JP2015176735A - El element, lighting device, display device and liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable increase of the efficiency of extracting light in an EL element.SOLUTION: An EL element 10 has an EL light emission portion in which a transparent electrode 4, a light emission layer and a counter electrode are laminated in this order, a translucent substrate 7 including an optical sheet having an irregular shape disposed on the surface of the translucent substrate 7 to emit light occurring in the light emission layer to the outside, and a light scattering layer 6 which is configured to contain light scattering particles and disposed between an EL light emission portion and the translucent substrate 7. The light scattering layer 6 is configured to have an irregular shape on a first surface 6a confronting the translucent electrode 4 of the EL light emission portion by aggregate of light scattering particles. On the second surface 6b confronting the translucent substrate 7, dense light scattering particles are aligned along an incidence side surface 13a which is a more smooth surface than the irregular shape of the first surface 6a.

Description

  The present invention relates to an EL element (electroluminescence element), a lighting device, a display device, and a liquid crystal display device.

2. Description of the Related Art Conventionally, for example, devices using EL elements are known as display light sources or illumination light sources in illumination devices, display devices, and liquid crystal display devices.
As such an EL element, for example, an organic EL element configured by providing a light emitting structure in which a light emitting layer containing a fluorescent organic compound is sandwiched between an anode and a cathode on one surface of a light transmitting substrate is used. Many. Such an organic EL device generates excitons by applying a DC voltage between the anode and the cathode, injecting electrons and holes into the light emitting layer and recombining them, and the excitons are deactivated. It emits light using the emission of light.
However, in such an EL element, when the light emitted from the light emitting layer is emitted from the translucent substrate to the outside, a part of the light is totally reflected on the surface of the translucent substrate, thereby causing internal reflection. There is a problem that light quantity loss occurs due to attenuation or the like while repeating. In this case, the external light extraction efficiency (hereinafter referred to as light extraction efficiency) is generally said to be about 20%.
Thus, if the light extraction efficiency is low, more input power is required to obtain the required luminance. Further, when the input power is increased, the load on the EL element is increased and the reliability of the element itself is lowered.
In order to improve the light extraction efficiency in the EL element, a fine unevenness is formed on the translucent substrate, and a part of the lost light beam is extracted to the outside by total reflection. Devices have been proposed. For example, Patent Document 1 proposes forming a microlens array in which a plurality of microlens elements are arranged in a plane on one surface of a translucent substrate.

JP 2002-260845 A

However, the prior art as described above has the following problems.
When the microlens element is provided on the surface of the translucent substrate as in the technique described in Patent Document 1, depending on the incident angle to the microlens element, there is a light component reflected to the light emitting layer side. There is a problem that such a light component is liable to cause a light amount loss by returning to the inside of the EL element.
Therefore, although the technique described in Patent Document 1 can improve the light extraction efficiency as compared with the case where the microlens element is not provided, there has been a strong demand for further improving the light extraction efficiency.

The present invention has been made in view of the above problems, and an object thereof is to provide an EL element capable of improving light extraction efficiency.
Another object of the present invention is to provide an illumination device, a display device, and a liquid crystal display device that can improve power saving performance by including such an EL element.

  In order to solve the above problems, an EL device according to the first aspect of the present invention includes an EL light emitting unit in which a transparent electrode, a light emitting layer, and a counter electrode are stacked in this order, and light generated in the light emitting layer is externally transmitted. The light is disposed between the EL light emitting unit and the light-transmitting substrate, and includes a light-transmitting particle and a light-transmitting particle disposed on the surface of the light-transmitting substrate. The light scattering layer is formed with an uneven shape due to an aggregate of the light scattering particles on the first surface facing the transparent electrode of the EL light emitting unit, and is suitable for the light transmitting substrate. On the second surface, the light scattering particles in a dense state are arranged along a smooth surface as compared with the uneven shape of the first surface.

  In the EL element, it is preferable that the light scattering layer is bonded to the transparent electrode through a light-transmitting smoothing layer that forms a smooth bonding surface that covers the uneven shape on the first surface. .

  In the EL element, the light-transmitting substrate further includes a light-transmitting sheet-like base material bonded to the surface facing the light scattering layer via a bonding layer, and the second surface has the light-transmitting substrate. It is preferable that the light scattering particles are aligned along the surface of the substrate opposite to the surface on which the bonding layer is provided.

  In the EL element, it is preferable that the light scattering particles on the second surface are aligned along a surface opposite to the surface on which the optical sheet of the translucent substrate is disposed.

  In the EL element, it is preferable that the light scattering particles of the light scattering layer have a particle density on the second surface higher than that on the first surface.

  In the EL element, it is preferable that the light scattering particles of the light scattering layer have a smaller average particle diameter on the second surface than an average particle diameter on the first surface.

  The illuminating device of the 2nd aspect of this invention is set as the structure provided with the said EL element as a light emission means.

  A display device according to a third aspect of the present invention includes the EL element, and the EL light emitting unit of the EL element includes a plurality of pixels that can be driven independently.

  A liquid crystal display device according to a fourth aspect of the present invention includes an image display element using liquid crystal, and the EL element according to any one of claims 1 to 6 disposed on the back surface of the image display element. It is set as the structure provided.

  A liquid crystal display device according to a fifth aspect of the present invention includes an image display element using liquid crystal and the illumination device according to claim 7 disposed on the back surface of the image display element.

According to the EL element of the present invention, since the light scattering layer in which the arrangement of the light scattering particles is changed is provided on the first surface facing the transparent electrode and the second surface facing the translucent substrate, the light extraction efficiency is improved. There is an effect that it can be improved.
Moreover, according to the illuminating device, display apparatus, and liquid crystal display apparatus of this invention, since the EL element of this invention is provided, there exists an effect that a power saving performance can be improved.

