JP2015149220A - Front plate for el element and lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a front plate for an EL element through which light can be extracted efficiently and in which resistance is reduced.SOLUTION: A front plate 1A for an EL element includes: a translucent substrate 11; a high refractive index layer 12 laminated on one surface 11a of the translucent substrate 11; a transparent anode part 13 laminated on a side of the high refractive index layer 12, the side being opposite to the translucent substrate 11; and an electrically conductive light reflecting layer 14 having conductivity and light reflectivity and laminated on a part of an opposite surface 13a of the transparent anode part 13, the opposite surface being an opposite side to the high refractive index layer 12.

Description

  The present invention relates to an EL element front plate with improved light extraction efficiency, and an illumination device including the EL element front plate.

In recent years, for example, in the case of a lighting device such as a general organic EL (Electro-Luminescence) element (hereinafter also abbreviated as “EL element” or “element”), the light extraction efficiency emitted from the glass substrate to the air Is only 20%. Therefore, in many cases, an external film is attached to the element in consideration of the mass productivity of the panel. Although it depends on the element structure of the panel, even when an external film is attached to the element, the light extraction efficiency is about 25%, and the loss of light is large. This is because the refractive index of the substrate mainly made of glass or plastic is different from that of the organic layer, and the light is totally reflected at the interface.
In order to further improve the light extraction efficiency, it is necessary to provide a light extraction structure inside the device.
For example, Patent Documents 1 and 2 are known as studies on the light extraction efficiency of an illumination device.

JP-A-8-083688 JP 2009-009861 A

  Patent Document 1 is an example in which an external film is pasted on a substrate, and it is possible to suppress total reflection of light at the interface between the substrate and the air layer and to improve light extraction efficiency. However, when light is extracted, the light-scattering film surface and retroreflection on the cathode part such as aluminum or silver are used to extract light to the outside, so that the external extraction efficiency by the light-scattering film increases. On the other hand, there is a problem that light is lost due to absorption of light at the transparent anode part, the light emitting element part, and the cathode during retroreflection. Further, as described above, the external extraction efficiency does not take into account the difference in refractive index between the organic layer and the substrate, and the external extraction efficiency is not sufficient in this respect.

  Patent Document 2 is a method of providing irregularities using a mother die in order to alleviate the refractive index difference between the organic layer and the substrate. However, similarly to Patent Document 1, there is a problem that light is lost due to absorption of light at the transparent anode part, the light emitting element part, and the cathode during retroreflection. In addition, when the concavo-convex shape reaches the organic layer in this manner, there is a drawback that leakage or short-circuit between the anode and the cathode often occurs, resulting in no productivity.

  An organic EL element for display and lighting applications needs to emit transparent light, so that the electrode needs to be transparent. In general, ITO or the like is often used for the transparent electrode, and the resistance value is generally higher than that of normal Al or Ag. Since the resistance value is high, the power supplied from the outside drops when the light emitting area increases. As a result, there is a problem in that unevenness of brightness occurs such that the vicinity of the power supply unit is bright in the light emitting surface and becomes darker as the distance from the power supply unit increases. In this case, as a workaround for the problem, it is common to use an auxiliary electrode having a low resistance value such as Al. However, when the auxiliary electrode is used, the portion does not emit light or is hidden even if it emits light. Therefore, there is a problem that the light emitting area is reduced.

  In general, an organic EL element is formed by laminating a light-transmitting substrate, a high refractive index layer, an EL element front plate having a transparent anode part, and a light emitting part having a cathode. The above-mentioned problems related to the organic EL element are similarly generated in the front panel for EL elements.

  The present invention has been made in order to solve the above-described problems. The front plate for an EL element, which efficiently extracts light and has a low resistance (a low resistance value), and the front of the EL element are provided. It aims at providing an illuminating device provided with a face plate.

In order to solve the above problems, the present invention proposes the following means.
The front plate for an EL element of the present invention includes a translucent substrate, a high refractive index layer laminated on one surface of the translucent substrate, and the opposite side of the high refractive index layer to the translucent substrate. A transparent anode part laminated on, and an electrically conductive light reflecting layer laminated on a part of the opposite surface of the transparent anode part opposite to the high refractive index layer, having conductivity and light reflectivity, It is characterized by having.

