JP2005209583A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device reduced in variation of an emission spectrum depending on an angle for viewing an emission extraction surface. <P>SOLUTION: This light emitting device has a first insulation layer formed on a substrate; an opening part reaching the substrate is formed in the first insulation layer; a second insulation layer is formed by covering the opening part; and a light emitting element is formed on the second insulation layer by overlapping at least a part of the opening part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an active matrix light-emitting device, and more particularly to a structure of a portion from which light emission is extracted.

  A light-emitting device using light emission from an electroluminescence element (light-emitting element) is a device that has attracted attention as a display device with a high viewing angle and low power consumption.

  There are an active matrix type and a passive matrix type as a driving method of a light-emitting device mainly used for display. An active matrix light-emitting device with a driving method can control light emission and non-light emission for each light-emitting element. Therefore, it can be driven with lower power consumption than a passive matrix light-emitting device, and is suitable not only as a display portion of a small electrical appliance such as a mobile phone but also as a display portion of a large-sized television receiver or the like. .

  In the active matrix light-emitting device, a circuit for controlling driving of each light-emitting element is provided for each light-emitting element. The circuit and the light-emitting element are arranged on the substrate so that extraction of emitted light to the outside is not hindered by the circuit. In addition, a light-transmitting insulating layer is stacked in a portion overlapping with the light-emitting element, and light emission is emitted outside through the insulating layer. These insulating layers are provided to form circuit elements such as transistors and capacitors, which are components of the circuit, or wiring.

  By the way, when light emission passes through the laminated insulating films, the light emission may cause multiple interference due to the difference in the refractive index of each insulating layer. As a result, the emission spectrum changes depending on the angle at which the light emission surface is viewed, and the visibility of the image displayed on the light emitting device is deteriorated.

  In addition, a reduction in image visibility caused by a difference in refractive index between layers also occurs in a passive matrix light-emitting device. For example, Patent Document 1 raises a problem that external light and light emission are reflected at an interface due to a difference in refractive index of each layer constituting a light emitting element, and visibility is deteriorated, so that the element structure can be solved. We have proposed light-emitting elements that have been devised.

JP-A-7-21458

  An object of the present invention is to provide a light emitting device in which a change in emission spectrum depending on an angle at which a light emission extraction surface is viewed is reduced.

  One of the configurations of the present invention for solving the above-described problem is that the first insulating layer is formed on the substrate, and the first insulating layer has an opening reaching the substrate. A second insulating layer is formed so as to cover the opening, and a light emitting element is provided on the second insulating layer so as to overlap at least part of the opening.

  According to another aspect of the present invention, there is provided a substrate, a first insulating layer formed on the substrate, a semiconductor layer formed on the insulating layer, and a gate insulating layer formed so as to cover the semiconductor layer. And a gate insulating layer formed on the semiconductor layer and the gate insulating layer, and the gate insulating layer has an opening that penetrates the first insulating layer and reaches the substrate. A second insulating layer is formed to cover the gate insulating layer, the gate electrode, and the opening, and a light emitting element is formed on the second insulating layer so as to overlap at least part of the light emitting opening. It is characterized by being provided.

  Another structure of the present invention is characterized in that in the above structure, the first insulating layer and the second insulating layer have a single layer structure.

  Another structure of the present invention is characterized in that in the above structure, the first insulating layer and / or the second insulating layer has a multilayer structure.

  According to another configuration of the present invention, in the above configuration, the light-emitting element includes a first electrode, a light-emitting layer, and a second electrode, and the first electrode is formed on the substrate from the second electrode. The second insulating layer has a refractive index between the refractive index of the first electrode and the refractive index of the substrate.

  According to another configuration of the present invention, in the above configuration, the light-emitting element includes a first electrode, a light-emitting layer, and a second electrode, and the first electrode is formed on the substrate from the second electrode. The refractive index of each layer formed between the first electrode and the substrate in the opening is smaller as it is closer to the substrate side.

  According to the present invention, it is possible to obtain a light emitting device in which a change in emission spectrum depending on an angle at which the light emission extraction surface is viewed is reduced.

