JP2006302879A - Light emitting element, light emitting device equipped with light emitting element, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element wherein a capping layer containing a triarylamine derivative and a carbazole derivative is provided to substantially enhance light extraction efficiency, a light emitting device equipped with this light emitting element, and its manufacturing method. <P>SOLUTION: This light emitting element 1 has a top emission type structure in which an anode 11 made of metal, a hole transport layer 12, a luminescent layer 13, an electron transport layer 14, a translucent cathode 15, and the capping layer 16 are laminated one by one on a glass substrate 10. Since it has the capping layer 16 having a refractive index higher than that of the translucent cathode 15, light extraction efficiency can be substantially enhanced. In addition, since the capping layer can be deposited at a temperature which is not very high, it gives no damage to the light emitting element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting element used in an organic electroluminescence display device, a light-emitting device including the light-emitting element, and a method for manufacturing the light-emitting element, and in particular, a light-emitting element with significantly improved light extraction efficiency and the light-emitting element. The present invention relates to a light emitting device and a method for manufacturing the same.

  An organic electroluminescence (EL) display device has features such as thinness, wide viewing angle, low power consumption, and excellent moving image display characteristics, and is expected as a next-generation image display device. An organic EL light emitting element (hereinafter referred to as a light emitting element) is used in such an organic EL display device, has at least one light emitting layer between two electrodes, and applies a voltage between the electrodes. The light emitting layer emits light and an image can be displayed.

  Conventionally, by forming a transparent electrode as an anode on a glass substrate, for example, ITO (indium tin oxide), a charge transport layer and a light emitting layer made of an organic material, and finally a cathode made of a metal such as Al, in this order, A light emitting element having a bottom emission structure that emits light from the bottom is generally manufactured.

  In recent years, a light-emitting element having a top emission structure in which a metal having a high work function is used for an anode and light is emitted from above has been used. Unlike a light emitting element having a bottom emission structure in which the area of the light emitting part is limited by the pixel circuit, a light emitting element having a top emission structure has an advantage that a wide light emitting part can be obtained. In a light emitting device having a top emission structure, a semi-transparent electrode such as LiF / Al / Ag (Non-patent Document 1), Ca / Mg (Non-patent Document 2), LiF / MgAg, or the like is used for a cathode.

  In such a light-emitting element, when light emitted from the light-emitting layer is incident on another film, if the light is incident at an angle or more, the light is totally reflected at the interface between the light-emitting layer and another film thickness. For this reason, only a part of the emitted light can be used. In recent years, in order to improve the light extraction efficiency, a light emitting element in which a “capping layer” having a high refractive index is provided outside a translucent electrode having a low refractive index has been proposed (Non-Patent Documents 1 and 2).

The effect of the capping layer in the light emitting device having the top emission structure is shown in Non-Patent Document 2. In Non-Patent Document 2, a light-emitting element using Ir (ppy) ₃ (fac-tris- (2-phenylpyridinate) indium) as a light-emitting material has a current efficiency of 38 cd / A when there is no capping layer. However, in the light-emitting element using ZnSe (film thickness 60 nm) as the capping layer, the efficiency was about 1.7 times as high as 64 cd / A.

  Non-Patent Document 2 shows that the transmissivity maximum of the translucent electrode and the capping layer do not always coincide with the maximum efficiency, and the maximum point of light extraction efficiency is determined by the interference effect. It has been shown.

Applied Physics Letters, USA, 2001, 78, 544-546. Applied Physics Letters, USA, 2003, 82, 466-468.

  For the formation of the capping layer, it has been proposed to use a metal mask with high definition. However, such a metal mask has a problem that the alignment accuracy is deteriorated due to thermal distortion. That is, ZnSe used in Non-Patent Document 2 has a high melting point of 1100 ° C. or higher and cannot be deposited at an accurate position with a high-definition mask. Many inorganic substances have high deposition temperatures and are not suitable for use with high-definition masks, and may damage the light-emitting elements themselves. Further, in the film formation by the sputtering method, the light emitting element is damaged, and therefore a capping layer containing an inorganic material cannot be used.