In the EL element front plate, the high refractive index layer preferably contains fine particles having light scattering properties.
In the EL element front plate, it is more preferable that a fine uneven shape is provided on the surface of the translucent substrate opposite to the high refractive index layer.
In the EL element front plate, the refractive index of the high refractive index layer is more preferably 1.7 or more.

In the EL element front plate described above, it is more preferable that the light-transmitting substrate contains fine particles having light scattering properties.
In addition, the lighting device of the present invention includes the above-described EL element front plate, the portion on the opposite surface of the transparent anode portion where the electroconductive light reflection layer is not laminated, and the electroconductive light reflection. The light emitting element part laminated | stacked on the opposite side to the said transparent anode part of a layer, The cathode part laminated | stacked on the opposite side to the said electroconductive light reflection layer of the said light emitting element part is provided, It is characterized by the above-mentioned.
Moreover, in the above-described lighting device, it is more preferable to provide an electrical insulating layer so as to cover the electrically conductive light reflecting layer laminated on the transparent anode portion.

  According to the EL element front plate and the lighting device of the present invention, it is possible to efficiently extract light and reduce the resistance.

It is sectional drawing of the side surface of the illuminating device of one Embodiment of this invention. It is a top view explaining arrangement | positioning of the conductive reflection part and opening part of the same illuminating device. It is sectional drawing of the principal part explaining the effect | action of the illuminating device. It is sectional drawing of the principal part explaining the effect | action of the illuminating device. It is sectional drawing of the side surface of the illuminating device of the modification of one Embodiment of this invention. It is a top view explaining arrangement | positioning of the electroconductive reflection part and opening part of the illuminating device of the modification of one Embodiment of this invention. It is a top view explaining arrangement | positioning of the electroconductive reflection part and opening part of the illuminating device of the modification of one Embodiment of this invention. It is sectional drawing of the side surface of the illuminating device of the modification of one Embodiment of this invention. It is sectional drawing of the side surface of the illuminating device in embodiment of the modification of this invention. It is sectional drawing of the side surface of the illuminating device of the Example of this invention. It is a figure which shows the change of the light beam by the refractive index of the translucent board | substrate of the illuminating device.

Hereinafter, an embodiment in which the illumination device according to the present invention is an organic EL element will be described with reference to FIGS. 1 to 8.
As shown in FIG. 1, the illuminating device 1 of the present embodiment includes a translucent substrate 11, a high refractive index layer 12 stacked on one surface 11 a of the translucent substrate 11, and a high refractive index layer 12. The transparent anode part 13 laminated on the opposite side to the translucent substrate 11, and the electrically conductive light reflecting layer 14 laminated on a part of the opposite surface 13a opposite to the high refractive index layer 12 of the transparent anode part 13. And the light emitting element portion 15 laminated on the opposite surface 13a of the transparent anode portion 13 where the electroconductive light reflecting layer 14 is not laminated, and the side opposite to the electroconductive light reflecting layer 14 of the light emitting element portion 15. And a cathode portion 16 laminated on the substrate.
The translucent substrate 11, the high refractive index layer 12, the transparent anode portion 13, and the electrically conductive light reflecting layer 14 constitute the EL element front plate 1 </ b> A of the present invention.

  The translucent substrate 11 is formed in a sheet shape from glass or a plastic material such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate). The thickness of the translucent substrate 11 is, for example, about 0.3 to 3 mm. Generally, if the translucent substrate 11 is thin, it can be bent and used for flexible applications. Moreover, when the translucent board | substrate 11 is thick, it becomes possible to use for the use for which rigidity is required.