  In addition, a change in the emission spectrum depending on the viewing angle of the emission extraction surface is reduced, whereby a display device that can provide an image with excellent visibility can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and it is easy for those skilled in the art to make various changes in form and details without departing from the spirit and scope of the present invention. Understood. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
The light emitting device of the present invention will be described with reference to FIG. An insulating layer 12 a and an insulating layer 12 b are provided on the substrate 11. A transistor 17 including a semiconductor layer 14, a gate insulating film 15, and a gate electrode 16 is provided over the insulating layer 12b. The transistor 17 is covered with an insulating layer 21.

  Here, the substrate 11 is made of a transparent material such as glass or quartz. Further, a substrate having a temporary property such as plastic may be used as the substrate 11. In addition, any substrate can be used as the substrate 11 as long as it has translucency and functions as a support for supporting the transistor 17 and the light emitting element 24.

  In this embodiment, the insulating layers 12a and 12b are provided to prevent impurities diffused from the substrate 11 from entering the transistor 17, and are made of different materials. Note that the insulating layers 12a and 12b are preferably layers made of silicon oxide, silicon nitride, silicon nitride containing oxygen, or the like. However, it may be a layer made of other materials. In this embodiment, the insulating layer 12 is formed of a multilayer of 12a and 12b, but may be a single layer. In addition, the insulating film 12 is not necessarily provided in the case where mixing of impurities from the substrate 11 is sufficiently suppressed.

  Further, an insulating layer 31 may be provided between the transistor 17 and the insulating layer 21 so as to cover the transistor 17 as shown in FIG. The insulating layer 31 is preferably formed of an insulating material containing silicon. After the insulating layer 31 is formed, dangling bonds in the semiconductor layer 14 can be terminated with hydrogen contained in the insulating layer 31 by heating.

  In the light emitting element 24, the light emitting layer 22 is sandwiched between the first electrode 20 and the second electrode 23. One of the first electrode 20 and the second electrode 23 functions as an anode and the other functions as a cathode. The first electrode 20 is preferably made of a light-transmitting conductive material such as indium tin oxide (ITO). In addition to ITO, ITO containing silicon oxide, IZO (Indium Zinc Oxide) containing 2 to 20% zinc oxide in indium oxide, zinc oxide, or the like may be used.

  In addition, the light emitting layer 22 includes a light emitting material and is formed of a single layer or multiple layers. The light emitting layer 22 may be made of either an organic material or an inorganic material, or may include both an inorganic material and an organic material.

  The transistor 17 and the light emitting element 24 are electrically connected via a connecting portion 19a made of a conductor. The connecting portion 19a is provided on the insulating layer 21 and further reaches the semiconductor layer 14 through a contact hole that penetrates the insulating layer 21. In addition, a part or the whole of the connection portion 19 a is in contact with the first electrode 20.

  Openings 25 are provided in the insulating layers 12 a and 12 b and the gate insulating film 15 so that a part of the substrate 11 is exposed. The opening 25 is covered with the insulating film 21. The insulating film 21 is formed of a material that is insulative and has a high leveling effect. By forming the insulating film 21, a step due to the opening 25 is relaxed and leveled. The material of the insulating film 21 is a material having a skeletal structure composed of a bond of silicon and oxygen and containing at least hydrogen as a substituent or having at least one of fluorine, alkyl group, or aromatic hydrocarbon as a substituent. A coating film of so-called siloxane, acrylic, or polyimide is preferably used. In addition, the insulating film 21 is preferably a single layer as in the present embodiment, but in the case of a multilayer, the refractive index of the film stacked in the direction in which light emitted from the light emitting layer is extracted is small. It is desirable for the structure to become. At this time, it is desirable that the refractive index of the layer in contact with the substrate 11 is larger than that of the substrate 11 at a place where light is extracted.

  The light emitting element 24 is provided on the insulating film 21, and the light emitting element 24 and the opening 25 are partially or entirely overlapped. With such an element configuration, the number of layers that pass through until the light emitted from the light emitting element 24 goes out is smaller than in the prior art (see FIG. 10), so the influence of multiple interference between thin films is reduced. This makes it possible to reduce the change in the emission spectrum depending on the angle at which the emission extraction surface is viewed. In addition, it is desirable to use a material having a refractive index between the second electrode 23 and the substrate 11 as the material of the insulating layer 15.

  Note that there is no particular limitation on the structure of the transistor 17. A single gate type or a multi-gate type may be used. Further, a single drain structure, an LDD (Lightly Doped Drain) structure, or a structure in which an LDD region and a gate electrode overlap each other may be used.

