JP2011049356A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element which can adjust stable luminescent color. <P>SOLUTION: The organic EL element is formed, by laminating at least two or more layers of the organic light-emitting layers 5b and 5c between an anode and a cathode. At least one layer of the organic light-emitting layers 5b and 5c is made by doping two or more of similar color type luminescent materials 5g, 5h, 5i, and 5j. In the similar color type luminescent materials 5g, 5h, 5i, and 5j, the difference of mutual luminescence peak wavelength is 30 nm or less. The organic light-emitting layers 5b and 5c present different luminescent colors, respectively, and present white luminescent color by color mixture. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic EL (electroluminescence) element, and particularly relates to adjustment of the emission color of an organic EL element.

  2. Description of the Related Art Conventionally, an organic EL element that is a self-luminous element formed of an organic material includes, for example, a first electrode made of ITO (Indium Tin Oxide) that serves as an anode, an organic layer that has at least a light-emitting layer, and aluminum that serves as a cathode. A non-translucent second electrode made of (Al) or the like is sequentially laminated (see, for example, Patent Document 1).

  Such an organic EL element emits light by injecting holes from the first electrode and injecting electrons from the second electrode, and the holes and electrons recombine in the light emitting layer. Organic EL devices have excellent visibility due to self-emission, are excellent in impact resistance because they are completely solid elements, and have excellent responsiveness in low-temperature environments. It is used in in-vehicle display devices such as instruments.

JP 59-194393 A JP 2000-68057 A

  In particular, organic EL elements used in in-vehicle display devices are required to have high reliability even under a wide range of temperature environments, and to emit light with high accuracy in order to improve display quality. Especially for white light, the user can easily recognize the difference in color even within the white chromaticity range such as yellowish white and blueish white, and the emission color is finely adjusted to obtain the white color required for the product. It is requested to do. On the other hand, a method for adjusting the emission color by doping a light emitting layer with a plurality of kinds of light emitting materials is known. For white, for example, as disclosed in Patent Document 2, a method is known in which a plurality of light emitting layers are doped with two or more kinds of fluorescent materials having different colors as a whole. In this method, it is possible to adjust the luminescent color to a desired chromaticity by controlling the concentration ratio of a plurality of types of luminescent materials serving as dopants, and in particular, doping three types of luminescent materials as a whole. The chromaticity can be finely adjusted.

  However, when doping the light emitting materials of different colors in the same light emitting layer, according to the verification by the inventors of the present application, it is necessary to make the respective concentrations greatly different in order to actually adjust to obtain a desired white color. There is a problem that it is actually difficult to control the doping concentration at a ratio such as 20: 1 which is different from the digit, and in the mass production, there is a variation in emission color, and the stable emission color cannot be adjusted. There was a point.

  Therefore, the present invention has been made in view of this problem, and an object of the present invention is to provide an organic EL element capable of stably adjusting the emission color.

  In order to solve the above-mentioned problems, the present invention provides an organic EL device in which at least two or more organic light-emitting layers are laminated between an anode and a cathode, and at least one layer of the organic light-emitting layers includes: It is characterized by being doped with a light emitting material of two or more similar colors.

  Further, the luminescent materials of similar colors are characterized in that the difference in emission peak wavelength between each other is 30 nm or less.

  Further, the concentration of each of the luminescent materials of similar colors is characterized in that the concentration of the luminescent material having a short emission peak wavelength is higher than the concentration of the luminescent material having a long emission peak wavelength.

  The organic light-emitting layers may have different emission colors, and may exhibit a white emission color by mixing colors.

  The present invention relates to an organic EL element, and enables stable adjustment of emission color.

The figure which shows the organic electroluminescent panel to which this invention was applied. The expanded sectional view which shows the organic layer same as the above. The figure which shows the characteristic table | surface of the Example and comparative example of this invention. The CIE chromaticity diagram which shows the chromaticity of the luminescent color in the Example and comparative example of this invention.