For the high refractive index layer 12, for example, an acrylic resin or a urethane resin, and in addition, a hybrid material of an organic substance such as silsesquioxane and an inorganic substance can be used.
The thickness of the high refractive index layer 12 is preferably in the range of 0.5 μm (micrometer) to 100 μm. When fine particles having a light scattering property, which will be described later, are put in the high refractive index layer 12, it is necessary to make the particle diameter of the fine particles smaller than the thickness of the high refractive index layer 12. If the thickness of the high refractive index layer 12 is less than 0.5 μm, the particle size of the fine particles is too small, the light scattering property is weakened, and it does not function as a scattering material.
In addition, when the thickness of the high refractive index layer 12 exceeds 100 μm, the amount of water contained in the material of the high refractive index layer 12 is excessively large and damages the light emitting element portion 15, or has a light scattering property described later. When the fine particles are added, the surface roughness increases and causes leakage. Furthermore, since the high refractive index layer 12 is too thick as a scattering layer, the light transmittance is weak, which is not preferable.
The high refractive index layer 12 preferably has a refractive index equivalent to or higher than that of the light emitting element portion 15. The refractive index of the high refractive index layer 12 is desirably 1.7 or more.
The high refractive index layer 12 is laminated on the entire surface 11 a of the translucent substrate 11.

The transparent anode portion 13 can be formed of a transparent material such as ITO (indium tin oxide). The transparent anode portion 13 is laminated over the entire surface of the high refractive index layer 12 on the side opposite to the light transmissive substrate 11.
The electroconductive light reflection layer 14 is formed of Al (aluminum), Ag (silver), or the like, and is a layer having conductivity that efficiently conducts electricity and light reflectivity that reflects light. The electroconductive light reflection layer 14 can be attached to the transparent anode portion 13 by vapor deposition. In this case, if the thickness is several tens of nanometers (nanometers) or more, light can be reflected. The electroconductive light reflection layer 14 is formed in a rectangular shape when viewed from the side (when viewed in a direction perpendicular to the thickness direction D of the translucent substrate 11).

When viewed in parallel to the thickness direction D, the range in which the electroconductive light reflection layer 14 is laminated becomes a conductive reflection portion R1 that reflects light L2 described later, and the electroconductive light reflection layer 14 is not laminated. The range is the opening R2.
As shown in FIG. 2, each opening R2 is formed in a rectangular shape, and the plurality of openings R2 are arranged in a lattice shape. By configuring each opening R2 of the electroconductive light reflection layer 14 in this way, each of the openings R2 is made inconspicuous, and it appears to be equivalent to surface light emission in the plurality of openings R2 as a whole. Can do.

In the present embodiment, as illustrated in FIG. 1, the lighting device 1 is disposed between the electrically conductive light reflecting layer 14 and the light emitting element portion 15 so as to cover the electrically conductive light reflecting layer 14 laminated on the transparent anode portion 13. Is provided with an electrical insulating layer 17. The electrical insulating layer 17 is a light-shielding layer that does not conduct light, and can be formed of many plastic materials and inorganic materials such as acrylic resin and urethane resin. In order not to conduct electricity (has insulation), the thickness of the electrical insulating layer 17 is preferably about 1 nm to several hundreds of μm.
In this example, the electrically insulating layer 17 is formed on the surface of the electroconductive light reflecting layer 14 opposite to the transparent anode portion 13 and the surface of the electroconductive light reflecting layer 14 adjacent along the opposite surface 13 a of the transparent anode portion 13. They are laminated on the opposite side surfaces 14 a and cover the electrically conductive light reflecting layer 14.
In the case where the electrical insulating layer 17 is laminated, the light emitting element portion 15 is formed by the ink jet printing method using the electrical insulating layer 17 as a barrier, thereby suppressing the waste of the material forming the light emitting element portion 15 and the lighting device 1. Can be manufactured.

The light emitting element portion 15 is laminated on the opposite side of the electrically conductive light reflecting layer 14 from the transparent anode portion 13 via the electrical insulating layer 17, and on the opposite surface 13 a of the transparent anode portion 13, the electrically conductive light. The reflective layer 14 is laminated on a portion where the reflective layer 14 is not laminated.
The light emitting element portion 15 is preferably made of a material that moves charges injected from the electrodes and recombines holes and electrons. Specifically, tris (8-quinolinolato) aluminum complex (Alq3), bis (benzoquinolinolato) beryllium complex (BeBq), tri (dibenzoylmethyl) phenanthroline europium complex (Eu (DBM) 3 (Phen)) Ditoluyl vinyl biphenyl (DTVBi) or the like can be used. Although the thickness of the light emitting element part 15 changes with structures, it is preferable that it is several 100 nm or less.
The light emitting element portion 15 is laminated over the entire surface on the opposite side of the high refractive index layer 12 with respect to the transparent anode portion 13 and the electrical insulating layer 17. A part of the light emitting element portion 15 is in direct contact with the transparent anode portion 13.

