JP4836093B2 - Organic EL device having a planar electrode - Google Patents

Description

  The present invention relates to an organic EL element having a planar electrode. In more detail, the electrode for applying a voltage to the light-emitting organic material has a three-terminal structure (anode electrode, cathode electrode, gate electrode). By applying an alternating voltage to the gate electrode, high luminance can be obtained. The present invention relates to an organic EL element having a planar electrode that can emit light.

A conventional general organic EL (Electroluminescence) display element is composed of a pixel and an organic light emitting layer sandwiched between two electrodes (an anode electrode and a cathode electrode). Then, by energizing between the anode electrode and the cathode electrode, holes and charges injected from the respective electrodes are recombined in the organic light emitting layer. The energy at this time is emitted as light (hereinafter, an organic EL element having such a configuration is referred to as a “two-terminal organic EL element”). In addition, it is possible to start light emission with a low driving voltage (about 6V) by newly providing a gate electrode in the configuration of electrodes (anode electrode, cathode electrode) in the conventional two-terminal organic EL element. In addition, an organic EL element that can obtain higher emission luminance than a conventional two-terminal organic EL element has been proposed (see Non-Patent Document 1) (hereinafter, an organic EL element having such a configuration is used). "Three-terminal organic EL element").
B. Park el al .: Applied Physics Letters 85 (2004) 7.

  However, in order to apply the organic EL element to display elements in various fields, it is necessary to set a drive voltage (turn-on voltage) necessary for starting light emission to a lower value and higher light emission. It is desired that light can be emitted with luminance. However, the turn-on voltage and light emission luminance of the three-terminal organic EL element described in Non-Patent Document 1 are not sufficient for the required levels, and further lower turn-on voltage and higher luminance are desired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an organic EL element having a planar electrode that can achieve low turn-on voltage and high luminance.

  In order to solve the above problems, an organic EL device having a planar electrode according to the first aspect of the present invention includes a transparent substrate, and an anode electrode and a gate electrode arranged in a planar shape on the surface of the transparent substrate. The organic material is laminated on the surface of the transparent substrate on which the anode electrode and the gate electrode are arranged, and has a light emitting property. An organic EL element having a planar electrode comprising a light-emitting organic material that is an organic material containing at least a material, and a cathode electrode that is laminated on a surface of the light-emitting organic material opposite to a surface in contact with the transparent substrate. Applying a DC voltage between the anode electrode and the cathode electrode and applying an AC voltage between the gate electrode and the cathode electrode. , Characterized in that for light emitting the light emitting organic material.

  According to a second aspect of the present invention, in the organic EL device having the planar electrode according to the second aspect, in addition to the configuration of the first aspect, the thickness of the gate electrode is larger than the thickness of the anode electrode. .

  An organic EL element having a planar electrode according to a third aspect of the invention is characterized in that at least one of the anode electrode and the gate electrode is opaque in addition to the configuration of the invention according to the first or second aspect. And

  In the organic EL element having the planar electrode according to the first aspect of the invention, a gate electrode is added as an electrode constituting the organic EL element in addition to the anode electrode and the cathode electrode, and an AC voltage is applied between the gate electrode and the cathode electrode. By applying, loss due to optical waveguide can be reduced, and light can be emitted with higher brightness than conventional organic EL elements.

  Further, in the organic EL element having the planar electrode of the invention according to claim 2, since the thickness of the gate electrode is larger than the thickness of the anode electrode, in addition to the effect of the invention of claim 1, the conventional organic EL element It is possible to emit light with higher luminance than the element.

  Further, in the organic EL device having the planar electrode of the invention according to claim 3, in addition to the effect of the invention according to claim 1 or 2, the organic EL device emits light with higher luminance than the conventional organic EL device. Is possible.

  Hereinafter, an organic EL element having a planar electrode as one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional perspective view showing a physical configuration of an organic EL element 10 according to the present invention, and FIG. 2 is an electrical configuration diagram of the organic EL element 10.

