JP2009140847A - Organic light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light emitting device in which a driving voltage fills a pressure withstanding of a driving transistor and moreover a life of an organic EL element is kept for a long time. <P>SOLUTION: The organic light emitting device includes a base board 56 (57), a first organic light emitting portion 1 having in order a first electrode 11, a first organic light emitting layer and a second electrode 16 on the above base board, a third electrode 26 which is conducted in a voltage potential with the second electrode of the first organic light emitting portion, and a second organic light emitting portion having in order a second light emitting layer and a fourth electrode 21 on the third electrode. A direction of a current flowing in the first organic light emitting portion and a direction of a current flowing the second light emitting portion are in the opposite direction with each in a membrane thickness direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic light emitting device having an organic light emitting unit.

  The organic EL element is characterized by self-emission from a planar light emitting structure in which thin films are stacked. This organic EL element includes at least a light emitting layer made of an organic light emitting material. This organic EL element can emit light efficiently at a low voltage by increasing the number of functional layers of the organic compound layer (Applied Physics Letters, 51, 913, 87, 913, 65, 8910). The basic element configuration here is composed of an anode / hole transport layer / light emitting layer (a layer containing an organic light emitting material) / cathode. Thereafter, higher efficiency has been achieved by the configuration of anode / hole transport layer / light emitting layer / electron transport layer / cathode.

  FIG. 9 is a diagram showing a typical configuration of an organic EL element in which an organic compound layer including at least a light emitting layer containing an organic light emitting material is sandwiched between an anode and a cathode which are a pair of electrodes. 65 is a glass substrate, 64 is a transparent anode such as ITO, 63 is a hole transport layer, 62 is a light emitting layer, 61 is an electron transport layer, and 60 is a cathode.

  As shown in FIG. 10, by applying a positive voltage to the anode 70 side and a negative voltage to the cathode 66 side, holes 74 that have passed through the hole transport layer 69 and electrons 73 that have passed through the electron transport layer 67 emit light. The layer 68 forms excitons and emits light by recombination.

  Further, a blocking layer is provided between the light emitting layer and the electron transport layer to block carriers passing through the light emitting layer, or between the cathode and the electron transport layer so that carriers can be injected at a low voltage. A metal thin film is provided as an electron injection layer. As a result, attempts have been made to improve luminous efficiency.

These organic EL elements emit light by a drive unit as shown in FIG. In FIG. 11, the luminance signal V _sig is supplied during the period when the gate V _{g10 of Tr39} is asserted as shown in the timing chart of FIG. At the same time, the gate V _{g11 of the} drive Tr ₃₆ becomes the luminance signal V _sig . As a result, the drive Tr 36 causes a current to flow from the power source 35 to the organic EL element 37.

  However, the organic EL element is an element that emits light when a current is supplied by the driving unit shown in FIG. 11, and it is necessary to supply a large amount of current in order to obtain a panel with high luminance and good visibility.

  However, it is also known that the luminance of light emitted from an organic EL element decreases with time when a drive current is applied to cause the element to deteriorate.

  Here, an “organic EL light-emitting element and a light-emitting device using the same” shown in Patent Document 1 are listed in FIG. The illustrated organic EL (light emitting) element 45 includes a transparent electrode 41, an electrode 42 disposed orthogonal to the transparent electrode 41, and n (1 ≦ n ≦ 100) intermediate conductive layers 43. Further, an organic compound layer 44 including at least an organic light emitting layer is interposed between the transparent electrode 41 and the counter electrode 42 with an intermediate conductive layer 43 interposed therebetween. A light emitting device 40 is proposed in which the organic EL elements 45 are arranged one-dimensionally or two-dimensionally. With such a configuration, the scanning line current is suppressed, and a large and high-definition display can be realized.

  Patent Document 2 proposes a stacked type “organic electroluminescent element” in which light emitting units as shown in FIG.

  This proposed organic electroluminescent element (organic EL element) includes a plurality of light emitting units 48-1, 48-2. . . . 48-n. Each light emitting unit includes layers 49-1, 49-2. . . . 49-n. Accordingly, it is an object of the present invention to provide an organic EL element that increases current efficiency, has high luminance light emission, and has a long lifetime. In the organic EL element described in Patent Document 2, two light emitting units are connected in series. FIG. 15 shows an equivalent circuit diagram of an active element when light emitting units are connected in series as in Patent Document 2.

  Further, Patent Document 3 describes that "there is possible to prevent as much as possible the shortening of the lifetime of the EL element due to the accumulation of space charges in the EL element due to repeated current driving". . As a means for solving this problem, “having at least a hole transport layer and a light emitting layer between the anode and the cathode. In an EL display device that emits light by supplying a predetermined bias, it is provided between the anode and the cathode during the non-display period. Means for periodically eliminating the space charge accumulated in the device by applying a reverse bias is disclosed.

