Double-sided organic light-emitting display

Abstract

To provide an organic light emitting display device having high aperture ratio and emitting efficiency and improved lifespan.SOLUTION: A dual side organic light emitting display device comprises: a first driving element and a second driving element that are positioned over a transparency substrate in a first region; a first organic light emitting diode that includes a first electrode positioned over the first and second driving elements in a second region and connected to the first driving element, a second electrode positioned over the first electrode, and a first organic light emitting layer positioned between the first and second electrodes; and a second organic light emitting diode that is positioned in the first and second regions and on the first organic light emitting diode, and includes a third electrode positioned over the second electrode, and connected to the second driving element, and a second organic light emitting layer positioned between the second and third electrodes. A light from the first organic light emitting diode is emitted toward a first direction via the first electrode, and a light from the second organic light emitting diode is emitted toward a second direction, which is opposite to the first direction, via the third electrode.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an organic light emitting display device, and more particularly to a double-sided organic light emitting display device having a high aperture ratio, luminous efficiency, and improved lifespan. [Background technology]

[0002] Recently, as display devices have become larger, there has been an increasing demand for flat display devices that occupy less space. One such flat display device, organic light emitting diode (OLED) technology, has been developing rapidly.

[0003] Organic light-emitting diodes are devices that emit light when electrons and holes are injected from the anode and cathode into a light-emitting material layer formed between an electron injection electrode (cathode) and a hole injection electrode (cathode), forming pairs and then disappearing. They can be formed on flexible, transparent substrates such as plastic, and have the advantages of being able to operate at low voltages (10V or less), consuming relatively little power, and producing excellent color.

[0004] The organic light emitting diode includes a first electrode, which is an anode, formed on a substrate, a second electrode facing the first electrode at a distance, and an organic light emitting layer located between the first electrode and the second electrode.

[0005] Recently, a double-sided display device has been proposed, in which images are displayed on both sides of the display device.

[0006] However, since the first electrode or the second electrode of the organic light emitting diode is made of an opaque material, there is a limit to the use of the conventional organic light emitting display device as a double-sided display device. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to solve the problem that conventional organic light emitting display devices cannot be used as double-sided display devices. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a double-sided organic light emitting display device comprising: a transparent substrate defining a pixel region including a first region and a second region; a first driving element and a second driving element positioned on the transparent substrate in the first region; a first organic light emitting diode (OLED) positioned on top of the first and second driving elements in the second region, the first electrode being connected to the first driving element, a second electrode facing the first electrode and positioned on top of the first electrode, and a first organic light emitting layer being positioned between the first and second electrodes; and a second organic light emitting diode positioned on top of the first organic light emitting diode in the first and second regions, the second electrode facing the second electrode, positioned on top of the second electrode and connected to the second driving element, and a second organic light emitting layer being positioned between the second and third electrodes, wherein light from the first OLED is emitted in a first direction through the first electrode and light from the second OLED is emitted in a second direction opposite to the first direction through the third electrode.

[0009] The double-sided organic light emitting display device of the present invention further includes: a gate line extending in a third direction; and first and second data lines extending in a fourth direction intersecting the third direction.

[0010] In the double-sided organic light emitting display device of the present invention, the first driving element and the second driving element are each located in the third direction from the first organic light emitting diode.

[0011] In the double-sided organic light emitting display device of the present invention, the first driving element and the second driving element are each located in the fourth direction from the first organic light emitting diode.

[0012] The double-sided organic light emitting display device of the present invention further includes: a low-level voltage wiring connected to the second electrode; a first high-level voltage wiring connected to the first driving element; and a second high-level voltage wiring connected to the second driving element.

[0013] In the double-sided organic light emitting display device of the present invention, the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring each extend along the third direction.

[0014] In the double-sided organic light emitting display device of the present invention, the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring each extend along the fourth direction.

[0015] In the double-sided organic light emitting display device of the present invention, the second organic light emitting diode overlaps with the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring.

[0016] In the double-sided organic light emitting display device of the present invention, the second organic light emitting diode has a larger area than the first organic light emitting diode.

[0017] In the double-sided organic light emitting display device of the present invention, at least one of the first organic light emitting layer and the second organic light emitting layer is formed by a solution process.

[0018] In the double-sided organic light-emitting display device of the present invention, the first organic light-emitting layer is formed by a solution process, and the second organic light-emitting layer is formed by a deposition process.

[0019] In the double-sided organic light-emitting display device of the present invention, the first electrode and the third electrode are each a transparent electrode, and the second electrode is a reflective electrode.

[0020] In the double-sided organic light emitting display device of the present invention, the first organic light emitting diode has a normal structure, and the second organic light emitting diode has an inverted structure.

[0021] In the double-sided organic light-emitting display device of the present invention, the first organic light-emitting layer includes a first light-emitting material layer, a first hole transport layer located between the first electrode and the first light-emitting material layer, and a first electron transport layer located between the first light-emitting material layer and the second electrode, and the second organic light-emitting layer includes a second light-emitting material layer, a second electron transport layer located between the second electrode and the second light-emitting material layer, and a second hole transport layer located between the second light-emitting material layer and the third electrode.

[0022] In the double-sided organic light-emitting display device of the present invention, the first organic light-emitting layer emits light in a first wavelength range, the second organic light-emitting layer emits light in a second wavelength range, and the first wavelength range and the second wavelength range are the same.

[0023] In the double-sided organic light-emitting display device of the present invention, the first organic light-emitting layer emits light in a first wavelength range, and the second organic light-emitting layer emits light in a second wavelength range, and the first wavelength range and the second wavelength range are different from each other.

[0024] The double-sided organic light emitting display device of the present invention includes a first organic light emitting diode (OLED) including a first electrode connected to a first driving element, a second electrode connected to a low-level voltage wiring, and a first organic light emitting layer positioned between the first and second electrodes, and a second organic light emitting diode (OLED) including a third electrode connected to a second driving element and a second organic light emitting layer positioned between the second and third electrodes, and the first and second OLEDs are independently driven to realize a double-sided image display.

[0025] In addition, since the reduction in aperture ratio due to the first and second driving elements is not reflected in the second organic light emitting diode that emits light in the second direction (front), the energy efficiency of the second organic light emitting diode is improved and its lifespan is increased.

[0026] Therefore, the double-sided organic light emitting display device of the present invention has a high aperture ratio, a high luminous efficiency, an improved lifespan, and can be driven with low power consumption. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic circuit diagram of one pixel region in a double-sided organic light emitting display device according to an embodiment of the present invention; [Figure 2] 1 is a schematic plan view of one pixel region in a double-sided organic light emitting display device according to a first embodiment of the present invention; [Figure 3] 10 is a schematic plan view of one pixel region in a double-sided organic light emitting display device according to a second embodiment of the present invention. [Figure 4] 1 is a schematic plan view of a pixel region structure in a double-sided organic light emitting display device according to a first embodiment of the present invention; [Figure 5] FIG. 5 is a cross-sectional view taken along line II' in FIG. [Figure 6] 1 is a schematic cross-sectional view of an organic light-emitting diode. [Figure 7] 10 is a schematic plan view of a pixel region structure in a double-sided organic light emitting display device according to a second embodiment of the present invention; [Figure 8] FIG. 8 is a cross-sectional view taken along line II-II' in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0028] The advantages and features of the present invention, as well as methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. However, the embodiments are provided so that the disclosure of the present invention will be complete and will fully convey the scope of the invention to those skilled in the art.

[0029] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating the embodiments of the present invention are merely examples, and the present invention is not limited to the illustrated details. The same reference symbols refer to the same elements throughout the specification. Furthermore, in describing the present invention, if a detailed description of related prior art is deemed to unnecessarily obscure the gist of the present invention, such a detailed description will be omitted. When words such as "include," "have," and "be," are used in this specification, other parts may be added unless "only" is used. When a component is expressed in the singular, it also includes a plural unless otherwise explicitly stated.

[0030] When interpreting elements, they are interpreted as including a margin of error even if there is no other explicit description.

[0031] When describing a positional relationship, for example, when the positional relationship between two parts is described using terms such as "above," "on top," "below," or "beside," one or more other parts may be located between the two parts, unless "immediately" or "directly" is used.

[0032] When describing a temporal relationship, for example, when the temporal sequence is described using "after," "following," "next," or "before," it can also include cases where the relationship is not consecutive, since "immediately" or "directly" is not used.

[0033] Although terms such as "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, a first component referred to below may be a second component within the technical concept of the present invention.

[0034] The features of the various embodiments of the present invention may be partially or fully combined or combined with each other, and various technical interlocking and driving mechanisms may be possible. Each embodiment may be implemented independently of the others, or may be implemented together in a linked relationship.

[0035] Preferred embodiments of the present invention will now be described with reference to the drawings.