  First, the physical configuration of the organic EL element 10 will be described with reference to FIG. As shown in FIG. 1, the organic EL element 10 has a luminescent property with a transparent substrate 1, an anode electrode 2, a gate electrode 3, and a cathode electrode 5 for supplying light to the luminescent organic material 4 to emit light. The light-emitting organic material 4 includes at least a material having a property of emitting light when energized.

  The transparent substrate 1 is used as a support that supports the light-emitting organic material 4 from below. Further, the transmittance is large, and light generated in the light-emitting organic material 4 can be easily extracted to the outside. The material of the transparent substrate 1 is not particularly limited, and a conventionally known material can be used. For example, a transparent glass substrate or an ITO substrate having a surface made of a mixture of indium oxide and tin oxide and having conductivity on the surface may be used.

  The anode electrode 2 and the gate electrode 3 are arranged in a planar shape on the surface of the transparent substrate 1. Both electrodes are alternately arranged in a comb shape. In FIG. 1, only the pair of anode electrode 2 and gate electrode 3 among the anode electrode 2 and gate electrode 3 arranged in a comb shape is shown. When the luminescent organic material 4 is caused to emit light, a voltage is applied to the anode electrode 2 and the gate electrode 3 under predetermined conditions.

  The thicknesses of both electrodes are set so that the thickness of the gate electrode 3 is larger than the thickness of the anode electrode 2. In this way, it is possible to cause the organic EL element 10 to emit light with higher luminance than when the thickness of the anode electrode 2 and the thickness of the gate electrode 3 are the same (for details, see <Implementation> Explained in Example>). Furthermore, at least one of the anode electrode 2 and the gate electrode 3 has a low transmittance and is in an opaque state. Thus, by making the transmittance of the electrode small and making it opaque, the light (arrow 11 in FIG. 1) generated from the light-emitting organic material 4 is blocked by the electrode, but the light emitted to the outside Is higher than that in the case where the transmittance of the electrode is large and the electrode is transparent (details will be described in <Example>). The materials for the anode electrode 2 and the gate electrode 3 are not particularly limited, and conventionally known materials can be used. For example, metals such as copper, iron, aluminum, gold, silver, lead, chrome, and ITO coated on an ITO substrate can be used.

  The light emitting organic material 4 is laminated and arranged on the surface of the transparent substrate 1 so as to cover the anode electrode 2 and the gate electrode 3 arranged in a comb shape in a planar shape. In addition, it contains at least a material capable of releasing light energy by recombining injected holes and charges inside.

  As the light-emitting organic material 4, for example, a structure in which a hole transport layer (HIL (Hole Injection Layer)), a charge transport layer (ETL (Electron Transporting Layer)), and a light-emitting layer (EML (Emitting Material Layer)) are stacked. And an organic material that emits light by injecting holes from the HIL, injecting charges from the ETL, and recombining the holes and charges in the EML. Examples of organic materials used as HIL include NPB (N, N-di (naphthalene-1-yl) -N, N-diphenyl-benzidene) and PEDOT (poly (ethylenedioxy) thiophene), and EML. As an organic material used as PTL (poly (1,4-phenylene vinylene)), an organic material used as ETL and EML includes, for example, Alq3 (aluminato-tris-8-hydroxyquinolate).

  Further, the cathode electrode 5 is laminated and disposed on the surface of the light-emitting organic material 4 laminated on the surface of the transparent substrate 1 on the side opposite to the surface in contact with the anode electrode 2 and the gate electrode 3. And it forms in the surface on the opposite side to the surface which contact | connects the transparent substrate 1 so that the pair of anode electrode 2 and the gate electrode 3 which are arranged in the shape of a comb can be covered. The transmittance of the cathode electrode 5 is set low, and light generated from the light emitting organic material 4 does not pass through the cathode electrode 5. The material for the cathode electrode 5 is not particularly limited, and conventionally known materials can be used. Examples thereof include metals such as copper, iron, aluminum, gold, silver, lead, and chromium.

