JP2021087001A - Self-luminous element and self-luminous display panel - Google Patents

Abstract

To provide a self-luminous element and a self-luminous display panel, in which carrier balance of a luminous layer can be improved by guaranteeing hole blockability and electron injectability and thereby improvement in luminous efficiency can be achieved.SOLUTION: A self-luminous element includes: a pixel electrode 13; a luminous layer 17 which is arranged above the pixel electrode 13 and includes a luminescent material; a first functional layer 18 which is arranged on the luminous layer 17 and formed by mixing a metal fluoride and a first organic material that has at least one property of electron transportability and electron injectability; a second functional layer 191 which is arranged on the first functional layer 18, which includes a second organic material that has at least one property of electron transportability and electron injectability, and which is not doped with one or more metal elements selected from among metal elements that belong to alkaline metals, alkaline earth metals, and rare earth elements and have reducibility to the metal fluoride; and a counter electrode 20 arranged above the second functional layer 191.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to a self-luminous element and a self-luminous display panel.

In recent years, as a self-luminous display using an organic EL (Electro Luminescence) element that utilizes the electroluminescence phenomenon of an organic material, an organic EL panel in which a plurality of organic EL elements are arranged along a matrix direction on a substrate has become an electronic device. It has been put to practical use as a display. Each organic EL element has a basic structure in which a plurality of various functional layers such as an electron transport layer including an organic light emitting layer containing an organic light emitting material are laminated between a pair of electrode pairs of an anode and a cathode, and at the time of driving. It is a current-driven light emitting element that is generated by the recombination of holes injected into the organic light emitting layer from the anode and electrons injected into the organic light emitting layer from the cathode by applying a voltage between the pair of electrodes. ..

In such an organic EL device, the lowest empty orbital (LUMO: Lowest Unoccupied Molecular Orbital) and the highest occupied molecular orbital (HOMO: Highest Occupied Molecular Orbital) of each functional layer are appropriately arranged to form holes in the light emitting layer. It is required to improve the carrier balance with electrons to improve the efficiency of the light emitting element.

On the other hand, for example, Patent Document 1 proposes a light emitting device in which a hole block layer (HBL: Hole Block Layer) is provided in an adjacent layer on the cathode side of the light emitting layer.

Further, in Patent Document 2, an intermediate layer made of an alkali metal fluoride is provided between an electron transport layer composed of an organic material and an organic light emitting layer, and a metal material having a low work function is doped in the electron transport layer. Therefore, a light emitting element having improved electron injection property has been proposed.

JP-A-2007-36175 International Publication WO2015-194189

However, in the configuration in which the hole block layer is arranged as the adjacent layer on the cathode side of the light emitting layer, the electron injection property from the hole block layer to the light emitting layer is low, and electrons are insufficient in the light emitting layer, so that sufficient luminous efficiency is achieved. In addition, in the configuration in which an intermediate layer made of alkali metal fluoride is arranged as an adjacent layer on the cathode side of the light emitting layer, the hole blocking property from the light emitting layer to the intermediate layer is low, and holes are insufficient in the light emitting layer. Therefore, there is a problem that sufficient luminous efficiency cannot be obtained.

In view of the above circumstances, it is an object of the present disclosure to provide a self-luminous element and a self-luminous display panel that ensure hole blockability and electron injection property, improve carrier balance in the light emitting layer, and improve luminous efficiency. And.

In order to solve the above problems, the self-luminous element in one aspect of the present disclosure is arranged on a pixel electrode, a light emitting layer containing a light emitting material arranged above the pixel electrode, and an electron. A first functional layer formed by mixing a first organic material having at least one of transportability and electron injectability and a metal fluoride, and an electron transporting property arranged on the first functional layer. It is selected from metal elements belonging to alkali metals, alkaline earth metals, and rare earth elements having reducibility to the metal fluoride, including a second organic material having at least one property of property and electron injection property. It is characterized by including a second functional layer not doped with one or more metal elements, and a counter electrode arranged above the second functional layer.

In the self-luminous element and the self-luminous display panel according to one aspect of the present disclosure, the hole blocking property and the electron injection property are ensured, the carrier balance in the light emitting layer is improved, and the luminous efficiency is improved.

