JP4819603B2 - ORGANIC LIGHT EMITTING ELEMENT AND MULTICOLOR DISPLAY DEVICE USING THE ORGANIC LIGHT EMITTING ELEMENT - Google Patents

Description

  The present invention relates to an organic light emitting device including at least a light emitting layer made of an organic compound and an electron injection layer sandwiched between a pair of electrodes, and a multicolor display device using the organic light emitting device.

  FIG. 1 is a schematic view showing a laminated structure of a top emission type organic light emitting device. In FIG. 1, 0 is a substrate, 1 is an anode, 2 is a hole transport layer, 3 is a light emitting layer, 4 is an electron transport layer, 5 is an electron injection layer, 6 is a cathode, 7 is a hygroscopic material, and 8 is a sealing member. Respectively.

  For the purpose of improving the light emission efficiency of such an organic light emitting device, there is one that uses an electron injection layer (5 in FIG. 1) containing cesium carbonate to improve electron injection (see Patent Document 1).

  In addition, there is one in which an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound is formed by vapor deposition as a hygroscopic material (7 in FIG. 1) for the purpose of improving life characteristics (Patent Document). 2).

  As described above, it has been conventionally known that cesium carbonate is used for the electron injection layer and that an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound is deposited by vapor deposition as a moisture absorbent. It was.

  However, the relationship between the hygroscopicity of the material used for the electron injection layer and the material used for the hygroscopic material and the method for avoiding the absorption of the extracted light by the hygroscopic material have not been known at all.

Special table 2005-510034 (2nd page, 14th line) JP 2003-317935 A (page 2, lines 13-14)

  In the conventional organic light emitting device described above, cesium carbonate is used for the electron injection layer and the electron injection property is improved. However, since the moisture absorption property of cesium carbonate is high, the electron injection layer gradually deteriorates and the life characteristics are increased. There was a problem of getting worse.

  Moreover, even when alkali metal, alkali metal compound, alkaline earth metal, or alkaline earth metal compound is used as the hygroscopic material, if the material used for the electron injecting layer is highly hygroscopic, such as cesium carbonate, it is hygroscopic. There was a problem that the material was useless.

  In addition, the hygroscopic material has to be formed thick as a film, and in particular, there is a problem of absorbing blue light and lowering the luminance of the blue element.

  An object of the present invention is to provide an organic light emitting device that prevents deterioration of an electron injection layer, has good life characteristics, and can effectively act as a hygroscopic material.

  It is another object of the present invention to provide a multi-color display device using the organic light-emitting element without causing deterioration without reducing the luminance of the blue organic light-emitting element.

As means for solving the problems of the background art described above, the organic light-emitting device according to the present invention is:
On an organic light emitting device comprising at least a light emitting layer made of an organic compound and an electron injection layer sandwiched between a pair of electrodes on a substrate,
The organic light emitting device is covered with a sealing member,
The electron injection layer includes an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound,
On the out light extraction electrode of the pair of electrodes, it has a hygroscopic material comprising cesium or cesium compound,
The alkali metal, alkali metal compound, alkaline earth metal or alkaline earth metal compound contained in the electron injection layer is the same as the cesium or cesium compound contained in the hygroscopic material .

  The organic light emitting device according to the present invention uses a hygroscopic material having a high hygroscopic property when the material used for the electron injecting layer is highly hygroscopic, such as cesium carbonate. It has good characteristics and can effectively act as a hygroscopic material.

  The multicolor display device according to the present invention uses a hygroscopic material having a high hygroscopic property when the material used for the electron injection layer is a high hygroscopic material such as cesium carbonate, and also emits organic light of other colors except blue. A hygroscopic material was formed on the element. Therefore, the luminance of the organic light emitting device that emits blue light does not decrease and does not deteriorate.

<Embodiment 1>
An embodiment of an organic light emitting device according to the present invention will be described with reference to FIG. 1 is a top emission type organic light emitting element, it may be a bottom emission type organic light emitting element.

