JP2010010576A - Organic light emitting element array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light emitting element array whose driving voltage is low and exhibits an excellent picture, controlling leakage of current between adjacent sub-pixels. <P>SOLUTION: The organic light emitting element array 1 is constructed in such a manner that a plurality of sub-pixels, which have an organic light emitting element including at least an lower electrode 12, a charge injection layer (a first charge injection layer 13), and an upper electrode 18 in the shown order, are located on a substrate 11. The lower electrode 12 is adjacent to the charge injection layer 13, and the charge injection layer is formed on the sub-pixel in common. The organic light emitting element array 1 meets a relation of (formula 1) concerning an electric resistance of a part formed between the adjacent sub-pixels among the charge injection layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic light emitting element array having a plurality of organic light emitting elements.

  In recent years, research and development has been vigorously conducted on organic light-emitting elements, and area color type organic light-emitting element arrays in which colors such as single color, blue, and red are added have been commercialized. Currently, the development and commercialization of organic light-emitting element arrays for full color are being activated.

  An organic light emitting element constituting an organic light emitting element array is an electronic element in which a thin film made of an organic compound is provided between an anode and a cathode. An organic light-emitting element is an electronic element that injects holes and electrons from an anode and a cathode, respectively, and extracts energy generated when these holes and electrons recombine as light. Here, it is known that an organic light-emitting element can reduce drive voltage, improve light emission efficiency, improve stability, and the like by improving charge injection characteristics.

  Here, some specific proposals have already been proposed as means for improving the charge injection characteristics of the organic light emitting device. For example, Patent Document 1 discloses a technique for introducing a mixed layer made of a mixture of a metal oxide such as vanadium oxide, molybdenum oxide, rubidium oxide and the like and a hole transport material as a hole injection layer as a method for improving hole injection characteristics. ing. Patent Document 1 also shows that the introduced mixed layer has a low resistivity.

  On the other hand, it is well known that driving voltage can be reduced by introducing a mixed layer made of a mixture of an electron transport material and an alkali metal, an alkali metal salt or an alkali metal oxide as an electron injection layer. Patent Document 2 discloses a technique of introducing a mixed layer formed by mixing cesium carbonate and an electron transport material, which is easy to handle, as an electron injection layer as a technique that enables electrons to be injected from various metal electrodes. Has been.

JP 2006-024791 A JP 2005-183265 A

  By the way, when an element array is formed by incorporating a plurality of organic light emitting elements, the type of driving the organic light emitting elements is generally a simple matrix type or a TFT driving type.

  In addition, when performing multicolor or full color display using an organic light emitting element, it is realized by arranging organic light emitting elements that emit light of red, green, blue, etc. in an array. For example, in the case of a low molecular vapor deposition type organic light emitting device, it is realized by selectively depositing a light emitting layer for each pixel using a vapor deposition mask. Further, in the case of a coating type organic light emitting device, the light emitting layer is realized by selectively painting each pixel by printing or ink jet.

  On the other hand, the layers other than the light emitting layer are desirably formed in common between the sub-pixels forming the organic light emitting element, from the viewpoint of improving productivity and reducing production cost. However, if the charge injection layer disclosed in Patent Document 1, Patent Document 2, or the like is formed in common between subpixels, current leakage occurs between adjacent subpixels due to the low resistivity. There was a problem that light was emitted from other than the pixels and the image quality deteriorated.

  Similar to the light emitting layer, this problem can be avoided by selectively forming the charge injection layer in the subpixel region using a mask or the like. However, Cs compounds that are electron injection dopants, vanadium oxide and molybdenum oxides that are hole injection dopants have high sublimation temperatures, and the mask thermally expands due to the influence of radiant heat generated when sublimation occurs. For this reason, there has been a problem that it is difficult to selectively deposit the charge injection layer using a mask or the like.

  The present invention solves the above-described problems, and an object of the present invention is to provide an organic light-emitting element array that exhibits a good image quality with a low driving voltage while suppressing current leakage between adjacent sub-pixels.

