JP2012142142A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device with high light extraction efficiency, high brightness in a front direction, and reduced color unevenness.SOLUTION: A surface light source device comprises an organic EL element including a light emitting layer, and has a device light emitting surface for emitting light from the organic EL element. The surface light source device further comprises a light emission efficiency improving part positioned nearer the device light emission surface than the organic EL element. The light emission efficiency improving part comprises a first structure layer, and a second structure layer contacting the first structure layer and positioned nearer the device light emission surface than the first layer structure. The first structure layer is a layer made of a material of a refraction factor n1 having a first uneven structure having an inclined plane whose inclined angle θ1 is 60-80°, on the surface of the device light emission surface side. The second structure layer is a layer made of a material of a refraction factor n2 having a second uneven structure having an inclined plane whose inclined angle θ2 is 40-50°, on the surface of the device light emission surface side. n1 and n2 satisfy a relationship of n2-n1≤-0.12.

Description

  The present invention relates to a surface light source device. Specifically, the present invention relates to a surface light source device including an organic electroluminescence element (hereinafter, appropriately referred to as “organic EL element”).

  A surface light source light emitting device including an organic EL element can have a shape as a license, and the color of the light can be white or a color close thereto. For this reason, it can be considered that a surface light source device including an organic EL element is used as a light source of a lighting fixture that illuminates a space such as a living environment or as a backlight of a display device.

  As an example of an organic EL element used for a lighting fixture, a white organic EL element is produced. Many of such white elements are laminated layers or light-emitting layers that generate a luminescent color having a complementary color relationship, which are referred to as a laminated type or a tandem type. These light emitting layer laminates are mainly yellow / blue or green / blue / red laminates.

  However, currently known organic EL elements have low efficiency for use in the above applications. Therefore, when the organic EL element is used as a surface light source, it is required to increase its light extraction efficiency. For example, although the light emitting layer itself of the organic EL element has high luminous efficiency, the light amount is reduced due to interference or the like in the layer before it emits light through the laminated structure constituting the element. Such light loss is required to be reduced as much as possible.

  As a method for improving the light extraction efficiency of the organic EL element, it is known to provide various structures on the light extraction substrate. For example, a microlens array is provided on both surfaces of a light extraction substrate (Patent Document 1), a light transmission diffusion layer is laminated on the surface of a light-transmitting base sheet on the light output surface of a light source device, Providing a lens sheet having a lens arrangement layer on the surface of the transmission diffusion layer (Patent Document 2) has been proposed. With these structures, good light collection can be achieved and efficiency is improved.

International Publication WO2005 / 112514 Japanese Patent Laid-Open No. 8-335044

  However, when an organic EL element is used as a surface light source device, improvement of other characteristics is also required in addition to improvement of light extraction efficiency. For example, improvement in luminance in the front direction (normal direction of the light exit surface) and reduction in color change (hereinafter sometimes simply referred to as “color unevenness”) depending on the observation angle are also required. The change in color depending on the observation direction, that is, color unevenness, is observed when the light exit surface of the surface light source device is observed from the front direction and when observed from an oblique direction that is non-parallel to the front direction. The light spectrum is different, and the reduction in color unevenness is to reduce the difference in the light spectrum. A surface light source device having such color unevenness is not suitable as a light source in many applications.

  With the structures described in Patent Documents 1 and 2, it is possible to improve the light extraction efficiency, but it is not possible to improve the brightness in the front direction and reduce the color unevenness, and in particular, improve the brightness in the front direction and reduce the color unevenness. I can't be satisfied at the same time.

  An object of the present invention is to provide a surface light source device having high light extraction efficiency, high luminance in the front direction, and reduced color unevenness.

As a result of intensive studies to solve the above-described problems, the present invention has found that the object of the present invention can be achieved by providing two layers of uneven structures having different shapes and refractive indexes on the light-emitting surface of the light source device. . That is, according to the present invention, the following is provided.
[1] A surface light source device including an organic electroluminescence element including a light emitting layer, and having a device light emitting surface that emits light from the organic electroluminescence element,
The surface light source device further includes a light output efficiency improving unit positioned on the device light output surface side from the organic electroluminescence element,
The light emission efficiency improving unit includes a first structure layer, and a second structure layer that is in contact with the first structure layer and located closer to the device light-emitting surface side than the first structure layer,
The first structural layer is a layer made of a material having a refractive index n1, having a first concavo-convex structure having an inclined surface with an inclination angle θ1 of 60 to 80 ° on the surface of the device light-emitting surface.
The second structural layer is a layer made of a material having a refractive index n2 having a second concavo-convex structure having an inclined surface with an inclination angle θ2 of 40 to 50 ° on a surface on the device light-emitting surface side,
n1 and n2 are represented by the following formula (1):
n2-n1 ≦ −0.12 (1)
A surface light source device that satisfies the above relationship.
[2] The first uneven structure and the second uneven structure are:
It is a concavo-convex structure constituted by concavo-convex structure units arranged repeatedly in two or more directions parallel to the device light exit surface, or a concavo-convex structure unit extending in one direction parallel to the device light exit surface, A concavo-convex structure configured by being repeatedly arranged in a direction perpendicular to the one direction and parallel to the device light exit surface;
[1] The surface light source device according to [1].
[3] The surface light source according to [2], wherein the concavo-convex structure unit has a pyramid shape, a truncated pyramid shape, a prism shape extending in a direction parallel to the device light exit surface, or a combination thereof. apparatus.
[4] The surface according to any one of [1] to [3], wherein the light output efficiency improvement unit further includes a base film layer at a position farther from the device light output surface than the first structure layer. Light source device.
[5] The surface light source device according to any one of [1] to [4], wherein the light output efficiency improvement unit further includes an adhesive layer at a position farther from the device light output surface than the first structure layer. .
[6] The surface light source device according to any one of [1] to [5], wherein the light output efficiency improving unit further includes a substrate at a position farther from the device light output surface than the first structural layer.
[7] The light emission efficiency improving unit is
In a position farther from the device light exit surface than the base film layer, further having an adhesive layer,
The surface light source device according to [4], further including a substrate at a position farther from the device light-emitting surface than the adhesive layer.
[8] The surface light source device according to any one of [1] to [7], wherein at least one of the layers constituting the light emission efficiency improving unit is a layer having light diffusibility.
[9] The surface light source device according to [8], wherein the layer having light diffusibility is made of a material including particles that impart light diffusibility.

  The surface light source device of the present invention can be used as a surface light source device having high light extraction efficiency, high luminance in the front direction, and reduced color unevenness. Therefore, the surface light source device can be suitably used as a light source device such as a lighting fixture and a backlight device. Can do.