It is typical sectional drawing which shows the structure of the liquid crystal display device and EL element of embodiment of this invention. It is a typical partial enlarged view of the A section in FIG. FIG. 3 is a schematic partial enlarged view of a C part and a D part in FIG. 2. It is typical process explanatory drawing which shows an example of the manufacturing process of EL element of embodiment of this invention. It is typical sectional drawing which shows the structure of the principal part of the EL element of the 1st modification of embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
An EL element according to an embodiment of the present invention and a liquid crystal display device including the same will be described.
FIG. 1 is a schematic cross-sectional view showing a configuration of a liquid crystal display device and an EL element according to an embodiment of the present invention. FIG. 2 is a schematic partial enlarged view of a portion A in FIG. FIGS. 3A and 3B are schematic partial enlarged views of a C part and a D part in FIG. 2, respectively.
In addition, since each figure is a schematic diagram, the shape and dimension are exaggerated (the following drawings are also the same).

  As shown in FIG. 1, the liquid crystal display device 50 of the present embodiment includes a liquid crystal panel 11 (image display element) and the EL element 10 of the present embodiment. “EL” represents electroluminescence.

The liquid crystal panel 11 is an image display element using liquid crystal, and although various detailed configurations are omitted, various known configurations can be adopted.
As an example of a configuration suitable for the liquid crystal panel 11, for example, the light transmittance in pixels arranged in a rectangular shape in plan view is controlled, and the polarization state of the liquid crystal layer sandwiched between polarizing plates is controlled independently for each pixel. It is possible to adopt a configuration in which image display is performed by changing the above. In this case, the polarization state of the liquid crystal layer is controlled by applying an electric field corresponding to the image signal by an electrode (not shown) arranged for each pixel.

In this embodiment, the EL element 10 is disposed on the back surface of the liquid crystal panel 11 and is a light emitting means for illuminating the liquid crystal panel 11 from the back surface, and constitutes an illumination device in the liquid crystal display device 50.
For this reason, the EL element 10 only needs to be able to irradiate the liquid crystal panel 11 with uniform illumination light. However, in this embodiment, the EL element 10 has a plurality of light emitting pixels that can emit light independently. FIG. 1 shows a configuration of one light emitting pixel. For this reason, in the EL element 10, a plurality of configurations as shown in the figure are formed adjacent to each other in the horizontal direction and the depth direction shown in the drawing.

The schematic configuration of the EL element 10 includes a configuration in which the counter substrate 1, the light emitting structure 5 (EL light emitting unit), the light scattering layer 6, the translucent substrate 7, and the light directing film 9 are laminated in this order.
The light emitting structure 5 is a device portion that generates illumination light to be emitted to the liquid crystal panel 11 by EL light emission.
In the present embodiment, the light B0 generated in the light emitting structure 5 is transmitted through the light scattering layer 6, the light transmissive substrate 7, and the light directing film 9, and is emitted to the outside as the light B1. Irradiated.
In this specification, “translucency” means translucency regarding the wavelength light of the light B0 generated in the light emitting structure 5 unless otherwise specified.

The counter substrate 1 and the translucent substrate 7 are plate-like or sheet-like members arranged to face each other in order to sandwich the light emitting structure 5 and the light scattering layer 6 therebetween.
In the present embodiment, the counter substrate 1 forms one outer surface of the EL element 10 in the thickness direction.
Since the counter substrate 1 does not particularly need translucency, an appropriate material on which the light emitting structure 5 can be laminated, for example, synthetic resin, glass, metal, or the like can be used.
In the present embodiment, as an example, the same material as that of the translucent substrate 7 described later is employed.

The light transmittance of the translucent substrate 7 is preferably 50% or more and more preferably 80% or more as the total light transmittance.
As a material used for the translucent substrate 7, various glass materials can be used, and PMMA (polymethyl methacrylate resin), polycarbonate, polystyrene, PEN (polyethylene naphthalate resin), PET (polyethylene terephthalate resin). Synthetic resin materials such as can be used.
When a synthetic resin material is used, a particularly preferable material is a cycloolefin-based polymer. This polymer is excellent in all of the material properties such as processability, heat resistance, water resistance and optical translucency.

In the light emitting structure 5, the transparent electrode 4, the light emitting layer 3, and the counter electrode 2 are stacked in this order, and the light emitting structure 5 is disposed on the counter substrate 1 with the counter electrode 2 facing the counter substrate 1.
In the light emitting structure 5, the light emitting layer 3 emits light by applying a voltage to the transparent electrode 4 and the counter electrode 2, and various conventionally known configurations can be adopted.

  The transparent electrode 4 is one electrode for applying a voltage to the light emitting layer 3, and is made of a material that can transmit the light B0. Examples of such a light-transmitting electrode material include ITO (indium tin oxide).

The counter electrode 2 is the other electrode for applying a voltage to the light emitting layer 3. The material of the counter electrode 2 can be the same as that of the transparent electrode 4. However, in this embodiment, since the counter electrode 2 does not ask | require the presence or absence of translucency, a suitable metal material with favorable electroconductivity, for example, aluminum, silver, copper, etc. can also be employ | adopted.
In this embodiment, in order to emit as much light B0 as possible from the light directing film 9, the counter electrode 2 is preferably made of a material having a good light reflecting function. The light reflectance of the counter electrode 2 is preferably 50% or more and 100% or less.
When the counter electrode 2 is made of a material having low light reflectance or a transparent material, it is preferable to provide a light reflecting layer between the counter electrode 2 and the counter substrate 1. The light reflecting layer may be provided between the counter electrode 2 and the counter substrate 1, or may be provided on the counter substrate 1 or the counter electrode 2, or may be provided inside the counter substrate 1. is there.
Further, the counter substrate 1 itself can be made of a light-reflective material so that the counter substrate 1 can also serve as a light reflection layer.

  The polarities of the transparent electrode 4 and the counter electrode 2 are not particularly limited, but in the present embodiment, as an example, the transparent electrode 4 is used as an anode and the counter electrode 2 is used as a cathode.