  Next, the light emission principle of the organic EL element 10 having the above configuration will be outlined. In order to cause the organic EL element 10 to emit light, a voltage is applied to the anode electrode 2 and the gate electrode 3 with the cathode electrode 5 as a reference potential. As a result, holes are injected from the anode electrode 2 and the gate electrode 3 to the luminescent organic material 4, and charges are injected from the cathode electrode 5 to the luminescent organic material 4. The injected holes and electric charges are recombined in the light emitting material contained in the light emitting organic material 4 to emit light. The generated light passes through the gap between the anode electrode 2 and the gate electrode 3 arranged in a comb shape, and further passes through the transparent substrate 1 and is emitted to the outside (arrow 11 in FIG. 1).

  Next, the electrical configuration of the organic EL element 10 will be described with reference to FIG. As shown in FIG. 2, when the organic EL element 10 is driven so that the luminescent organic material 4 emits light, a positive direct current voltage is applied to the anode electrode 2 with reference to the potential of the cathode electrode 5. Then, an alternating voltage is applied to the gate electrode 3 (8). In this way, by setting an electrical state in which an AC voltage is applied to the gate electrode 3, the organic EL element 10 is caused to emit light with higher brightness than when a DC voltage is applied to the gate electrode 3. Is possible. Furthermore, it is possible to make the turn-on voltage lower than when a DC voltage is applied to the gate electrode 3 (details will be described in <Example>). Note that the AC voltage applied to the gate electrode 3 may be a sine wave, a rectangular wave, or a square wave.

As described above, in the organic EL element 10, the anode electrode 2 and the gate electrode 3 are arranged on the transparent substrate 1 in a planar shape in a comb shape. Further, the thickness of the gate electrode 3 is adjusted to be larger than the thickness of the anode electrode 2. Further, at least one of the anode electrode 2 and the gate electrode 3 has low transmittance and is opaque, and light generated from the light-emitting organic material 4 does not pass through this electrode. Then, a DC voltage is applied to the anode electrode 2 and an AC voltage is applied to the gate electrode 3 to cause the luminescent organic material 4 to emit light. By doing in this way, compared with the conventional 2 terminal organic EL element and a 3 terminal organic EL element (nonpatent literature 1), it can be set as the organic EL element 10 which is high-intensity and has a low turn-on voltage. It has become.
<Example>

An example of a method for producing the organic EL element 10 (see FIG. 1) having a planar electrode and an evaluation result described above will be described with reference to the drawings. About evaluation, it implemented by making the produced organic EL element 10 (henceforth "sample A") light-emit, and measuring a brightness | luminance. In addition, in order to perform comparative evaluation between Sample A and a known organic EL element, among the configurations of the organic EL element 10, a sample having a configuration in which the thicknesses of the anode electrode 2 and the gate electrode 3 are the same (hereinafter, In the configuration of the organic EL element 10, the anode electrode 2 and the gate electrode 3 have the same thickness, and both the anode electrode 2 and the gate electrode 3 are transparent. A sample (hereinafter referred to as “sample C”) having a high transmittance was prepared. And the sample B and the sample C which were produced were light-emitted, and the difference with the sample A was implemented by measuring a brightness | luminance. In the following, description will be made in the order of 1) Sample A creation method, 2) Sample B creation method, 3) Sample C creation method, and 4) Evaluation by luminance measurement.
<How to create Sample A>