  The organic light emitting device of the present invention has a configuration substantially similar to that of the existing organic light emitting device described above. That is, the anode 1, the hole transport layer 2, the light emitting layer 3, the electron transport layer 4, the electron injection layer 5, the cathode 6, and the hygroscopic material 7 are sequentially laminated on the substrate 0 and covered with the sealing member 8. ing.

  The electron injection layer 5 of the present invention contains an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound. The hygroscopic material 7 has a high hygroscopicity equivalent to or higher than that of the alkali metal, alkali metal compound, alkaline earth metal, or alkaline earth metal compound contained in the electron injection layer 5.

  Therefore, deterioration of the electron injection layer 5 can be prevented, life characteristics can be improved, and the hygroscopic material 7 can be effectively operated.

  Hereinafter, the organic light emitting device of the present invention will be described in detail.

  An anode 1 which is a reflective electrode that reflects light is provided on a substrate 0. Examples of the anode 1 include Cr, Al, Ag, or an alloy thereof. A metal having a higher reflectance is more preferable. In the present invention, a reflective layer for reflecting light and a transparent electrode for injecting charges can be laminated instead of the reflective electrode. At this time, the same metal as the reflective electrode is used as the reflective layer, and a transparent conductive material such as ITO or IZO is used as the transparent electrode.

  A hole transport layer 2 made of an organic compound is formed on the anode 1, and a light emitting layer 3 made of an organic compound is further formed. As the hole transport layer 2 and the light emitting layer 3, conventionally known materials can be used. The electron transport layer 4 may be formed on the light emitting layer 3, and in this case as well, conventionally known materials can be used.

  An electron injection layer 5 is formed on the light emitting layer 3 (electron transport layer 4).

  Among these substances, cesium or a cesium compound is preferable because of its high electron injection property, and among these, cesium carbonate is more preferable. Cesium carbonate is preferable because it can be deposited by heating and is more stable in air than cesium and other cesium compounds.

  An alkali metal such as cesium carbonate, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound may be used alone as an electron injection layer, but may be formed as a composite film co-deposited with an organic compound. preferable.

  A light extraction electrode that transmits light is stacked on the electron injection layer 5 as the cathode 6. As a material for forming the cathode, a transparent conductive material such as ITO or IZO or a metal material is formed to a thickness capable of transmitting light.

  A hygroscopic material 7 is formed on the cathode 6. In bottom emission type organic light emitting devices, it is common to install a hygroscopic material sheet on the back of the cathode (reflective electrode). However, in top emission type devices, the upper part serves as a light extraction electrode. Material is required.

  As the hygroscopic material 7, an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound used for the electron injection layer 5 is used, and a material having a high hygroscopicity is used for the electron transport layer 4. It is also preferable to use the same material as the hygroscopic material.

  That is, as the hygroscopic material 7, an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound is used. It may be formed in combination with a material.

  As the hygroscopic material 7, cesium or a cesium compound is preferable because of its high hygroscopicity, and among these, cesium carbonate is more preferable. When cesium carbonate is used for the electron injection layer 5, it is preferable to use cesium carbonate as the moisture absorbent 7.

Here, the magnitude of hygroscopicity is as follows. Each test specimen dried to a constant weight at 120 ° C. is placed in a container, and left in a constant temperature and humidity layer having an air temperature of 25 ° C. and a relative humidity of 10% for 24 hours. The change is measured, and the amount of moisture absorption is calculated from the following <Equation 1>.
Moisture absorption amount (moisture release amount) ΔM = mass at each measurement−mass at start of test ··· <Equation 1>

  The organic light emitting device having the above configuration is covered with a sealing member 8 in order to block it from the outside air. The sealing member 8 is formed of a material that transmits light, such as glass or plastic, and is adhered to the substrate 0 or the anode 1 without a gap. Note that the inside of the sealing member 8 may be hollow or filled with resin or the like as long as light can be transmitted.

<Embodiment 2>
An embodiment of a multicolor display device according to the present invention will be described with reference to FIG. In addition, since the multicolor display device of the present invention has a configuration using the organic light emitting element having the above configuration, the details of the organic light emitting element are omitted.