  Embodiments in which the present invention is applied to a dot matrix type organic EL panel will be described below with reference to the accompanying drawings.

  In FIG. 1, an organic EL panel includes a support substrate 1, a first electrode (anode) 2, an insulating layer 3, a partition wall 4, an organic layer 5, a second electrode (cathode) 6, and a sealing member. 7 is mainly composed.

  The support substrate 1 is a translucent glass substrate having a rectangular shape.

The first electrode 2 is formed of a light-transmitting conductive material such as ITO (Indium Tin Oxide) in a layer form on the support substrate 1 by a method such as sputtering or vapor deposition, and is patterned in a stripe shape by a photolithography method, for example. It is made. As shown in FIG. 1A, the first electrode 2 has an anode wiring portion 2a and an anode portion 2b. The anode wiring portion 2a is an anode terminal portion for electrically connecting to an external power source at the terminal portion. 2c. The surface of the first electrode 2 is subjected to a surface treatment such as UV / O ₃ treatment or plasma treatment.

  The insulating layer 3 is made of an insulating material such as polyimide or phenol, and is formed in a predetermined shape on a non-light emitting portion on the support substrate 1 by means such as photolithography. The insulating layer 3 is formed between the anode portions 2 b of the first electrode 2 and is formed so as to slightly overlap the first electrode 2 and insulates the first electrode 2 from the second electrode 6. is there.

  The partition wall portion 4 is made of, for example, an insulating material such as a phenol-based material, and has a cross section formed in, for example, a reverse taper shape by means of a photolithography method or the like. The partition wall portion 4 is formed on the first electrode 2 and the insulating layer 3 so as to cross the anode portion 2b at a substantially right angle, and in a portion corresponding to a cathode wiring portion described later on the support substrate 1, FIG. ), The support substrate 1 is formed to have an arc shape when viewed from the laminated body forming surface side.

  The organic layer 5 is formed on the first electrode 2 and the insulating layer 3, and as shown in FIG. 2, the hole injection transport layer 5a, the first light emitting layer (organic light emitting layer) 5b, the second The light emitting layer (organic light emitting layer) 5c, the electron transport layer 5d, and the electron injection layer 5e are sequentially laminated by means such as vapor deposition to form a layer having a thickness of about 60 to 100 nm.

The hole injecting and transporting layer 5a has a function of taking holes from the first electrode 2 and transmitting them to the first and second light emitting layers 5b and 5c. For example, a hole having a high hole mobility such as an amine compound. The transporting material is formed in a layer shape having a film thickness of about 15 to 40 nm by means such as vapor deposition. The hole transporting material has a glass transition temperature of 85 ° C. or higher (more preferably 130 ° C. or higher), a hole mobility of about 4 × 10 ⁻⁴ cm ² / V · s, and an energy gap of 3 About 1 eV.

  The first light-emitting layer 5b is formed by doping the host material 5f with a first dopant 5g and a second dopant 5h as a light-emitting material by means of vapor deposition or the like to form a layer having a thickness of about 15 to 20 nm. . The host material 5f is capable of transporting holes and electrons, and is made of a light-emitting material that emits light when the holes and electrons are transported and recombined. For example, an anthracene derivative having an energy gap of about 3.3 eV Consists of. The first dopant 5g is made of a fluorescent dopant having a function of emitting light in response to recombination of electrons and holes, and exhibits, for example, orange emission as a predetermined emission color. The second dopant 5h is made of a fluorescent dopant having the same color as the first dopant 5g, and emits orange-red light, for example. It should be noted that the doping amounts of the first and second dopants 5g and 5h are preferably configured so as not to cause concentration quenching, and the first light emitting layer 5b has a concentration of 2 to 20%. First and second dopants 5g and 5h are added.

