JP2005340187A - Light emitting device, its manufacturing method, and light emitting device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element and a light emitting device wherein a charge generating layer can be formed on an electroluminescent layer by using a spattering method, without giving a damage to the electroluminescent layer, as to the light emitting element wherein a plurality of the electroluminescent layers are laminated so as to sandwich the charge generating layer between a pair of electrodes facing each other. <P>SOLUTION: A material which is not easily etched is used for the layer among the electroluminescent layers, which is located closest to the charge generating layer formed on the electroluminescent layer by the spattering method. To be concrete, a benzooxazole derivative or a pyridine derivative is used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting element, a manufacturing method thereof, and a light emitting device using the light emitting element.

  A light-emitting element using a light-emitting material has features such as thin and light weight, high-speed response, and direct-current low-voltage driving, and is expected to be applied to a next-generation flat panel display. Further, it is said that a light-emitting device in which light-emitting elements are arranged in a matrix has an advantage in that it has a wide viewing angle and excellent visibility as compared with a conventional liquid crystal display device.

  The light-emitting mechanism of the light-emitting element is that a voltage is applied between a pair of electrodes with an electroluminescent layer sandwiched between them, so that electrons injected from the cathode and holes injected from the anode recombine at the emission center of the electroluminescent layer. It is said that a molecular exciton is formed, and when the molecular exciton returns to the ground state, energy is emitted and light is emitted. Singlet excitation and triplet excitation are known as excited states, and light emission is considered to be possible through either excited state.

  With respect to such a light emitting element, there are many problems depending on the material in improving the element characteristics, and improvement of the element structure, material development, and the like have been performed in order to overcome these problems.

  On the other hand, as one of the element structures, a plurality of light emitting units are divided and stacked by a charge generation layer between an opposing anode electrode and a cathode electrode in order to realize a long life at high luminance light emission. A light-emitting element having a structure has been reported (see Patent Document 1 and Non-Patent Document 1). This charge generation layer has a role of injecting carriers and needs to be a highly light-transmitting material.

JP 2003-45676 A

Toshio Matsumoto, Takeshi Nakada, Jun Endo, Koichi Mori, Norihumi Kawamura, Akira Tokoi, Junji Kido, IDW'03, 1285-1288

  In Patent Document 1 and Non-Patent Document 1, a transparent conductive film with high translucency is used as the charge generation layer, but a transparent conductive film typified by indium tin oxide (ITO) is formed by an electroluminescent layer by sputtering. If formed on the electroluminescent layer, the electroluminescent layer is damaged (sputter damage). Moreover, when forming a transparent conductive film using a vapor deposition method, the transmittance | permeability and resistivity of the electrode which are formed become low, and are not preferable. Therefore, a proposal of a light-emitting element and a light-emitting device that can form electrodes on an electroluminescent layer using a sputtering method without damaging the electroluminescent layer is desired.

  In view of the above-described problems, an object of the present invention is to provide a method for manufacturing a light-emitting element that can reduce damage to an electroluminescent layer due to film formation using a sputtering method. It is another object of the present invention to provide a light-emitting element and a light-emitting device in which damage due to film formation using a sputtering method is reduced.

  The light-emitting element of the present invention includes a plurality of electroluminescent layers and one or a plurality of charge generation layers between the first electrode and the second electrode. The electroluminescent layer and the charge generation layer are alternately stacked, and the electroluminescent layer includes a layer containing a material that is difficult to be etched by plasma during film formation by a sputtering method. The layer containing a material that is difficult to be etched is laminated so as to be formed before the charge generation layer.

  That is, among the electroluminescent layers, a material that is not easily etched by plasma at the time of film formation by the sputtering method is used for a layer in contact with the charge generation layer formed on the electroluminescent layer by the sputtering method. More specifically, when the first electrode is formed before the second electrode, a benzoxazole derivative or a pyridine derivative is included so as to be in contact with the charge generation layer on the first electrode side of the charge generation layer. A layer is formed.

  Hereinafter, in the present specification, of the pair of electrodes of the light-emitting element, the electrode formed first is referred to as a first electrode, and the electrode formed later is referred to as a second electrode.

  The structure of the benzoxazole derivative used in the present invention is shown in the general formula (1).

（式中、Ａｒはアリール基を示し、Ｒ１〜Ｒ４は、それぞれ独立に水素、ハロゲン、シアノ基、アルキル基（ただし、炭素数１〜１０）、ハロアルキル基（ただし、炭素数１〜１０）、アルコキシル基（ただし、炭素数１〜１０）を示す。もしくは、置換または無置換のアリール基、置換または無置換の複素環残基を示す。）。

(In the formula, Ar represents an aryl group, and R1 to R4 each independently represent hydrogen, halogen, cyano group, alkyl group (however, having 1 to 10 carbon atoms), haloalkyl group (however, having 1 to 10 carbon atoms), An alkoxyl group (wherein the carbon number is 1 to 10), or a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic residue);

  The structure of the pyridine derivative used in the present invention is shown in the general formula (2).

（式中、二つのＸは同じであっても異なる構造であってもよい。Ｒ１〜Ｒ８は、それぞれ独立に水素、ハロゲン、シアノ基、アルキル基（ただし、炭素数１〜１０）、ハロアルキル基（ただし、炭素数１〜１０）、アルコキシル基（ただし、炭素数１〜１０）、を示す。もしくは、置換または無置換のアリール基、置換または無置換の複素環残基を示す。）。

(In the formula, two Xs may be the same or different structures. R1 to R8 are each independently hydrogen, halogen, cyano group, alkyl group (however, having 1 to 10 carbon atoms), haloalkyl group. (However, C1-C10) and an alkoxyl group (C1-C10) are shown, or a substituted or unsubstituted aryl group and a substituted or unsubstituted heterocyclic residue are shown.

  In the light-emitting element of the present invention, a plurality of electroluminescent layers are partitioned by the charge generation layer and stacked between the first electrode, the second electrode, and the first electrode and the second electrode. In addition to a layer that has a structure and can actually emit light (light-emitting layer), a layer containing a material with a high carrier (electron / hole) transporting property or a layer containing a material with a high carrier-injecting property is combined. It may be configured.

