KR100741781B1 - Dual display apparatus - Google Patents

Abstract

A dual displaying apparatus is provided to minimize a thickness when forming the dual displaying device having the same light-emitting area by replacing electrodes of contact areas of OLED devices with single electrodes. A dual displaying apparatus includes a first driving device structure, a lower OLED displaying device, an upper OLED displaying device, and a second driving device structure. The first driving device structure is formed at a predetermined area of a transparent substrate(100). The lower OLED displaying device is electrically connected with the first driving device structure. The upper OLED displaying device is arranged at an upper part of the lower OLED displaying device. The second driving device structure is electrically connected with the upper OLED displaying device. The lower OLED displaying device and the upper OLED displaying device are formed by sequentially laminating a lower anode electrode(120), a lower organic light emitting layer(130), a lower cathode electrode(140), an upper anode electrode(160), an upper organic light emitting layer(170), and an upper cathode electrode(180).

Description

Duplex Display Unit {DUAL DISPLAY APPARATUS}

1A and 1B are conceptual views illustrating a structure of a conventional double-sided display device.

2 is a cross-sectional view showing another structure of a conventional double-sided display device.

Figure 3 is a cross-sectional view showing the structure of an embodiment of the present invention.

Figure 4 is a cross-sectional view showing the structure of another embodiment of the present invention.

*** Explanation of symbols for main parts of drawing ***

100: substrate 110, 115: driving element

114: flat film 117: extended electrode layer

120: lower anode electrode 130: lower organic light emitting layer

140: lower cathode electrode 150: insulating layer

160: upper anode electrode 170: upper organic light emitting layer

180: upper cathode electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly, to a double-side display device in which an organic light emitting diode (OLED) is overlapped in a vertical direction to enable double-sided light emission at a maximum aperture ratio.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes (CRTs). Such a flat panel display panel is based on a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic electroluminescence (EL). Organic light emitting diode (OLED) displays; and the like.

Among them, the OLED injects electrons and holes into the light emitting layer from the electron injection electrode (cathode electrode) and the hole injection electrode (anode electrode), respectively, so that the excitons, in which the injected electrons and holes combine, fall from the excited state to the ground state. When the device emits light.

Due to this principle, unlike LCD, which is conventionally used as a thin display device, it does not need a separate light source, and thus has the advantage of reducing the volume and weight of the device. Since the reaction speed is 1000 times faster than LCD, afterimage display is performed. As a result, it is emerging as a next-generation display device.

According to the size of these OLEDs, various driving methods are used. Typically, medium- and large-sized OLED displays have an active matrix driving method (AM method), and active matrix driving methods and passive (Passive) methods in small OLED displays. ) Matrix driving method (PM method) is used in combination. In the AM type OLED display, a switching element formed of a thin film transistor is installed in each OLED element (pixel), and the switching element is responsible for current control, thereby emitting a specific pixel until the next control point without a separate control signal. That's the way. On the other hand, the PM type display is a method of operating the entire panel area by using an afterimage by sequentially driving the OLED by a general matrix configuration.

Recently, researches have been conducted to provide a light emitting method of such an OLED display panel using a double-sided light emitting method, which allows a single panel to provide the same or different images on both sides selectively or simultaneously, thereby providing a mounting space. It is intended to provide a wider display area to the user while reducing it. At present, such a double-sided OLED display panel is being applied to a clamshell mobile communication terminal as a test, but its target is expected to gradually increase, and a camera / camcorder that allows a photographer and a subject to simultaneously check a shooting state, It is expected to be widely used in various video reproducing apparatus.

1A to 1B show a structure of a general double-sided light emitting OLED display, and FIG. 1A shows a rear panel of an individual OLED display device manufactured separately, and FIG. 1B shows a rear surface of an individual OLED display panel manufactured separately. After the arrangement, the protective cap is unified.

