JP2007207916A - Organic el display and organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL display and an organic EL element using a triplet light emitting material, wherein a drive voltage is decreased and a production step is simplified. <P>SOLUTION: The organic EL display is provided with a plurality of light emitting elements with a different luminescent color which each of them has a plurality of light emitting layers which are different from each other in the luminescent color as a light emitting layer 5. In at least one type of light emitting layer of the plurality of light emitting layers with the different luminescent color, the light emitting material which emits a light through a triplet exciting state is used as a radiative dopant, and in the light emitting layer using the light emitting material, an electronic transportational zinc complex is used as a host material. In the plurality of light emitting elements with the different luminescent color, a hole implantation electrode 2, a hole transport layer 4, an electronic transport layer, and an electronic implantation electrode 7 are composed of the same composition, and each element has the same element structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence (EL) display and an organic electroluminescence (EL) element.

  The organic EL display has various features such as a wide viewing angle, high contrast, fast response speed, and light weight and thinness, and is expected as a display for portable devices. However, since the portable device is battery-driven, it is required to reduce the power consumption of the display in order to suppress battery consumption. In addition, as the price of portable devices decreases, there is a demand for cost reduction of displays as parts.

  As the organic EL display, a passive type and an active type are known. In the active type, an organic EL element is laminated on a thin film transistor (TFT) substrate. The passive type has a simple matrix structure in which an organic EL element is laminated on a processed transparent electrode. Since the active type is a static drive capable of individually controlling pixels, it is advantageous in terms of life and power consumption compared to the passive type of line sequential driving.

  In addition, as a full color method, three types of methods are generally known: a combination method of white light emission and a color filter, a combination method of blue light emission and a color conversion filter, and a RGB color separation method. Among these, the combination method of white light emission and color filter and the combination method of blue light emission and color conversion filter are simple in manufacturing process because the white light emission layer or blue light emission layer is applied to the entire surface of the substrate. There is a disadvantage that color reproducibility is low. On the other hand, in the case of the RGB coating method, a process of separately coating the three primary colors R (red), G (green), and B (blue) using a mask process is required, which complicates the manufacturing process.

  However, the color reproducibility is higher than the other methods described above, and the RGB color separation method is superior as a full-color display. In addition, it has excellent characteristics in terms of reduction of power consumption and life. This is because a color filter is not used unlike the other methods described above. When a color filter is used, light is absorbed by the color filter, resulting in a decrease in emission intensity. Since the display needs to have a predetermined luminance, the applied power and voltage must be increased, and the load on the element increases. On the other hand, in the case of the RGB coating method, since there is no color filter, the emission intensity does not decrease. Therefore, the load on the element is reduced, which is advantageous in terms of life and power consumption.

  In the RGB coating method, the three types of RGB organic EL elements are independent individual elements. Therefore, in order to improve the performance of the entire organic EL display, it is necessary to improve the performance of each element. Therefore, attention is focused on triplet light-emitting materials. Usually, organic molecules can be divided into two types of singlet excitons and triplet excitons depending on the direction of spin of electrons when excited energy is obtained. As a physical existence probability, the ratio of singlet excitons to triplet excitons is 1: 3, and triplet excitons have a higher existence probability than singlet excitons. Therefore, theoretically, if a triplet light emitting material is used, the light emission efficiency is improved. When the light emission efficiency is increased, power to be supplied to the element is reduced, and power consumption can be reduced as a whole display.

  As described above, the triplet light-emitting material can theoretically be expected to improve the light emission efficiency, but has not been used in practice so far. This is because most triplet light-emitting materials exhibit high light emission efficiency at extremely low temperatures, but no material exhibits high light emission efficiency at room temperature.

  However, in 1999, Bald et al. Of Princeton University found an iridium complex exhibiting high luminous efficiency even at room temperature, and showed the usefulness of a triplet light emitting material (Non-patent Document 1). By using this triplet light emitting material in the RGB coating method, power consumption can be greatly reduced.

  Among triplet light emitting materials, iridium complexes that are stable in red and green and exhibit high efficiency are known at the mass production level. However, in blue, a triplet light-emitting material that is stable and exhibits high efficiency has not been found, and at present only a singlet light-emitting material is used for blue. Therefore, in a mass production level full color display, a triplet light emitting material is used as a red and green light emitting material, a singlet light emitting material is used as a blue light emitting material, or a triplet light emitting material is used as a red light emitting material. A combination using singlet light emitting materials as blue and green light emitting materials is realistic.