  The multicolor display device of the present invention also has substantially the same configuration as a conventional multicolor display device. That is, on the substrate 10, the anode 11, the hole transport layer 12, the light emitting layers 13 R, 13 G, and 13 B exhibiting the respective emission colors (red, green, and blue in this embodiment), the electron transport layer 14, the electron injection layer 15, A cathode 16 and a hygroscopic material 17 are sequentially laminated and covered with a sealing member 18.

  The electron injection layer 15 of the present invention contains an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound. And the moisture absorption material 17 is formed on the 2nd electrode 16 of the organic light emitting element of other colors (this embodiment R, G) except blue (B). The hygroscopic material 17 has a high hygroscopic property equivalent to or higher than that of an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound contained in the electron injection layer 15.

  Therefore, deterioration of the electron injection layer 15 can be prevented, the life characteristics can be improved, and the hygroscopic material 17 can be effectively operated. In addition, since the hygroscopic material 17 is formed on the second electrode 16 of the organic light emitting elements other than blue, the multicolor display device without deterioration is provided without reducing the luminance of the blue organic light emitting elements. can do. In addition, the thick moisture-absorbing material 17 can be formed even with a material that easily absorbs blue light.

  Incidentally, the hygroscopic material 17 is preferably a hygroscopic film formed by vapor deposition. This is convenient when the hygroscopic material 17 is formed on the second electrode 16 of the organic light emitting elements of other colors except blue.

  As described above, the electron injection layer 15 preferably contains cesium or a cesium compound, and more preferably contains cesium carbonate. Cesium carbonate is preferable because it can be deposited by heating and is more stable in air than cesium and other cesium compounds.

  Further, the hygroscopic material 17 preferably contains cesium or a cesium compound, and more preferably contains cesium carbonate. When cesium carbonate is used for the electron injection layer 15, it is preferable to use cesium carbonate as the moisture absorbing material 17. Moreover, the hygroscopic material 17 preferably contains the same material as the alkali metal, alkali metal compound, alkaline earth metal, or alkaline earth metal compound contained in the electron injection layer 15.

  Examples of the present invention will be described below, but the materials and structures used in the examples are particularly preferable examples, but are not limited thereto.

<Example 1>
FIG. 1 shows a top emission type organic light emitting device of this example. In addition, the organic light emitting element of a present Example exhibits a green luminescent color.

  Cr was laminated on a glass support substrate 0 by sputtering to a thickness of 200 nm to form an anode 1, and then the anode 1 was subjected to UV / ozone cleaning.

Subsequently, the cleaned substrate and material were attached to a vacuum evaporation apparatus (manufactured by ULVAC Kiko Co., Ltd.), and after exhausting to 1 × 10 ⁻³ Pa, N, N′-α-dinaphthylbenzidine (α -NPD) was formed to a thickness of 40 nm to form a hole transport layer 2.

  Further, a co-deposited film of coumarin dye (1.0 vol%) and tris [8-hydroxyquinolinate] aluminum (Alq3), which is known to exhibit green light emission, is formed to a thickness of 30 nm. The light emitting layer 3 was obtained.

  Next, as the electron transport layer 4,

で表される、フェナントロリン化合物を１０ｎｍの膜厚で成膜した。

A phenanthroline compound represented by the formula was formed to a thickness of 10 nm.

  On the electron transport layer 4, a co-deposited film of cesium carbonate (2.9 vol%) and the phenanthroline compound represented by the above <Chemical Formula 1> was formed to a thickness of 40 nm, thereby forming an electron injection layer 5.

  The substrate formed up to the electron injection layer 5 is moved to another sputtering apparatus (manufactured by Osaka Vacuum Co., Ltd.), and indium tin oxide (ITO) is formed on the electron injection layer 5 with a film thickness of 60 nm by sputtering. Thus, a cathode 6 was obtained.

  Thereafter, the substrate was returned to the vacuum vapor deposition apparatus, and cesium carbonate was vapor-deposited to a thickness of 160 nm. Next, it moved to the glove box and sealed by using a glass cap as the sealing member 8 in a nitrogen atmosphere.

  The organic light emitting device obtained by the above manufacturing procedure was applied with a direct voltage increased from 0 V to 0.25 V, and the light emission characteristics were examined. The initial luminous efficiency of this device was calculated to be 5.8 cd / A.

