JP2007141728A - Double-side display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve life characteristic and image visibility of a light transmissive double-side light emission type organic EL display device. <P>SOLUTION: The double-side light emission type organic EL display device is provided with a transparent substrate SUB1, a light transmissive electrode E1 arranged on the substrate SUB1, a light transmissive electrode E2 facing the electrode E1, and an active layer ACT that is interposed between the electrodes E1, E2 and includes the light emitting layer EMT, while it is equipped with an organic EL element OLED that constitutes at least a part of a light resonator in which the light emitted by the light emitting layer EMT is repeatedly reflected and interfered, and a light scattering layer DF which is arranged between the substrate SUB1 and the organic EL element OLED, or on the organic EL element OLED. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a double-sided light emitting organic electroluminescence (EL) display device and a building member using the same.

  Patent Document 1 discloses a first and second transparent electrodes, a light-shielding intermediate electrode interposed therebetween, a first active layer interposed between the first transparent electrode and the intermediate electrode, and a second transparent electrode. A double-sided organic EL display device including a second active layer interposed between an electrode and an intermediate electrode is described. This display device can display separate images on the front surface and the back surface. However, this display device has a complicated structure and is difficult to manufacture.

  An organic EL element including a pair of transparent electrodes and an active layer interposed therebetween emits light on both sides thereof. A double-sided light emitting organic EL display device in which this organic EL element is arranged on a transparent substrate has a structure in which an image displayed on one surface and an image displayed on the other surface are in a mirror image relationship. Simple and easy to manufacture. Further, this display device is light-transmitting because it does not require a light-shielding intermediate electrode. Therefore, such a display device can provide an aesthetic image to an indoor customer and an outdoor passer-by at the same time without blocking the invasion of sunlight indoors, for example, when used for a display window. .

However, the present inventor has found that the double-sided light emitting organic EL display device has insufficient image visibility and life characteristics in making the present invention.
JP 2005-267926 A

  An object of the present invention is to improve the life characteristics and image visibility of a light-transmitting double-sided light emitting organic EL display device.

  According to a first aspect of the present invention, a transparent substrate, a light transmissive first electrode disposed on the transparent substrate, a light transmissive second electrode facing the first electrode, the first and An organic EL device comprising an active layer interposed between the second electrodes and including a light-emitting layer, and constituting at least a part of an optical resonator in which light emitted from the light-emitting layer repeatedly reflects and interferes; and the transparent substrate, A double-sided organic EL display device comprising a light scattering layer disposed between or on the organic EL elements is provided.

  According to the second aspect of the present invention, there is provided a building member comprising the organic EL display device according to the first aspect and a support that supports the organic EL display device.

  According to the present invention, it is possible to improve the life characteristics and image visibility of a light-transmitting double-sided light emitting organic EL display device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

FIG. 1 is a cross-sectional view schematically showing a double-sided light emitting organic EL display device according to one embodiment of the present invention.
This organic EL display device includes a light transmissive display panel DP.

  The display panel DP includes transparent substrates SUB1 and SUB2. The substrates SUB1 and SUB2 face each other with a certain gap. As the substrates SUB1 and SUB2, for example, a glass substrate or a polycarbonate substrate can be used.

  A frame-shaped seal layer SS is interposed between the substrates SUB1 and SUB2, and a sealed space is formed between them. This sealed space is, for example, a vacuum.

  A light scattering layer DF is formed on the surface of the substrate SUB1 facing the substrate SUB2. The light scattering layer DF includes, for example, a light transmissive resin layer RL and a plurality of particles PTC dispersed therein. The particle PTC is light transmissive and typically has a higher refractive index than the resin layer RL. As a material of the resin layer RL, for example, an acrylic resin can be used. As a material of the particle PTC, for example, an inorganic substance such as titanium oxide can be used.

  When the flatness of the surface of the light scattering layer DF is insufficient, the surface may be covered with a flattening layer. However, this flattening layer is made thinner than the maximum value of the evanescent wave seepage depth described later. As the material for the planarization layer, for example, those exemplified as the material for the resin layer RL can be used.

  An organic EL element OLED is formed on the light scattering layer DF. The organic EL element OLED may be interposed between the substrate SUB1 and the light scattering layer DF.

  The organic EL element OLED includes a light transmissive first electrode E1, a light transmissive second electrode E2 facing the first electrode E1, and an active layer ACT interposed between the electrodes E1 and E2. The active layer ACT is light transmissive and includes a light emitting layer EMT. In this example, the active layer ACT further includes a hole injection layer HIL, a hole transport layer HTL, a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL.