The light emitting layer 3 can be a white light emitting layer, for example. In this case, the transparent electrode 4 is made of ITO, the counter electrode 2 is made of aluminum, and CuPc (copper phthalocyanine) / α-NPD is doped with 1% rubrene from the transparent electrode 4 side to the counter electrode 2, and perylene is added to dioctylanthracene. A configuration in which 1% dope / Alq3 / lithium fluoride is laminated in this order can be adopted.
However, the configuration of the light-emitting layer 3 is not limited to this, and an appropriate material that can set the wavelength of light emitted from the light-emitting layer 3 to R (red), G (green), and B (blue). Any configuration used may be employed.
In addition, when the liquid crystal display device 50 is used for a full color display, for example, the light emitting layer 3 is separately applied to three types of light emitting materials corresponding to R, G, and B, or a color is formed on the white light emitting layer. A configuration in which filters are stacked can be employed.

  In the present embodiment, since the light emission of the EL element 10 is controlled for each light emitting pixel, the light emitting structure 5 is formed corresponding to each light emitting pixel, and the transparent electrode 4 and the counter electrode 2 of each light emitting pixel include It is wired to a drive unit (not shown).

The light scattering layer 6 is a layered part that transmits light incident on the transparent electrode 4 to the translucent substrate 7 side and is scattered to change the traveling direction of the light. Of light scattering particles.
The light scattering layer 6 can easily transmit light B0 incident from the transparent electrode 4 by changing the particle density of the light scattering particles in the layer thickness direction, and transmits light incident from the translucent substrate 7 side. 7 is easily reflected.
Specifically, as schematically shown in FIG. 2, the light scattering layer 6 includes a first light scattering layer 6A, a second light scattering layer 6B, and a first light scattering layer 6B between the first surface 6a and the second surface 6b. Is formed.
Since FIG. 2 is a schematic diagram, a boundary surface S is illustrated between the first light scattering layer 6A and the second light scattering layer 6B. However, a physical interface is formed on the boundary surface S. Not required. For example, a configuration in which the particle density of the light scattering particles continuously changes from the first light scattering layer 6A to the second light scattering layer 6B and a physical interface is not formed is possible.
In the present embodiment, the boundary surface S indicates the position of the boundary where the particle density of the light scattering particles on the manufacturing method is switched, and is not necessarily a physical interface.

  The first light scattering layer 6 </ b> A is a layered portion disposed so that the first surface 6 a faces the transparent electrode 4. In the present embodiment, the first light scattering layer 6 </ b> A is bonded to the surface 4 a of the transparent electrode 4 via the smoothing layer 12.

As shown in FIG. 3A, the first light scattering layer 6A has a configuration in which light scattering particles 16A are dispersed in a binder 19A.
The light scattering particles 16A were selected from, for example, inorganic particles such as silica, alumina, titanium oxide, and barium sulfate, organic particles such as acrylic, styrene, acrylic / styrene copolymer, and melamine, or these particles. What mixed 2 or more types of particle | grains is employable.
The average particle diameter of the light scattering particles 16A is preferably 50 nm to 1000 nm, and more preferably 100 nm to 300 nm. The particle diameter can be measured using SALD-7100 (trade name; manufactured by Shimadzu Corporation).
The first surface 6 a of the first light scattering layer 6 </ b> A has a concavo-convex shape due to the distribution of aggregates 17 formed by agglomerating light scattering particles 16 </ b> A. Since the uneven shape is formed by the aggregate 17, it does not have regularity, and the uneven pitch and depth vary. As the size of the unevenness of the first surface 6a, the height difference between adjacent unevenness is preferably about 0.2 μm to 3 μm.
The number of aggregates 17 forming one convex portion is preferably, for example, about 2 to 10 although it depends on the particle size distribution of the light scattering particles 16A.

  In the first light scattering layer 6A, it is preferable that the particle density of the light scattering particles 16A increases from the first surface 6a toward the boundary surface S. However, it is preferably lower than the particle density of the light scattering particles 16B in the second light scattering layer 6B described later.

The binder 19A is made of an appropriate transparent resin material whose refractive index has a refractive index difference from the refractive index of the light scattering particles 16A.
As the binder matrix material of the binder 19A, for example, an ionizing radiation curable or thermosetting synthetic resin, for example, an acrylic resin, a polyester resin, a polycarbonate resin, a styrene resin, or an acrylic / styrene copolymer resin is used. Can be used.
When ultraviolet rays are used as the ionizing radiation, a photopolymerization initiator is added to the hard coat layer forming coating solution in which the light scattering particles 16A are mixed with the binder matrix material. Although a well-known photoinitiator can be used for a photoinitiator, it is preferable to use what was suitable for the binder matrix formation material to be used.
As the photopolymerization initiator, for example, benzoin such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl methyl ketal, and alkyl ethers thereof can be used. The usage-amount of a photoinitiator is 0.5 to 20 weight part with respect to a binder matrix formation material. Preferably they are 1 weight part or more and 5 weight part or less.

The smoothing layer 12 is a layered portion for joining the first light scattering layer 6A to the transparent electrode 4 while forming a smooth joining surface 12a covering the first light scattering layer 6A, and has a light-transmitting property. Made of resin.
As a material of the smoothing layer 12, an appropriate resin material can be selected from the above synthetic resins suitable for the binder 19A.
However, the refractive index of the smoothing layer 12 is set so that the light B0 is not totally reflected by the surface 4a or the amount of total reflection can be reduced. That is, the refractive index of the smoothing layer 12 has a refractive index close to the refractive index of the transparent electrode 4 when it is equal to or higher than the refractive index of the transparent electrode 4 or less than the refractive index of the transparent electrode 4. The refractive index difference when the refractive index is less than that of the transparent electrode 4 is preferably 0.4 or less, and more preferably 0.2 or less.

In general, the refractive index of the material used for the transparent electrode 4 is often a high refractive index. Therefore, in order to increase the refractive index of the smoothing layer 12 accordingly, the resin material similar to the binder 19A described above has a high refractive index. A configuration in which fine particles are added is also possible.
For example, as the high refractive index fine particles, for example, one kind of metal oxides such as zirconia, titania, potassium titanate, barium titanate, and zinc oxide can be used alone or in combination of two or more kinds. . Among these, zirconia and titania are particularly preferable because they have properties such as high refractive index, excellent chemical stability, high light transmittance in the visible light range, and easy particle size alignment.
Moreover, the surface of these highly refractive fine particles may be modified.