  Thus, when the element of the singlet light emitting material and the element of the triplet light emitting material are combined, problems occur in the characteristics and manufacturing of the element. As shown in Non-Patent Document 1, a hole block layer is used in an element structure using a triplet light emitting material. The hole blocking layer is inserted between the light emitting layer and the electron transport layer. As the hole block material, a material whose absolute value of HOMO is sufficiently larger than the constituent material of the light emitting layer is used. Thereby, it is possible to prevent holes from penetrating from the light emitting layer to the electron transport layer without causing recombination. Therefore, the recombination probability in the light emitting layer is increased, and the light emission efficiency is improved. CBP used as a host material in Non-Patent Document 1 is a material that is often used as a triplet light-emitting material. Usually, this material has a polar property, but rather has a hole transport property. Since it is strong, holes easily enter the light emitting layer, resulting in excessive holes. And a part of it penetrates from the light emitting layer to the electron transport layer without recombination. In order to prevent this, a hole block layer is inserted. However, when the hole block layer is inserted, the drive voltage of the element increases. This is because the absolute value of the HOMO of the hole block layer is sufficiently larger than the constituent material of the light emitting layer, so that an injection barrier is generated there.

  Therefore, a device using a triplet light emitting material has a high voltage characteristic. In the case of R, G, and B, since it is combined with a singlet light emitting material, an imbalance of driving voltages occurs between the element of the singlet light emitting material and the element of the triplet light emitting material. That is, an element made of a singlet light emitting material having no hole blocking layer has a low driving voltage, and an element made of a triplet light emitting material having a hole blocking layer has a high driving voltage. When combined with TFTs in an active display, the power supply voltage is shared by the RGB sub-pixels due to the configuration of the drive circuit. That is, if there is a sub-pixel having a high drive voltage among RGB, the power supply voltage must be set higher in accordance with the voltage. As a result, the power consumption of the entire display increases. An element made of a singlet light-emitting material capable of emitting light even when the voltage is low applies a high voltage unnecessarily, resulting in a large loss of power consumption. In order to prevent such a problem, it is necessary to shift the respective RGB voltages to the lower side to minimize the difference.

  The problem on the manufacturing side in the element of the triplet light emitting material is that the number of layers is increased by one by inserting the hole blocking layer as compared with the element of the singlet light emitting material. An increase of one layer causes an increase in cost. In terms of characteristics, each element of RGB is independent, but from the viewpoint of manufacturing, in order to simplify the process, it is necessary to make the layers that can be shared as common as possible. That is, the light emitting layer needs to be manufactured individually at least in order to produce each color of RGB, but a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, etc. may be shared. desirable. By using a common material, it is possible to collect the materials charged in the source for forming the thin film. As a result, it is possible to reduce the cost of the display by reducing the material cost, suppressing the capital investment by reducing the number of chambers of the manufacturing apparatus, and improving the productivity by reducing the tact time.

  However, in the case of a conventional triplet light emitting material element, since the hole block layer has to be inserted as described above, it has been difficult to make the layers common.

Patent Document 1 discloses a problem caused by a difference in driving voltage between an element of a singlet light emitting material and an element of a triplet light emitting material in an RGB color separation type display. In this document, since the light emission efficiency of the element of the triplet light emitting material is high, a lower power value than that of the element of the singlet light emitting material may be used in order to obtain a predetermined luminance of the display. Are listed. However, in the case of a triplet light emitting material element, a voltage (horizontal axis) -power (vertical axis) curve is steep in a luminance region (100 to 10000 cd / m ² ) actually used in a display. This means that the voltage change is small with respect to the current change. Therefore, the use of a triplet light emitting material element does not always result in low voltage driving. Patent Document 1 does not describe a specific configuration of a triplet light emitting material element.

Patent Document 2 discloses an electron-transporting zinc complex used as a host material in the present invention. By using this as a host material for a light-emitting layer, there is no need to provide a hole blocking layer, and the driving voltage is reduced. There is no disclosure of what can be done.
JP 2002-2684 A JP 2002-305083 A (MABald, S. Lamansky, PEBurrows, METhompson and SRForrest: Appl. Phys, Lett., 75, 4, (1999))

  An object of the present invention is to provide an organic EL display and an organic EL element that can reduce a driving voltage and simplify a manufacturing process in an organic EL display and an organic EL element using a triplet light emitting material. It is to provide.

  The organic EL display according to the present invention includes a hole injection electrode, an electron injection electrode, a light emitting layer provided between the hole injection electrode and the electron injection electrode, containing a host material and a luminescent dopant, and a hole injection electrode and a light emitting layer. A plurality of light emitting colors different from each other, each having a plurality of light emitting layers having different light emitting colors as the light emitting layer. The hole transporting layer provided between the electron injecting electrode and the light emitting layer. The organic EL display provided with the light emitting element, wherein light emitted from the light emitting layer through a triplet excited state in at least one light emitting layer of a plurality of light emitting layers having different emission colors In the light emitting layer in which the material is used and the light emitting material is used, an electron transporting zinc complex is used as a host material, and the emission color is different. In the number of light emitting elements, the hole injecting electrode, a hole transport layer, an electron transport layer and an electron injecting electrode is made of the same composition, each element is characterized by having the same device structure.

