WO2015146904A1

WO2015146904A1 - Display device

Info

Publication number: WO2015146904A1
Application number: PCT/JP2015/058726
Authority: WO
Inventors: 慶成岩浪; 順也福田
Original assignee: 株式会社オルタステクノロジー
Priority date: 2014-03-27
Filing date: 2015-03-23
Publication date: 2015-10-01
Also published as: JP2015191708A; JP6342191B2

Abstract

The display device (10) comprises: a transparent light-emitting element (12) emitting light having a first wavelength region; and a dielectric layer (21) whereby light having a second wavelength region containing at least a portion of the first wavelength region is reflected to an observer side and light outside of the second wavelength region among an external light is transmitted.

Description

Display device

The present invention relates to a display device, and more particularly to a self-luminous display device using a light emitting element.

In recent years, an organic EL display device using an organic electroluminescence element (organic EL element) is known as a display device that replaces a liquid crystal display device. The organic EL display device is a self-luminous type and has characteristics such as high contrast, a large viewing angle, and a high response speed.

In general organic EL display devices, the light emission luminance on the viewing side is enhanced by using a metal that reflects light, such as an aluminum alloy, as the cathode of the organic EL element. However, an organic EL display device using such a reflective film cannot be used for a device that needs to transmit light.

On the other hand, a transmissive organic EL display device can be constructed by using transparent conductive films for the anode and the cathode, respectively. However, in this transmissive organic EL display device, light is transmitted also in the direction opposite to the viewing side, so that the light emission luminance is reduced as compared with the case where total reflection is performed using a reflective film.

JP 2007-333767 A JP 2013-2111169 A

The present invention provides a display device capable of improving light emission luminance while suppressing a decrease in transmittance.

A display device according to one embodiment of the present invention includes a transmissive light-emitting element that emits light having a first wavelength region, and light having a second wavelength region including at least part of the first wavelength region on the viewer side. And a dielectric layer that transmits light outside the second wavelength region out of the external light.

According to the present invention, it is possible to provide a display device capable of improving the light emission luminance while suppressing a decrease in transmittance.

1 is a cross-sectional view of an organic EL display device according to a first embodiment. The graph which shows the relationship between the wavelength of the light which a light emitting element radiates | emits, and radiance. The graph explaining the reflectance of a transparent dielectric material layer. Sectional drawing of the transparent dielectric material layer which has the reflective characteristic of 1st Example. The figure explaining an example of the material of the multilayer film which comprises a transparent dielectric material layer. The top view of an organic electroluminescence display. FIG. 7 is a cross-sectional view of the organic EL display device along line A-A ′ shown in FIG. 6. Sectional drawing of the organic electroluminescence display which concerns on 2nd Embodiment. Sectional drawing which shows the specific structure of the organic electroluminescence display which concerns on 2nd Embodiment. Sectional drawing of the organic electroluminescence display which concerns on 3rd Embodiment.

Hereinafter, embodiments will be described with reference to the drawings. However, it should be noted that the drawings are schematic or conceptual, and the dimensions and ratios of the drawings are not necessarily the same as the actual ones. Further, even when the same portion is represented between the drawings, the dimensional relationship and ratio may be represented differently. In particular, the following embodiments exemplify an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention depends on the shape, structure, arrangement, etc. of components. Is not specified. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

[First Embodiment]
[1. Basic configuration of organic EL display device]
In the present embodiment, a display device (organic EL display device) using an organic EL element as a light emitting element will be described as an example. In the present embodiment, an organic EL display device having a bottom emission structure in which light is extracted from a substrate side on which a light emitting element is formed will be described as an example.

FIG. 1 is a cross-sectional view of an organic EL display device 10 according to the first embodiment of the present invention. The substrate 11 is composed of a transparent substrate, and for example, a glass substrate or a plastic substrate is used. A light emitting element 12 made of an organic EL element is provided on the substrate 11. The organic EL element of this embodiment is a transmissive organic EL element.

The light emitting element 12 is configured by laminating a lower electrode 13, an organic layer 14, and an upper electrode 15 in this order. The organic layer 14 is configured by laminating a hole transport layer 16, a light emitting layer 17, and an electron transport layer 18 in this order. The lower electrode 13 functions as an anode, is composed of a transparent electrode, and for example, a conductive metal oxide is used. Examples of the transparent and conductive metal oxide include ITO (indium tin oxide) and IZO (indium zinc oxide). The upper electrode 15 functions as a cathode and is composed of a transparent electrode. For example, a conductive metal oxide (such as ITO or IZO) is used.