The cathode portion 16 is formed of Al, Ag, or the like, like the electrically conductive light reflecting layer 14, and is a layer having conductivity and light reflectivity. The thickness of the cathode portion 16 is preferably several nm to 500 nm.
The cathode portion 16 is laminated over the entire surface on the opposite side of the light emitting element portion 15 from the electrical insulating layer 17.

The electrically conductive light reflecting layer 14 of the lighting device 1 configured as described above can be formed in a predetermined pattern shape by a known method such as vapor deposition or etching.
The translucent substrate 11, the high refractive index layer 12, the transparent anode portion 13, the electrically conductive light reflection layer 14, and the like can be manufactured by a known roll-to-roll method in the same manner as a conventional organic EL element.

In the lighting device 1 configured and manufactured in this way, as shown in FIG. 3, the light L <b> 1 emitted from the light emitting element unit 15 is normally transmitted through the translucent substrate 11 when radiated to the outside. Due to the difference in refractive index between the conductive substrate 11 and air A, total reflection occurs at the interface and the light is reflected as light L2. In this state, the light L2 is not emitted to the outside, and light loss occurs.
However, in the present lighting device 1, the reflected light L2 hits the surface 14b on the transparent anode portion 13 side of the electroconductive light reflecting layer 14 and is reflected to become the light L3. By being reflected, the direction of the light L3 changes with respect to the direction of the light L1, and the light L2 that should have been totally reflected and lost can be extracted from the translucent substrate 11 to the outside.
In order to change the direction of the light L3 with respect to the direction of the light L1, the surface 14b of the electrically conductive light reflecting layer 14 is preferably not flat but rough to some extent. The arithmetic average roughness (Ra) of the surface 14b is preferably 100 μm or more and 500 μm or less, for example.

  When the surface 14b of the electroconductive light reflecting layer 14 is further rough (arithmetic average roughness is large), as shown in FIG. It becomes. In this case, performance equivalent to adding fine particles to the high refractive index layer 12 to have a scattering effect can be provided.

As described above, according to the EL element front plate 1 </ b> A and the illumination device 1 of the present embodiment, since the electroconductive light reflection layer 14 is provided, the light emitted from the light emitting element portion 15 is transmitted through the translucent substrate 11. Even if the light is reflected at the interface between the air A and the air A, the light can be reflected again by the electroconductive light reflection layer 14. Thereby, the light extraction efficiency of the illuminating device 1 can be improved and light can be extracted efficiently.
Since the electrically conductive light reflecting layer 14 is disposed along the opposite surface 13a of the transparent anode portion 13, the illuminating device 1 is placed on the transparent substrate 11 side even though the electrically conductive light reflecting layer 14 itself is not illuminated. When viewed from above, it can appear as if the electrically conductive light reflecting layer 14 is shining.
The illuminating device 1 originally has a structure in which total reflection at the interface between the translucent substrate 11 and the air A is small due to the electrically conductive light reflection layer 14. However, the light that is totally reflected and returns to the element side (the light emitting element part 15 side) is not reflected on the cathode part 16 side of the lighting device 1 but is reflected on the electroconductive light reflection layer 14 as much as possible. Therefore, the probability that the light returned by total reflection is absorbed through the light emitting element portion 15 is low.

When the transparent anode portion 13 is thinned, the resistance value of the transparent anode portion 13 increases, which causes a deterioration in the light emission distribution in the light emitting surface. In order to reduce the resistance value of the transparent anode part 13, it is the simplest method to increase the thickness of the transparent anode part 13, but the light transmittance decreases (light becomes difficult to transmit through the transparent anode part 13). There is a trade-off relationship.
In order to reduce the resistance of the transparent anode portion 13, a method is generally used in which the transparent anode portion 13 is crystallized and annealed by annealing at about 200 ° C. or higher. In that case, the substrate to be heated needs to be able to withstand the temperature. When an organic material is used as the material of the substrate, the material may be deteriorated due to the high temperature.
On the other hand, in the configuration of the lighting device 1, the electrically conductive light reflecting layer 14 used as a light reflecting material also contributes to lowering the resistance of the transparent anode portion 13. There is no need to anneal at high temperatures. Therefore, a general material such as ITO or a relatively high resistance material such as a conductive polymer such as PEdot can be used for the transparent anode portion 13.