  A method for producing Sample A (organic EL element 10 (see FIG. 1)) will be described. First, the physical configuration of the created sample A will be described. FIG. 3 is a cross-sectional view showing the physical configuration of the sample A that was created. As shown in FIG. 3, the light-emitting organic material 4 includes a hole injection layer 20, a buffer layer 21, a hole transport layer 22, a light-emitting layer 23, a charge transport layer 24, and a buffer layer 25. Formed. As shown in FIG. 3, the buffer layer 21 is laminated on the upper surface of the hole injection layer 20, the hole transport layer 22 is laminated on the upper surface of the buffer layer 21, and the light emitting layer 23 is laminated on the upper surface of the hole transport layer 22. The charge transport layer 24 is laminated on the upper surface of the light emitting layer 23, and the buffer layer 25 is laminated on the upper surface of the charge transport layer 24. In addition, the hole injection layer 20 of the luminescent organic material 4 was disposed so as to be laminated on the transparent substrate 1 so as to cover the anode electrode 2 and the gate electrode 3 formed in a comb shape. In addition, the cathode electrode 5 was laminated on the upper surface of the buffer layer 25 of the light-emitting organic material 4.

  Next, a method for creating Sample A will be described. A transparent glass substrate was used as the transparent substrate 1 (see FIG. 1). Further, chromium was used as a material for the anode electrode 2 and the gate electrode 3. Then, comb-shaped electrodes (line width: 2 μm, line interval: 10 μm) formed of chromium were formed on a transparent glass substrate by vacuum deposition, and these were used as an anode electrode and a gate electrode. In addition, by adjusting the conditions of vacuum deposition so that the thickness of the gate electrode 3 is larger than the thickness of the anode electrode 2, the thickness of the anode electrode 2 is 30 nm and the thickness of the gate electrode 3 is 60 nm. Each electrode was formed so as to be. Further, the transmittance of the formed anode electrode 2 and gate electrode 3 is small (transmittance: 1% or less (visible transmission region)), and both electrodes are in an opaque state.

Next, the hole injection layer 20 was laminated so as to cover the anode electrode 2 and the gate electrode 3 formed on the surface of the transparent glass substrate (corresponding to the transparent substrate 1, see FIG. 1). As the material for the hole injection layer 20, MoO ₃ (“Molybdenum trioxide” manufactured by Japan High-Purity Chemical Co., Ltd.) was used, and the hole injection layer 20 having a thickness of 70 nm was formed on the transparent glass substrate by vacuum deposition. . Next, the buffer layer 21 was laminated on the upper surface of the hole injection layer 20. As a material of the buffer layer 21, PEDOT (“polyethylenedioxythiophene” manufactured by HC Starck) was used, and a buffer layer having a thickness of 30 nm was laminated by a spin coating method. Next, the hole transport layer 22 was laminated on the upper surface of the buffer layer 21. As a material for the hole transport layer 22, TAPC (1,1-bis [(di-4-tolylamino) phenyl] cyclohexane) (“1,1-bis (4- (N, N-di (para-tolyl) amino)-) The hole transport layer 22 having a film thickness of 50 nm was laminated by a vacuum deposition method using “Phenyl) cyclohexane” (manufactured by Tokyo Chemical Industry Co., Ltd.). Next, the light emitting layer 23 was laminated on the upper surface of the hole transport layer 22. The weight ratio of CBP (4,4′-bis [9-dicarbazolyl] -2,2′-biphenyl) and Ir (ppy) ₃ (Tris (2-phenylpyridine) iridium (III)) as the material of the light emitting layer 23 Using a mixture of 100: 5 (“4,4′-bis (9-carbazolyl) -biphenyl and tris (2-phenylpyridine) iridium” manufactured by Luminescence Technology Co., Ltd.) A 30 nm light emitting layer 23 was laminated. Next, the charge transport layer 24 was laminated on the upper surface of the light emitting layer 23. As a material for the charge transport layer 24, BCP (Bathocuprione) (“Basocproin” manufactured by Kanto Chemical Co., Inc.) was used, and the charge transport layer 24 having a thickness of 20 nm was laminated by vacuum deposition.

  Next, the buffer layer 25 was formed on the upper surface of the charge transport layer 24. As the buffer layer 25, a LiF film (film thickness: 1 nm) was laminated on the upper surface of the charge transport layer 24 by a vacuum deposition method.

