25%. The light 110 e is light that is incident on the metal electrode 101, interacts with free electrons in the metal electrode 101, generates a plasmon mode that is a kind of waveguide mode, and is confined in the vicinity of the surface of the metal electrode 101. The loss due to this is called plasmon loss, and there is usually a loss of about 30 to 40%.

  As described above, the conventional organic light emitting device 100 has substrate loss, waveguide loss, and plasmon loss. Therefore, it is a problem to reduce these losses and extract more light.

  For example, Patent Document 1 discloses a configuration in which a microlens sheet is provided on a substrate surface in order to reduce substrate loss and improve light extraction efficiency. Patent Document 2 discloses a configuration in which a light diffusion layer is provided on the substrate surface in order to reduce substrate loss and improve light extraction efficiency. In Patent Document 3, an uneven structure layer containing a transparent resin and fine particles is provided on the substrate surface in order to reduce substrate loss and improve light extraction efficiency, and to reduce changes in color depending on the observation angle. The configuration is disclosed.

JP 2010-123436 A Japanese Patent No. 4393788 Japanese Patent No. 4614012

  The techniques of the above Patent Documents 1 and 2 are intended to reduce the substrate loss and improve the light extraction efficiency by devising the shape of the interface of the transparent substrate with the air. In addition, a change in color depending on the viewing angle, so-called color shift, is to be reduced.

  As described above, since the configurations of Patent Documents 1 and 2 can solve only one problem (improvement of light extraction efficiency), another configuration must be added to solve the problem of color misregistration. On the other hand, the configuration of Patent Document 3 can solve two problems. However, in the configuration of Patent Document 3, fine particles must be mixed into the concavo-convex structure, which is a complicated configuration. When the configuration becomes complicated, productivity is lowered and costs are increased. These problems are not only applicable to organic light emitting elements but also to other light emitting elements such as LEDs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting element that improves light extraction efficiency with a simple structure and reduces color misregistration.

In order to achieve the above object, the present invention provides a light emitting device having a light extraction surface with a concavo-convex structure on a transparent substrate, wherein the concavo-convex structure protrudes from a flat portion and a concave portion or a flat portion recessed from the flat portion. The ratio of the area of the plane portion to the area of the light extraction surface projected in the direction perpendicular to the plane portion is 0 to 25%, and the recess with respect to the length of the opening of the recess When the aspect ratio of the depth of the protrusion or the aspect ratio of the height of the protrusion to the length of the base of the protrusion is 0.25 to 0.3, and the refractive index of the transparent substrate is n, The air distribution of the transparent substrate is smaller than 1 / n ² .

  In the above light-emitting element, it is desirable that the shape of the concave portion or the convex portion is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid.

In the light-emitting element having a light extraction surface with a concavo-convex structure on a transparent substrate, the concavo-convex structure is formed by a flat portion and a concave portion recessed from the flat portion, and the light extraction surface is the flat portion. The ratio of the area of the plane portion to the area projected in the direction perpendicular to the direction is 0 to 25%, the aspect ratio of the depth of the recess to the length of the opening of the recess is 0.75 or more, When the refractive index of the transparent substrate is n, the air light distribution of the transparent substrate is smaller than 1 / n ² .

  In the above light emitting device, it is preferable that the shape of the concave portion is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid.

According to the present invention, in the light-emitting element having a light extraction surface with a concavo-convex structure on a transparent substrate, the concavo-convex structure is formed by a flat portion and a convex portion protruding from the flat portion, and the light extraction surface is the flat surface. The ratio of the area of the plane part to the area projected in the direction perpendicular to the part is 0 to 25%, and the aspect ratio of the height of the convex part to the length of the base part of the convex part is 1.0 or more. When the refractive index of the transparent substrate is n, the air light distribution of the transparent substrate is smaller than 1 / n ² .

  In the above light-emitting element, it is desirable that the shape of the convex portion is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid.

  In the above light emitting device, it is desirable that the uneven structure and the transparent substrate have the same refractive index.