  Furthermore, an accelerated moisture absorption test was conducted for 1 hour in an environment of a temperature of 60 ° C. and a humidity of 90%, and the luminous efficiency was determined in the same manner as in the initial stage. As a result, it was 5.7 cd / A. It was a good device.

<Example 2 (reference example) >
A top emission type organic light emitting device was prepared in the same manner as in Example 1 except that the hygroscopic material 7 was formed on the back surface of the sealing member 8, that is, the surface of the sealing member 8 on the substrate 0 side. Measurements were made.

  The initial luminous efficiency was 6.1 cd / A, the luminous efficiency after the accelerated moisture absorption test was 6.0 cd / A, and there was almost no deterioration and the light emitting state was uniform and good.

<Example 3 (reference example) >
The top emission type was the same as in Example 1 except that the electron injection layer 5 was formed by rubidium carbonate (2.9 vol%) and a phenanthroline compound co-deposited film represented by the above <Chemical Formula 1> with a film thickness of 40 nm. An organic light emitting device was prepared, and the same measurement as in Example 1 was performed.

  The initial light emission efficiency was 4.9 cd / A, the light emission efficiency after the accelerated moisture absorption test was 4.9 cd / A, and there was almost no deterioration and the light emission state was uniform and good.

<Example 4>
A co-deposited film of perylene dye (1.0 vol%) and tris [8-hydroxyquinolinato] aluminum (Alq3), which is known to exhibit blue light emission, was formed to a thickness of 20 nm as the light emitting layer 3. . Other than that, a top emission type organic light emitting device was prepared in the same manner as in Example 1.

  When the same measurement as in Example 1 was performed, the initial light emission efficiency was 1.5 cd / A, the light emission efficiency after the accelerated moisture absorption test was 1.5 cd / A, almost no deterioration, and the light emission state was uniform. It was a good device.

<Comparative Example 1>
A top emission type organic light emitting device was prepared in the same manner as in Example 1 except that the hygroscopic material 7 was not formed.

  When the same measurement as in Example 1 was performed, the initial luminous efficiency was 5.8 cd / A, and the luminous efficiency after the accelerated moisture absorption test was reduced to 4.8 cd / A. The light emitting state was also a non-uniform element with dark spots.

<Comparative example 2>
A top emission type organic light emitting device was prepared in the same manner as in Example 1 except that lithium fluoride was formed to a thickness of 160 nm as the moisture absorbent 7.

  When the same measurement as in Example 1 was performed, the initial luminous efficiency was 5.7 cd / A, and the luminous efficiency after the accelerated moisture absorption test was reduced to 4.9 cd / A. The light emitting state was also a non-uniform element with dark spots.

<Comparative Example 3>
A top emission type organic light emitting device was prepared in the same manner as in Example 3 except that the hygroscopic material 7 was not formed.

  When the same measurement as in Example 1 was performed, the initial luminous efficiency was 4.8 cd / A, and the luminous efficiency after the accelerated moisture absorption test was reduced to 3.6 cd / A. The light emitting state was also a non-uniform element with dark spots.

<Comparative example 4>
A top emission type organic light emitting device was prepared in the same manner as in Example 4 except that the hygroscopic material 7 was not formed.

  When the same measurement as in Example 1 was performed, the initial luminous efficiency was 2.0 cd / A, and the luminous efficiency after the accelerated moisture absorption test was reduced to 0.9 cd / A.

  The initial luminous efficiency was higher than that of Example 4 because there was no absorption by the hygroscopic material, but after the accelerated moisture absorption test, the light emitting state was a non-uniform element in which dark spots were generated.

  The results of Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention are summarized in <Table 1>.

  In the present invention, when a material having a high hygroscopic property is used for the electron injection layer 5, the hygroscopic material 7 having a hygroscopic property equal to or higher than that is used. Therefore, deterioration of the electron injection layer 5 can be prevented, life characteristics can be improved, and the hygroscopic material 7 can be effectively operated.

<Example 5>
This embodiment is a multicolor display device using a top emission type organic light emitting element (not shown). In the multicolor display device of this embodiment, unlike the one shown in FIG. 2, the anode is an individual electrode and the cathode is a common electrode.