  In the present invention, an electron transporting zinc complex is used as a host material in a light emitting layer in which a light emitting material that emits light via a triplet emission excited state (triplet light emitting material) is used. Thus, there is no need to provide a hole blocking layer between the light emitting layer and the electron transport layer, and in a plurality of light emitting elements having different emission colors such as a red light emitting element, a green light emitting element, and a blue light emitting element, The transport layer, the electron transport layer, and the electron injection electrode can be formed from the same composition. Therefore, since the same element structure can be used in each light emitting element, the manufacturing process can be simplified. In addition, since the driving voltage can be reduced without providing the hole block layer in the element containing the triplet light emitting material, the power consumption of the entire organic EL display can be reduced.

  In the present invention, at least one of a hole injection layer provided between the hole injection electrode and the hole transport layer and an electron injection layer provided between the electron injection electrode and the electron transport layer may be provided. Good. In this case, the hole injection layer and / or the electron injection layer have the same composition in a plurality of light emitting elements having different emission colors, and each layer is provided so that each element has the same element structure.

  The triplet light emitting material used in the present invention is preferably an iridium complex represented by the following general formula (1) or (2).

  (D represents a bidentate monoanionic (-1 valent) ligand. At least one of R1 to R4 is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or Substituted aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted euroridyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, non-substituted A substituted or substituted siloxanyl group and all others are hydrogen, R1 to R4 may be the same or different from each other, n represents an integer of 1 to 3, and m represents 0 to 2 Represents an integer.)

(D represents a bidentate monoanionic (-1 valent) ligand. R5 to R8 are hydrogen, unsubstituted or substituted alkyl group, unsubstituted or substituted alkoxy group, unsubstituted or substituted. Aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted urolidyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, unsubstituted or substituted And R5 to R8 may be the same or different from each other, n represents an integer of 1 to 3, and m represents an integer of 0 to 2.)
At present, triplet light-emitting materials that are stable and highly efficient are red light-emitting materials and green light-emitting materials. Therefore, a plurality of light-emitting layers having different light emission colors are a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer. In some cases, the light emitting layer containing the triplet light emitting material is preferably a red light emitting layer and / or a green light emitting layer.

  When the triplet light emitting material is contained in the red light emitting layer, the electron transporting zinc complex contained as a host material in the red light emitting layer preferably has a benzothiazole derivative as a ligand. It is preferable that it has-(2-hydroxyphenyl) benzothiazole as a ligand.

  The electron-transporting zinc complex used as the host material in the present invention has a strong electron-transporting property and a small hole-transporting property, so that electrons are richer in the light-emitting layer. Therefore, since holes are consumed by recombination, the frequency of holes penetrating from the light emitting layer to the electron transport layer is reduced. This eliminates the need for the hole blocking layer, thereby eliminating the energy barrier between the light emitting layer / hole blocking layer and lowering the voltage.

  When using an electron transporting zinc complex having a benzothiazole derivative as a ligand, in order to cover the low hole transporting property, a hole transporting material such as a tertiary amine compound is used as an assist dopant in the light emitting layer. An appropriate amount may be doped. Thereby, fine adjustment of the carrier balance can be performed, and the light emission efficiency and the life can be improved. In addition, NPB etc. which are demonstrated in an Example can be used as a tertiary amine compound.

  When the triplet light emitting material is contained in the green light emitting layer, the triplet light emitting green light emitting material has higher excitation energy than the triplet light emitting red light emitting material. When the zinc complex is added as a host material to the green light emitting layer, the host material may emit light. In such a case, it is preferable to use a host material having higher excitation energy. As such a host material, a zinc complex having a benzoxazole derivative as a ligand is preferably used. In particular, a zinc complex having 2- (2-hydroxyphenyl) benzoxazole as a ligand is preferably used. By using such a zinc complex, the driving voltage can be reduced and the power consumption of the organic EL display can be reduced.

  The organic EL device of the present invention includes a hole injecting electrode, an electron injecting electrode, a light emitting layer containing a host material and a luminescent dopant, a hole injecting electrode, and a light emitting layer. An organic EL device comprising a hole transport layer provided between and an electron transport layer provided between the electron injection electrode and the light emitting layer, wherein the following general formula (1) or (2) And an electron transporting zinc complex is used as a host material.

  (D represents a bidentate monoanionic (-1 valent) ligand. At least one of R1 to R4 is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or Substituted aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted euroridyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, non-substituted A substituted or substituted siloxanyl group and all others are hydrogen, R1 to R4 may be the same or different from each other, n represents an integer of 1 to 3, and m represents 0 to 2 Represents an integer.)

(D represents a bidentate monoanionic (-1 valent) ligand. R5 to R8 are hydrogen, unsubstituted or substituted alkyl group, unsubstituted or substituted alkoxy group, unsubstituted or substituted. Aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted urolidyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, unsubstituted or substituted And R5 to R8 may be the same or different from each other, n represents an integer of 1 to 3, and m represents an integer of 0 to 2.)
As the electron transport layer zinc complex used in the organic EL device of the present invention, the electron transport zinc complex described in the organic EL display of the present invention can be used.

  In the organic EL device of the present invention, since the electron transporting zinc complex is used as the host material of the light emitting layer, it is not necessary to provide a hole blocking layer between the light emitting layer and the electron transport layer, and the driving voltage is reduced. be able to. Therefore, the manufacturing process can be simplified.