The structure of FIG. 1A simplifies the OLED, and sequentially forms the first electrode 11, the organic EL layer 12, and the second electrode 13 on the substrate 10, and adsorbs moisture and impurities. A getter 14 is attached to the protective cap 16 and then encapsulated so that the protective cap 16 protects the OLED device using the sealant 15. It is the simplest double-sided light emission method to manufacture such a basic structure and then place the protective cap 16 to face each other, but due to the double application of the protective cap 16, the volume is increased, the size sensitive device such as a mobile device It is difficult to apply, and the manufacturing cost, material cost, and processing time become longer, which increases the cost.

In the structure of FIG. 1B, the protective cap is removed, and each display panel is disposed to face the rear surface and sealed with a sealant 28 so that each of the substrates 20 and 24 operates as a protective cap of the opposite side. Accordingly, the first electrode 21, the organic EL layer 22, and the second electrode 23 are formed on the lower substrate 20, and the first electrode 25 and the organic EL layer 26 are formed on the upper substrate 24. After forming the second electrode 27, the second electrode 27 is formed to face the backside and is bonded to the sealant 28, thereby completing a double-sided display panel having an inner space as a buffer space. In this case, however, the OLED panels have to be manufactured separately, thereby increasing the cost and increasing the volume to secure the space.

FIG. 2 is a structure proposed to solve the above volume and cost problems, and is a structure presented as a practical one panel dual display (OPDD) device. As shown, the driving device 31 is disposed on the substrate 30, the flat film 32 is formed, and then the upper region is horizontally divided, and thus the first electrodes 33 and 36 and the organic light emitting layer having different characteristics, respectively. The second electrodes 35 and 38 are separately manufactured so that OLEDs having different light emitting directions are arranged by dividing one pixel area. Details thereof are disclosed in Korean Patent Laid-Open Publication No. 10-2004-0036636. However, since this structure divides one pixel area into a front emission element and a rear emission element, the aperture ratio is extremely lower than half of the cell area, resulting in low luminance and efficiency.

In order to solve the problems of the double-sided OLED display device as described above, an object of the present invention is to provide a vertical stack of the front emission OLED device and the rear emission OLED device to emit light up and down on the same plane, The present invention provides a double-sided display device capable of reducing manufacturing costs and increasing aperture ratio and brightness.

Another object of the embodiments of the present invention is to provide a double-side display device in which a single electrode is used as the contact electrodes of stacked OLED elements so that the OLED elements are shared, thereby minimizing the thickness of the double-side display element having the same light emitting area.

It is still another object of the present invention to provide a double-side display device in which contact electrodes of stacked OLED elements are formed by heterojunctions of electrodes having different work functions to enhance characteristics of each device.

It is still another object of the present invention to provide a double-sided display device in which an insulating layer is formed on the laminated junction portions of OLED elements to be stacked so that each OLED in the upper and lower portions can operate completely independently of each other.

It is still another object of the present invention to provide a double-side display device in which a driving circuit portion is stacked together with the OLEDs in a predetermined area to maximize the aperture ratio of the double-side display device having the same light emitting area and to minimize the thickness.

In order to achieve the above object, a double-sided display device according to an embodiment of the present invention, the first driving device structure formed in a predetermined region of the transparent substrate; A lower OLED display device electrically connected to the first driving device structure; An upper OLED display device disposed on the lower OLED display device; A second driving device structure electrically connected to the upper OLED display device, wherein the lower OLED display device and the upper OLED display device are in turn a lower anode electrode, a lower organic light emitting layer, a lower cathode electrode, an upper anode electrode, and an upper organic light emitting layer , Characterized in that formed in the stack of the upper cathode electrode order.

In addition, a double-sided display device according to another exemplary embodiment of the present invention may include first and second driving device structures respectively formed in different regions of the transparent substrate, and one side of the driving device structures on the transparent substrate on which the driving device structures are formed. A lower OLED including a transparent flat film formed to expose the electrodes, a lower anode electrode, a lower organic light emitting layer, and a lower cathode electrode sequentially formed on the one side of the transparent flat film and the first driving device structure; And an upper OLED composed of an upper anode electrode, an upper organic light emitting layer, and an upper cathode electrode, which are continuously formed on the upper electrode, and an extension electrode layer connecting the upper cathode electrode of the upper OLED and the second driving element.