As described above, the electrically conductive light reflecting layer 14 not only reflects light but also serves to lower the resistance value of the transparent anode part 13, and the presence of the electrically conductive light reflecting layer 14 reduces the thickness of the transparent anode part 13. It is possible to reduce the absorption of light as much as possible.
In order to reduce the resistance of the transparent anode portion 13, there is a method of providing auxiliary wiring as described in JP-A-2003-316291, for example. However, in a general configuration, the portion where the auxiliary wiring is provided does not emit light, so that a light emitting portion and a non-light emitting portion are formed in the light emitting surface of the lighting device, which is a cause of impairing the product design.

An electrically insulating layer 17 is disposed so as to cover the electrically conductive light reflecting layer 14 laminated on the transparent anode portion 13. Thereby, the light emission which becomes a loss in the electroconductive light reflection layer 14 is eliminated, the patterning of the light emitting element portion 15 is not necessary, and the manufacturing process can be simplified.
When the refractive index of the high refractive index layer 12 is 1.7 or more, the light extraction efficiency can be increased.
The high refractive index layer 12 is directed toward the light emitting element portion 15, that is, the high refractive index layer 12 is provided closer to the light emitting element portion 15 than the translucent substrate 11. Thereby, the surface of the translucent substrate 11 (surface opposite to the high refractive index layer 12) can be flattened, the surface can be easily cleaned, and the design of the lighting device 1 is possible. Can be improved.

  Moreover, since the translucent substrate 11, the high refractive index layer 12, the transparent anode part 13, the electroconductive light reflection layer 14 and the like can be manufactured by the roll-to-roll method as described above, Similarly, the film can be produced by a roll-to-roll method. Therefore, manufacturing a device structure part on a conventional glass substrate, forming a light scattering film on a plastic substrate, and then sticking the light scattering film onto the glass substrate via an adhesive or the like. Compared with the process, there is a possibility that the process is simplified, the manufacturing lead time is increased, and the cost is reduced.

The ratio of the light emitting area to the entire area of the light emitting element portion 15 when viewed in the thickness direction D is defined as an aperture ratio. In this case, if the aperture ratio is large, the in-plane luminance increases, but the luminous efficiency decreases. Conversely, if the aperture ratio is small, the luminous efficiency increases, but the in-plane luminance decreases. Therefore, it is necessary to determine the aperture ratio depending on which of in-plane luminance and light emission efficiency is important.
When the aperture ratio is reduced, the proportion of the electrically conductive light reflecting layer 14 is inevitably increased. However, this causes the heat generated in the light emitting element portion 15 to be transferred, thereby mitigating the temperature rise of the lighting device 1 as a whole. There is an effect to. Thereby, the lifetime of the light emitting element part 15 can be increased (lengthened).
Further, in this structure, the transparent anode portion 13 can be formed without patterning, and the transparent anode portion 13 is flat without uneven portions, so that the surface polishing of the transparent anode portion 13 necessary for the organic EL element is possible. There are benefits.