In Non-Patent Document 1, tris- (8-hydroxyquinolinato) aluminum (Alq ₃ ) is used as a capping layer for adjusting the refractive index, but Alq ₃ is known as an organic EL material that emits green light. As shown in FIG. 8, it has weak absorption near 450 nm used for blue light emitting elements. FIG. 8 is a diagram showing the relationship between the wavelength, refractive index, and extinction coefficient in the capping layer using Alq ₃ . In the figure, the solid line indicates the refractive index, and the broken line indicates the extinction coefficient. For this reason, the blue light emitting device has a problem that both the color purity is lowered and the light extraction efficiency is lowered.

  The present invention has been made to solve the above-described problems, and can be stably formed as a capping layer material at a temperature that is not so high, and also absorbs in each wavelength region of blue, green, and red. It is an object of the present invention to provide a light emitting element including a capping layer made of a material having no light emitting element, a light emitting device including the light emitting element, and a manufacturing method thereof.

  In order to solve the above-described problems and achieve the object, in the light emitting device of the present invention, a first electrode, an organic layer that is disposed above the first electrode and includes a light emitting layer, A second electrode disposed on the organic layer and transmitting light from the light emitting layer; and a capping layer disposed on the second electrode and made of a material having a refractive index larger than that of the constituent material of the second electrode. And the material constituting the capping layer includes at least one selected from the group consisting of triarylamine derivatives, carbazole derivatives, benzimidazole derivatives, and triazole derivatives.

  In the light emitting device of the present invention, the material constituting the capping layer includes a material having a band gap of 3.2 eV or more.

  In the light-emitting element of the present invention, the material constituting the capping layer contains a triphenylamine derivative.

  In the light emitting device of the present invention, the material constituting the capping layer is 4,4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (TPD), 4,4. ', 4' '-tris [(3-methylphenyl) phenylamino] triphenylamine (m-MTDATA), 1,3,5-tris [N, N-bis (2-methylphenyl) -amino] -benzene (O-MTDAB), 1,3,5-tris [N, N-bis (3-methylphenyl) -amino] -benzene (m-MTDAB), 1,3,5-tris [N, N-bis ( 4-methylphenyl) -amino] -benzene (p-MTDAB) and at least selected from the group consisting of 4,4′-bis [N, N-bis (3-methylphenyl) -amino] -diphenylmethane (BPPM) 1 Characterized in that it comprises a.

  In the light emitting device of the present invention, the material constituting the capping layer may be 4,4′-dicarbazolyl-1,1′-biphenyl (CBP), 4,4 ′, 4 ″ -tris (N -Carbazole) triphenylamine (TCTA), 2,2 ', 2 "-(1,3,5-benzenetolyl) tris- [1-phenyl-1H-benzimidazole] (TPBI), and 3- It contains at least one selected from the group consisting of (4-biphenyl) -4-phenyl-5-t-butylphenyl-1,2,4-triazole (TAZ).

  In the light emitting device of the present invention, the capping layer has a thickness in the range of 30 nm to 120 nm.

  In the light emitting device of the present invention, the refractive index of the capping layer is 1.75 or more at least in the range of the wavelength of light transmitted through the capping layer from 380 nm to 780 nm. .

  In the light emitting device of the present invention, the extinction coefficient of the capping layer is 0.12 or less at least in a wavelength range of 380 nm to 780 nm of light passing through the capping layer. To do.

  The light-emitting device of the present invention includes a plurality of the light-emitting elements, and the plurality of light-emitting elements includes a first light-emitting element and a second light-emitting element that emits light in a color different from the first light-emitting element; The first and second light emitting elements are at least classified into third light emitting elements that emit light in different colors, and the capping layers of the first to third light emitting elements have different thicknesses.

  In the light emitting device of the present invention, the capping layers of the first to third light emitting elements are made of the same material.

In the light emitting device of the present invention, the first light emitting element emits red light, the second light emitting element emits green light, the third light emitting element emits blue light, and the capping of the first light emitting element. The film thickness d _{R of} the layer, the film thickness d _{G of the} capping layer of the second light emitting element, and the film thickness d _{B of the} capping layer of the third light emitting element are in a relational expression of d _R > d _G > d _B. It is characterized by satisfying.