  In the above light emitting device, it is desirable that the concavo-convex structure and the transparent substrate have a refractive index close to each other.

  According to the present invention, by optimizing the aspect ratio of the concavo-convex structure of the light extraction surface, the ratio of the area of the flat portion, and the air light distribution of the transparent substrate, the light extraction efficiency is improved with a simple configuration, and the color Misalignment can also be reduced.

It is a schematic sectional drawing of the organic light emitting element of one Embodiment of this invention. It is a partial top view of FIG. It is an enlarged view of the micro lens sheet | seat part of FIG. It is sectional drawing of the uneven structure of an elliptical hemisphere of a <0.5. It is sectional drawing of the uneven structure of the hemisphere of a = 0.5. It is sectional drawing of the uneven structure of an elliptical hemisphere of a> 0.5. It is a graph which shows the relationship of the single surface transmittance | permeability with respect to an aspect ratio. It is a figure which shows the light distribution in the transparent substrate at the time of omitting a microlens sheet | seat from the organic light emitting element of one Embodiment of this invention. It is a figure which shows air light distribution when a microlens sheet | seat is abbreviate | omitted from the organic light emitting element of one Embodiment of this invention. It is a graph which shows the light extraction efficiency at the time of changing the aspect-ratio of a convex part. It is a graph which shows the color shift at the time of changing the aspect-ratio of a convex part. It is sectional drawing of the uneven structure which has a recessed part of an elliptical hemisphere. FIG. 13 is a plan view of FIG. 12. It is a graph which shows the light extraction efficiency at the time of changing the aspect-ratio of a recessed part. It is a graph which shows the color shift at the time of changing the aspect-ratio of a recessed part. It is sectional drawing of the uneven structure which has a convex part of a regular quadrangular pyramid. FIG. 17 is a plan view of FIG. 16. It is sectional drawing of the uneven structure which has a concave part of a regular quadrangular pyramid. It is a top view of FIG. It is the graph which showed the light extraction efficiency with respect to the aspect-ratio in the uneven structure which has a recessed part of a regular tetragonal pyramid about various area ratios of a plane part. It is the graph which showed the color shift with respect to the aspect-ratio in the uneven structure which has a recessed part of a regular quadrangular pyramid about various area ratios of a plane part. It is a figure which shows the evaluation result of Examples 1-10 and Comparative Examples 1-5. It is a schematic sectional drawing of the conventional organic light emitting element.

  As an example of the light-emitting element of the present invention, the following embodiment will be described using an organic light-emitting element, but it can be similarly applied to various light-emitting elements such as inorganic light-emitting elements and LEDs.

<Configuration of organic light-emitting element>
FIG. 1 is a schematic cross-sectional view of an organic light-emitting device according to an embodiment of the present invention, and FIG. 2 is a plan view of a part thereof. The organic light emitting element 10 is configured by laminating a back electrode 11, an organic light emitting layer 12, a transparent electrode 13, a transparent substrate 14, and a microlens sheet 15 in order from the lower layer in the drawing. The organic light emitting device 10 is a so-called bottom emission method.

  For convenience of explanation, in FIG. 1, the left-right direction of the paper surface is defined as the X direction, the direction perpendicular to the paper surface is defined as the Y direction, and the vertical direction of the paper surface (stacking direction of each layer) is defined as the Z direction.

  The back electrode 11 has a role as an anode or a cathode and a role as a mirror that reflects light to the transparent substrate 14 side. For example, the reflectance of aluminum, silver, nickel, titanium, sodium, calcium, etc. is 60% or more. A metal material or an alloy containing any of them can be used.

  The organic light emitting layer 12 is a single layer or a plurality of layers of an organic compound or complex including a light emitting layer. For example, a hole transport layer in contact with the anode, a light emitting layer formed of a light emitting material, an electron transport layer in contact with the cathode, or the like. Thus, the thickness is several nm to several hundred nm. The refractive index is around 1.8. Further, a lithium fluoride layer, an inorganic metal salt layer, or a layer containing them may be formed at an arbitrary position. The light emitting layer is made of at least one kind of light emitting material, and a fluorescent light emitting compound or a phosphorescent light emitting compound can be used.

