JP2019125616A - Display device and method for manufacturing display device - Google Patents

Abstract

To provide a high-definition display device with excellent color reproducibility and including a light-emitting element with excellent chromatic purity and light-emitting efficiency, and a method for manufacturing the display device.SOLUTION: A display device comprises a first pixel and a second pixel adjacent to the first pixel. The first pixel comprises a first pixel electrode, a first hole transport layer located on the first pixel electrode and extending over the first and second pixels, a first light-emitting layer on the first hole transport layer, and a counter electrode located on the first light-emitting layer and extending over the first and second pixels. The second pixel comprises a second pixel electrode, a first hole transport layer on the second pixel electrode, a second hole transport layer on the first hole transport layer, a second light-emitting layer on the second hole transport layer, and a counter electrode on the second light-emitting layer. A refractive index of the first hole transport layer is larger than a refractive index of the second hole transport layer. A light-emitting wavelength of the first light-emitting layer is shorter than a light-emitting wavelength of the second light-emitting layer.SELECTED DRAWING: Figure 3

Description

  One of the embodiments of the present invention relates to a display device having a light-emitting element and a method for manufacturing the same.

  As an example of the display device, an organic EL (Electroluminescence) display device can be mentioned. An organic EL display device has a plurality of organic light emitting elements (hereinafter referred to as light emitting elements) formed on a substrate, and each light emitting element includes an electroluminescent layer (hereinafter referred to as an organic compound) between a pair of electrodes (cathode and anode) , Described as an EL layer) as a basic structure. By applying a potential difference between the pair of electrodes, holes and electrons are respectively supplied from the anode and the cathode to the EL layer. The holes and electrons recombine in the EL layer to form an excited state of the organic compound. The function as a light emitting element is expressed by utilizing light emission when the excited state is radiatively deactivated to the ground state.

  The efficiency and the emission color of the light emitting element are controlled by the structure of the EL layer and the light emitting material contained in the EL layer. For example, light emission of various colors can be obtained by appropriately selecting a light-emitting material. In addition, by utilizing the interference effect of light inside or outside the light emitting element, the emission intensity in the front direction can be increased and the emission spectrum can be narrowed. For example, Patent Document 1 discloses that the thickness of the hole transport layer included in the EL layer is adjusted for each light emitting element having different emission wavelengths, and thereby the resonant structure formed by the EL layer and the pair of electrodes is controlled. ing. By this method, optimization of emission intensity and emission color is performed for each light emitting element.

JP, 2000-323277, A

  An object of one embodiment of the present invention is to provide a high-definition display device including a light-emitting element excellent in color purity and luminous efficiency and excellent in color reproducibility, and a method for manufacturing the display device. Do.

  One of the embodiments of the present invention is a display device. The display device has a first pixel and a second pixel adjacent to the first pixel. The first pixel is located on the first pixel electrode, the first pixel electrode, and extends over the first pixel and the second pixel on the first hole transport layer, the first hole transport layer. A first light emitting layer, and a counter electrode located on the first light emitting layer and extending over the first pixel and the second pixel. The second pixel includes a second pixel electrode, a first hole transport layer on the second pixel electrode, a second hole transport layer on the first hole transport layer, and a second hole transport layer on the second hole transport layer. And a counter electrode on the second light emitting layer. The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer, and the emission wavelength of the first light emitting layer is shorter than the emission wavelength of the second light emitting layer.

  One of the embodiments of the present invention is a method for manufacturing a display device. In this manufacturing method, a first pixel electrode and a second pixel electrode adjacent to the first pixel electrode are formed, and a first hole transport is performed so as to cover the first pixel electrode and the second pixel electrode. Forming a layer, forming a second hole transport layer on the first hole transport layer to cover the second pixel electrode and expose the first hole transport layer on the first pixel electrode Forming a first light emitting layer on the first pixel electrode via the first hole transport layer, and forming a second pixel electrode via the first hole transport layer and the second hole transport layer. Forming a second light emitting layer thereon, and forming a counter electrode on the first light emitting layer and the second light emitting layer. The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer, and the emission wavelength of the first light emitting layer is shorter than the emission wavelength of the second light emitting layer.

  One of the embodiments of the present invention is a method for manufacturing a display device. In this manufacturing method, a first pixel electrode, a second pixel electrode adjacent to the first pixel electrode, and a third pixel electrode adjacent to the second pixel electrode are formed, the first pixel electrode, Forming a first hole transport layer so as to cover the second pixel electrode and the third pixel electrode; covering the second pixel electrode; and on the first pixel electrode and the third pixel electrode Forming a second hole transport layer on the first hole transport layer so that the first hole transport layer is exposed; covering a third pixel electrode; and forming a first hole transport layer on the first pixel electrode Forming a third hole transport layer on the first hole transport layer such that the hole transport layer is exposed and the second hole transport layer is exposed on the second pixel electrode; first hole transport layer Forming a first light emitting layer on the first pixel electrode via the first hole transporting layer and the second hole transporting layer; Forming a second light emitting layer on the second pixel electrode via the transport layer; and forming a third light emitting layer on the third pixel electrode via the first hole transport layer and the third hole transport layer And forming a counter electrode on the first light emitting layer, the second light emitting layer, and the third light emitting layer. The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer and the refractive index of the third hole transport layer, and the emission wavelength of the second light emitting layer is that of the first light emitting layer. It is longer than the emission wavelength and shorter than the emission wavelength of the third light emitting layer.

  One of the embodiments of the present invention is a method for manufacturing a display device. In this manufacturing method, a first pixel electrode, a second pixel electrode adjacent to the first pixel electrode, and a third pixel electrode adjacent to the second pixel electrode are formed, the first pixel electrode, Forming a first hole transport layer so as to cover the second pixel electrode and the third pixel electrode; covering the second pixel electrode and the third pixel electrode; and on the first pixel electrode Forming a second hole transport layer on the first hole transport layer so that the first hole transport layer is exposed; covering a third pixel electrode; and forming a first hole transport layer on the first pixel electrode Forming a third hole transport layer on the second hole transport layer such that the hole transport layer is exposed and the second hole transport layer is exposed on the second pixel electrode; first hole transport layer Forming a first light emitting layer on the first pixel electrode via the first hole transporting layer and the second hole transporting layer; Forming a second light emitting layer on the second pixel electrode via the transport layer; and forming a third pixel via the first hole transport layer, the second hole transport layer, and the third hole transport layer. Forming a third light emitting layer on the electrode; and forming a counter electrode on the first light emitting layer, the second light emitting layer, and the third light emitting layer. The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer and the refractive index of the third hole transport layer, and the emission wavelength of the second light emitting layer is that of the first light emitting layer. It is longer than the emission wavelength and shorter than the emission wavelength of the third light emitting layer.

  One of the embodiments of the present invention is a method for manufacturing a display device. In this manufacturing method, a first pixel electrode, a second pixel electrode adjacent to the first pixel electrode, and a third pixel electrode adjacent to the second pixel electrode are formed, the first pixel electrode, Forming a first hole transport layer so as to cover the second pixel electrode and the third pixel electrode; forming a first light emitting layer on the first pixel electrode via the first hole transport layer Forming the second hole transport layer and the second light emitting layer sequentially on the first hole transport layer so as to selectively cover the second pixel electrode, and selecting the third pixel electrode Forming a third hole transport layer and a third light emitting layer on the first hole transport layer so as to cover the first light emitting layer, and the second light emitting layer and the third light emitting layer Forming a counter electrode. The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer and the refractive index of the third hole transport layer, and the emission wavelength of the second light emitting layer is that of the first light emitting layer. It is longer than the emission wavelength and shorter than the emission wavelength of the third light emitting layer.

The upper surface schematic diagram of the display apparatus which concerns on embodiment of this invention. The cross-sectional schematic diagram of the display element of the display apparatus which concerns on embodiment of this invention. The cross-sectional schematic diagram of the display element of the display apparatus which concerns on embodiment of this invention. The cross-sectional schematic diagram of the display element of the display apparatus which concerns on embodiment of this invention. The cross-sectional schematic diagram of the display element of the display apparatus which concerns on embodiment of this invention. 6 illustrates an example of an equivalent circuit of a pixel of a display device according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of a display device according to an embodiment of the present invention. FIGS. 5A to 5D are schematic cross-sectional views illustrating a method of manufacturing a display device according to an embodiment of the present invention. FIGS. FIGS. 5A to 5D are schematic cross-sectional views illustrating a method of manufacturing a display device according to an embodiment of the present invention. FIGS. FIGS. 5A to 5D are schematic cross-sectional views illustrating a method of manufacturing a display device according to an embodiment of the present invention. FIGS. FIGS. 5A to 5D are schematic cross-sectional views illustrating a method of manufacturing a display device according to an embodiment of the present invention. FIGS.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in various modes without departing from the scope of the present invention, and the present invention is not interpreted as being limited to the description of the embodiments exemplified below.