Embodiments of the present invention as described above will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view showing the structure of an embodiment of the present invention, as shown in the first driving device (TFT and capacitor, etc.) 110 and the second driving device 115 on the transparent substrate 100 in a separate position The planar film 114 is formed on the driving devices, and a transparent dielectric material is formed on the driving devices. Although the illustrated planar film 114 is formed lower than the driving elements 110 and 115, the height of the driving elements 110 and 115 is greater than that of the driving elements 110 and 115 while exposing predetermined electrodes of the driving elements 110 and 115. It can be formed as. That is, the insulating layer may be selectively maintained between the driving devices and the OLED structures to be formed later by using a method of forming the through hole after forming the flat film 114 high. However, as shown, the height of the flat film 114 may be lower than that of the driving devices 110 and 115 so that the electrodes of the driving devices 110 and 115 may be exposed.

In the illustrated structure, the first driving device 110 is used as the lower OLED driving device, and the second driving device 115 is used as the upper OLED driving device. Accordingly, a lower OLED structure is formed on the first driving device 110 and the flat layer 114, and an upper OLED structure is formed on the first driving device 110 and the flat layer 114. In this case, a stacking state of the lower OLED structure and the upper OLED structure may be sequentially disposed on the flat layer 114, and the lower anode electrode 120, the lower organic emission layer 130, the lower cathode electrode 140, and the upper anode electrode 160 may be formed. ), The upper organic emission layer 170, and the upper cathode electrode 180. That is, by making the upper and lower OLED structures the same and sequentially forming the lower cathode electrode 140 and the upper anode electrode 160 to be in electrical contact, the OLED structures having different emission directions from each other can be stacked. When the lower cathode electrode 140 and the upper anode electrode 160 are electrically stacked as described above, the upper OLED is not driven when the lower OLED is driven, and the lower OLED is not driven when the upper OLED is driven. If both screens should be used at the same time, the common electrode may be positioned at the contact portion. However, if only one screen is to be driven at a time by using an effective current consumption or screen switching function, only one screen can be effectively driven through the above configuration. Both sides of the screen can be driven at the same time.

The first driving device 110 is connected to the lower anode electrode 120 of the lower OLED to drive the lower OLED, and the second driving device 115 is connected to the lower OLED to drive the upper OLED. It is connected to the upper cathode electrode 180. In this case, an electrode connection layer 117 is formed on the second driving device 115 to eliminate the step difference.

In general, in order to smoothly drive an OLED, the work function of the cathode electrode must be lower than that of the anode electrode. For this purpose, a material having a high work function (for example, ITO) is used as the anode electrode, and the work electrode is used as the cathode electrode. One or more of the conductive metals including Al, Ca, Mg, LIF / Al (lithium fluorine / aluminum) having low water function are used.

Therefore, the structure of each illustrated OLED may also be formed of electrodes having the same work function characteristics, and the lower cathode electrode 140 of the lower OLED and the upper anode electrode 160 of the upper OLED have a work function characteristic. It can be a different heterojunction electrode. That is, the lower cathode electrode 140 may be formed of a material having a low work function, and the upper anode electrode 160 may be formed of a material having a high work function. In addition, since the light emission directions of the stacked OLED structures are opposite to each other, the lower cathode electrode 140 of the lower OLED and the upper anode electrode 160 of the upper OLED reflect light generated in each emission layer in different directions, respectively. It is desirable to have reflective characteristics so that the amount of emitted light can be increased.

Unlike the above structure, the lower cathode electrode 140 of the lower OLED and the upper anode electrode 160 of the upper OLED may be configured as a single common electrode and then used as the respective electrodes. However, in this case, since the device may not be smoothly driven by the work function value of the common electrode, which is not appropriate, the common electrode may be formed of a material having a low work function value to be used as the cathode electrode of the lower OLED. In addition, the upper surface of the common electrode may be surface treated (by applying at least one of surface treatments such as mechanical, chemical, plasma, and laser treatment to increase work function) to be used as an anode electrode of the upper OLED. . In addition, a method of forming an electron injection layer under the common electrode or a hole injection layer on the common electrode may be considered.