It is a block diagram which shows the whole structure of the organic EL display device which concerns on aspect of this disclosure. It is a schematic plan view which enlarged a part of the image display surface of the organic EL panel in the said organic EL display apparatus. It is a schematic cross-sectional view along the line AA of FIG. It is a schematic diagram which shows the laminated structure of the organic EL element 2 which concerns on one aspect of this disclosure. (A) is a schematic diagram showing energy levels of the hole transport layer, the light emitting layer, and the electron transport layer in the organic EL element 2, and (b) is an operation explanatory diagram. It is a flowchart which shows the manufacturing process of the organic EL display panel which concerns on one aspect of this disclosure. (A) to (d) are partial cross-sectional views schematically showing a manufacturing process of an organic EL element. (A) to (d) are partial cross-sectional views schematically showing the manufacturing process of the organic EL element following FIG. (A) and (b) are partial cross-sectional views schematically showing the manufacturing process of the organic EL element following FIG. (A) to (e) are partial cross-sectional views schematically showing the manufacturing process of the organic EL element following FIG. This is an experimental result showing the relationship between the mixing ratio of sodium fluoride in the first functional layer and the luminous efficiency in the organic EL element 2. It is a schematic diagram which shows the state which the energy level of a hole transport layer, a light emitting layer, and an electron transport layer in an organic EL element 2 is appropriately balanced. (A) and (b) are schematic views showing the laminated structure of the conventional organic EL elements 2Y and 2X. (A) and (b) are operation explanatory views of the conventional organic EL elements 2Y and 2X.

<< Background to the form for carrying out the invention >>
In an organic EL element, by optimally designing the arrangement of the lowest empty orbital (LUMO) and the highest occupied orbital (HOMO) of each functional layer, the carrier balance between holes and electrons in the light emitting layer is improved, and light emission is performed. It is required to improve the efficiency of the device.

Hereinafter, a method for optimizing the carrier movement in the light emitting layer in the organic EL element will be described with reference to the drawings. FIG. 12 is a schematic view showing a state in which the energy levels of the hole transport layer, the light emitting layer, and the electron transport layer in the organic EL element are appropriately set.

As shown in the figure, when a voltage is applied between the pixel electrode (anode) and the counter electrode (cathode), the electron electrode reaches the highest occupied orbital (HOMO) of the light emitting layer via the hole transport layer. Holes are supplied, and electrons are supplied from the counter electrode to the lowest empty orbital (LUMO) of the light emitting layer via the electron transport layer. Then, the holes supplied from the hole transport layer side and the electrons supplied from the electron transport layer side with respect to the light emitting layer are recombined in the light emitting layer to generate an excited state and emit light.

In this recombination, when the electrons and holes injected into the light emitting layer are quantitatively balanced while maintaining a good carrier balance, the electrons and holes are recombined with little excess or deficiency. Therefore, residual holes or electrons are rarely generated, many holes and electrons can be contributed to light emission, and the luminous efficiency of the organic EL element can be optimized.

FIG. 13 (a) is a schematic view showing a laminated structure of a main portion (a portion from the anode to the cathode: hereinafter, also referred to as a “light emitting portion”) of the conventional organic EL element 2Y, and FIG. 14 (a). ) Is an operation explanatory diagram of the organic EL element 2Y.

In the organic EL element 2Y, as shown in FIG. 13A, the hole injection layer 15, the hole transport layer 16, the light emitting layer 17, the hole block layer 18Y (HBL) electron transport layer 191Y, and the electron injection transport are performed on the pixel electrode 13. A light emitting portion is formed by laminating the layer 192Y and the counter electrode 20.

As shown in FIG. 14A, the organic EL element 2Y has a configuration in which a hole block layer 18Y having a larger absolute value of the HOMO level than the light emitting layer 17 is provided as an adjacent layer on the cathode side of the light emitting layer 17. This blocks the movement of holes and excitons from the light emitting layer 17 to the electron transport layer 191Y. This makes it possible to confine holes in the light emitting layer 17 to increase the amount of holes bonded to electrons, and to efficiently convert exciton energy into light.

However, the organic EL element 2Y has a problem that the electron injection property of the organic material used for the hole block layer 18Y into the light emitting layer 17 is low, and sufficient light emission efficiency cannot be obtained due to lack of electrons in the light emitting layer 17. there were.

On the other hand, in the organic EL element 2X, as shown in FIG. 13B, an intermediate layer 18X composed of a hole injection layer 15, a hole transport layer 16, a light emitting layer 17, and a material having high electron injection property on the pixel electrode 13. , The electron injection transport layer 19X and the counter electrode 20 are laminated to form a light emitting portion. The intermediate layer 18X is composed of an intermediate layer made of an alkali metal fluoride, for example, a layer made of a metal compound such as sodium fluoride, and is selected from an alkali metal or an alkaline earth metal doped in an adjacent electron transport layer 19Y. The metal element M1 having a low work function, for example, barium, cesium, lithium, etc., reduces the alkali metal fluoride in the intermediate layer and partially dissociates it into the alkali metal, thereby enhancing the electron injection property. The structure is adopted.