[0036] FIG. 1 is a schematic circuit diagram of one pixel region in a double-sided organic light emitting display device according to an embodiment of the present invention.

[0037] As shown in FIG. 1, the double-sided OLED display includes a gate line GL, a first data line DL1, a second data line DL2, a low-level voltage line Vss, a first high-level voltage line Vdd1, a second high-level voltage line Vdd2, a first switching element Ts1, a second switching element Ts, a first driving element Td1, a second driving element Td2, a first organic light-emitting diode D1, and a second organic light-emitting diode D2.

[0038] In addition, a first storage capacitor Cst1 and a second storage capacitor Cst2 may be further formed.

[0039] A pixel is defined by the gate line GL and the first data line DL1, and the pixel region P can include a red pixel region, a green pixel region, and a blue pixel region.

[0040] The first switching element Ts1 is connected to the gate line GL and the first data line DL1, the first driving element Td1 and the first storage capacitor Cst1 are connected between the first switching element Ts1 and the first high-level voltage line Vdd1, and the first organic light emitting diode D1 is connected to the first driving element Td1 and the low-level voltage line Vss.

[0041] The second switching element Ts2 is connected to the gate line GL and the second data line DL2, the second driving element Td2 and the second storage capacitor Cst2 are connected between the second switching element Ts2 and the second high-level voltage line Vdd2, and the second organic light emitting diode D2 is connected to the second driving element Td2 and the low-level voltage line Vss.

[0042] In such a double-sided OLED display, when the first switching thin film transistor Ts1 is turned on by the gate signal applied to the gate line GL, the first data signal applied to the first data line DL1 is applied to the gate electrode of the first driving element Td1 and one electrode of the first storage capacitor Cst1 through the first switching element Ts1.

[0043] The first driving element Td1 is turned on by the first data signal applied to the gate electrode, and as a result, a current proportional to the first data signal flows from the first high-level voltage line Vdd1 through the first driving element Td1 to the first organic light-emitting diode D1, and the first organic light-emitting diode D1 emits light with a brightness proportional to the current flowing through the first driving element Td1.

[0044] At this time, the first storage capacitor Cst1 is charged with a voltage proportional to the first data signal, so that the voltage of the gate electrode of the first driving device Td1 is maintained constant for one frame.

[0045] In addition, when the second switching thin film transistor Ts2 is turned on by the gate signal applied to the gate line GL, the second data signal applied to the second data line DL2 is applied to the gate electrode of the second driving element Td2 and one electrode of the second storage capacitor Cst2 through the second switching element Ts2.

[0046] The second driving element Td2 is turned on by the second data signal applied to the gate electrode, and as a result, a current proportional to the second data signal flows from the second high-level voltage wiring Vdd2 through the second driving element Td2 to the second organic light-emitting diode D2, and the second organic light-emitting diode D2 emits light with a brightness proportional to the current flowing through the second driving element Td2.

[0047] At this time, the second storage capacitor Cst2 is charged with a voltage proportional to the second data signal, so that the voltage of the gate electrode of the second driving device Td2 is maintained constant for one frame.

[0048] Therefore, the double-sided organic light emitting display device can display a desired image.

[0049] FIG. 2 is a schematic plan view of one pixel region in the double-sided organic light emitting display device according to the first embodiment of the present invention.

[0050] 2, in a double-sided OLED display, the gate lines GL extend in a first direction (x), and the first data lines DL1 extend in a second direction (y) that intersects with the first direction (y). For example, the first direction (x) and the second direction (y) may be perpendicular to each other.

[0051] The double-sided OLED display device has a first opening op1 corresponding to a first electrode (lower electrode, first positive electrode) of the first OLED D1 and a second opening op2 corresponding to a second electrode (middle electrode, negative electrode) shared by the first OLED D1 and the second OLED D2. The first opening op1 may be a light-emitting region of the first OLED D1, and the second opening op2 may be a light-emitting region of the second OLED D2.

[0052] The second opening op2 completely overlaps the first opening op1 and has a larger area than the first opening op1. That is, the first organic light-emitting diode D1 has a first aperture ratio, and the second organic light-emitting diode D2 has a second aperture ratio that is larger than the first aperture ratio.

[0053] The double-sided organic light emitting display device also includes a first pixel driving circuit unit PDC1 for driving the first organic light emitting diode D1 and a second pixel driving circuit unit PDC2 for driving the second organic light emitting diode D2, and the first and second pixel driving circuit units PDC1 and PDC2 are located in the first direction (x) from the first opening op1.

[0054] For example, each of the first and second pixel driving circuit units PDC1 and PDC2 may include a switching element, a driving element, and a storage capacitor.

[0055] That is, the first and second pixel driving circuit units PDC1 and PDC2 do not overlap with the first opening op1 but overlap with the second opening op2. In other words, the first organic light emitting diode D1 does not overlap with the first and second pixel driving circuit units PDC1 and PDC2, and the second organic light emitting diode D2 overlaps with the first and second pixel driving circuit units PDC1 and PDC2.

[0056] The pixel region P is defined into a first region and a second region, with the first and second pixel driving circuit units PDC1 and PDC2 located in the first region and the first organic light emitting diode D1 located in the second region. The first pixel driving circuit unit PDC1 including the first driving element Td1 and the second pixel driving circuit unit PDC2 including the second driving element Td2 are located in the first direction (x) from the first organic light emitting diode D1. Meanwhile, the second organic light emitting diode D2 is located in both the first and second regions.

[0057] Therefore, the aperture ratio of the second organic light emitting diode D2 increases.

[0058] FIG. 3 is a schematic plan view of one pixel region in a double-sided organic light emitting display device according to a second embodiment of the present invention.

[0059] 3, in a double-sided OLED display, the gate lines GL extend in a first direction (x), and the first data lines DL1 extend in a second direction (y) that intersects with the first direction (y). For example, the first direction (x) and the second direction (y) may be perpendicular to each other.

[0060] The double-sided OLED display device has a first opening op1 corresponding to a first electrode (lower electrode, first positive electrode) of the first OLED D1 and a second opening op2 corresponding to a second electrode (middle electrode, negative electrode) shared by the first OLED D1 and the second OLED D2. The first opening op1 may be a light-emitting region of the first OLED D1, and the second opening op2 may be a light-emitting region of the second OLED D2.

[0061] The second opening op2 completely overlaps the first opening op1 and has a larger area than the first opening op1. That is, the first organic light-emitting diode D1 has a first aperture ratio, and the second organic light-emitting diode D2 has a second aperture ratio that is larger than the first aperture ratio.

[0062] The double-sided organic light emitting display device also includes a first pixel driving circuit unit PDC1 for driving the first organic light emitting diode D1 and a second pixel driving circuit unit PDC2 for driving the second organic light emitting diode D2, and the first and second pixel driving circuit units PDC1 and PDC2 are located in the second direction (y) from the first opening op1.

[0063] That is, the first and second pixel driving circuit units PDC1 and PDC2 do not overlap with the first opening op1 but overlap with the second opening op2. In other words, the first organic light emitting diode D1 does not overlap with the first and second pixel driving circuit units PDC1 and PDC2, and the second organic light emitting diode D2 overlaps with the first and second pixel driving circuit units PDC1 and PDC2.

[0064] The pixel region P is defined into a first region and a second region, with the first and second pixel driving circuit units PDC1 and PDC2 located in the first region and the first organic light emitting diode D1 located in the second region. The first pixel driving circuit unit PDC1 including the first driving element Td1 and the second pixel driving circuit unit PDC2 including the second driving element Td2 are located in the second direction (y) from the first organic light emitting diode D1. Meanwhile, the second organic light emitting diode D2 is located in both the first and second regions.

[0065] Therefore, the aperture ratio of the second organic light emitting diode D2 increases.

[0066] FIG. 4 is a schematic plan view of a pixel region structure in a double-sided organic light emitting display device according to a first embodiment of the present invention.

[0067] As shown in FIG. 4, the double-sided OLED display device 100 includes a gate line GL, a low-level voltage line Vss, a first high-level voltage line Vdd1, a second high-level voltage line Vdd2, a first data line DL1, a second data line DL2, a first driving element (Td1 in FIG. 1), a second driving element (Td2 in FIG. 1), a first organic light-emitting diode D1, and a second organic light-emitting diode D2.

[0068] The gate line GL extends along a first direction (x), and the first data line DL1, the second data line DL2, the low-level voltage line Vss, the first high-level voltage line Vdd1, and the second high-level voltage line Vdd2 extend in a second direction (y) that intersects with the first direction (x). For example, the second direction (y) may be perpendicular to the first direction (x).

[0069] The first driving device Td1 is connected to the first high-level voltage wiring Vdd1, and the second driving device Td2 is connected to the second high-level voltage wiring Vdd2.