  The organic EL element OLED constitutes at least a part of an optical resonator in which light emitted from the light emitting layer EMT is repeatedly reflected and interfered. For example, when the resin layer RL has a smaller refractive index than the electrode E1 and the region adjacent to the organic EL element OLED and the substrate SUB2 side has a smaller refractive index than the electrode E2, the organic EL element OLED Constitutes the entire optical resonator.

  The display panel DP may be capable of changing the display image, or may not be able to change the display image. When the display image can be changed, for example, a driving method such as an active matrix driving method, a passive matrix driving method, or a segment driving method can be used.

  For example, when the display panel DP employs an active matrix driving method, a plurality of pixels each including a pixel circuit and the organic EL element OLED are arranged in a matrix on the substrate SUB1. In this case, video signal lines, scanning signal lines, power supply lines, and the like are further arranged on the substrate SUB1. In each pixel, the pixel circuit and the organic EL element OLED are connected in series in this order between the power supply line and the power supply terminal.

  The video signal lines are arranged corresponding to the pixel columns, and the scanning signal lines are arranged corresponding to the pixel rows. The video signal line is connected to the video signal line driver, and the scanning signal line is connected to the scanning signal line driver. The video signal line driver and the scanning signal line driver are connected to a controller that controls their operations.

  For example, the scanning signal line driver sequentially selects pixels for each row. The scanning signal line driver supplies, to the selected pixel, a first scanning signal that electrically separates the pixel circuit and the organic EL element OLED from each other, for example, via the first scanning signal line. A second scanning signal for electrically connecting the video signal line and the pixel circuit to each other is supplied via the second scanning signal line within a period during which the scanning signal is supplied.

  The video signal line driver outputs a video signal to the video signal line. A video signal is written into the selected pixel within a period during which the second scanning signal is supplied to the pixel circuit. The pixel circuit holds this video signal from the end of the supply of the second scanning signal until the next second scanning signal is supplied, and after the supply of the first scanning signal ends, the next first scanning signal Is supplied to the organic EL element OLED with a magnitude corresponding to the previous video signal.

FIG. 2 is a diagram schematically showing an example in which the display device of FIG. 1 is applied to a building.
FIG. 2 shows a building BLD used as a sales office, for example. A lighting device LM is arranged inside the building BLD, and a window W is fitted as an architectural member in an opening provided in the wall portion.

The window W includes a window plate WP and a window frame WF.
Window plate WP includes display panel DP of FIG. The window plate WP may further include a protective plate, an ultraviolet blocking layer, an antireflection layer, and the like.
The window frame WF supports the peripheral edge of the window plate WP. The window frame WF has a built-in controller connected to the display panel DP.

  The display panel DP included in the window plate WP is light transmissive. Therefore, for example, light emitted from an outdoor light source such as the solar SN can be taken indoors through the window plate WP. Moreover, the outdoor passerby PSR can confirm that the customer CTR is present indoors by looking through the window panel WP.

  Further, the display panel DP of the window plate WP includes a light scattering layer DF. Therefore, as will be described below, the window plate WP has higher visibility of the image on the display panel DP than the case where the light scattering layer DF is omitted.

  During the day, outdoors are usually brighter than indoors. Therefore, when the display panel DP does not include the light scattering layer DF, even if an outdoor passerby PSR looks at the window plate, an indoor object is not clearly seen. Therefore, in this case, the visual recognition of the image on the display panel DP is hardly hindered by the transparent image.

  On the other hand, the indoor customer CTR can clearly see an outdoor object when the display panel DP does not include the light scattering layer DF. For this reason, the see-through image significantly reduces the visibility of the image on the display panel DP.

  Also, after sunset, indoors are usually brighter than outdoors. Therefore, when the display panel DP does not include the light scattering layer DF, an outdoor object is not clearly seen even when the indoor customer CTR looks at the window plate. Therefore, in this case, the visual recognition of the image on the display panel DP is hardly hindered by the transparent image.

  On the other hand, an outdoor passerby PSR can clearly see an indoor object when the display panel DP does not include the light scattering layer DF. For this reason, the see-through image significantly reduces the visibility of the image on the display panel DP.

  As described above, the display panel DP of FIG. 1 includes the light scattering layer DF. Therefore, the transmitted image does not look clear in any environment. That is, an image that shows through does not significantly reduce the visibility of the image on the display panel DP. Therefore, according to this aspect, excellent image visibility can be realized.