Japanese Patent Laid-Open No. 11-329748 JP 2003-45676 A Japanese Patent Laid-Open No. 2000-2629

  The organic EL elements proposed in Patent Document 1 and Patent Document 2 are intended to extend the lifetime of each element by stacking element structures in the same direction and increasing current efficiency.

  However, these elements are stacked in the same direction, and when these elements are driven by current, the drive voltage is increased approximately twice. For this reason, for example, when driving using a TFT or the like as a drive transistor, the required voltage is high, and the breakdown voltage of the drive transistor may be a problem.

  An object of the present invention is to provide an organic light emitting device in which the driving voltage satisfies the withstand voltage of the driving transistor and the lifetime of the organic EL element is maintained for a long time.

In view of the characteristics of the EL element as described above, the organic light-emitting device of the present invention is
A substrate,
A first organic light emitting unit having a first electrode, a first organic light emitting layer, and a second electrode in order on the substrate;
A second electrode having a third electrode electrically connected to the second electrode of the first organic light emitting unit, a second organic light emitting layer, and a fourth electrode in order on the third electrode;
In an organic light emitting device having
The direction of the current flowing through the first organic light emitting unit and the direction of the current flowing through the second organic light emitting unit are opposite to each other in the film thickness direction.

  According to the present invention, it is possible to provide an organic light-emitting device in which the drive voltage satisfies the withstand voltage of the drive transistor and the lifetime of the organic EL element is maintained for a long time.

(First embodiment)
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an equivalent circuit diagram of a light-emitting device shown for the first embodiment of the present invention. In FIG. 1, 1 is a first organic light emitting unit, 2 is a second organic light emitting unit, 35 is a power source, 36 is a driving transistor, 38 is a capacitor, and 39 is a switching transistor (hereinafter, the transistor is abbreviated as Tr).

In the first embodiment of the present invention, as shown in FIG. 1, two organic light emitting units, that is, a first organic light emitting unit 1 and a second organic light emitting unit 2 are arranged in parallel between a drive Tr 36 and a reference potential. It is connected. First, the luminance signal V _sig is supplied from the column data processing unit 58 during the period when the gate V _{g10 of the} switching Tr ₃₉ is asserted as shown in the timing chart of FIG. At the same time, the gate V _{g11 of the} drive Tr 36 becomes the luminance signal V _sig supplied from the column data processing unit 58. As a result, the drive Tr 36 causes a current to flow from the power source 35 to the first organic light emitting unit 1 and the second organic light emitting unit 2.

  In the present embodiment, the organic light emitting devices connected in series can be driven at a lower voltage than the case where the same luminance is obtained, and the withstand voltage of the drive Tr can be satisfied. Further, when obtaining the same luminance as the conventional example shown in FIG. 11, the current flowing through the first organic light emitting unit 1 or the second organic light emitting unit 2 is approximately half of the current flowing through the organic light emitting element 37. For this reason, it is possible to remarkably suppress a decrease in the luminance of the light emission due to the deterioration of the element that occurs with the light emission time while having the same luminance.

  As shown in FIG. 3, as the first organic light emitting unit 1, the first electrode 11, the first hole transporting layer 12, the first organic light emitting layer 13, the first electron transporting layer 14, the first on the substrate 10. An electron injection layer 15 and a second electrode (transparent electrode) 16 are sequentially stacked. In addition, as the second organic light emitting unit 2, the second electrode 16, the second electron injection layer 25, the second electron transport layer 24, and the second used as the first organic light emitting unit are formed on the first organic light emitting unit 1. An organic light emitting layer 23, a second hole transport layer 22, and a fourth electrode (transparent electrode) 21 are sequentially stacked. In the present embodiment, the first organic light emitting unit and the second organic light emitting unit also serve as the second electrode 16, but this is not restrictive. As will be described later, the second organic light emitting unit may include a third electrode, and the third electrode may be electrically connected to the second electrode of the first organic light emitting unit.

  A DC signal from the drive unit 17 is applied to the first electrode 11, and a DC signal from the drive unit 27 is applied to the fourth electrode 21. The second electrode 16 is supplied with a reference potential (ground potential). That is, the direction of the current flowing through the first organic light emitting unit 1 and the direction of the current flowing through the second organic light emitting unit 2 are opposite to each other in the film thickness direction.