In the organic light emitting device array of the present invention, a plurality of subpixels each having an organic light emitting device including at least a lower electrode, a charge injection layer, and an upper electrode in this order are disposed on a substrate.
The lower electrode is in contact with the charge injection layer;
The charge injection layer is formed in common to the sub-pixels;
The electrical resistance of the portion formed between adjacent subpixels in the charge injection layer satisfies the relationship of the following formula 1.

（式１において、Ｒ_CILは、隣接する副画素間に形成される電荷注入層が有する電気抵抗を表す。Ｖ_maxは、最大輝度時の駆動電圧を表す。Ｉ_maxは、最大輝度時に副画素に流れる電流を表す。Ｖ_leakは、最大輝度時に副画素に流れる電流（Ｉ_max）を流すのに必要な電圧を表す。Ｃは、得たいコントラストを表す。）

(In Equation 1, R _CIL represents the electrical resistance of the charge injection layer formed between adjacent sub-pixels. V _max represents the driving voltage at the maximum luminance. I _max represents the sub-pixel at the maximum luminance. (V _leak represents a voltage required to flow a current (I _max ) flowing through the sub-pixel at the maximum luminance. C represents a contrast to be obtained.)

  ADVANTAGE OF THE INVENTION According to this invention, the organic light emitting element array which has a low drive voltage and exhibits favorable image quality can be provided, suppressing the current leak between adjacent subpixels.

  In the organic light emitting element array of the present invention, a plurality of subpixels having organic light emitting elements each including at least a lower electrode, a charge injection layer, and an upper electrode in this order are arranged on a substrate.

  Hereinafter, the organic light-emitting element array of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of the organic light-emitting element array of the present invention. In the organic light-emitting element array 1 of FIG. 1, a pattern is formed on a base material 11 at a position where the lower electrode 12 is a sub-pixel. A pixel isolation film 19 for partitioning each lower electrode 12 is formed between the lower electrodes 12.

  A first charge injection layer 13 is formed above the lower electrode 12 and the pixel isolation film 19 so as to cover the lower electrode 12 and the pixel isolation film 19. A first charge transport layer 14 is formed on the first charge injection layer 13. On the first charge transport layer 14, the light emitting layer 15 is patterned at a position to be a sub-pixel. A second charge transport layer 16 is formed on the light emitting layer 15 so as to cover the light emitting layer 15 and the first charge transport layer 14. On the second charge transport layer 16, a second charge injection layer 17 and an upper electrode 18 are sequentially formed.

  In the organic light emitting device array of the present invention, at least a charge injection layer is commonly formed in each subpixel. Here, “commonly formed” means that the charge injection layer included in each sub-pixel is formed of a common thin film. In addition, the charge injection layer formed in common to each subpixel refers to the first charge injection layer 13 in the organic light emitting element array of FIG. 1, for example. Note that the commonly formed layer is not limited to the charge injection layer. For example, as in the organic light emitting device array 1 shown in FIG. 1, layers other than the light emitting layer 15 (first charge injection layer 13, first charge transport layer 14, second charge transport layer 16 and second charge injection layer 17). ) May be commonly formed in each sub-pixel. In the organic light emitting device array of the present invention, the lower electrode 11 is in contact with the charge injection layer (first charge injection layer 12) as shown in FIG.

  Hereinafter, the charge injection layer that is commonly formed in each sub-pixel will be described in more detail.

  The charge injection layer (first charge injection layer 13) formed in common to each sub-pixel shown in FIG. 1 is adjacent to the region formed in the sub-pixel, depending on the position where the layer is formed. It can be divided into regions formed between them. Here, with respect to the electrical resistance in the portion formed between adjacent sub-pixels, the following formula 1 is established.

In Equation 1, R _CIL represents the electrical resistance of the charge injection layer formed between adjacent subpixels.

In Equation 1, V _max represents a driving voltage at the maximum luminance.

In Equation 1, I _max represents a current flowing through the sub-pixel at the maximum luminance.

In Equation 1, V _leak represents a voltage necessary for flowing a current (I _max ) flowing through the sub-pixel at the maximum luminance.

  In Equation 1, C represents the contrast to be obtained.

  The parameter expressed by Equation 1 depends on the constituent material of the charge injection layer (first charge injection layer 13) and the film thickness of the layer.