  The second light-emitting layer 5c is composed of the same host material 5f as the first light-emitting layer 5b, the third dopant 5i and the fourth dopant having different emission colors from the first and second dopants 5g and 5h as light-emitting materials. The dopant 5j is doped by means such as vapor deposition to form a layer having a thickness of about 20 to 40 nm. The third dopant 5i is made of a fluorescent dopant that emits blue light, for example, as a predetermined light emission color. The fourth dopant 5j is made of a fluorescent dopant having the same color as the third dopant 5j, and emits blue-green light, for example. The third and fourth dopants 5i and 5j are preferably doped so that the concentration does not cause quenching, and the second light emitting layer 5c has a concentration of 2 to 20%. Third and fourth dopants 5i and 5j are added.

The electron transport layer 5d has a function of transmitting electrons to the first and second light-emitting layers 5b and 5c. For example, an electron transport material such as aluminum quinolinol (Alq ₃ ), which is a chelate compound, is deposited by a vapor deposition method or the like. It is formed in a layered form having a film thickness of about 8 to 30 nm by means. Alternatively, an organic material having an electron mobility of 1 × 10 ⁻⁶ cm ² / V · s or less is used.

  The electron injection layer 5e has a function of injecting electrons from the second electrode 6. For example, lithium fluoride (LiF) is formed in a layer shape having a film thickness of about 0.5 nm by means such as vapor deposition.

  The second electrode 6 is formed by forming a conductive material such as aluminum (Al) or magnesium silver (Mg: Ag) into a layer having a thickness of about 50 to 200 nm by means such as vapor deposition. As a result, the arc-shaped cathode wiring portion 6a and the cathode portion 6b intersecting the first electrode 2 at a substantially right angle are formed (see FIG. 1A). Further, the cathode wiring portion 6 a is electrically connected to the connection wiring portion 8. The connection wiring portion 8a is formed together with the first electrode 2, and is made of the same material ITO. Further, the connection wiring portion 8 is formed with a cathode terminal portion 8a for electrical connection with the external power source at the terminal portion.

  As described above, the first electrode 2, the organic layer 5, and the second electrode 6 are sequentially laminated on the support substrate 1 to obtain an organic EL element. Each of the organic EL elements is arranged in a matrix and becomes each light emitting pixel constituting the light emitting display section.

  The sealing member 7 is formed by forming a molded glass or flat plate member made of, for example, a glass material into a concave shape by an appropriate method such as sandblasting, cutting, and etching. The sealing member 7 is hermetically disposed on the support substrate 1 via an adhesive 7 a made of, for example, an ultraviolet curable epoxy resin, so that the light emitting display unit is sealed between the sealing member 7 and the support substrate 1. Stop. The sealing member 7 is configured to be slightly smaller than the support substrate 1 so that the anode terminal portion 2c of the first electrode 2 and the cathode terminal portion 8a connected to the second electrode 6 are exposed to the outside. The sealing member 7 may have a flat plate shape. In this case, the sealing member 7 is disposed on the support substrate 1 via a spacer.

  As described above, a dot matrix type organic EL panel having a light-emitting display unit made of organic EL elements can be obtained. This organic EL panel emits orange light and blue light by recombining holes from the first electrode 2 and electrons from the second electrode 6 in the first and second light emitting layers 5b and 5c. Thus, white light is emitted from the first electrode 2 side by mixing these colors. In addition, the organic EL panel applies a constant current by selecting one of the plurality of anode portions 2b and the plurality of cathode portions 6b formed in a stripe shape, and the opposite portion of the selected anode portion 2b and cathode portion 6b. The light emitting pixels corresponding to the above are driven to emit light by so-called passive driving.

  In the organic EL device according to the present embodiment, the first light emitting layer 5b is doped with the first and second dopants 5g and 5h, which are light emitting materials of similar colors, and the second light emitting layer 5c has similar colors. The third and fourth dopants 5i and 5j, which are light emitting materials, are doped.