When an active matrix type display device is configured using the organic light emitting device of the present invention, a light emitting element in which a first organic light emitting unit 1 and a second organic light emitting unit 2 are stacked as shown in FIG. Separation by a separation membrane 53 is arranged in a matrix. Then, the voltage signal from the column data processing unit 58 is received by the first electrode 11 and the DC signal V _data1 from the driving unit 17 which is a TFT circuit in the pixel is driven to the fourth electrode 21 by the TFT circuit in the pixel. The DC signal V _data2 from the unit 27 is applied. A reference potential V ₃ is set for the second electrode 16 used in common for the two organic light emitting units.

  However, in the present embodiment, since the drive Tr 36 constituting the drive unit in FIG. 1 passes a current from the power source 35, the drive units 17 and 27 may be the same or any one of them.

  FIG. 5 is a schematic cross-sectional view of a display device using the organic light emitting device according to the embodiment of the invention. Here, the lower substrate 56 includes the driving unit 17 including a TFT circuit, and is connected to the first electrode 11. The upper substrate 57 includes a driving unit 27 made of a TFT circuit and is connected to the fourth electrode 21. The first organic light emitting unit 1 is laminated so as to face the first electrode 11, and the second organic light emitting unit 2 is laminated so as to face the fourth electrode 21. The second electrode 16 of each first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are connected by a conductor 52. In this embodiment, the second electrode 16 of the first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are formed separately, but the same film can be obtained by bringing the upper and lower organic light emitting units closer to each other. May be used as an electrode.

  In the organic light emitting device according to the present invention, each organic light emitting section is partitioned by a reference potential, and there are a plurality (two or more) of organic light emitting sections including one or more sets of organic light emitting sections in which the injection directions of electrons and holes are opposed. If it exists, the organic light emitting part may have any laminated structure. That is, the first electrode may be a cathode or an anode. When the first electrode is an anode, the second and third electrodes are cathodes and the fourth electrode is an anode. When the first electrode is a cathode, the second and third electrodes are anodes and the fourth electrode is a cathode. However, since it is necessary to extract light emitted from the light emitting layer from at least one of the substrate 10 and the opposite side, at least one of the first electrode 11 and the fourth electrode 21 needs to be a light transmitting electrode. . Moreover, in order to take out both light emission of a 1st organic light emission part and a 2nd organic light emission part, both electrodes need to be a light transmissive electrode. As the light transmissive electrode, a transparent metal oxide conductive member such as ITO or IZO or a metal thin film (thickness of about 10 nm to 20 nm) can be used.

There are no particular restrictions on the material used for the organic compound layer, that is, the organic light emitting layer, the hole transport layer, the hole injection layer, the electron transport layer, the electron injection layer, etc., and any material conventionally used for forming these layers may be used. It may be. There is no restriction | limiting in particular about the luminescent material used for an organic light emitting layer, A well-known material can be used, For example, various fluorescent materials, phosphorescent materials, etc. are mentioned. Examples of the material of each configuration include α-NPD as the hole transport layer, Alq3 as the organic light emitting layer, TAZ as the electron transport layer, and LiF as the electron injection layer. Note that Ir (ppy) _{3 and the} like are known as phosphorescent materials.

  Hereinafter, the manufacturing method will be described by taking the display device shown in FIG. 5 as an example.

  First, a method for manufacturing a lower light emitting substrate, that is, a member on which the first organic light emitting portion is formed will be described. The substrate 56 is deposited over a transparent and insulating substrate in a first process step, and the polysilicon layer is patterned into islands by photolithography. The substrate 56 is a crystalline material, but is preferably an inexpensive material such as low temperature glass. When a glass substrate is used, it is performed in a low temperature process in order to prevent melting or distortion of the glass in the TFT-EL manufacturing process and to avoid dopant diffusion in the active region. Accordingly, the manufacturing process for the glass substrate should be performed at 1000 ° C. or lower, preferably 600 ° C. or lower.

  Insulating gate material is then deposited over the polysilicon island and over the surface of the insulating substrate. The insulating material is silicon dioxide deposited by chemical vapor deposition (CVD) such as plasma enhanced CVD or low pressure CVD (LPCVD). The gate oxide insulating layer is a film having a thickness of about 1000 angstroms.

  In the next step, a layer of silicon is deposited on the gate insulating layer, and after ion implantation, source and drain regions are formed in the polysilicon region. For this reason, the source and drain regions are patterned by photolithography on the polysilicon island. The gate electrode material is polysilicon. The ion implant is made conductive with an N-type dopant, for example arsenic. The polysilicon gate electrode is also used as an electrode for a storage capacitor. A gate bus is applied and patterned on the insulating layer. The gate bus is preferably a metal silicide such as tungsten silicide.

  In the next step, an insulating layer of silicon dioxide is applied over the entire surface of the device.