  The significance of Equation 1 will be described with reference to the drawings. FIG. 2 is a diagram showing an equivalent circuit including two types of elements. The equivalent circuit of FIG. 2 is an equivalent circuit related to two adjacent elements (first element 21 and second element 22) when the anode is a drive power supply and the cathode is a common electrode. The first element 21 and the second element 22 shown in FIG. 2 are electrically connected via the resistor 23 on the anode side. Here, the resistor 23 shown in FIG. 2 corresponds to the commonly formed first charge injection layer 13 which is a constituent member of the organic light emitting element array of FIG.

  In the circuit shown in FIG. 2, the relationship of the following formula 2 is established.

In Equation 2, V ₁ represents a voltage applied to the first element 21.

In Equation 2, I _leak represents the magnitude of the current flowing to the second element 22 by the voltage applied to the first element 21.

In Equation 2, R _CIL represents the electrical resistance of the resistor 23 (the electrical resistance between the first element 21 and the second element 22 via the first charge injection layer).

In Equation 2, V ₂ represents a voltage applied to the second element 22.

FIG. 3 is a graph showing an example of current-voltage characteristics in the equivalent circuit of FIG. The graph of FIG. 3 shows that a current of 2 × 10 ⁻⁷ A flows when the voltage V ₁ is applied to the first element 21 included in the equivalent circuit of FIG. According to the graph of FIG. 3, when R _CIL = 100 MΩ, a current of about 1 × 10 ⁻⁸ A flows through the second element 22 corresponding to the adjacent pixel. This value is 1/20 of the current (drive current) flowing through the first element 21 when the voltage V ₁ is applied. When R _CIL = 100 MΩ, about 1/20 light emission is observed in the adjacent pixel (second element 22). On the other hand, when R _CIL = 4 GΩ, about 4 × 10 ⁻¹⁰ (A) flows through the second element 22. This value is 1/500 of the current flowing through the first element 21.

  When the current characteristics shown in FIG. 3 are shown, in order to obtain a contrast of 500: 1 (C = 500), the resistance between adjacent pixels needs to be at least 4 GΩ.

  In general, a higher contrast is required for a display element or an organic light emitting element array, but a factor for lowering the contrast varies depending on the use environment. For example, in the case of a display element or the like used in a dark place, slight light emission when the element is off becomes a problem. On the other hand, in the case of a display element used outdoors or the like, since the reflection of ambient light is more problematic than the light emission when the element itself is off, it is not necessary to suppress the light emission when the element is off. What can be suppressed by the organic light emitting element array of the present invention is the contrast due to light emission when the element is off. Therefore, the value of the contrast C is preferably set according to the purpose and use environment of the display.

  Below, the structural member of the organic light emitting element array of this invention is demonstrated in detail.

  Specific examples of the substrate 11 suitably used as the base material include various glass substrates, glass substrates in which driving circuits such as TFTs are formed with poly-Si, and those in which driving circuits are provided on a silicon wafer. It is done. Moreover, when taking out the light emitted from the opposite side with respect to the substrate 11, the substrate does not need to be transparent, but when taking out the light emitted from the substrate 11 side, the substrate 11 is preferably transparent. . Further, when the organic light emitting element array adopts an active matrix driving method, a switching element corresponding to the sub-pixel is preferably provided on the substrate 11.

  One of the lower electrode 12 and the upper electrode 18 is an anode, and the other is a cathode. Any of the constituent materials of the lower electrode 12 and the upper electrode 18 is preferably a transparent material.

  The material constituting the anode is preferably a material having a high work function. Specifically, a transparent conductive material having a large work function such as indium tin oxide (ITO) is preferably used.

  The material constituting the cathode is preferably a material having a low work function. Specifically, a metal having a small work function such as aluminum, an aluminum / lithium alloy, or a magnesium / silver alloy is preferably used.

  When the cathode is a transparent electrode, a thin film made of a metal material may be interposed between the organic compound layer and the transparent electrode layer. For example, a thin film made of a metal material that has a small work function and can be suitably used as a constituent material of a cathode is provided with a film thickness of about 1 nm to 10 nm on the side in contact with the organic compound layer, and then outside the thin film layer. A layer of a transparent conductive material such as ITO may be provided.