As shown in FIG. 14B, the organic EL element 2X uses an intermediate layer 18X made of a material having higher electron injection property than the hole block layer 18Y as an adjacent layer on the cathode side of the light emitting layer 17, and therefore emits light. The electron injection property into the layer 17 is improved, and it is possible to prevent a shortage of electrons in the light emitting layer 17.

However, in the organic EL element 2X, since the intermediate layer 18X having a smaller absolute value of the HOMO level than the hole block layer 18Y is provided as an adjacent layer on the cathode side of the light emitting layer 17, the light emitting layer 17 to the electron transport layer 191Y Insufficient holes and exciton blocks. Further, in the study of the inventor, it is considered that a part of the metal compound of the intermediate layer 18X is reduced by the metal element contained in the electron transport layer 19Y, so that the blocking property of the intermediate layer 18X with respect to holes and excitons is lowered. As a result, holes move from the light emitting layer 17 to the intermediate layer 18X, the amount of holes bonded to electrons in the light emitting layer 17 decreases, excitons move from the light emitting layer 17 to the intermediate layer 18X, and exciton energy. There was a problem that it could not be efficiently converted into light.

In order to solve the above problems, the inventor has diligently studied a laminated structure of an organic EL element that secures hole blockability and electron injection property and improves the carrier balance in the light emitting layer, and achieves one aspect of the present disclosure. This is an idea for the organic EL element and the organic EL display panel.

<< Outline of the form for carrying out the invention >>
The self-luminous element according to one aspect of the present disclosure is arranged on a pixel electrode, a light emitting layer containing a light emitting material arranged above the pixel electrode, and the light emitting layer, and is electron transportable and electron injectable. A first functional layer obtained by mixing a first organic material having at least one of these properties and having a hole-blocking property and a metal fluoride, and an electron transporting layer arranged on the first functional layer. One or more metal elements selected from alkali metals, alkaline earth metals, and rare earth elements, including a second organic material having at least one property of property and electron injection property, and having a reducing property with respect to the metal fluoride. It is characterized in that it is provided with a second functional layer that does not contain the above, and a counter electrode arranged above the second functional layer. In another aspect, the metal fluoride may be a fluoride of an alkali metal, an alkaline earth metal, and a rare earth element. In another aspect, the metal fluoride may be sodium fluoride.

With this configuration, the metal element M1 having a reducing property for metal fluoride such as sodium fluoride spreads to the first functional layer, and the fluoride of the alkali metal in the first functional layer is reduced to partially reduce it. It is possible to prevent dissociation into alkali metal and prevent deterioration of hole blocking property. At the same time, the electron injection property from the first functional layer to the light emitting layer can be improved. As a result, the carrier balance in the light emitting layer can be improved and the luminous efficiency can be improved.

In another aspect, in any of the above embodiments, the metal element may be one or more metal elements selected from barium, lithium, cesium, and ytterbium. In another aspect, in any of the above embodiments, the film thickness of the first functional layer may be 1 nm or more and 10 nm or less.

With such a configuration, it is possible to realize a self-luminous element that secures hole blockability and electron injection property, improves carrier balance in the light emitting layer, and improves light emission efficiency.

In another aspect, in any of the above embodiments, the first functional layer may be a vapor-deposited film of the first organic material and sodium fluoride.

With such a configuration, it is possible to realize a first functional layer in which a first organic material having at least one of electron transporting property and electron injecting property and having hole blocking property and sodium fluoride is mixed.

In another aspect, in any of the above embodiments, the concentration of sodium fluoride contained in the first functional layer may be 70 wt% or less.

With such a configuration, the luminous efficiency and the drive voltage reduction rate can be sharply increased as compared with the range other than the above.

In another aspect, in any of the above embodiments, the concentration of sodium fluoride contained in the first functional layer may be 10 wt% or more and 50 wt% or less.

With such a configuration, the luminous efficiency and the drive voltage reduction rate can be further increased.

In another aspect, in any of the above embodiments, the film thickness of the second functional layer may be 5 nm or more and 30 nm or less.

With this configuration, the metal element M2 contained in the electron injection transport layer is prevented from spreading to the first functional layer and the sodium fluoride in the first functional layer is reduced, and the electron injection into the light emitting layer is suppressed. The sex can be improved.

In another aspect, in any of the above embodiments, the film thickness of the first functional layer may be equal to or less than the film thickness of the second functional layer.

With such a configuration, the electron injection property in the first functional layer can be ensured.