  In the display panel DP, as described above, the organic EL element OLED constitutes at least a part of the optical resonator. Since the optical resonator intensifies the light having the resonance wavelength, for example, if the optical resonator is designed so that the wavelength of the light component having the maximum intensity out of the light emitted from the light emitting layer EMT becomes the resonance wavelength, the light flows through the organic EL element OLED Even when the current density is small, high luminance can be realized.

  The organic EL element OLED is more likely to deteriorate as the voltage applied between the electrodes E1 and E2 increases. Therefore, it is considered that excellent life characteristics can be realized by adopting the above design. However, this alone may not achieve excellent life characteristics.

  For example, when the particle PTC is omitted from the display panel DP of FIG. 1, when light enters the interface between the electrode E1 and the resin layer RL with an incident angle larger than the critical angle, the resin emits resin. An evanescent wave that is near-field light is generated in the layer RL. Usually, since the resin layer RL is thicker than the maximum value of the penetration depth of the evanescent wave, the previous evanescent wave is converted into propagating light at the interface. That is, conversion from propagating light to evanescent waves and reverse conversion occur at the same interface. In other words, of the light emitted from the light emitting layer EMT, the light incident on the interface between the electrode E1 and the resin layer RL at an incident angle larger than the critical angle is totally reflected at the previous interface. Therefore, this light cannot be used for display. The “evanescent wave seepage depth” means a depth at which the energy of the evanescent wave is reduced to 1 / e when the energy of the evanescent wave at the interface is 1.

  In the display panel DP of FIG. 1, particles PTC having a higher refractive index are dispersed in the resin layer RL. In such a configuration, the distance from the electrode E1 to the interface between the resin layer RL and the particle PTC is shorter than the maximum value of the penetration depth of the previous evanescent wave. Therefore, the previous evanescent wave is converted into propagating light at the interface between the resin layer RL and the particles PTC. That is, “photon tunneling” in which light tunnels through a portion sandwiched between the electrode E1 and the particle PTC can be generated. Therefore, when the particles PTC are dispersed in the resin layer RL, more light can be emitted from the substrate SUB1 side as compared with the case where the particles PTC are omitted.

  Further, in the light scattering layer DF, the propagating light is refracted and / or reflected at the interface between the resin layer RL and the particles PTC, and changes its traveling direction. Therefore, part of the light returning from the light scattering layer DF to the organic EL element OLED is incident on the interface between the electrode adjacent to the region adjacent to the organic EL element OLED and the substrate SUB2 and the electrode E2 at an angle smaller than the critical angle. . Therefore, when the particles PTC are dispersed in the resin layer RL, more light can be emitted from the substrate SUB2 side than when the particles PTC are omitted.

  That is, more light can be emitted to both the substrate SUB1 side and the substrate SUB2 side. Therefore, according to this aspect, excellent life characteristics can be realized.

  Moreover, the reflection layer made of a metal or an alloy has a relatively large light absorption rate. Therefore, when the optical resonator includes such a reflective layer, the light intensity is greatly reduced due to repeated reflection.

  On the other hand, in the display panel DP of FIG. 1, the optical resonator does not include a reflective layer made of a metal or an alloy. Therefore, this optical resonator has a much smaller decrease in light intensity due to repeated reflection than an optical resonator including a reflective layer made of metal or alloy.

  Therefore, according to this aspect, more light can be emitted to both the substrate SUB1 side and the substrate SUB2 side than when a metal or an alloy is used for the reflection layer of the optical resonator. Therefore, according to this aspect, excellent life characteristics can be realized.

Below, an example of the effect at the time of employ | adopting the structure of FIG. 1 is shown.
Here, ITO was used as the material for the electrodes E1 and E2, and a laminate of a lithium fluoride layer and a magnesium-silver alloy layer was used as the electron injection layer EIL. The thickness of the magnesium-silver alloy layer was set to 20 nm or less in order to achieve sufficient light transmittance. The light scattering layer DF was formed by applying a liquid obtained by dispersing titanium dioxide particles (refractive index of 2.7) having an average particle diameter of 300 nm in an acrylic resin on the substrate SUB1. The thickness of the light scattering layer DF was 1 μm. In this display panel DP, 10% of the light totally reflected in the optical resonator of the display panel having the same structure except that the titanium dioxide particles are omitted can be emitted to the outside of the optical resonator. .