In the present embodiment, the high refractive index layer 12 may include (enclose) light-scattering fine particles (not shown). With this configuration, when viewed from the outside (from the translucent substrate 11 side), there is an effect of further shielding the electrically conductive light reflecting layer 14, and further, an effect of extracting light from the translucent substrate 11. improves. As the above-mentioned fine particles, TiO ₂ , SiO ₂ , Al ₂ O ₃ , ZrO, CaCO ₃ , BaSO ₄ , Mg ₃ Si ₄ O ₁₀ (OH) ₂ or the like can be used, and the particle diameter of the fine particles is several tens nm. To several hundred μm, etc. The material and particle size of the fine particles are not limited to this.
In this case, the amount of fine particles added to the high refractive index layer 12 is preferably 40 w% or less. When the added amount exceeds 40 w%, the fine particles are aggregated, which is not preferable.
When fine particles are not put into the high refractive index layer 12, irregularities are formed on the interface between the electroconductive light reflecting layer 14 and the transparent anode portion 13, that is, on the surface 14 b of the electroconductive light reflecting layer 14 as described above. There is a method of giving a scattering effect.
When the high refractive index layer 12 contains fine particles, the light is scattered in the high refractive index layer 12 to make the light uniform. Thereby, the light nonuniformity as a surface light source can be reduced, and the angle distribution of light can be made uniform.

You may provide the fine uneven | corrugated shape which is not illustrated in the surface on the opposite side to the high refractive index layer 12 of the translucent board | substrate 11. FIG. Examples of the fine concavo-convex shape include a microlens shape (eg, hemispherical or elliptical sphere) having an outer diameter of about 0.1 μm to 500 μm, a quadrangular pyramid shape, and a shape in which fine particles are scattered. Any shape of the fine uneven shape is intended to change the direction in which light is scattered and to extract the light emitted in the illumination device 1 to the outside of the translucent substrate 11.
By providing the light-transmitting substrate 11 with a fine uneven shape, the light emission angle and the light extraction efficiency can be controlled.

The translucent substrate 11 may include fine particles having light scattering properties. As the fine particles, those configured in the same manner as the fine particles used for the high refractive index layer 12 can be used.
When the translucent substrate 11 contains fine particles, the light distribution characteristic of light can be controlled.

In the present embodiment, the electrically conductive light reflecting layer 14 is formed in a rectangular shape in a side view. However, as shown in FIG. 5, the electrically conductive light reflecting layer 14 may be formed in a tapered shape whose width becomes narrower toward the translucent substrate 11.
The shape of each opening R2 and the arrangement of the plurality of openings R2 may be modified as follows. For example, in the example shown in FIG. 6, each opening R2 is formed in a rectangular shape, and the plurality of openings R2 are arranged in a honeycomb shape (staggered shape). By configuring each opening R2 of the electroconductive light reflection layer 14 in this way, the intervals between the adjacent openings R2 can be made equal, so that the light extraction efficiency can be improved.
In the example shown in FIG. 7, each opening R2 is formed in a circular shape, and the plurality of openings R2 are arranged in a honeycomb shape. By configuring each opening R2 of the electroconductive light reflection layer 14 in this way, the intervals between the adjacent openings R2 can be made more evenly spaced, so that the light extraction efficiency can be further improved.

  Like the illuminating device 2 shown in FIG. 8, in addition to each structure of the illuminating device 1, the semicylindrical lens 21 may be aligned and arrange | positioned on the surface of the translucent board | substrate 11. FIG. With this configuration, the light use efficiency can be increased.

As mentioned above, although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and modifications, combinations, and deletions within a scope that does not depart from the gist of the present invention. Etc. are also included.
For example, although the lighting device 1 includes the electrical insulating layer 17, the lighting device 1 may not include the electrical insulating layer 17. This is because even if configured in this way, the light emitting element unit 15 can emit light by applying a voltage between the transparent anode unit 13 and the cathode unit 16.

Moreover, in the said embodiment, it is comprised so that the anode and cathode which sandwich the light emitting element part 15 in the thickness direction D may be opposite with respect to each structure of the illuminating device 1 like the illuminating device 3 shown in FIG. May be. Specifically, the lighting device 3 includes a transparent cathode portion 26 and an anode portion 27 instead of the transparent anode portion 13 and the cathode portion 16 of the lighting device 1.
The transparent cathode portion 26 is laminated on the opposite side of the high refractive index layer 12 from the translucent substrate 11, similarly to the transparent anode portion 13 of the above embodiment. The transparent cathode part 26 can be formed of the same transparent material as the transparent anode part 13.
In this example, the light emitting element portion 15 is laminated on the opposite side of the electroconductive light reflecting layer 14 from the transparent cathode portion 26.
The anode part 27 is laminated on the side of the light emitting element part 15 opposite to the electrically conductive light reflecting layer 14. The anode part 27 can be formed of the same material as the cathode part 16.
Also with the illuminating device 3 configured in this way, the same effects as those of the illuminating device 1 of the embodiment can be obtained.