The hole transport layer 16, the light emitting layer 17, and the electron transport layer 18 are each composed of an organic material, and these specific organic materials can be selected from known materials. The hole transport layer 16 has a function of transporting holes injected from the interface with the lower electrode 13 to the light emitting layer 17. The electron transport layer 18 has a function of transporting electrons injected from the interface with the upper electrode 15 to the light emitting layer 17. The light emitting layer 17 has a function of emitting light by recombining holes transported from the hole transport layer 16 and electrons transported from the electron transport layer 18.

The organic layer 14 is not limited to the three-layer structure described above, and a five-layer structure or the like may be used. That is, the hole transport layer 16 may be constituted by two layers by functionally dividing into a hole injection layer and a hole transport layer from the lower electrode 13 side. Similarly, the electron transport layer 18 may be divided into two layers, functionally divided into an electron injection layer and an electron transport layer from the upper electrode 15 side.

A substrate 20 is provided above the light emitting element 12 via a sealing layer 19. The sealing layer 19 is composed of, for example, an air layer sealed by an adhesive member (not shown) that bonds the substrate 11 and the substrate 20 together. The sealing layer 19 has a function of preventing moisture from entering the organic layer 14 from the outside. The refractive index of the sealing layer 19 is set to be different from the refractive index of the transparent dielectric layer 21 described later. The sealing layer 19 may use an insulating resin made of, for example, an ultraviolet (UV) curable resin or a thermosetting resin. When an insulating resin is used as the sealing layer 19, the sealing layer 19 further has a function of bonding the substrate 11 and the substrate 20 and a function of increasing the mechanical strength of the organic EL display device 10. Even when the sealing layer 19 is configured using an insulating resin, the refractive index of the sealing layer 19 is set to be different from the refractive index of the transparent dielectric layer 21 described later.

The substrate 20 is composed of a transparent substrate, and for example, a glass substrate or a plastic substrate is used. A transparent dielectric layer 21 is provided on the light emitting element 12 side of the substrate 20. The transparent dielectric layer 21 has a function of substantially completely reflecting light having a specific wavelength region and transmitting light having other wavelength regions. That is, the transparent dielectric layer 21 is light transmissive.

In the present embodiment, as an example, the organic EL display device 10 displays a red character. Therefore, the light emitting element 12 emits red light. FIG. 2 is a graph showing the relationship between the wavelength of light emitted from the light emitting element 12 and the radiance. The vertical axis represents radiance (arbitrary unit), and the horizontal axis represents wavelength (nm). The light-emitting element 12 emits light having a long wavelength from around 600 nm and emits light having a radiance peak around 630 nm.

(Configuration of transparent dielectric layer 21)
FIG. 3 is a graph for explaining the reflectance of the transparent dielectric layer 21. The vertical axis in FIG. 3 indicates the reflectance of the transparent dielectric layer 21, and the horizontal axis indicates the wavelength (nm) of incident light on the transparent dielectric layer 21. FIG. 3 shows graphs of three cases (first to third embodiments) having different reflectivities.

The transparent dielectric layer 21 according to the first embodiment almost completely reflects light having a wavelength of 610 nm or more and transmits light in other wavelength regions. FIG. 4 is a cross-sectional view of the transparent dielectric layer 21 having the reflection characteristics of the first embodiment. FIG. 5 is a view for explaining an example of the material of the multilayer film constituting the transparent dielectric layer 21.

The transparent dielectric layer 21 is configured by alternately laminating a first dielectric film having a relatively high refractive index and a second dielectric film having a low refractive index. The first and second dielectric films constituting the transparent dielectric layer 21 are each composed of a transparent dielectric film.

4 and FIG. 5, the transparent dielectric layer 21 is composed of a dielectric multilayer film (laminated film) in which 32 dielectric films are laminated. Specifically, the transparent dielectric layer 21 has, for example, a titanium oxide film (TiO ₂ ) as the first dielectric film and a silicon oxide film (SiO ₂ ) as the second dielectric film, which are alternately stacked in 32 layers. Configured. The refractive index (about 1.45) of the silicon oxide film is smaller than the refractive index (about 2.30) of the titanium oxide film. Further, the thickness of each layer is set so that the plurality of first dielectric films and the plurality of second dielectric films have desired reflection characteristics. When a titanium oxide film is used as the first dielectric film and a silicon oxide film is used as the second dielectric film, an example of the thickness of each layer is as shown in FIG. The film thickness of each layer constituting the transparent dielectric layer 21 is set in the range of 10 nm to 140 nm.