  UV / ozone cleaning was performed on a substrate with electrodes for multi-color display capable of 200 ppi display in which a TFT, a circuit, an anode (reflection electrode), a planarization film, an element isolation film, etc. were formed on glass. Similarly, a hole transport layer was formed.

  Next, an Ir complex (18 vol%) and 4,4′-N, N′-dicarbazole-biphenyl (CBP) co-deposited film exhibiting red light emission at a red electrode position using a mask vapor deposition method is a 50 nm film. A film was formed with a thickness to form a light emitting layer that emits red light.

  Next, a co-deposited film of coumarin dye (1.0 vol%) and tris [8-hydroxyquinolinate] aluminum (Alq3) that emits green light at the position of the green electrode using a mask vapor deposition method is formed to a thickness of 30 nm. To form a light emitting layer that emits green light.

  Next, a co-deposition film of perylene dye (1.0 vol%) and tris [8-hydroxyquinolinate] aluminum (Alq3) that emits blue light is formed to a thickness of 20 nm using the mask vapor deposition method. A light emitting layer exhibiting blue light emission was obtained.

  From the electron transport layer to the cathode in the same manner as in Example 1, cesium carbonate was sequentially deposited on the red pixel (element) portion and the green pixel portion with a film thickness of 160 nm using a mask vapor deposition method. A hygroscopic material was used.

  It moved to the glove box and sealed by using a glass cap as a sealing member in a nitrogen atmosphere.

  Although an accelerated moisture absorption test was conducted in the same manner as in Example 1, no deterioration or the like was observed in the display, and the device was a good multicolor display device.

<Comparative Example 5>
A multicolor display device was produced in the same manner as in Example 5 except that cesium carbonate was formed on all the red, blue, and green pixel portions without using the mask vapor deposition method in the hygroscopic material forming step.

  The accelerated moisture absorption test was conducted in the same manner as in Example 1 and no deterioration was observed. When light was emitted under the same conditions as in Example 5, the luminance of the organic light-emitting device that emitted blue light even in the initial state was low. It was a multicolor display device that was generally yellowish.

  In the present invention, when a material having a high hygroscopic property is used for the electron injection layer, a hygroscopic material having a high hygroscopic property equal to or higher than that is used, and the hygroscopic material is formed on organic light emitting elements of other colors except blue. Therefore, the luminance of the organic light emitting device that emits blue light does not decrease and does not deteriorate.

It is a schematic diagram which shows the laminated structure of a top emission type organic light emitting element. It is a schematic diagram which shows the multicolor display apparatus using the top emission type organic light emitting element.

Explanation of symbols

0 Substrate 1 Anode (reflection electrode)
2 Hole transport layer 3 Light emitting layer 4 Electron transport layer 5 Electron injection layer 6 Cathode (light extraction electrode)
7 Hygroscopic material 8 Sealing member 10 Substrate 11 Anode (reflective electrode)
12 hole transport layer 13R red light emitting layer 13G green light emitting layer 13B blue light emitting layer 14 electron transport layer 15 electron injection layer 16 cathode 17 hygroscopic agent 18 sealing member

Claims (3)

On an organic light emitting device comprising at least a light emitting layer made of an organic compound and an electron injection layer sandwiched between a pair of electrodes on a substrate,
The organic light emitting device is covered with a sealing member,
The electron injection layer includes an alkali metal, an alkali metal compound, an alkaline earth metal, or an alkaline earth metal compound,
On the out light extraction electrode of the pair of electrodes, it has a hygroscopic material comprising cesium or cesium compound,
An organic light-emitting element , wherein the alkali metal, alkali metal compound, alkaline earth metal, or alkaline earth metal compound contained in the electron injection layer is the same as the cesium or cesium compound contained in the hygroscopic material .   The organic light emitting device according to claim 1, wherein the cesium compound is cesium carbonate. An organic light emitting element which emits blue light, and a organic light emitting element emits light of a color other than blue, organic light-emitting device exhibiting color emission of other than the blue organic light-emitting according to claim 1 or 2 A multicolor display device characterized by being an element.

Images