  The organic compound layer includes, for example, the first charge injection layer 13, the first charge transport layer 14, the light emitting layer 15, the second charge transport layer 16, the second charge injection layer 17 and the like shown in the organic light emitting element array 1 of FIG. Consists of. However, the configuration of the organic compound layer is not particularly limited as long as it has a charge injection layer (first charge injection layer 13) that is in direct contact with the lower electrode 12 and is commonly formed in each subpixel. The organic compound layer is preferably formed by a vapor deposition method or the like, but may be combined with spin coating, screen printing, an inkjet method, or the like.

  The light emitting layer 15 constituting the organic compound layer may be composed only of a light emitting material that obtains desired light emission, or may be composed of a combination of a host and a guest. When the light emitting layer is composed of a host and a guest, the method of layering is to form a light emitting layer having an arbitrary dope concentration by simultaneously vacuum-depositing the host material and the guest material and adjusting the respective deposition rates. can get. At this time, any light emission can be obtained from each organic light emitting element by changing the material of the light emitting layer or the host / guest combination constituting the light emitting layer corresponding to the light emission color.

  One of the first charge transport layer 14 and the second charge transport layer 16 is a hole transport layer made of a hole transport material, and the other is an electron transport layer made of an electron transport material. One of the first charge injection layer 13 and the second charge injection layer 17 is a hole injection layer made of a hole injection material, and the other is an electron injection layer made of an electron injection material. These may be selected according to the polarities of the lower electrode 11 and the upper electrode 18 to be used. That is, when the lower electrode 12 is a cathode, the first charge injection layer 13 is an electron injection layer made of an electron injection material, and the first charge transport layer 14 is an electron transport layer made of an electron transport material.

  Examples of the hole transport material constituting the hole transport layer include, but are not limited to, low molecular compounds such as triphenyldiamine derivatives, oxadiazole derivatives, polyphylyl derivatives, and stilbene derivatives. Absent.

  Examples of the electron transport material constituting the electron transport layer include, but are not limited to, an aluminum quinolinol derivative, an oxadiazole derivative, a triazole derivative, a phenylquinoxaline derivative, and a silole derivative.

Examples of the hole injection material constituting the hole injection layer include metal oxides such as vanadium oxide (VO _x ), molybdenum oxide (MoO _x ), and rubidium oxide (RuO _x ). The hole injection layer may be a layer made of a metal oxide such as vanadium oxide or a mixed layer in which a metal oxide such as vanadium oxide and an organic compound that is a hole transport material are combined. May be.

  Examples of the electron injection material constituting the electron injection layer include alkali metal compounds such as alkali metals, alkali metal salts, and alkali metal oxides. The electron injection layer may be a layer made of an alkali metal, an alkali metal compound, or the like, or may be a mixed layer in which an alkali metal, an alkali metal compound, etc. and an organic compound that is an electron transport material are combined. Good. When the electron injection layer is a mixed layer, the electron injection layer is preferably a layer in which a cesium compound and an organic compound that is an electron transport material are combined. The cesium compound contained in the mixed layer is preferably a cesium carbonate or a substance obtained by heating cesium carbonate.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example 1]
(Preparation of organic light emitting device array)
The organic light emitting device array shown in FIG. 1 was manufactured by the following steps.

  First, an AlNd film is formed by sputtering on an active matrix substrate (substrate 11) having a driving circuit and the like, a sub-pixel having a square shape of 100 μm on a side and an interval of each pixel being 20 μm. Formed. At this time, the thickness of the reflective electrode was set to 100 nm. Next, ITO was formed on the reflective electrode by sputtering to form an ITO thin film. At this time, the thickness of the ITO thin film was set to 20 nm. Next, patterning was performed by photolithography to form the lower electrode 12. In this embodiment, the lower electrode 12 functions as a cathode.

  Next, a pixel separation film 19 was formed by patterning polyimide with a photolithography method. At this time, the thickness of the pixel isolation film 19 was set to 1000 nm. When the pixel separation film 19 was formed, the size (effective pixel size) of the lower electrode 11 not covered with the pixel separation film 19 was 100 μm × 100 μm.