FIG. 1 is a perspective view schematically showing an example of the surface light source device of the present invention. 2 is a cross-sectional view showing a cross section of the surface light source device shown in FIG. 1 cut along a plane passing through the line 1a. FIG. 3 is a perspective view schematically showing the first structural layer 111 in the light emission efficiency improving unit 100 shown in FIGS. 1 and 2. FIG. 4 is a perspective view schematically showing another example of the surface light source device of the present invention. FIG. 5 is a cross-sectional view showing a cross section of the surface light source device shown in FIG. 4 cut along a plane passing through the line 2a. FIG. 6 is a perspective view schematically showing the first structural layer 211 in the light emission efficiency improving unit 200 shown in FIGS. 4 and 5. FIG. 7 is a perspective view schematically showing an example of a conventional surface light source device in a comparative example of the present application. FIG. 8 is a graph showing the results of Example 1 and Comparative Example 3 of the present application. FIG. 9 is a graph showing the results of Example 1 and Comparative Example 3 of the present application. FIG. 10 is a graph showing the results of Example 2 and Comparative Example 4 of the present application. FIG. 11 is a graph showing the results of Example 2 and Comparative Example 4. FIG. 12 is a graph showing the orientation distribution of the light emitting layers used in the examples and comparative examples of the present application.

〔Overview〕
The surface light source device of the present invention is a surface light source device that includes an organic EL element including a light emitting layer and has a device light exit surface that emits light from the organic EL element.
The surface light source device of the present invention further includes a light output efficiency improving unit positioned on the device light output surface side of the organic EL element. The light emission efficiency improving unit includes a first structure layer and a second structure layer that is in contact with the first structure layer and located closer to the device light-emitting surface side than the first structure layer.

In the present invention, the device light exit surface is a light exit surface as a surface light source device, that is, a light exit surface when light exits from the surface light source device to the outside of the device.
The device light exit surface is a surface parallel to the light emitting layer of the organic EL element, and is parallel to the main surface of the surface light source device. However, when the device light exit surface is defined by a surface having a fine concavo-convex structure, the area of the actual light exit surface is sufficiently larger than that of the concavo-convex structure. Can be recognized as a flat surface. In the present application, unless otherwise specified, it is simply “parallel (or perpendicular) to the device light-emitting surface” to be parallel (or perpendicular) to the device light-emitting surface viewed ignoring the microscopic uneven structure. That's it. In the present application, unless otherwise specified, the surface light source device will be described in a state where the device light-emitting surface is placed so as to be parallel to the horizontal direction and upward. Therefore, in the following description, the “upper” surface of a layer constituting the surface light source device is the surface of the layer closer to the device light exit surface, and the “lower” surface is the surface of the layer. This is the surface far from the device exit surface.
In the present invention, the fact that each component is “parallel” or “vertical” may include an error within a range that does not impair the effects of the present invention, for example, an error of ± 5 ° from a parallel or vertical angle. May be included.

[First Embodiment]
FIG. 1 is a perspective view schematically showing an example of the surface light source device of the present invention, and FIG. 2 is a cross-sectional view showing a cross section of the surface light source device shown in FIG. 1 cut along a plane passing through a line 1a. .
A surface light source device 10 shown in FIGS. 1 and 2 is a device having a rectangular plate-like structure, and is provided under an organic EL element substrate 131 that is a substrate that supports organic EL elements, and an organic EL element substrate 131. A transparent electrode layer 141 provided in contact with the side surface 13L; a light emitting layer 142 provided in contact with the transparent electrode layer 141; and a reflective electrode layer 143 provided in contact with the light emitting layer 142. The transparent electrode layer 141, the light emitting layer 142, and the reflective electrode layer 143 constitute the organic EL element 140. The surface light source device 10 further includes a sealing substrate 151 on the lower surface 14 </ b> L side of the organic EL element 140.

  The surface light source device 10 further includes a first structural layer 111 provided in contact with the upper surface 13U of the organic EL element substrate 131 and a first structural layer 111 provided in contact with the upper surface 11U of the first structural layer 111. 2 structural layers 121. The organic EL element substrate 131, the first structural layer 111, and the second structural layer 121 constitute the light emission efficiency improving unit 100.

  The light from the light emitting layer 142 passes through the transparent electrode layer 141 or is reflected by the reflective electrode layer 143, passes through the light emitting layer 142 and the transparent electrode layer 141, and travels toward the device light exit surface side. Most of the light emitted from the organic EL element 140 is transmitted through the organic EL element substrate 131, the first structural layer 111, and the second structural layer 121 in this order, and the upper surface of the second structural layer 121. I come out of light. Therefore, in this example, the upper surface of the second structural layer 121 is the device light exit surface.

[Uneven structure]
In the present invention, the first structural layer has a first concavo-convex structure having an inclined surface with a predetermined inclination angle θ1 on the surface on the device light-emitting surface side. On the other hand, the second structure layer has a second concavo-convex structure having an inclined surface with a predetermined inclination angle θ2 on the surface on the device light-emitting surface side. The concavo-convex structure on the first structural layer and the second structural layer can be constituted by, for example, a concavo-convex structure unit that is repeatedly arranged in two directions parallel to the device light exit surface.

  This will be described with reference to the example of FIGS. 1 and 2. In the light emission efficiency improving unit 100, the upper surface of the first structural layer 111 (that is, the device light emission surface side) has an uneven structure. FIG. 3 is a perspective view schematically showing the first structural layer 111 in the light emission efficiency improving unit 100 shown in FIGS. 1 and 2. As shown in FIG. 3, the upper surface of the first structural layer 111 has a depression having a regular quadrangular pyramid shape (that is, a quadrangular pyramid shape having a square base and the same shape of four inclined surfaces). A plurality of concavo-convex structure units 112 having a number of are repeatedly arranged in two directions, ie, a long side and a short side direction of the apparatus, thereby defining a first concavo-convex structure.

  On the other hand, as shown in FIG. 1 and FIG. 2, the concavo-convex structure unit 122 having depressions in the shape of a regular quadrangular pyramid is also formed on the upper surface of the second structural layer 121 in the long side and short side directions of the device. Many are arranged repeatedly in the direction, and these define the second concavo-convex structure.

  In the present invention, the inclination angle θ1 of the inclined surface of the first concavo-convex structure is 60 to 80 °, preferably 65 to 75. On the other hand, the inclination angle θ2 of the inclined surface of the second concavo-convex structure is 40 to 50 °, preferably 42 to 48. Here, the inclination angle of the inclined surface is an angle formed by the inclined surface and the device light exit surface.

When the first concavo-convex structure and the second concavo-convex structure are formed of a large number of inclined surfaces having a uniform inclination angle, the angles formed by the inclined surface and the device light-emitting surface are the inclination angles θ1 and θ2, respectively.
For example, as in the example shown in FIGS. 1 to 3, when the concavo-convex structure is formed by repeating a large number of concavo-convex structure units of regular quadrangular pyramids, the angle formed by the slopes of the regular quadrangular pyramids and the device light exit surface is the concavo-convex structure. This corresponds to an inclination angle of. That is, in the example of FIGS. 1 and 2, the line 1 c is a line parallel to the device light exit surface and a line in contact with the apex 12 </ b> P of one row of the concavo-convex structure unit 122 of the regular quadrangular pyramid. Therefore, in the example of FIG. 2, the angle formed between the inclined surface 12S and the line 1a is equal to the angle formed between the inclined surface 12S and the device light exit surface, and thus corresponds to the inclination angle θ2 of the inclined surface of the second concavo-convex structure. To do. Similarly, the angle formed between the inclined surface 11S and the line 1b passing through the apex 11P of the concavo-convex structure unit 112 parallel to the device light-emitting surface is equal to the angle formed between the inclined surface 11S and the device light-emitting surface. It becomes the inclination angle θ1 of the inclined surface of the structure.