  According to the above configuration, a plurality of light emitting materials to be doped in the light emitting layers 5b and 5c, that is, in the first light emitting layer 5a, the first and second dopants 5g and 5h, and in the second light emitting layer 5b. Can be within a range in which the concentration ratio of the third and fourth dopants 5i and 5j can be stably controlled, and stable emission color adjustment is possible. Note that when the difference in the emission peak wavelength of the luminescent material increases, the difference in concentration also increases and the concentration ratio exceeds the range that can be stably controlled. Therefore, in order to sufficiently obtain the effects of the present invention, the same light emitting layer 5b is obtained. , 5c, it is desirable to use a luminescent material having a difference in emission peak wavelength of 30 nm or less. Further, in each of the light emitting layers 5b and 5c, since electrons and holes easily move from a light emitting material having a short emission peak wavelength to a light emitting material having a longer emission peak wavelength, doping is performed in the same light emitting layer 5b and 5c. The concentration of the same color luminescent material, that is, the concentration of the first and second dopants 5g and 5h in the first light emitting layer 5b, and the third and fourth dopants 5i and 5j in the second light emitting layer 5c. As for the density | concentration, it is desirable that the density | concentration of a luminescent material with a shorter luminescence peak wavelength is higher than the density | concentration of the luminescent material with a longer luminescence peak wavelength.

  The organic EL element in the present embodiment includes the first and second dopants 5g and 5h and the third and third dopants as a plurality of similar-colored luminescent materials in both the first and second light-emitting layers 5b and 5c. Although the fourth dopants 5i and 5j are doped, the present invention is not limited as long as at least one of the plurality of organic light emitting layers is doped with a light emitting material of two or more similar colors.

  In addition, the first light emitting layer 5b in the present embodiment is doped with the first and second dopants 5g and 5h exhibiting an orange light emitting color, and the second light emitting layer 5c has a blue light emitting color. Although the third and fourth dopants 5i and 5j to be presented are doped, in the present invention, each luminescent material doped in the luminescent layer may exhibit other luminescent colors.

  In this embodiment, the host material 5f of the first light emitting layer 5b is a single material. However, in the present invention, a configuration using a plurality of materials as the host material may be used. Similarly, the host material 5f of the second light emitting layer 5c may be configured to use a plurality of materials instead of a single material.

  Further, although the present embodiment is a dot matrix type organic EL panel, the present invention can also be applied to a segment type organic EL panel, and can also be applied to active driving.

  In the present embodiment, the hole injection / transport layer 5a is composed of a single layer. In the present invention, a hole injection layer and a hole transport layer are sequentially stacked to form a hole injection / transport layer. May be composed of a plurality of layers.

  Further, in the present embodiment, the electron transport layer 5d is configured by a single layer, but in the present invention, it may be configured by a plurality of layers.

  The specific effects of the present invention will be described below with further examples. FIG. 3 is a characteristic table showing the configurations of the organic light emitting layers of Examples 1 to 5 and Comparative Examples 1 to 3 and the CIE chromaticity coordinates of the light emission colors shown by the whole organic EL element. The concentration ratio of each material in the light emitting layer in each example and comparative example is set so as to obtain pure white light emission. FIG. 4 is a CIE chromaticity diagram showing chromaticity coordinates of light emission colors of the light emitting material and the organic EL element.