  The contact hole penetrates through the second insulating layer, and the first electrode 11 is connected to the thin film transistor (TFT) circuit 17 through the contact hole. The electrode material applied to the source region of the TFT circuit 17 forms the upper surface electrode of the capacitor. The first electrode 11 is formed on silicon dioxide, which is an insulating material.

  In the next step, the tapered element isolation film 53 of the passivation layer is formed. The taper-shaped element isolation film 53 is necessary for manufacturing a reliable device. This is because the organic compound layer of the first organic light emitting unit 1 is made of a thin film having a thickness of about 200 nm. The passivation layer is about 1 micron thick. In addition, when the edge of the passivation layer forms a perpendicular or acute angle with respect to the first electrode 11, defects are likely to occur due to discontinuity of the coverage in the organic EL layer. In order to prevent defects, the passivation layer must have a tapered shape. Preferably, the passivation layer is tapered at an angle of 10 to 30 degrees with respect to the first electrode 11.

  The organic compound layer of the first organic light emitting unit 1 is deposited on the passivation layer and the first electrode 11. The compound that forms the organic compound layer of the first organic light emitting unit 1 is deposited by vapor deposition according to a known method, but may be deposited by a conventional technique such as other coating.

  Thereafter, the second electrode 16 is formed on the organic compound layer.

  Next, a method for manufacturing an upper light emitting substrate, that is, a member on which the second organic light emitting portion is formed will be described.

  The upper organic light emitting substrate is manufactured by the same manufacturing process as described above. The organic light emitting substrate includes a driving unit 27 made of a TFT circuit and is connected to the fourth electrode 21.

  Finally, bonding of the member on which the first organic light emitting unit 1 is formed and the member on which the second organic light emitting unit 2 is formed will be described. The member on which the first organic light emitting unit 1 is formed and the member on which the second organic light emitting unit 2 is formed are bonded together with the second electrode 16 and the third electrode 26 facing each other, and are fixed by a fixed seal 51 and are external atmosphere. More sealed. In addition, the second electrode 16 and the third electrode 26 formed on each organic light emitting unit are connected by a conductor 52.

(Second Embodiment)
Hereinafter, the second embodiment of the present invention will be described in detail with reference to the drawings.

  The layer configuration of the second embodiment of the present invention is the same as the configuration described in the first embodiment, and is the configuration shown in FIG.

Then, V _data1 shown in FIG. 6 is supplied from the driving unit 17 to the first electrode 11, and luminance signals having opposite phases are supplied to the fourth electrode 21 from the driving unit 27 with an alternating current of _Vdata2 . The second electrode 16 is given a potential that is ½ of the positive and negative peaks of the AC signal as a common potential. That is, a voltage for applying alternating currents having opposite phases to each other is supplied to the first electrode 11 and the fourth electrode 21, and the alternating current applied to the first electrode and the fourth electrode is applied to the second electrode 16. A voltage for applying a potential between the peak amplitudes of the potential is supplied.

When an active matrix type display device is configured using the organic light emitting device of the present invention, a light emitting element in which a first organic light emitting unit 1 and a second organic light emitting unit 2 are stacked as shown in FIG. Separation by a separation membrane 53 is arranged in a matrix. Then, the voltage data from the column data processing unit 58 is received by the first electrode 11, and the AC signal V _data1 from the driving unit 17 that is the TFT circuit in the pixel is driven to the fourth electrode 21 that is the TFT circuit in the pixel. The AC signal V _data2 from the unit 27 is applied to each. An intermediate potential V ₃ is set to the second electrode 16 that is also used as two organic light emitting units.

  FIG. 5 is a schematic cross-sectional view of a display device using the organic light emitting device according to the embodiment of the invention. Here, the lower substrate 56 includes the driving unit 17 including a TFT circuit, and is connected to the first electrode 11. The upper substrate 57 includes a driving unit 27 made of a TFT circuit and is connected to the fourth electrode 21. The first organic light emitting unit 1 is laminated so as to face the first electrode 11, and the second organic light emitting unit 2 is laminated so as to face the fourth electrode 21. Further, the second electrode 16 of the first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are connected by a conductor 52. In this embodiment, the second electrode 16 of the first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are formed separately, but the same film can be obtained by bringing the upper and lower organic light emitting units closer to each other. May be used as an electrode.

Here, the timing of the signals V _data1 and V _data2 of the driving units 17 and 27 in one pixel will be described with reference to FIG. First, at the timing period T ₁ is, V _data1 from the column data processing section 58 is supplied with + V _g level, V _data2 is supplied at -V _g level. In the subsequent timing T ₂ period, V _data1 is supplied from the column data processing unit 58 at the −V _g level, and V _data2 is supplied at the + V _g level. That is, in the second embodiment, V _data1 and V _data2 are driven with the same potential.