  The height of the concavo-convex structure in the concavo-convex structure is not particularly limited, but the centerline average roughness measured on the surface on which the concavo-convex structure is formed in various directions (various directions in a plane parallel to the device light exit surface). The maximum value (Ra (max)) can be in the range of 1 to 50 μm. When the concavo-convex structure is formed on the structural layer, a preferable concavo-convex height can be determined relative to the thickness of the structural layer. For example, when a hard material that is advantageous for maintaining the durability of the concavo-convex structure is used as the material of the structural layer, the thickness of the structural layer is reduced, so that the flexibility of the multilayer body increases, and the surface light source device is manufactured. Handling of the multilayer body in the process becomes easy. Specifically, the thickness of the structural layer with respect to the height of the unevenness is preferably 100% to 300%.

[Refractive index of structural layer]
In the present invention, the first structural layer is a layer made of a material having a refractive index n1, the second structural layer is a layer made of a material having a refractive index n2, and n1 and n2 are expressed by the following formula (1). :
n2-n1 ≦ −0.12 (1)
Meet. The upper limit of the value of n2-n1 is more preferably −0.14 or less. The lower limit of the value of n2-n1 is not particularly limited, but can be preferably -0.4 or more for reasons of selecting a high refractive index material.

The surface light source device of the present invention has a combination of the first structural layer and the second structural layer, and further has the predetermined tilt angle and refractive index described above, thereby reducing the high front luminance and reducing the luminance. It is possible to achieve both color unevenness.
In the prior art, it is known to provide a light emission efficiency improving portion having a single structural layer in order to improve the light extraction efficiency, and further, by adjusting the inclination angle of the concavo-convex structure on the light emission surface, the luminance is improved. It was also known that it can improve or reduce color unevenness. However, in such an aspect, when the luminance is improved, the color unevenness increases, and conversely, when the color unevenness is reduced, the luminance decreases (see Comparative Examples 1 and 2 of the present application). Here, according to the finding of the inventor of the present application, as defined in the present invention, when the two structural layers are combined and these have the predetermined inclination angle and refractive index described above, It is possible to achieve both high front luminance and reduced color unevenness.

  When the surface light source device of the present invention has the above-described configuration, the displacement of at least one of the x-coordinate and y-coordinate of the chromaticity coordinate in all hemispherical directions on the light-emitting surface of the device is not configured as described above. For example, the size can be reduced by half. For this reason, in the surface light source device, it is possible to suppress a change in color due to the observation angle. As a method for measuring the displacement of chromaticity in all hemispherical directions, for example, when a spectral radiance meter is installed on the normal line (front) of the device light-emitting surface and the normal direction is 0 °, the device light-emitting surface Since a chromaticity coordinate can be calculated from an emission spectrum measured in each direction by providing a mechanism that can rotate the angle from −90 to 90 °, the displacement can be calculated.

[Idemitsu efficiency improvement part Arbitrary layer]
In the surface light source device of the present invention, the light output efficiency improving unit may have an arbitrary layer in addition to the first structural layer and the second structural layer. For example, as in the example shown in FIGS. 1 to 3, a substrate for supporting the organic EL element may be provided at a position farther from the device light exit surface than the first structural layer. In addition, it can have one or more base film layers, an adhesive layer, or a combination thereof at a position farther from the device light exit surface than the first structural layer. When the substrate, the adhesive layer, and the base film layer are combined, the adhesive layer is located farther from the device light exit surface than the base film layer, and the substrate is located farther from the device light exit surface than the adhesive layer. Is preferred. That is, it is preferable to have a layer structure of (substrate)-(adhesive layer)-(base film layer)-(first structure layer)-(second structure layer). By having such a layer configuration, an operation of attaching a multilayer structure having a layer configuration of (adhesive layer)-(base film layer)-(first structural layer)-(second structural layer) to the substrate. Thus, the surface light source device can be manufactured, and a surface light source device having good optical performance can be easily manufactured.

[Materials for structural layer and base film layer]
As a material of each layer constituting the light output efficiency improving portion, a material that can be used for the optical member can be appropriately selected and used. In particular, the material of the first structural layer, the second structural layer, and the base film layer is a resin composition containing a transparent resin and, if necessary, other optional components. It is preferable from the viewpoint of easy acquisition of desired optical performance.

  That the transparent resin is “transparent” means that it has a light transmittance suitable for use in an optical member. In the present invention, the first structural layer, the second structural layer, and the base film layer can have a light transmittance suitable for use in an optical member, and each layer has a total transmittance of 80% or more. It can have light transmittance.

  The material of the transparent resin contained in the resin composition is not particularly limited, and various resins that can form a transparent layer can be used. Examples thereof include a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, and an electron beam curable resin. Among these, thermoplastic resins are preferable because they can be easily deformed by heat, and ultraviolet curable resins have high curability and high efficiency, so that an uneven structure layer can be formed efficiently. Examples of the thermoplastic resin include polyester-based, polyacrylate-based, and cycloolefin polymer-based resins. Examples of the ultraviolet curable resin include epoxy resins, acrylic resins, urethane resins, ene / thiol resins, and isocyanate resins. As these resins, those having a plurality of polymerizable functional groups can be preferably used.

  The material for the first and second structural layers is preferably a material having a high hardness at the time of curing, from the viewpoint of easily forming a concavo-convex structure and easily obtaining scratch resistance of the concavo-convex structure. Specifically, when a resin layer having a film thickness of 7 μm is formed on a substrate without a concavo-convex structure, a material having a pencil hardness of HB or higher is preferable, and a material of H or higher is more preferable. The material which becomes 2H or more is more preferable. On the other hand, as the material of the base film layer, a multilayer body (base film layer, first structure layer, and second layer) in forming the first and second structure layers and / or after forming the structure layer is used. In order to facilitate the handling of the material having a structural layer, a material having a certain degree of flexibility is preferable. By combining such materials, a multilayer body that is easy to handle and excellent in durability can be obtained, and as a result, a high-performance surface light source device can be easily manufactured. Such a combination of materials can be obtained by appropriately selecting the transparent resin exemplified above as the resin constituting each material. Specifically, an ultraviolet curable resin such as an acrylate is used as the transparent resin constituting the material of the first and second structural layers, while the alicyclic olefin is used as the transparent resin constituting the material of the base film layer. A polymer film or a polyester film can be used, whereby a preferable combination of materials can be obtained.