  Examples of the iridium complex that can be used as the triplet light emitting material in the organic EL display and the organic EL element of the present invention include those represented by the general formulas (1) and (2) as described above.

  In the iridium complex represented by the general formula (1), R3 and R4 are more preferably hydrogen. Furthermore, R1, R3 and R4 are preferably hydrogen. Particularly preferably, R1, R3 and R4 are hydrogen and R2 is hydrogen or an unsubstituted or substituted alkyl group.

  Preferable specific examples of the iridium complex represented by the general formula (1) include those having the structures shown below.

  In the iridium complex represented by the general formula (2), more preferably, R5 to R8 are hydrogen or an unsubstituted or substituted alkyl group. In the general formula (2), it is more preferable that n = 3 and m = 0.

  Preferable specific examples of the iridium complex represented by the general formula (2) include the following.

  In the organic EL display of the present invention, an electron transporting zinc complex is used as a host material in a light emitting layer in which a triplet light emitting material is used. By using the electron transporting zinc complex, it is not necessary to provide a hole blocking layer which has been conventionally required between the light emitting layer and the electron transporting layer. For this reason, in light emitting elements having different emission colors, such as a red light emitting element, a green light emitting element, and a blue light emitting element, the driving voltage is reduced even if the layers constituting each element have the same composition and each element has the same element structure. Power consumption can be reduced.

  Moreover, since each light emitting layer element has the same element structure, each layer of each element can be formed simultaneously, and the manufacturing process can be simplified. Therefore, it can be produced at low cost and the production amount can be greatly increased.

  In the organic EL device of the present invention, a specific iridium complex that is a triplet light emitting material is used as a light emitting dopant, and an electron transporting zinc complex is used as a host material. Hole penetration can be suppressed, and it is no longer necessary to provide a hole blocking layer, which was conventionally required. For this reason, a drive voltage can be reduced and luminous efficiency can be improved.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

Example 1
FIG. 1 is a schematic cross-sectional view showing the organic EL element of this example. Referring to FIG. 1, a hole injection electrode 2, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, an electron transport / electron injection layer 9, and an electron injection electrode 7 are sequentially stacked on a glass substrate 1. ing.

  Specifically, the organic EL device having the above structure was produced as follows.

First, the substrate on which the indium-tin oxide (ITO) film was formed on the glass substrate 1 was subjected to ultrasonic cleaning twice with isopropyl alcohol for 5 minutes, and the substrate surface was subjected to O ₂ plasma treatment. Next, a hole injection layer 3 (thickness 1 nm) made of a CFx film was formed on the hole injection electrode 2 made of ITO by a fluorocarbon film forming apparatus. Next, a hole transport layer 4 (thickness 50 nm), a light emitting layer 5 (thickness 40 nm), an electron transport / electron injection layer 9 (thickness 20 nm), and electron injection are formed on the hole injection layer 3 using a vacuum vapor deposition machine. The electrode 7 was formed by sequentially stacking by a vacuum vapor deposition method. The hole transport layer 4 was formed from NPB. The light emitting layer 5 was formed using ZnBTZ which is an electron transporting zinc complex as a host material and using Compound 1 as a dopant material. Compound 1 is a triplet light emitting material dopant, and was used at a content of 6 wt% with respect to the host material. The electron injection layer 9 was formed from Alq and Cs. The ratio of Alq to Cs is 1: 1. The electron injection electrode 7 was formed by laminating aluminum having a thickness of 200 nm on lithium fluoride having a thickness of 1 nm. The light emitting layer 5 was formed by a co-evaporation method in which the host material and the dopant material were simultaneously heated and evaporated. In addition, the vapor deposition was performed under the condition that each layer had a degree of vacuum of 1 × 10 ⁻⁶ Torr and no substrate temperature control.

  NPB is N, N′-di (naphthasen-1-yl) -N, N′-diphenylbenzidine and has the following structure.

  ZnBTZ is bis [2- (2-hydroxyphenyl) -benz-1,3-thiazolato] zinc (II) and has the following structure.

  Compound 1 is bis [2- (3-methylphenyl) quinoline] iridium (III) acetylacetonate and has the following structure.

  Alq is tris- (8-quinolinato) aluminum (III) and has the following structure.

The organic EL device obtained as described above was measured for light emission characteristics. The light emission characteristics were measured by applying a voltage while biasing the hole injection electrode positive and the electron injection electrode negative. By applying voltage, red light emission based on Compound 1 (peak wavelength: 620 nm, chromaticity (0.66, 0.34)) was observed. In the initial characteristics, the driving voltage at a current density of 10 mA / cm ² is 3.2 V, the current efficiency is 7.3 cd / A, the power (power) efficiency is 7.2 lm / W, and the external quantum yield is It was 6.5%. The luminance half-life when this device was continuously driven at 1000 cd / m ² was 200 hours.

(Example 2)
An organic EL device was produced in the same manner as in Example 1 except that Compound 2 was used as the light-emitting dopant material instead of Compound 1.