  In the light emitting device manufacturing method of the present invention, the light emitting device manufacturing method may further include the constituent material of the capping layer on the second electrode corresponding to the first and second light emitting elements. Forming the intermediate layer on the second electrode corresponding to the first light emitting element and forming the capping layer on the second electrode corresponding to the second light emitting element by stacking; and The capping layer is stacked on the intermediate layer corresponding to the light emitting element and the second electrode corresponding to the third light emitting element, thereby corresponding to the first and third light emitting elements. Forming the capping layer on the second electrode, and thereby forming the capping layer of the first to third light emitting devices.

  In the method for manufacturing a light emitting device of the present invention, the sum of the thicknesses of the capping layers corresponding to the second and third light emitting elements is equal to the thickness of the capping layer corresponding to the first light emitting elements. It is characterized by being substantially equal.

  Further, in the method for manufacturing a light emitting device of the present invention, the first electrode, an organic layer disposed above the first electrode and including a light emitting layer, and disposed on the organic layer, A second electrode that transmits light from the light emitting layer, and a capping layer that is disposed on the second electrode and is made of a material having a refractive index larger than that of the constituent material of the second electrode and a band gap of 3.2 eV or more. A method of manufacturing a light-emitting device having a plurality of first to third light-emitting elements each provided on a substrate, wherein the capping layer is formed on the second electrode corresponding to the first and second light-emitting elements. Forming an intermediate layer on the second electrode corresponding to the first light emitting element and forming the capping layer on the second electrode corresponding to the second light emitting element by laminating materials; The intermediate layer corresponding to the first light emitting element The capping layer is formed on the second electrode corresponding to the second and third light emitting elements by laminating the constituent material of the capping layer on the second electrode corresponding to the third light emitting element. Forming a capping layer of the first to third light emitting elements.

  In the method for manufacturing a light emitting device of the present invention, the sum of the thicknesses of the capping layers corresponding to the second and third light emitting elements is equal to the thickness of the capping layer corresponding to the first light emitting elements. It is characterized by being substantially equal.

  In the method for manufacturing a light emitting device according to the present invention, the first light emitting element is red, the second light emitting element is one of blue and green, and the third light emitting element is blue and green. Each of the other colors emits light.

In the light emitting device of the present invention, the first electrode, the organic layer disposed above the first electrode and including the light emitting layer, and disposed on the organic layer, the light emitting layer And a capping layer that is disposed on the second electrode and has a refractive index larger than that of the constituent material of the second electrode and is made of a material having a band gap of 3.2 eV or more. The plurality of light emitting elements are classified into a first light emitting element that emits red light, a second light emitting element that emits green light, and a third light emitting element that emits blue light. A thickness d _{R of the} capping layer of one light emitting element, a thickness d _{G of the} capping layer of the second light emitting element, and a thickness d _{B of the} capping layer of the third light emitting element are different from each other. And

In the light emitting device of the present invention, the capping layer thickness d _R of the first light emitting device, the capping layer thickness d _{G of} the second light emitting device, and the third light emitting device of the third light emitting device. The film thickness d _{B of the} capping layer satisfies a relational expression of d _R > d _G > d _B.

  According to the present invention, since the capping layer having a refractive index higher than that of the semitransparent electrode is provided outside the transparent or semitransparent electrode, a light emitting element capable of significantly improving the light extraction efficiency can be obtained. . In addition, since a film can be formed at a temperature of 500 ° C. or lower by using a triarylamine derivative or a carbazole derivative for the capping layer, each color can be used without damaging the light emitting element and using a high-definition mask. Can be optimized, and can be suitably applied to a full color display, and can display a clear and bright image with good color purity.

  In addition, according to the light emitting device of the present invention, by forming the capping layer with the same material for a plurality of light emitting elements, it is possible to reduce labor and cost required for the film forming process of the capping layer and to improve the productivity of the light emitting device. It is possible to contribute to improvement and cost reduction. Furthermore, by setting the film thickness of the capping layer to correspond to different wavelengths of red, blue, and green, the light extraction efficiency of the light emitting element corresponding to each color can be further improved.