  FIG. 2 is a top view of the light emitting device of the present invention. In FIG. 2, a partial cross section of a portion represented by a broken line AB is represented by the cross sectional view of FIG. 1. Accordingly, the same parts as those described above with reference to FIG. That is, 14 is a semiconductor layer, 16 is a gate electrode, 19b is a wiring, and 19a is a connection portion. Reference numeral 20 denotes a first electrode, 22 denotes a light emitting layer, and 25 denotes a portion where an opening exists. Although not shown in FIG. 1, 19c, 29a, and 29b are wirings, and 27 and 28 are transistors.

  As shown in FIG. 4, an insulating layer 18 made of a material different from that of the insulating layer 21 may be formed on the insulating layer 21. The insulating layer 18 has a role of preventing the insulating layer 21 from being etched up to the time of etching the connection portion 19a, and a role of preventing intrusion of water that adversely affects the light emitting element 24 from the insulating layer 21. It is made of a material such as a silicon film. Of course, if you don't mind these things, you don't need to provide them. Further, the formation of the insulating layer 18 increases the number of thin films. However, if the insulating layer 18 is formed of a material having a refractive index between the refractive indexes of the first electrode 20 and the insulating layer 21, reflection is achieved. It is possible to moderate the influence of the multiple interference due to.

  In addition, if there is no concern about the entry of water or the like from the insulating layer 21 into the light emitting element 24, the insulating layer 18 may be removed from the portion where the light emitting element 24 is formed as shown in FIG. . As a result, the number of layers in the light emitting portion is the same as that in FIG. 1, and the insulating layer 21 is also etched during the etching of the connecting portion 19a while suppressing the influence of multiple interference as compared with the configuration of FIG. Can be prevented.

  A structure in which the opening 25 is not formed until the glass substrate 11 is exposed as in the structure shown in FIG. In this case, since the number of layers until light is extracted from the light emitting layer 22 is reduced, the influence of multiple interference can be suppressed from the conventional configuration (FIG. 10), although not as much as FIG. 1 and FIG. Light transmittance can also be improved. In addition, since the refractive index of the films stacked in the direction in which light emitted from the light emitting layer is extracted is desirably reduced, the refractive index of the insulating layer 32 is that of the substrate 11 and the insulating layer 21. It is desirable to have a refractive index between. Note that in this configuration, since the substrate 11 is covered with the insulating layer 32, the substrate 11 can be used even when there is a risk of intrusion of impurities from the substrate 11.

  In the light emitting device of the present invention described above, the total number of light passing through is reduced when the light emitted from the light emitting element is taken out. Therefore, the number of times or the amount of reflection of light emitted from the light emitting element is reduced at the interface between layers, and as a result, multiple interference caused by reflected light is suppressed.

  As described above, the light-emitting device of the present invention has a structure that can suppress multiple interference, and is a light-emitting device with good visibility in which a change in the emission spectrum depending on the angle at which the light emission extraction surface is viewed is reduced. is there.

  In order to obtain the same effect as that of the present invention, an opening is formed in the insulating layer 21 until the lower insulating layer (insulating layers 12a, 12b, 15, 31, etc.) is exposed or until the substrate 11 is exposed. Such a configuration is also conceivable, but in such a configuration, the first electrode 20 and the light emitting layer 21 may be disconnected. In addition, since the end of the partition wall 30 must be created inside the opening, the aperture ratio is reduced.

(Embodiment 2)
In this embodiment mode, a method for manufacturing the light-emitting device of the present invention shown in FIGS. 1 and 2 will be described with reference to FIGS.

  After the insulating layers 12a and 12b are sequentially stacked on the substrate 11, a semiconductor layer is further formed on the insulating layer 12b.

  Next, the semiconductor layer is processed into a desired shape to form the semiconductor layer 14. Note that the processing may be performed by etching the semiconductor layer using a resist mask.

  Next, a gate insulating film 15 that covers the semiconductor layer 14, the insulating layer 12 b, and the like is formed, and a conductive layer is stacked over the gate insulating film 15.

  Subsequently, the electrode layer is processed into a desired shape to form the gate electrode 16. Here, wirings 29 a and 29 b are also formed together with the gate electrode 16. Note that the processing may be performed by etching the conductive layer using a resist mask.