  Although the drawings may be schematically represented with respect to the width, thickness, shape, etc. of each part in comparison with the actual embodiment in order to clarify the explanation, the drawings are merely an example, and the interpretation of the present invention is limited. It is not something to do. In the present specification and the drawings, elements having the same functions as those described with reference to the drawings in the drawings may be denoted by the same reference numerals, and overlapping descriptions may be omitted.

  In the present invention, when a plurality of films are formed by performing etching or light irradiation on a certain film, the plurality of films may have different functions and roles. However, the plurality of films are derived from the film formed as the same layer in the same step, and have the same layer structure and the same material. Therefore, these multiple films are defined as existing in the same layer.

  In the present specification and claims, when expressing an aspect in which another structure is disposed on a certain structure, in the case where it is simply referred to as “above”, in a certain structure, unless otherwise specified. It includes both the case where another structure is arranged immediately above and the case where another structure is arranged above another structure via another structure so as to be in contact with each other.

  In the present specification and claims, the expression "a certain structure is exposed from another structure" means an aspect in which a part of a certain structure is not covered by another structure. The part not covered by the structure also includes the aspect covered by another structure.

First Embodiment
In this embodiment, a structure of a display device 100 which is one of the embodiments of the present invention and a light emitting element 105 included in the display device 100 will be described.

[1. Overall structure]
A schematic top view of the display device 100 is shown in FIG. The display device 100 has a substrate 102, and has various insulating films, semiconductor films, and conductive films patterned thereon. The insulating film, the semiconductor film, and the conductive film form a driver circuit (a scan line driver circuit 108 and a signal line driver circuit 110) for driving the plurality of pixels 104 and the pixels 104. A plurality of pixels 104 define a display area 106. As described later, the light emitting element 105 is disposed in each pixel 104.

  The scanning line side drive circuit 108 and the signal line side drive circuit 110 are arranged outside the display area 106 (peripheral area or frame area). Various wirings 112 formed of a conductive film patterned from the display region 106, the scanning line driver circuit 108, and the signal line driver circuit 110 extend to one side of the substrate 102, and the wirings 112 are in the vicinity of the edge of the substrate 102. Exposed to form a terminal (not shown). These terminals are electrically connected to the flexible printed circuit board (FPC) 114. In the example shown here, a driving IC 116 having an integrated circuit formed on a semiconductor substrate is further mounted on the FPC 114. Video signals and power are supplied from an external circuit (not shown) through the driver IC 116 and the FPC 114, and the video signals and power are supplied to the display region 106, the scan line driver circuit 108, and the signal line driver circuit 110 through the wiring 112. . The mode of the drive circuit and the drive IC 116 is not limited to that shown in FIG. 1. For example, the drive IC 116 may be mounted on the substrate 102, or the function of the signal line side drive circuit 110 may be integrated into the drive IC 116. good.

[2. Structure of light emitting element]
The display device 100 is provided with a plurality of light emitting elements 105 giving different emission colors, and any one of the light emitting elements 105 is disposed in each pixel 104. As shown in FIG. 2A, for example, in each pixel, any of the light-emitting elements 105 which emit blue light, green light, and red light is provided. By controlling the plurality of light emitting elements 105 which emit light of three primary colors in this manner, full color display can be performed. There is no restriction on the emission color of the light emitting element 105, and for example, a light emitting element which emits white light may be further provided.

  FIG. 2A shows a first light-emitting element 105 a and a second light-emitting element 105 which give different emission colors to three adjacent pixels (hereinafter, the first pixel 104 a, the second pixel 104 b, and the third pixel 104 c). An example in which the light emitting element 105 b and the third light emitting element 105 c are arranged is shown. Here, the cross-sectional structure of the light emitting element 105 is schematically shown. In the example shown here, the emission wavelength of the second light emitting element 105 b is longer than that of the first light emitting element 105 a and shorter than that of the third light emitting element 105 c. For example, the first light emitting element 105a, the second light emitting element 105b, and the third light emitting element 105c can be configured to emit blue light, green light, and red light, respectively. In this specification, blue emission is emission having an emission peak wavelength in the range of 400 nm to 500 nm, green emission is emission having an emission peak wavelength in the range of 500 nm to 600 nm, and red emission is 600 nm. It is light emission which has a light emission peak wavelength in the range of 780 nm or less.

  Each light emitting element 105 includes a pixel electrode 120. Here, for the sake of convenience, the pixel electrodes of the first light emitting element 105a, the second light emitting element 105b, and the third light emitting element 105c are the first pixel electrode 120a, the second pixel electrode 120b, and the third pixel electrode 120c, respectively. Call. The pixel electrode 120 can function as an anode or a cathode, but in the following description, the pixel electrode 120 functions as an anode. The pixel 104 is configured such that a potential is independently supplied to the first pixel electrode 120a, the second pixel electrode 120b, and the third pixel electrode 120c.

  Each light emitting element 105 includes an opposite electrode 138 overlapping with the pixel electrode 120. The counter electrode 138 can also function as an anode or a cathode, but in the following description, the case where the counter electrode 138 functions as a cathode will be described. The counter electrode 138 extends over the first pixel 104a, the second pixel 104b, and the third pixel 104c. That is, the counter electrode 138 is continuously provided over the first pixel 104a, the second pixel 104b, and the third pixel 104c, and is shared by these pixels. Therefore, the same potential is applied to the counter electrode 138 in the plurality of pixels 104. In each pixel 104, various functional layers are provided between the pixel electrode 120 and the counter electrode 138, and holes and electrons are respectively injected from the pixel electrode 120 and the counter electrode 138 to the functional layer. In the present specification and claims, the EL layer refers to the entire functional layer sandwiched between the pixel electrode 120 and the counter electrode 138.

  As shown in FIG. 2A, the first hole transport layer 124 and the first light emitting layer 128 a over the first hole transport layer 124 are provided in the first pixel 104 a. That is, one hole transport layer is provided in the first pixel 104a. As an optional configuration, the first pixel 104a has a hole injection layer 122 in contact with the first pixel electrode 120a, an electron transport layer 132 on the first light emitting layer 128a, and an electron injection layer 134 on the electron transport layer 132. You may In the first pixel 104 a, a hole blocking layer 130 may be further provided between the first light emitting layer 128 a and the electron transporting layer 132.

  On the other hand, two stacked hole transport layers are disposed in the second pixel 104b. Specifically, in the second pixel 104 b, in addition to the first hole transport layer 124, the second hole transport layer 126 b in contact with the first hole transport layer 124 is provided on the first hole transport layer 124. The second light emitting layer 128 b is formed thereon. Similar to the first pixel 104 a, the hole injection layer 122, the electron transport layer 132, the electron injection layer 134, the hole blocking layer 130, and the like may be provided as an optional configuration for the second pixel 104 b.

Similar to the second pixel 104b, the third pixel 104c is also formed with a plurality of hole transport layers. That is, the third hole transport layer 126c is disposed on the first hole transport layer 124 so as to be in contact with the first hole transport layer 124, and the third light emitting layer 128c is provided thereon. The thickness T ₃ of the third hole transport layer 126c is greater than the thickness T ₂ of the second hole transport layer 126 _b. Similar to the first pixel 104a, the hole injection layer 122, the electron transport layer 132, the electron injection layer 134, the hole blocking layer 130, and the like may be formed as an optional configuration for the third pixel 104c.

  Thus, the second hole transport layer 126b is selectively disposed in the second pixel 104b without providing the second hole transport layer 126b and the third hole transport layer 126c in the first pixel 104a. , And the third hole transport layer 126c may be selectively disposed in the third pixel 104c. In this case, the second hole transport layer 126b and the third hole transport layer 126c are confined in the second pixel 104b and the third pixel 104c, respectively. Therefore, in the example shown in FIG. 2A, in the first light emitting element 105a, the first hole transport layer 124 and the first light emitting layer 128a are in contact with each other on the first pixel electrode 120a. The light emitting layer 128 b and the third light emitting layer 128 c are provided on the first hole transport layer 124 via the second hole transport layer 126 b and the third hole transport layer 126 c, respectively.