By bonding the first light scattering layer 6A to the transparent electrode 4 through such a smoothing layer 12, the light B0 transmitted through the transparent electrode 4 and reaching the surface 4a is substantially totally reflected. It enters the smoothing layer 12 (including the case where it is totally reflected) and reaches the first surface 6a.
Moreover, since the transparent electrode 4 can be formed on the smooth joining surface 12a by providing the smoothing layer 12, the variation in the layer thickness of the transparent electrode 4 can be suppressed.
For example, when the transparent electrode 4 is formed directly on the first surface 6a, the layer thickness of the transparent electrode 4 varies depending on the uneven shape of the first surface 6a. If the layer thickness of the transparent electrode 4 varies, there may be a problem that uneven brightness occurs or a short circuit of current occurs. In the present embodiment, these can be prevented.

  As shown in FIG. 3B, the second light scattering layer 6B is laminated with the first light scattering layer 6A at the boundary surface S, and is arranged in a layered manner so that the second surface 6b faces the translucent substrate 7. Part. In the present embodiment, as shown in FIG. 2, the second light scattering layer 6 </ b> B is bonded to the incident-side surface 7 a of the translucent substrate 7 through the bonding layer 14 while being laminated on the base material 13. Yes.

As shown in FIG. 3B, the second light scattering layer 6B has a configuration in which the light scattering particles 16B are dispersed in the binder 19B.
As the light scattering particles 16B, one or more appropriate particle materials can be selected from the particle materials suitable for the light scattering particles 16A described above. The kind of the light scattering particles 16B may be the same as or different from the light scattering particles 16A.
The average particle diameter of the light scattering particles 16B can be the same as that of the light scattering particles 16A. However, as one means for forming the layered alignment portion 18 to be described later, when the average particle diameter of the light scattering particles 16B is made small, the light scattering particles 16B having an average particle diameter smaller than that of the light scattering particles 16A should be adopted. You can also.
For this reason, as an average particle diameter of the light-scattering particle | grains 16B, 50 nm-300 nm are preferable, for example, and 50 nm-150 nm are more preferable.

  The binder 19B is made of an appropriate transparent resin material whose refractive index has a refractive index difference from the refractive index of the light scattering particles 16B. Specifically, an appropriate resin material can be selected and used from the materials suitable for the binder 19A described above according to the refractive index of the light scattering particles 16B. The type of the binder 19B may be the same as or different from the binder 19A.

As shown in FIG. 2, the base material 13 is a sheet-like member that forms a sheet-like assembly 15 by laminating the light scattering layers 6.
As a material of the base material 13, a resin film having translucency can be adopted. For example, a stretched or unstretched film made of a thermoplastic resin such as cellulose triacetate, polyester, polyamide, polyimide, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polymethyl methacrylate, polycarbonate, polyurethane, etc. Can do.
The transmittance of the base material 13 is preferably 90% or more, for example.

As the bonding layer 14, the bonding layer 14 can be bonded to the light-transmitting substrate 7, and an appropriate pressure-sensitive adhesive or adhesive having light-transmitting properties can be employed.
Examples of suitable materials for the bonding layer 14 include various pressure-sensitive adhesives and adhesives such as acrylic, urethane, rubber, and silicone.
In any case, since the bonding layer 14 is adjacent to the light emitting structure 5 that is at a high temperature, it is desirable to use a material having a storage elastic modulus G ′ of about 1.0 × 10 ⁺⁴ (Pa) or more at 100 ° C. .
If the storage elastic modulus G ′ is lower than this, a positional deviation may occur between the base material 13 and the translucent substrate 7 during use. Such misalignment leads to misalignment between the light emitting pixels of the light emitting structure 5 and the light directing film 9, and such misalignment decreases the light extraction efficiency by the light directing film 9 described later. May lead to

In addition, in order to ensure the separation dimension between the base material 13 and the translucent substrate 7 stably, for example, transparent fine particles such as beads may be mixed in the bonding layer 14. In this case, the difference between the refractive index of the transparent fine particles and the refractive index of the material serving as the base of the bonding layer 14 is preferably less than 0.01. By satisfying such a refractive index difference, even when transparent fine particles are mixed, light scattering due to the refractive index difference between the fine particles and the base material of the bonding layer 14 is less likely to occur. Since scattering of light due to a difference in refractive index from the base material is suppressed, the transmitted light travels almost straight in the substrate 13 (including a case where the light travels completely straight). For this reason, it becomes possible to maintain the joining layer 14 in a transparent state.
Further, the pressure-sensitive adhesive or adhesive constituting the bonding layer 14 may be a double-sided tape or a single layer.

  Moreover, it is preferable that the refractive index of the base material 13, the joining layer 14, and the translucent board | substrate 7 is made into the substantially same refractive index (including the case where it is equal) so that total reflection does not occur easily in each interface. As for the refractive index of the base material 13, the joining layer 14, and the translucent board | substrate 7, it is preferable that the refractive index difference between adjacent members is 0.1 or less, for example.

The second light-scattering layer 6B is incident on the first light-scattering layer 6A from the transparent electrode 4 side, and the light B0 that is incident while being scattered is scattered through the base material 13 as light B2 while being scattered. 7 and the light B3 incident from the translucent substrate 7 through the base material 13 are likely to be reflected toward the translucent substrate 7 like the light B4.
Specifically, the particle density of the light scattering particles 16B in the second light scattering layer 6B is equal to or higher than the particle density of the first light scattering layer 6A, and the particle density is the incident side surface 13a of the substrate 13. It is comprised so that it may become the highest in the 2nd surface 6b adjacent to.
For this reason, on the second surface 6b of the second light scattering layer 6B, the light scattering particles 16B in a dense state are along the incident side surface 13a of the base material 13 which is a smooth surface compared to the uneven shape of the first surface 6a. A layered alignment portion 18 is formed in the vicinity of the incident side surface 13a. Since the light scattering particles 16B are densely packed in the layered alignment portion 18, most of the incident light passes through the light scattering particles 16B.
In contrast, the second light scattering layer 6B in the region between the layered alignment portion 18 and the boundary surface S is a region where the particle density of the light scattering particles 16B is lower than that of the layered alignment portion 18, and the light scattering particle 16B. In between, a gap filled with the binder 19B is formed,

  As described above, the EL element 10 according to this embodiment includes the counter electrode 2, the light emitting layer 3, the transparent electrode 4, the first light scattering layer 6A, and the second electrode between the counter substrate 1 and the translucent substrate 7. The light scattering layer 6B, the base material 13, and the bonding layer 14 are laminated in this order from the counter substrate 1 side.