For example, when the cathode is the first electrode and the anode is the second electrode, the above-described material that is not easily etched as a layer having a hole injecting property or a hole transporting property closest to the charge generation layer among the electroluminescent layers. Is used. Specifically, when a benzoxazole derivative is used, a benzoxazole derivative and tetracyanoquinodimethane (hereinafter referred to as TCQn), FeCl ₃ , fullerene (hereinafter referred to as C ₆₀ ), or tetrafluorotetracyanoquinodi. A layer containing any one or more materials of methane (hereinafter referred to as F ₄ TCNQ) is formed on the first electrode side of the charge generation layer so as to be in contact with the charge generation layer.

  Further, for example, when the anode is the first electrode and the cathode is the second electrode, the above-described material that is not easily etched as an electron-emitting layer or an electron-transporting layer closest to the charge generation layer among the electroluminescent layers. Is used. Specifically, when a benzoxazole derivative is used, a layer including the benzoxazole derivative and one or more materials of an alkali metal, an alkaline earth metal, or a transition metal is used as the first electrode of the charge generation layer. It is formed in contact with the charge generation layer on the side.

  With the above structure, a transparent conductive film formed by a sputtering method, for example, indium tin oxide (ITO) or indium tin oxide containing silicon, and an oxide containing 2 to 20% zinc oxide (ZnO) as a charge generation layer. Even when indium or the like is used, sputtering damage to the electroluminescent layer can be suppressed. Therefore, the selectivity of the substance for forming the charge generation layer is expanded.

  In the present invention, even when a transparent conductive film formed by a sputtering method is used for the second electrode, the layer in contact with the second electrode in the electroluminescent layer is etched into the plasma during the film formation by the sputtering method described above. By forming a layer including a material that is difficult to be formed, sputtering damage to the electroluminescent layer can be suppressed.

  Note that the light-emitting device of the present invention is not limited to the active matrix type, and may be a passive matrix type.

  As described above, the present invention provides a method for manufacturing a light-emitting element that can reduce damage to an electroluminescent layer when a charge generation layer or a second electrode is formed over the electroluminescent layer by a sputtering method. Can be obtained. Accordingly, it is possible to provide a light-emitting element and a light-emitting device in which defects due to film formation by sputtering are suppressed. Therefore, the selectivity of the material for the charge generation layer formed on the electroluminescent layer can be expanded.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below.

  The structure of the light emitting element of the present invention will be described with reference to FIG. In FIG. 1, the element structure of the light emitting element in this invention is typically shown. The light-emitting element 108 of the present invention is formed over a substrate 100 and has a structure in which a plurality of electroluminescent layers are stacked with a charge generation layer 103 interposed between a first electrode 101 and a second electrode 105. Actually, various layers or semiconductor elements are provided between the substrate 100 and the light emitting element 108.

  One of the first electrode 101 and the second electrode 105 corresponds to an anode and the other corresponds to a cathode. In the present invention, among the electroluminescent layers 102, the layer 106 closest to the charge generation layer formed on the electroluminescent layer 102 is etched by plasma during film formation by sputtering, such as a benzoxazole derivative or a pyridine derivative. Include materials that are difficult to handle. Specifically, when the first electrode 101 is an anode and the second electrode 105 is a cathode, a benzoxazole derivative is used in order to provide the layer 106 closest to the charge generation layer 103 with an electron injecting property. A benzoxazole derivative and one or more materials of an alkali metal, an alkaline earth metal, or a transition metal are included.

On the contrary, when the first electrode 101 is a cathode and the second electrode 105 is an anode, a benzoxazole derivative is used when a benzoxazole derivative is used in order to provide the layer 106 closest to the charge generation layer with hole injection properties. A derivative and one or more materials of TCQn, FeCl ₃ , C ₆₀ or F ₄ TCNQ are included.

  Similarly to the charge generation layer 103, when a sputtering method is used to form the second electrode 105, the electroluminescent layer can be obtained by using the above material for the layer 107 closest to the second electrode 105. The effect which suppresses the sputter | spatter damage to can be acquired. Specifically, the present invention is applied to a top emission type element in which the second electrode is formed of a transparent conductive film, and a dual emission type element in which the first electrode and the second electrode are formed of a transparent conductive film. By doing so, defects due to sputter damage can be suppressed.

  The electroluminescent layer 102 (104) includes at least a light emitting layer and a layer 107 (109) containing a material that is difficult to be etched by plasma at the time of film formation by a sputtering method. A layer, a hole blocking layer (hole blocking layer), an electron transport layer, an electron injection layer, and the like are appropriately combined. Note that the layer containing a material that is difficult to be etched may serve as these functions. Further, the electroluminescent layer 102 (104) may be a single layer or a structure in which a plurality of layers are stacked.

  As a first configuration of the present invention, a layer including a material that is difficult to be etched by plasma during film formation by sputtering includes a benzoxazole derivative represented by the following general formula (1) and is provided in contact with the charge generation layer.

（式中、Ａｒはアリール基を示し、Ｒ１〜Ｒ４は、それぞれ独立に水素、ハロゲン、シアノ基、アルキル基（ただし、炭素数１〜１０）、ハロアルキル基（ただし、炭素数１〜１０）、アルコキシル基（ただし、炭素数１〜１０）を示す。もしくは、置換または無置換のアリール基、置換または無置換の複素環残基を示す。）。

(In the formula, Ar represents an aryl group, and R1 to R4 each independently represent hydrogen, halogen, cyano group, alkyl group (however, having 1 to 10 carbon atoms), haloalkyl group (however, having 1 to 10 carbon atoms), An alkoxyl group (wherein the carbon number is 1 to 10), or a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic residue);

  Note that specific materials included in the benzoxazole derivative represented by the general formula (1) include substances represented by the structural formulas (3) to (5).

  As another structure of the present invention, a layer including a material that is difficult to be etched by plasma during film formation by sputtering includes a pyridine derivative represented by the following general formula (2) and is provided in contact with the charge generation layer.