  Further, according to the method for manufacturing a light emitting device according to the present invention, when the materials of the capping layers in the first to third light emitting elements are the same and the film thicknesses are different, compared to the case where each capping layer is formed in a separate process. The film forming process can be simplified, and it is possible to contribute to improving the productivity of the light emitting device.

  Embodiments and examples of a light-emitting element, a light-emitting device including the light-emitting element, and a method for manufacturing the light-emitting element according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following embodiments and examples.

[Light emitting element]
First, the light emitting device according to the present invention will be described. FIG. 1 is a schematic sectional side view showing a light emitting device according to an embodiment of the present invention. In addition, in each figure, the same code | symbol shows the same or equivalent part. In FIG. 1, a light emitting device 1 is a light emitting device having a top emission structure. On a substrate, for example, a glass substrate 10, an anode 11 as a first electrode made of metal, a hole transport layer 12, a light emitting layer 13, an electron transport layer. 14, a translucent cathode 15 as a second electrode, and a capping layer 16 are sequentially laminated.

  Since the light emitting element 1 has a top emission structure, the glass substrate 10 is not necessarily transparent. The hole transport layer 12 serves to transport holes from the anode 11 to the light emitting layer 13, and the electron transport layer 14 serves to transport electrons from the translucent cathode 15 to the light emitting layer 13. In the light emitting layer 13, holes from the hole transport layer 12 and electrons from the electron transport layer 14 are recombined, so that the electronic state of the organic material in the light emitting layer 13 is a singlet excited state or a triplet excited state. When excited to a state and returned from these excited states to a stable ground state, fluorescence or phosphorescence is generated, respectively.

  The capping layer 16 can be stably formed at a temperature that is not so high, and is made of a material that does not absorb in the wavelength regions of blue, green, and red. The material constituting the capping layer 16 will be described later.

  The total thickness of the anode 11, the hole transport layer 12, the light emitting layer 13, the electron transport layer 14, and the translucent cathode 15 as described above is about 200 nm to 600 nm. The film thickness of the capping layer 16 is preferably 30 nm to 120 nm, for example. When the capping layer 16 is in the above film thickness range, good light extraction efficiency can be obtained. Note that the thickness of the capping layer 16 can be changed as appropriate in accordance with the type of the light emitting material used for the light emitting element, the thickness of the light emitting element other than the capping layer 16, and the like. Examples of the translucent cathode 15 include Ca / Mg, MgAg, MgAl, ITO, and IZO.

  For the film formation of each layer to be laminated, a chemical method such as a CVD (Chemical Vapor Deposition) method is used as the film formation method from the viewpoint of ensuring the denseness of the film and good step coverage (step coverage). In addition to the CVD method, for example, a vacuum deposition method or the like can be applied. Furthermore, a heat vapor deposition method, an inkjet method, gravure printing, or the like may be applied.

  Although the top emission structure light emitting element 1 has been described with reference to FIG. 1, the present invention is not limited to this, and the bottom emission structure light emitting element or the dual emission structure emitting light from both the top and bottom directions is used. The same applies to a light-emitting element. In these cases, an electrode in a direction in which light is extracted from the light emitting element to the outside needs to be transparent or translucent.

  In FIG. 1, when a capping layer 16 is formed on a light emitting device having a three-layer structure in which a layer sandwiched between the anode 11 and the semitransparent cathode 15 is composed of a hole transport layer 12, a light emitting layer 13, and an electron transport layer 14. As an example, the structure of the light-emitting element is not limited to this three-layer structure, and a five-layer structure and a four-layer structure in which a hole injection layer and an electron injection layer are added according to various conditions. A light-emitting element adopting various structures such as a two-layer structure or a single-layer structure having only a light-emitting layer can also be used.

  The refractive index of the material constituting the capping layer 16 is preferably larger than the refractive index of the adjacent electrode. That is, the light extraction efficiency of the light-emitting element 1 is improved by the capping layer 16, but the effect is that the higher the reflectance at the interface between the capping layer 16 and the material in contact with the capping layer 16, the higher the light interference. This is effective because of its large effect. Therefore, the refractive index of the material constituting the capping layer 16 is preferably larger than the refractive index of the adjacent electrode, and more preferably the refractive index is 1.5 or more.