  In the EL element 10 of the present embodiment, as shown in FIG. 1, the light directing film 9 is bonded to the light emitting side surface 7 b of the light transmitting substrate 7 opposite to the light incident side surface 7 a through the bonding layer 8. ing.

The light directing film 9 gives the directivity centered on the front direction, which is the normal direction of the light transmitting substrate 7, to the outside generated by the light emitting structure 5 and transmitted through the light transmitting substrate 7. In order to emit light, the optical sheet has an uneven shape on the surface.
The light directing film 9 is provided with a light directing structure layer portion 9B having an uneven shape on one surface of a base material portion 9A made of a sheet-like translucent material.

The base material portion 9A can use various materials having optical transparency with respect to the wavelength of the light B0 emitted from the light emitting layer 3, for example, a synthetic resin material for an optical member can be used. it can.
Examples of such synthetic resin materials include, for example, thermoplastic resins such as polyester resin, acrylic resin, polycarbonate resin, polystyrene resin, MS (acrylic and styrene copolymer) resin, polymethylpentene resin, and cycloolefin polymer. Resins can be mentioned.
Other examples include ionizing radiation curable resins made of oligomers such as polyester acrylates, urethane acrylates, epoxy acrylates, or acrylates.

The light directing structure layer portion 9B is formed by arranging unit prism lenses 9b having a polygonal cross section extending in one direction on the surface of the base material portion 9A so as to cross each other in a biaxial direction.
For this reason, the surface shape of the light directivity structure layer portion 9B is a combination of the flat surfaces 9a, and has no curved surface other than the curved surface of the minute roundness on the top of the light directivity structure layer portion 9B.
Thus, by providing the surface of the light directivity structure layer portion 9B with a flat surface 9a instead of a curved surface, the light transmitted through the light directivity structure layer portion 9B, the transmittance of the reflected light, and the incident angle of the reflectivity It becomes possible to strengthen the angle dependence with respect to. For this reason, since the angle of the light which permeate | transmits the light directivity structure layer part 9B is restrict | squeezed, it becomes possible to enlarge the directivity of light.

  The biaxial direction in which the unit prism lenses 9b are arranged is not particularly limited, but the crossing angle between the biaxial directions is preferably 80 ° or more and 90 ° or less. In the present embodiment, as an example, the intersection angle is 90 °. Since FIG. 1 is a cross-sectional view, the unit prism lenses 9b arranged in the left-right direction on the paper surface are shown, and the unit prism lenses 9b arranged in the depth direction on the paper surface are omitted.

The cross-sectional shape of the unit prism lens 9b is an example in which the flat surface 9a is formed in an isosceles triangle shape having an apex angle θ as an example of a polygonal shape. The apex angle θ is preferably 80 ° or more and 100 ° or less.
However, in order to enhance the light redistribution effect in the light directivity structure layer portion 9B and strengthen the directivity of the light B1 emitted from the light directivity film 9, the apex angle of each unit prism lens 9b in the biaxial direction It is preferable to set θ to the same value. In this case, the light is less likely to be scattered by the blism in the direction of the angle with low directivity.
The heights of the unit prism lenses 9b may all be the same or may be changed as appropriate.
The same material as that of the base material portion 9A can be adopted as the material of the light directing structure layer portion 9B.

The light directing film 9 having such a configuration can be formed by, for example, pouring and solidifying the above-described material into a previously formed mold. This die uses a diamond tool having a shape similar to the cross-sectional shape of the unit prism lens 9b, and cuts a concave shape corresponding to the outer shape of the unit prism lens 9b on a die base material subjected to copper plating. Can be manufactured.
Further, the light directing film 9 is formed by extrusion molding or injection molding using a thermoplastic resin, for example, an ionizing radiation curable resin such as an ultraviolet curable resin, in addition to the method of forming by casting solidification as described above. It can also be formed by ionizing radiation forming method. At that time, the shapes of the base material portion 9A and the light directivity structure layer portion 9B may be integrally formed. For example, the base material portion 9A and the light directivity structure layer portion 9B are separately formed. Then, you may make it assemble.
In any case, the material for forming the light directing film 9 can be formed by dispersing a diffusing agent such as a filler that exhibits a light diffusing function.
Furthermore, ultrafine particles such as antimony-containing tin oxide (ATO) or tin-containing indium oxide (ITO), which are conductive fine particles, may be dispersed in the light directing film 9 as an antistatic agent. By dispersing the antistatic agent, the antifouling property of the light directing film 9 can be improved.

In the light-directing film 9, for example, when the light-directing structure layer portion 9B is formed on the base material portion 9A by an ionizing radiation molding method or the like, as the base material portion 9A, for example, cellulose triacetate, polyester, polyamide A stretched or unstretched transparent film made of a thermoplastic resin such as polyimide, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, methyl polymethacrylate, polycarbonate, and polyurethane can also be used.
In this case, the thickness of the base material portion 9A is preferably 50 μm to 300 μm from the viewpoint of workability and handling, although it depends on characteristics such as rigidity of the material to be used.