The transparent dielectric layer 21 configured in this way can almost completely reflect light having a wavelength of 610 nm or more out of light emitted from the light emitting element 12 and transmit light in other wavelength regions. As shown in FIG. 1, the observer 22 can visually recognize light directly reaching from the light emitting layer 17 and light reflected by the transparent dielectric layer 21 among the light emitted from the light emitting layer 17. In addition, light having a wavelength of less than 610 nm among external light incident from the substrate 20 side passes through the transparent dielectric layer 21 and is visually recognized by the observer 22. The external light corresponds to light from a background (subject) that the viewer 22 visually recognizes through the transmissive organic EL display device 10. For example, when the organic EL display device 10 is used as a camera finder, external light corresponds to light from the background incident on the finder via the camera lens. The observer 22 visually recognizes the character displayed by the organic EL display device 10 on the background as external light.

Further, the transparent dielectric layer 21 having a lower reflectance than that of the first embodiment (with a reflectance of about 99%) may be used. In FIG. 3, the transparent dielectric layer according to the second embodiment is formed by alternately stacking nine layers of titanium oxide films (TiO ₂ ) and silicon oxide films (SiO ₂ ). The transparent dielectric layer according to the third embodiment is formed by alternately stacking seven layers of titanium oxide films (TiO ₂ ) and silicon oxide films (SiO ₂ ). The transparent dielectric layer of the second embodiment has a reflectance of about 68% for light with a wavelength of 630 nm. The transparent dielectric layer of the third embodiment has a reflectance of about 54% for light with a wavelength of 630 nm. The reflectance of the transparent dielectric layer 21 with respect to light having a wavelength corresponding to the radiance peak of the light emitting element 12 is set in a range of 10% to 100%.

As described above, in this embodiment, by using the transparent dielectric layer 21, the light emitted from the light emitting element 12 in the direction opposite to the observer 22 can be reflected to the observer 22 side. Thereby, even when the power consumption of the light emitting element 12 is reduced, the light emission luminance of the organic EL display device 10 can be improved.

[2. Specific configuration example of organic EL display device]
Next, a specific configuration example of the organic EL display device 10 will be described. In the present embodiment, a pattern display type organic EL display device that displays a plurality of characters having a predetermined shape such as characters and figures will be described as an example. FIG. 6 is a plan view of the organic EL display device 10. FIG. 7 is a cross-sectional view of the organic EL display device 10 taken along line AA ′ shown in FIG.

The substrate 11 and the substrate 20 are bonded by an adhesive 23. The light emitting element formed on the substrate 11 is sealed with the adhesive 23 and the substrate 20. The adhesive 23 is formed so as to surround a display area (active area) AA on which an image (character) is displayed. Specifically, the adhesive (sealing member) 23 is provided in contact with the partition wall 33 provided on the substrate 11 and the transparent dielectric layer 21 provided on the substrate 20. The sealing layer 19 is sealed between. When the partition wall 33 is not formed up to the end of the active area AA, the adhesive material 23 may be formed so as to be in contact with the insulating film 31. Similarly, when the transparent dielectric layer 21 is not formed up to the end of the active area AA, the adhesive 23 may be formed so as to be in contact with the substrate 20. The adhesive 23 is made of resin, for example.

In the peripheral area PA other than the active area AA in the substrate 11, an LSI (large-scale-integrated) circuit 24 is provided. The LSI circuit 24 includes a driver that drives the light emitting element, a control circuit that controls the driver, and the like. A flexible printed circuit board (FPC: flexible printed circuit) 25 is electrically connected to the LSI circuit 24 via a plurality of terminals. The flexible printed board 25 includes a signal line for sending various signals to the LSI circuit 24 and a power line for supplying power to the LSI circuit 24. The flexible printed circuit board 25 is a flexible circuit board in which, for example, wiring is formed on a polyimide film base material. The flexible printed circuit board 25 is electrically connected to an external device (external circuit) through a plurality of terminals.

The organic EL display device 10 displays characters in the active area AA by receiving control signals including power and image signals from an external device via the flexible printed circuit board 25.

FIG. 6 shows an example of characters that can be displayed by the organic EL display device 10. The organic EL display device 10 can be applied to a camera finder, for example. A character (light emitting area) CR1 that can be displayed by the organic EL display device 10 represents a focus point (rectangle) to be displayed on a camera finder or the like, and a character (light emitting area) CR2 has a frame indicating a focus point area. Represents. Characters CR <b> 1 and CR <b> 2 correspond to a region (light emitting region) emitted by the light emitting element 12.