When the emission characteristics were measured in the same manner as in Example 1, red emission (peak wavelength: 629 nm, chromaticity (0.65, 0.35)) based on Compound 2 was observed. The driving voltage at a current density of 10 mA / cm ² is 3.2 V, the current efficiency is 6.8 cd / A, the power (power) efficiency is 6.7 lm / W, and the external quantum yield is 6.5%. Met. In addition, the luminance half life when this device was continuously driven at 1000 cd / m ² was 756 hours.

  Compound 2 is bis [2- (3-methylphenyl) -3-methylquinoline] iridium (III) acetylacetonate, and has the following structure.

(Comparative Example 1)
The host material in the light-emitting layer was changed from ZnBTZ to CBP, and an organic layer was formed in the same manner as in Example 1 except that a hole blocking layer (thickness 10 nm) made of BAlq was provided between the light-emitting layer and the electron transport / electron injection layer. An EL element was produced.

As a result of measuring the light emission characteristics of this organic EL device, red light emission (peak wavelength: 620 nm, chromaticity (0.66, 0.34)) based on Compound 1 was observed. The driving voltage at a current density of 10 mA / cm ² is 7.3 V, the current efficiency is 7.2 cd / A, the power (power) efficiency is 3.2 lm / W, and the external quantum yield is 5.3%. Met. The luminance half-life when this device was continuously driven at 1000 cd / m ² was 160 hours.

  CBP is 4,4′-N, N′-dicarbazole-biphenyl and has the following structure.

  BAlq is bis (2-methyl-8-quinolinolato) -4-phenylphenolato aluminum (III) and has the following structure.

(Comparative Example 2)
An organic EL device was produced in the same manner as in Example 1 except that the light-emitting dopant in the light-emitting layer was changed to BTPIr. Note that BTPIr is a red-emitting iridium complex which is a triplet light-emitting material disclosed in Patent Document 2. As a result of measuring the light emission characteristics of the obtained organic EL device, red light emission (chromaticity (0.67, 0.32)) based on BTPIr was observed. The driving voltage at a current density of 10 mA / cm ² is 3.2 V, the current efficiency is 2.5 cd / A, the power efficiency is 2.5 lm / W, and the external quantum yield is 3.2%. Met. Further, the luminance half-life when this device was continuously driven at 1000 cd / m ² was 31 hours.

  BTPIr is bis (benzothienylpyridine) iridium (III) acetylacetonate and has the following structure.

  The measurement results of the light emission characteristics of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are summarized in Table 1.

  As is clear from the comparison between Example 1 and Comparative Example 1, the organic EL element of Example 1 using ZnBTZ which is the host material of the present invention has a structure without a hole blocking layer. The current efficiency is comparable to that of an organic EL device using CBP as a host material, and the driving voltage shows a value significantly reduced as compared with Comparative Example 1, indicating that high power efficiency can be obtained.

  As is clear from comparison with Example 1 and Comparative Example 2, when the triplet light-emitting material disclosed in Patent Document 2 is used, the light emission characteristics are low and the luminance half-life is shortened. Recognize.

(Example 3)
Organic EL in the same manner as in Example 1 above, except that 80 wt% ZnBTZ and 20 wt% NPB were used as the host material of the light emitting layer, and 6 wt% of Compound 1 was used as the light emitting dopant with respect to these host materials. An element was produced. Here, NPB is used as an assist dopant.

As a result of measuring the light emission characteristics of the obtained organic EL device, red light emission (peak wavelength: 620 nm, chromaticity (0.66, 0.34)) based on Compound 1 was observed. The driving voltage at a current density of 10 mA / cm ² is 3.4 V, the current efficiency is 8.6 cd / A, the power (power) efficiency is 7.9 lm / W, and the external quantum yield is 8.9%. Met. In addition, the luminance half-life when this device was continuously driven at 3000 cd / m ² was 900 hours.

Example 4
An organic EL device was produced in the same manner as in Example 3 except that Compound 2 was used instead of Compound 1 as the dopant material.

When the light emission characteristics of the obtained organic EL device were measured, red light emission (peak wavelength: 629 nm, chromaticity (0.65, 0.34)) based on Compound 2 was observed. The driving voltage at a current density of 10 mA / cm ² was 3.3 V, the current efficiency was 10 cd / A, the power (power) efficiency was 9.5 lm / W, and the external quantum yield was 11%. Further, the luminance half-life when this device was continuously driven at 3000 cd / m ² was 2000 hours.

  The measurement results of Example 3 and Example 4 are shown in Table 2.

  As apparent from the comparison with Example 1 and Example 2 shown in Table 1, the luminance half-life can be increased and the device stability can be improved by including the assist dopant material in the light emitting layer. I understand.

(Example 5)
ZnOXD is used as the host material of the light emitting layer, compound 3 is used as the light emitting dopant material so as to be 8% by weight with respect to the host material, and the thickness of the light emitting layer is set to 50 nm. An organic EL element was produced.