In another aspect, in any of the above embodiments, the absolute value of HOMO of the first organic material may be 6.0 eV or more.

With such a configuration, the hole blockability in the first functional layer can be ensured.

In another aspect, in any of the above embodiments, the triplet excitation level value of the first organic material may be 2.0 eV or more.

With such a configuration, when the light emitting material contained in the light emitting layer is a phosphorescent material, the movement of excitons from the light emitting layer to the second functional layer can be blocked.

In another aspect, in any of the above embodiments, at least one of the electron transporting property and the electron injecting property is further provided above the second functional layer and below the counter electrode. The third organic material may be provided with a third functional layer doped with one or more metal elements selected from alkali metals, alkaline earth metals and rare earth metals. In another aspect, in any of the above embodiments, one selected from alkali metals, alkaline earth metals and rare earth metals is further above the second functional layer and below the counter electrode. The configuration may include a third functional layer made of the above metal elements. Further, the metal element contained in the third functional layer may be ytterbium.

With this configuration, the metal element M1 having a reducing property for metal fluoride such as sodium fluoride is not present in the electron transport layer, so that the influence of the metal element M2 contained in the electron injection transport layer is the first function. The structure does not spread to the sodium fluoride in the layer. Therefore, the content of M2 such as a metal element contained in the third functional layer can be optimally set with respect to the electron injection property and the electron transport property in the third functional layer. It is not necessary to determine the content of M2 such as a metal element in consideration of the reducing property of the fluoride of the alkali metal in the first functional layer, and the electron injection property and the electron transport property in the third functional layer are further enhanced. Can be done.

In another aspect, in any of the above embodiments, the pixel electrode may be light-reflecting and the counter electrode may be semipermeable.

With such a configuration, a top emission type self-luminous element can be realized.

In another aspect, in any of the above embodiments, an organic material having at least one of hole transportability and hole injection property is contained above the pixel electrode and below the light emitting layer. The configuration may include four functional layers.

With such a configuration, the hole injection property and the hole transport property from the pixel electrode are improved, the supply of holes to the light emitting layer is promoted, and high efficiency can be achieved.

In another aspect, in any of the above embodiments, the film thickness of at least one of the light emitting layer and the fourth functional layer may be different depending on the wavelength of the light emitted by the light emitting layer.

With such a configuration, the optical resonator structure can be easily constructed, and further improvement in luminous efficiency can be expected.

In another aspect, in any of the above embodiments, at least one of the light emitting layer and the fourth functional layer may be a coating film.

With such a configuration, the manufacturing cost can be reduced by adopting the wet process. When the film is formed by the wet process, the residual amount of impurities such as water increases as compared with the case of the dry process, but the sodium fluoride contained in the first functional layer causes the second functional layer and the third functional layer due to the residual water. It is possible to extend the life by suppressing the deterioration of the functional layer.

In another aspect, in any of the above embodiments, a plurality of self-luminous elements according to any one of claims 1 to 15 are arranged in a matrix on the substrate, and the self-luminous elements are adjacent to each other in the row direction. The light emitting layer in the light emitting element may be a self-luminous display panel partitioned by banks extending in the row direction.

With such a configuration, it is possible to realize a self-luminous display panel that secures hole blockability and electron injection property, improves carrier balance in the light emitting layer, and improves light emission efficiency.

<< Embodiment >>
Hereinafter, the organic EL element, the organic EL panel, and the organic EL display device as the self-luminous element and the self-luminous display panel according to one aspect of the present disclosure will be described with reference to the drawings. It should be noted that the drawings include schematic ones, and the scale and aspect ratio of each member may differ from the actual ones.

1. 1. Overall Configuration of Organic EL Display Device 1 FIG. 1 is a block diagram showing an overall configuration of the organic EL display device 1. The organic EL display device 1 is a display device used for, for example, a television, a personal computer, a mobile terminal, a commercial display (electronic signage, a large screen for commercial facilities), and the like.

The organic EL display device 1 includes an organic EL display panel 10 (hereinafter referred to as “display panel 10”) and a drive control unit 200 electrically connected to the organic EL display panel 10.

In the present embodiment, the display panel 10 is a top-emission type display panel whose upper surface is a rectangular image display surface. On the display panel 10, a plurality of organic EL elements (not shown) are arranged along the image display surface, and the light emission of each organic EL element is combined to display an image. The display panel 10 adopts an active matrix method as an example.

The drive control unit 200 includes a drive circuit 210 connected to the display panel 10 and a control circuit 220 connected to an external device such as a computer or a receiving device such as an antenna. The drive circuit 210 is a power supply circuit that supplies electric power to each organic EL element, a signal circuit that applies a voltage signal that controls the electric power supplied to each organic EL element, and a scan that switches a location where a voltage signal is applied at regular intervals. It has a circuit and so on.