Next, the cathode electrode 5 was formed on the upper surface of the buffer layer 25. As the cathode electrode 5, an AlNd film (film thickness: 70 nm) was laminated on the upper surface of the buffer layer 25 by a vacuum deposition method. Sample A was prepared as described above.
<Sample B creation>

  Next, a method for creating Sample B will be described. First, the physical configuration of the created sample B will be described. FIG. 4 is a cross-sectional view showing a physical configuration of the prepared sample B. As shown in FIG. 4, the light-emitting organic material 4 is formed by laminating a hole injection layer 30, a buffer layer 31, a hole transport layer 32, a charge transport light-emitting layer 33, and a buffer layer. It was. As shown in FIG. 4, a buffer layer 31 is laminated on the upper surface of the hole injection layer 30, a hole transport layer 32 is laminated on the upper surface of the buffer layer 31, and a charge transporting light emitting layer is formed on the upper surface of the hole transport layer 32. 33 is laminated, and the buffer layer 34 is laminated on the upper surface of the charge transporting light emitting layer 33. In addition, the hole injection layer 30 of the luminescent organic material 4 was disposed so as to be laminated on the transparent substrate 1 so as to cover the anode electrode and the gate electrode formed in a comb shape. Further, the cathode electrode 5 was laminated on the upper surface of the buffer layer 34 of the luminescent organic material 4.

  Next, a method for creating Sample B will be described. A transparent glass substrate was used as the transparent substrate 1 (see FIG. 1). Further, chromium was used as a material for the anode electrode and the gate electrode. Then, comb-shaped electrodes (line width: 2 μm, line interval: 10 μm) formed of chromium were formed on a transparent glass substrate by vacuum deposition, and these were used as an anode electrode and a gate electrode. Since the anode electrode and the gate electrode are formed under the same conditions, the film thicknesses of both are the same (film thickness 100 nm). Note that the transmittance of the anode electrode and the gate electrode is small (transmittance: 1% or less (visible transmission region)), and both electrodes are in an opaque state.

Next, the hole injection layer 30 was laminated so as to cover the anode electrode and the gate electrode formed on the surface of the transparent glass substrate (corresponding to the transparent substrate 1, see FIG. 1). MoO ₃ (“Molybdenum trioxide” manufactured by Japan High Purity Chemical Co., Ltd.) was used as the material for the hole injection layer 30, and the hole injection layer 30 having a thickness of 62 nm was formed on the transparent glass substrate by vacuum deposition. . Next, a buffer layer 31 was stacked on the upper surface of the hole injection layer 30. As a material of the buffer layer 31, PEDOT (“polyethylenedioxythiophene” manufactured by HC Starck) was used, and a buffer layer having a thickness of 30 nm was laminated by a spin coating method. Next, the hole transport layer 32 was laminated on the upper surface of the buffer layer 31. As a material for the hole transport layer 32, TPD (N, N′-diphenyl-N, N′-bis (3-methylphenyl) 1-1′biphenyl-4,4′-diamine) (“N, N′-bis (3 -Methylphenyl) -N, N′-diphenylbenzidine (manufactured by Aldrich Co.) was used, and a hole transport layer 32 having a film thickness of 50 nm was laminated by a vacuum deposition method. Next, a charge transporting light emitting layer 33 was laminated on the upper surface of the hole transport layer 32. As a material for the charge transporting light emitting layer 33, Alq3 (“Tris (8-hydroxyquinoline) aluminum” manufactured by Luminescence Technology Co., Ltd.) was used, and the charge transporting light emitting layer 33 having a film thickness of 50 nm was laminated by vacuum deposition. .

  Next, the buffer layer 34 was formed on the upper surface of the charge transporting light emitting layer 33. As the buffer layer 34, a LiF film (film thickness: 1 nm) was laminated on the upper surface of the charge transporting light emitting layer 33 by a vacuum deposition method.