(Example)
Hereinafter, the present invention will be described in more detail based on examples of the present invention, but the present invention is not limited to the following examples.

Example 1
The pitch of the light emitting layer of the lighting device (the pitch between adjacent light emitting portions 15a of the light emitting element portion 15 in FIG. 1; only one light emitting portion 15a is shown in FIG. 1) is 200 μm, and the thickness of the high refractive index layer Was 10 μm. ITO was used for a transparent anode part, and it formed into a film with a thickness of 150 nm using well-known sputtering. The high refractive index layer was produced on a 188 μm thick PET film, and the opposite side of the PET film from the high refractive index layer was bonded to the glass surface with a transparent adhesive film as a measure against moisture permeability.

As shown in FIG. 10, in this example, a light-transmitting substrate 31 was configured with a glass substrate 32 and a PET film 33. The refractive index of the high refractive index layer was 1.7, and the thickness of the electrically conductive light reflecting layer was 3 μm. To the high refractive index layer, 20 w% of light-scattering fine particles made of SiO ₂ and having a particle size of 2.0 μm were added.
Aluminum was used as the electrically conductive light reflecting layer and deposited on the high refractive index layer.
In the element structure, α-npd of 70 nm, Alq3 of 60 nm, and Al of a cathode part of 100 nm were formed on ITO as a transparent anode part. Compared with a reference (comparative example) simply produced on glass, an efficiency improvement of about 1.5 times was confirmed.

(Example 2)
Α-npd of 70 nm, Alq3 of 60 nm, and Al of the cathode part of 100 nm were formed on ITO as the transparent anode part. FIG. 11 shows a graph obtained by simulating the light flux of light entering the translucent substrate when the refractive index of the translucent substrate is swung from 1.5 to 2.0.
The graph shows the rate of increase of the luminous flux when the refractive index of the translucent substrate is changed with the refractive index of the translucent substrate being 1.5 as a reference. It can be seen that when the refractive index is 1.7, the luminous flux is extremely increased compared to the case where the refractive index is 1.6. From this, it is understood that the amount of the light beam taken out from the translucent substrate is preferably such that the refractive index of the translucent substrate is 1.7 or more.

1, 2 and 3 Illumination device 1A EL element front plate 11 Translucent substrate 11a One surface 12 High refractive index layer 13 Transparent anode portion 13a Opposite surface 14 Electroconductive light reflection layer 15 Light emitting element portion 16 Cathode portion 17 Electrical insulation Layer 26 Transparent cathode portion 27 Anode portion

Claims (7)

A translucent substrate;
A high refractive index layer laminated on one surface of the translucent substrate;
A transparent anode portion laminated on the opposite side of the high refractive index layer from the translucent substrate;
An electrically conductive light reflecting layer that has electrical conductivity and light reflectivity, and is laminated on a part of the opposite surface of the transparent anode portion opposite to the high refractive index layer;
A front plate for an EL element, comprising:   The front plate for an EL element according to claim 1, wherein the high refractive index layer contains fine particles having light scattering properties.   2. The front plate for an EL element according to claim 1, wherein a fine uneven shape is provided on a surface of the translucent substrate opposite to the high refractive index layer.   The front plate for an EL element according to claim 1, wherein the refractive index of the high refractive index layer is 1.7 or more.   The EL element front plate according to claim 1, wherein the light-transmitting substrate contains light-scattering fine particles. A front plate for an EL device according to claim 1,
A portion of the opposite surface of the transparent anode portion where the electrically conductive light reflecting layer is not laminated, and a light emitting element portion laminated on the opposite side of the electrically conductive light reflecting layer from the transparent anode portion,
A cathode portion laminated on a side opposite to the electrically conductive light reflecting layer of the light emitting element portion;
A lighting device comprising:   The lighting device according to claim 6, further comprising an electrically insulating layer so as to cover the electrically conductive light reflecting layer laminated on the transparent anode portion.

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