As the bonding layer 8 for bonding such a light directing film 9 to the emission-side surface 7b, an appropriate pressure-sensitive adhesive or adhesive having translucency can be adopted.
As the material of the bonding layer 8, the same material and configuration as those of the bonding layer 14 described above can be employed. However, the bonding layer 8 does not have to be made of the same material and configuration as the bonding layer 14. For example, the bonding layer 8 has the above-described materials and configurations according to differences in materials to be bonded and temperature conditions during use. It is possible to select appropriate materials and configurations different from those of the bonding layer 14.
In the bonding layer 8, the light directional film 9 allows light emitted from the emission side surface 7 b of the translucent substrate 7 to enter the light directional film 9 while maintaining the emission angle distribution. This is particularly important for keeping the directivity within a predetermined range.
For this reason, the bonding layer 8 is particularly preferable to have a transparent configuration in which the stability of the layer thickness is ensured and the scattering of the transmitted light of the bonding layer 8 is suppressed. Specifically, for example, a configuration in which fine particles such as beads having a small difference in refractive index from the base material of the bonding layer 8 is particularly preferable. The bonding layer 8 is preferably a refractive index between the light directing film 9 and the translucent substrate 7 because reflection at the interface with each is suppressed.

In order to manufacture such an EL element 10, for example, the assembly 15 is attached to the incident side surface 7 a of the translucent substrate 7 via the bonding layer 14, and the first surface 6 a of the light scattering layer 6 is smoothed. After providing the conversion layer 12, the light emitting structure 5 is formed on the smoothing layer 12.
Then, the counter substrate 1 is bonded onto the light emitting structure 5. Next, the light directing film 9 formed as described above is bonded to the incident side surface 7 a of the translucent substrate 7 through the bonding layer 8.

Here, the manufacturing method of the assembly 15 will be described in detail.
4A, 4B, and 4C are schematic process explanatory views showing an example of a manufacturing process of the EL element according to the embodiment of the present invention.

First, as shown in FIG. 4A, the base material 13 is formed. Both the incident side surface 13a and the emission side surface 13b of the substrate 13 are flat surfaces.
At this time, the bonding layer 14 (not shown) may be applied in advance on the emission side surface 13b, or may be applied after forming the light scattering layer 6 described below.

Next, in order to form the 2nd light-scattering layer 6B on the incident side surface 13a, the light-scattering particle coating liquid 60B is apply | coated (refer FIG.4 (b)).
The coating method can be appropriately selected from known coating methods such as spin coating, die coating, and curtain coating.

The light scattering particle coating liquid 60B is obtained by mixing the light scattering particles 16B with an uncured binder 19B so that a necessary particle density can be obtained. In the second light scattering layer 6B, the light scattering particles 16B need to be aligned at least along the incident side surface 13a.
Such a configuration is naturally formed to some extent because the light scattering particles 16B tend to settle in the binder 19B.
In order to more reliably form such a configuration, for example, a light scattering particle coating liquid 60B containing a high concentration of light scattering particles 16B having a minute particle diameter may be used. In this case, since the light scattering particles 16B having a small particle diameter enter the gap between the light scattering particles 16B having a large particle diameter during the mixing process, the light scattering particles 16B are easily aligned in the vicinity of the incident side surface 13a.
For example, when the light scattering particles 16B are titanium oxide and the binder 19B is acrylic, the light scattering particle coating solution 60B containing 50 wt% of titanium oxide with a particle size of less than 100 nm is 0.5 μm to 1 μm in thickness. It is preferable to apply to.
In addition, when the light scattering particle 16B has a large particle size, the sedimentation effect due to its own weight increases, so the concentration of the light scattering particle 16B in the light scattering particle coating liquid 60B may be set low.
For example, in the case of the same material and coating thickness as described above, a light scattering particle coating solution 60B containing 50 wt% of titanium oxide having a particle size of about 100 nm in acrylic is suitable.

After the light scattering particle coating liquid 60B is applied and then dried and cured to form the second light scattering layer 6B, the upper surface of the second light scattering layer 6B that becomes the boundary surface S as shown in FIG. In addition, in order to form the first light scattering layer 6A, the light scattering particle coating liquid 60B is applied.
As a coating method, a method similar to the coating method of the light scattering particle coating liquid 60B can be employed.

The light scattering particle coating liquid 60A is obtained by mixing the light scattering particles 16A with the uncured binder 19A so that the necessary particle density of the light scattering particles 16A can be obtained. In the first light scattering layer 6A, at least the first surface 6a needs to be formed with an uneven shape due to the aggregate 17.
Such a configuration is naturally formed to some extent when the binder 19A includes light scattering particles 16A made of fine particles of low concentration.
In order to more reliably form a suitable uneven shape, for example, a light scattering particle coating liquid 60A containing a large concentration of light scattering particles 16A having a large particle diameter may be used. In this case, since the diameter of the aggregate 17 formed by the aggregation generated in the mixing process becomes large, a preferable uneven shape of, for example, about 0.2 μm to 0.8 μm can be easily obtained.
For example, when the light scattering particles 16B are titanium oxide and the binder 19B is acrylic, the light scattering particle coating solution 60A containing 30 wt% of titanium oxide having a particle size exceeding 100 nm in thickness is 0.5 μm to 1 μm. It is preferable to apply to.
When the particle diameter of the light scattering particles 16A is not so large, the concentration in the light scattering particle coating liquid 60A may be set to a concentration that easily aggregates into an appropriate lump shape.
For example, in the case of the same material and coating thickness as described above, a light scattering particle coating solution 60A containing 20 wt% of titanium oxide having a particle size of about 100 nm in an acrylic is preferable.

When the light scattering particle coating solution 60A is applied and then dried and cured, the binder 19A contracts to expose the aggregates 17 on the surface, and the first light scattering layer 6A on which the first surface 6a having the uneven shape is formed. can get.
In such a first light scattering layer 6A, the light scattering particles 16A also aggregate inside, and the binder 19A is filled between the separated aggregates 17.
In this way, the light scattering layer 6 is formed on the substrate 13. In addition, when the bonding layer 14 is not applied to the base material 13 in advance, the bonding layer 14 is applied.
In this way, the assembly 15 is manufactured.

  Such an assembly 15 is manufactured in advance as a continuous sheet, for example, and when the EL element 10 is manufactured, it can be cut into a required size and attached, so that the production efficiency is increased. preferable.