In FIG. 7, the wiring electrode 30 is provided on the substrate 11. The wiring electrode 30 is electrically connected to the LSI circuit 24. An insulating film 31 is provided on the wiring electrode 30. On the insulating film 31, the light emitting element 12 is provided. The light emitting element 12 is configured by laminating a lower electrode (anode) 13, an organic layer 14, and an upper electrode (cathode) 15 in this order. The organic layer 14 is configured by laminating a hole transport layer 16, a light emitting layer 17, and an electron transport layer 18 in this order. The lower electrode 13 is electrically connected to the wiring electrode 30 via the contact plug 32.

A partition wall 33 is provided between adjacent light emitting regions. The partition wall 33 has a function of ensuring insulation between the lower electrode 13 and the upper electrode 15. As described above, the plurality of light emitting elements 12 are partitioned by the partition walls 33, so that the light emitting elements 12 are formed in regions where the partition walls 33 are not formed. Specifically, the lower electrode 13 is formed in the light emitting region where the light emitting element 12 is formed, and the opening for exposing the lower electrode 13 is formed in the partition wall 33. The organic layer 14 and the upper electrode 15 are stacked on the opening of the partition wall 33 and on the lower electrode 13. On the other hand, since the lower electrode 13 is not formed under the organic layer 14 in the non-light emitting region other than the light emitting region, no light emission occurs.

A substrate 20 is provided above the upper electrode 15 via a sealing layer 19. As described above, the transparent dielectric layer 21 that reflects light having a specific wavelength region emitted from the light emitting element 12 is provided on the light emitting element 12 side of the substrate 20.

As the insulating film 31 and the partition wall 33, a transparent insulating material is used. For example, an organic material such as an acrylic resin, a polyimide resin, or an epoxy resin, or an inorganic material such as SiO ₂ is used. As the wiring electrode 30 and the contact plug 32, a transparent conductive material is used, for example, ITO or IZO.

[3. effect]
As described above in detail, in the first embodiment, the organic EL display device 10 is provided on the transmissive light emitting element 12 provided on the substrate 11 and the substrate 20 facing the substrate 11 with the light emitting element 12 interposed therebetween. And a transparent dielectric layer 21. The light emitting element 12 is composed of an organic EL element, and emits light having a first wavelength region that is, for example, monochromatic light. The transparent dielectric layer 21 reflects light having the second wavelength region including at least a part of the first wavelength region toward the viewer 22 and transmits light outside the second wavelength region out of the external light. To do.

Therefore, according to the first embodiment, the light emitted from the light emitting element 12 in the direction opposite to the observer 22 can be reflected to the observer 22 side by the transparent dielectric layer 21. Thereby, even when the power consumption of the light emitting element 12 is reduced, the light emission luminance of the organic EL display device 10 can be improved.

Further, the transparent dielectric layer 21 can transmit external light. Thereby, a transmissive organic EL display device can be realized. In addition, the light emission luminance of the organic EL display device 10 can be improved while suppressing a decrease in the transmittance of the organic EL display device 10.

[Second Embodiment]
In the second embodiment, the transparent dielectric layer 21 is disposed on the opposite side to the first embodiment with respect to the substrate 20.

FIG. 8 is a cross-sectional view of the organic EL display device 10 according to the second embodiment of the present invention. The configuration of the light emitting element 12 provided on the substrate 11 is the same as that of the first embodiment. A transparent dielectric layer 21 is provided on the opposite side of the substrate 20 from the light emitting element 12. The configuration and characteristics of the transparent dielectric layer 21 are the same as those in the first embodiment.

FIG. 9 is a cross-sectional view showing a specific configuration of the organic EL display device 10 according to the second embodiment. The plan view of the organic EL display device 10 is the same as FIG.

Also in the second embodiment, as in the first embodiment, the light emission luminance of the organic EL display device 10 can be improved while suppressing a decrease in the transmittance of the organic EL display device 10.

[Third Embodiment]
In the third embodiment, the transparent dielectric layer 21 is arranged on the substrate 11 on which the light emitting element 12 is formed. That is, the third embodiment is a configuration example of an organic EL display device having a top emission structure in which light is extracted from the substrate 20 side for sealing the light emitting element 12.

FIG. 10 is a cross-sectional view of an organic EL display device 10 according to the third embodiment of the present invention. The configuration of the light emitting element 12 provided on the substrate 11 is the same as that of the first embodiment. The substrate 20 is bonded to the substrate 11 with an adhesive 23 and seals the light emitting element 12 through the sealing layer 19.