When the light emission characteristics of the obtained organic EL device were measured, green light emission (peak wavelength: 520 nm, chromaticity (0.29, 0.63)) based on Compound 3 was observed. The driving voltage at a current density of 10 mA / cm ² was 5.6 V, the current efficiency was 39 cd / A, the power (power) efficiency was 22 lm / W, and the external quantum yield was 11%.

  ZnOXD is bis [2- (2-hydroxyphenyl) -benz-1,3 oxazolate] zinc (II) and has the following structure.

  Compound 3 is tris (2-phenylpyridine) iridium (III) and has the following structure.

(Comparative Example 3)
The same as in Example 5 except that CBP is used as the host material in the light emitting layer and a hole blocking layer (thickness 10 nm) made of BAlq is provided between the light emitting layer and the electron transport / electron injection layer as in Comparative Example 1. An organic EL element was produced.

When the light emission characteristics of the obtained organic EL device were measured, green light emission (peak wavelength: 520 nm, chromaticity (0.27, 0.63)) based on Compound 3 was observed. The driving voltage at a current density of 10 mA / cm ² was 7.0 V, the current efficiency was 29 cd / A, the power (power) efficiency was 13 lm / W, and the external quantum yield was 8.3%.

  The measurement results of Example 5 and Comparative Example 3 are shown in Table 3.

  From the results of Example 5 and Comparative Example 3, the organic EL element using ZnOXD as the host material exceeds the organic EL element of Comparative Example 3 using CBP as the host material, even if the structure does not have a hole blocking layer. It can be seen that the current efficiency is shown, and that the driving voltage is significantly lower and the power efficiency is higher.

(Example 6)
An organic EL device was produced in the same manner as in Example 1 except that Compound 4 was used as the light emitting dopant material of the light emitting layer.

When the emission characteristics of the obtained organic EL device were measured, red light emission (peak wavelength: 629 nm, chromaticity (0.68, 0.32)) based on Compound 4 was observed. The driving voltage at a current density of 10 mA / cm ² is 3.4 V, the current efficiency is 8.6 cd / A, the power (power) efficiency is 7.9 lm / W, and the external quantum yield is 12.2%. Met. Further, the luminance half-life when this device was continuously driven at 3000 cd / m ² was 1000 hours.

  Compound 4 is tris (phenylisoquinoline) iridium (III) and has the following structure.

(Example 7)
An organic EL device was produced in the same manner as in Example 3 except that Compound 4 was used as the light emitting dopant material of the light emitting layer. When the light emission characteristics of the obtained organic EL device were measured, red light emission (peak wavelength: 629 nm, chromaticity (0.68, 0.32)) based on Compound 4 was observed. The driving voltage at a current density of 10 mA / cm ² is 3.5 V, the current efficiency is 8.9 cd / A, the power efficiency is 8.2 lm / W, and the external quantum yield is 12.3%. Met. Further, the luminance half-life when this device was continuously driven at 3000 cd / m ² was 1000 hours.

  The measurement results of Example 6 and Example 7 are shown in Table 4.

  As is apparent from the results shown in Table 4, it can be seen that the effects of the present invention can also be obtained when Compound 4 is used as the triplet light emitting material.

<Production of organic EL display>
FIG. 2 is a plan view showing an organic EL display according to the present invention, and FIG. 3 is a cross-sectional view.

  In FIG. 2, an organic EL element 100R that is a red light emitting element, an organic EL 100G that is a green light emitting element, and an organic EL element 100B that is a blue light emitting element are provided in order from the left.

  Each organic EL element 100R, 100G, and 100B is formed in a region surrounded by two gate signal lines 51 extending in the row direction and two drain signal lines (data lines) 52 extending in the column direction. Within each organic EL element region, a first TFT 130 as a switching element is formed near the intersection of the gate signal line 51 and the drain signal line 52, and each organic EL element 100R, 100G, and 100B is formed near the center. A second TFT 140 for driving is formed. In addition, an auxiliary capacitor 70 and a hole injection electrode (anode) 2 made of ITO are formed in the regions of the organic EL elements 100R, 100G, and 100B. Each organic EL element 100R, 100G, and 100B is formed in an island shape in the region of the hole injection electrode 2.

  The drain of the second TFT 130 is connected to the drain signal line 52 through the drain electrode 13d, and the source of the first TFT 130 is connected to the electrode 55 through the source electrode 13s. The gate electrode 111 of the first TFT 130 extends from the gate signal line 51.

  The auxiliary capacitor 70 includes an SC line 54 that receives the power supply voltage Vsc, and an electrode 55 that is integrated with the active layer 11 (see FIG. 6).

  The drain of the second TFT 140 is connected to the hole injection electrode 2 of each organic EL element via the drain electrode 43d, and the source of the second TFT 140 is connected to the power supply line 53 extending in the column direction via the source electrode 43s. Is done. The gate electrode 41 of the second TFT 140 is connected to the electrode 55.