[0070] The first organic light emitting diode D1 is connected to the first driving element Td1 and the low-level voltage line Vss, and the second organic light emitting diode D2 is connected to the second driving element Td2 and the low-level voltage line Vss.

[0071] In addition, the double-sided organic light emitting display device 300 may further include a first switching element (Ts1 in FIG. 1) connected to the gate line GL, the first data line DL, and the first driving element Td1, and a second switching element (Ts2 in FIG. 1) connected to the gate line GL, the second data line DL, and the second driving element Td2.

[0072] The low level voltage line Vss, the first data line DL1, the first high level voltage line Vdd1, the second data line DL2, and the second high level voltage line Vdd2 may be sequentially arranged along the first direction (x) at regular intervals.

[0073] The low-level voltage wiring Vss or the first data wiring DL1 and the second high-level voltage wiring Vdd2 intersect with the gate wiring GL to define pixel regions P, and the first switching element Ts1, the second switching element Ts2, the first driving element Td1, the second driving element Td2, the first organic light-emitting diode D1, and the second organic light-emitting diode D2 are arranged in each pixel region P.

[0074] The first organic light emitting diode D1 includes a first electrode 210 which is an anode, a first organic light emitting layer, and a second electrode 230 which is an anode, and the second organic light emitting diode D2 includes a second electrode 230 which is an anode, a second organic light emitting layer, and a third electrode 250 which is an anode. That is, the second organic light emitting diode D2 is located above the first organic light emitting diode D1, sharing the second electrode 230 which is an anode with the first organic light emitting diode D1.

[0075] The first organic light emitting diode D1 and the second organic light emitting diode D2 share the negative second electrode 230. The first organic light emitting diode D1 is driven by the first driving element Td1, and the second organic light emitting diode D2 is driven by the second driving element Td2. That is, the first organic light emitting diode D1 and the second organic light emitting diode D2 are driven independently.

[0076] The first organic light emitting diode D1 is located in the space between the first data line DL1 and the first high-level voltage line Vdd1, and the second organic light emitting diode D2 has a larger planar area than the first organic light emitting diode D1. For example, one end of the second organic light emitting diode D2 may overlap the low-level voltage line Vss, and the other end may overlap the second high-level voltage line Vdd2.

[0077] That is, the first organic light emitting diode D1 does not overlap with the gate line GL, the first and second data lines DL1 and DL2, the low-level voltage line Vss, and the first and second high-level voltage lines Vdd1 and Vdd2, while the second organic light emitting diode D2 may overlap with the gate line GL, the first and second data lines DL1 and DL2, the low-level voltage line Vss, and the first and second high-level voltage lines Vdd1 and Vdd2.

[0078] The first organic light emitting diode D1 emits light in a first normal direction relative to the first direction (x) and the second direction (y), and the second organic light emitting diode D2 emits light in a second normal direction opposite to the first normal direction.

[0079] Therefore, the double-sided organic light emitting display device 100 of the present invention can realize a double-sided image display in which a first image is displayed in a first normal direction and a second image is displayed in a second normal direction.

[0080] FIG. 5 is a cross-sectional view taken along line II' in FIG.

[0081] As shown in FIG. 5, a first driving element Td1, a second driving element Td2, a first organic light emitting diode D1, and a second organic light emitting diode D2 are formed on a first transparent substrate 110 in which a pixel region is defined.

[0082] In addition, a protection layer (170) covering the second organic light emitting diode D2, a sealing layer 180 on the protection layer 170, and a second transparent substrate 190 on the sealing layer 180 may be provided on the second organic light emitting diode D2.

[0083] Each of the first and second transparent substrates 110 and 190 may be a glass substrate or a flexible substrate, for example, a polyimide (PI) substrate, a polyethersulfone (PES) substrate, a polyethylenenaphthalate (PEN) substrate, a polyethyleneterephthalate (PET) substrate, or a polycarbonate (PC) substrate.

[0084] A buffer layer 112 is formed on the first transparent substrate 110, and the first driving element Td1 and the second driving element Td2 are formed on the buffer layer 112. For example, the buffer layer 112 may be made of an inorganic insulating material such as silicon nitride. The buffer layer 112 may be omitted, in which case the first driving element Td1 and the second driving element Td2 may be formed on the first transparent substrate 110.

[0085] A first semiconductor layer 120 and a second semiconductor layer 122 are formed on the buffer layer 112. For example, the first semiconductor layer 120 and the second semiconductor layer 122 may each be made of an oxide semiconductor material. When the first semiconductor layer 120 and the second semiconductor layer 122 are each made of an oxide semiconductor material, a light-shielding pattern (not shown) may be formed below the first semiconductor layer 120 and the second semiconductor layer 122. The light-shielding pattern prevents light from being incident on the first semiconductor layer 120 and the second semiconductor layer 122, thereby preventing the first semiconductor layer 120 and the second semiconductor layer 122 from being deteriorated by light.

[0086] Alternatively, each of the first semiconductor layer 120 and the second semiconductor layer 122 may be made of polycrystalline silicon, and in this case, both ends of each of the first semiconductor layer 120 and the second semiconductor layer 122 may be doped with impurities.

[0087] A gate insulating layer 124 made of an insulating material is formed on the first semiconductor layer 120 and the second semiconductor layer 122 on the front surface of the first transparent substrate 110. The gate insulating layer 124 may be made of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx).

[0088] A first gate electrode 126 and a second gate electrode 128 made of a conductive material such as metal are formed on the gate insulating film 124. The first gate electrode 126 corresponds to the center of the first semiconductor layer 120, and the second gate electrode 128 corresponds to the center of the second semiconductor layer 122.

[0089] Furthermore, a gate wiring GL is formed on the gate insulating film 124 .

[0090] Although the gate insulating film 124 is formed on the front surface of the first transparent substrate 110 in FIG. 5, the gate insulating film 124 may be patterned in the same shape as the first gate electrode 126 and the second gate electrode 128, respectively.

[0091] An interlayer insulating film 130 made of an insulating material is formed on the front surface of the first transparent substrate 110 on the first gate electrode 126 and the second gate electrode 128. The interlayer insulating film 130 may be made of an inorganic insulating material such as silicon oxide or silicon nitride, or an organic insulating material such as benzocyclobutene or photo-acrylic.

[0092] The interlayer insulating film 130 has first and second semiconductor layer contact holes 132 and 134 exposing both upper surfaces of the first semiconductor layer 120 and third and fourth semiconductor layer contact holes 136 and 138 exposing both upper surfaces of the second semiconductor layer 122. The first and second semiconductor layer contact holes 132 and 134 are located on both sides of the first gate electrode 126 and spaced apart from the first gate electrode 126, and the third and fourth semiconductor layer contact holes 136 and 138 are located on both sides of the second gate electrode 128 and spaced apart from the second gate electrode 128.

[0093] 5, the first to fourth semiconductor layer contact holes 132, 134, 136, and 138 are formed in the interlayer insulating film 130 and the gate insulating film 124. Alternatively, if the gate insulating film 124 is patterned to have the same shape as the first and second gate electrodes 126 and 128, respectively, the first to fourth semiconductor layer contact holes 132, 134, 136, and 138 may be formed only in the interlayer insulating film 130.

[0094] A first source electrode 142, a first drain electrode 144, a second source electrode 146, and a second drain electrode 148 made of a conductive material such as metal are formed on the interlayer insulating film 130. The first source electrode 142 and the first drain electrode 144 are spaced apart around the first gate electrode 126 and contact both sides of the first semiconductor layer 120 through first and second semiconductor layer contact holes 132 and 134, respectively. The second source electrode 146 and the second drain electrode 148 are spaced apart around the second gate electrode 128 and contact both sides of the second semiconductor layer 122 through third and fourth semiconductor layer contact holes 136 and 138, respectively.

[0095] The first semiconductor layer 120, the first gate electrode 126, the first source electrode 142, and the first drain electrode 144 form a first driving element Td1, and the second semiconductor layer 122, the second gate electrode 128, the second source electrode 146, and the second drain electrode 148 form a second driving element Td2. Each of the first and second driving elements may be a thin film transistor (TFT).

[0096] 5, a first gate electrode 126, a first source electrode 142, and a first drain electrode 144 are located on the first semiconductor layer 120, and a second gate electrode 128, a second source electrode 146, and a second drain electrode 148 are located on the second semiconductor layer 122. That is, the first driving device Td1 and the second driving device Td2 each have a coplanar structure.

[0097] Alternatively, the first and second driving transistors Td1 and Td2 may each have a gate electrode located below a semiconductor layer and a source electrode and a drain electrode located above the semiconductor layer. That is, the first and second driving transistors Td1 and Td2 may each have an inverted staggered structure. In this case, the semiconductor layer may be made of amorphous silicon.