As the configuration of the organic light emitting layer 12, for example, the following configurations (i) to (v) can be adopted including the above-described configuration.
(I) (anode) / light emitting layer / electron transport layer / (cathode)
(Ii) (anode) / hole transport layer / light emitting layer / electron transport layer / (cathode)
(Iii) (anode) / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / (cathode)
(Iv) (anode) / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / (cathode)
(V) (anode) / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / (cathode)

  The hole transport layer is made of a material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

  The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking.

  The hole injection layer and the electron injection layer are layers provided between the electrode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance.

The transparent electrode 13 is an opposite electrode to the back electrode 11, and for example, a conductive transparent material having a transmittance of 40% or more such as CuI, indium tin oxide (ITO), SnO ₂ , ZnO, or the like can be used. The refractive index is around 1.8, similar to the organic light emitting layer 12.

  The transparent substrate 14 is a transparent material, and has a thickness of 0.1 to 1 mm, for example. The refractive index is about 1.5 to about 1.8.

  As the transparent substrate 14, for example, a resin such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), crystal, or the like can be used. Preferably, it is a resin film which can give flexibility to an organic light emitting element. By forming the transparent substrate 14 with a flexible film-like base material, the surface light source can be curved and light can be emitted in various directions.

  The microlens sheet 15 is an element that changes the angle of light, and the surface on the light extraction side (light extraction surface) may be an uneven shape (uneven structure). For example, an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, A concave or convex shape such as a quadrangular frustum, other pyramids, a pyramidal frustum or the like can be adopted. In FIG. 1, a convex elliptical hemisphere is employed.

  As shown in FIG. 2, the concave-convex structure of the microlens sheet 15 is formed by an elliptical hemispherical convex portion 15a and a flat portion 15b (XY plane) of a gap between the convex portions 15a. In other words, the concavo-convex structure of the microlens sheet 15 is formed by the flat surface portion 15b and the convex portion 15a protruding from the flat surface portion 15b.

  As a result, the light 110c shown in FIG. 23, which is totally reflected at the interface between the transparent substrate and the air and cannot be extracted to the light extraction side, is incident on the microlens sheet 15, and the angle is changed by the concave-convex structure. The light is extracted as 16a and 16b, or becomes light 16c to 16e due to reflection at different angles, and is incident on the microlens sheet 15 again and extracted.

The microlens sheet 15 preferably has a refractive index close to that of the transparent substrate 14 from the viewpoint of suppressing Fresnel reflection and total reflection at the boundary with the transparent substrate 14 (for example, the refractive index of the transparent substrate is 1). .5, the refractive index of the microlens sheet is 1.4 to 1.6),
It is most desirable to have the same refractive index as that of the transparent substrate 14 (for example, the refractive index of the transparent substrate and the microlens sheet is 1.5).

  And the transparent electrode 13, the organic light emitting layer 12, and the back electrode 11 are laminated | stacked on the transparent substrate 14 which stuck the micro lens sheet | seat 15, the transparent electrode 13 is exposed at one edge part, and the other edge part is exposed. The back electrode 11 is exposed to form an electrode portion, this electrode portion is connected to each power wiring (not shown) of a power source portion (not shown), and a predetermined DC voltage is applied to the organic light emitting layer 12 to emit light. Let

  Since the light extraction surface of the organic light emitting element only needs to have a concavo-convex structure, the concavo-convex structure may be formed on the surface of the transparent substrate 14 by transfer or the like instead of the microlens sheet 15.

  In addition, since the organic compound which comprises the organic light emitting element 10 deteriorates with a water | moisture content or oxygen in air | atmosphere, it seals with a moisture permeation prevention layer (gas barrier layer), and is used by interrupting | blocking from external atmosphere. This moisture permeation preventive layer can be formed by, for example, a high frequency sputtering method.