  The density of the particles PTC in the light scattering layer DF is, for example, 5% by volume or more. When this density is small, the effect of emitting more light from the display panel DP, that is, the effect of increasing the light extraction efficiency may be insufficient.

  The density of the particles PTC in the light scattering layer DF may be, for example, 25% by volume or more. The effect of increasing the light extraction efficiency is improved by increasing the density, but in many cases, the saturation occurs when the density reaches about 25% by volume.

  The density of the particles PTC in the light scattering layer DF is, for example, 50% by volume or less. When this density is large, aggregation of the particles PTC is likely to occur when the scattering layer DF is formed.

  The average particle diameter of the particles PTC is, for example, 500 nm or less. The average particle diameter of the particles PTC is, for example, 10 nm or more. When the average particle size is large or small, light scattering by the light scattering layer DF may be sufficient. The “average particle diameter” referred to here is measured using, for example, a light scattering method.

  The magnitude of the effect that the light scattering layer DF scatters light depends on the thickness of the light scattering layer DF. As an example, when the thickness of the light scattering layer DF is 0.5 μm or more, about 50% or more of the incident light can be scattered, and when the thickness of the light scattering layer DF is 1 μm or more, about 80% of the incident light. The above can be scattered. However, if the light scattering layer DF is thickened, it becomes difficult for light to be emitted from the substrate SUB1 side. As an example, when the thickness of the light scattering layer DF is 3 μm or more, the transmittance of the light scattering layer DF is about 5% or less.

  The forward scattering property and the backward scattering property of the light scattering layer DF may be the same or different. For example, by making the forward scattering property and the backward scattering property different, the transmittance of the display panel DP is made different between when light is incident from the substrate SUB1 side and when light is incident from the substrate SUB2 side. be able to. Further, according to the ratio of the forward scattering property and the backward scattering property of the light scattering layer DF, the energy of the light emitted from the light emitting layer EMT and emitted from the substrate SUB1 side, and the light energy emitted from the light emitting layer EMT and from the substrate SUB2 side. The ratio with the energy of the emitted light can be changed. The ratio of the forward scattering property and the backward scattering property of the light scattering layer DF depends on, for example, the volume ratio of the particles PTC in the light scattering layer DF, the thickness of the light scattering layer DF, the average particle size of the particles PTC, and the like. Can be changed.

  The display panel DP may be arranged so that the substrate SUB1 faces indoors and the substrate SUB2 faces outdoor. Alternatively, the display panel DP may be arranged so that the substrate SUB2 faces indoors and the substrate SUB1 faces outdoor.

  The building member BC may be another building member such as a door. That is, the display panel DP may be at least a part of the door plate, and the support SPT may be a door frame. Moreover, you may use a double-sided light emission type organic electroluminescence display for uses other than a building member.

1 is a cross-sectional view schematically showing a double-sided light emitting organic EL display device according to one embodiment of the present invention. The figure which shows schematically the example which applied the display apparatus of FIG. 1 to the building.

Explanation of symbols

  ACT ... active layer, BLD ... building, CTR ... customer, DF ... light scattering layer, DP ... display panel, E1 ... electrode, E2 ... electrode, EIL ... electron injection layer, EMT ... light emitting layer, ETL ... electron transport layer, HBL ... hole blocking layer, HIL ... hole injection layer, HTL ... hole transport layer, LM ... lighting device, OLED ... organic EL element, PSR ... passerby, PTC ... particles, RL ... resin layer, SN ... sun, SS ... Seal layer, SUB1 ... Substrate, SUB2 ... Substrate, W ... Window, WF ... Window frame, WP ... Window plate.

Claims (4)

A transparent substrate;
A light transmissive first electrode disposed on the transparent substrate; a light transmissive second electrode facing the first electrode; and a light emitting layer interposed between the first and second electrodes. An organic EL device comprising an active layer, and constituting at least a part of an optical resonator in which light emitted from the light emitting layer is repeatedly reflected and interfered;
A double-sided light emitting organic EL display device comprising a light scattering layer disposed between the transparent substrate and the organic EL element or on the organic EL element.   2. The organic EL display device according to claim 1, wherein the light scattering layer is different in forward scattering property and backward scattering property.   The light scattering layer includes a light transmissive resin layer having a smaller refractive index than the surface region of the optical resonator on the light scattering layer side, and is dispersed in the resin layer and compared with the resin layer. The organic EL display device according to claim 1, further comprising a plurality of light-transmitting particles having a higher refractive index.   A building member comprising the organic EL display device according to claim 1 and a support body supporting the organic EL display device.

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