  When the light emission efficiency improvement part has a base film layer, the refractive index of the first structure layer and the base film layer can be made as close as possible. In this case, the difference in refractive index is preferably 0. It is within 20 and more preferably within 0.17.

  The resin composition that is the material of the layer that is a constituent element of the light output efficiency improving portion such as the first and second structural layers and the base film layer will be described later when the layer is a layer having light diffusibility. Elements that impart light diffusibility such as particles can be included. Furthermore, the resin composition can contain arbitrary components as needed. Examples of the optional component include additives such as phenol-based and amine-based deterioration preventing agents; surfactant-based, siloxane-based antistatic agents; triazole-based, 2-hydroxybenzophenone-based light-resistant agents; be able to.

  In the present invention, the thicknesses of the first and second structural layers are not particularly limited, but are preferably 1 to 70 μm. Here, the thickness of the first structural layer refers to the surface on the organic EL element side where the concavo-convex structure is not formed and the portion protruding to the most outgoing surface side of the concavo-convex structure (vertex 11P in the examples of FIGS. 1 to 3). ). The thickness of the second structural layer is the distance between the portion that protrudes most toward the first structure layer and the portion that protrudes most toward the light exit surface. Moreover, it is preferable that the thickness of a base film layer is 20-300 micrometers.

[Substrate material, physical properties and shape]
When the light emission efficiency improving part has a substrate that supports the organic EL element, a material such as glass can be adopted as the material of the substrate, thereby giving the surface light source device rigidity to suppress deflection. it can. Further, by providing a substrate that is excellent in the performance of sealing the organic EL element as a substrate and that can easily form the layers constituting the organic EL element in the manufacturing process in order, a surface light source The durability of the device can be improved and the manufacture can be facilitated.

  Examples of the material constituting the substrate include resins in addition to glass. Although the refractive index of a board | substrate is not restrict | limited in particular, It can be set to 1.4-2. In the present invention, the thickness of the substrate is not particularly limited, but is preferably 0.1 to 5 mm.

(Adhesive layer)
When the light emission efficiency improving part has an adhesive layer, the adhesive as the material is a narrowly defined adhesive (a so-called hot melt type having a shear storage elastic modulus at 23 ° C. of 1 to 500 MPa and exhibiting no tackiness at room temperature. As well as pressure-sensitive adhesives having a shear storage modulus at 23 ° C. of less than 1 MPa. In the present application, unless otherwise specified, the adhesive and the adhesive layer are such an adhesive in a broad sense and an adhesive layer formed thereby. As the material for the adhesive layer, specifically, a material having a refractive index close to that of the substrate or the transparent resin layer and transparent can be appropriately used. More specifically, an acrylic adhesive or a pressure-sensitive adhesive can be used. The thickness of the adhesive layer is preferably 5 to 100 μm.

(Light diffusion layer)
In the surface light source device of the present invention, one or more of the layers constituting the light emission efficiency improving portion can be a layer having light diffusibility (hereinafter, sometimes simply referred to as “light diffusion layer”). More specifically, a substrate, an adhesive layer, a base film layer, a first structural layer, a second structural layer, and other optional layers that are essential or optional layers constituting the light emission efficiency improving portion. A part or all of the layer may be a light diffusion layer.
By having such a light diffusion layer, effects such as reduction in color unevenness and improvement in light extraction efficiency can be obtained more favorably. In applications where the mirror surface of the reflective electrode is not observed from the light exit surface of the device when the device is not driven, the mirror surface is concealed and not driven by having the light diffusion layer. The appearance of the device light exit surface at the time can be a white appearance or other non-specular appearance.

  Examples of the material of the light diffusion layer include a material containing particles that impart light diffusibility, and a material that is an alloy resin that diffuses light by mixing two or more kinds of resins. From the viewpoint that the light diffusibility can be easily adjusted, a material containing particles imparting light diffusibility, particularly a resin composition containing particles imparting light diffusibility, is particularly preferred.

  The particles imparting light diffusibility may be transparent or opaque. As a material for such particles, metals, metal compounds, resins, and the like can be used. Examples of the metal compound include metal oxides and nitrides. Specific examples of metals and metal compounds include metals having high reflectivity such as silver and aluminum, and metal compounds such as silicon oxide, aluminum oxide, zirconium oxide, silicon nitride, tin-doped indium oxide, and titanium oxide. Can do. On the other hand, examples of the resin include methacrylic resin, polyurethane resin, and silicone resin.

The shape of the particles imparting light diffusibility can be a spherical shape, a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, a pyramid shape, a conical shape, a star shape, or the like.
In the light diffusing layer, the content ratio of the particles is preferably 1 to 80%, more preferably 5 to 50%, in the volume ratio in the total amount of the material constituting the layer. By setting the content ratio of the particles to the lower limit or higher, desired effects such as reduction in color unevenness can be obtained. Moreover, by setting it as this upper limit or less, aggregation of the particle | grains in a layer can be prevented and the layer in which the particle | grains were disperse | distributed favorably can be obtained easily.
The particle size of the particles is preferably 0.1 μm or more and 10 μm or less, more preferably 5 μm or less. Here, the particle diameter is a 50% particle diameter in an integrated distribution obtained by integrating the volume-based particle amount with the particle diameter as the horizontal axis. The larger the particle size, the larger the content ratio of particles necessary for obtaining the desired effect, and the smaller the particle size, the smaller the content. Therefore, as the particle diameter is smaller, desired effects such as reduction in color unevenness and improvement in light extraction efficiency can be obtained with fewer particles. When the particle shape is other than spherical, the diameter of the sphere having the same volume is used as the particle size.

  When the particles are transparent particles and the particles are contained in the transparent resin, the difference between the refractive index of the particles and the refractive index of the transparent resin is preferably 0.05 to 0.5. More preferably, it is 07-0.5. Here, either the particle or the refractive index of the transparent resin may be larger. If the refractive index of the particles and the transparent resin is too close, the diffusion effect cannot be obtained and the color unevenness is not suppressed. Conversely, if the difference is too large, the diffusion increases and the color unevenness is suppressed, but the light extraction effect is reduced. Become.

  When a layer constituting a part or all of the light emission efficiency improving part is a light diffusion layer, which of the layers constituting the light emission efficiency improving part is not particularly limited, various viewpoints You can choose from. For example, from the viewpoint that the degree of diffusion can be easily adjusted, it is preferable to use a layer containing a transparent resin as a light diffusion layer.

Furthermore, from the viewpoint of ensuring sufficient light diffusibility without increasing the content ratio of the particles in the layer, it is preferable to use a layer having a certain thickness, such as 5 μm or more, as the light diffusion layer.
Here, the first and second structural layers are preferably made of a material having a high hardness as described above. However, when the thickness of the material having such a high hardness is large, when used in a surface light source device, over time, Undesirable warping may occur on the light exit surface of the device. Therefore, from this viewpoint, it is preferable to use a layer other than the first and second structural layers and capable of imparting a property of being easily plastically deformed, for example, a base film layer or an adhesive layer as a light diffusion layer.