<Method for manufacturing organic light-emitting element>
Next, as an example of a method for producing the organic light emitting device 10, a microlens sheet / transparent substrate / anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode A method for manufacturing an element composed of the above will be described.

  First, a thin film of a transparent electrode 13 made of an anode material is formed on a transparent substrate 14 with a microlens sheet 15 attached thereto by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 nm to 200 nm. To produce an anode.

  Then, an organic compound thin film such as a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer, which is the organic light emitting layer 12, is formed thereon.

  As a method for forming each of these layers, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, printing method), etc., and it is easy to obtain a uniform film and it is difficult to generate pinholes. Is preferably formed by a coating method such as a spin coating method, an ink jet method, or a printing method.

  Examples of the liquid medium for dissolving or dispersing the organic light emitting layer 12 include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, mesitylene, and cyclohexylbenzene. Aromatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used. Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

  After these layers are formed, a thin film of the back electrode 11 made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 50 nm to 200 nm. To produce a cathode. In this way, the organic light emitting device 10 is obtained.

<Features of uneven structure>
FIG. 3 is an enlarged view of the microlens sheet 15 portion of FIG. The base of the convex portion 15a, that is, the boundary between the convex portion 15a and the flat portion 15b is circular, and its length (here, the diameter) is d1. Moreover, the height of the convex part 15a is set to h1. At this time, the aspect ratio a of the height h1 of the convex portion with respect to the diameter d1 of the base portion can be expressed by h1 / d1. For example, when a = 0.5, the convex portion 15a becomes a hemisphere.

  4 is a sectional view of an uneven structure of an elliptical hemisphere with a <0.5, FIG. 5 is a sectional view of an uneven structure of an elliptical hemisphere with a = 0.5, and FIG. 6 is an uneven structure of an elliptical hemisphere with a> 0.5. It is sectional drawing.

  As shown in FIG. 4, when a <0.5, the light that has been totally reflected once by the convex portion (arrow in FIG. 4) is totally reflected by the convex portion after the second time and returns to the transparent substrate side. . Further, as shown in FIG. 5, even when a = 0.5, the light totally reflected once by the convex portion (arrow in FIG. 5) is totally reflected by the convex portion after the second time and returns to the transparent substrate side. become. On the other hand, as shown in FIG. 6, when a> 0.5, the light that has been totally reflected once by the convex portion (the arrow in FIG. 6) goes from the convex portion to the air side after the second time (second time in FIG. 6). May be emitted.

  FIG. 7 is a graph showing the relationship of the single-surface transmittance A with respect to the aspect ratio a. Here, the single-surface transmittance is a ratio at which light once incident on the convex portion is emitted without returning to the transparent substrate side. In FIG. 7, the number of times of reflection at the convex portion is shown as 1, 2, 3, 4, and 1000 times.

  From FIG. 7, when a ≦ 0.5, it can be said that the single-surface transmittance is substantially the same regardless of the number of reflections at the convex portion. And in the case of a> 0.5, the ratio of the light reflected and emitted by the convex part twice or more increases, so that the overall transmittance is improved as compared with the case of a ≦ 0.5. Improvement of the transmittance directly leads to improvement of light extraction efficiency.

  In addition, since the light reflected multiple times by the convex portion is extracted to the air side, the polarization direction deviates from the light distribution in the transparent substrate, so that the emission direction becomes random and the color shift described later is mitigated. There is also.

  From the results so far, in order to improve the light extraction efficiency and reduce the color shift, in the organic light emitting device 10 of FIG. 1, the shape of the convex portion 15 a should be an elliptical hemisphere with a> 0.5. It can be said that it is preferable.

  Next, color misregistration will be examined. When the light distribution is different at light wavelengths, particularly red, green, and blue wavelengths, this corresponds to a shift between the color seen from the front (0 degree direction) and the color seen from the oblique direction. In particular, when it is desired to extract white light with an illumination light source or the like, it is important that this color shift is small.