The control circuit 220 controls the operation of the drive circuit 210 according to data including image information input from an external device or a receiving device.

In FIG. 1, four drive circuits 210 are arranged around the display panel 10 as an example, but the configuration of the drive control unit 200 is not limited to this, and the number and positions of the drive circuits 210 are not limited to this. Can be changed as appropriate. Further, for the sake of explanation below, as shown in FIG. 1, the direction along the long side of the upper surface of the display panel 10 is defined as the X direction, and the direction along the short side of the upper surface of the display panel 10 is defined as the Y direction.

2. Configuration of Display Panel 10 (A) Planar Configuration FIG. 2 is a schematic plan view in which a part of the image display surface of the display panel 10 is enlarged. In the display panel 10, as an example, sub-pixels 100R, 100G, and 100B that emit light to R (red), G (green), and B (blue) (hereinafter, also simply referred to as R, G, and B) are arranged in a matrix. It is arranged. The sub-pixels 100R, 100G, and 100B are arranged alternately in the X direction, and a set of sub-pixels 100R, 100G, and 100B arranged in the X direction constitute one pixel P. In the pixel P, it is possible to express full color by combining the emission luminance of the sub-pixels 100R, 100G, and 100B whose gradation is controlled.

Further, in the Y direction, only one of the sub-pixel 100R, the sub-pixel 100G, and the sub-pixel 100B is arranged to form the sub-pixel row CR, the sub-pixel row CG, and the sub-pixel row CB, respectively. As a result, the pixels P are arranged in a matrix along the X and Y directions as a whole of the display panel 10, and the image is displayed on the image display surface by combining the coloring of the pixels P arranged in the matrix.

Organic EL elements 2 (R), 2 (G), and 2 (B) (see FIG. 3) that emit light in the colors R, G, and B are arranged in the sub-pixels 100R, 100G, and 100B, respectively.

Further, the display panel 10 according to the present embodiment employs a so-called line bank method. That is, a plurality of banks 14 for partitioning the sub-pixel columns CR, CG, and CB for each column are arranged at intervals in the X direction, and in each sub-pixel sequence CR, CG, and CB, the sub-pixels 100R, 100G, and 100B are arranged. It shares an organic light emitting layer.

However, in each of the sub-pixel columns CR, CG, and CB, a plurality of pixel regulation layers 141 that insulate the sub-pixels 100R, 100G, and 100B are arranged at intervals in the Y direction, and the sub-pixels 100R, 100G, and 100B are arranged. It can emit light independently.

The height of the pixel regulation layer 141 is lower than the height of the liquid level when the organic light emitting layer is coated with ink. In FIG. 2, the bank 14 and the pixel regulation layer 141 are represented by a dotted line, which is because the pixel regulation layer 141 and the bank 14 are not exposed on the surface of the image display surface and are inside the image display surface. Because it is arranged.

(B) Cross-sectional configuration FIG. 3 is a schematic cross-sectional view taken along the line AA of FIG. In the display panel 10, one pixel is composed of three sub-pixels that emit light of R, G, and B, and each sub-pixel emits the corresponding color of the organic EL elements 2 (R), 2 (G), and the like. It is composed of 2 (B).

Since the organic EL elements 2 (R), 2 (G), and 2 (B) of each emission color basically have substantially the same configuration, they will be described as the organic EL element 2 when they are not distinguished.

As shown in FIG. 3, the organic EL element 2 includes a substrate 11, an interlayer insulating layer 12, a pixel electrode (anode) 13, a bank 14, a hole injection layer 15, a hole transport layer 16, a light emitting layer 17, and a hole block / electron transport. From the layer (first functional layer) 18, the electron transport layer (second functional layer) 191 and the electron injection transport layer (third functional layer) 192, the counter electrode (cathode) 20, and the sealing layer 21. Become.

The substrate 11, the interlayer insulating layer 12, the intermediate layer 18, the second functional layer 19, the counter electrode 20, and the sealing layer 21 are not formed for each pixel, but a plurality of organic ELs included in the display panel 10. It is formed in common with the element 2.

(1) Substrate The substrate 11 includes a base material 111 which is an insulating material and a TFT (Thin Film Transistor) layer 112. A drive circuit is formed in the TFT layer 112 for each sub-pixel. The base material 111 includes, for example, a glass substrate, a quartz substrate, a silicon substrate, molybdenum sulfide, copper, zinc, aluminum, stainless steel, magnesium, iron, nickel, gold, silver and other metal substrates, gallium arsenic and other semiconductor substrates, and plastic substrates. Etc. can be adopted.