  On the other hand, management of a manufacturing process can be made easy by making the layer which does not accompany the process of heating materials, such as transparent resin, into a light-diffusion layer in a manufacturing process. For example, it is possible to easily cope with a case where clogging with particles occurs in the resin conveyance path. From this viewpoint, the adhesive layer is preferably a light diffusion layer. Alternatively, it is also preferable to use a layer other than the adhesive layer and the adhesive layer as a light diffusion layer. For example, the adhesive layer and the base film layer are used as a light diffusion layer, and by reducing the proportion of particles added to the base film layer, management in the manufacturing process of the base film layer is facilitated (for example, clogging is prevented). The frequency of occurrence can be reduced).

  Furthermore, in the light emission efficiency improvement part, layers other than the first and second structural layers, the base film layer, the adhesive layer, and the substrate can be additionally provided, and the additional layer can be used as a light diffusion layer. . For example, addition between the first structure layer and the base film layer, between the adhesive layer and the substrate, the surface on the light emitting layer side of the substrate (for example, between the electrode layer constituting the light emitting layer and the glass substrate) Can be formed. Alternatively, both the additional layer and the first and second structural layers, the base film layer, the adhesive layer, and one or more layers of the glass substrate may be used as a light diffusion layer.

  In the case where the light diffusion layer is provided as a layer constituting part or all of the light output efficiency improving portion, the degree of diffusion is not particularly limited, but as an example, the light diffusion layer is a part between the second structural layer and the adhesive layer. Alternatively, in the case of all, the total light transmittance of a portion from the second structural layer to the adhesive layer in a state where there is no surface irregularity of the first and second structural layers is 70 to 95%. Preferably, it is 75 to 90%. Moreover, although the refractive index of a light-diffusion layer is not specifically limited, 1.45-2 are preferable, 1.6-2 are more preferable, and 1.7-2 are more preferable. By selecting a large refractive index for such a light diffusing layer, a material having a smaller refractive index can be used as the refractive index of the light-emitting layer than the light diffusing layer, so that the selectivity of the material is widened. .

[Organic EL device]
The surface light source device of the present invention includes an organic EL element including a light emitting layer. The organic EL element can be an element including two or more electrode layers and one or more light emitting layers that are provided between these electrode layers and emit light when voltage is applied from the electrodes.

  The organic EL element has a structure in which layers such as an electrode and a light-emitting layer constituting the element are formed on a substrate, and a sealing member that covers these layers is further provided and sealed with the substrate and the sealing member. It is common. Usually, the element that emits light from the substrate side here is called a bottom emission type, and the element that emits light from the sealing member side is called a top emission type. Any of these may be sufficient as the surface light source device of this invention. In the case of the bottom emission type, a substrate for an organic EL element or a combination of such a substrate and an arbitrary layer (a layer existing between the substrate and the organic EL element) constitutes a part of the light emission efficiency improving unit. On the other hand, in the case of the top emission type, a structure on the device light exit surface side such as a sealing member constitutes a part of the light output efficiency improving portion.

In this invention, it does not specifically limit as a light emitting layer which comprises an organic EL element, A well-known thing can be selected suitably. The light-emitting material in the light-emitting layer is not limited to one type, and the light-emitting layer is not limited to one layer, and may be a single layer or a combination of a plurality of layers in order to suit the use as a light source. Thereby, light of white color (specifically, for example, a color temperature range of 3000 to 6500 K) or a color close thereto can be emitted.
In the present invention, in particular, the object is to reduce the change in color depending on the observation angle. Therefore, the light emitting layer preferably has two or more emission peaks or emits light in a wide wavelength range. Therefore, the light emitting layer is preferably one or more layers containing two or more kinds of light emitting materials. More specifically, the light emitting layer preferably emits white light.

  The organic EL device may further include other layers such as a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and a gas barrier layer in addition to the light emitting layer between the electrodes. In addition to the organic EL element, the surface light source device of the present invention can also include arbitrary components such as a wiring for energizing the electrode of the element and a peripheral structure for sealing the light emitting layer.

  The electrode of the organic EL element is not particularly limited, and a known one can be appropriately selected. Like the organic EL element 140 according to the first embodiment, an organic EL element that emits light to the light-emitting surface structure layer side by using the electrode on the light-emitting surface structure layer side as a transparent electrode and the electrode on the opposite side as a reflective electrode; can do. Further, both electrodes are transparent electrodes, and a reflection member or a scattering member (for example, a white scattering member disposed via an air layer) is provided on the side opposite to the device light-emitting surface, so that the device light-emitting surface side is provided. Idemitsu can also be achieved.

Although it does not specifically limit as a material which comprises an electrode and the layer provided among them, The following can be mentioned as a specific example.
ITO etc. can be mentioned as a material of a transparent electrode.
Examples of the material for the hole injection layer include a starburst aromatic diamine compound.
Examples of the material for the hole transport layer include triphenyldiamine derivatives.
Examples of the host material for the yellow light-emitting layer include triphenyldiamine derivatives, and examples of the dopant material for the yellow light-emitting layer include tetracene derivatives.
Examples of the material for the green light emitting layer include pyrazoline derivatives.
Examples of the host material for the blue light emitting layer include anthracene derivatives, and examples of the dopant material for the blue light emitting layer include perylene derivatives.
Examples of the material for the red light emitting layer include europium complexes.
Examples of the material for the electron transport layer include an aluminum quinoline complex (Alq).
Examples of the cathode material include lithium fluoride and aluminum, which are sequentially stacked by vacuum film formation.

  By appropriately combining the above or other light-emitting layers, a light-emitting layer that generates a light emission color having a complementary color relationship, which is referred to as a stacked type or a tandem type, can be obtained. Thereby, it can be set as the light emitting layer which light-emits the light of the color of white or it. The combination of complementary colors can be yellow / blue, green / blue / red, or the like.

〔Production method〕
Although the manufacturing method of the surface light source device of this invention is not specifically limited, For example, when manufacturing a surface light source device provided with the light emission efficiency improvement part which has a 1st and 2nd structure layer, a base film, an adhesive layer, and a board | substrate. Each layer constituting the organic EL element is laminated on one side of the substrate, and thereafter or before that, a multilayer body having the first and second structural layers and the base film on the other side of the substrate, It can manufacture by sticking through an adhesive layer.

  The manufacture of the multilayer body having the first and second structural layers is performed by preparing a mold such as a mold having a desired shape, and forming a material for forming the first structural layer and a second structural layer. Can be carried out by transferring to a layer of the material to be transferred.

As a more specific method for forming the first structural layer,
(Method 1) For example, an unprocessed multilayer body having a layer of the resin composition A constituting the base film and a layer of the resin composition B constituting the first structure layer (an uneven structure has not yet been formed) A method of forming a concavo-convex structure on the surface of the unprocessed multilayer body on the resin composition B side; and (Method 2) a resin composition B in a liquid state on a base film And applying a mold to the layer of the applied resin composition B, curing the resin composition B in that state, and forming a first structure layer having a concavo-convex structure.