  The color misregistration here is chromaticity determined from the wavelength distribution at each angle when light is viewed in 5 degree increments, such as in the front (0 degree) direction, 5 degrees, 10 degrees,... 80 degrees. And chromaticity is expressed by color coordinates. When the color coordinates in the front direction are set as the reference color coordinates, the coordinate deviation amount from the 0 degree color coordinates of the color coordinates at each angle, such as 5 degrees, 10 degrees,. Color misregistration. Further, the maximum value of 16 color shifts from 5 to 80 degrees is defined as the final color shift. The smaller the color shift value, the smaller the color shift.

FIG. 8 is a view showing a light distribution in the transparent substrate 14 when the microlens sheet 15 is omitted from the organic light emitting element 10, and FIG. 9 is an air view when the microlens sheet 15 is omitted from the organic light emitting element 10. It is a figure which shows light distribution (distribution of the light radiate | emitted to the air side). The solid line is the blue light distribution, the long broken line is the green light, and the short broken line is the red light distribution, which is normalized in the front direction. Here, the transparent substrate 14 whose air light distribution is smaller than 1 / n ² is used.

As shown in FIG. 8, in the transparent substrate 14, it can be seen that there is a clear color shift when viewed obliquely. When the light distribution in the transparent substrate 14 is an ideal circular Lambert light distribution, it is known that the air light distribution of the transparent substrate 14 is 1 / n ² when the refractive index of the transparent substrate 14 is n. ing. For example, when n = 1.5, light having a total reflection angle within about 41 degrees is emitted to the air side. In FIG. 8, the energy of the portion within about 41 degrees that is emitted to the air side without being totally reflected is smaller than that in the case of Lambert light distribution. This is due to the use of the transparent substrate 14 having an air light distribution smaller than 1 / n ² .

  Further, the light distribution shown in FIG. 9 has a shape in which the distribution near the center of the light distribution shown in FIG. 8 is extended to the entire angle as it is. FIG. 9 also shows that color misregistration has occurred. Assuming that the light incident on the transparent substrate 14 is 100%, the light extraction efficiency in FIG. 9 is 22% and the color shift is 0.074.

  Next, the relationship among the aspect ratio a of the convex portion 15a, the light extraction efficiency, and the color shift in the organic light emitting element 10 will be examined.

  FIG. 10 is a graph showing the light extraction efficiency when the aspect ratio a of the convex portion 15a is changed, and FIG. 11 is a graph showing the color shift when the aspect ratio a of the convex portion 15a is changed.

  As shown in FIG. 10, it can be said that the light extraction efficiency is good when a ≧ 0.25. On the other hand, as shown in FIG. 11, it can be seen that the color shift decreases as a increases as a ≧ 0.5. The color misregistration at a ≧ 1.0 is less than 0.04, at which it can be said that the color misregistration is small.

  Therefore, when a ≧ 1.0, it can be said that the light extraction efficiency is sufficiently high and the color shift is small.

  Further, in the light distribution in the transparent substrate 14, when there is a large amount of light in an oblique direction that is greater than or equal to total reflection as shown in FIG. May be improved and color misregistration may be reduced. In FIG. 11, the color shift is locally small (0.04 or less) in the region of 0.25 ≦ a ≦ 0.3.

  Therefore, when combined with the above result that light extraction efficiency is good when a ≧ 0.25, it can be said that when 0.25 ≦ a ≦ 0.3, the light extraction efficiency is sufficiently high and the color shift is small.

  Next, an organic light emitting device in which the uneven structure of the microlens sheet is composed of an elliptical hemispherical concave portion and a flat portion will be described. Except for the concavo-convex structure, the organic light-emitting element 10 has the same configuration. FIG. 12 is a sectional view of an uneven structure having an elliptical hemispherical recess, and FIG. 13 is a plan view thereof. The concavo-convex structure of the microlens sheet is formed by an elliptical hemispherical recess 20a and a planar portion 20b of a gap between the recesses 20a. In other words, the concavo-convex structure of the microlens sheet is formed by the flat surface portion 20b and the concave portion 20a recessed from the flat surface portion 20b.