  However, the structure of the light emitting element 105 is not limited to this, and for example, the electron blocking layer 136 may be provided on the first hole transport layer 124. That is, as shown in FIG. 2B, in the first pixel 104a, the electron blocking layer 136 can be provided between the first hole transporting layer 124 and the first light emitting layer 128a so as to be in contact with these. In this case, the electron blocking layer 136 is provided between the second hole transport layer 126b and the second light emitting layer 128b in the second pixel 104b, and the third hole transport layer 126c and the third pixel in the third pixel 104c. The electron blocking layer 136 is provided between the light emitting layers 128c.

  Alternatively, as shown in FIG. 2C, a configuration without the hole blocking layer 130 may be employed. In this case, in each pixel 104, the light emitting layer 128 and the electron transport layer 132 are in contact with each other.

  A schematic cross-sectional view of the display device 100 including the structure between the pixels 104 is shown in FIG. Although the structure of the light emitting element 105 shown in FIG. 3A corresponds to that of FIG. 2A, the electron injecting layer 134 is not shown here for easy viewing. As shown in FIG. 3A, the pixel electrode 120 is provided on the insulating surface 142. The insulating surface 142 is, for example, a surface constituted by the substrate 102 and an insulating film provided on the substrate 102. A partition wall 140 is provided between adjacent pixel electrodes 120. The partition wall 140 is an insulating film, and has a function of insulating between adjacent pixel electrodes 120 and relaxing unevenness due to an end portion of the pixel electrode 120.

  The hole injection layer 122 and the first hole transport layer 124 can be continuously provided over the first pixel electrode 120 a, the second pixel 104 b, and the third pixel 104 c. Therefore, the hole injection layer 122 and the first hole transport layer 124 also cover the upper surface of the partition wall 140, and are shared by the first pixel electrode 120a, the second pixel 104b, and the third pixel 104c. Similarly, the hole blocking layer 130, the electron transport layer 132, the electron injection layer 134, and the counter electrode 138 can be continuously provided over the first pixel electrode 120a, the second pixel 104b, and the third pixel 104c. Therefore, these are also shared by the first pixel electrode 120a, the second pixel 104b, and the third pixel 104c. When the electronic block layer 136 is provided, as shown in FIG. 3B, the electronic block layer 136 is continuously provided over the first pixel electrode 120a, the second pixel 104b, and the third pixel 104c.

  On the other hand, as described above, the second hole transport layer 126b and the third hole transport layer 126c can be selectively formed in the second pixel 104b and the third pixel 104c, respectively. In this case, the second hole transport layer 126 b and the third hole transport layer 126 c are not included in the first pixel 104 a. In addition, the second hole transport layer 126b is not included in the first pixel 104a or the third pixel 104c, and the third hole transport layer 126c is not included in the first pixel 104a or the second pixel 104b. Similarly, each light emitting layer 128 is also selectively formed in the corresponding pixel 104. In the first pixel 104 a, the first light emitting layer 128 a overlaps with the first pixel electrode 120 a through the first hole transport layer 124. In the second pixel 104b, the second light emitting layer 128b overlaps the second pixel electrode 120b via the first hole transport layer 124 and the second hole transport layer 126b. In the third pixel 104c, the third light emitting layer 128c overlaps the third pixel electrode 120c through the first hole transport layer 124 and the third hole transport layer 126c.

  Alternatively, as shown in FIG. 4, although the second hole transport layer 126b is not disposed in the first pixel 104a, it may be provided to extend over the second pixel 104b and the third pixel 104c. . In this case, the second hole transport layer 126b is shared by the second pixel 104b and the third pixel 104c, and the third hole transport layer 126c in the third pixel 104c is replaced with the first hole transport layer 124 and the first hole transport layer 124. It overlaps with the third pixel electrode 120c through the second hole transport layer 126b.

[3. material]
3-1. Pixel Electrode The pixel electrode 120 is an electrode provided to inject holes in the EL layer, and it is preferable that the surface thereof has a relatively high work function. Specific materials include conductive oxides capable of transmitting visible light such as indium-tin oxide (ITO) and indium-zinc oxide (IZO), and these may further contain silicon. Good. With this structure, light emission obtained from the light emitting layer 128 can be extracted through the pixel electrode 120. On the other hand, when light emitted from the light emitting layer 128 is extracted through the counter electrode 138, the pixel electrode 120 may further include a film containing a metal having a high visible light reflectance, such as silver or aluminum. For example, the pixel electrode 120 has a structure in which a first conductive film containing a conductive oxide, a second conductive film containing a metal such as silver and aluminum, and a third conductive film containing a conductive oxide are stacked in this order. You can have
3-2. Hole Injection Layer The hole injection layer 122 can use a compound (electron donating compound) in which holes are easily injected from the pixel electrode 120, that is, easily oxidized. In other words, a compound having a shallowest occupied molecular orbital (HOMO) level can be used. For example, aromatic amines such as benzidine derivatives and triarylamines, carbazole derivatives, thiophene derivatives, and phthalocyanine derivatives such as copper phthalocyanine can be used. Alternatively, polythiophene or a polyaniline derivative can be used, and as an example, poly (2,3-ethylenedioxythiophene) / poly (styrenesulfonic acid) can be mentioned. Alternatively, a mixture of an electron donor and an electron donor such as the above-mentioned aromatic amine or carbazole derivative or an aromatic hydrocarbon may be used. Examples of the electron acceptor include transition metal oxides such as vanadium oxide and molybdenum oxide, nitrogen-containing heteroaromatic compounds, heteroaromatic compounds having a strong electron-withdrawing group such as cyano group, and the like. Since these materials and mixtures have small ionization potentials, the hole injection barrier from the pixel electrode 120 is small, which contributes to the reduction of the driving voltage of the display device 100.

3-3. Hole Transport Layer The first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c have a function of transporting the holes injected into the hole injection layer 122 to the light emitting layer 128 side. For these transport layers, materials similar to or similar to the materials usable for the hole injection layer 122 can be used. For example, a material whose HOMO level is deep compared to the hole injection layer 122 but whose difference is approximately 0.5 eV, 0.3 eV, or less can be used. Since the above-described material has a hole transportability higher than the electron transportability, holes can be efficiently transported to the light emitting layer 128 side, which enables the display device 100 to be driven at a low voltage.

  Here, the material is selected such that the refractive index of the material used for the first hole transport layer 124 is larger than the refractive index of the material used for the second hole transport layer 126 b and the third hole transport layer 126 c. Be done. More specifically, the difference between the refractive index of the material used for the first hole transport layer 124 and the refractive index of the material used for the second hole transport layer 126 b and the third hole transport layer 126 c is 0.05 or more The material is selected so as to be 0.3 or less, 0.1 or more and 0.2 or less, or 0.1 or more and 0.15 or less. The materials used for the second hole transport layer 126 b and the third hole transport layer 126 c may have the same or different refractive index. Alternatively, the materials used for the second hole transport layer 126b and the third hole transport layer 126c may be the same.

  At the same time, the material of the material used for the first hole transport layer 124 is smaller than the hole mobility of the material used for the second hole transport layer 126 b and the third hole transport layer 126 c. It is selected. More specifically, the hole mobility of the material used for the second hole transport layer 126 b and the third hole transport layer 126 c is twice or more the hole mobility of the material used for the first hole transport layer 124. The material is selected so as to be 100 times or less, 5 times or more and 50 times or less, or 10 times or more and 25 times or less.

  Further, it is preferable that molecules of the material used for the first hole transport layer 124 or molecules of the material contained be oriented in the horizontal direction or in the direction parallel to the main surface of the substrate 102. When the molecule of the material used for the first hole transport layer 124 is a rod-like molecule, it is desirable that the major axis of the molecule is oriented in the horizontal direction or in the direction parallel to the main surface of the substrate 102. Note that the direction in which the molecules are aligned may be a substantially horizontal direction or a direction substantially parallel to the main surface of the substrate 102. When the long axis of the molecule of the material used for the first hole transport layer 124 is oriented in the above direction, it is in the horizontal direction or on the main surface of the substrate 102 as compared with the case where it is oriented in the random direction. The refractive index of the first hole transport layer 124 in the parallel direction is increased. In addition, the mobility of the first hole transport layer 124 in the horizontal direction or in the direction parallel to the main surface of the substrate 102 is reduced. Therefore, in the first hole transport layer 124, the number of molecules oriented substantially horizontally or in a direction substantially parallel to the main surface of the substrate 102 may be larger than the number of molecules oriented in the other direction. .