  With the above driving method, the driving voltage is applied to the first organic light emitting unit 1 and the second organic light emitting unit 2 from the individual first electrode 11 and the fourth electrode 21, respectively, so that the driving voltage can be kept low. For this reason, the withstand voltage of the drive Tr can be satisfied. Further, the driving time of the first organic light emitting unit 1 and the second organic light emitting unit 2 for obtaining the same luminance as that of the conventional example of FIG. Twice the life is obtained.

  Here, the first organic light emitting unit 1 and the second organic light emitting unit 2 are driven alternately, the first organic light emitting unit 1 has a positive potential for driving, and the undriven second organic light emitting unit 2 has Apply a bias that is the reverse of the display potential. In this case, a current flows from the first electrode 11 of the first organic light emitting unit 1 to the second electrode 16, and the first organic light emitting unit 1 emits light. At this time, a reverse voltage is applied to the fourth electrode 21 in the second organic light emitting unit 2 that does not contribute to light emission, and a reverse bias is applied to the third electrode 26. Thereby, since the space charge accumulated in the second organic light emitting unit 2 can be eliminated, the life of the display device 55 can be further extended.

  In the organic light emitting device according to the present invention, each organic light emitting section is partitioned by a reference potential, and there are a plurality (two or more) of organic light emitting sections including one or more sets of organic light emitting sections in which the injection directions of electrons and holes are opposed. If it exists, the organic light emitting part may have any laminated structure. That is, the first electrode may be a cathode or an anode. When the first electrode is an anode, the second and third electrodes are cathodes and the fourth electrode is an anode. When the first electrode is a cathode, the second and third electrodes are anodes and the fourth electrode is a cathode. However, since it is necessary to extract light emitted from the organic light emitting layer from at least one of the substrate 10 and the opposite side, at least one of the first electrode 11 and the fourth electrode 21 needs to be a light transmission electrode. is there. Moreover, in order to take out both light emission of a 1st organic light emission part and a 2nd organic light emission part, both electrodes need to be a light transmissive electrode. As the light transmissive electrode, a transparent metal oxide conductive member such as ITO or IZO, or a metal thin film (about 10 nm to 20 nm) can be used.

There are no particular restrictions on the material used for the organic compound layer, that is, the organic light emitting layer, the hole transport layer, the hole injection layer, the electron transport layer, the electron injection layer, and the like. It may be. There is no restriction | limiting in particular about the luminescent material used for an organic light emitting layer, A well-known material can be used, For example, various fluorescent materials, phosphorescent materials, etc. are mentioned. Examples of the material of each configuration include α-NPD as the hole transport layer, Alq3 as the organic light emitting layer, TAZ as the electron transport layer, and LiF as the electron injection layer. Note that Ir (ppy) _{3 and the} like are known as phosphorescent materials.

(Third embodiment)
Hereinafter, the third embodiment of the present invention will be described in detail with reference to the drawings.

  The layer configuration of the third embodiment of the present invention is the same as the configuration described in the first embodiment and the second embodiment, and is the configuration shown in FIG.

Then, V _data1 shown in FIG. 7 is supplied from the driving unit 17 to the first electrode 11, and luminance signals having opposite phases are supplied to the fourth electrode 21 from the driving unit 27 with an alternating current of _Vdata2 . The second electrode 16 is given a potential that is ½ of the positive and negative peaks of the AC signal as a common potential. That is, this embodiment also supplies the first electrode 11 and the fourth electrode 21 with voltages for applying alternating currents having opposite phases to each other, and the second electrode 16 has the first electrode and the fourth electrode connected to each other. A voltage for supplying a potential between the peak amplitudes of the applied AC potential is supplied.

When an active matrix type display device is configured using the organic light emitting device of the present invention, a light emitting element in which a first organic light emitting unit 1 and a second organic light emitting unit 2 are stacked as shown in FIG. Separation by a separation membrane 53 is arranged in a matrix. Then, the first electrode 11 receives the voltage data from the column data processing unit 58 and the AC signal V _data1 from the driving unit 17 which is a TFT circuit in the pixel is driven to the fourth electrode 21 which is a TFT circuit in the pixel. The AC signal V _data2 from the unit 27 is applied to each. An intermediate potential V ₃ is set to the second electrode 16 that is also used as two organic light emitting units.