  The opening of the recess 20a, that is, the boundary between the recess 20a and the flat surface 20b is circular, and its length (here, the diameter) is d2. The depth of the recess 20a is assumed to be h2. At this time, the aspect ratio a of the depth h2 of the recess 20a with respect to the diameter d2 of the opening can be expressed by h2 / d2. For example, when a = 0.5, the recess 20a becomes a hemisphere.

  The relationship between the aspect ratio a of the recess 20a, the light extraction efficiency, and the color shift in this organic light emitting device will be examined.

  FIG. 14 is a graph showing the light extraction efficiency when the aspect ratio a of the recess 20a is changed, and FIG. 15 is a graph showing the color shift when the aspect ratio a of the recess 20a is changed.

  As shown in FIG. 14, it can be said that the light extraction efficiency is good when a ≧ 0.25. On the other hand, as shown in FIG. 15, it can be seen that the color shift decreases as a increases as a ≧ 0.5. The color misregistration at a ≧ 0.75 is less than 0.04, at which it can be said that the color misregistration is small.

  Therefore, when the concavo-convex structure having the recess 20a is employed, it can be said that the light extraction efficiency is sufficiently high and the color shift is small when a ≧ 0.75.

  Further, even if the region of 0.25 ≦ a ≦ 0.3 is viewed, the color shift is small (0.04 or less), although not locally. Therefore, when combined with the above result that light extraction efficiency is good when a ≧ 0.25, it can be said that when 0.25 ≦ a ≦ 0.3, the light extraction efficiency is sufficiently high and the color shift is small.

  In the above description, the concavo-convex structure having the elliptical hemispherical convex portion 15a or the concave portion 20a has been described. The same tendency is shown in the quadrangular pyramid recess. That is, the light extraction efficiency is sufficiently high and the color misregistration is small in the convex portions of each shape when a ≧ 1.0 and when 0.25 ≦ a ≦ 0.3. On the other hand, the light extraction efficiency is sufficiently high and the color misregistration is small in the concave portions of each shape when a ≧ 0.75 and when 0.25 ≦ a ≦ 0.3.

  FIG. 16 is a cross-sectional view of a concavo-convex structure having convex portions of regular quadrangular pyramids, and FIG. 17 is a plan view thereof. The concavo-convex structure of the microlens sheet is formed by a convex portion 21a having a regular quadrangular pyramid and a planar portion 21b in a gap between the convex portions 21a. In other words, the concavo-convex structure of the microlens sheet is formed by the flat portion 21b and the convex portion 21a protruding from the flat portion 21b.

  The base of the convex part 21a, that is, the boundary between the convex part 21a and the flat part 21b is a square, and its length (here, the length of one side) is d3. Moreover, the height of the convex part 21a is set to h3. At this time, the aspect ratio a of the height h3 of the convex portion 21a with respect to the length d3 of one side of the base portion can be expressed by h3 / d3.

  18 is a cross-sectional view of a concavo-convex structure having a concave portion of a regular quadrangular pyramid, and FIG. 19 is a plan view thereof. The concavo-convex structure of the microlens sheet is formed by a concave portion 22a of a regular quadrangular pyramid and a flat portion 22b of a gap between the concave portions 22a. In other words, the concavo-convex structure of the microlens sheet is formed by the flat portion 22b and the concave portion 22a recessed from the flat portion 22b.

  The opening of the recess 22a, that is, the boundary between the recess 22a and the flat portion 22b is a regular quadrangular pyramid, and its length (here, the length of one side) is d4. The depth of the recess 22a is h4. At this time, the aspect ratio a of the depth h4 of the recess 22a with respect to the length d4 of one side of the opening can be expressed by h4 / d4.