Next, the cathode electrode 5 was formed on the upper surface of the buffer layer 34. As the cathode electrode 5, an Al film (thickness 70 nm) was formed on the upper surface of the buffer layer 34 by vacuum deposition. Sample B was prepared as described above.
<Sample C creation>

  Next, a method for creating Sample C will be described. First, the physical configuration of the created sample C will be described. FIG. 5 is a cross-sectional view showing a physical configuration of the created sample C. As shown in FIG. 5, the light-emitting organic material 4 was formed by laminating a hole transport layer 40, a charge transport light-emitting layer 41, and a buffer layer 42. As shown in FIG. 5, the charge transporting light emitting layer 41 is laminated on the upper surface of the hole transport layer 40, and the buffer layer 42 is laminated on the upper surface of the charge transporting light emitting layer 41. The hole transport layer 40 of the luminescent organic material 4 was disposed so as to be laminated on the transparent substrate 1 so as to cover the anode electrode and the gate electrode formed in a comb shape. Further, the cathode electrode 5 was laminated on the upper surface of the buffer layer 42.

  Next, a method for creating Sample C will be described. An ITO substrate was used as the transparent substrate 1 (see FIG. 1). Then, the ITO film was scraped, and comb-like lines (line width: 2 μm, line interval: 10 μm) of the ITO film were formed on the transparent glass substrate. These were used as an anode electrode and a gate electrode. Note that the anode electrode and the gate electrode have the same film thickness (film thickness 70 nm). Note that the transmittance of the anode electrode and the gate electrode is large (transmittance: 80% or more (visible transmission region)), and both electrodes are in a transparent state.

  Next, the hole transport layer 40 was laminated on the surface of the ITO substrate (corresponding to the transparent substrate 1, see FIG. 1) so as to cover the anode electrode and the gate electrode formed by the ITO film. TPD (“N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine” manufactured by Aldrich) is used as a material for the hole transport layer 40, and a hole transport with a film thickness of 50 nm is formed by vacuum deposition. Layer 40 was laminated. Next, a charge transporting light emitting layer 41 was laminated on the upper surface of the hole transport layer 40. As a material for the charge transporting light emitting layer 41, Alq3 (“Tris (8-hydroxyquinoline) aluminum” manufactured by Luminescence Technology Co., Ltd.) was used, and a charge transporting light emitting layer 33 having a film thickness of 50 nm was laminated by a vacuum deposition method. . Next, the buffer layer 42 was formed on the upper surface of the charge transporting light emitting layer 41. As the buffer layer 42, a LiF film (film thickness: 1 nm) was laminated on the upper surface of the charge transporting light emitting layer 41 by a vacuum deposition method.

Next, the cathode electrode 5 was formed on the upper surface of the buffer layer 42. As the cathode electrode 5, an Al film (film thickness: 70 nm) was laminated on the upper surface of the buffer layer 42 by vacuum deposition. Sample C was prepared as described above.
<Evaluation by luminance measurement>

  Next, with respect to Sample A, Sample B, and Sample C created by the creation method described above, evaluation was performed by changing the voltage conditions applied to the electrodes to emit light and measuring the luminance of the generated light. did.

Sample A, sample B, and sample C were used as samples to be evaluated. Then, the relationship between the applied voltage applied to the anode electrode and the luminance was measured with the conditions of the voltage applied to the gate electrode in each sample set as follows.
Measurement 1: Sample C used. Gate electrode voltage: 5 VDC (cathode electrode voltage: 0 VDC).
Measurement 2: Sample B used. Gate electrode voltage: 5 VDC (cathode electrode voltage: 0 VDC).
Measurement 3: Sample A used. Gate electrode voltage: 5 VDC (cathode electrode voltage: 0 VDC).
Measurement 4: Sample A used. Gate voltage: square-wave AC voltage (frequency: 20 Hz to 15 MHz, amplitude: 10 V, duty ratio: 1/128) (cathode electrode voltage: 0 VDC).
(Sample A: electrode thickness: anode electrode <gate electrode, electrode transparency: opaque)
(Sample B: electrode thickness: anode electrode = gate electrode, electrode transparency: opaque)
(Sample C: electrode thickness: anode electrode = gate electrode, electrode transparency: transparent)