  Next, a high concentration impurity is added to the semiconductor layer 14 using the gate electrode 16 as a mask. Thereby, the transistor 17 including the semiconductor layer 14, the gate insulating film 15, and the gate electrode 16 is formed.

  Note that there is no particular limitation on the process for manufacturing the transistor, and the process may be changed as appropriate so that a transistor having a desired structure can be formed.

  Subsequently, an opening 25 is formed in the insulating layers 12 a and 12 b and the gate insulating film 15. The openings 25 may be formed by etching using a resist mask until the substrate 11 is exposed, and can be performed by wet etching or dry etching. In the case of forming the insulating layer 31 as shown in FIG. 3, after forming the gate electrode 16, the insulating layer 31 is formed and heated to hydrogenate the semiconductor layer 14, and then the opening 25 is formed. Good.

  Next, an insulating layer 21 that covers the opening 25, the gate electrode 16, the gate insulating film 15, and the wirings 29a and 29b is formed. In the present embodiment, the insulating layer 18 is formed using an inorganic material having self-flatness such as siloxane. However, the present invention is not limited to this, and an organic material having self-flatness may be used. By using a substance having self-planarity for the insulating layer 21, a step formed by the opening 25 can be planarized. The insulating layer 21 may be a multi-layered film formed by combining a layer made of a substance having self-flatness and a layer made of a substance not having flatness. It is desirable to laminate so that the refractive index of the substrate 11 decreases as it goes in the direction of extraction.

  Subsequently, a contact hole that penetrates the insulating layer 21 and reaches the semiconductor layer 14 is formed. Then, a conductive layer that covers the contact hole, the insulating layer 21, and the like is formed. The conductive layer is processed into a desired shape, and the connection portion 19a, the wiring 19b, the wiring 19c, and the like are formed.

  Next, after forming a light-transmitting conductive layer so as to cover the connection portion 19 a and the like, the conductive layer is processed to form the first electrode 20. Here, the first electrode 20 is formed so that one part is in contact with the connection part and overlaps the opening part 25.

  Next, the partition layer 30 having an opening is formed so that a part of the first electrode is exposed. The partition layer 30 is formed so as to cover the connection portion 19 a and the insulating layer 21. The partition wall layer 18 may be formed by processing a photosensitive resin material into a desired shape by exposure / development, or after forming a layer made of an inorganic or organic material having no photosensitivity, It may be formed by etching into a desired shape.

  Subsequently, a light emitting layer 22 that covers the first electrode 20 exposed from the partition wall layer 18 is formed. The light emitting layer 22 may be formed by any method such as an evaporation method, an ink jet method, or a spin coating method.

  Next, a second electrode 23 that covers the light emitting layer 22 is formed. As a result, the light emitting layer 24 including the first electrode 20, the light emitting layer 22, and the second electrode 23 can be formed.

  Note that the structure as shown in FIGS. 3, 4, 5, and 6 can be easily obtained by those skilled in the art by appropriately changing the creation process shown in this embodiment mode.

  In the present embodiment, the configuration of the light emitting layer 22 will be described in detail.

  The light-emitting layer is formed of a charge injecting and transporting substance containing an organic compound or an inorganic compound and a light-emitting material. From the number of molecules thereof, a low molecular weight organic compound or a medium molecular weight organic compound (having no sublimation property and a molecular number of 20 Or an organic compound having a chain molecule length of 10 μm or less), including one or a plurality of layers selected from high-molecular organic compounds, and having an electron injection transport property or a hole injection transport property You may combine with a compound.

Among the charge injecting and transporting materials, materials having a particularly high electron transporting property include, for example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ )), tris (5-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ). Bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), quinoline skeleton or benzo And metal complexes having a quinoline skeleton. As a substance having a high hole-transport property, for example, 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (abbreviation: α-NPD), 4,4′-bis [ N- (3-methylphenyl) -N-phenyl-amino] -biphenyl (abbreviation: TPD) or 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine (abbreviation: TDATA) ), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (abbreviation: MTDATA) (ie, benzene ring-nitrogen) And a compound having a bond of

Among the charge injecting and transporting materials, materials having particularly high electron injecting properties include alkali metals or alkaline earths such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ) and the like. Metal compounds can be mentioned. In addition, a mixture of a substance having a high electron transport property such as Alq ₃ and an alkaline earth metal such as magnesium (Mg) may be used.