As the plastic material, either a thermoplastic resin or a thermosetting resin may be used. For example, polyethylene, polypropylene, polyamide, polyimide (PI), polycarbonate, acrylic resin, polyethylene terephthalate (PET), polybutylene terephthalate, polyacetal, other fluororesins, styrene-based, polyolefin-based, polyvinyl chloride-based, polyurethane-based, Various thermoplastic elastomers such as fluororubber type and chlorinated polyethylene type, epoxy resin, unsaturated polyester, silicone resin, polyurethane, etc., or copolymers, blends, polymer alloys, etc. mainly composed of these can be mentioned. A laminated body in which one type or two or more types are laminated can be used.

(2) Interlayer Insulation Layer The interlayer insulation layer 12 is formed on the substrate 11. The interlayer insulating layer 12 is made of a resin material and is for flattening a step on the upper surface of the TFT layer 112. Examples of the resin material include a positive type photosensitive material. Moreover, as such a photosensitive material, an acrylic resin, a polyimide resin, a siloxane resin, and a phenol resin can be mentioned. Further, although not shown in the cross-sectional view of FIG. 3, contact holes are formed in the interlayer insulating layer 12 for each sub-pixel.

(3) Pixel Electrode The pixel electrode 13 includes a metal layer made of a light-reflecting metal material and is formed on the interlayer insulating layer 12. The pixel electrode 13 is provided for each sub-pixel and is electrically connected to the TFT layer 112 through a contact hole (not shown). In this embodiment, the pixel electrode 13 functions as an anode.

Specific examples of the metal material having light reflectivity include Ag (silver), Al (aluminum), aluminum alloy, Mo (molybdenum), APC (alloy of silver, palladium and copper), ARA (silver, rubidium, gold). , MoCr (alloy of molybdenum and chromium), MoW (alloy of molybdenum and tungsten), NiCr (alloy of nickel and chromium), and the like.

The pixel electrode 13 may be composed of a metal layer alone, but as a laminated structure in which a layer made of a metal oxide such as ITO (indium tin oxide) or IZO (indium tin oxide) is laminated on the metal layer. May be good.

(4) Bank / Pixel Control Layer The bank 14 partitions a plurality of pixel electrodes 13 arranged for each sub-pixel above the substrate 11 for each row in the X direction (see FIG. 2), and is in the X direction. It is a line bank shape extending in the Y direction between the sub-pixel rows CR, CG, and CB arranged in the same direction.

An electrically insulating material is used for the bank 14. As a specific example of the electrically insulating material, for example, an insulating organic material (for example, acrylic resin, polyimide resin, novolak resin, phenol resin, etc.) is used.

The bank 14 functions as a structure for preventing the applied inks of each color from overflowing and mixing when the light emitting layer 17 is formed by the coating method.

When a resin material is used, it is preferable to have photosensitivity from the viewpoint of processability. The photosensitivity may be either positive type or negative type.

The bank 14 preferably has resistance to organic solvents and heat. Further, in order to suppress the outflow of ink, it is preferable that the surface of the bank 14 has a predetermined liquid repellency.

In the portion where the pixel electrode 13 is not formed, the bottom surface of the bank 14 is in contact with the upper surface of the interlayer insulating layer 12.

The pixel regulation layer 141 is made of an electrically insulating material, covers the ends of the pixel electrodes 13 adjacent to the Y direction (FIG. 2) in each sub-pixel row, and partitions the pixel electrodes 13 adjacent to the Y direction. ..

The film thickness of the pixel regulation layer 141 is set to be slightly larger than the film thickness of the pixel electrode 13 but smaller than the thickness up to the upper surface of the light emitting layer 17. As a result, the light emitting layer 17 in each of the sub-pixel rows CR, CG, and CB is not partitioned by the pixel regulating layer 141, and the flow of ink when forming the light emitting layer 17 is not hindered. Therefore, it is easy to make the thickness of the light emitting layer 17 in each sub-pixel row uniform.

With the above structure, the pixel regulation layer 141 improves the electrical insulation of the pixel electrodes 13 adjacent to each other in the Y direction, suppresses the step breakage of the light emitting layer 17 in each of the sub-pixel rows CR, CG, and CB, and faces the pixel electrodes 13. It has a role of improving the electrical insulation between the electrode 20 and the like.