[0098] In addition, a low-level voltage line Vss, a first data line DL1, a first high-level voltage line Vdd1, a second data line DL2, and a second high-level voltage line Vdd2 are formed on the interlayer insulating film 130. The low-level voltage line Vss, the first data line DL1, the first high-level voltage line Vdd1, the second data line DL2, and the second high-level voltage line Vdd2 may be made of the same material as the first source electrode 142.

[0099] The first high-level voltage wiring Vdd1 is connected to the first source electrode 142. For example, the first source electrode 142 may be extended from the first high-level voltage wiring Vdd1. The second high-level voltage wiring Vdd2 is connected to the second source electrode 146. For example, the second source electrode 146 may be extended from the second high-level voltage wiring Vdd2.

[0100] Each pixel region P further includes a first switching element Ts1 connected to the gate line GL and the first data line DL1, and a second switching element Ts2 connected to the gate line GL and the second data line DL2. The first and second switching elements Ts1 and Ts2 may be thin film transistors. The first switching element Ts1 is connected to the first driving element Td1, and the second switching element Ts2 is connected to the second driving element Td2.

[0101] For example, the first switching element Ts1 may include a semiconductor layer, a gate electrode, a source electrode, and a drain electrode, the gate electrode may be connected to the gate line GL, the source electrode may be connected to the first data line DL1, and the drain electrode may be connected to the first drain electrode 144 of the first driving element Td1.

[0102] The second switching element Ts2 may include a semiconductor layer, a gate electrode, a source electrode, and a drain electrode, the gate electrode may be connected to the gate line GL, the source electrode may be connected to the second data line DL2, and the drain electrode may be connected to the second drain electrode 148 of the second driving element Td2.

[0103] In addition, each pixel region P may further include a first storage capacitor Cst1 for maintaining the voltage of the first gate electrode 126 of the first driving element Td1 constant during one frame, and a second storage capacitor Cst2 for maintaining the voltage of the second gate electrode 128 of the second driving element Td2 constant.

[0104] A planarization layer 150 is formed on the front surface of the first transparent substrate 110 on the first source electrode 142, the first drain electrode 144, the second source electrode 146, the second drain electrode 148, the low-level voltage line Vss, the first data line DL1, the first high-level voltage line Vdd1, the second data line DL2, and the second high-level voltage line Vdd2. The planarization layer 150 has a flat top surface and has a first drain contact hole 152 exposing the first drain electrode 144 of the first driving element Td1.

[0105] The first electrodes 210 separated for each pixel region P are formed on the planarization layer 150. The first electrodes 210 are connected to the first drain electrodes 144 of the first driving transistors Td1 through first drain contact holes 152.

[0106] The first electrode 210 may be an anode and may be made of a conductive material with a relatively high work function, such as a transparent conductive oxide (TCO). Specifically, the first electrode 210 may be made of one of indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc-oxide (ITZO), tin oxide (SnO), zinc oxide (ZnO), indium-copper-oxide (ICO), and aluminum:zinc oxide (Al:ZnO; AZO). That is, the first electrode 210 is a transparent electrode.

[0107] The first electrode 210 has an area smaller than the pixel area P. For example, the first electrode 210 may be located within an area defined by the gate line GL, the first data line DL1, and the first high-level voltage line Vdd1.

[0108] A bank layer 160 is formed on the planarization layer 150 to cover the edges of the first electrodes 210. The bank layer 160 includes a first bank 162 having a first thickness and a second bank 164 having a second thickness greater than the first thickness and positioned on the first bank 162. For example, the first bank 162 has a first height from the first transparent substrate 110, and the second bank 164 has a second height from the first transparent substrate 110 that is greater than the first height.

[0109] The bank layer 160 includes a first opening op1 corresponding to the first electrode 210 and a second opening op2 having an area larger than the first opening op1 and corresponding to the pixel region P. That is, the first bank 162 has the first opening op1 exposing the center of the first electrode 210, and the second bank 164 has the second opening op2 corresponding to the pixel region P.

[0110] A common contact hole 166 exposing the low-level voltage wiring Vss and a second drain contact hole 168 exposing the second drain electrode 148 of the second driving device Td2 are formed through the bank layer 160 and the planarization layer 150.

[0111] A first organic light-emitting layer 220 is formed on the first electrode 210. The first organic light-emitting layer 220 may have a single-layer structure of a first light-emitting material layer (EML). Alternatively, the first organic light-emitting layer 220 may have a multi-layer structure by further including at least one of a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL).

[0112] Alternatively, the first organic light emitting layer 220 may include two or more light emitting material layers spaced apart from each other, which may be light emitting material layers of the same color or different colors.

[0113] At least a portion of the first organic light-emitting layer 220 may be formed by a solution process. For example, the first organic light-emitting layer 220 may be formed by an inkjet process or a spin-coating process. Alternatively, the first organic light-emitting layer 220 may be formed by a deposition process. In FIG. 5, the first organic light-emitting layer 220 is formed by a solution process, and the first organic light-emitting layer 220 is formed in the first opening op1, and the thickness of the edge may be greater than the thickness of the center.

[0114] A second electrode 230 is formed on the first transparent substrate 110 on which the first organic light emitting layer 220 and the bank layer 160 are formed. The second electrode 230 is connected to the low-level voltage line Vss through a common contact hole 166.

[0115] The second electrode 230 may be separated for each pixel region. Alternatively, the second electrode 230 of a first pixel region may be integrally formed with the second electrode of a second pixel region adjacent to the first pixel region across the low-level voltage line Vss.

[0116] The second electrode 230 is located on the first organic light-emitting layer 220 at the first opening op1, and on the first bank 162 at the second opening op2. That is, the second electrode 230 has a larger area than the first electrode 210 and the first organic light-emitting layer 220. The area of ​​the second electrode 230 may be the same as the area of ​​the second opening op2.

[0117] The second electrode 230 may be made of a conductive material with a relatively low work function and used as a cathode. For example, the second electrode 230 may be made of a material with high conductivity and high reflectivity, such as aluminum (Al), magnesium (Mg), calcium (Ca), silver (Ag), or an alloy or combination thereof. In other words, the second electrode 230 is a reflective electrode.

[0118] That is, the first organic light emitting diode D1 is disposed on the planarization layer 150 and includes a first electrode 210, a first organic light emitting layer 220, and a second electrode 230 sequentially stacked on the first electrode 210. The first organic light emitting diode D1 is disposed in the red pixel region, the green pixel region, and the blue pixel region, respectively, and can emit red, green, and blue light, respectively. Alternatively, the first organic light emitting diode D1 can emit white light.

[0119] A second organic light emitting layer 240 is formed on the second electrode 230. The second organic light emitting layer 240 has substantially the same area as the second electrode 230.

[0120] The first organic light-emitting layer 220 may emit light in a first wavelength range, and the second organic light-emitting layer 240 may emit light in a second wavelength range that may be the same as or different from the first wavelength. For example, the light in the first wavelength range and the light in the second wavelength range may each be one of red, green, and blue light.

[0121] The second organic light-emitting layer 240 may have a single-layer structure of a second light-emitting material layer, or may have a multi-layer structure by further including at least one of a hole-injecting layer, a hole-transporting layer, an electron-blocking layer, a hole-blocking layer, an electron-transporting layer, and an electron-injecting layer.

[0122] Alternatively, the second organic light emitting layer 240 may include two or more light emitting material layers spaced apart from each other, which may be light emitting material layers of the same color or different colors.

[0123] At least a portion of the second organic light-emitting layer 240 may be formed by a solution process. For example, the second organic light-emitting layer 240 may be formed by an inkjet process or a spin-coating process. Alternatively, the second organic light-emitting layer 240 may be formed by a deposition process. In FIG. 5, the second organic light-emitting layer 240 is formed by a solution process, and the second organic light-emitting layer 240 is formed in the second opening op2, and the thickness of the edge may be greater than the thickness of the center.

[0124] The first organic light-emitting layer 220 is located within the area surrounded by the first bank 162 , while the second electrode 230 and the second organic light-emitting layer 240 are located within the area surrounded by the second bank 164 .

[0125] In one embodiment, the first organic light emitting layer 220 may be formed by a solution process, and the second organic light emitting layer 240 may be formed by a vapor deposition process.

[0126] A third electrode 250 is formed on the second organic light emitting layer 240 .

[0127] The third electrode 250 is formed separately for each pixel region and is connected to the second drain electrode 148 of the second driving transistor Td2 through the second drain contact hole 168.

[0128] The third electrode 250 may be an anode and may be made of a conductive material with a relatively high work function, such as a transparent conductive oxide (TCO). Specifically, the third electrode 250 may be made of one of indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc-oxide (ITZO), tin oxide (SnO), zinc oxide (ZnO), indium-copper-oxide (ICO), and aluminum:zinc oxide (Al:ZnO; AZO). That is, the third electrode 250 is a transparent electrode.