Among the charge injecting and transporting materials, examples of the material having a high hole injecting property include molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), and manganese oxide. Examples thereof include metal oxides such as (MnOx). In addition, phthalocyanine compounds such as phthalocyanine (abbreviation: H ₂ Pc) and copper phthalocyanine (CuPC) can be given.

  The light emitting layer may be configured to perform color display by forming light emitting layers having different emission wavelength bands for each pixel. Typically, a light emitting layer corresponding to each color of R (red), G (green), and B (blue) is formed. In this case as well, by providing a filter (colored layer) that transmits light in the emission wavelength band on the light emission side of the pixel, the color purity is improved and the pixel portion is mirrored (reflected). Prevention can be achieved. By providing the filter (colored layer), it is possible to omit a circularly polarized plate that has been considered necessary in the past, and it is possible to eliminate the loss of light emitted from the light emitting layer. Furthermore, a change in color tone that occurs when the pixel portion (display screen) is viewed obliquely can be reduced.

There are various kinds of light emitting materials. In the low molecular weight organic light emitting material, 4-dicyanomethylene-2-methyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (abbreviation: DCJT), 4- Dicyanomethylene-2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (abbreviation: DPA), periflanthene, 2,5-dicyano-1, 4-bis (10-methoxy-1,1,7,7-tetramethyljulolidyl-9-enyl) benzene, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8 - quinolinolato) aluminum (abbreviation: Alq _3), 9,9'-bianthryl, 9,10-diphenyl anthracene (abbreviation: DPA) and 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA) using a like Can . Other substances may also be used.

  On the other hand, the high molecular organic light emitting material has higher physical strength than the low molecular weight material, and the durability of the device is high. In addition, since the film can be formed by coating, the device can be manufactured relatively easily. The structure of the light emitting element using the high molecular weight organic light emitting material is basically the same as that when the low molecular weight organic light emitting material is used, and is cathode / organic light emitting layer / anode. However, when forming a light emitting layer using a high molecular weight organic light emitting material, it is difficult to form a laminated structure as in the case of using a low molecular weight organic light emitting material. . Specifically, the structure is cathode / light-emitting layer / hole transport layer / anode.

  Since the light emission color is determined by the material for forming the light emitting layer, a light emitting element exhibiting desired light emission can be formed by selecting these materials. Examples of the polymer electroluminescent material that can be used for forming the light emitting layer include polyparaphenylene vinylene, polyparaphenylene, polythiophene, and polyfluorene.

  The polyparaphenylene vinylene system includes derivatives of poly (paraphenylene vinylene) [PPV], poly (2,5-dialkoxy-1,4-phenylene vinylene) [RO-PPV], poly (2- (2′- Ethyl-hexoxy) -5-methoxy-1,4-phenylenevinylene) [MEH-PPV], poly (2- (dialkoxyphenyl) -1,4-phenylenevinylene) [ROPh-PPV] and the like. The polyparaphenylene series includes derivatives of polyparaphenylene [PPP], poly (2,5-dialkoxy-1,4-phenylene) [RO-PPP], poly (2,5-dihexoxy-1,4-phenylene). ) And the like. Polythiophene series includes polythiophene [PT] derivatives, poly (3-alkylthiophene) [PAT], poly (3-hexylthiophene) [PHT], poly (3-cyclohexylthiophene) [PCHT], poly (3-cyclohexyl). -4-methylthiophene) [PCHMT], poly (3,4-dicyclohexylthiophene) [PDCHT], poly [3- (4-octylphenyl) -thiophene] [POPT], poly [3- (4-octylphenyl) -2,2 bithiophene] [PTOPT] and the like. Examples of the polyfluorene series include polyfluorene [PF] derivatives, poly (9,9-dialkylfluorene) [PDAF], poly (9,9-dioctylfluorene) [PDOF], and the like.

  Note that when a hole-transporting polymer-based organic light-emitting material is sandwiched between an anode and a light-emitting polymer-based organic light-emitting material, hole injection properties from the anode can be improved. In general, an acceptor material dissolved in water is applied by spin coating or the like. In addition, since it is insoluble in an organic solvent, it can be stacked with the above-described light-emitting organic light-emitting material. Examples of the hole-transporting polymer organic light emitting material include a mixture of PEDOT and camphor sulfonic acid (CSA) as an acceptor material, a mixture of polyaniline [PANI] and polystyrene sulfonic acid [PSS] as an acceptor material, and the like. .