（式中、二つのＸは同じであっても異なる構造であってもよい。Ｒ１〜Ｒ８は、それぞれ独立に水素、ハロゲン、シアノ基、アルキル基（ただし、炭素数１〜１０）、ハロアルキル基（ただし、炭素数１〜１０）、アルコキシル基（ただし、炭素数１〜１０）を示す。もしくは、置換または無置換のアリール基、置換または無置換の複素環残基を示す。）。

(In the formula, two Xs may be the same or different structures. R1 to R8 are each independently hydrogen, halogen, cyano group, alkyl group (however, having 1 to 10 carbon atoms), haloalkyl group. (However, C1-C10) and an alkoxyl group (C1-C10 are shown. Or a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic residue is shown.).

  Note that specific materials included in the pyridine derivative represented by the general formula (2) include substances represented by the structural formulas (6) to (9).

  In the light-emitting element of the present invention, light generated by carrier recombination in the electroluminescent layers 102 and 104 is emitted from both the first electrode 101 and the second electrode 105 to the outside. That is, both electrodes are formed of a transparent conductive film.

  Further, a known material can be used for the electroluminescent layers 102 and 104, and either a low molecular material or a high molecular material can be used. Note that the material for forming the electroluminescent layers 102 and 104 includes not only a material made of an organic compound material but also a structure containing an inorganic compound in part.

  In the present invention, specific materials used for the hole injection layer, the hole transport layer, the light emitting layer, or the electron transport layer constituting the electroluminescent layers 102 and 104 formed between the pair of electrodes are shown below.

As the hole-injecting material for forming the hole-injecting layer, a porphyrin-based compound is effective as long as it is an organic compound, and phthalocyanine (hereinafter referred to as H ₂ -Pc), copper phthalocyanine (hereinafter referred to as Cu-Pc). Or the like can be used. In addition, there is a material in which a conductive polymer compound is chemically doped, and polyethylenedioxythiophene (hereinafter referred to as PEDOT) doped with polystyrene sulfonic acid (hereinafter referred to as PSS) can also be used. Further, a benzoxazole derivative and any one or a plurality of materials of TCQn, FeCl ₃ , C ₆₀ or F ₄ TCNQ may be included.

  As the hole transporting material for forming the hole transporting layer, an aromatic amine-based compound (that is, a compound having a benzene ring-nitrogen bond or the like) is suitable. Examples of widely used materials include N, N′-bis (3-methylphenyl) -N, N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (hereinafter referred to as TPD). 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (hereinafter referred to as α-NPD) or 4,4′-4 ′, 4 ′ '-Tris (N-carbazolyl) -triphenylamine (hereinafter referred to as TCTA), 4,4', 4 ''-tris (N, N-diphenyl-amino) -triphenylamine (hereinafter referred to as TDATA) , 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (hereinafter referred to as MTDATA) and the like. .

Specific examples of the light-emitting material for forming the light-emitting layer include tris (8-quinolinolato) aluminum (hereinafter referred to as Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (hereinafter referred to as Almq _3). ), Bis (10-hydroxybenzo [h] -quinolinato) beryllium (hereinafter referred to as BeBq ₂ ), bis (2-methyl-8-quinolinolato)-(4-hydroxy-biphenylyl) -aluminum (hereinafter referred to as BAlq). ), Bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (hereinafter referred to as Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (hereinafter referred to as In addition to metal complexes such as Zn (BTZ) ₂ , various fluorescent dyes are effective.

When a light emitting layer is formed in combination with a guest material, quinacridone, diethylquinacridone (hereinafter referred to as DEQD), dimethylquinacridone (hereinafter referred to as DMQD), rubrene, perylene, coumarin, coumarin 545T (hereinafter referred to as C545T). DPT, Co-6, PMDFB, BTX, ABTX, DCM, DCJT, tris (2-phenylpyridine) iridium (hereinafter referred to as Ir (ppy) ₃ ), 2, 3, 7, 8, A triplet light-emitting material (phosphorescent material) such as 12,13,17,18-octaethyl-21H, 23H-porphyrin-platinum (hereinafter referred to as PtOEP) can be used as a guest material.

As the electron transporting material for forming the electron transport layer, the above-described metal complexes having a quinoline skeleton or a benzoquinoline skeleton such as Alq ₃ , Almq ₃ , and BeBq _2, and BAlq that is a mixed ligand complex are preferable. It is. There are also metal complexes having an oxazole-based ligand such as Zn (BOX) ₂ and a thiazole-based ligand such as Zn (BTZ) ₂ . In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (hereinafter referred to as PBD), 1,3-bis [ Oxadiazole derivatives such as 5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (hereinafter referred to as OXD-7), 3- (4-tert-butyl Phenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole (hereinafter referred to as TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl)- A triazole derivative such as 5- (4-biphenylyl) -1,2,4-triazole (hereinafter referred to as p-EtTAZ) can be used.

Specific examples of the electron injecting material for forming the electron injecting layer include alkali metal halides such as LiF and CsF, alkaline earth halides such as CaF ₂ , and alkali metal oxides such as Li ₂ O. Insulator thin films such as objects are often used. In addition, alkali metal complexes such as lithium acetylacetonate (abbreviation: Li (acac) and 8-quinolinolato-lithium (abbreviation: Liq) are also effective.
Moreover, you may make it contain a benzoxazole derivative and any one or more materials of an alkali metal, an alkaline-earth metal, or a transition metal.

  Although FIG. 1 shows a case where there are two electroluminescent layers, the present invention is not limited to this, and three or more layers may be used. Further, the electroluminescent layers to be stacked do not have to have the same configuration, and electroluminescent layers made of different materials may be stacked.

  In this embodiment, an example in which the first electrode is an anode and the second electrode is a cathode will be described with reference to FIG.

  First, the first electrode 201 of the light emitting element is formed over the substrate 200. Note that in this embodiment, the first electrode 201 functions as an anode. The material is ITO, which is a transparent conductive film, and is formed with a film thickness of 110 nm by a sputtering method.