[0129] The third electrode 250 has an area larger than the second electrode 230 and the second organic light emitting layer 240. The third electrode 250 has an area larger than the second opening and may cover a portion of the top surface of the second bank 164.

[0130] The second organic light emitting diode D2 includes a second electrode 230, a second organic light emitting layer 240, and a third electrode 250 sequentially stacked on the second electrode 230. The second organic light emitting diode D2 is located in the red pixel region, the green pixel region, and the blue pixel region, respectively, and can emit red, green, and blue light, respectively. Alternatively, the second organic light emitting diode D2 can emit white light.

[0131] The second organic light emitting diode D2 has a larger area than the first organic light emitting diode D1 and can overlap with the first and second driving elements Td1 and Td2, so that the aperture ratio of the second organic light emitting diode D2 is not reduced by the first and second driving elements Td1 and Td2.

[0132] In other words, the first pixel driving circuit unit PDC1 including the first driving element Td1 and the second pixel driving circuit unit PDC2 including the second driving element Td2 are located on the first transparent substrate 110 in a first region of the pixel region P, and the first organic light emitting diode D1 is located on the first transparent substrate 110, for example, on the first and second pixel driving circuit units PDC1 and PDC2, in a second region of the pixel region P. Furthermore, the second organic light emitting diode D2 is located on the first organic light emitting diode D1 in the first and second regions of the pixel region P2.

[0133] Referring to FIG. 6, which is a schematic cross-sectional view of an organic light-emitting diode, the organic light-emitting diode included in the double-sided organic light-emitting display device of the present invention includes first and second organic light-emitting diodes D1 and D2 stacked together and sharing a second electrode 230.

[0134] The first organic light-emitting diode D1 includes a first electrode (210, lower electrode, first positive electrode), a second electrode (230, middle electrode, negative electrode) facing the first electrode 210, and a first organic light-emitting layer 220 located between the first and second electrodes 210 and 230. After holes from the first electrode 210 and electrons from the second electrode 230 are combined in the first organic light-emitting layer 220, light is emitted from the first organic light-emitting layer 220.

[0135] The first organic light emitting layer 220 includes a first light emitting material layer 226 located between the first electrode 210 and the second electrode 230 .

[0136] In addition, the first organic light-emitting layer 220 may further include a first hole transport layer 224 located between the first electrode 210 and the first light-emitting material layer 226, and a first electron transport layer 228 located between the first light-emitting material layer 226 and the second electrode 230.

[0137] In addition, the first organic light emitting layer 220 may further include a first hole injection layer 222 located between the first electrode 210 and the first hole transport layer 224 .

[0138] That is, the first organic light emitting diode D1 may have a structure in which a hole injection layer 222, a first hole transport layer 224, a first light emitting material layer 226, a first electron transport layer 228, and a second electrode 230 are sequentially stacked on a first electrode (210, first anode). order The organic light-emitting diode may have a normal structure.

[0139] The second organic light-emitting diode D2 includes a second electrode 230, a third electrode (250, upper electrode, second anode) facing the second electrode 230, and a second organic light-emitting layer 240 located between the second and third electrodes 230 and 250. After electrons from the second electrode 230 and holes from the third electrode 250 are combined in the second organic light-emitting layer 240, light is emitted from the second organic light-emitting layer 240.

[0140] The second organic light-emitting layer 240 includes a second light-emitting material layer 244 located between the second electrode 230 and the third electrode 250 .

[0141] In addition, the second organic light-emitting layer 240 may further include a second electron transport layer 242 located between the second electrode 230 and the second light-emitting material layer 244, and a second hole transport layer 246 located between the second light-emitting material layer 244 and the third electrode 250.

[0142] In addition, the second organic light-emitting layer may further include a second hole-injection layer 248 located between the third electrode 250 and the second hole-transport layer 246 .

[0143] That is, the second organic light emitting diode D2 may have a structure in which a second electron transport layer 242, a second light emitting material layer 244, a second hole transport layer 246, a second hole injection layer 248, and a third electrode 250 are sequentially stacked on a second electrode (230, negative electrode). The second organic light emitting diode D2 may be an organic light emitting diode with an inverted structure.

[0144] 5, a protective layer 170 is formed on the third electrode 250. For example, the protective layer 170 may be made of an inorganic insulating material.

[0145] In addition, a sealing layer 180 is formed on the protective layer 170. The sealing layer 180 may be made of an organic insulating material.

[0146] The protective layer 170 and the sealing layer 180 can prevent external moisture from penetrating into the first and second organic light emitting diodes D1 and D2.

[0147] The second transparent substrate 190 is disposed on the sealing layer 180. For example, the sealing layer 180 may have adhesive properties so that the second transparent substrate 190 can be attached to the protective layer 170 by the sealing layer 180.

[0148] The double-sided OLED display 100 may include color filter layers (not shown) corresponding to the red, green, and blue pixel regions. The color filter layers may include red, green, and blue color filters corresponding to the red, green, and blue pixel regions, respectively. When the double-sided OLED display 100 includes color filter layers, the color purity of the OLED display 100 may be improved. Furthermore, when the first and second OLEDs D1 and D2 are white OLEDs, a full-color image may be realized by the color filter layers.

[0149] For example, a first color filter layer may be located between the first transparent substrate 110 and the first organic light emitting diode D1, and a second color filter layer may be located between the second organic light emitting diode D2 and the second transparent substrate 190.

[0150] The double-sided OLED display 100 may further include a polarizer (not shown) to reduce reflection of external light. The polarizer may be a circular polarizer. For example, a first polarizer may be disposed on the outer side of the first transparent substrate 110, and a second polarizer may be disposed on the outer side of the second transparent substrate 190.

[0151] As described above, in the double-sided OLED display device 100 of the present invention, the first OLED D1 and the second OLED D2 are driven independently while sharing the negative second electrode 230. The first OLED D1 displays a first image through the first electrode 210, and the second OLED D2 displays a second image through the third electrode 250.

[0152] In addition, the second organic light emitting diode D2 has a relatively large aperture, which improves the energy efficiency and lifespan of the second organic light emitting diode D2.

[0153] In addition, since the second electrode 230, which is a negative electrode, can be formed of a metal material having excellent conductivity and high reflectivity, the light emitting efficiency (brightness) of the double sided OLED display 100 can be improved.

[0154] FIG. 7 is a schematic plan view of a pixel region structure in a double-sided organic light emitting display device according to a second embodiment of the present invention.

[0155] As shown in FIG. 7, the double-sided organic light emitting display device 300 includes a gate line GL, a low-level voltage line Vss, a first high-level voltage line Vdd1, a second high-level voltage line Vdd2, a first data line DL1, a second data line DL2, a first driving element (Td1 in FIG. 1), a second driving element (Td2 in FIG. 1), a first organic light emitting diode D1, and a second organic light emitting diode D2.

[0156] The gate line GL, the low-level voltage line Vss, the first high-level voltage line Vdd1, and the second high-level voltage line Vdd2 extend along a first direction (x), and the first data line DL1 and the second data line DL2 extend in a second direction (y) that intersects with the first direction (x). For example, the second direction (y) may be perpendicular to the first direction (x).

[0157] The first driving device Td1 is connected to the first high-level voltage wiring Vdd1, and the second driving device Td2 is connected to the second high-level voltage wiring Vdd2.

[0158] The first organic light emitting diode D1 is connected to the first driving element Td1 and the low-level voltage line Vss, and the second organic light emitting diode D2 is connected to the second driving element Td2 and the low-level voltage line Vss.

[0159] In addition, the double-sided organic light emitting display device 300 may further include a first switching element (Ts1 in FIG. 1) connected to the gate line GL, the first data line DL, and the first driving element Td1, and a second switching element (Ts2 in FIG. 1) connected to the gate line GL, the second data line DL, and the second driving element Td2.

[0160] The gate line GL, the second high-level voltage line Vdd2, the first high-level voltage line Vdd1, and the low-level voltage line Vss may be sequentially arranged at regular intervals along the second direction (y), and the first data line DL1 and the second data line DL2 may be sequentially arranged at regular intervals along the first direction (x).

[0161] The first data line DL1 and the second data line DL2 intersect with the gate line GL to define pixel regions P, and the first switching element Ts1, the second switching element Ts2, the first driving element Td1, the second driving element Td2, the first organic light-emitting diode D1, and the second organic light-emitting diode D2 are arranged in each pixel region P.

[0162] The first organic light emitting diode D1 includes a first electrode 410 which is an anode, a first organic light emitting layer, and a second electrode 430 which is an anode, and the second organic light emitting diode D2 includes a second electrode 430 which is an anode, a second organic light emitting layer, and a third electrode 450 which is an anode. That is, the second organic light emitting diode D2 is located above the first organic light emitting diode D1, sharing the second electrode 430 which is an anode with the first organic light emitting diode D1.