  In Example 1, an organic EL element having the same configuration as that of the organic EL element described in the above embodiment was prepared except that the light emitting material doped in the first light emitting layer 5b was only the second dopant 5h. Is. The first light-emitting layer 5b uses a material that is an anthracene derivative as the host material 5f, and the emission color of the second dopant 5h is A2 (chromaticity coordinates CIE (0.57, 0.41)) in FIG. Using the orange-red fluorescent dopant shown (emission peak wavelength 595 nm), a film was formed by co-evaporation so that the concentration ratio thereof was 20: 1. The second light-emitting layer 5c uses a material that is an anthracene derivative as the host material 5f, and the light emission color of the third dopant 5i as a similar color light-emitting material is B1 (chromaticity coordinates CIE (0.13) in FIG. , 0.2)) is a blue fluorescent dopant (emission peak wavelength: 470 nm), and the fourth dopant 5j has an emission color of B2 (chromaticity coordinates CIE (0.16, 0.33)) in FIG. Using a green fluorescent dopant (emission peak wavelength 483 nm), a film was formed by co-evaporation so that the concentration ratio thereof was 40: 3: 2. In Example 1, by adjusting the film thickness of each light emitting layer 5b, 5c and the dopant concentration of each dopant 5h, 5i, 5j, a line segment A2-B1, B1- connecting A2, B1, B2 on FIG. The light emission color can be adjusted within the region consisting of B2, B2-A2. Then, by adjusting the concentration ratio of each material in each of the light emitting layers 5b and 5c as described above, pure white light emission indicating W1 (chromaticity coordinates CIE (0.33, 0.33)) in FIG. Could get. Further, at this time, although the second light emitting layer 5c is doped with a plurality of types of dopants 5i and 5j, the concentration ratios of the two are not significantly different, so that it is possible to stably obtain pure white light emission. is there.

  In Example 2, an organic EL element having the same configuration as that of the organic EL element described in the above embodiment was prepared except that the first light emitting layer 5b was doped with only the first dopant 5g. Is. The first light-emitting layer 5b uses a material that is an anthracene derivative as the host material 5f, and the emission color of the first dopant 5g is A1 (chromaticity coordinates CIE (0.51, 0.48)) in FIG. Using the orange fluorescent dopant shown (emission peak wavelength 565 nm), a film was formed by co-evaporation so that the concentration ratio thereof was 20: 1. The second light emitting layer 5c was the same as in Example 1. Example 2 adjusts the film thickness of each light emitting layer 5b, 5c and the dopant concentration of each dopant 5g, 5i, 5j, so that line segments A1-B1, B1- The light emission color can be adjusted within the region consisting of B2, B2-A1. Then, by adjusting the concentration ratio of each material in each of the light emitting layers 5b and 5c as described above, pure white light emission indicating W2 (chromaticity coordinates CIE (0.30, 0.36)) in FIG. Could get. Further, at this time, although the second light emitting layer 5c is doped with a plurality of types of dopants 5i and 5j, the concentration ratios of the two are not significantly different, so that it is possible to stably obtain pure white light emission. is there.

  In Example 3, an organic EL element having the same configuration as that of the organic EL element shown in the above embodiment was manufactured except that the light emitting material doped in the second light emitting layer 5c was only the third dopant 5i. Is. The first light-emitting layer 5b uses a material that is an anthracene derivative as the host material 5f, and the orange fluorescent dopant whose emission color is A1 as the first dopant 5g as the same color light-emitting material, and the second dopant 5h as the second dopant 5h Using the orange-red fluorescent dopant having an emission color of A2, a film was formed by co-evaporation so that the concentration ratio thereof was 20: 1: 0.8. In the second light emitting layer 5c, a material that is an anthracene derivative is used as the host material 5f, the blue fluorescent dopant that emits B1 is used as the third dopant 5i, and the concentration ratio thereof is 40: 3. A film was formed by co-evaporation. In Example 3, by adjusting the film thickness of each light emitting layer 5b, 5c and the dopant concentration of each dopant 5g, 5h, 5i, line segments A1-A2, A2- connecting A1, A2, B1 on FIG. The emission color can be adjusted within the region consisting of B1, B1-A1. Then, by adjusting the concentration ratio of each material in each of the light emitting layers 5b and 5c as described above, pure white light emission indicating W3 (chromaticity coordinates CIE (0.31, 0.31)) in FIG. Could get. Further, at this time, although the first light emitting layer 5b is doped with a plurality of types of dopants 5g and 5h, the concentration ratios of the two are not greatly different, so that it is possible to stably obtain pure white light emission. is there.