3-4. Light-Emitting Layer The light-emitting layer 128 is a layer that provides a space where holes and electrons recombine, and light is emitted from the light-emitting material contained in this layer. The light emitting layer 128 may be formed of a single compound, or may have a so-called host-guest configuration. In the case of the host-guest type, the host material includes, for example, fused aromatic compounds such as stilbene derivatives and anthracene derivatives, carbazole derivatives, metal complexes containing quinolinol ligands, nitrogen-containing heteroaromatics such as aromatic amines and phenanthroline derivatives A compound etc. can be used. The guest functions as a light-emitting material, and a fluorescent material such as coumarin derivative, pyran derivative, quinocridone derivative, tetracene derivative, pyrene derivative, anthracene derivative, or a phosphorescent material such as an iridium-based ortho metal complex can be used as the guest. When the light emitting layer 128 is formed of a single compound, the above-described host material can be used. In this case, the host material acts as a light emitting material.

  In the display device 100 according to this embodiment, the light emitting layer 128 is configured such that the emission wavelength of the second light emitting element 105 b is longer than the emission wavelength of the first light emitting element 105 a and shorter than the emission wavelength of the third light emitting element 105 c. The material of is selected. For example, the light emitting material of the first light emitting layer 128a gives a light emission peak in the range of 400 nm to 500 nm, and the light emitting material of the second light emitting layer 128b gives a light emission peak in the range of 500 nm to 600 nm, and the third light emission The light emitting material is selected such that the light emitting material of the layer 128c has a light emission peak in the range of 600 nm to 780 nm.

3-5. Hole Blocking Layer The hole blocking layer 130 prevents holes injected from the pixel electrode 120 from being injected into the electron transport layer 132 through the light emitting layer 128 without contributing to recombination, thereby causing holes to be emitted to the light emitting layer 128. In addition to being confined inside, it has a function of preventing energy transfer of excitation energy obtained in the light emitting layer 128 to molecules in the electron transport layer 132. Thereby, the fall of luminous efficiency can be prevented.

  For the hole blocking layer 130, it is preferable to use a material having electron transportability higher than or the same degree as hole transportability, and having a deeper HOMO level and a larger band gap than the molecules in the light emitting layer 128. Specifically, the difference between the HOMO level of the molecule contained in the hole blocking layer 130 and that of the molecule contained in the light emitting layer 128 is preferably 0.2 eV, 0.3 eV, or 0.5 eV or more. The difference between the band gap of the molecules contained in the hole blocking layer 130 and that of the molecules contained in the light emitting layer 128 is preferably 0.2 eV, 0.3 eV, or 0.5 eV or more. When the light emitting material is a phosphorescent material, it is preferable to use a material having a triplet level higher than that of the light emitting material by 0.2 eV, 0.3 eV, or 0.5 eV or more. More specifically, phenanthroline derivatives, oxadiazole derivatives, triazole derivatives, bis (2-methyl-8-quinolinolato) (4-hydroxy-biphenylyl) aluminum, etc., relatively large band gap (eg, 2.8 eV or more) Metal complexes and the like can be mentioned.

3-6. Electron blocking layer The electron blocking layer 136 passes through the light emitting layer 128 without the electrons injected from the counter electrode 138 contributing to recombination, and passes through the first hole transport layer 124, the second hole transport layer 126b, and the third. The holes are confined in the light emitting layer 128 by preventing the holes from being injected into the hole transporting layer 126c, and the excitation energy obtained in the light emitting layer 128 has a function of preventing energy transfer to the molecules of the hole transporting layer. Thereby, the fall of luminous efficiency can be prevented.

  A material having a hole transportability higher than or the same degree as the electron transportability in the electron block layer 136, and a minimum unoccupied molecular orbital (LUMO) level shallower than the molecules in the light emitting layer 128 and a large band gap It is preferable to use Specifically, the difference between the LUMO level of the molecule contained in the electron blocking layer 136 and that of the molecule contained in the light emitting layer 128 is preferably 0.2 eV, 0.3 eV, or 0.5 eV or more. The difference between the band gap of the molecules contained in the electron blocking layer 136 and that of the molecules contained in the light emitting layer 128 is preferably 0.2 eV, 0.3 eV, or 0.5 eV or more. When the light emitting material is a phosphorescent material, it is preferable to use a material having a triplet level higher than that of the light emitting material by 0.2 eV, 0.3 eV, or 0.5 eV or more. More specifically, aromatic amine derivatives, carbazole derivatives, 9,10-dihydroacridine derivatives, benzofuran derivatives, benzothiophene derivatives and the like can be mentioned.

3-7. Electron Transport Layer The electron transport layer 132 has a function of transporting the electrons injected from the counter electrode 138 to the electron injection layer 134 to the light emitting layer 128 side. The electron transporting layer 132 contains a compound (electron transporting compound) having an electron transporting property higher than the hole transporting property, and as such a compound, aluminum complex, lithium complex, metal complex such as beryllium, oxadiazole derivative, triazole Specific examples thereof include fused aromatic compounds such as derivatives, silacyclopentadiene derivatives, anthracene derivatives, pyrene derivatives and perylene derivatives, and nitrogen-containing fused heteroaromatic compounds such as phenanthroline derivatives. Examples of the metal complex include metal complexes having an 8-quinolinol ligand such as 8-quinolinolato lithium (Liq), tris (8-quinolinolato) aluminum (Alq), and bis (8-quinolinolato) beryllium. Be done. These compounds may have a substituent, and examples of the substituent include an alkyl group having 1 to 4 carbon atoms, and an aryl group such as a phenyl group or a naphthyl group.

3-8. Electron Injection Layer The electron injection layer 134 has a function of promoting electron injection from the counter electrode 138. Examples of the material that can be used for the electron injection layer 134 include inorganic compounds such as lithium fluoride and calcium fluoride. Alternatively, an electron-transporting compound exemplified by an electron-transporting compound which can be used for the electron-transporting layer 132, a group 1 metal such as lithium or the like, magnesium, a group 2 metal such as magnesium or calcium, or a lanthanoid metal such as ytterbium Mixtures with compounds can be used. Typically, a mixture of Alq and Li or a mixture of Liq and Li can be mentioned. Since the anion radical of the electron transporting compound is present in the mixed layer of the electron transporting compound and the electron donating compound, the density of electrons as a carrier is high. Therefore, the electron transporting property of the electron transporting layer 132 is increased, and electrons injected from the counter electrode 138 can be efficiently transported to the light emitting layer 128, and as a result, the driving voltage of the display device 100 is reduced.

3-9. Counter electrode The counter electrode 138 has a function of injecting electrons into the EL layer. At the same time, when light emitted from the light emitting layer 128 is extracted from the pixel electrode 120, it serves as a reflective electrode, and when light emitted is extracted from the counter electrode 138, a light extraction electrode that reflects part of the light and transmits part of it. Act as. When the counter electrode 138 is used as a reflective electrode, a film containing a metal such as aluminum, magnesium, silver or an alloy thereof and having a thickness that efficiently reflects visible light is used as the counter electrode 138. On the other hand, in the case where the counter electrode 138 is a light extraction electrode, the counter electrode 138 is configured to include a light transmitting conductive oxide such as ITO or IZO. Alternatively, a metal film containing the above-described metal and having such a thickness as to transmit visible light may be used. In this case, a stacked body in which a light-transmitting conductive oxide is further stacked may be used.

[4. Optical design]
In the display device 100, light emission efficiency can be increased and color purity of light emission can be improved by performing appropriate optical design on the EL layer. As described above, when light emitted from the light emitting layer 128 is extracted from the counter electrode 138 (top emission), the pixel electrode 120 functions as a reflective electrode, and the counter electrode 138 reflects a part of the light emitted from the light emitting layer 128, Partially transparent. On the other hand, when light emitted from the light emitting layer 128 is extracted from the pixel electrode 120 (bottom emission), the pixel electrode 120 transmits visible light, and the counter electrode 138 functions as a reflective electrode. Therefore, in any case, a microresonator is formed between the pixel electrode 120 and the reflective surface of the counter electrode 138, and the light generated by the light emitting layer 128 interferes. Here, in the description, it is assumed that the top surface of the pixel electrode 120 and the bottom surface of the counter electrode 138 shown in FIG. 1 are reflection surfaces, and a microresonator is formed therebetween.