  FIG. 2 is a diagram showing a relationship between a wavelength, a refractive index, and an extinction coefficient in a capping layer using CBP represented by the structural formula (7) described later. In the figure, the solid line indicates the refractive index, and the broken line indicates the extinction coefficient. The refractive index is the value of the real part of the complex refractive index, and the extinction coefficient means the value of the imaginary part of the complex refractive index. As a method for measuring the refractive index and extinction coefficient, a conventionally known n & k method is used. As is clear from this figure, the refractive index of CBP is about 1.75 or more at any wavelength. Further, no extinction occurs in the vicinity of 450 nm used for the blue light emitting element. Similarly, no extinction occurs at other wavelengths, and the extinction coefficient of the capping layer is 0.12 or less at least when the wavelength of light passing through the capping layer is in the range of 380 nm to 780 nm. Accordingly, since no absorption occurs in each of the blue, green, and red wavelength regions, the light-emitting element including the capping layer can be suitably used for a full color display or the like.

  The band gap of the material constituting the capping layer 16 is preferably 3.2 eV or more. Here, the band gap of 3.2 eV corresponds to the light wavelength of about 387 nm, and 3.1 eV corresponds to about 400 nm. Therefore, in order for almost the entire region of 380 nm to 780 nm, which is the wavelength of the visible portion, to be transparent, the band gap of the material constituting the capping layer 16 is preferably 3.2 eV or more. On the other hand, a band gap of less than 3.2 eV is not preferable because it affects the blue wavelength.

  More specifically, as the band gap of the material constituting the capping layer 16 is larger, the light absorption edge due to the electrons transitioning the band gap moves to the short wavelength side. Therefore, as the band gap of the material is larger, the light absorption edge is moved away from the visible portion, so that the light absorption of the material becomes smaller and transparent. Since the material constituting the capping layer 16 is desirably transparent in almost the entire visible portion, it is preferable that the material has a large band gap. If the band gap is 3.2 eV or more, the light absorption edge is from the visible portion. It is more preferable because it comes off.

  The band gap of the material constituting the capping layer 16 can be calculated by measuring the long wavelength side absorption edge wavelength of the light absorption spectrum of the material.

  As a material constituting the capping layer 16, a triarylamine derivative can be used. Examples of the triarylamine derivative include 4,4′-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl represented by the structural formula (1) (hereinafter referred to as “TPD”). 4,4 ′, 4 ″ -tris [(3-methylphenyl) phenylamino] triphenylamine (hereinafter referred to as “m-MTDATA”) represented by Structural Formula (2), Structural Formula (3 1,3,5-tris [N, N-bis (2-methylphenyl) -amino] -benzene (hereinafter referred to as “o-MTDAB”), represented by the structural formula (4) 1,3,5-tris [N, N-bis (3-methylphenyl) -amino] -benzene (hereinafter referred to as “m-MTDAB”), 1,3 represented by the structural formula (5) , 5-Tris [N, N-bis (4-methylphenyl) -amino ] -Benzene (hereinafter referred to as “p-MTDAB”), 4,4′-bis [N, N-bis (3-methylphenyl) -amino] -diphenylmethane (hereinafter referred to as structural formula (6)) , Described as “BPPM”). These materials can be used alone or as a mixture of a plurality of materials.

  As the capping layer 16, a triphenylamine derivative can also be used in the same manner as the triaryl derivative.

  As another material constituting the capping layer 16, a carbazole derivative can be used. Examples of the carbazole derivative include 4,4′-dicarbazolyl-1,1′-biphenyl (hereinafter referred to as “CBP”) represented by the structural formula (7), and 4 represented by the structural formula (8). , 4 ′, 4 ″ -tris (N-carbazole) triphenylamine (hereinafter referred to as “TCTA”) and the like. These materials can be used alone or as a mixture of a plurality of materials.