In the method 1, the raw multilayer body can be obtained by, for example, extrusion molding in which the resin composition A and the resin composition B are coextruded. An uneven structure can be formed by pressing a mold having a desired surface shape onto the surface of the unprocessed multilayer body on the resin composition B side.
More specifically, a long raw multilayer body is continuously formed by extrusion molding, and the raw multilayer body is pressed with a transfer roll and a nip roll having a desired surface shape, thereby continuously. Manufacturing can be performed efficiently. The pinching pressure between the transfer roll and the nip roll is preferably several MPa to several tens of MPa. The temperature at the time of transfer is preferably Tg or more (Tg + 100 ° C.) or less, where Tg is the glass transition temperature of the resin composition B. The contact time between the unprocessed multilayer body and the transfer roll can be adjusted by the film feed speed, that is, the roll rotation speed, and is preferably 5 seconds or more and 600 seconds or less.

  In Method 2, it is preferable to use a composition that can be cured by energy rays such as ultraviolet rays as the resin composition B for forming the first structural layer. From the light source located on the back side of the coating surface (the side opposite to the surface on which the resin composition B is applied) of the coating surface in a state where the resin composition B is coated on the base film and the mold is applied. By irradiating energy rays such as ultraviolet rays, curing the resin composition B, and then peeling the mold, the coating film of the resin composition B can be used as a concavo-convex structure layer to obtain a multilayer body.

As a more specific method for forming the second structural layer,
(Method 3) The resin composition C in a liquid state is applied onto the first structural layer, and the mold is applied to the layer of the applied resin composition C in the same manner as in the method 2 described above. And a method of curing the resin composition C to form a second structure layer having a concavo-convex structure.

  As another method for forming the first structural layer and the second structural layer, the first structural layer and the second structural layer are directly formed on the substrate by the same method as the above-described method 2 and method 3. The method of forming can be mentioned. Thereby, the surface light source device of the aspect in which the 1st structure layer was directly formed on the board | substrate can be obtained. As still another method, the first structural layer and the second structural layer are formed on a flat surface by the same method as the above method 2 and method 3, and the first structural layer and the second structural layer are formed. The method of peeling and sticking this on a board | substrate directly or through an adhesive layer can be mentioned.

[Second Embodiment]
In the first embodiment exemplified above, the first and second concavo-convex structures are constituted by concavo-convex structure units that are repeatedly arranged in two directions parallel to the device light exit surface, and more specifically. Although it consists of the aligned square pyramid, the shape of the 1st and 2nd uneven structure is not restricted to this. As another embodiment, for example, in the concavo-convex structure, the concavo-convex structure units extending in one direction parallel to the device light exit surface are repeatedly arranged in a direction perpendicular to the one direction and parallel to the device light exit surface. It may be configured.

  In this case, the concavo-convex structural unit can have a prismatic shape extending in a direction parallel to the device light exit surface. By arranging a large number of such prismatic shapes, the concavo-convex structure can be formed into a row-like structure. Also in such an embodiment, the inclination angles θ1 and θ2 of the first and second concavo-convex structures and the refractive indexes n1 and n2 of the first and second structural layers are set within the predetermined range. The effects of the invention can be obtained.

  FIG. 4 is a perspective view schematically showing another example of the surface light source device of the present invention, and FIG. 5 is a cross-sectional view showing a cross section of the surface light source device shown in FIG. 4 cut along a plane passing through the line 2a. It is. FIG. 6 is a perspective view schematically showing the first structural layer 211 in the light emission efficiency improving unit 200 shown in FIGS. 4 and 5. The surface light source device 20 shown in FIGS. 4 and 5 includes the first structure layer 211 and the second structure layer 221 having the above-described row-like uneven structure as the first and second structure layers. In this respect, the second embodiment is different from the first embodiment, and other components are common.

  As shown in FIG. 6, an uneven structure unit 212 having a triangular prism shape and extending in the short side direction of the device is repeatedly formed in the long side direction of the device on the upper surface of the first structural layer 211. Many are arranged, and these define the first uneven structure. On the other hand, as shown in FIGS. 4 and 5, the upper and lower surfaces of the second structural layer 221 also have a concavo-convex structure unit 222 that has a triangular prism shape and extends in the short side direction of the device. A large number are repeatedly arranged in the side direction, and these define the second concavo-convex structure.

  In this example, the concavo-convex structure unit 212 has a symmetric shape with a vertical plane passing through the ridgeline 21P as a symmetric plane. Accordingly, the angles formed by the two inclined surfaces 21S of one concavo-convex structure unit 212 and the device light exit surface are equal. Therefore, in this example, since the first concavo-convex structure is composed of a large number of inclined surfaces having a uniform inclination angle, the angle formed by the inclined surface 21S and the device light exit surface is the inclination angle θ1 of the inclined surface of the first concavo-convex structure. It corresponds to. Similarly, in this example, the concavo-convex structure unit 222 of the second concavo-convex structure has a symmetric shape with a vertical plane passing through the ridgeline 22P as a symmetric plane. Therefore, the angle formed by the inclined surface 22S and the device light exit surface corresponds to the inclination angle θ2 of the inclined surface of the second concavo-convex structure.

[Other Embodiments]
The present invention is not limited to the above specific examples, and can be arbitrarily modified within the scope of the claims of the present application and equivalents thereof.
For example, in the first embodiment exemplified above, the first and second concavo-convex structures are constituted by concavo-convex structure units having a regular quadrangular pyramid shape, but the concavo-convex structure units are not limited to this, and a regular quadrangular pyramid is formed. In place of the shape, any other pyramid shape (for example, a triangular pyramid, a quadrangular pyramid other than a regular quadrangular pyramid, a hexagonal pyramid, etc.), a conical shape, a pyramid or a shape having a rounded tip, or a pyramid Or it can be set as the shape by which the front-end | tip of the cone was chamfered flat (pyramidal frustum or truncated cone), the shape of a part of spherical surface, or the shape which combined these. Further, in the first embodiment exemplified above, the concavo-convex structure units constituting the first and second concavo-convex structures are structures that are convex on the device light-emitting surface side, but the concavo-convex structure units are not limited thereto, A concave shape obtained by inverting the above various shapes may be used, or a combination of a convex structure and a concave structure may be used. Furthermore, the concavo-convex structure unit may be another polygonal column shape, a partial shape of a cylinder, or a combination thereof instead of the triangular column shape of the second embodiment. Further, the first concavo-convex structure and the second concavo-convex structure are provided such that one of the first concavo-convex structure and the second concavo-convex structure is provided with a pyramidal concavo-convex structure unit and the other is provided with a prismatic concavo-convex structure unit. It is also possible to adopt different types of concavo-convex structure units.