  In Example 4, an organic EL element having the same configuration as that of the organic EL element described in the above embodiment was manufactured except that the luminescent material doped in the second light emitting layer 5c was only the fourth dopant 5j. Is. The first light emitting layer 5b was the same as in Example 3. The second light-emitting layer 5c uses a material that is an anthracene derivative as the host material 5f, uses the blue-green fluorescent dopant that emits B2 as the fourth dopant 5j, and the concentration ratio thereof is 40: 3. The film was formed by co-evaporation. In Example 4, by adjusting the film thickness of each light emitting layer 5b, 5c and the dopant concentration of each dopant 5g, 5h, 5j, line segments A1-A2, A2- The light emission color can be adjusted within the region consisting of B2, B2-A1. Then, by adjusting the concentration ratio of each material in each light emitting layer 5b, 5c as described above, pure white light emission indicating W4 (chromaticity coordinates CIE (0.33, 0.38)) in FIG. Could get. Further, at this time, although the first light emitting layer 5b is doped with a plurality of types of dopants 5g and 5h, the concentration ratios of the two are not greatly different, so that it is possible to stably obtain pure white light emission. is there.

  In Example 5, an organic EL element having the same configuration as that of the organic EL element shown in the above embodiment was produced. The first light-emitting layer 5b uses a material that is an anthracene derivative as the host material 5f, and the orange-fluorescent dopant that emits A1 as the first dopant 5g as a light-emitting material of the same color, and the second dopant 5h Using the orange-red fluorescent dopant having an emission color of A2, a film was formed by co-evaporation so that the concentration ratio thereof was 20: 1: 0.8. The second light-emitting layer 5c uses a material that is an anthracene derivative as the host material 5f, and as the light-emitting material of the same color, the blue dopant having the emission color B1 in the third dopant 5i and the fourth dopant 5j A film was formed by co-evaporation using the blue-green fluorescent dopant having an emission color of B2 and a concentration ratio of 40: 3: 2. In Example 5, by adjusting the film thickness of each light emitting layer 5b, 5c and the dopant concentration of each dopant 5g, 5h, 5i, 5j, a line segment A1- connecting A1, A2, B1, B2 on FIG. The light emission color can be adjusted within the region composed of A2, A2-B1, B1-B2, and B2-A1. And the pure white light emission which shows W1 on FIG. 4 was able to be obtained by adjusting the density | concentration ratio of each material in each light emitting layer 5b, 5c as mentioned above. Further, at this time, the first and second light emitting layers 5b and 5c are doped with a plurality of types of dopants 5g and 5h and dopants 5i and 5j, respectively, but the concentration ratios of the two are not significantly different. Thus, pure white light emission can be obtained.

(Comparative Example 1)
Comparative Example 1 is the same as the organic EL element shown in the above embodiment except that only one light emitting layer is used and the light emitting layer is doped with a light emitting material having different emission colors (the emission colors are not the same color). An organic EL element having the following structure is produced. The light emitting layer uses a material that is an anthracene derivative as a host material, and the blue fluorescent dopant that emits light of B1 and the orange red fluorescent dopant that emits A2 as the dopant. The film was formed by co-evaporation so that the concentration ratio was 40: 3: 0.05. Although Comparative Example 1 exhibits pure white light emission indicating W5 (chromaticity coordinates CIE (0.30, 0.28)) in FIG. 4, it is difficult to control the two dopants at a ratio that is different in digit. The emission chromaticity changes greatly due to the variation in density ratio, and it is difficult to adjust the emission color stably. In Comparative Example 1, for example, when the concentration ratio of each material in the light emitting layer is 40: 3: 2, orange light emission indicating A3 (chromaticity coordinates CIE (0.56, 0.40)) in FIG. It was confirmed that white light could not be obtained.