  In addition, “luminance meter BM-3” (manufactured by Topcon Co., Ltd.) was used for luminance measurement. Further, “Semiconductor Parameter Analyzer 4155B” (manufactured by Hewlett-Packard Company) was used as a measuring instrument for applying a voltage to the electrodes during luminance measurement.

  The luminance measurement result will be described with reference to FIG. FIG. 6 is a diagram showing the results of luminance measurement under the conditions of Measurement 1 to Measurement 4. Among the curves shown in FIG. 6, the curve 51 corresponds to the result when the luminance measurement is performed under the condition of measurement 1, the curve 52 corresponds to the result when the luminance measurement is performed under the condition of measurement 2, and the curve 53 Corresponds to the result when the luminance measurement is performed under the condition of measurement 3, and the curve 54 corresponds to the result when the luminance measurement is performed under the condition of measurement 4.

  As shown in FIG. 6, the brightness of the generated light increases as the voltage applied to the anode electrode is increased. Further, under the condition that the applied voltage to the anode electrode is the same, the luminance of light generated in the order of measurement 4 (curve 54), measurement 3 (curve 53), measurement 2 (curve 52), and measurement 1 (curve 51). Is getting bigger. In measurement 4 (curve 54), when the voltage of the anode electrode is 7.5 V, 30 arb. A luminance higher than unit is obtained. Further, when the turn-on voltage, which is a driving voltage necessary for starting light emission, is compared between the respective measurement results, the turn-on voltage under the conditions of measurement 1 to measurement 3 (curve 51 to curve 53) is about 3V. On the other hand, the turn-on voltage under the condition of the measurement 4 (curve 54) is about 2.5 V, and it can be issued at a lower voltage.

  When the voltage of the anode electrode (horizontal axis in FIG. 6) is the same, the luminance in the measurement 2 result (curve 52) is higher than the measurement 1 result (curve 51) (for example, the anode Under conditions of voltage: 7.5 V, measurement 1 (curve 51): about 10 arb.unit, measurement 2 (curve 52): about 15 arb.unit). The difference between the conditions for measurement 1 and the conditions for measurement 2 is that the anode electrode and the gate electrode are transparent (measurement 1 (curve 51): transparent, measurement 2 (curve 52): opaque). Therefore, it has been found that the organic EL element can emit light with high luminance by reducing the transmittance of the anode electrode and the gate electrode to make it opaque.

  In addition, when the voltage of the anode electrode (horizontal axis in FIG. 6) is the same, the luminance in the measurement 3 result (curve 53) is higher than the measurement 2 result (curve 52) (for example, Measurement 2 (curve 52): about 15 arb.unit, measurement 3 (curve 53): about 20 arb.unit) under conditions of anode voltage: 7.5V. The difference between the conditions of measurement 2 and the conditions of measurement 3 is that the thickness of the gate electrode 3 is larger than the thickness of the anode electrode (measurement 2 (curve 52): anode electrode = gate electrode, measurement 3). (Curve 53): Anode electrode <gate electrode). Therefore, it was found from this that the organic EL element can emit light with high luminance by making the thickness of the gate electrode larger than the thickness of the anode electrode.

  In addition, when the voltage of the anode electrode (horizontal axis in FIG. 6) is the same, the luminance in the measurement 4 result (curve 54) is significantly higher than the measurement 3 result (curve 53) ( For example, measurement 3 (curve 53): about 20 arb.unit, measurement 4 (curve 54): 30 arb.unit or more under the condition of anode voltage: 7.5 V). The difference between the condition of measurement 3 and the condition of measurement 4 is that a DC voltage or an AC voltage is applied to the gate electrode (measurement 3 (curve 53): DC voltage, measurement 4 (curve 54)). : AC voltage). Therefore, it has been found that when an alternating voltage is applied to the gate electrode 3, the organic EL element can emit light with high luminance.