  As shown in FIG. 3, an active layer 11 made of polycrystalline silicon or the like is formed on a glass substrate 10, and a part of the active layer 11 becomes a second TFT 140 for driving the organic EL element. . A gate electrode 41 having a double gate structure is formed on the active layer 11 via a gate oxide film (not shown), and the interlayer insulating film 13 and the first flat surface are formed on the active layer 11 so as to cover the gate electrode 41. The forming layer 15 is formed. As a material of the first planarization layer 15, for example, an acrylic resin can be used. A transparent hole injection electrode 2 is formed for each organic EL element on the first planarization layer 15, and an insulating second electrode is formed on the first planarization layer 15 so as to cover the hole injection electrode 2. A planarization layer 18 is formed. The second TFT 140 is formed under the second planarization layer 18.

  A hole transport layer 4 is formed on the entire region so as to cover the hole injection electrode 2 and the second planarization layer 18.

  On the hole transport layer 4 of each organic EL element 100R, organic EL element 100G, and organic EL element 100B, a striped red light emitting layer 5R, green light emitting layer 5G, and blue light emitting layer 5B extending in the column direction are formed. Yes. In the red light emitting layer 5R and / or the green light emitting layer 5G, a triplet light emitting material is used according to the present invention, and an electron transporting zinc complex is used as a host material.

  The boundary between the striped red light emitting layer 5R, the green light emitting layer 5G, and the blue light emitting layer 5B is provided in a region parallel to the glass substrate 10 on the surface of the second planarizing layer 18.

  An electron transport layer 8 and an electron injection layer 6 are formed on the red light emitting layer 5R, the green light emitting layer 5G, and the blue light emitting layer 5B of the organic EL element 100R, the organic EL element 100G, and the organic EL element 100B, respectively.

  An electron injection electrode (cathode) 7 is formed on the electron injection layer 6. A protective layer 34 made of resin or the like is formed on the electron injection electrode 7. The light emitting layers 5R, 5G and 5B, the electron transport layer 8, the electron injection layer 6 and the electron injection electrode 7 are simultaneously formed on the respective regions of the organic EL elements 100R, 100G and 100B using a mask. Yes.

  In the organic EL display of this example, as described above, a triplet light emitting material is used for the red light emitting layer 5R and / or the green light emitting layer 5G, and an electron transporting zinc complex is used as a host material. Therefore, it is not necessary to provide a hole block layer between the light emitting layer and the electron transport layer. Therefore, in the organic EL element 100R, the organic EL element 100G, and the organic EL element 100B, the hole injection electrode 2, the hole transport layer 4, the electron transport layer 8, the electron injection layer 6, and the electron injection electrode 7 are configured from the same composition. can do. Therefore, since each organic EL element 100R, 100G, and 100B can be made into the same element structure, each layer of each organic EL element can be formed simultaneously in a manufacturing process. Therefore, the manufacturing process can be simplified and the production efficiency can be increased.

(Example 8)
For the layers other than the light emitting layer, a blue light emitting element, a green light emitting element, and a red light emitting element were produced in the same manner as in the above example.

  For the light emitting layer of the blue light emitting element, TBADN was used as a host material, and 1 wt% TBP was used as a light emitting dopant.

  In the light emitting layer of the green light emitting element, TBADN was used as a host material, and 1 wt% C545T was used as a light emitting dopant.

  In the blue light emitting device, the same light emitting layer as in Example 3 was used.

  TBADN is 2-tertiary-butyl-9,10-di (2-naphthyl) anthracene and has the following structure.

  TBP is 2,5,8,11-tetra-tertiary-butylperylene and has the following structure.

  C545T is 10- (2-benzothiazolyl) -2,3,6,7-tetrahydro-1,1,7,7-tetramethyl1-1H, 5H, 11H- [1] benzopyrano [6,7,8, ij] quinolinidin-11-one, which has the following structure.

The obtained blue light emitting element, green light emitting element, and red light emitting element were measured for light emission characteristics at a current density of 10 mA / cm ² , and the measurement results are shown in Table 5.

  As is apparent from the results shown in Table 5, by using ZnBTZ as the host material of the light emitting layer of the red light emitting device according to the present invention, the driving voltage at the same current value of the blue light emitting device, the green light emitting device, and the red light emitting device. Can be made substantially the same.

Example 9
For the layers other than the light emitting layer, a blue light emitting element was manufactured using a blue triplet light emitting material in the same manner as in the above example.

  A light emitting layer was formed using 2AZM-iPr as a host material and 8 wt% of FIrpic which is a blue triplet light emitting material as a light emitting dopant.

  2AZM-iPr is bis (N-iso-propylsalicylideneaminato) zinc (II) and has the following structure.

  FIrpic is bis [2- (4,6-difluorophenyl) pyridinato] iridium (III) picolinate and has the following structure.

With respect to the obtained blue light-emitting element, the light emission characteristics were measured at a current density of 10 mA / cm ^{2. The} measurement results are shown in Table 6.

  As shown in Table 6, it can be seen that even when a blue triplet light emitting material is used, the driving voltage can be reduced and high luminous efficiency can be obtained.