The transparent dielectric layer 21 is provided on the opposite side of the substrate 11 from the light emitting element 12. The refractive index of the substrate 11 is set to be different from the refractive index of the transparent dielectric layer 21. The configuration and characteristics of the transparent dielectric layer 21 are the same as those in the first embodiment. The observer 22 observes the organic EL display device 10 from the substrate 20 side. External light enters the organic EL display device 10 from the substrate 11 side. Of the light emitted from the light emitting layer 17, the light incident on the substrate 11 is reflected by the transparent dielectric layer 21 toward the viewer 22.

Also in the third embodiment, similarly to the first embodiment, it is possible to improve the light emission luminance of the organic EL display device 10 while suppressing a decrease in the transmittance of the organic EL display device 10.

In each of the above embodiments, the light emitting element 12 that emits red light having a radiance peak in the vicinity of a wavelength of 630 nm has been described as an example. However, the present invention is not limited to this, and a color other than red light may be used. Of course, the present invention can also be applied to a light emitting element that emits light. In this case, the transparent dielectric layer 21 is configured to reflect at least a part of the wavelength region of monochromatic light emitted from the light emitting element.

In each of the above embodiments, a display device using an organic EL element as a light emitting element is described as an example. However, the present invention is not limited to this, and a light emitting element other than the organic EL element (for example, an LED) Etc.) can also be applied.

Further, in each of the above embodiments, a configuration example in which the organic EL display device 10 is applied to a camera finder is shown. However, the present invention is not limited to this, and the display device of this embodiment can be applied to various electronic devices that are used to display different images on the subject, background, and image.

The present invention is not limited to the embodiment described above, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Further, the above embodiments include inventions at various stages, and are obtained by appropriately combining a plurality of constituent elements disclosed in one embodiment or by appropriately combining constituent elements disclosed in different embodiments. Various inventions can be configured. For example, even if some constituent elements are deleted from all the constituent elements disclosed in the embodiments, the problems to be solved by the invention can be solved and the effects of the invention can be obtained. Embodiments made can be extracted as inventions.

DESCRIPTION OF SYMBOLS 10 ... Organic

EL display device

11, 20 ... Substrate, 12 ... Light emitting element, 13 ... Lower electrode, 14 ... Organic layer, 15 ... Upper electrode, 16 ... Hole transport layer, 17 ... Light emitting layer, 18 ... Electron transport layer , 19 ... sealing layer, 21 ... transparent dielectric layer, 22 ... observer, 23 ... adhesive, 24 ... LSI circuit, 25 ... flexible printed circuit board, 30 ... wiring electrode, 31 ... insulating film, 32 ... contact plug, 33 ... partition wall.

Claims

A transmissive light emitting element that emits light having a first wavelength region;
A dielectric layer that reflects light having a second wavelength region including at least a part of the first wavelength region to the viewer side and transmits light outside the second wavelength region of external light; and
A display device comprising:
A first substrate provided with the light emitting element;
A second substrate facing the first substrate across the light emitting element and provided with the dielectric layer;
The display device according to claim 1, further comprising:
The display device according to claim 2, further comprising a sealing layer provided between the first substrate and the second substrate.
The display device according to claim 2, further comprising a sealing member that seals a space between the first substrate and the second substrate.
The display device according to claim 3, wherein the sealing layer is an air layer.
A first substrate having a first main surface on which the light emitting element is provided and a second main surface on which the dielectric layer is provided;
A second substrate facing the first substrate across the light emitting element;
The display device according to claim 1, further comprising:
The display device according to claim 6, further comprising a sealing layer provided between the first substrate and the second substrate.
The display device according to claim 6, further comprising a sealing member that seals a space between the first substrate and the second substrate.
The display device according to claim 7, wherein the sealing layer is an air layer.
2. The display device according to claim 1, wherein the light emitting element includes a first transparent electrode and a second transparent electrode, and an organic layer sandwiched between the first and second transparent electrodes and including a light emitting layer.
The display device according to claim 10, wherein each of the first and second transparent electrodes is made of a conductive metal oxide.
The display device according to claim 1, wherein the reflectance of the dielectric layer in light having a wavelength corresponding to a peak of radiance of the light emitting element is set in a range of 10% to 100%.
The dielectric layer includes a plurality of first dielectric films having a first refractive index and a plurality of second dielectric films having a second refractive index lower than the first refractive index. The display device according to claim 1.
The display device according to claim 1, wherein the light emitting element emits monochromatic light.