  The interference effect of light in the microresonator depends on the optical distance between the top surface of the pixel electrode 120 and the bottom surface of the counter electrode 138 and the spectrum of light emission from the light emitting layer 128. This optical distance is the sum of the product of the refractive index and thickness of each functional layer. In the case of the top emission, the light emitting center of the light emitting layer 128 and the pixel electrode 120 in the case of the bottom emission so that the optical distance coincides with an odd multiple of one quarter (λ / 4) of the target light emission wavelength. By adjusting the EL layer so that the optical distance between the upper surfaces of the upper and lower surfaces coincides with an integral multiple of half (λ / 2) of the target light emission wavelength, the light interferes so that the light emission is enhanced. Thereby, the emission intensity of the light emitting layer 128 is increased, and the emission spectrum is narrowed.

  In the display device 100, the thickness and refractive index of the hole transport layer of each light emitting element 105, that is, the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c are controlled to control the optical Adjustment of distance can be easily performed. For example, in the first light emitting element 105a, optical adjustment is performed by controlling the thickness and the refractive index of the first hole transport layer 124. Since the second light emitting layer 128 b emits light to the longer wavelength side than the first light emitting layer 128 a, the optical distance is longer in the second light emitting element 105 b than in the first light emitting element 105 a. Therefore, in the second light emitting element 105b, optical adjustment is performed by adjusting the thickness and refractive index of the second hole transport layer 126b in addition to the first hole transport layer 124. Similarly, since the third light emitting layer 128c emits light to the longer wavelength side than the second light emitting layer 128b, the optical distance of the third light emitting element 105c is longer than that of the second light emitting element 105b. Therefore, in the third light emitting element 105c, not only the first hole transport layer 124 but also the third hole transport layer 126c having a thickness larger than that of the second hole transport layer 126b is disposed, Optical adjustment is performed by adjusting the thickness of the third hole transport layer 126c.

  As described above, the refractive index of the material used for the first hole transport layer 124 is greater than the refractive index of the material used for the second hole transport layer 126 b and the third hole transport layer 126 c. Materials of the hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c are selected. For this reason, the refractive index of the first hole transport layer 124 is larger than the refractive index of the second hole transport layer 126 b and the third hole transport layer 126 c. Since the optical distance of the film is the product of the refractive index and the thickness, each light emitting element 105 can be formed by forming the first hole transport layer 124 so as to be shared by the first pixel 104 a to the third pixel 104 c. Large optical distances can be obtained. That is, since the amount of material used for the first hole transport layer 124 can be reduced, the display device 100 can be manufactured at low cost.

  On the other hand, the refractive index of the second hole transport layer 126 b and the third hole transport layer 126 c is smaller than that of the first hole transport layer 124. For this reason, the variation in the thickness of the second hole transport layer 126 b and the third hole transport layer 126 c is less likely to affect the optical distance more than the variation in the thickness of the first hole transport layer 124. Although the variation of the optical distance modulates the brightness of each light emitting element by modulating the optical cavity effect, what is particularly problematic for the display device is the change of the white chromaticity due to the modulation of the relative brightness among the light emitting elements. The variation of the optical distance of the first hole transport layer 124 changes the optical chromaticity of the first light emitting element 105a, the second light emitting element 105b, and the third light emitting element 105c at the same time, so the change of the white chromaticity is It is hard to occur. On the other hand, variations in thickness of the second hole transport layer 126 b and the third hole transport layer 126 c easily change the white chromaticity because they change the optical distance of any one light emitting element. Therefore, in the present embodiment, by making the refractive index of the second hole transport layer 126 b and the third hole transport layer 126 c smaller than that of the first hole transport layer 124, the thickness of the hole transport layer on the process can be increased. By making the change of the white chromaticity less likely to occur due to the variation, the manufacturing yield of the display can be improved, and the display device 100 can be provided at lower cost.

  Furthermore, in the display device 100, as described above, the hole mobility of the material used for the first hole transport layer 124 is the hole migration of the material used for the second hole transport layer 126b and the third hole transport layer 126c. The materials of the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c are selected so as to be smaller than zero. Thus, the hole mobility of the first hole transport layer 124 is smaller than the hole mobility of the second hole transport layer 126 b and the third hole transport layer 126 c. By adopting such a configuration, color mixing due to so-called crosstalk can be prevented, and a display device excellent in color reproducibility can be provided. A more detailed description will be made using FIG.

  When driving the display device 100, the pixels 104 are controlled independently. Specifically, while the display device 100 is driven, a constant potential is applied to the counter electrode 138 shared by the plurality of pixels 104. On the other hand, in the selected pixel 104 (for example, the first pixel 104a in FIG. 5), a potential corresponding to the video signal is applied to the pixel electrode 120 (in FIG. 5, the first pixel electrode 120a). When the potential difference between the first pixel electrode 120a and the counter electrode 138 exceeds the threshold of the first light emitting element 105a, holes are injected from the first pixel electrode 120a and electrons are injected to the EL layer from the counter electrode 138a. (See arrows 144, 145). By transporting the injected holes and electrons into the EL layer, current flows in the EL layer. The current flowing here is called a space charge limited current, and flows from the first pixel electrode 120a toward the counter electrode 138 in a direction perpendicular to the surface of the first pixel electrode 120a. The injected holes and electrons recombine in the first light emitting layer 128a, resulting in light emission.

  The magnitude of the space charge limited current is inversely proportional to the cube of the film thickness (here, the thickness of the EL layer). Therefore, the space charge limited current can not flow in the EL layer in a direction parallel to the surface of the pixel electrode 120, and the ohmic law is applied to the current flowing in this direction. Each of the layers constituting the EL layer usually has conductivity enough to be regarded as an insulating film. Therefore, in the EL layer, usually, the ohmic current flowing in the direction parallel to the surface of the pixel electrode 120 can be ignored, and the injected holes and electrons are not transported to the adjacent pixel, and thus selected. Light emission selectively occurs in the pixel 104.

  However, if the conductivity of all or part of the layers constituting the EL layer is increased, the ohmic current can not be ignored. In particular, in the case where the width of the partition wall 140 is reduced to reduce the distance between adjacent pixels 104 in order to achieve high definition of the display device, the influence of the ohmic current can not be ignored. In the display device 100, as described above, the first hole transport layer 124 is continuously disposed from the first pixel 104a to the third pixel 104c. Therefore, when the hole transportability of the first hole transport layer 124 is high, some of the holes injected from the first pixel electrode 120 a are adjacent via the inside of the first hole transport layer 124 on the partition wall 140. It is transported to the light emitting element (the second light emitting element 105 b in the example of FIG. 5) (see the arrow 146). As a result, even when only the first pixel 104a is selected, holes are transported to the adjacent second pixel 104b, and recombine with electrons (arrow 147) injected from the counter electrode 138 to generate a second light emission. The layer 128 b emits light. This phenomenon is crosstalk, and light emission from pixels 104 other than the selected pixel 104 is mixed, so that the outline of the image is blurred or the color purity of the light emission color is lowered, and the color gamut that can be expressed by the display device Decreases. As a result, the quality of the displayed image is degraded.

  However, in the display device 100, the first hole transport layer 124 formed over the plurality of pixels 104 has a hole mobility smaller than that of the second hole transport layer 126b and the third hole transport layer 126c. As a result, the holes injected from the selected pixel electrode 120 are prevented from being transported to the adjacent pixel 104, and crosstalk does not occur. Therefore, by applying the present embodiment, it is possible to provide a high definition display device excellent in color reproducibility.

  Note that the hole injection layer 122, the electron transport layer 132, the hole blocking layer 130, the electron injection layer 134, and the like are also formed over the plurality of pixels 104. However, the electron transportability of the electron transport layer 132, the hole blocking layer 130, and the electron injection layer 134 is the same as that of the hole injection layer 122, the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c. Crosstalk is less likely to occur because it is smaller than the hole mobility of In addition, the thickness of the hole injection layer 122 is smaller than the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c, so the resistance is high, and the ohmic current flowing in the hole injection layer 122 is It is possible to ignore.

Second Embodiment
In this embodiment, a method for manufacturing the light-emitting element 105 and the display device 100 including the light-emitting element is described. Description of the same or similar configuration as the first embodiment may be omitted.