  Next, the electroluminescent layer 202 is formed over the first electrode 201 functioning as an anode. Note that the electroluminescent layer 202 in this embodiment has a stacked structure including a hole injection layer 211, a hole transport layer 212, a light emitting layer 213, an electron transport layer 214, and an electron injection layer 215.

  The substrate on which the first electrode 201 is formed is fixed to a substrate holder of a commercially available vacuum deposition apparatus with the surface on which the first electrode 201 is formed facing downward, and copper is attached to an evaporation source provided inside the vacuum deposition apparatus. Phthalocyanine (hereinafter referred to as Cu—Pc) is added, and the hole injection layer 211 is formed with a thickness of 20 nm by a vapor deposition method using a resistance heating method. Note that a known hole injecting material can be used as a material for forming the hole injecting layer 211.

  Next, the hole transport layer 212 is formed using a material having excellent hole transport properties. As a material for forming the hole transport layer 212, a known hole transport material can be used. In this embodiment, 4,4′-bis [N- (1-naphthyl) -N-phenyl- Amino] -biphenyl (hereinafter referred to as α-NPD) is formed to a thickness of 40 nm by the same method.

Next, the light emitting layer 213 is formed. Note that holes and electrons recombine in the light-emitting layer 213 to emit light. In this example, tris (8-quinolinolato) aluminum (hereinafter referred to as Alq ₃ ) serving as a host material among materials forming the light emitting layer 213 and dimethylquinacridone (hereinafter referred to as DMQD) serving as a guest material are used. The film is formed with a film thickness of 40 nm by co-evaporation so that DMQD is 1% by mass.

Next, the electron transport layer 214 is formed. As a material for forming the electron transport layer 214, a known electron transport material can be used. In this embodiment, Alq ₃ is used and a film thickness of 20 nm is formed by a vapor deposition method.

  Next, the electron injection layer 215 is formed. The electron injection layer 215 is formed using a benzoxazole derivative represented by the general formula (1). This facilitates the injection of electrons from the charge generation layer or electrode into the electroluminescent layer and prevents damage to the electroluminescent layer due to the formation of the charge generation layer or electrode. Specifically, a layer containing any one of an alkali metal, an alkaline earth metal, and a transition metal is formed using the benzoxazole derivative represented by the general formula (1) in order to improve electron injectability. In this example, 4,4′-Bis (5-methyl benzazol-2-yl) stilbene represented by the following structural formula (3) and Li which is an alkali metal are used, and Li becomes 1% by mass. Thus, it forms by a co-evaporation method with the film thickness of 20 nm.

  In this manner, the hole injection layer 211, the hole transport layer 212, the light-emitting layer 213, the electron transport layer 214, and the electron injection layer (a layer containing a material that is difficult to be etched by plasma during film formation by sputtering) 215 After the electroluminescent layer 202 formed by stacking is formed, the charge generation layer 203 is formed by a sputtering method. Note that the charge generation layer 203 is preferably a light-transmitting substance. In this embodiment, the charge generation layer 203 is obtained by forming ITO (10 nm) on the electroluminescent layer 202 by a sputtering method.

An electroluminescent layer 204 is formed on the charge generation layer 203. The electroluminescent layer 204 may be formed in the same manner as the electroluminescent layer 202 described above. In this example, Cu—Pc (20 nm) as the hole injection layer 216, α-NPD (40 nm) as the hole transport layer 217, Alq ₃ (40 nm) containing 1% by mass of DMQD as the light emitting layer 218, an electron transport layer A benzoxazole derivative (20 nm) containing 1% by mass of Li is formed as Alq ₃ (20 nm) as 219 and an electron injection layer (a layer containing a material that is difficult to be etched by plasma during film formation by a sputtering method) 220.

  Then, after the electroluminescent layer 204 is formed, ITO is formed with a thickness of 110 nm as a second electrode 205 functioning as a cathode by a sputtering method.

  The light-emitting element manufactured in this example is a film formed by a sputtering method by forming a layer containing a material that is difficult to be etched by plasma at the time of film formation by a sputtering method in a layer closest to the charge generation layer among the electroluminescent layers. Damage to the electroluminescent layer when formed can be reduced. Similar effects can be obtained when a pyridine derivative is used in addition to the benzoxazole derivative.

  In order to confirm whether or not damage to the electroluminescent layer can be reduced by forming a layer containing a material that is difficult to be etched in the layer closest to the transparent conductive film formed by the sputtering method among the electroluminescent layers, The experiment was conducted.

On the first electrode, ITO, Alq ₃ (40 nm) containing Cu-Pc (20 nm) as a hole injection layer, α-NPD (40 nm) as a hole transport layer, 1% by mass of DMQD as a light emitting layer, electron transport Alq ₃ (20 nm) was formed as a layer. Then, Li that is an alkali metal and 4,4′-Bis (5-methylbenzoxol-2-yl) stilbene (20 nm) represented by the above structural formula (3) are used so that Li becomes 1% by mass. An electron injection layer was formed, and then ITO (110 nm) was formed by sputtering. The element manufactured in this experiment is referred to as element 1.
[Comparative Example 1]

  As Comparative Example 1, an element that does not use a material that is not easily etched by plasma at the time of film formation by a sputtering method is manufactured as a layer closest to a transparent conductive film formed by a sputtering method among electroluminescent layers.

4,4′-Bis (5-methylbenzoxol-2-yl) stilbene (20 nm) represented by the above structural formula (3) containing 1% by mass of Li as an electron injection layer on the first electrode ITO. Alq ₃ (20 nm) as an electron transporting layer, forming a Alq ₃ containing DMQD 1 mass% as a light-emitting layer (40 nm), a hole transport layer α-NPD (40nm), Cu -Pc as a hole injection layer (20 nm) did. Thereafter, ITO (110 nm) was formed by sputtering. The element formed in this comparative example is referred to as element 2.
[Comparative Example 2]

    As Comparative Example 2, an element that does not use a material that is not easily etched by plasma at the time of film formation by a sputtering method was manufactured as the layer closest to the transparent conductive film formed by the sputtering method among the electroluminescent layers. The device fabricated in this comparative example was formed up to α-NPD in the same manner as the device fabricated in comparative example 1, and then the film thickness of Cu-Pc formed as the hole injection layer was set to 40 nm. (110 nm) was formed. The element formed in this comparative example is referred to as element 3.