  Further, the turn-on voltage is lower when the measurement 4 (curve 54) is used than when the measurement 1 to measurement 3 (curve 51 to 23) are used (measurement 1 to measurement 3 (curve 54). 51-curve 53): about 3V, measurement 4 (curve 54): about 2.5V). The difference between the conditions of measurement 1 to measurement 3 and the condition of measurement 4 is that a DC voltage or an AC voltage is applied to the gate electrode 3 (measurement 1 to measurement 3 (curve 51 to curve 53)). : DC voltage, measurement 4 (curve 54): AC voltage). Therefore, it has been found that when an alternating voltage is applied to the gate electrode 3, the organic EL element can emit light with a low turn-on voltage.

  In this measurement, the types of the light-emitting organic materials 4 in Sample A, Sample B, and Sample C used as samples were different. Therefore, it is recalled that the difference in luminance described above is caused by the difference in the luminescent organic material 4. However, it has been confirmed by experiments that when the voltage is applied to each of the light-emitting organic materials 4 under the same electrode structure conditions, almost the same luminance can be obtained. Therefore, it can be determined that the reason for the difference in luminance is simply due to the electrode structure.

  As described above, the anode electrode 2 and the gate electrode 3 are arranged in a planar shape in a comb shape on the transparent substrate 1, and the thickness of the gate electrode 3 is adjusted to be larger than the thickness of the anode electrode 2. A conventional two-terminal organic EL device is formed by reducing the transmittance of at least one of the anode electrode 2 and the gate electrode 3 to make it opaque and applying an alternating voltage to the gate electrode 3 to cause the light-emitting organic material 4 to emit light. It has been clarified that the organic EL element 10 can emit light with higher luminance and lower turn-on voltage than the element.

2 is a cross-sectional view showing a physical configuration of an organic EL element 10. FIG. 1 is an electrical configuration diagram of an organic EL element 10. FIG. It is sectional drawing which shows the physical structure of the produced organic EL element 10 (sample A). It is sectional drawing which shows the physical structure of the produced sample B. FIG. It is sectional drawing which shows the physical structure of the created sample C. FIG. It is a figure which shows the brightness | luminance measurement result of a 3 terminal organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode electrode 3 Gate electrode 4 Luminescent organic material 5 Cathode electrode 20 Hole injection layer 21 Buffer layer 22 Hole transport layer 23 Light emitting layer 24 Charge transport layer 25 Buffer layer 30 Hole injection layer 31 Buffer layer 32 Hole transport layer 33 Charge transporting light emitting layer 34 Buffer layer 40 Hole transporting layer 41 Charge transporting light emitting layer 42 Buffer layer

Claims (3)

A transparent substrate;
An anode electrode and a gate electrode arranged in a planar shape on the surface of the transparent substrate, both of which are alternately arranged in a comb shape;
A light-emitting organic material that is an organic material that is laminated on a surface of the transparent substrate on which the anode electrode and the gate electrode are disposed, and that includes at least a light-emitting material;
An organic EL element having a planar electrode comprising a cathode electrode laminated on a surface opposite to a surface in contact with the transparent substrate in the light emitting organic material,
A planar light emitting device that emits light from the light-emitting organic material by applying a DC voltage between the anode electrode and the cathode electrode and applying an AC voltage between the gate electrode and the cathode electrode. An organic EL device having an electrode.   2. The organic EL element having a planar electrode according to claim 1, wherein the thickness of the gate electrode is larger than the thickness of the anode electrode.   3. The organic EL element having a planar electrode according to claim 1, wherein at least one of the anode electrode and the gate electrode is opaque.

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