[1. Pixel circuit]
In each pixel 104, a pixel circuit including the light emitting element 105 is formed of various insulating films, semiconductor films, and conductive films which are patterned. The configuration of the pixel circuit can be arbitrarily selected, an example of which is shown in FIG. 6 as an equivalent circuit.

  The pixel circuit shown by the equivalent circuit in FIG. 6 includes a drive transistor 182, a light emission control transistor 190, a correction transistor 188, an initialization transistor 184, a write transistor 186, a storage capacitor 194, and an additional capacitor 196 in addition to the light emitting element 105. ing. The capacitance 198 is not an independent capacitance element but a parasitic capacitance of the light emitting element 105. The high potential power supply line 160 is supplied with the high potential PVDD, and the potential is supplied to the pixels 104 connected to each column through the current supply line 162. The light emitting element 105, the drive transistor 182, the light emission control transistor 190, and the correction transistor 188 are connected in series between the high potential power supply line 160 and the low potential power supply line 164. Low potential power supply line 164 is supplied with low potential PVSS.

  One terminal of the drive transistor 182 is electrically connected to the high potential power supply line 160 through the light emission control transistor 190 and the correction transistor 188, and the other terminal is electrically connected to the light emitting element 105. The gate of the drive transistor 182 is electrically connected to the first signal line 166 through the initialization transistor 184, and is electrically connected to the second signal line 168 through the write transistor 186. The initialization signal Vini is applied to the first signal line 166, and the video signal Vsig is applied to the second signal line 168. The initialization signal Vini is a signal giving an initialization potential of a fixed level. Write transistor 186 has its operation (on / off) controlled by scan signal SG applied to write control scan line 170 connected to its gate. The gate of the initialization transistor 184 is connected to an initialization control scan line 172 to which an initialization control signal IG is applied, and the operation is controlled by the initialization control signal IG. When the write transistor 186 is on and the initialization transistor 184 is off, the potential of the video signal Vsig is applied to the gate of the drive transistor 182. On the other hand, when the write transistor 186 is off and the initialization transistor 184 is on, the potential of the initialization signal Vini is applied to the gate of the drive transistor 182.

  A correction control scanning line 174 to which a correction control signal CG is applied and a light emission control scanning line 178 to which a light emission control signal BG is applied are connected to the gates of the correction transistor 188 and the light emission control transistor 190, respectively. The reset control line 176 is connected to one terminal of the drive transistor 182 via the correction transistor 188. The reset control line 176 is connected to a reset transistor 192 provided in the scan line driver circuit 108. The reset transistor 192 is controlled by the reset control signal RG, whereby the reset potential Vrst applied to the reset signal line 180 can be applied to one terminal of the drive transistor 182 via the correction transistor 188.

  A storage capacitor 194 is provided between the other terminal of the drive transistor 182 and the gate. One terminal of the additional capacitance 196 is connected to the other terminal of the drive transistor 182, and the other terminal is connected to the high potential power supply line 160. The additional capacitance 196 may be provided such that the other terminal is connected to the low potential power supply line 164. The storage capacitor 194 and the additional capacitor 196 are provided to hold a gate-source voltage Vgs according to the video signal Vsig when the video signal Vsig is applied to the gate of the drive transistor 182.

The signal line side drive circuit 110 or the drive IC 116 outputs the initialization signal Vini and the video signal Vsig to the first signal line 166 and the second signal line 168, respectively. On the other hand, the scanning line side drive circuit 108 outputs the scanning signal SG to the write control scanning line 170, outputs the initialization control signal IG to the initialization control scanning line 172, and outputs the correction control signal CG to the correction control scanning line 174. The light emission control signal BG is output to the light emission control scanning line 178, and the reset control signal RG is output to the gate of the reset transistor 192.
[2. Cross section structure]
The cross-sectional schematic diagram of the display apparatus 100 is shown in FIG. FIG. 7 is a schematic cross-sectional view of three adjacent pixels 104 (first pixel 104 a, second pixel 104 b, and third pixel 104 c) formed on the substrate 102. Here, among the elements included in each pixel 104, the cross-sectional structure of the drive transistor 182, the storage capacitance 194, the additional capacitance 196, and the light emitting element 105 is shown.

  Each element included in the pixel circuit is provided on the substrate 102 via the undercoat 200. The substrate 102 can include glass, quartz, or plastic. By using a plastic, the substrate 102 can have flexibility. Examples of the plastic include polymers such as polyimide, polyamide, polyester, polycarbonate and the like, and among them, polyimide having high heat resistance is preferable. The undercoat 200 may have a single layer structure, and may be composed of a plurality of films as shown in FIG. In the case of using a plurality of films, for example, a film including a film 200 a containing silicon oxide, a film 200 b containing silicon nitride, and a film 200 c containing silicon oxide may be sequentially formed over the substrate 102.

  The driving transistor 182 includes a semiconductor film 202, a gate insulating film 204, a gate electrode 206, a drain electrode 212, and a source electrode 214. The gate electrode 206 is arranged to intersect at least a part of the semiconductor film 202 with the gate insulating film 204 interposed therebetween, and a channel region 202 a is formed in a region where the semiconductor film 202 and the gate electrode 206 overlap. The semiconductor film 202 further includes a low concentration impurity region 202c sandwiching the channel region 202a, and a high concentration impurity region 202b sandwiching the channel region 202a and the low concentration impurity region 202c.

  A capacitor electrode 208 present in the same layer as the gate electrode 206 is provided to overlap with the high concentration impurity region 202 b with the gate insulating film 204 interposed therebetween. An interlayer insulating film 210 is disposed on the gate electrode 206 and the capacitor electrode 208. An opening reaching the high concentration impurity region 202 b is formed in the interlayer insulating film 210 and the gate insulating film 204, and the drain electrode 212 and the source electrode 214 are disposed to cover the opening. A part of the source electrode 214 overlaps a part of the high concentration impurity region 202 b and the capacitance electrode 208 via the interlayer insulating film 210, and a part of the high concentration impurity region 202 b, the gate insulating film 204, the capacitance electrode 208, the interlayer insulation The membrane 210 and part of the source electrode 214 form a storage capacitor 194.

  A planarization film 216 is further provided on the driving transistor 182 and the storage capacitor 194. The planarization film 216 has an opening reaching the source electrode 214, and the connection electrode 220 covering the opening and a part of the top surface of the planarization film 216 is formed in contact with the source electrode 214. An additional capacitance electrode 222 is further provided on the planarization film 216. A capacitive insulating film 224 is disposed to cover the connection electrode 220 and the additional capacitance electrode 222. The capacitive insulating film 224 does not cover a part of the connection electrode 220 at the opening of the planarization film 216 and exposes the upper surface of the connection electrode 220. Thus, electrical connection can be established between the pixel electrode 120 and the source electrode 214 provided thereon via the connection electrode 220. The capacitor insulating film 224 may be provided with an opening 226 for allowing the partition film 140 provided thereon to be in contact with the planarization film 216. Impurities in the planarization film 216 can be removed through the openings 226, whereby the reliability of the light emitting element 105 can be improved. Note that the formation of the connection electrode 220 and the opening 226 is optional.

  The pixel electrode 120 is provided on the capacitive insulating film 224 so as to cover the connection electrode 220 and the additional capacitance electrode 222. The capacitive insulating film 224 is sandwiched between the additional capacitance electrode 222 and the pixel electrode 120, and an additional capacitance 196 is constructed by this structure. The pixel electrode 120 is shared by the additional capacitance 196 and the light emitting element 105.

  A partition 140 covering an end of the pixel electrode 120 is provided on the pixel electrode 120. An EL layer is provided so as to cover the pixel electrode 120 and the partition wall 140, and an opposite electrode 138 is provided thereover. The structure described in the first embodiment can be applied to the EL layer. The counter electrode 138 covers the plurality of pixels 104 and is shared by the plurality of pixels 104. In FIG. 7, the hole injection layer 122, the first hole transport layer 124, the second hole transport layer 126b, the third hole transport layer 126c, the light emitting layer 128, and the electron transport layer in the EL layers are considered in view of easy viewing. Layer 132 is shown.

  The display device 100 may include a passivation film 230 for protecting the light emitting element 105 as an arbitrary configuration. The structure of the passivation film 230 can also be arbitrarily determined, and either a single layer structure or a laminated structure may be employed. In the case of having a laminated structure, for example, as shown in FIG. 7, a first layer 230a containing a silicon-containing inorganic compound, a second layer 230b containing a resin, and a third layer 230c containing a silicon-containing inorganic compound are sequentially laminated. The structure can be adopted. Examples of the silicon-containing inorganic compound include silicon nitride and silicon oxide. Examples of the resin include epoxy resin, acrylic resin, polyester, polycarbonate and the like.