    FIG. 6 shows the luminance-current density characteristics of the element 1, element 2 and element 3, FIG. 7 shows the current efficiency-luminance characteristics, FIG. 8 shows the luminance-voltage characteristics, and FIG. 9 shows the current-voltage characteristics. As can be seen from FIGS. 6 to 9, the element 1 has better element characteristics than the elements 2 and 3.

  The structure of the element 1 is included in the structure of the light-emitting element prepared in Example 1. Even in the light-emitting element manufactured in Example 1, an electric field can be obtained by using a material that is not easily etched by plasma during film formation by sputtering. It was confirmed that the sputter damage to the light emitting layer was prevented.

  In this embodiment, an example in which the first electrode is a cathode and the second electrode is an anode will be described with reference to FIG.

  First, the first electrode 301 of the light emitting element is formed over the substrate 300. Note that in this embodiment, the first electrode 301 functions as a cathode. The material is ITO, which is a transparent conductive film, and is formed with a film thickness of 110 nm by a sputtering method.

  Next, an electroluminescent layer 302 is formed over the first electrode 301 functioning as a cathode. Note that the electroluminescent layer 302 in this embodiment has a stacked structure including an electron injection layer 311, an electron transport layer 312, a light emitting layer 313, a hole transport layer 314, and a hole injection layer 315.

  An electron injection layer 311 is formed over the first electrode 301 with a material having excellent electron injection properties. As a material for forming the electron injecting layer, a known electron injecting material can be used. In this embodiment, a benzoxazole derivative and an alkali metal Li are used so that Li is 1% by mass. Then, it is formed by a co-evaporation method with a film thickness of 20 nm.

Next, the electron transport layer 312 is formed. As a material for forming the electron transporting layer 312, a known electron transporting material can be used. In this embodiment, Alq ₃ is used and a film thickness of 20 nm is formed by a vapor deposition method.

Next, the light emitting layer 313 is formed. Note that holes and electrons recombine in the light-emitting layer 313 to emit light. In this example, Alq _{3 serving as a} host material and DMQD serving as a guest material among the materials forming the light emitting layer 313 and DMQD serving as a guest material are used, and the film thickness is 40 nm by co-evaporation so that DMQD is 10% by mass. Form.

  Next, the hole transport layer 314 is formed using a material having excellent hole transport properties. As a material for forming the hole transport layer 314, a known hole transport material can be used. In this embodiment, α-NPD is formed to a thickness of 40 nm by a vapor deposition method.

Next, the hole injection layer 315 is formed. The hole injection layer 315 is formed using a benzoxazole derivative occupied by the general formula (1). This facilitates the injection of holes from the charge generation layer or electrode into the electroluminescent layer, and prevents damage to the electroluminescent layer due to the formation of the charge generation layer or electrode. Specifically, a layer containing one or more materials of TCQn, FeCl ₃ , C _60, or F ₄ TCNQ using a benzoxazole derivative represented by the general formula (1) in order to enhance hole injection properties. Form. In this example, a layer containing 4,4′-Bis (5-methylbenzoxol-2-yl) stilbene and TCQn represented by the following structural formula (3) is formed by a co-evaporation method with a thickness of 20 nm. To do.

  Thus, after forming the electroluminescent layer 302 formed by stacking the electron injection layer 311, the electron transport layer 312, the light emitting layer 313, the hole transport layer 314, and the hole injection layer 315, the charge generation layer is formed. 303 is formed by a sputtering method. Note that the charge generation layer 303 is preferably a light-transmitting substance. In this embodiment, the charge generation layer 303 is obtained by forming ITO (10 nm) on the electroluminescent layer 302 by a sputtering method.

An electroluminescent layer 304 is formed on the charge generation layer 303. The electroluminescent layer 304 may be formed in the same manner as the electroluminescent layer 302 described above. In this example, a benzoxazole derivative (20 nm) containing 1% by mass of Li as the electron injection layer 316, Alq ₃ (20 nm) as the electron transport layer 317, Alq ₃ (40 nm) containing 1% by mass of DMQD as the light emitting layer 318, Α-NPD (40 nm) is formed as the hole transport layer 319, and a layer containing a benzoxazole derivative and TCQn is formed as the hole injection layer 320 with a thickness of 20 nm.

  Then, after the electroluminescent layer 304 is formed, ITO is formed to a thickness of 110 nm by a sputtering method as the second electrode 305 that functions as an anode.

  The light-emitting element manufactured in this example is a film formed by a sputtering method by forming a layer containing a material that is difficult to be etched by plasma at the time of film formation by a sputtering method in a layer closest to the charge generation layer among the electroluminescent layers. Damage to the electroluminescent layer when formed can be reduced. Similar effects can be obtained when a pyridine derivative is used in addition to the benzoxazole derivative.

  In this example, a structure of a light-emitting device using the light-emitting element manufactured in Example 1 and Example 2 will be described with reference to FIGS. 4 and 11 to 14.

  In a light-emitting device using a light-emitting element in which a plurality of electroluminescent layers are stacked, for example, when white light emission is obtained, conventionally, in all the light-emitting elements, the first color electroluminescent layer (for example, electroluminescent layer emitting red light), the first A two-color electroluminescent layer (for example, an electroluminescent layer emitting green light) and a third color electroluminescent layer (for example, an electroluminescent layer emitting blue light) were laminated in the same order. However, if all the light-emitting elements have the same laminated structure, all the light-emitting elements must emit white light, and they are colored due to light interference effects and differences in resistance values of the layers. It was difficult to adjust so that no white light emission was obtained. That is, in order to obtain a desired emission color, it is necessary to strictly adjust the film thickness of each layer. In addition, since the time-dependent change in characteristics varies depending on each light emitting material, the light is not white over time, and light emission of a specific color may be noticeable. When all the light-emitting elements have the same laminated structure, it was impossible to cope with a change in emission color due to a change in characteristics over time.