  FIG. 5 is a schematic cross-sectional view of a display device using the organic light emitting device according to the embodiment of the invention. Here, the lower substrate 56 includes the driving unit 17 including a TFT circuit, and is connected to the first electrode 11. The upper substrate 57 includes a driving unit 27 made of a TFT circuit and is connected to the fourth electrode 21. The first organic light emitting unit 1 is laminated so as to face the first electrode 11, and the second organic light emitting unit 2 is laminated so as to face the fourth electrode 21. The second electrode 16 of each first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are connected by a conductor 52. In this embodiment, the second electrode 16 of the first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are formed separately, but the same film can be obtained by bringing the upper and lower organic light emitting units closer to each other. May be used as an electrode.

Here, the timing of the signals V _data1 and V _data2 of the driving units 17 and 27 for one pixel will be described with reference to FIG. First, at the timing period T ₁ is, V _data1 from the column data processing section 58 is supplied with ₊ V g_image level, V _data2 is supplied at -V _{G_text} level. In the subsequent timing T ₂ period, V _data1 is supplied from the column data processing unit 58 at the −V _{g_image} level, and V _data2 is supplied at the + V _{g_text} level.

In the timing T ₃ period and the timing T ₄ period, the T ₁ and T ₂ cycles and the data from the driving units 17 and 27 are inverted. In the timing period T _3, V _data1 from the column data processing section 58 is supplied with ₊ V g_text level, V _data2 is supplied at -V _{G_image} level. In the period of timing T ₄ , V _data1 is supplied from the column data processing unit 58 at the −V _{g_text} level, and V _data2 is supplied at the + V _{g_image} level.

In this _embodiment, V g_text a V _{G_image} the fixed pattern is a periodic change pattern is shared alternately displayed in the organic light-emitting portion 1 and the organic light emitting unit 2. V _{g_image} is a video data signal value, and V _{g_text} is a text data signal value.

  With the above-described driving method, the driving voltage is applied to the organic light emitting units 1 and 2 from the individual electrodes 11 and 21, respectively, and can be kept low. For this reason, the withstand voltage of the drive Tr can be satisfied. Further, the driving time of the organic light emitting units 1 and 2 for obtaining the same luminance as that of the conventional example of FIG. 11 is approximately half that of the light emitting element 37, and the display device 55 has a life that is approximately twice as long. . Further, since the space charge accumulated in the organic light emitting units 1 and 2 can be eliminated by the bias having the opposite polarity to the previous display luminance signal applied alternately, the lifetime of the display device 55 is expected to be further extended.

  An actual display image is shown in FIG. As described above, the first display pattern is displayed in the pixel matrix of the first organic light emitting unit 1, and the second display pattern is displayed in the pixel matrix of the second organic light emitting unit 2. The first display pattern and the second display pattern are alternately displayed and displayed as one image.

  With the above driving method, the driving voltage can satisfy the withstand voltage of the driving Tr.

  In the organic light emitting device according to the present invention, each organic light emitting section is partitioned by a reference potential, and there are a plurality (two or more) of organic light emitting sections including one or more sets of organic light emitting sections in which the injection directions of electrons and holes are opposed. If it exists, the organic light emitting part may have any laminated structure. That is, the first electrode may be a cathode or an anode. When the first electrode is an anode, the second and third electrodes are cathodes and the fourth electrode is an anode. When the first electrode is a cathode, the second and third electrodes are anodes and the fourth electrode is a cathode. However, since it is necessary to extract light emitted from the organic light emitting layer from at least one of the substrate 10 and the opposite side, at least one of the first electrode 11 and the fourth electrode 21 needs to be a light transmission electrode. is there. Moreover, in order to take out both light emission of a 1st organic light emission part and a 2nd organic light emission part, both electrodes need to be a light transmissive electrode. As the light transmissive electrode, a transparent metal oxide conductive member such as ITO or IZO, or a metal thin film (about 10 nm to 20 nm) can be used.

There are no particular restrictions on the material used for the organic compound layer, that is, the organic light emitting layer, the hole transport layer, the hole injection layer, the electron transport layer, the electron injection layer, etc., and any material conventionally used for forming these layers may be used. It may be. There is no restriction | limiting in particular about the luminescent material used for an organic light emitting layer, A well-known material can be used, For example, various fluorescent materials, phosphorescent materials, etc. are mentioned. Examples of the material of each configuration include α-NPD as the hole transport layer, Alq3 as the organic light emitting layer, TAZ as the electron transport layer, and LiF as the electron injection layer. Note that Ir (ppy) _{3 and the} like are known as phosphorescent materials.

(Fourth embodiment)
In the fourth embodiment of the present invention, the first organic light emitting unit and the second organic light emitting unit are configured by similar system colors, respectively. The chromaticity is CIE chromaticity coordinates, and both the organic light emitting unit 1 (0.145, 0.095) and the organic light emitting unit 2 (0.147, 0.139) emit blue light. No. 1 has better color purity. On the other hand, the half life is longer in the organic light emitting unit 2 than in the organic light emitting unit 1.