Specific examples of the electrically insulating material used for the pixel regulation layer 141 include a resin material and an inorganic material exemplified as the material of the bank 14. Further, when the light emitting layer 17 to be the upper layer is formed, it is preferable that the surface of the pixel regulation layer 141 has a liquid property to the ink so that the ink can be easily wetted and spread.

(5) Hole Injection Layer The hole injection layer 15 is provided in the opening 14a on the pixel electrode 13 for the purpose of promoting the injection of holes (holes) from the pixel electrode 13 into the light emitting layer 17. The hole injection layer 15 is formed by, for example, an oxide such as silver (Ag), molybdenum (Mo), chromium (Cr), vanadium (V), tungsten (W), nickel (Ni), iridium (Ir), or PEDOT. A layer made of a conductive polymer material such as (mixture of polythiophene and polystyrene sulfonic acid). Among the above, the hole injection layer 15 made of a metal oxide has a function of injecting holes into the light emitting layer 17 stably or assisting the formation of holes. In the present embodiment, the hole injection layer 15 is formed of a conductive polymer material such as PEDOT (a mixture of polythiophene and polystyrene sulfonic acid) by a wet process such as a printing method.

(6) Hole transport layer The hole transport layer 16 has a function of transporting holes injected from the hole injection layer 15 to the light emitting layer 17. The hole transport layer 16 includes, for example, an arylamine derivative, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazoline derivative and a pyrazolone derivative, a phenylenediamine derivative, an amino-substituted chalcone derivative, an oxazole derivative, and a styrylanthracene derivative. It is a material consisting of a fluorenone derivative, a hydrazone derivative, a stillben derivative, a butadiene compound, a polystyrene derivative, a hydrazone derivative, a triphenylmethane derivative, a tetraphenylbenzine derivative, or a combination thereof.
Further, polyfluorene or a derivative thereof, or a polymer compound such as polyarylamine or a derivative thereof, which does not have a hydrophilic group, may be formed by a wet process such as a printing method.

(7) Organic Light Emitting Layer The light emitting layer 17 is formed in the opening 14a and has a function of emitting light of each color of R, G, and B by recombination of holes and electrons. In particular, when it is necessary to specify and explain the emission color, the emission layers 17 (R), 17 (G), and 17 (B) are described.

A known material can be used as the organic light emitting material used for the light emitting layer 17. For example, oxinoid compounds, perylene compounds, coumarin compounds, azacumine compounds, oxazole compounds, oxaziazole compounds, perinone compounds, pyrolopyrrole compounds, naphthalene compounds, anthracene compounds, fluorene compounds, fluoranthene compounds, tetracene compounds, pyrene compounds, coronen compounds, Kinolone compounds and azaquinolone compounds, pyrazoline derivatives and pyrazolone derivatives, rhodamine compounds, chrysene compounds, phenanthrene compounds, cyclopentadiene compounds, stilben compounds, diphenylquinone compounds, styryl compounds, butadiene compounds, dicyanomethylenepyran compounds, dicyanomethylenethiopyran compounds, fluorescein Compounds, pyririum compounds, thiapyrrium compounds, selenapyrylium compounds, tellropyrylium compounds, aromatic aldaziene compounds, oligophenylene compounds, thioxanthene compounds, anthracene compounds, cyanine compounds, acrydin compounds, metal chains of 8-hydroxyquinoline compounds, 2- Fluorescent substances such as metal chains of bipyridine compounds, chains of shift salts and Group III metals, oxine metal chains, rare earth chains, and metal complexes that emit phosphorescence such as tris (2-phenylpyridine) iridium. Known phosphorescent substances can be used.

(8) Hole block / electron transport layer 18 (first functional layer)
The hole block / electron transport layer 18 has a function of blocking the movement of holes and excitons from the light emitting layer 17 to the electron transport layer 191 and transporting electrons from the counter electrode 20 to the light emitting layer 17. The hole block / electron transport layer 18 prevents the holes injected from the pixel electrode 13 from passing through the light emitting layer 17 and being injected into the electron transport layer 191 without contributing to recombination, thereby forming the holes into the light emitting layer 17. It has a function of confining the inside and preventing the excitation energy generated in the light emitting layer 17 from being transferred to the molecules in the electron transport layer 191. This makes it possible to prevent a decrease in luminous efficiency.