(Comparative Example 2)
In Comparative Example 2, an organic EL element having the same configuration as that of the organic EL element described in the above embodiment was prepared except that the first and second light emitting layers were each doped with one kind of light emitting material. is there. The first light-emitting layer uses a material that is an anthracene derivative as a host material, uses the orange-red fluorescent dopant whose emission color is A2 as a dopant, and performs co-evaporation so that the concentration ratio thereof is 20: 1. A film was formed. The second light-emitting layer uses a material that is an anthracene derivative as a host material, uses the blue-green fluorescent dopant that emits B2 as a dopant, and performs co-evaporation so that the concentration ratio thereof is 40: 3. A film was formed. Although Comparative Example 2 shows pure white light emission that becomes W2 (chromaticity coordinates CIE (0.30, 0.36)) in FIG. 4, the adjustment of the light emission color is a line segment connecting A2 and B2 in FIG. This can be performed only on A2-B2, and is insufficient for adjusting the emission color. In Comparative Example 2, for example, the emission color cannot be adjusted to chromaticity coordinates CIE (0.33, 0.33).

(Comparative Example 3)
Comparative Example 3 is the organic EL shown in the above embodiment except that the first light emitting layer is doped with one kind of light emitting material and the second light emitting layer is doped with light emitting materials having different emission colors. An organic EL element having the same configuration as the element is produced. The first light-emitting layer uses a material that is an anthracene derivative as a host material, uses the orange-red fluorescent dopant whose emission color is A2 as a dopant, and performs co-evaporation so that the concentration ratio thereof is 20: 1. A film was formed. The second light-emitting layer uses a material that is an anthracene derivative as a host material, and the light-emitting material that is a light-emitting material having a different emission color as a dopant has the emission color of B2 and the emission color of A1 A film was formed by co-evaporation using an orange fluorescent dopant so that the concentration ratio thereof was 40: 3: 0.05. In Comparative Example 3, theoretically, by adjusting the film thickness of each light emitting layer and the dopant concentration of each dopant, line segments A1-A2, A2-B2, connecting A1, A2, and B2 on FIG. Although the emission color can be adjusted in the region consisting of B2-A1, it is actually difficult to make the doping concentration ratio of the orange fluorescent dopant in the second emission layer smaller than 0.05, Within the controllable range, orange light emission indicating A4 (chromaticity coordinates CIE (0.40, 0.38)) in FIG. 4 was obtained, and good pure white light emission could not be obtained. In addition, it is difficult to control the two dopants at different orders of magnitude, and the emission color changes greatly due to variations in the concentration ratio, making it difficult to adjust the emission color stably. In Comparative Example 3, for example, when the concentration ratio of each material in the second light emitting layer is 40: 3: 2, orange light emission indicating A5 (chromaticity coordinates CIE (0.55, 0.40)) may occur. confirmed.

  From the above test results, it is clear that the present invention has a sufficient effect.

  The present invention is particularly suitable for an organic EL element that requires fine adjustment of emission color.

1 Support substrate 2 First electrode (anode)
3 Insulating layer 5 Organic layer 5a Hole injection transport layer 5b First light emitting layer (organic light emitting layer)
5c Second light emitting layer (organic light emitting layer)
5d Electron transport layer 5e Electron injection layer 5f Host material 5g First dopant (light emitting material)
5h Second dopant (luminescent material)
5i Third dopant (luminescent material)
5j Fourth dopant (luminescent material)
6 Second electrode (cathode)

Claims (4)

An organic EL element formed by laminating at least two organic light emitting layers between an anode and a cathode,
At least one layer of the organic light emitting layer is doped with a light emitting material of two or more similar colors, and is an organic EL element. 2. The organic EL device according to claim 1, wherein the light emitting materials of similar colors have a difference in emission peak wavelength of 30 nm or less. 2. The organic EL device according to claim 1, wherein the concentration of each of the light-emitting materials having the same color is higher than the concentration of the light-emitting material having a short emission peak wavelength. . 2. The organic EL device according to claim 1, wherein each of the organic light emitting layers exhibits a different light emission color, and exhibits a white light emission color by mixing colors.

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