  The light emitting layer can be configured to emit monochromatic or white light. In the case of using a white light emitting material, color display can be made possible by providing a filter (colored layer) that transmits light of a specific wavelength on the light emission side of the pixel.

To form a light emitting layer that emits white light, for _{example, Alq 3, Alq 3, Alq} 3 doped with Nile Red which is partly red light emitting pigment, p-EtTAZ, by TPD (aromatic diamine) evaporation A white color can be obtained by sequentially laminating. In the case where the EL is formed by a coating method using spin coating, it is preferable that baking is performed by vacuum heating after coating. For example, a poly (ethylenedioxythiophene) / poly (styrenesulfonic acid) aqueous solution (PEDOT / PSS) that acts as a hole injection layer is applied and baked on the entire surface, and then a luminescent center dye (1, 1,4,4-tetraphenyl-1,3-butadiene (TPB), 4-dicyanomethylene-2-methyl-6- (p-dimethylamino-styryl) -4H-pyran (DCM1), Nile Red, Coumarin 6 Etc.) A doped polyvinyl carbazole (PVK) solution may be applied to the entire surface and fired.

  The light emitting layer can also be formed as a single layer, and an electron transporting 1,3,4-oxadiazole derivative (PBD) may be dispersed in hole transporting polyvinyl carbazole (PVK). Further, white light emission can be obtained by dispersing 30 wt% PBD as an electron transporting agent and dispersing an appropriate amount of four kinds of dyes (TPB, coumarin 6, DCM1, Nile red). In addition to the light-emitting element that can emit white light as shown here, a light-emitting element that can obtain red light emission, green light emission, or blue light emission can be manufactured by appropriately selecting the material of the light-emitting layer.

  Note that when a hole-transporting polymer-based organic light-emitting material is sandwiched between an anode and a light-emitting polymer-based organic light-emitting material, hole injection properties from the anode can be improved. In general, an acceptor material dissolved in water is applied by spin coating or the like. In addition, since it is insoluble in an organic solvent, it can be stacked with the above-described light-emitting organic light-emitting material. Examples of the hole-transporting polymer organic light emitting material include a mixture of PEDOT and camphor sulfonic acid (CSA) as an acceptor material, a mixture of polyaniline [PANI] and polystyrene sulfonic acid [PSS] as an acceptor material, and the like. .

  Furthermore, a triplet excitation material containing a metal complex or the like may be used for the light emitting layer in addition to a singlet excitation light emitting material. For example, among red light emitting pixels, green light emitting pixels, and blue light emitting pixels, a red light emitting pixel having a relatively short luminance half time is formed of a triplet excitation light emitting material, and the other A singlet excited luminescent material is used. The triplet excited luminescent material has a feature that the light emission efficiency is good, so that less power is required to obtain the same luminance. That is, when applied to a red pixel, the amount of current flowing through the light emitting element can be reduced, so that reliability can be improved. As a reduction in power consumption, a red light-emitting pixel and a green light-emitting pixel may be formed using a triplet excitation light-emitting material, and a blue light-emitting pixel may be formed using a singlet excitation light-emitting material. By forming a green light-emitting element having high human visibility with a triplet excited light-emitting material, power consumption can be further reduced.

  Examples of triplet excited luminescent materials include those using a metal complex as a dopant, and metal complexes having a third transition series element platinum as the central metal and metal complexes having iridium as the central metal are known. Yes. The triplet excited light-emitting material is not limited to these compounds, and a compound having the above structure and having an element belonging to group 8 to 10 in the periodic table as a central metal can also be used.

  The substances forming the light-emitting layer listed above are examples, and functionalities such as a hole injection transport layer, a hole transport layer, an electron injection transport layer, an electron transport layer, a light emission layer, an electron block layer, and a hole block layer are included. A light emitting element can be formed by appropriately stacking each layer. Moreover, you may form the mixed layer or mixed junction which combined these each layer. The layer structure of the light-emitting layer can be changed, and instead of having a specific electron injection region or light-emitting region, it is possible to provide a modification with an electrode for this purpose or a dispersed light-emitting material. Can be permitted without departing from the spirit of the present invention.