In the first embodiment and the second embodiment exemplified above, the direction in which the concavo-convex structure units are repeatedly arranged is the same direction in the first concavo-convex structure and the second concavo-convex structure, but this is a different direction. It can also be. For example, in the first embodiment, the direction in which the second concavo-convex structure is repeatedly arranged is changed so that the short side and the long side of the device are non-perpendicular and non-parallel, and the repetitive arrangement direction is different from the first concavo-convex structure. can do.
Moreover, in the illustration of the said embodiment, although the uneven | corrugated structure unit distributed over the whole surface of the surface of the 1st structure layer and the 2nd structure layer showed what only the thing which has the same shape is distributed. In the concavo-convex structure, concavo-convex structure units having different shapes may be mixed. For example, pyramid shapes having different sizes may be mixed, pyramid shapes and cone shapes may be mixed, or a combination of a plurality of pyramids and a simple pyramid shape may be mixed.

  When the angles of the inclined surfaces present in the first concavo-convex structure and the second concavo-convex structure are not uniform, for example, when there are a plurality of types of inclined surfaces, planes, curved surfaces, or combinations thereof, the average inclination angle of the entire surface Are the inclination angles θ1 and θ2. The average inclination angle is specified as follows. That is, when the concavo-convex structure surface is divided into n small areas sufficiently smaller than the concavo-convex structure unit and each small area is ΔSi, the value of the angle that the above-described ΔSi makes with the device light-emitting surface is θi, The average inclination angle is expressed by the following formula (2):

  Stipulated in Here, ΣΔSi represents the total surface area of the reflective layer.

  In the first embodiment and the second embodiment exemplified above, the second structural layer is the device light-emitting surface. However, the surface light source device of the present invention is not limited to this, and is further above the second structural layer. In addition, an arbitrary layer may be provided. For example, a third structural layer may be provided on the upper side of the second structural layer, and the third structural layer may be any of those exemplified as examples of the first and second uneven structures described above. A similar uneven structure may be provided on the device light exit surface side. Furthermore, you may have arbitrary layers on the light emission efficiency improvement part. The arbitrary layer may be, for example, a coating layer further provided on the concavo-convex structure on the upper surface of the light emission efficiency improving portion layer, and the upper surface of the coating layer is the device light output of the surface light source device of the present invention. The surface may be defined.

  In the first and second embodiments exemplified above, the first and second structural layers are provided on the upper side of the substrate for forming and supporting the organic EL element. However, the first structural layer may also serve as the substrate. In this case, the first structural layer can be obtained by processing the surface of a flat plate such as glass into a predetermined shape.

  In the first embodiment and the second embodiment illustrated above, the transparent electrode 141 is provided in direct contact with the substrate 131. However, between the substrate and the electrode, the adhesion strength is improved and the sealing performance is improved. For this purpose, an arbitrary layer such as a layer of an inorganic material can be provided.

  The surface light source device of the present invention may further include a layer of an arbitrary substance such as a filler or an adhesive between the organic EL element and the sealing substrate as an optional component. It may be. As long as there is no inconvenience such as greatly impairing the durability of the light emitting layer, air or other gas may be present in the space, or the space may be evacuated.

[Application of surface light source device]
The surface light source device of the present invention can be used as a light source device such as a lighting fixture and a backlight device.
The luminaire includes the surface light source device of the present invention as a light source, and can further include arbitrary components such as a member for holding the light source and a circuit for supplying power. The backlight device includes the surface light source device of the present invention as a light source, and further includes a housing, a circuit for supplying electric power, a diffusion plate for making light emitted more uniform, a diffusion sheet, a prism sheet, and the like. The components can be included. The use of the backlight device can be used as a backlight of a display device such as a liquid crystal display device that displays an image by controlling pixels and a display device that displays a fixed image such as a signboard.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Comparative Example 1: Front luminance-oriented type>
The optical performance of the conventional surface light source device 30 having the layer configuration shown in FIG. 7 was simulated. As shown in FIG. 7, the surface light source device 30 includes a light emitting surface structure layer 312 having a concavo-convex structure unit 312 constituted by a regular quadrangular pyramid-shaped depression, a substrate 131, a transparent electrode 141, a light emitting layer 142, a reflective electrode 143, and a sealing. This is an apparatus having a stop substrate 151 in this order. However, the light emitting layer 142 was a yellow light emitting layer or a blue light emitting layer.
The simulation conditions were as follows. In the simulation, when the blue light emitting layer was used as the light emitting layer 142 and when the yellow light emitting layer was used, calculation was performed separately to obtain color unevenness. The thickness of the substrate 131, the transparent electrode 141, the yellow light emitting layer, and the blue light emitting layer was 0.7 mm, 100 nm, 20 nm, and 15 nm, respectively. The refractive indexes of the substrate 131, the transparent electrode 141, the yellow light-emitting layer, and the blue light-emitting layer were 1.53, 1.90, 1.74, and 1.85, respectively. The hazes of the substrate 131, the transparent electrode 141, the yellow light emitting layer, and the blue light emitting layer were all 0%. The reflective electrode 142 was assumed to have a specular reflection with a reflectance of 100%. The orientation distribution of the light emitting layer 142 is Lambertian and has the characteristics shown in FIG.

  The thickness of the light exit surface structure layer 311 was set to 300 μm, and the refractive index was set to 1.54. The apex angle of the concavo-convex structure unit 312 of the light emitting surface structure layer was set to 90 ° (that is, θ1 = 45 °), and the pitch (the length of one side of the base of the quadrangular pyramid) was set to 200 μm.

Under these conditions, the front luminance (of yellow light, the same applies hereinafter), and the luminous intensity distribution of blue light (wavelength 480 nm) and yellow light (wavelength 575 nm) were determined. The direction for tilting the observation angle was set to a direction parallel to one of the bases of the quadrangular pyramid of the concavo-convex structure 312. Further, the light intensity ratio of blue light intensity / yellow light intensity at each observation polar angle was determined, the maximum value and the minimum value of the light intensity ratio at polar angles 0 to 90 ° were determined, and the color unevenness ratio was determined.
The color unevenness ratio obtained in this comparative example is set to 1, and the color unevenness ratios in the following other examples and comparative examples are shown as relative values. Further, the front luminance (relative value based on the value of Comparative Example 2 (unit: lm) as described later) was 2.178.

<Comparative Example 2: Color unevenness-oriented type>
The vertex angle of the concavo-convex structure unit 312 of the light emitting surface structure layer is changed to 60 ° (that is, θ1 = 60 °), and the pitch is 55 nm (the thickness is also changed by changing the height of the concavo-convex structure unit). The front luminance and the color unevenness ratio were obtained under the same conditions as in Comparative Example 1.
In this comparative example, the value (unit: lm) of yellow light front luminous intensity is set to 1, and the front luminance in other examples and comparative examples is shown as a relative value. In addition, the color unevenness ratio in this comparative example was 0.407.