[0163] The first organic light emitting diode D1 and the second organic light emitting diode D2 share the negative second electrode 430. The first organic light emitting diode D1 is driven by the first driving element Td1, and the second organic light emitting diode D2 is driven by the second driving element Td2. That is, the first organic light emitting diode D1 and the second organic light emitting diode D2 are driven independently.

[0164] The first organic light emitting diode D1 is located in an area surrounded by the first data line DL1, the second data line DL2, the low-level voltage line Vss, and the first high-level voltage line Vdd1, and the second organic light emitting diode D2 has a larger planar area than the first organic light emitting diode D1. For example, one end of the second organic light emitting diode D2 may overlap the low-level voltage line Vss and the other end may be located beyond the second high-level voltage line Vdd2. For example, the other end of the second organic light emitting diode D2 may overlap the gate line GL.

[0165] That is, the first organic light emitting diode D1 does not overlap with the gate line GL, the first and second data lines DL1 and DL2, the low-level voltage line Vss, and the first and second high-level voltage lines Vdd1 and Vdd2, while the second organic light emitting diode D2 may overlap with the gate line GL, the first and second data lines DL1 and DL2, the low-level voltage line Vss, and the first and second high-level voltage lines Vdd1 and Vdd2.

[0166] The first organic light emitting diode D1 emits light in a first normal direction relative to the first direction (x) and the second direction (y), and the second organic light emitting diode D2 emits light in a second normal direction opposite to the first normal direction.

[0167] Therefore, the double-sided organic light emitting display device 100 of the present invention can realize a double-sided image display in which a first image is displayed in a first normal direction and a second image is displayed in a second normal direction.

[0168] FIG. 8 is a cross-sectional view taken along line II-II' in FIG.

[0169] As shown in FIG. 8, a first driving element Td1, a second driving element Td2, a first organic light emitting diode D1, and a second organic light emitting diode D2 are formed on a first transparent substrate 310 in which a pixel region is defined.

[0170] In addition, a protective layer 370 covering the second organic light emitting diode D2, a sealing layer 380 on the protective layer 370, and a second transparent substrate 390 on the sealing layer 380 may be provided on the second organic light emitting diode D2.

[0171] Each of the first and second transparent substrates 310 and 390 may be a glass substrate or a flexible substrate, for example, a polyimide (PI) substrate, a polyethersulfone (PES) substrate, a polyethylenenaphthalate (PEN) substrate, a polyethyleneterephthalate (PET) substrate, or a polycarbonate (PC) substrate.

[0172] A buffer layer 312 is formed on the first transparent substrate 310, and the first driving element Td1 and the second driving element Td2 are formed on the buffer layer 312. For example, the buffer layer 312 may be made of an inorganic insulating material such as silicon nitride. The buffer layer 312 may be omitted, in which case the first driving element Td1 and the second driving element Td2 may be formed on the first transparent substrate 310.

[0173] A first semiconductor layer 320 and a second semiconductor layer 322 are formed on the buffer layer 312. For example, the first semiconductor layer 320 and the second semiconductor layer 322 may each be made of an oxide semiconductor material. When the first semiconductor layer 320 and the second semiconductor layer 322 are each made of an oxide semiconductor material, a light-shielding pattern (not shown) may be formed below the first semiconductor layer 320 and the second semiconductor layer 322. The light-shielding pattern prevents light from being incident on the first semiconductor layer 320 and the second semiconductor layer 322, thereby preventing the first semiconductor layer 320 and the second semiconductor layer 322 from being deteriorated by light.

[0174] Alternatively, the first semiconductor layer 320 and the second semiconductor layer 322 may each be made of polycrystalline silicon, in which case both ends of the first semiconductor layer 320 and the second semiconductor layer 322 may be doped with impurities.

[0175] A gate insulating layer 324 made of an insulating material is formed on the first semiconductor layer 320 and the second semiconductor layer 322 on the front surface of the first transparent substrate 310. The gate insulating layer 324 may be made of an inorganic insulating material such as silicon oxide (SiOx) or silicon nitride (SiNx).

[0176] A first gate electrode 326 and a second gate electrode 328 made of a conductive material such as metal are formed on the gate insulating film 324. The first gate electrode 326 corresponds to the center of the first semiconductor layer 320, and the second gate electrode 328 corresponds to the center of the second semiconductor layer 322.

[0177] In addition, a gate line GL, a low-level voltage line Vss, a first high-level voltage line Vdd1, and a second high-level voltage line Vdd2 are formed on the gate insulating film 324. For example, the first high-level voltage line Vdd1 and the second high-level voltage line Vdd2 may be located between the first gate electrode 326 and the second gate electrode 328.

[0178] For example, the first gate electrode 326, the second gate electrode 328, the gate line GL, the low-level voltage line Vss, the first high-level voltage line Vdd1, and the second high-level voltage line Vdd2 may be made of the same material.

[0179] Although the gate insulating film 324 is formed on the front surface of the first transparent substrate 310 in FIG. 8, the gate insulating film 324 may be patterned in the same shape as the first gate electrode 326 and the second gate electrode 328, respectively.

[0180] An interlayer insulating film 330 made of an insulating material is formed on the front surface of the first transparent substrate 310 on the first gate electrode 326, the second gate electrode 328, the gate line GL, the low level voltage line Vss, the first high level voltage line Vdd1, and the second high level voltage line Vdd2. The interlayer insulating film 330 may be made of an inorganic insulating material such as silicon oxide or silicon nitride, or an organic insulating material such as benzocyclobutene or photo-acrylic.

[0181] The interlayer insulating film 330 has first and second semiconductor layer contact holes 332 and 334 exposing both upper surfaces of the first semiconductor layer 320 and third and fourth semiconductor layer contact holes 336 and 338 exposing both upper surfaces of the second semiconductor layer 322. The first and second semiconductor layer contact holes 332 and 334 are located on both sides of the first gate electrode 326 and spaced apart from the first gate electrode 326, and the third and fourth semiconductor layer contact holes 336 and 338 are located on both sides of the second gate electrode 328 and spaced apart from the second gate electrode 328.

[0182] 8, the first to fourth semiconductor layer contact holes 332, 334, 336, and 338 are formed in the interlayer insulating film 330 and the gate insulating film 324. Alternatively, if the gate insulating film 324 is patterned to have the same shape as the first and second gate electrodes 326 and 328, respectively, the first to fourth semiconductor layer contact holes 332, 334, 336, and 338 may be formed only in the interlayer insulating film 330.

[0183] A first source electrode 342, a first drain electrode 344, a second source electrode 346, and a second drain electrode 348 made of a conductive material such as metal are formed on the interlayer insulating film 330. The first source electrode 342 and the first drain electrode 344 are spaced apart around the first gate electrode 326 and contact both sides of the first semiconductor layer 320 through first and second semiconductor layer contact holes 332 and 334, respectively. The second source electrode 346 and the second drain electrode 348 are spaced apart around the second gate electrode 328 and contact both sides of the second semiconductor layer 322 through third and fourth semiconductor layer contact holes 336 and 338, respectively.

[0184] The first semiconductor layer 320, the first gate electrode 326, the first source electrode 342, and the first drain electrode 344 form a first driving element Td1, and the second semiconductor layer 322, the second gate electrode 328, the second source electrode 346, and the second drain electrode 348 form a second driving element Td2. Each of the first and second driving elements may be a thin film transistor (TFT).

[0185] 8, a first gate electrode 326, a first source electrode 342, and a first drain electrode 344 are located on the first semiconductor layer 320, and a second gate electrode 328, a second source electrode 346, and a second drain electrode 348 are located on the second semiconductor layer 322. That is, the first driving device Td1 and the second driving device Td2 each have a coplanar structure.

[0186] Alternatively, the first and second driving transistors Td1 and Td2 may each have a gate electrode located below a semiconductor layer and a source electrode and a drain electrode located above the semiconductor layer. That is, the first and second driving transistors Td1 and Td2 may each have an inverted staggered structure. In this case, the semiconductor layer may be made of amorphous silicon.

[0187] In addition, a first data line DL1 and a second data line DL2 are formed on the interlayer insulating film 330. The first data line DL1 and the second data line DL2 may be made of the same material as the first source electrode 342.

[0188] The first high-level voltage wiring Vdd1 is connected to the first source electrode 342. For example, a first contact hole exposing the first high-level voltage wiring Vdd1 may be formed in the interlayer insulating film 330, and the first source electrode 342 may be connected to the first high-level voltage wiring Vdd1 through the first contact hole. The second high-level voltage wiring Vdd2 is connected to the second source electrode 346. For example, a second contact hole exposing the second high-level voltage wiring Vdd2 may be formed in the interlayer insulating film 330, and the second source electrode 346 may be connected to the second high-level voltage wiring Vdd2 through the second contact hole.