  Next, the area of the planar portion will be examined by taking the concavo-convex structure of the concave portion 22a of a regular square pyramid as an example. In order to increase the light extraction efficiency and reduce the color misregistration, it is preferable that the area of the planar portion 22b is as small as possible. However, when forming the concavo-convex structure by transfer or the like, a certain area of the flat portion 22b is required for processing.

  Here, the sum of the areas of the respective concave portions 22a of the microlens sheet projected in the direction perpendicular to the plane portion 22b (Z direction) is S1, and the sum of the areas of the plane portions 22b of the microlens sheet is S2. At this time, the area ratio of the planar portion 22b of the concavo-convex structure is the ratio of the area S2 of the planar portion 22b to the area (S1 + S2) obtained by projecting the light extraction surface of the microlens sheet in the direction (Z direction) perpendicular to the planar portion 22b. , S2 / (S1 + S2).

  FIG. 20 is a graph showing the light extraction efficiency with respect to the aspect ratio a for various area ratios of the planar portion in a concavo-convex structure having a regular quadrangular pyramid recess. FIG. 21 is a graph showing the color shift with respect to the aspect ratio a in the concavo-convex structure having a concave portion of a regular quadrangular pyramid for various area ratios of the plane portion. 20 and 21 show the case where the area ratio of the plane portion is 0%, 25%, 50%, and 90%.

  As shown in FIG. 20, the light extraction efficiency is the best when the area ratio of the flat portion is 0%, the efficiency is somewhat lowered at 25%, and the efficiency is so low that it cannot be ignored at 50 and 90%. On the other hand, as shown in FIG. 21, it can be seen that the color shift is roughly reduced as a is increased when a ≧ 0.25. In particular, it is less than 0.04, which can be said that there is little color shift when a ≧ 0.25, when the area ratio of the planar portion is 0% or 25%.

  Therefore, when a concavo-convex structure having a regular quadrangular pyramid recess is employed, the light extraction efficiency is sufficiently high and the color shift is small when the area ratio of the planar portion is 0 to 25% at a ≧ 0.25 You can say that.

  An evaluation result is shown in FIG. 22 as examples 1 to 10 and comparative examples 1 to 5 of an example of the organic light-emitting elements having the various uneven structures described above. The organic light emitting device of Comparative Example 1 is obtained by omitting the microlens sheet 15 from the organic light emitting device 10. The organic light-emitting device of Example 1 is an organic light-emitting device 10 having a concavo-convex structure formed so as to contact the convex portion of an elliptical hemisphere with a = 1. The organic light-emitting device of Example 2 has a concavo-convex structure formed so as to contact a concave portion of an elliptical hemisphere with a = 0.75. The organic light-emitting device of Example 3 has a concavo-convex structure formed so as to contact a conical convex portion with a = 1. The organic light emitting device of Example 4 has a concavo-convex structure formed so as to contact a conical concave portion of a = 0.75. The organic light emitting device of Example 5 has a concavo-convex structure formed so as to be in contact with the convex portions of a = 1 regular tetragonal pyramid. The organic light emitting device of Example 6 has a concavo-convex structure formed so as to contact a concave portion of a regular quadrangular pyramid of a = 0.75.

  The organic light emitting device of Example 7 has a concavo-convex structure formed so as to contact the convex portion of an elliptical hemisphere with a = 0.25. The organic light-emitting device of Example 8 has a concavo-convex structure formed so as to contact the convex portion of an elliptical hemisphere with a = 0.3. The organic light emitting device of Comparative Example 3 has a concavo-convex structure formed so as to contact the convex portion of an elliptical hemisphere with a = 0.5.

  The organic light emitting device of Example 9 has a concavo-convex structure formed so as to contact a concave portion of a regular quadrangular pyramid of a = 0.8. The organic light emitting device of Example 10 has a concavo-convex structure composed of a quadrangular pyramid concave portion with a = 0.8 and a flat portion of 25%. The organic light-emitting device of Comparative Example 4 has a concavo-convex structure composed of a regular quadrangular pyramid concave portion with a = 0.8 and a flat portion with 50%. The organic light-emitting device of Comparative Example 5 has a concavo-convex structure composed of a regular quadrangular pyramid concave portion of a = 0.8 and a 90% flat portion.