Substantially, in each of the above OLED structures, the organic light emitting layer is a stack of a second organic common film composed of one or more of a first organic common film, a light emitting layer, and an electron transporting layer / electron injection layer composed of one or more of a hole injection layer / hole transport layer. It may have a structure. Therefore, the characteristics of each device can be appropriately maintained by using the combination and surface treatment of the above layers, so that any two of the electrode structures described above can be used to smoothly drive the real double-sided OLED. In particular, the thickness of the organic common film may be made thinner than the thickness of the upper anode electrode 160, so that the electrode is shared and the organic common film may be used, thereby reducing the thickness of the entire device. Alternatively, even when the individual electrodes 140 and 160 are used, the characteristics and efficiency of the device may be improved by applying the organic common layer.

In addition, since the lower anode electrode of the lower OLED structure is a portion where light is to be emitted, a high work function transparent conductive oxide film including ITO may be used, and the upper cathode electrode of the upper OLED structure is a portion where light should be emitted. Low work function translucent thin film metal may be used. Of course, a transparent conductive oxide film may be used for both layers or a translucent thin film metal may be used.

In the above structure, since the first driving device 110 is located in the lower region of the lower OLED to reduce the light emitting area, and the second driving device 115 is located at the side of the OLED and also reducing the light emitting area, the stacking of these The light emitting area of the lower OLED can be increased. That is, the lower OLED is driven using the illustrated second driving device 115, and an insulating layer is further formed instead of the extension electrode layer 117 formed on the second driving device 115. The light emitting area of the lower OLED may be further increased if the first driving device is formed on the upper portion and configured to connect with the upper cathode electrode of the upper OLED. Although the structure of the transistor needs to be repeated in order to implement the above structure, the process may be increased and the cost may be increased. However, the luminance of the lower OLED may be increased by increasing the emission aperture ratio.

4 is a structure in which an insulating layer 150 is further formed to electrically isolate between the lower OLED and the upper OLED, as shown in another embodiment of the present invention. Accordingly, the lower cathode electrode 140 of the lower OLED and the upper anode electrode 160 of the upper OLED may use a metal having reflective properties for light emission, and the lower cathode electrode 140 may have a low work function. The metal may be used, and the upper anode electrode 160 may use a metal having a high work function. In addition, since the lower OLED and the upper OLED are electrically completely separated by the above configuration, electrical interference does not occur during individual driving or simultaneous driving.

As described above, a plurality of OLEDs having different light emitting directions are stacked and disposed in a vertical direction on a single substrate, and a driving unit capable of driving each OLED is appropriately configured to maximize utilization of one single cell area. It is possible to form a bidirectional light emitting OLED structure and to reduce the deterioration of device characteristics through surface treatment or application of an organic common film while sharing the contact portion electrodes of the two OLEDs in order to minimize the height thereof. Alternatively, the contact portion may be configured to be a heterojunction of electrodes having different properties, or an insulating layer may be further formed between the electrodes to be contacted to electrically separate the OLEDs, thereby easily responding to various operating environments. .

As described above, the double-sided display device according to the exemplary embodiment of the present invention vertically stacks the top emission OLED element and the bottom emission OLED element to emit light from above and below on the same plane, thereby reducing the volume and manufacturing cost of the device, and reducing the aperture ratio and There is an effect that can increase the brightness.

The double-sided display device according to the exemplary embodiment of the present invention has an effect of minimizing the thickness of the double-sided display device having the same light emitting area by replacing the electrodes of the stacked OLED elements with a single electrode.

The double-sided display device according to an exemplary embodiment of the present invention forms contact electrodes of stacked OLED elements as a heterojunction structure of electrodes having different work functions, thereby reducing the thickness of the double-sided display elements while maintaining the characteristics of each device. There is an effect that can be reduced.

The double-side display device according to the embodiment of the present invention forms an insulating layer between the stacked partial electrodes of the stacked OLED elements, or makes the electrodes have a heterojunction structure of metal electrodes having different work functions, or for each device. By allowing a single metal electrode to be shared by the upper and lower OLEDs instead of the electrodes, it is possible to appropriately provide a double-side display device suitable for the purpose of use and the operating environment through a simple structure change while maintaining the minimum thickness and the maximum aperture ratio.