  Next, the substrate 11 on which the lower electrode 12 and the pixel separation film 19 were formed was subjected to UV ozone cleaning under atmospheric pressure, and then moved to a vacuum chamber.

Next, continuous film formation by resistance heating was performed while controlling the pressure in the vacuum chamber to 10 ⁻⁴ Pa.

  Specifically, first, ET-1 and cesium carbonate shown below are covered so as to cover the lower electrode 12 and the pixel separation film 19 so that the cesium carbonate is 2.9% by volume with respect to the entire layer. The first charge injection layer 13 was formed by co-evaporation. At this time, the thickness of the first charge injection layer 13 was set to 10 nm.

  Next, ET-1 was formed on the first charge injection layer 13 to form the first charge transport layer 14. At this time, the thickness of the first charge transport layer 14 was set to 50 nm.

  Next, EM-1 and EM-2 shown below are co-deposited on the first charge transport layer 14 so that EM-2 is 13% by volume with respect to the entire layer, thereby forming the light emitting layer 15. did.

  In addition, when forming the light emitting layer 15, it formed with the desired pattern using mask vapor deposition, and the film thickness was 20 nm. Here, the light emitting layer 15 which is a mixed layer of EM-1 and EM-2 exhibits blue light emission.

  Next, HT-1 shown below was formed on the light emitting layer 15 to form the second charge transport layer 16. At this time, the thickness of the second charge transport layer 16 was set to 10 nm.

Next, HT-1 and vanadium oxide (V ₂ O ₅ ) were co-deposited on the second charge transport layer 16 so as to have a volume ratio of 1: 1 to form a second charge injection layer 17. . At this time, the thickness of the second charge injection layer 17 was set to 20 nm.

  Next, an ITO film was formed on the second charge injection layer 17 to form the upper electrode 18. At this time, the film thickness of the upper electrode 18 was set to 30 nm. In this embodiment, the upper electrode 18 functions as an anode.

  The organic light emitting element array was obtained by the above method.

(Evaluation of resistivity of charge injection layer)
The resistivity of the hole injection layer and the electron injection layer, which are charge injection layers, was evaluated by the following method.

(I) Hole injection layer HT-1 and vanadium oxide (V ₂ O ₅ ) were co-deposited on a glass substrate so as to have a volume ratio of 1: 1 to form a thin film having a thickness of 20 nm.

When the resistivity of this thin film was measured using a comb electrode, the resistivity ρ _EIL was about 100 Ωm.

(Ii) Electron Transport Layer ET-1 and cesium carbonate were co-deposited on the glass substrate so that the cesium carbonate was 2.9% by volume with respect to the entire layer to form a thin film having a thickness of 10 nm.

When the resistivity of this thin film was measured using a comb electrode, the resistivity ρ _HIL was about 270 Ωm.

(Characteristic evaluation of organic light emitting device array)
At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  Further, when active matrix driving was performed on the organic light emitting element array of this example, a good display with a sharp outline and high contrast was obtained.

[Comparative Example 1]
(Preparation of organic light emitting device array)
In Example 1, an organic light emitting element array was obtained by the same method as Example 1 except that the film thickness of the first charge injection layer was 50 nm and the film thickness of the first charge transport layer was 10 nm. .

At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  In addition, active matrix driving was performed on the organic light emitting element array of this comparative example, but the display of the white display was blurred.

[Example 2]
(Preparation of organic light emitting device array)
The organic light emitting device array shown in FIG. 1 was manufactured by the following steps.

  First, a glass substrate (substrate 11) on which the lower electrode 11 and the pixel separation film 19 were formed was produced by the same method as in Example 1. In this embodiment, the lower electrode 11 functions as an anode. The substrate 11 used in this example is an active matrix substrate in which the shape of the subpixel is a rectangle of 190 μm × 63 μm, and the interval between the pixels is 20 μm. Further, when the pixel separation film 19 is formed, the size (effective pixel size) of the lower electrode 11 not covered with the pixel separation film 19 is 140 μm × 43 μm.