  In FIG. 22, the light extraction efficiency is the ratio of light extracted to the air side when the light incident on the transparent substrate is 100%. Further, the magnification is a magnification of each light extraction efficiency with respect to the light extraction efficiency of Comparative Example 1. In addition, those with good light extraction efficiency are indicated with a mark ◯, those with a defect are indicated with a mark X, those with a good color shift are indicated with a mark ◯, those with a poor color are indicated with a mark X, and light extraction is performed as a comprehensive evaluation. Those with good efficiency and color misregistration are indicated by ○, and those with poor light extraction efficiency and / or color misregistration are indicated by x.

  As a result, Examples 1-10 have better light extraction efficiency and color shift than Comparative Example 1, Comparative Example 2 has poor light extraction efficiency and color shift, and Comparative Example 3 has poor color shift. Comparative Example 4 has poor color shift, and Comparative Example 5 has poor light extraction efficiency and color shift. Therefore, if it is an organic light emitting element of Examples 1-10, light extraction efficiency will be high enough and there will be little color shift.

  The light emitting element of the present invention can be used as a display device, a display, and various light sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, it is not limited to these. In particular, it can be effectively used as a backlight of a liquid crystal display device and a light source for illumination.

10 Organic light emitting devices (light emitting devices)
14 Transparent substrate 15a Convex part 15b, 20b Plane part 20a Concave part d1 Base length d2 Opening length h1 Convex part height h2 Concave part depth

Claims (8)

In a light emitting device having a light extraction surface with a concavo-convex structure on a transparent substrate,
The concavo-convex structure is formed of a flat part and a concave part recessed from the flat part or a convex part protruding from the flat part,
The ratio of the area of the plane part to the area of the light extraction surface projected in the direction perpendicular to the plane part is 0 to 25%,
The aspect ratio of the depth of the concave portion to the length of the opening of the concave portion or the aspect ratio of the height of the convex portion to the length of the base portion of the convex portion is 0.25 to 0.3,
The light emitting device, wherein an air light distribution of the transparent substrate is smaller than 1 / n ² where n is a refractive index of the transparent substrate.   The light emitting device according to claim 1, wherein the shape of the concave portion or the convex portion is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid. In a light emitting device having a light extraction surface with a concavo-convex structure on a transparent substrate,
The concavo-convex structure is formed of a flat portion and a concave portion recessed from the flat portion,
The ratio of the area of the plane part to the area of the light extraction surface projected in the direction perpendicular to the plane part is 0 to 25%,
The aspect ratio of the depth of the recess to the length of the opening of the recess is 0.75 or more,
The light emitting device, wherein an air light distribution of the transparent substrate is smaller than 1 / n ² where n is a refractive index of the transparent substrate.   4. The light emitting device according to claim 3, wherein the shape of the recess is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid. In a light emitting device having a light extraction surface with a concavo-convex structure on a transparent substrate,
The concavo-convex structure is formed of a flat portion and a convex portion protruding from the flat portion,
The ratio of the area of the plane part to the area of the light extraction surface projected in the direction perpendicular to the plane part is 0 to 25%,
The aspect ratio of the height of the convex portion to the length of the base portion of the convex portion is 1.0 or more,
The light emitting device, wherein an air light distribution of the transparent substrate is smaller than 1 / n ² where n is a refractive index of the transparent substrate.   6. The light emitting device according to claim 5, wherein the shape of the convex portion is an elliptical hemisphere, a cone, a truncated cone, a quadrangular pyramid, or a quadrangular pyramid.   The light-emitting element according to claim 1, wherein the uneven structure and the transparent substrate have the same refractive index.   The light emitting device according to claim 1, wherein the concavo-convex structure and the transparent substrate have a refractive index close to each other.

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