[0189] Each pixel region P further includes a first switching element Ts1 connected to the gate line GL and the first data line DL1, and a second switching element Ts2 connected to the gate line GL and the second data line DL2. The first and second switching elements Ts1 and Ts2 may be thin film transistors. The first switching element Ts1 is connected to the first driving element Td1, and the second switching element Ts2 is connected to the second driving element Td2.

[0190] For example, the first switching element Ts1 may include a semiconductor layer, a gate electrode, a source electrode, and a drain electrode, the gate electrode may be connected to the gate line GL, the source electrode may be connected to the first data line DL1, and the drain electrode may be connected to the first drain electrode 344 of the first driving element Td1.

[0191] The second switching element Ts2 may include a semiconductor layer, a gate electrode, a source electrode, and a drain electrode, the gate electrode may be connected to the gate line GL, the source electrode may be connected to the second data line DL2, and the drain electrode may be connected to the second drain electrode 348 of the second driving element Td2.

[0192] In addition, each pixel region P may further include a first storage capacitor Cst1 for maintaining the voltage of the first gate electrode 326 of the first driving element Td1 constant during one frame, and a second storage capacitor Cst2 for maintaining the voltage of the second gate electrode 328 of the second driving element Td2 constant.

[0193] A planarization layer 350 is formed on the front surface of the first transparent substrate 310 on the first source electrode 342, the first drain electrode 344, the second source electrode 346, the second drain electrode 348, the first data line DL1, and the second data line DL2. The planarization layer 350 has a flat top surface and has a first drain contact hole 352 exposing the first drain electrode 344 of the first driving element Td1.

[0194] The first electrodes 410 are formed on the planarization layer 350, separated for each pixel region P. The first electrodes 410 are connected to the first drain electrodes 344 of the first driving transistors Td1 through first drain contact holes 352.

[0195] The first electrode 410 may be an anode and may be made of a conductive material with a relatively high work function, such as a transparent conductive oxide (TCO). Specifically, the first electrode 410 may be made of one of indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc-oxide (ITZO), tin oxide (SnO), zinc oxide (ZnO), indium-copper-oxide (ICO), and aluminum:zinc oxide (Al:ZnO; AZO). That is, the first electrode 410 is a transparent electrode.

[0196] The first electrode 410 has an area smaller than the pixel area P. For example, the first electrode 410 may be located within an area defined by the first data line DL1, the second data line DL2, the low-level voltage line Vss, and the first high-level voltage line Vdd1.

[0197] A bank layer 360 is formed on the planarization layer 350 to cover the edges of the first electrodes 410. The bank layer 360 includes a first bank 362 having a first thickness and a second bank 364 having a second thickness greater than the first thickness. For example, the first bank 362 has a first height from the first transparent substrate 310, and the second bank 364 has a second height from the first transparent substrate 310 that is greater than the first height.

[0198] The bank layer 360 includes a first opening op1 corresponding to the first electrode 410 and a second opening op2 having an area larger than the first opening op1 and corresponding to the pixel region P. That is, the first bank 362 has the first opening op1 exposing the center of the first electrode 410, and the second bank 364 has the second opening op2 corresponding to the pixel region P.

[0199] A common contact hole 366 exposing the low-level voltage line Vss and a second drain contact hole 368 exposing the second drain electrode 348 of the second driving element Td2 are formed through the bank layer 360, the planarization layer 350, and the interlayer insulating film 330.

[0200] A first organic light-emitting layer 420 is formed on the first electrode 410. The first organic light-emitting layer 420 may have a single-layer structure of a first light-emitting material layer, or may have a multi-layer structure further including at least one of a hole-injection layer, a hole-transport layer, an electron-blocking layer, a hole-blocking layer, an electron-transport layer, and an electron-injection layer.

[0201] Alternatively, the first organic light emitting layer 420 may include two or more light emitting material layers spaced apart from each other, which may be light emitting material layers of the same color or different colors.

[0202] At least a portion of the first organic light-emitting layer 420 may be formed by a solution process. For example, the first organic light-emitting layer 420 may be formed by an inkjet process or a spin coating process. Alternatively, the first organic light-emitting layer 420 may be formed by a deposition process. In FIG. 8, the first organic light-emitting layer 420 is formed by a deposition process, and the edge of the first organic light-emitting layer 420 covers a portion of the top surface of the first bank 362.

[0203] A second electrode 430 is formed on the first transparent substrate 310 on which the first organic light emitting layer 420 and the bank layer 360 are formed. The second electrode 430 is connected to a low-level voltage line Vss through a common contact hole 366.

[0204] The second electrode 430 may be separated for each pixel region. Alternatively, the second electrode 430 of a first pixel region may be integrally formed with the second electrode of a second pixel region adjacent to the first pixel region across the low-level voltage line Vss.

[0205] The second electrode 430 is located on the first organic light-emitting layer 420 at the first opening op1, and on the first bank 362 at the second opening op2. That is, the second electrode 430 has a larger area than the first electrode 410 and the first organic light-emitting layer 420. The area of ​​the second electrode 430 may be the same as the area of ​​the second opening op2.

[0206] The second electrode 430 may be made of a conductive material with a relatively low work function and used as a cathode. For example, the second electrode 430 may be made of a material with high conductivity and high reflectivity, such as aluminum (Al), magnesium (Mg), calcium (Ca), silver (Ag), or an alloy or combination thereof. In other words, the second electrode 430 is a reflective electrode.

[0207] That is, the first organic light emitting diode D1 is disposed on the planarization layer 350 and includes a first electrode 410, a first organic light emitting layer 420, and a second electrode 430 sequentially stacked on the first electrode 410. The first organic light emitting diode D1 is disposed in the red pixel region, the green pixel region, and the blue pixel region, respectively, and can emit red, green, and blue light, respectively. Alternatively, the first organic light emitting diode D1 can emit white light.

[0208] A second organic light-emitting layer 440 is formed on the second electrode 430. The second organic light-emitting layer 440 has substantially the same area as the second electrode 430. The edge of the second electrode 430 may be covered by the second organic light-emitting layer 440.

[0209] The first organic light-emitting layer 420 may emit light in a first wavelength range, and the second organic light-emitting layer 440 may emit light in a second wavelength range that may be the same as or different from the first wavelength. For example, the light in the first wavelength range and the light in the second wavelength range may each be one of red, green, and blue light.

[0210] The second organic light-emitting layer 440 may have a single-layer structure of a second light-emitting material layer, or may have a multi-layer structure by further including at least one of a hole-injecting layer, a hole-transporting layer, an electron-blocking layer, a hole-blocking layer, an electron-transporting layer, and an electron-injecting layer.

[0211] Alternatively, the second organic light-emitting layer 440 may include two or more light-emitting material layers spaced apart from each other, which may be light-emitting material layers of the same color or different colors.

[0212] At least a portion of the second organic light-emitting layer 440 may be formed by a solution process. For example, the second organic light-emitting layer 440 may be formed by an inkjet process or a spin coating process. Alternatively, the second organic light-emitting layer 440 may be formed by a vapor deposition process. In FIG. 8, the second organic light-emitting layer 440 is formed by a vapor deposition process, and the edge of the second organic light-emitting layer 440 covers the edge of the second electrode 430 on the second bank 364.

[0213] A third electrode 450 is formed on the second organic light emitting layer 440 .

[0214] The third electrode 450 is formed separately for each pixel region and is connected to the second drain electrode 348 of the second driving transistor Td2 through a second drain contact hole 368.

[0215] The third electrode 450 may be an anode and may be made of a conductive material with a relatively large work function, such as a transparent conductive oxide (TCO). Specifically, the third electrode 450 may be made of one of indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc-oxide (ITZO), tin oxide (SnO), zinc oxide (ZnO), indium-copper-oxide (ICO), and aluminum:zinc oxide (Al:ZnO; AZO). That is, the third electrode 450 is a transparent electrode.

[0216] The third electrode 450 has an area larger than the second electrode 430 and the second organic light emitting layer 440. The third electrode 450 has an area larger than the second opening and may cover a portion of the top surface of the second bank 364.

[0217] The second organic light emitting diode D2 includes a second electrode 430, a second organic light emitting layer 440, and a third electrode 450 sequentially stacked on the second electrode 430. The second organic light emitting diode D2 is located in the red pixel region, the green pixel region, and the blue pixel region, respectively, and can emit red, green, and blue light, respectively. Alternatively, the second organic light emitting diode D2 can emit white light.

[0218] The second organic light emitting diode D2 has a larger area than the first organic light emitting diode D1 and can overlap with the first and second driving elements Td1 and Td2, so that the aperture ratio of the second organic light emitting diode D2 is not reduced by the first and second driving elements Td1 and Td2.