  In addition to Comparative Examples 1 and 2, when the front luminance and the color unevenness ratio were obtained by changing the apex angle of the concavo-convex structure unit 312 in various ways, among them, Comparative Example 1 was the most excellent for the front luminance. Thus, it was found that Comparative Example 2 was most excellent in terms of color unevenness ratio.

<Example 1 and Comparative Example 3: Variation of Refractive Index>
With respect to the surface light source device 10 having the layer configuration shown in FIGS. 1 to 3, a change in optical performance due to a change in Δn value was simulated. As described with reference to FIGS. 1 to 3 and the first embodiment, the surface light source device 10 includes a second structural layer 112 having a regular quadrangular pyramidal structure unit 122 and a regular quadrangular pyramidal structure unit 112. This is a device having a first structural layer 111, a substrate 131, a transparent electrode 141, a light emitting layer 142, a reflective electrode 143, and a sealing substrate 151 in this order.

  Conditions regarding the substrate 131, the transparent electrode 141, the light emitting layer 142, and the reflective electrode 142 were the same as those in Comparative Example 1.

  The thickness of the first structural layer 111 was set to 300 μm, the apex angle of the first concavo-convex structure unit 112 was set to 40 ° (that is, θ1 = 70 °), and the pitch was set to 55 μm. The thickness of the second structural layer 121 was set to 300 μm, the apex angle of the second concavo-convex structure unit 122 was set to 90 ° (that is, θ1 = 45 °), and the pitch was set to 200 μm.

  Under these conditions, the refractive index n1 of the first structural layer 111 is variously changed in the range of 1.5 to 1.7, and the refractive index n2 of the second structural layer 121 is also variously changed to Δn The value of (= n2-n1) was variously changed in the range of −0.20 to +0.20, and the color unevenness ratio and the front luminance were obtained. The results are shown in FIGS.

The following can be understood from the results of FIGS.
From the results of FIG. 8, in the example of the present application (Δn is −0.20 to −0.16: indicated by a white square or a white triangle), the color unevenness ratio is less than half of the numerical value of Comparative Example 1. It can be seen that the color unevenness is reduced. Furthermore, it can be seen from the results of FIG. 9 that in the embodiment of the present invention, the front luminance is 1.2 times or more the numerical value of Comparative Example 2 and also has good front luminance.

<Example 2 and Comparative Example 4: Variation of Inclination Angle>
With respect to the surface light source device 10 having the layer configuration shown in FIGS. 1 to 3, a change in optical performance due to a change in the values of θ1 and θ2 was simulated.

  Conditions regarding the substrate 131, the transparent electrode 141, the light emitting layer 142, and the reflective electrode 142 were the same as those in Comparative Example 1.

The thickness and refractive index of the first structural layer 111 were set to 300 μm and 1.66, respectively, and the pitch of the first uneven structure unit 112 was set to 55 μm.
The thickness and refractive index of the second structural layer 121 were set to 300 μm and 1.50, respectively, and the pitch of the second uneven structure unit 122 was set to 200 μm.

  Under these conditions, the apex angle of the first structural layer 111 is variously changed in a range of 20 to 70 ° (that is, θ1 = 80 to 55 °), and the apex angle of the second structural layer 121 is also 80. The color unevenness ratio and the front luminance were obtained by variously changing in the range of ˜110 ° (that is, θ2 = 50 to 35 °). The results are shown in FIGS.

  10 and 11, the second structural layer apex angle is 80 ° to 100 ° (that is, θ2 = 50 to 40 °: indicated by a white triangle or white diamond), and the first structural layer An apex angle in the range of 20 to 60 ° (that is, θ1 = 80 to 60 °) corresponds to the present embodiment.

  From the results shown in FIG. 10, it can be seen that in this embodiment, the color unevenness ratio is half or less of the numerical value of Comparative Example 1, and the color unevenness is reduced. Furthermore, it can be seen from the results of FIG. 11 that the front luminance is 1.2 times or more the numerical value of Comparative Example 2 in the embodiment of the present invention, and also has good front luminance.

DESCRIPTION OF SYMBOLS 10, 20, 30: Surface light source device 100: Light emission efficiency improvement part 111: 1st structure layer 112: Uneven structure unit 121: 2nd structure layer 122: Uneven structure unit 131: Substrate 140: Organic EL element 141: Transparent Electrode 142: Light emitting layer 143: Reflective electrode 151: Sealing substrate 200: Light emission efficiency improving unit 211: First structural layer 212: Concavity and convexity structural unit 221: Second structural layer 222: Concavity and convexity structural unit 311: Light emission surface structural layer 312: Uneven structure unit

Claims (9)

A surface light source device comprising an organic electroluminescent element including a light emitting layer, and having a light output surface for emitting light from the organic electroluminescent element,
The surface light source device further includes a light output efficiency improving unit positioned on the device light output surface side from the organic electroluminescence element,
The light emission efficiency improving unit includes a first structure layer, and a second structure layer that is in contact with the first structure layer and located closer to the device light-emitting surface side than the first structure layer,
The first structural layer is a layer made of a material having a refractive index n1, having a first concavo-convex structure having an inclined surface with an inclination angle θ1 of 60 to 80 ° on the surface of the device light-emitting surface.
The second structural layer is a layer made of a material having a refractive index n2 having a second concavo-convex structure having an inclined surface with an inclination angle θ2 of 40 to 50 ° on a surface on the device light-emitting surface side,
n1 and n2 are represented by the following formula (1):
n2-n1 ≦ −0.12 (1)
A surface light source device that satisfies the above relationship. The first uneven structure and the second uneven structure are:
It is a concavo-convex structure constituted by concavo-convex structure units arranged repeatedly in two or more directions parallel to the device light exit surface, or a concavo-convex structure unit extending in one direction parallel to the device light exit surface, A concavo-convex structure configured by being repeatedly arranged in a direction perpendicular to the one direction and parallel to the device light exit surface;
The surface light source device according to claim 1.   The surface light source device according to claim 2, wherein the concavo-convex structure unit has a pyramid shape, a truncated pyramid shape, a prism shape extending in a direction parallel to the device light-emitting surface, or a combination thereof.   The surface light source device according to any one of claims 1 to 3, wherein the light output efficiency improving unit further includes a base film layer at a position farther from the device light output surface than the first structure layer.   5. The surface light source device according to claim 1, wherein the light output efficiency improving unit further includes an adhesive layer at a position farther from the device light output surface than the first structure layer.   The surface light source device according to claim 1, wherein the light emission efficiency improving unit further includes a substrate at a position farther from the device light exit surface than the first structural layer. The light emission efficiency improving unit is
In a position farther from the device light exit surface than the base film layer, further having an adhesive layer,
The surface light source device according to claim 4, further comprising a substrate at a position farther from the device light-emitting surface than the adhesive layer.   The surface light source device according to claim 1, wherein at least one of the layers constituting the light emission efficiency improving unit is a layer having light diffusibility.   The surface light source device according to claim 8, wherein the layer having light diffusibility is made of a material containing particles that impart light diffusibility.

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