Next, the operation of the EL element 10 will be described.
As shown in FIG. 1, the light B0 generated in the light emitting layer 3 reaches the surface 4 a of the transparent electrode 4.
Since the light B0 is emitted from the light emitting layer 3 in various directions, it has a predetermined light distribution.
In the present embodiment, as shown in FIG. 2, a smoothing layer 12 having a refractive index close to (including matching with) the refractive index of the transparent electrode 4 is provided in contact with the surface 4 a.
Therefore, the light B0 travels substantially straight along the path (including the case where the light travels straight) and is incident on the smoothing layer 12 without being totally totally reflected by the surface 4a (including the case where it is not totally reflected). The vehicle travels substantially straight and reaches the first surface 6a.
For this reason, the light B0 travels through the smoothing layer 12 and reaches the first surface 6a without substantially changing the light distribution.

As shown in FIG. 3A, the first surface 6a has an uneven shape formed by the aggregates 17 of the light scattering particles 16A, so that the return light to the smoothing layer 12 side is reduced, and the light B0 is Efficiently enters the first light scattering layer 6A.
That is, the light scattered by the light scattering particles 16 </ b> A and returning to the smoothing layer 12 is uniformly emitted from the surface of the aggregate 17 to the outside, so that the light scattered from the side of the convex portion is transmitted to the transparent electrode 4. It re-enters the convex part of the adjacent aggregate 17 without heading.
On the other hand, for example, on the first surface 6a, if the light scattering particles 16A are densely arranged on the plane, the light scattering particles 16A function as a scattering reflection surface. All scattered light emitted to the smoothing layer 12 side once enters the smoothing layer 12 and travels toward the transparent electrode 4. For this reason, compared with the case where the 1st surface 6a is formed in uneven | corrugated shape, the probability that it will reenter in a light-scattering layer falls.
Further, if the first surface 6a is formed as a flat surface by only the binder 19A, the smoothing layer 12 has a higher refractive index than the refractive index of the binder 19A. Reflection occurs. For this reason, the return light to the smoothing layer 12 increases.
According to the first surface 6a as in the present embodiment, the generation of return light such as these is suppressed due to the uneven shape, so that the light B0 efficiently enters the first light scattering layer 6A.

The light B incident on the first light scattering layer 6A is scattered by the light scattering particles 16A and reaches the second light scattering layer 6B while changing the traveling direction.
The light B0 is scattered by the light scattering particles 16B in the second light scattering layer 6B and travels while being deflected in various directions, so that the traveling direction of the light is diversified as a whole.
And as shown in FIG.3 (b), it injects into the translucent board | substrate 7 as the light B2 radiated | emitted from the 2nd surface 6b in a wider range rather than the light distribution on the incident side.

As shown in FIG. 1, among the light B <b> 2 incident on the light transmissive substrate 7, for example, B <b> 2 ′ that travels in an oblique direction travels substantially straight inside the light transmissive substrate 7, the bonding layer 8, and the light directing film 9. Then, it reaches the flat surface 9a of the unit prism lens 9b.
Since the flat surface 9a is inclined with respect to the emission-side surface 7b, the light B2 ′ is refracted according to the incident angle with respect to the flat surface 9a and is deflected in a direction close to the front direction of the EL element 10. Is emitted.

On the other hand, of the light B2, the light B2 '' radiated in the direction near the vertical from the incident-side surface 7a is totally reflected by the paired flat surfaces 9a, and therefore has substantially the same angle as the light B3. Then, it returns to the incident side surface 7a.
In the case where the light scattering layer 6 is not provided, the returning light B3 enters the transparent electrode 4 directly after being emitted from the translucent substrate 7 and attenuates inside the light emitting structure 5.
However, in the present embodiment, as shown in FIG. 3B, since the second light scattering layer 6B is provided via the base material 13, the light B3 traveling from the incident side surface 7a toward the transparent electrode 4 side. Passes through the substrate 13 and reaches the second surface 6b of the second light scattering layer 6B.
Since the second surface 6b is densely aligned along the flat incident-side surface 13a, a layered alignment portion 18 that functions as a scattering reflection surface with respect to the light B0 is formed. For this reason, the light B3 is scattered and reflected like the light B4, and becomes the light directed to the light directing film 9 like the light B2. At this time, since the light B4 has a light distribution by being scattered and reflected, most of the light B4 is reflected in a direction not totally reflected by the flat surface 9a. As a result, when the light B4 reaches the flat surface 9a, it is emitted to the outside according to the incident angle distribution.

That is, in the EL element 10, the light B0 that has passed through the transparent electrode 4 is transmitted while being scattered by the light scattering layer 6. Therefore, like the light B2 ′, the light component emitted from the light directing film 9 to the outside is reduced. Increased compared to the case where the light scattering layer 6 is not provided.
Also, for example, when the light is totally reflected by the flat surface 9a of the unit prism lens 9b as in the case of the light B2 '', the second light scattering layer 6B of the light scattering layer 6 has the layered alignment portion 18 (FIG. 3B). 1), the reflection is repeated between the unit prism lens 9b and the layered alignment portion 18 and is scattered and reflected by the layered alignment portion 18 as shown by the white arrow in FIG. As in the case of ', the component to be emitted to outside increases.
For this reason, as in the case where the layered alignment portion 18 is not provided, the component that causes the light B3 to return to the transparent electrode 4 and lose the light amount is reduced.

Thus, the EL element 10 includes the light scattering layer 6 in which the arrangement of the light scattering particles is changed between the first surface 6 a facing the transparent electrode 4 and the second surface 6 b facing the translucent substrate 7. The light extraction efficiency can be improved.
In addition, since the liquid crystal display device 50 includes such an EL element 10, the power consumption of the EL element 10 for obtaining necessary luminance is reduced, and the liquid crystal display device 50 becomes a power-saving device.

[First Modification]
Next, an EL element according to a first modification of the present embodiment will be described.
FIG. 5 is a schematic cross-sectional view showing the configuration of the main part of the EL element of the first modification of the embodiment of the present invention.

In the EL element 20 of this modification, the base material 13 and the bonding layer 14 of the EL element 10 of the above embodiment are deleted, and the second surface 6b of the light scattering layer 6 is formed on the incident side surface 7a of the translucent substrate 7. It is a thing.
The EL element 20 can be used as a lighting device in the liquid crystal display device 50 in place of the EL element 10 of the above embodiment.
Hereinafter, a description will be given focusing on differences from the above embodiment.