  Next, the substrate 11 on which the lower electrode 12 and the pixel separation film 19 were formed was subjected to UV ozone cleaning under atmospheric pressure, and then moved to a vacuum chamber.

Next, continuous film formation by resistance heating was performed while controlling the pressure in the vacuum chamber to 10 ⁻⁴ Pa.

  Specifically, first, HT-1 and vanadium oxide are co-deposited on the lower electrode 11 so as to have a volume ratio of 1: 1, thereby covering the lower electrode 11 and the pixel separation film 19. An injection layer 12 was formed. At this time, the thickness of the first charge injection layer 12 was set to 10 nm.

  Next, HT-1 was formed on the first charge injection layer 12 to form the first charge transport layer 13. At this time, the thickness of the first charge transport layer 13 was set to 50 nm.

  Next, EM-1 and EM-2 were co-deposited on the first charge transport layer 14 so that EM-2 was 13% by volume with respect to the entire layer, whereby the light emitting layer 15 was formed. At this time, the thickness of the light emitting layer 15 was set to 20 nm. The method for forming the light emitting layer 15 is the same as in Example 1.

  Next, ET-1 was formed on the light emitting layer 15 to form the second charge transport layer 16. At this time, the film thickness of the two charge transport layer 16 was 10 nm.

  Next, the second charge injection layer 17 was formed by co-evaporating ET-1 and cesium carbonate on the second charge transport layer 16 so that cesium carbonate was 2.9% by volume with respect to the entire layer. . At this time, the thickness of the second charge injection layer 17 was set to 20 nm.

  Next, an ITO film was formed on the second charge injection layer 17 to form the upper electrode 18. At this time, the film thickness of the upper electrode 18 was set to 30 nm. In this embodiment, the upper electrode 18 functions as a cathode.

  The organic light emitting element array was obtained by the above method.

At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  Further, when active matrix driving was performed on the organic light emitting element array of this example, a good display with a sharp outline and high contrast was obtained as in Example 1.

[Comparative Example 2]
(Preparation of organic light emitting device array)
In Example 2, an organic light emitting element array was obtained by the same method as Example 2 except that the film thickness of the first charge injection layer was 50 nm and the film thickness of the first charge transport layer was 10 nm. .
R _{CIL at} this time is expected to be as follows.

At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  In addition, active matrix driving was performed on the organic light emitting element array of this comparative example, but the display of the white display was blurred.

[Example 3]
(Preparation of organic light emitting device array)
The organic light emitting device array shown in FIG. 1 was manufactured by the following steps.

  First, a glass substrate (substrate 11) on which the lower electrode 11 and the pixel separation film 19 were formed was produced by the same method as in Example 1. In this embodiment, the lower electrode 11 functions as a cathode. The substrate 11 used in this example is an active matrix substrate in which the shape of the subpixel is a rectangle of 96 μm × 32 μm, and the interval between the pixels is 20 μm. Furthermore, when the pixel separation film 19 is formed, the size (effective pixel size) of the lower electrode 11 not covered with the pixel separation film 19 is 76 μm × 12 μm.

  Next, the substrate 11 on which the lower electrode 12 and the pixel separation film 19 were formed was subjected to UV ozone cleaning under atmospheric pressure, and then moved to a vacuum chamber.

Next, continuous film formation by resistance heating was performed while controlling the pressure in the vacuum chamber to 10 ⁻⁴ Pa.

  Specifically, first, ET-1 and cesium carbonate are co-deposited so as to cover the lower electrode 12 and the pixel separation film 19 so that the cesium carbonate is 0.3% by volume with respect to the entire layer. Thus, the first charge injection layer 13 was formed. At this time, the thickness of the first charge injection layer 13 was set to 10 nm.

  Next, ET-1 was formed on the first charge injection layer 13 to form the first charge transport layer 14. At this time, the thickness of the first charge transport layer 14 was set to 50 nm.

  Next, EM-1 and EM-2 were co-deposited on the first charge transport layer 14 so that EM-2 was 13% by volume with respect to the entire layer, whereby the light emitting layer 15 was formed. In addition, when forming the light emitting layer 15, it formed with the desired pattern using mask vapor deposition, and the film thickness was 20 nm.