  Therefore, in this embodiment, white light emission is obtained by making the laminated structure of each light emitting element as shown in FIG. In FIG. 4, three light emitting elements (501, 502, 503) are formed on a substrate. One pixel is formed by three light emitting elements. In each light-emitting element, an electroluminescent layer is stacked on a first electrode 551 with a charge generation layer 552 interposed therebetween, and a second electrode 553 is formed as the uppermost layer.

  In the light emitting element 501, a first color electroluminescent layer 511, a second color electroluminescent layer 512, and a third color electroluminescent layer 513 are stacked in this order. In the light emitting element 502, the second color electroluminescent layer 521, The electroluminescent layer 522 of the third color and the electroluminescent layer 523 of the first color are stacked in this order. In the light emitting element 503, the electroluminescent layer 531 of the third color, the electroluminescent layer 532 of the first color, and the electric field of the second color are stacked. The light emitting layer 533 is stacked in this order. Thus, by changing the stacking order of the electroluminescent layers of each light emitting element, it is possible to obtain white light emission as a whole pixel even if each light emitting element cannot obtain white light emission. Note that the light-emitting element 501 emits light with a strong first emission color, the light-emitting element 502 emits light with a strong second emission color, and the light-emitting element 503 emits light with a strong third emission color.

  In the case of the active matrix type, since each light emitting element can be driven independently, it is possible to cope with a change in characteristics of each light emitting material with time, and to obtain white light emission for a longer time. .

  For example, when the first emission color becomes conspicuous due to changes over time, the first controller 561 emits the first emission color strongly as shown in FIG. The current flowing through the element is reduced, the current flowing through the second light emitting element in which the second emission color is strongly emitted by the second controller 562 is increased, and the third emission color is obtained by the third controller 563. Increases the current flowing through the third light emitting element which emits light strongly, and keeps white light emission as a whole. In this way, the controller can control the emission color of the entire pixel by changing the amount of current flowing through each light emitting element.

  4 and 11 show the case where the second electrode is an anode, the second electrode may be a cathode. In this embodiment, the case of white light emission is shown, but the present invention can also be applied to obtain light emission of a desired color. Further, although an example in which three electroluminescent layers are laminated is shown in this embodiment, the present invention is not limited to this, and the same effect can be obtained as long as two or more layers are formed. Specifically, as in this embodiment, one pixel may be formed by three light emitting elements in which three electroluminescent layers are stacked, or two light emitting elements in which two electroluminescent layers are stacked. Pixels may be formed. One pixel may be formed of a light emitting element in which three or more electroluminescent layers are stacked. One pixel may be formed by two light emitting elements in which three electroluminescent layers are stacked, or one pixel may be formed by four light emitting elements in which three electroluminescent layers are stacked.

Further, the thickness of the electroluminescent layer may be different for each light emitting element. For example, in this embodiment, the first color electroluminescent layers 511, 523, and 532 may have different thicknesses. Thereby, since the characteristics of the light emission color are different for each light emitting element, the light emission color can be made closer to the desired light emission color.

  Note that in order to change the amount of current applied to each light-emitting element in the same pixel, a method of changing the potential of the power supply line or a method of changing the signal from the source line driver circuit by making the potential of the power supply line the same is used. is there.

  FIG. 12 shows an equivalent circuit of a light-emitting device in which a power supply line electrically connected to each light-emitting element in the same pixel is independent and a potential applied to each light-emitting element can be changed.

  In FIG. 12, each pixel 1101 is provided with three light emitting elements, and power supply lines for transmitting a potential supplied to the light emitting elements are independently provided with the three elements. Accordingly, independent potentials can be supplied to the light emitting elements from the power supply circuit 1106, and the luminance of the three light emitting elements can be controlled independently.

  Each pixel is connected to the source line driver circuit 1104 and the gate line driver circuit 1105, and is controlled by signals supplied from the source line driver circuit 1104 and the gate line driver circuit 1105.

  The change in light emission color due to the time-dependent change of each light-emitting element is calculated using a light-emitting element for monitoring, or using the result of the lighting time of the light-emitting element and the degradation characteristics of the light-emitting element measured in advance. The degree of change with time calculated by the monitor circuit 1108 is input to the power supply circuit 1106, and the potential supplied to each light emitting element is determined.

  The controller 1107 controls the source line driver circuit 1104, the gate line driver circuit 1105, and the power supply circuit 1106. Note that a plurality of potentials may be supplied only by the power supply circuit 1106, and the controller 1107 may control the source line driver circuit 1104 and the gate line driver circuit 1105.

  As described above, the luminance of the three light emitting elements in one pixel can be controlled independently. In FIG. 12, a red color filter can be provided for the pixel 1101R, a green color filter can be provided for the pixel 1101G, and a blue color filter can be provided for the pixel 1101B. is there. The light emitting device of the present invention can suppress a change in color due to a change with time, and has high luminance and a long lifetime, so even when used as a display, it can suppress a change in color due to a change with time. A display with high brightness and long life can be obtained.

  FIG. 13 is an equivalent circuit of a light-emitting device in the case where the video signal supplied from the source line driver circuit 1204 to the pixels is changed with the same potential of the power supply line.

  In FIG. 13, each pixel 1201 is provided with three light emitting elements, and a power supply line for transmitting a potential supplied to the light emitting elements is common to the three elements. Therefore, the potential supplied from the power supply circuit 1206 to each light-emitting element is the same potential.

    In FIG. 13, each pixel is connected to a source line driver circuit 1204 and a gate line driver circuit 1205, and is controlled by signals supplied from the source line driver circuit 1204 and the gate line driver circuit 1205.

    In addition, the luminance of each light-emitting element is controlled by a video signal supplied from the source line driver circuit 1204. By changing the video signal, the voltage applied to the gate of the second TFT 1212 when the first TFT 1211 is turned on by a signal from the gate line driver circuit 1205 is changed and is supplied from the power supply line to the light emitting element. The amount of current that changes.