  In such an EL element 20, as shown in FIGS. 4B and 4C, the second light scattering layer 6B is formed on the incident-side surface 7a of the translucent substrate 7, and then the above-described embodiment. It can be manufactured in the same manner as in the above embodiment except that the first light scattering layer 6A is formed in the same manner as in the above.

According to the EL element 20, since the light scattering layer 6 similar to that in the above embodiment is provided between the transparent electrode 4 and the translucent substrate 7, the light extraction efficiency can be improved as in the above embodiment. it can.
At that time, in this modification, the base material 13 and the bonding layer 14 are deleted. For this reason, loss of light quantity due to reflection and absorption due to these elements is eliminated, so that the light extraction efficiency can be further improved as compared with the above embodiment.
Moreover, since the base material 13 and the joining layer 14 can be deleted, manufacturing cost can be reduced more.

  In the description of the embodiment and the first modified example, the example in the case of forming the smooth bonding surface 12a covering the first surface 6a of the first light scattering layer 6A has been described, but the smoothing layer 12 is not provided. However, the smoothing layer 12 can be omitted when the transparent electrode 4 having a layer thickness that does not cause uneven brightness or short-circuiting can be formed.

  In the description of the embodiment and the first modified example, the light scattering layer 6 has been described as an example in which the light scattering layer 6 includes two layers of the first light scattering layer 6A and the second light scattering layer 6B. As long as the uneven first surface 6a can be formed, a single-layer structure in which the arrangement and particle density of light scattering particles change within a certain layer thickness may be employed. Moreover, it is good also as a multilayer structure of three or more layers.

In the description of the embodiment and the first modification, the EL elements 10 and 20 have been described as examples in the case where the EL elements 10 and 20 are illumination devices that are arranged and used on the back surface of the image display element of the liquid crystal display device 50. The EL elements 10 and 20 can be used as an illumination device that illuminates an object other than the image display element.
In addition, since the EL elements 10 and 20 can be driven by pixels, the EL elements 10 and 20 can be used as a display device that displays, for example, images, character information, and pattern patterns by causing each light emitting pixel to emit light based on an image signal. It is.

In the description of the above-described embodiment and the first modification, the example has been described in which the light emitting pixels of the EL elements 10 and 20 are composed of a plurality of pixels that can be driven independently. It is not essential to drive.
For example, the surface emitting light source can be configured by simultaneously driving the light emitting layers.

In the description of the above embodiment and the first modification, the unit prism lens 9b of the light directivity structure layer portion 9B has been described as an example in the case of a prism lens having a polygonal prism shape such as a triangle. A polygonal prism lens can be formed.
In addition to these, the concavo-convex shape of the light directing structure layer portion 9B may employ various known concavo-convex shapes. For example, the light directivity structure layer portion 9B does not have a unit prism lens, and may be formed by a plurality of uneven shapes having different sizes and shapes.

  All the components described in the above embodiment and the first modification can be implemented by appropriately changing or deleting the combination within the scope of the technical idea of the present invention.

3 Light emitting layer 4 Transparent electrode 4a Surface 5 Light emitting structure (EL light emitting part)
6 Light Scattering Layer 6A First Light Scattering Layer 6B Second Light Scattering Layer 6a First Surface 6b Second Surface 7 Translucent Substrate 7a Incident Side Surface 8, 14 Bonding Layer 9 Light Directional Film (Optical Sheet)
9B Light directivity structure layer part 9a Flat surface 9b Unit prism lens 10, 20 EL element (illumination device, display device)
11 Liquid crystal panel (image display element)
12 Smoothing layer 12a Bonding surface 13 Base material 15 Assembly 16A, 16B Light scattering particle 17 Aggregate 18 Layered alignment portion 19A, 19B Binder 50 Liquid crystal display devices B0, B1, B2, B2 ′, B2 ″ B3, B4, B5 light

Claims (10)

An EL light emitting unit in which a transparent electrode, a light emitting layer, and a counter electrode are laminated in this order;
In order to emit the light generated in the light emitting layer to the outside, a translucent substrate having an optical sheet having a concavo-convex shape disposed on the surface;
A light scattering layer configured to include light scattering particles and disposed between the EL light emitting unit and the translucent substrate;
With
The light scattering layer is
On the first surface of the EL light emitting portion facing the transparent electrode, an uneven shape is formed by an aggregate of the light scattering particles,
On the second surface facing the translucent substrate, the light scattering particles in a dense state are aligned along a smooth surface as compared with the uneven shape of the first surface.
EL element. The light scattering layer is
2. The EL element according to claim 1, wherein the EL element is bonded to the transparent electrode through a light-transmitting smoothing layer that forms a smooth bonding surface covering the uneven shape on the first surface. . Further comprising a sheet-like base material having translucency, bonded to the surface facing the light scattering layer in the translucent substrate through a bonding layer,
The light scattering particles on the second surface are:
The EL element according to claim 1, wherein the EL element is aligned along a surface opposite to a surface on which the bonding layer is provided in the base material. The light scattering particles on the second surface are:
The EL element according to claim 1, wherein the EL element is aligned along a surface opposite to a surface on which the optical sheet is disposed in the light-transmitting substrate. The light scattering particles of the light scattering layer are:
5. The EL element according to claim 1, wherein the particle density on the second surface is higher than the particle density on the first surface. The light scattering particles of the light scattering layer are:
6. The EL device according to claim 1, wherein an average particle diameter on the second surface is smaller than an average particle diameter on the first surface.   A lighting device comprising the EL element according to claim 1 as a light emitting unit. The EL element according to any one of claims 1 to 6,
The EL light emitting unit of the EL element has a plurality of pixels that can be driven independently. An image display element using liquid crystal;
The EL element according to any one of claims 1 to 6, which is disposed on the back surface of the image display element,
A liquid crystal display device comprising: An image display element using liquid crystal;
The lighting device according to claim 7 disposed on the back surface of the image display element;
A liquid crystal display device comprising:

Images