  Next, HT-1 was formed on the light emitting layer 15 to form the second charge transport layer 16. At this time, the thickness of the second charge transport layer 16 was set to 10 nm.

  Next, HT-1 and vanadium oxide were co-deposited on the second charge transport layer 16 so as to have a volume ratio of 1: 1, thereby forming a second charge injection layer 17. At this time, the thickness of the second charge injection layer 17 was set to 20 nm.

  Next, an ITO film was formed on the second charge injection layer 17 to form the upper electrode 18. At this time, the film thickness of the upper electrode 18 was set to 30 nm. In this embodiment, the upper electrode 18 functions as an anode.

  The organic light emitting element array was obtained by the above method.

Here, when the resistivity was measured for the electron injection layer used in Example 3, that is, the electron injection layer: ET-1 and 0.6 vol% cesium carbonate co-deposition layer, the resistivity ρ _EIL was about 350 Ωm. Met.

At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  Further, when active matrix driving was performed on the organic light emitting element array of this example, a good display with a sharp outline and high contrast was obtained as in Example 1.

[Comparative Example 3]
(Preparation of organic light emitting device array)
In Example 3, an organic light emitting device array was obtained by the same method as in Example 3 except that the film thickness of the first charge injection layer was 50 nm and the film thickness of the first charge transport layer was 10 nm. .

At this time, the resistance R _CIL between the sub-pixels is expected to be as follows.

  In addition, active matrix driving was performed on the organic light emitting element array of this comparative example, but the display of the white display was blurred.

1 is a schematic cross-sectional view showing an embodiment of an organic light-emitting element array of the present invention. It is a figure which shows the equivalent circuit provided with two types of elements. It is a graph which shows an example of the current-voltage characteristic in the equivalent circuit of FIG. 6 is a graph showing current-voltage characteristics in organic light-emitting element arrays of Example 1 and Comparative Example 1. 6 is a graph showing current-voltage characteristics in organic light-emitting element arrays of Example 2 and Comparative Example 2. 6 is a graph showing current-voltage characteristics in organic light-emitting element arrays of Example 3 and Comparative Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic light emitting element 11 Substrate 12 Lower electrode 13 First charge injection layer 14 First charge transport layer 15 Light emitting layer 16 Second charge transport layer 17 Second charge injection layer 18 Counter electrode 21 First element 22 Second element 23 Resistance

Claims (9)

On the substrate, a plurality of sub-pixels having an organic light emitting device including at least a lower electrode, a charge injection layer, and an upper electrode in this order are disposed.
The lower electrode is in contact with the charge injection layer;
The charge injection layer is formed in common to the sub-pixels;
An organic light-emitting element array characterized by satisfying the relationship of the following formula 1 with respect to the electric resistance of a portion formed between adjacent sub-pixels in the charge injection layer.

(In Equation 1, R _CIL represents the electrical resistance of the charge injection layer formed between adjacent sub-pixels. V _max represents the driving voltage at the maximum luminance. I _max represents the sub-pixel at the maximum luminance. (V _leak represents a voltage required to flow a current (I _max ) flowing through the sub-pixel at the maximum luminance. C represents a contrast to be obtained.)   The organic light-emitting element array according to claim 1, wherein the charge injection layer is an electron injection layer.   The organic light-emitting element array according to claim 1, wherein the electron injection layer is composed of an alkali metal or an alkali metal compound and an electron transport material.   The organic light-emitting element array according to claim 3, wherein the alkali metal compound is a cesium compound.   The organic light-emitting element array according to claim 1, wherein the cesium compound is cesium carbonate or a substance obtained by heating the cesium carbonate.   2. The organic light emitting device array according to claim 1, wherein the charge injection layer is a hole injection layer.   The organic light-emitting element array according to claim 6, wherein the hole injection layer is made of a metal oxide.   The organic light-emitting element array according to claim 6, wherein the hole injection layer is a mixed layer of a layer made of a metal oxide and a hole transport material.   9. The organic light emitting element array according to claim 1, wherein a switching element is provided at a position corresponding to the sub-pixel.

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