As shown in FIG. 1, two organic light emitting units, that is, a first organic light emitting unit 1 and a second organic light emitting unit 2 are connected in parallel between the drive Tr 36 and a reference potential. First, the luminance signal V _sig is supplied from the column data processing unit 58 during the period when the gate V _{g10 of the} switching Tr ₃₉ is asserted as shown in the timing chart of FIG. At the same time, the gate V _{g11 of the} drive Tr 36 becomes the luminance signal V _sig supplied from the column data processing unit 58. As a result, the drive Tr 36 causes a current to flow from the power source 35 to the first organic light emitting unit 1 and the second organic light emitting unit 2.

  In the present embodiment, the organic light emitting devices connected in series can be driven at a lower voltage than the case where the same luminance is obtained, and the withstand voltage of the drive Tr can be satisfied. In addition, when obtaining the same luminance as in the conventional example in FIG. 11, the current flowing through the first organic light emitting unit 1 or the second organic light emitting unit 2 is approximately half of the current flowing through the organic light emitting element 37. Therefore, it is possible to remarkably suppress a decrease in luminance of light emission due to deterioration of the element that occurs with the time of light emission while having the same luminance. In addition, the initial display color purity was worse than when the first organic light emitting unit of the organic light emitting device was displayed alone, and better than when the second organic light emitting unit was displayed alone. Here, it is clear that the deviation of the white balance due to drive deterioration is also improved by the above-described improvement of the lifetime.

  As shown in FIG. 3, as the first organic light emitting unit 1, the first electrode 11, the first hole transporting layer 12, the first organic light emitting layer 13, the first electron transporting layer 14, the first on the substrate 10. An electron injection layer 15 and a second electrode (transparent electrode) 16 are sequentially stacked. In addition, as the second organic light emitting unit 2, the second electrode 16, the second electron injection layer 25, the second electron transport layer 24, and the second used as the first organic light emitting unit are formed on the first organic light emitting unit 1. An organic light emitting layer 23, a second hole transport layer 22, and a fourth electrode (transparent electrode) 21 are sequentially stacked.

  A DC signal from the drive unit 17 is applied to the first electrode 11, and a DC signal from the drive unit 27 is applied to the fourth electrode 21. The second electrode 16 is supplied with a reference potential (ground potential).

When an active matrix type display device is configured using the organic light emitting device of the present invention, a light emitting element in which a first organic light emitting unit 1 and a second organic light emitting unit 2 are stacked as shown in FIG. Separation by a separation membrane 53 is arranged in a matrix. Then, the voltage signal from the column data processing unit 58 is received by the first electrode 11, and the DC signal V _data1 from the driving unit 17 that is the TFT circuit in the pixel is driven to the fourth electrode 21 by the TFT circuit in the pixel. The DC signal V _data2 from the unit 27 is applied. A reference potential V ₃ is set for the second electrode 16 used in common for the two organic light emitting units.

  However, in the present embodiment, since the drive Tr 36 constituting the drive unit in FIG. 1 passes a current from the power source 35, the drive units 17 and 27 may be the same or any one of them.

  FIG. 5 is a schematic cross-sectional view of a display device using the organic light emitting device according to the embodiment of the invention. Here, the lower substrate 56 includes the driving unit 17 including a TFT circuit, and is connected to the first electrode 11. The upper substrate 57 includes a driving unit 27 made of a TFT circuit and is connected to the fourth electrode 21. The first organic light emitting unit 1 is laminated so as to face the first electrode 11, and the second organic light emitting unit 2 is laminated so as to face the fourth electrode 21. The second electrode 16 of each first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are connected by a conductor 52. In this embodiment, the second electrode 16 of the first organic light emitting unit 1 and the third electrode 26 of the second organic light emitting unit 2 are formed separately, but the same film can be obtained by bringing the upper and lower organic light emitting units closer to each other. May be used as an electrode.

  In the organic light emitting device according to the present invention, each organic light emitting section is partitioned by a reference potential, and there are a plurality (two or more) of organic light emitting sections including one or more sets of organic light emitting sections in which the injection directions of electrons and holes are opposed. If it exists, the organic light emitting part may have any laminated structure. That is, the first electrode may be a cathode or an anode. When the first electrode is an anode, the second and third electrodes are cathodes and the fourth electrode is an anode. When the first electrode is a cathode, the second and third electrodes are anodes and the fourth electrode is a cathode. However, since it is necessary to extract light emitted from the organic light emitting layer from at least one of the substrate 10 and the opposite side, at least one of the first electrode 11 and the fourth electrode 21 needs to be a light transmission electrode. is there. Moreover, in order to take out both light emission of the 1st organic light emission part 1 and the 2nd organic light emission part 2, both electrodes need to be a light transmissive electrode. As the light transmissive electrode, a transparent metal oxide conductive member such as ITO or IZO, or a metal thin film (about 10 nm to 20 nm) can be used.