Claims (20)

A first driving device structure formed in a predetermined region of the transparent substrate; A lower OLED display device electrically connected to the first driving device structure; An upper OLED display device disposed on the lower OLED display device; A second driving device structure electrically connected to the upper OLED display device; And the lower OLED display element and the upper OLED display element are sequentially formed in a stack of a lower anode electrode, a lower organic emission layer, a lower cathode electrode, an upper anode electrode, an upper organic emission layer, and an upper cathode electrode. delete The extended electrode layer of claim 1, wherein the first driving device structure and the second driving device structure are located at different regions on a substrate, and the second driving device and the upper OLED display device are formed on the second driving device. Double-sided display device characterized in that connected via. The double-sided device of claim 1, wherein the first driving device structure is positioned below the lower OLED display device, and the lower OLED display device is supported by a flat film formed on a side surface of the first driving device. Display device. The double-sided display device as claimed in claim 1, wherein the first driving device structure and the second driving device structure are stacked on the same substrate area by an insulating layer. delete The double-side display device of claim 1, wherein the lower cathode electrode and the upper anode electrode formed thereon have a heterojunction structure of a material having a different work function. The double-side display device of claim 1, wherein the lower cathode electrode and the upper anode electrode are formed of a metal material having reflective characteristics. The double-side display device of claim 1, wherein the lower anode electrode and the upper cathode electrode are a transparent conductive oxide or a translucent thin film metal. The double-side display device of claim 1, wherein the lower cathode electrode and the upper anode electrode are physically single common electrode. The double-sided display device of claim 1, wherein an electron injection layer is further formed between the lower cathode electrode and the lower organic emission layer, or a hole injection layer is further formed between the upper anode electrode and the upper organic emission layer. The double-side display device of claim 1, wherein the lower cathode electrode and the upper anode electrode are physically single common electrodes, and a surface used as the upper anode is surface treated to increase a work function. The double-side display device of claim 1, further comprising a dielectric layer formed between the lower cathode electrode and the upper anode electrode. First and second drive element structures respectively formed in different regions of the transparent substrate; A transparent flat film formed to expose one electrode of the driving device structures on the transparent substrate on which the driving device structures are formed; A lower OLED consisting of a lower anode electrode, a lower organic light emitting layer, and a lower cathode electrode which are sequentially formed on the one side electrode of the transparent flat film and the first driving device structure; An upper OLED consisting of an upper anode electrode, an upper organic light emitting layer, and an upper cathode electrode continuously formed on the lower OLED; And an extension electrode layer connecting the upper cathode electrode of the upper OLED and the second driving element. The method of claim 14, wherein an electron injection layer is further formed between the lower cathode electrode of the lower OLED and the lower organic light emitting layer, or a hole injection layer is further formed between the upper anode electrode of the upper OLED and the upper organic light emitting layer. Duplex display device. The method of claim 14, wherein the lower organic light emitting layer of the lower OLED and the upper organic light emitting layer of the upper OLED are at least one of a first organic common layer, a light emitting layer, and an electron transport layer / electron injection layer, which is at least one of a hole injection layer and a hole transport layer. A double-side display device comprising a laminated structure composed of two organic common films. The double-side display device of claim 14, wherein a work function of a lower cathode electrode of the lower OLED and an upper anode electrode of the upper OLED bonded to the electrode is different. The double-side display device of claim 14, wherein the lower cathode electrode and the upper anode electrode are made of a metal material having reflective characteristics. 15. The method of claim 14, wherein the lower cathode electrode of the lower OLED and the upper anode electrode of the upper OLED are physically single common electrodes, and an upper surface of the common electrode used as the upper anode electrode is a surface for increasing work function. A double-sided display device, characterized in that processed. The double-side display device of claim 14, wherein an insulating layer is further formed between the lower cathode electrode of the lower OLED and the upper anode electrode of the upper OLED.

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