[0219] In other words, the first pixel driving circuit unit PDC1 including the first driving element Td1 and the second pixel driving circuit unit PDC2 including the second driving element Td2 are located on the first transparent substrate 310 in a first region of the pixel region P, and the first organic light emitting diode D1 is located on the first transparent substrate 310, for example, on the first and second pixel driving circuit units PDC1 and PDC2, in a second region of the pixel region P. Furthermore, the second organic light emitting diode D2 is located on the first organic light emitting diode D1 in the first and second regions of the pixel region P2.

[0220] Referring to FIG. 6, the first organic light emitting layer 420 of the first organic light emitting diode D1 may have a structure in which a hole injection layer 222, a first hole transport layer 224, a first light emitting material layer 226, a first electron transport layer 228, and a second electrode 230 are sequentially stacked, and the second organic light emitting layer 440 of the second organic light emitting diode D2 may have a structure in which a second electron transport layer 242, a second light emitting material layer 244, a second hole transport layer 246, and a second hole injection layer 248 are sequentially stacked.

[0221] 8, a protective layer 370 is formed on the third electrode 450. For example, the protective layer 370 may be made of an inorganic insulating material.

[0222] A sealing layer 380 is formed on the protective layer 370. The sealing layer 380 may be made of an organic insulating material.

[0223] The protective layer 370 and the sealing layer 380 can prevent external moisture from penetrating into the first and second organic light emitting diodes D1 and D2.

[0224] The second transparent substrate 390 is disposed on the sealing layer 380. For example, the sealing layer 380 may have adhesive properties so that the second transparent substrate 390 can be attached to the protective layer 370 by the sealing layer 380.

[0225] The double-sided organic light-emitting display device 300 may include color filter layers (not shown) corresponding to the red, green, and blue pixel regions. The color filter layers may include red, green, and blue color filters corresponding to the red, green, and blue pixel regions, respectively. When the double-sided organic light-emitting display device 300 includes color filter layers, the color purity of the organic light-emitting display device 300 may be improved. Furthermore, when the first and second organic light-emitting diodes D1 and D2 are white organic light-emitting diodes, a full-color image may be realized by the color filter layers.

[0226] For example, a first color filter layer may be located between the first transparent substrate 310 and the first organic light emitting diode D1, and a second color filter layer may be located between the second organic light emitting diode D2 and the second transparent substrate 390.

[0227] The double-sided OLED display 300 may further include a polarizer (not shown) to reduce reflection of external light. The polarizer may be a circular polarizer. For example, a first polarizer may be disposed on the outer side of the first transparent substrate 310, and a second polarizer may be disposed on the outer side of the second transparent substrate 390.

[0228] As described above, in the double-sided OLED display device 300 of the present invention, the first OLED D1 and the second OLED D2 are independently driven while sharing the negative second electrode 430. The first OLED D1 displays a first image through the first electrode 410, and the second OLED D2 displays a second image through the third electrode 450.

[0229] In addition, the second organic light emitting diode D2 has a relatively large aperture, which improves the energy efficiency and lifespan of the second organic light emitting diode D2.

[0230] In addition, since the second electrode 430, which is a negative electrode, can be formed of a metal material having excellent conductivity and high reflectivity, the light emitting efficiency (brightness) of the double sided OLED display device 300 can be improved.

[0231] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. [Explanation of symbols]

[0232] 100, 300: Double-sided organic light-emitting display device D1: First organic light-emitting diode D2: second organic light-emitting diode Td1: First driving element Td2: second driving element Ts1: first switching element Tds2: second switching element GL: Gate wiring DL1: First data line DL2: Second data line Vss: Low level voltage wiring Vdd1: First high voltage wiring Vdd2: Second high voltage wiring 110, 310: First transparent substrate 190, 390: Second transparent substrate 210, 410: 1st electrode 220, 420: first organic light-emitting layer 230, 430: 2nd electrode 240, 440: second organic light-emitting layer 250, 450: 3rd electrode

Claims

1. a first transparent substrate including a pixel region including a first region and a second region; a gate wiring extending in a third direction; a first data wiring and a second data wiring extending in a fourth direction intersecting the third direction; a first switching element connected to the gate line and the first data line; a second switching element connected to the gate line and the second data line; a first driving element and a second driving element positioned above the first transparent substrate in the first region; a first high-level voltage wiring connected to the first driving element; a second high-level voltage wiring connected to the second driving element; a first organic light emitting diode located above the first and second driving elements in the second region, the first organic light emitting diode including a first electrode connected to the first driving element, a first organic light emitting layer facing the first electrode and stacked on the first electrode, and a second electrode stacked on the first organic light emitting layer; a second organic light emitting diode located above the first organic light emitting diode in the first and second regions, the second organic light emitting diode including a second organic light emitting layer facing the second electrode and stacked on the second electrode, and a third electrode stacked on the second organic light emitting layer and connected to the second driving element; a low-level voltage wiring connected to the second electrode; a common contact hole exposing the low-level voltage wiring and disposed on one side of the pixel area; a drain contact hole exposing a portion of the second driving element and disposed on the other side of the pixel area; the first organic light emitting diode and the second organic light emitting diode are stacked while sharing the second electrode; a first light from the first organic light emitting diode is emitted in a first direction through the first electrode, and a second light from the second organic light emitting diode is emitted in a second direction opposite to the first direction through the third electrode; the second electrode is connected to the low-level voltage wiring through the common contact hole, and the third electrode is connected to the second driving element through the drain contact hole; the first organic light emitting diode and the second organic light emitting diode are disposed between the common contact hole and the drain contact hole; the first driving element is connected to the first switching element, and the second driving element is connected to the second switching element; the first data wiring is disposed below the second organic light emitting diode and between the low-level voltage wiring and the second data wiring; the second data wiring is disposed below the second organic light emitting diode and between the first driving element and the second driving element; the first high-level voltage wiring is disposed below the second organic light-emitting diode and between the first driving element and the second data wiring; the second driving element is disposed between the second data wiring and the second high-level voltage wiring; the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring extend along the first data wiring and the second data wiring, and are arranged in the same layer as the first data wiring and the second data wiring; Double-sided organic light-emitting display.

2. The double-sided organic light emitting display device of claim 1 , wherein the first driving element and the second driving element are positioned in the third direction from the first organic light emitting diode.

3. The double-sided organic light emitting display device of claim 1 , wherein the first organic light emitting diode is disposed in a space between the first data line and the first high-level voltage line.

4. 2. The double-sided organic light emitting display device of claim 1, wherein the first organic light emitting diode does not overlap with the gate wiring, the first data wiring, the second data wiring, the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring, and the second organic light emitting diode overlaps with the low-level voltage wiring, the first high-level voltage wiring, and the second high-level voltage wiring.

5. The double-sided organic light emitting display device of claim 1 , wherein the second organic light emitting diode has a larger area than the first organic light emitting diode.

6. The double-sided organic light emitting display device of claim 1 , wherein at least one of the first organic light emitting layer and the second organic light emitting layer is formed by a solution process.

7. The double-sided organic light emitting display device of claim 6 , wherein the first organic light emitting layer is formed by a solution process, and the second organic light emitting layer is formed by a deposition process.

8. The double-sided organic light emitting display device of claim 1 , wherein the first electrode and the third electrode are transparent electrodes, and the second electrode is a reflective electrode.

9. The double-sided organic light emitting display device according to claim 1 , wherein the first organic light emitting diode has a forward structure and the second organic light emitting diode has an inverted structure.

10. the first organic light-emitting layer includes a first light-emitting material layer, a first hole transport layer located between the first electrode and the first light-emitting material layer, and a first electron transport layer located between the first light-emitting material layer and the second electrode; 2. The double-sided organic light-emitting display device of claim 1, wherein the second organic light-emitting layer comprises a second light-emitting material layer, a second electron transport layer located between the second electrode and the second light-emitting material layer, and a second hole transport layer located between the second light-emitting material layer and the third electrode.

11. The double-sided organic light emitting display device of claim 1 , wherein the first light has a first wavelength range, the second light has a second wavelength range, and the first wavelength range and the second wavelength range are the same.

12. The double-sided organic light emitting display device of claim 1 , wherein the first light has a first wavelength range, and the second light has a second wavelength range, the first wavelength range and the second wavelength range being different from each other.

13. a bank layer covering an edge of the first electrode and including a first bank and a second bank on the first bank; the second electrode in the first region is disposed on the bank layer, and the second electrode in the second region is disposed on the first organic light-emitting layer; the first bank includes a first opening, and the second bank includes a second opening; the first opening exposes the first electrode, and the second opening exposes the pixel region; The double-sided organic light emitting display of claim 1 , wherein the first bank overlaps the second bank.

14. a protective layer on the third electrode; a sealing layer on the protective layer; The double-sided organic light-emitting display device of claim 1 , further comprising: a second transparent substrate on the sealing layer.

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