  The change in light emission color due to the time-dependent change of each light-emitting element is calculated using a light-emitting element for monitoring, or using the result of the lighting time of the light-emitting element and the degradation characteristics of the light-emitting element measured in advance. The degree of change with time calculated by the monitor circuit 1208 is input to the power supply circuit 1206, and the potential supplied to each light emitting element is determined.

  The controller 1207 controls the source line driver circuit 1204, the gate line driver circuit 1205, and the power supply circuit 1206. Note that a plurality of potentials may be supplied only by the power supply circuit 1206, and the controller 1207 may control the source line driver circuit 1204 and the gate line driver circuit 1205.

  As described above, the luminance of the three light emitting elements in one pixel can be controlled independently. In FIG. 13, a red color filter is provided for the pixel 1201R, a green color filter is provided for the pixel 1201G, and a blue color filter is provided for the pixel 1201B. is there. The light emitting device of the present invention can suppress a change in color due to a change with time, and has high luminance and a long lifetime, so even when used as a display, it can suppress a change in color due to a change with time. A display with high brightness and long life can be obtained.

  The present invention can be applied not only to an active matrix light-emitting device but also to a passive matrix light-emitting device. FIG. 14 shows an equivalent circuit in the case where the present invention is applied to a passive matrix light-emitting device.

  In FIG. 14, a pixel 1301 has three light emitting elements. Each light emitting element is controlled based on signals input from the source line driver circuit 1304 and the gate line driver circuit 1305. The luminance of each light emitting element is determined by the value of current supplied from the source line driver circuit 1304. The value of the current supplied from the source line driver circuit 1304 is controlled by the power supply circuit 1306 and the controller 1307. The power supply circuit 1306 determines the amount of current applied to the light emitting element based on the degree of change over time of the light emitting element calculated by the monitor circuit 1308.

  As described above, the luminance of the three light emitting elements in one pixel can be controlled independently. In FIG. 14, a red color filter is provided for the pixel 1301R, a green color filter is provided for the pixel 1301G, and a blue color filter is provided for the pixel 1301B. is there. The light emitting device of the present invention can suppress a change in color due to a change with time, and has high luminance and a long lifetime, so even when used as a display, it can suppress a change in color due to a change with time. A display with high brightness and long life can be obtained.

  In this embodiment, a light-emitting device having the light-emitting element of the present invention in a pixel portion will be described with reference to FIG. 5A is a top view illustrating the light-emitting device, and FIG. 5B is a cross-sectional view taken along line A-A ′ in FIG. 5A. Reference numeral 801 indicated by a dotted line denotes a drive circuit portion (source side drive circuit), 802 denotes a pixel portion, and 803 denotes a drive circuit portion (gate side drive circuit). Further, reference numeral 804 denotes a sealing substrate, and 805 denotes a sealing material. An inner side surrounded by the sealing material 805 is a space 807.

  Reference numeral 808 denotes a wiring for transmitting signals input to the source side driver circuit 801 and the gate side driver circuit 803, and a video signal, a clock signal, and a start signal from an FPC (flexible printed circuit) 809 serving as an external input terminal. Receive a reset signal, etc. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes not only a light-emitting device body but also a state in which an FPC or a PWB is attached thereto.

  Next, a cross-sectional structure is described with reference to FIG. A driver circuit portion and a pixel portion are formed over the element substrate 810. Here, a source side driver circuit 801 which is a driver circuit portion and a pixel portion 802 are shown.

  Note that the source side driver circuit 801 is a CMOS circuit in which an n-channel TFT 823 and a p-channel TFT 824 are combined. The TFT forming the driving circuit may be formed by a known CMOS circuit, PMOS circuit or NMOS circuit. In this embodiment mode, a driver integrated type in which a driver circuit is formed over a substrate is shown; however, this is not always necessary, and the driver circuit can be formed outside the substrate.

  The pixel portion 802 is formed of a plurality of pixels including a switching TFT 811, a current control TFT 812, and a first electrode 813 electrically connected to the drain thereof. Note that an insulating layer 814 is formed to cover an end portion of the first electrode 813. Here, a positive photosensitive acrylic resin film is used.

  In order to improve the coverage, a curved surface having a curvature is formed at the upper end portion or the lower end portion of the insulating layer 814. For example, in the case where positive photosensitive acrylic is used as a material for the insulating layer 814, it is preferable that only the upper end portion of the insulating layer 814 has a curved surface with a curvature radius (0.2 μm to 3 μm). As the insulating layer 814, either a negative type that becomes insoluble in an etchant by light irradiation or a positive type that becomes soluble in an etchant by light irradiation can be used.

  A first electroluminescent layer 815, a charge generation layer 816, a second electroluminescent layer 817, and a second electrode 818 are formed over the first electrode 813, respectively. The first electroluminescent layer 815 and the second electroluminescent layer 817 are formed by an evaporation method using an evaporation mask or an inkjet method. The charge generation layer 816 is formed by a sputtering method. The second electrode 818 is formed using a transparent conductive film. The structure of the light-emitting element 819 may be the structure of the electroluminescent layer described in Example 1 or Example 2, for example.

  Further, the sealing substrate 804 is bonded to the element substrate 810 with the sealant 805, whereby the light-emitting element 819 is provided in a space surrounded by the element substrate 810, the sealing substrate 804, and the sealant 805. . Note that the space 807 is filled with a filler and may be filled with a sealing material in addition to the case of being filled with an inert gas (such as nitrogen or argon).

  Note that an epoxy-based resin is preferably used for the sealant 805. Moreover, it is desirable that these materials are materials that do not transmit moisture and oxygen as much as possible. In addition to a glass substrate and a quartz substrate, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), Mylar, polyester, acrylic, or the like can be used as a material used for the sealing substrate 804.

  As described above, a light-emitting device having the light-emitting element of the present invention can be obtained. In this embodiment, two electroluminescent layers are stacked, but three or more layers may be stacked.

  In this example, various electric appliances including a light-emitting device manufactured using the light-emitting element of the present invention as a part thereof will be described.