The typical sectional view showing one example of the organic EL element according to the present invention. The top view which shows one Example of the organic electroluminescent display according to this invention. Sectional drawing which shows one Example of the organic electroluminescent display according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Hole injection electrode 3 ... Hole injection layer 4 ... Hole transport layer 5 ... Light emitting layer 6 ... Electron injection layer 7 ... Electron injection electrode 8 ... Electron transport layer 9 ... Electron transport / electron injection layer

Claims (9)

A hole injection electrode, an electron injection electrode, a light emitting layer containing a host material and a light emitting dopant, provided between the hole injection electrode and the electron injection electrode, and provided between the hole injection electrode and the light emitting layer A hole transport layer, and an electron transport layer provided between the electron injection electrode and the light emitting layer, and each of the light emitting layers includes a plurality of light emitting layers having different light emitting colors, and a plurality of light emitting colors different from each other. An organic EL display provided with a light emitting element,
In at least one light emitting layer of the plurality of light emitting layers having different emission colors, a light emitting material that emits light through a triplet excited state is used as the light emitting dopant, and the light emitting material is used. In the light emitting layer, an electron transporting zinc complex is used as a host material,
In the plurality of light emitting devices having different emission colors, the hole injection electrode, the hole transport layer, the electron transport layer, and the electron injection electrode have the same composition, and each device has the same device structure. Organic EL display.   At least one of a hole injection layer provided between the hole injection electrode and the hole transport layer, and an electron injection layer provided between the electron injection electrode and the electron transport layer is provided; The organic EL display according to claim 1, wherein the hole injection layer and / or the electron injection layer have the same composition in the plurality of light emitting elements having different emission colors, and each element has the same element structure. 3. The organic EL display according to claim 1, wherein the light emitting material that emits light through a triplet excited state is an iridium complex represented by the following general formula (1) or (2): .

(D represents a bidentate monoanionic (-1 valent) ligand. At least one of R1 to R4 is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or Substituted aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted euroridyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, non-substituted A substituted or substituted siloxanyl group and all others are hydrogen, R1 to R4 may be the same or different from each other, n represents an integer of 1 to 3, and m represents 0 to 2 Represents an integer.)

(D represents a bidentate monoanionic (-1 valent) ligand. R5 to R8 are hydrogen, unsubstituted or substituted alkyl group, unsubstituted or substituted alkoxy group, unsubstituted or substituted. Aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted urolidyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, unsubstituted or substituted And R5 to R8 may be the same or different from each other, n represents an integer of 1 to 3, and m represents an integer of 0 to 2.)   The plurality of light emitting layers having different emission colors are a red light emitting layer, a green light emitting layer, and a blue light emitting layer, and the light emitting material that emits light through a triplet excited state is the red light emitting layer and / or the green light emitting layer. It contains in a light emitting layer, The organic electroluminescent display of any one of Claims 1-3 characterized by the above-mentioned.   The light emitting material is contained in the red light emitting layer, and the ligand of the electron transporting zinc complex contained in the red light emitting layer is a benzothiazole derivative. Organic EL display.   6. The organic EL display according to claim 5, wherein the benzothiazole derivative is 2- (2-hydroxyphenyl) -benzothiazole.   The light emitting material is contained in the green light emitting layer, and the ligand of the electron transporting zinc complex contained in the green light emitting layer is a benzoxazole derivative. Organic EL display.   The organic EL display according to claim 7, wherein the benzoxazole derivative is 2- (2-hydroxyphenyl) -benzoxazole. Provided between a hole injection electrode, an electron injection electrode, the hole injection electrode and the electron injection electrode, and provided between a light emitting layer containing a host material and a luminescent dopant, and between the hole injection electrode and the light emitting layer. An organic EL device comprising a hole transport layer and an electron transport layer provided between the electron injection electrode and the light emitting layer,
An organic EL device, wherein an iridium complex represented by the following general formula (1) or (2) is used as the light-emitting dopant, and an electron-transporting zinc complex is used as the host material.

(D represents a bidentate monoanionic (-1 valent) ligand. At least one of R1 to R4 is an unsubstituted or substituted alkyl group, an unsubstituted or substituted alkoxy group, an unsubstituted or Substituted aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted euroridyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, non-substituted A substituted or substituted siloxanyl group and all others are hydrogen, R1 to R4 may be the same or different from each other, n represents an integer of 1 to 3, and m represents 0 to 2 Represents an integer.)

(D represents a bidentate monoanionic (-1 valent) ligand. R5 to R8 are hydrogen, unsubstituted or substituted alkyl group, unsubstituted or substituted alkoxy group, unsubstituted or substituted. Aryloxy group, unsubstituted or substituted arylthio group, unsubstituted or substituted amino group, unsubstituted or substituted urolidyl group, halogen group, hydroxyl group, unsubstituted or substituted silyl group, unsubstituted or substituted And R5 to R8 may be the same or different from each other, n represents an integer of 1 to 3, and m represents an integer of 0 to 2.)

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