[3. Production method]
FIG. 8A shows a schematic cross-sectional view of the display device 100 in which up to the partition wall 140 is formed. The structure shown here can be manufactured by applying a known method as appropriate, and thus the description will be omitted.

  First, the hole injection layer 122 is formed so as to cover the pixel electrode 120 and the partition wall 140 and to be shared by the first pixel 104a, the second pixel 104b, and the third pixel 104c (see FIG. B)). The hole injection layer 122 is formed by applying a wet film method such as a spin coating method, a printing method, or an inkjet method, or an evaporation method.

  Subsequently, the first hole transport layer 124 is formed so as to cover the pixel electrode 120 and the partition wall 140 and to be shared by the first pixel 104 a, the second pixel 104 b, and the third pixel 104 c (see FIG. Fig. 8 (B). The first hole transport layer 124 is also formed by applying a wet film method or a vapor deposition method. The thickness of the first hole transport layer 124 is adjusted so that the EL layer has an optimal optical distance for the first light emitting element 105 a in the first pixel 104 a, for example, 50 nm to 150 nm, 60 nm to 130 nm, or 80 nm To a thickness of 120 nm.

  Subsequently, the second hole transport layer 126b is formed. Specifically, as shown in FIG. 9A, the second hole transport layer 126b is formed over the first hole transport layer 124 so as to overlap with the second pixel electrode 120b. The second hole transport layer 126 b is a substrate 102 such that the metal mask having an opening is formed such that the opening overlaps the second pixel 104 b and the non-opening portion overlaps the first pixel 104 a and the third pixel 104 c. It can be placed on top and applied by vapor deposition. Thus, the second hole transport layer 126b is not formed in the first pixel 104a and the third pixel 104c, but is selectively formed only in the second pixel 104b. The thickness of the second hole transport layer 126 b is adjusted so that the EL layer has an optimal optical distance for the second light emitting element 105 b in the second pixel 104 b, for example, the first hole transport layer 124 and the second hole transport layer 124 b. The hole transport layer 126b is formed to have a total thickness of 100 nm to 200 nm, 120 nm to 200 nm, or 150 nm to 180 nm.

  Similarly, the third hole transport layer 126c is formed. Specifically, as shown in FIG. 9B, the third hole transport layer 126c is formed over the first hole transport layer 124 so as to overlap with the third pixel electrode 120c. The third hole transport layer 126c is a substrate 102 so that the metal mask having an opening overlaps the first pixel 104a and the second pixel 104b such that the opening overlaps the third pixel 104c. It can be placed on top and applied by vapor deposition. Thus, the third hole transport layer 126c is not formed in the first pixel 104a and the second pixel 104b, but is selectively formed only in the third pixel 104c. The thickness of the third hole transport layer 126c is adjusted so that the EL layer has an optimal optical distance for the third light emitting element 105c in the third pixel 104c. For example, the first hole transport layer 124 and the third hole transport layer 124c are used. The hole transport layer 126c is formed to have a total thickness of 120 nm to 250 nm, 140 nm to 220 nm, or 160 nm to 200 nm. However, in the case where the third light emitting element 105c has the structure shown in FIG. 4, the total thickness of the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c. The third hole transport layer 126 c is formed so that the above-described range is satisfied. The formation order of the second hole transport layer 126 b and the third hole transport layer 126 c is not limited to the order described above, and the latter may be formed before the former.

  In the formation of the first hole transport layer 124, the second hole transport layer 126b, and the third hole transport layer 126c, as described above, the refractive index of the first hole transport layer 124 is the second hole transport layer. The material of each layer is selected to be larger than the refractive index of 126b and the third hole transport layer 126c. Further, the material of each layer is selected so that the hole mobility of the first hole transport layer 124 is smaller than the hole mobility of the second hole transport layer 126 b and the third hole transport layer 126 c. Alternatively, the first hole transport layer 124 may be formed by orienting the molecules of the material used for the first hole transport layer 124 horizontally or in a direction parallel to the main surface of the substrate 102.

  Next, the light emitting layer 128 is formed (FIG. 10A). For example, in the case of forming the first light emitting layer 128a in the first pixel 104a, a metal mask having an opening is formed so that the opening overlaps with the first pixel 104a, and the non-opening portion is the second pixel 104b and the third pixel. The first light emitting layer 128 a is formed by being disposed over the substrate 102 so as to overlap with the pixel 104 c and the material contained in the first light emitting layer 128 a is deposited. Thus, a first light emitting layer 128 a overlapping with the first pixel 104 a is formed on the first hole transport layer 124. The second light emitting element 105 b and the third light emitting element 105 c are also formed by the same method. There is no limitation on the order of forming the light emitting layers 128.

  Even if the second hole transport layer 126b, the third hole transport layer 126c, the first light emitting layer 128a, the second light emitting layer 128b, and the third light emitting layer 128c are formed in the order different from the method described above Good. For example, as shown in FIG. 11A, after the second hole transport layer 126b is formed, the second light emitting layer 128b may be continuously formed. Similarly, after the third hole transport layer 126c is formed, the third light emitting layer 128c may be continuously formed (FIG. 11B). In this case, the second hole transport layer 126 b and the second light emitting layer 128 b can be formed while the metal mask for forming the second hole transport layer 126 b is disposed on the substrate 102, and the third hole transport layer Since the third hole transport layer 126 c and the third light emitting layer 128 c can be formed while the metal mask for forming the 126 c is disposed on the substrate 102, the manufacturing time of the display device 100 can be shortened. Also in this case, the formation order of the first light emitting layer 128a, the second light emitting layer 128b, and the third light emitting layer 128c can be arbitrarily determined.

  Subsequently, the electron transport layer 132 and the counter electrode 138 are sequentially formed so as to overlap the pixel electrode 120 and the partition wall 140 and be shared by the first pixel 104a, the second pixel 104b, and the third pixel 104c (see FIG. FIG. 10 (B). The electron transport layer 132 can be formed using a vapor deposition method. The counter electrode 138 can be formed by evaporation or sputtering. Although not shown, the electron block layer 136, the hole block layer 130, and the electron injection layer 134 also use the vapor deposition method as appropriate, and are shared by the first pixel 104a, the second pixel 104b, and the third pixel 104c. It is formed.

  Subsequently, a passivation film 230 is formed. As shown in FIG. 7, when the passivation film 230 has a three-layer structure, first, the first layer 230a is formed so as to cover the counter electrode 138 (FIG. 7). The first layer 230a contains an inorganic material such as silicon nitride or silicon oxide, for example, and is formed by applying a chemical vapor deposition (CVD) method or a sputtering method.

  Subsequently, the second layer 230b is formed. As shown in FIG. 7, the second layer 230b may be formed to have a thickness that absorbs unevenness due to the partition wall 140 and provides a flat surface. Specifically, the second layer 230 b can be formed by a printing method, an inkjet method, a spin coating method, or the like using a polymer such as an epoxy resin or an acrylic resin. Alternatively, the oligomer serving as a raw material of these polymers may be atomized or gasified under reduced pressure, sprayed onto the first layer 230a, and then polymerized to form the second layer 230b. Good.

  Thereafter, a third layer 230c is formed in contact with the second layer 230b (FIG. 7). The third layer 230c can comprise the materials available for the first layer 230a and can be formed in a manner applicable to the formation of the first layer 230a.

  Through the above steps, the display device 100 illustrated in FIG. 7 can be manufactured.

  The embodiments described above as the embodiments of the present invention can be implemented in combination as appropriate as long as they do not contradict each other. In addition, those in which a person skilled in the art appropriately adds, deletes or changes the design of components based on the display device of each embodiment or those in which steps are added, omitted or conditions changed are also included in the present invention. As long as it comprises the gist, it is included in the scope of the present invention.

  Even if other effects or effects different from the effects brought about by the aspects of the above-described embodiments are apparent from the description of the present specification or those which can be easily predicted by those skilled in the art, it is natural. It is understood that the present invention provides.