  As another material constituting the capping layer 16, a benzimidazole derivative can be used. As the benzimidazole derivative, for example, 2,2 ′, 2 ″-(1,3,5-benzenetolyl) tris- [1-phenyl-1H-benzimidazole] represented by the structural formula (9) (Hereinafter referred to as “TPBI”).

  As another material constituting the capping layer 16, a triazole derivative can be used. Examples of the triazole derivative include 3- (4-biphenyl) -4-phenyl-5-t-butylphenyl-1,2,4-triazole (hereinafter referred to as “TAZ”) represented by the structural formula (10). )).

As a material for the capping layer 16 having a band gap of 3.2 eV or more, there are TPD (3.2 eV), m-MTDATA (3.2 eV), TAZ (4.0 eV), and the like. Examples of the material of the capping layer 16 having a band gap of less than 3.2 eV include Alq ₃ , Almq ₃ , and CuPc.

[Light emitting device]
Next, the light emitting device according to the present invention will be described. FIG. 3 is a schematic sectional side view showing the light emitting device according to the embodiment of the present invention. In FIG. 3, the light emitting device 50 includes the first light emitting element 20, the second light emitting element 30, and the third light emitting element 40 as the above light emitting elements on the same substrate 10.

  The first light-emitting element 20, the second light-emitting element 30, and the third light-emitting element 40 are the anode 11, the hole transport layer 12, the light-emitting layer 13, the electron transport layer 14, and the translucent as the second electrode, respectively. Cathodes 15 </ b> A to 15 </ b> C and capping layers 16 </ b> A to 16 </ b> C are provided, and these can be sequentially stacked in the same manner as the light-emitting element 1 described with reference to FIG. 1.

  The first light emitting element 20, the second light emitting element 30, and the third light emitting element 40 emit light in red, green, and blue, respectively, and the capping layers 16A to 16C may be made of different materials or may be made of the same material. It may be formed from a material. When the capping layers 16A to 16C are formed of the same material, the labor and cost required for the film formation process of the capping layers 16A to 16C can be reduced, which contributes to improvement in productivity and cost reduction of the light emitting device 50. It becomes possible.

The film thickness of the capping layers 16A to 16C may be the same or different. In particular, film thickness d _R of the capping layer 16A of the first light emitting element 20, the film thickness of d _G of the capping layer 16B in the second light emitting element 30, the thickness of the capping layer 16C of the third light emitting element 40 and d _B Then, it is preferable that the relational expression of d _R > d _G > d _B is satisfied. Among red, blue, and green, the emission wavelength is the longest for red and the shortest for blue. Therefore, by setting the film thickness of the capping layers 16A to 16C corresponding to these emission wavelengths, The light extraction efficiency of the first light emitting element 20 to the third light emitting element 40 can be further improved.

  Note that all the descriptions of the above-described light-emitting elements such as the material of the capping layer, the film thickness, the band gap, and the refractive index also apply to the first light-emitting element 20, the second light-emitting element 30, and the third light-emitting element 40 in the light-emitting device 50. The same can be applied. The number of light-emitting elements is not limited to three, and a larger number of light-emitting elements can be formed over the same substrate or can be formed over different substrates.

[Method of manufacturing light emitting device]
Next, a method for manufacturing a light emitting device according to the present invention will be described. 4 to 6 are schematic cross-sectional side views illustrating a method for manufacturing a light-emitting device according to an embodiment of the present invention. In these drawings, the illustration from the semitransparent cathodes 15A to 15C to the anode 11 is simplified for easy understanding.

  In FIG. 4, the light emitting device 50 includes a first light emitting element 20, a second light emitting element 30, and a third light emitting element 40 on the same substrate 10. The first light-emitting element 20, the second light-emitting element 30, and the third light-emitting element 40 are the anode 11, the hole transport layer 12, the light-emitting layer 13, the electron transport layer 14, and the translucent as the second electrode, respectively. Cathodes 15A to 15C are provided, and these can be sequentially stacked in the same manner as the light-emitting element 1 described in FIG.