  A light-emitting element formed using the above materials emits light by being forward-biased. A pixel of a display device formed using a light-emitting element can be driven by a simple matrix method or an active matrix method. In any case, each pixel emits light by applying a forward bias at a specific timing, but is in a non-light emitting state for a certain period. By applying a reverse bias during this non-light emitting time, the reliability of the light emitting element can be improved. The light emitting element has a degradation mode in which the light emission intensity decreases under a constant driving condition and a degradation mode in which the non-light emitting area is enlarged in the pixel and the luminance is apparently decreased. However, alternating current that applies a bias in the forward and reverse directions. By performing a typical drive, the progress of deterioration can be slowed, and the reliability of the light emitting device can be improved.

  In this embodiment, an example of the structure of a light emitting device using the present invention will be described with reference to FIG. In addition, even if the shapes are different, parts showing similar functions are denoted by the same reference numerals, and explanations thereof are omitted. In this example, the transistor 17 having an LDD structure using the top hat type gate electrode 16 is connected to the light emitting element 24 through the connection portion 19a, and the insulation as shown in FIG. In this configuration, the film 31 is formed.

  FIG. 9A illustrates a structure in which the first electrode 20 is formed using a light-transmitting conductive film, and light emitted from the light-emitting layer 22 is extracted to the substrate 11 side. Reference numeral 40 denotes a counter substrate, which is fixed to the substrate 11 using a sealant or the like after the light emitting element 24 is formed. Filling the counter substrate 40 and the element with a light-transmitting resin 45 or the like and sealing it can prevent the light emitting element 24 from being deteriorated by moisture. Moreover, it is desirable that the resin 45 has a hygroscopic property. Further, if the desiccant 46 having high translucency is dispersed in the resin 45, the influence of moisture can be further suppressed, which is a more desirable form.

  In FIG. 9B, both the first electrode 20 and the second electrode 23 are formed of a light-transmitting conductive film, and light can be extracted to both the substrate 11 and the substrate 40. Yes. Further, in this configuration, by providing the polarizing plates 41 and 42 outside the substrate 11 and the counter substrate 40, it is possible to prevent the screen from being seen through, and visibility is improved. Protective films 43 and 44 are preferably provided outside the polarizing plates 41 and 42.

Sectional drawing which shows the structure of the light-emitting device of this invention. FIG. 6 is a top view illustrating a structure of a light-emitting device of the present invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. Sectional drawing which shows the structure of the light-emitting device of this invention. The figure which shows the structure of the conventional light-emitting device.

Claims (7)

A first insulating layer formed on the substrate;
An opening reaching the substrate is formed in the first insulating layer,
A second insulating layer is formed to cover the opening;
A light-emitting device, wherein a light-emitting element is provided on the second insulating layer so as to overlap at least part of the opening. A substrate,
A first insulating layer formed on the substrate; a semiconductor layer formed on the insulating layer;
A gate insulating layer formed over the semiconductor layer;
A gate insulating layer formed on the semiconductor layer and the gate insulating layer;
The gate insulating layer is provided with an opening that penetrates the first insulating layer and reaches the substrate,
A second insulating layer is formed to cover the gate insulating layer, the gate electrode and the opening;
A light-emitting device, wherein a light-emitting element is provided on the second insulating layer so as to overlap at least a part of the light-emitting opening. In claim 1 or claim 2,
The light-emitting device, wherein the first insulating layer and the second insulating layer have a single layer structure. In claim 1 or claim 2,
The light-emitting device, wherein the first insulating layer and / or the second insulating layer has a multilayer structure. In any one of Claims 1 thru | or 3,
The light-emitting element has a first electrode, a light-emitting layer, and a second electrode,
The first electrode is formed closer to the substrate than the second electrode;
The light-emitting device, wherein the second insulating layer has a refractive index between the refractive index of the first electrode and the refractive index of the substrate. In any one of Claims 1 thru | or 4,
The light-emitting element has a first electrode, a light-emitting layer, and a second electrode,
The first electrode is formed closer to the substrate than the second electrode;
The light emitting device according to claim 1, wherein a refractive index of each layer existing between the first electrode and the substrate in the opening is smaller as it is closer to the substrate. In any one of Claims 1 thru | or 4,
The light-emitting element has a first electrode, a light-emitting layer, and a second electrode,
The first electrode is formed closer to the substrate than the second electrode;
The light emitting device according to claim 1, wherein a refractive index of each layer existing between the first electrode and the substrate in the opening is smaller as it is closer to the substrate.

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