  Video appliances, digital cameras, goggle-type displays, navigation systems, sound playback devices (car audio, audio components, etc.), personal computers, game machines as electrical appliances manufactured using light-emitting devices formed using the present invention , A portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), an image reproducing device (specifically, a digital versatile disc (DVD)) provided with a recording medium, and the image And the like). Specific examples of these electric appliances are shown in FIG.

  FIG. 10A illustrates a display device, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. It is manufactured by using a light emitting device formed using the present invention for the display portion 2003. The display device includes all information display devices such as a computer, a TV broadcast receiver, and an advertisement display.

  FIG. 10B illustrates a personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. It is manufactured by using a light emitting device formed using the present invention for the display portion 2203.

  FIG. 10C illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The display device 2302 is manufactured using a light-emitting device formed using the present invention.

  FIG. 10D illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the light-emitting device formed using the present invention is used for the display portion A 2403 and the display portion B 2404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.

  FIG. 10E illustrates a goggle type display, which includes a main body 2501, a display portion 2502, and an arm portion 2503. The display device 2502 is manufactured using a light-emitting device formed using the present invention.

  FIG. 10F illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and an eyepiece. Part 2610 and the like. The display device 2602 is manufactured using a light-emitting device formed using the present invention.

  Here, FIG. 10G shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. It is manufactured by using a light emitting device formed using the present invention for the display portion 2703.

  By using the light-emitting element of the present invention, it is possible to provide a light-emitting element and a light-emitting device that achieve a long life at the time of high-luminance light emission and have few defects due to sputtering damage.

4A and 4B illustrate a light-emitting element of the present invention. FIG. 6 illustrates a light-emitting element of the present invention. FIG. 6 illustrates a light-emitting element of the present invention. 4A and 4B illustrate a light-emitting device of the present invention. FIG. 14 illustrates an example of a light-emitting device using a light-emitting element of the present invention. The figure which showed the luminance-current density characteristic. The figure which showed the current efficiency-luminance characteristic. The figure which showed the luminance-voltage characteristic. The figure which showed the current-voltage characteristic. The figure which shows the example of the electric appliance using the light-emitting device of this invention. 4A and 4B illustrate a light-emitting device of the present invention. 4A and 4B illustrate a light-emitting device of the present invention. 4A and 4B illustrate a light-emitting device of the present invention. 4A and 4B illustrate a light-emitting device of the present invention.

Explanation of symbols

100 Substrate 101 First electrode 102 Electroluminescent layer 103 Charge generation layer 105 Second electrode 106 Layer 107 closest to the charge generation layer 107 Layer 108 closest to the second electrode

Claims (18)

A plurality of electroluminescent layers and one or a plurality of charge generation layers between the first electrode and the second electrode;
One or more charge generation layers are formed between the plurality of electroluminescent layers,
The electroluminescent layer has a layer containing a benzoxazole derivative,
The layer including the benzoxazole derivative is in contact with the charge generation layer, and is formed on the first electrode side of the charge generation layer. A plurality of electroluminescent layers and one or a plurality of charge generation layers between the first electrode and the second electrode;
One or more charge generation layers are formed between the plurality of electroluminescent layers,
The electroluminescent layer has a layer containing a pyridine derivative,
The layer containing the pyridine derivative is in contact with the charge generation layer and is formed on the first electrode side of the charge generation layer. 3. The light emitting element according to claim 1, wherein the charge generation layer is formed by a sputtering method. 4. The light-emitting element according to claim 1, wherein the second electrode is formed by a sputtering method. 5. The light-emitting element according to claim 1, wherein the charge generation layer is a transparent conductive film. 6. The light-emitting element according to claim 1, wherein the second electrode is a transparent conductive film. 7. The light-emitting element according to claim 1, wherein the first electrode is a transparent conductive film. Forming a first electrode;
Forming a plurality of electroluminescent layers and one or more charge generation layers on the first electrode;
Forming a second electrode above the first electrode,
Forming a layer containing a benzoxazole derivative on the uppermost layer of the electroluminescent layer;
A method for manufacturing a light-emitting element, wherein the charge generation layer is formed in contact with a layer containing the benzoxazole derivative. Forming a first electrode;
Forming a plurality of electroluminescent layers and one or more charge generation layers on the first electrode;
Forming a second electrode above the first electrode,
Forming a layer containing a pyridine derivative on the uppermost layer of the electroluminescent layer;
A method for manufacturing a light-emitting element, wherein the charge generation layer is formed in contact with a layer containing the pyridine derivative. 10. The method for manufacturing a light-emitting element according to claim 8, wherein the charge generation layer is formed by a sputtering method. The method for manufacturing a light-emitting element according to claim 8, wherein the second electrode is formed by a sputtering method. The method for manufacturing a light-emitting element according to claim 8, wherein the charge generation layer is a transparent conductive film. The method for manufacturing a light-emitting element according to claim 8, wherein the second electrode is a transparent conductive film. 14. The method for manufacturing a light-emitting element according to claim 8, wherein the first electrode is a transparent conductive film. A light-emitting device using the light-emitting element according to claim 1. Having a plurality of light emitting elements in one pixel,
In the light emitting element, a plurality of types of electroluminescent layers are stacked with one or more charge generation layers interposed between a pair of electrodes,
The electroluminescent layer has a layer containing a benzoxazole derivative,
The layer containing the benzoxazole derivative is in contact with the charge generation layer and formed on the first electrode side of the charge generation layer;
2. The light emitting device according to claim 1, wherein the order of stacking the plurality of types of electroluminescent layers is different for each light emitting element in one pixel. Having a plurality of light emitting elements in one pixel,
In the light emitting element, a plurality of types of electroluminescent layers are stacked with one or more charge generation layers interposed between a pair of electrodes,
The electroluminescent layer has a layer containing a pyridine derivative,
The layer containing the pyridine derivative is in contact with the charge generation layer and formed on the first electrode side of the charge generation layer;
2. The light emitting device according to claim 1, wherein the order of stacking the plurality of types of electroluminescent layers is different for each light emitting element in one pixel. 18. The light emitting device according to claim 16, wherein the light emitting device includes a control unit capable of independently controlling an amount of current flowing through the plurality of light emitting elements.

Images