When the capping layers 16A to 16C are formed of the same material with different film thicknesses, first, as shown in FIG. the constituent material of the layers laminated by mask deposition through a vapor deposition mask 19A such as a shadow mask, to form a first layer 17 made of the constituent material with a thickness d _1. At this time, since the same material is further laminated on the upper surface of the first layer 17 made of the constituent material of the capping layer formed on the semitransparent cathode 15A in the first light emitting element 20, the so-called capping layer The intermediate layer 17 is formed. On the other hand, the layer made of the constituent material of the capping layer formed on the semitransparent cathode 15B in the second light emitting element 30 becomes the capping layer 16B itself.

Next, as shown in FIG. 6, the second layer 18 made of the constituent material of the capping layer is deposited on the intermediate layer 17 in the first light emitting element 20 and the semitransparent cathode 15C in the third light emitting element 40, respectively. A film thickness d ₂ is formed by mask vapor deposition via 19B. At this time, in the first light emitting element 20, the capping layer 16A is formed by the intermediate layer 17 and the second layer 18 formed thereon. On the other hand, the second layer 18 formed on the translucent cathode 15C in the third light emitting element 40 becomes the capping layer 16C itself.

Since the capping layer 16A in the first light emitting device 20 is composed of the capping layer 17 and the capping layer 18 formed thereon, d _R = d ₁ + d _{2 where} d _R is the thickness of the capping layer 16A. It becomes. That is, the film thickness of the capping layer 16A in the first light emitting element 20 is the sum of the film thickness d ₁ of the capping layer 16B in the second light emitting element 30 and the film thickness d ₂ of the capping layer 16C in the third light emitting element 40. Almost equal. However, the sum of the film thicknesses may not be a sum that is strictly added depending on the film forming conditions of the capping layer, but is allowed to be within 10% with respect to the film thickness d _R of the capping layer 16A.

  As described above, since the capping layers 16A to 16C having different thicknesses are formed in two steps, the materials of the capping layers 16A to 16C in the first light emitting element 20 to the third light emitting element 40 are the same and the film thicknesses are different. In this case, the film forming process can be simplified as compared with the case where each of the capping layers 16A to 16C is formed in a separate process, and it is possible to contribute to the improvement of the productivity of the light emitting device.

  Note that the description of the light-emitting element and the light-emitting device described above can be similarly applied to the method for manufacturing the light-emitting device described with reference to FIGS.

Hereinafter, based on an Example, this invention is demonstrated further more concretely. A red light emitting device according to the present invention was produced as follows. First, a 20 nm-thick copper phthalocyanine (CuPc) film, which is a hole injection layer, was deposited on a Ni anode having a thickness of 100 nm deposited on a substrate by a sputtering method. Subsequently, N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine (NPB) having a film thickness of 40 nm, which is a hole transport layer, was formed by vapor deposition. Then, Alq ₃ which is a light emitting layer, and 4- (dicyanomethylene) -2-t-butyl-6- (1,1,7,7, -tetramethyljulolidyl-9-enyl) -4H-pyran ( DCJTB) and two sources. The film thickness of Alq ₃ was 30 nm, and DCJTB having a volume ratio of 1% was simultaneously deposited.

Further, Alq ₃ with a film thickness of 40 nm as an electron transport layer, Ca with a film thickness of 12 nm as a cathode and Mg with a film thickness of 12 nm were continuously formed by an evaporation method. Finally, the film thickness of CBP as a capping layer was changed in the range of 0 nm to 100 nm, and a film was formed by vapor deposition. In this embodiment, the red pixel forming method is described, but the green and blue pixels are formed by the same method although the film thickness and material are different. In forming red, green, and blue pixels, the positions are selected and formed. Therefore, a metal mask having an opening at the film formation position is precisely aligned with the substrate, and the film formation surface side of the substrate Vapor deposition is performed by attaching a metal mask to the surface.

  The light extraction efficiency was measured for red light-emitting elements manufactured with different capping layer thicknesses. The results are shown in FIG. As is apparent from FIG. 7, the light extraction efficiency is highest when the thickness of the capping layer is 70 nm, which is 1.9 times that when there is no capping layer. In the case where the film thickness of the capping layer is 50 to 90 nm, the light extraction efficiency is improved by 1.6 times or more compared to the case where the capping layer is not provided, and when the film thickness of the capping layer is 60 nm to 80 nm. Was found to be significantly improved by 1.8 times or more.