There are no particular restrictions on the material used for the organic compound layer, that is, the organic light emitting layer, the hole transport layer, the hole injection layer, the electron transport layer, the electron injection layer, etc., and any material conventionally used for forming these layers may be used. It may be. There is no restriction | limiting in particular about the luminescent material used for an organic light emitting layer, A well-known material can be used, For example, various fluorescent materials, phosphorescent materials, etc. are mentioned. Examples of the material of each configuration include α-NPD as the hole transport layer, Alq3 as the organic light emitting layer, TAZ as the electron transport layer, and LiF as the electron injection layer. Note that Ir (ppy) _{3 and the} like are known as phosphorescent materials.

It is an equivalent circuit diagram of the organic light emitting device of the present invention. It is a figure for demonstrating the signal supplied to the drive part of this invention, and its timing. It is a schematic diagram for demonstrating the cross section and drive part of the organic light-emitting device of this invention. It is a plane schematic diagram which shows the active matrix type display apparatus using the organic light-emitting device of this invention. It is a cross-sectional schematic diagram of the display apparatus using the organic light-emitting device of this invention. It is a figure for demonstrating the data signal supplied to the drive part which concerns on the 2nd Embodiment of this invention, and its timing. It is a figure for demonstrating the data signal supplied to the drive part which concerns on the 3rd Embodiment of this invention, and its timing. It is a figure which shows the display method which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the conventional organic EL element. It is a figure for demonstrating the light emission principle of the conventional organic EL element. It is an equivalent circuit diagram of a conventional organic light emitting device. It is a figure for demonstrating the signal supplied to the conventional drive part, and its timing. It is a figure for description of "the organic electroluminescent light emitting element and the light-emitting device using the same" disclosed by patent document 1. FIG. FIG. 11 is a diagram for explaining an “organic electroluminescent element” disclosed in Patent Document 2. It is an equivalent circuit diagram at the time of connecting two organic light emission parts in series.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st organic light emission part 2 2nd organic light emission part 10 Substrate 11 1st electrode 12 1st hole transport layer 13 1st organic light emission layer 14 1st electron transport layer 15 1st electron injection layer 16 2nd electrode 17 Drive part 21 4th electrode 22 2nd electron injection layer 23 2nd electron transport layer 24 2nd organic light emitting layer 25 2nd hole transport layer 26 3rd electrode 27 drive part 35 power supply 36 drive transistor 38 capacity 39 switching transistor 40 light emitting device 41 Transparent electrode 42 Counter electrode 43 Intermediate conductive layer 44 Organic compound layer 45 Organic EL light emitting element 51 Fixed seal 52 Conductor 53 Element separation layer 56 Substrate 57 Counter substrate 58 Column data processing unit 59 Scan control unit 60 Display control unit 61 Power supply

Claims (6)

A substrate,
A first organic light emitting unit having a first electrode, a first organic light emitting layer, and a second electrode in order on the substrate;
A second electrode having a third electrode electrically connected to the second electrode of the first organic light emitting unit, a second organic light emitting layer, and a fourth electrode in order on the third electrode;
In an organic light emitting device having
An organic light emitting device, wherein a direction of current flowing through the first organic light emitting unit and a direction of current flowing through the second organic light emitting unit are opposite to each other in the film thickness direction.   The current flowing through the first organic light emitting unit and the current flowing through the second organic light emitting unit are both direct current, and the first organic light emitting unit and the second organic light emitting unit are driven simultaneously. The organic light-emitting device according to claim 1.   The organic light emitting device according to claim 1, wherein the first organic light emitting unit and the second organic light emitting unit are driven alternately. Supplying a voltage for applying alternating currents of opposite phases to the first electrode and the fourth electrode;
The voltage for giving the electric potential between the peak amplitudes of the alternating current potential applied to the said 1st electrode and the said 3rd electrode is supplied to the said 2nd electrode and the said 3rd electrode. The organic light-emitting device described.   A first display pattern is displayed in the pixel matrix of the first organic light emitting unit, a second display pattern is displayed in the pixel matrix of the second organic light emitting unit, and the first display pattern and the second display are displayed. The organic light-emitting device according to claim 4, wherein the organic light-emitting device is displayed alternately with a pattern.   5. The organic light emitting device according to claim 2, wherein the light emitting layers of the first organic light emitting unit and the second organic light emitting unit are made of different organic light emitting materials.

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