  100: display device 102: substrate 104: pixel 104a: first pixel 104b: second pixel 104c: third pixel 105: light emitting element 105 a: first light emitting element 105 b: first 2 light emitting element 105c: third light emitting element 106: display area 108: scanning line driver circuit 110: signal line driver circuit 112: wiring 114: FPC 120: pixel electrode 120a: third 1 pixel electrode 120b: second pixel electrode 120c: third pixel electrode 122: hole injection layer 124: first hole transport layer 126b: second hole transport layer 126c: third Hole transport layer 128: light emitting layer 128a: first light emitting layer 128b: second light emitting layer 128c: third light emitting layer 130: hole blocking layer 132: electron transport layer 134: electron injection layer 136: electronic block layer, 138: counter electrode, 140: partition wall, 142: insulating surface, 144: arrow, 145: arrow, 146: arrow, 147: arrow, 160: high potential power line, 162: current supply line, 164 Low potential power supply line 166: first signal line 168: second signal line 170: write control scan line 172: initialization control scan line 174: correction control scan line 176: reset control line , 178: light emission control scanning line, 180: reset signal line, 182: drive transistor, 184: initialization transistor, 186: write transistor, 188: correction transistor, 190: light emission control transistor, 192: reset transistor, 194: hold Capacity, 196: additional capacity, 198: capacity, 200: undercoat, 200a: film containing silicon oxide, 200b A film containing silicon nitride, 200c: A film containing silicon oxide, 202: a semiconductor film, 202a: a channel region, 202b: a high concentration impurity region, 202c: a low concentration impurity region, 204: a gate insulating film, 206: a gate electrode, 208 : Capacitance electrode, 210: interlayer insulating film, 212: drain electrode, 214: source electrode, 216: planarization film, 220: connection electrode, 222: additional capacitance electrode, 224: capacitance insulating film, 226: opening, 230: passivation Film, 230a: first layer, 230b: second layer, 230c: third layer

Claims (21)

A first pixel, and a second pixel adjacent to the first pixel,
The first pixel is
First pixel electrode,
A first hole transport layer located on the first pixel electrode and extending over the first pixel and the second pixel;
A first light emitting layer on the first hole transport layer, and a counter electrode located on the first light emitting layer and extending over the first pixel and the second pixel;
The second pixel is
Second pixel electrode,
The first hole transport layer on the second pixel electrode;
A second hole transport layer on the first hole transport layer,
A second light emitting layer on the second hole transport layer, and the counter electrode on the second light emitting layer;
The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer,
The display apparatus whose light emission wavelength of a said 1st light emitting layer is shorter than the light emission wavelength of a said 2nd light emitting layer.   The display device according to claim 1, wherein the hole mobility of the second hole transport layer is higher than the hole mobility of the first hole transport layer.   The display device according to claim 1, wherein the first light emitting layer is in contact with the first hole transport layer in the first pixel. The electronic device further includes an electronic block layer extending over the first pixel and the second pixel on the first hole transport layer,
The electron blocking layer according to claim 1, wherein the electron blocking layer is located between the first hole transport layer and the first light emitting layer, and between the second hole transport layer and the second light emitting layer. Display device.   The display device according to claim 1, wherein the first pixel does not include the second hole transport layer. And a third pixel adjacent to the second pixel,
The third pixel is
Third pixel electrode,
The first hole transport layer located on the third pixel electrode and extending over the first pixel, the second pixel, and the third pixel;
A third hole transport layer on the first hole transport layer,
A third light emitting layer on the third hole transport layer, and the third light emitting layer located on the third light emitting layer and extending across the first pixel, the second pixel, and the third pixel Equipped with a counter electrode,
The refractive index of the third hole transport layer is smaller than the refractive index of the first hole transport layer, and is the same as the refractive index of the second hole transport layer,
The display device according to claim 1, wherein a light emission wavelength of the third light emitting layer is longer than a light emission wavelength of the second light emitting layer.   The display device according to claim 6, wherein the second hole transport layer and the third hole transport layer contain the same compound.   The hole mobility of the third hole transport layer is higher than the hole mobility of the first hole transport layer, and the same as the hole mobility of the second hole transport layer. Display device. It further comprises a third pixel adjacent to the second pixel,
The third pixel is
Third pixel electrode,
The first hole transport layer located on the third pixel electrode and extending over the first pixel, the second pixel, and the third pixel;
The second hole transport layer located on the first hole transport layer and extending across the second pixel and the third pixel;
A third hole transport layer on the second hole transport layer,
A third light emitting layer on the third hole transport layer, and the third light emitting layer located on the third light emitting layer and extending across the first pixel, the second pixel, and the third pixel Equipped with a counter electrode,
The refractive index of the third hole transport layer is smaller than the refractive index of the first hole transport layer, and is the same as the refractive index of the second hole transport layer,
The display device according to claim 1, wherein a light emission wavelength of the third light emitting layer is longer than a light emission wavelength of the second light emitting layer.   The display device according to claim 9, wherein the second hole transport layer and the third hole transport layer contain the same compound.   The hole mobility of the third hole transport layer is higher than the hole mobility of the first hole transport layer, and is the same as the hole mobility of the second hole transport layer. Display device. It further comprises a substrate on which the first pixel and the second pixel are located,
The display device according to any one of claims 1 to 11, wherein molecules of the material contained in the first hole transport layer are aligned in a direction parallel to the main surface of the substrate. Forming a first pixel electrode and a second pixel electrode adjacent to the first pixel electrode;
Forming a first hole transport layer to cover the first pixel electrode and the second pixel electrode;
Forming a second hole transport layer on the first hole transport layer so as to cover the second pixel electrode and expose the first hole transport layer on the first pixel electrode; ,
Forming a first light emitting layer on the first pixel electrode via the first hole transport layer;
Forming a second light emitting layer on the second pixel electrode via the first hole transporting layer and the second hole transporting layer; and the first light emitting layer and the second light emitting layer Including forming a counter electrode on top,
The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer,
A method for manufacturing a display device, wherein an emission wavelength of the first light emitting layer is shorter than an emission wavelength of the second light emitting layer.   The method according to claim 13, wherein the hole mobility of the second hole transport layer is higher than the hole mobility of the first hole transport layer.   The manufacturing method according to claim 13, wherein the formation of the first light emitting layer is performed such that the first light emitting layer is in contact with the first hole transport layer on the first pixel electrode.   Before the formation of the first light emitting layer and the second light emitting layer, the first hole transporting layer is in contact with the first pixel electrode on the first pixel electrode, and the second hole transport is on the second pixel electrode The method according to claim 13, further comprising forming an electron blocking layer in contact with the layer. Forming a first pixel electrode, a second pixel electrode adjacent to the first pixel electrode, and a third pixel electrode adjacent to the second pixel electrode;
Forming a first hole transport layer to cover the first pixel electrode, the second pixel electrode, and the third pixel electrode;
The second hole transport layer is covered with the first hole transport layer so as to cover the second pixel electrode and expose the first hole transport layer on the first pixel electrode and the third pixel electrode. Forming on the transport layer,
The third pixel electrode is covered, the first hole transport layer is exposed on the first pixel electrode, and the second hole transport layer is exposed on the second pixel electrode. Forming a third hole transport layer on the first hole transport layer;
Forming a first light emitting layer on the first pixel electrode via the first hole transport layer;
Forming a second light emitting layer on the second pixel electrode via the first hole transport layer and the second hole transport layer;
Forming a third light emitting layer on the third pixel electrode via the first hole transporting layer and the third hole transporting layer; and the first light emitting layer, the second light emitting layer And forming a counter electrode on the third light emitting layer,
The refractive index of the first hole transport layer is larger than the refractive index of the second hole transport layer and the refractive index of the third hole transport layer,
A method for manufacturing a display device, wherein a light emission wavelength of the second light emitting layer is longer than a light emission wavelength of the first light emitting layer and shorter than a light emission wavelength of the third light emitting layer.   The hole mobility of the second hole transport layer and the hole mobility of the third hole transport layer are the same and are higher than the hole mobility of the first hole transport layer. How to make   The manufacturing method according to claim 17, wherein the formation of the first light emitting layer is performed such that the first light emitting layer is in contact with the first hole transport layer on the first pixel electrode.   Before the formation of the first light emitting layer, the second light emitting layer, and the third light emitting layer, the second pixel electrode is in contact with the first hole transport layer on the first pixel electrode The method according to claim 17, further comprising forming an electron blocking layer in contact with the second hole transport layer on the upper side and in contact with the third hole transport layer on the third pixel electrode. . Forming the first pixel electrode on a substrate;
21. The first hole transport layer is formed by orienting molecules of a material contained in the first hole transport layer in a direction parallel to the main surface of the substrate. The production method according to item 1.

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