  As described above, the light-emitting element, the light-emitting device including the light-emitting element, and the method for manufacturing the light-emitting element according to the present invention can stably form a film as a capping layer material at a not-so-high temperature, and And a capping layer made of a material having no absorption in each of the wavelength regions of red and red, it can be applied to a full-color display and is suitable for displaying a clear and bright image with good color purity.

It is a schematic sectional drawing which shows the structure of the light emitting element concerning embodiment of this invention. It is a diagram which shows the relationship between the wavelength in a capping layer using CBP, a refractive index, and an extinction coefficient. It is a schematic sectional side view which shows the light-emitting device concerning embodiment of this invention. It is a schematic sectional side view explaining the manufacturing method of the light-emitting device concerning embodiment of this invention. It is a schematic sectional side view explaining the manufacturing method of the light-emitting device concerning embodiment of this invention. It is a schematic sectional side view explaining the manufacturing method of the light-emitting device concerning embodiment of this invention. It is a diagram which shows the relationship between the thickness of the capping layer in an Example, and the extraction efficiency of light. Is a graph showing the relationship between the wavelength and the refractive index and the extinction coefficient of the capping layer using Alq ₃ in the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 10 Glass substrate 11 Anode (1st electrode)
12 hole transport layer 13 light emitting layer 14 electron transport layer 15, 15A-15C translucent cathode (second electrode)
16, 16A to 16C Capping layer 17 First layer, intermediate layer 18 Second layer 19A, 19B Evaporation mask 20 First light emitting element 30 Second light emitting element 40 Third light emitting element 50 Light emitting device

Claims (5)

A first electrode; an organic layer disposed above the first electrode and including a light emitting layer; a second electrode disposed on the organic layer and transmitting light from the light emitting layer; First to third light-emitting elements disposed on two electrodes, each having a capping layer made of a material having a refractive index larger than that of the constituent material of the second electrode and a band gap of 3.2 eV or more, are disposed on the substrate. A method of manufacturing a plurality of light emitting devices,
By laminating the constituent material of the capping layer on the second electrode corresponding to the first and second light emitting elements, an intermediate layer is formed on the second electrode corresponding to the first light emitting element. Forming the capping layer on the second electrode corresponding to two light emitting elements,
The second and third light emitting elements are formed by laminating the constituent material of the capping layer on the intermediate layer corresponding to the first light emitting element and on the second electrode corresponding to the third light emitting element, respectively. Forming the capping layer on the second electrode corresponding to the above, and thereby forming the capping layer of the first to third light emitting elements.   2. The light emitting device according to claim 1, wherein a sum of thicknesses of the capping layers corresponding to the second and third light emitting elements is substantially equal to a thickness of the capping layer corresponding to the first light emitting elements. Manufacturing method.   The first light emitting element emits light in red, the second light emitting element emits light in any one color of blue and green, and the third light emitting element emits light in any one color of blue and green, respectively. The manufacturing method of the light-emitting device of Claim 1 or Claim 2 to do. A first electrode; an organic layer disposed above the first electrode and including a light emitting layer; a second electrode disposed on the organic layer and transmitting light from the light emitting layer; A plurality of light-emitting elements that are disposed on two electrodes and have a capping layer made of a material having a refractive index larger than that of the constituent material of the second electrode and a band gap of 3.2 eV or more;
The plurality of light emitting elements are classified into a first light emitting element that emits red light, a second light emitting element that emits green light, and a third light emitting element that emits blue light.
The thickness d _R of the first capping layer of a light-emitting element, the thickness d _G of the capping layer of the second light emitting element, and the thickness d _B of the capping layer of the third light emitting element are different from each other A light emitting device characterized by the above. The film thickness d _{R of the} capping layer of the first light emitting element, the film thickness d _{G of the} capping layer of the second light emitting element, and the film thickness d _{B of the} capping layer of the third light emitting element are d _R > The light emitting device according to claim 4, wherein a relational expression of d _G > d _B is satisfied.

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