The hole block / electron transport layer 18 is arranged adjacent to the cathode side of the light emitting layer 17, has at least one property of electron transport property and electron injection property, and is a first organic material having a hole block property. , Metal fluoride, for example, sodium fluoride (NaF), is a first functional layer formed by mixing by co-evaporation. In addition to sodium fluoride, the metal fluoride may be an alkali metal, an alkaline earth metal, or a fluoride of a rare earth element. For example, ytterbium fluoride (YbF ₃ ), lithium fluoride (LiF), and barium fluoride (BaF ₂ ) are suitable. In addition, as alkali metal fluoride, cerium fluoride (CeF ₃ ), lithium fluoride (LiF), sodium fluoride (NaF), as alkaline earth metal fluoride, calcium fluoride (CaF ₂ ), magnesium fluoride (MgF ₂ ), barium fluoride (BaF ₂ ), as rare earth metal fluoride, lanthanum fluoride (LaF ₃ ), _{neodium fluoride (NdF 3} ), samarium fluoride (SmF ₃ ), yttrium fluoride (YbF ₃ ) , Yttrium fluoride (YF ₃ ), gadolinium fluoride (GdF ₃ ) and the like may be used. As the first organic material, it is preferable to use a material having a lower HOMO level (the absolute value of the HOMO level is larger) and a larger bandgap than the molecules in the light emitting layer 17. Specifically, the difference between the HOMO level of the molecule contained in the hole block / electron transport layer 18 and that of the molecule contained in the light emitting layer 17 is preferably 0.2 eV or more, and more preferably 0.5 eV or more. preferable. The difference between the bandgap of the molecules contained in the hole block / electron transport layer 18 and the bandgap of the molecules contained in the light emitting layer is preferably 0.2 eV or more, and more preferably 0.5 eV or more. As a specific first organic material, for example, CBP, BCP, or the like can be used. Further, a metal complex having a relatively large bandgap (for example, 2.8 eV or more) such as a phenanthroline derivative, an oxadiazole derivative, a triazole derivative, and bis (2-methyl-8-quinolinolato) (4-hydroxy-biphenylyl) aluminum can be used. Can be used.

When the organic light emitting material contained in the light emitting layer 17 is a phosphorescent material, it is preferable to use a material having a higher triplet level (T1) than the light emitting material. In this case, the triplet level of the organic light emitting material is preferably 0.2 eV or more higher than the triplet level of the first organic material contained in the hole block / electron transport layer 18, and is preferably 0.5 eV or more. More preferred.

Further, by setting the value of the triplet excitation level of the organic material constituting the hole block / electron transport layer 18 to 2.0 eV or more, the movement of excitons from the light emitting layer 17 to the electron transport layer 191 is blocked. can do.

Further, in the hole block / electron transport layer 18, the electron transport property can be further improved by mixing sodium fluoride with the first organic material. Therefore, the mixed sodium fluoride is not reduced by the metal element M1 and the metal element M2, which will be described later, and therefore exists as a compound in the hole block / electron transport layer 18. Therefore, by preventing the dissociation of sodium fluoride, it is possible to prevent a decrease in hole blocking property.

In the mixing of the first organic material and sodium fluoride, the weight ratio of sodium fluoride is preferably 70 wt% or less, preferably 10 wt% or more and 50 wt% or less, based on the weight of the hole block / electron transport layer 18. More preferably.

The film thickness of the hole block / electron transport layer 18 is preferably 1 nm or more and 10 nm or less. A function of containing a predetermined amount of sodium fluoride and having a thickness of 1 nm or more to block the movement of holes and excitons, and having a thickness of 10 nm or less to improve the electron injection property into the light emitting layer 17. Have.

That is, it is possible to optimize the carrier movement between the light emitting layer and the adjacent layer in the hole block / electron transport layer 18. FIG. 5A is a schematic diagram showing energy levels of the hole transport layer, the light emitting layer, and the electron transport layer in the organic EL element 2, and FIG. 5B is an operation explanatory diagram.

Since the HOMO level of the constituent material of the hole block / electron transport layer 18 is lower than that of the light emitting layer 17 (the absolute value of the HOMO level is large), holes and excitons from the light emitting layer 17 to the electron transport layer 191 can be formed. It has a function to block movement. Specifically, by setting the absolute value of HOMO of the organic material constituting the hole block / electron transport layer 18 to 6.0 eV or more, the HOMO level and the light emitting layer of the molecules contained in the hole block / electron transport layer 18 are set. A configuration can be adopted in which the difference between the molecule contained in 17 and that of the molecule (A in FIG. 5A) is 0.2 eV or more, more preferably 0.5 eV or more. As a result, as shown in FIG. 5B, the hole movement from the light emitting layer 17 to the electron transport layer 191 can be blocked.

Further, the film thickness of the hole block / electron transport layer 18 is 1 nm or more and 10 nm or less, and the concentration of sodium fluoride is 70 wt% or less, more preferably 10 wt% or more and 50 wt% or less. As shown in the above, the electron injection property from the hole block / electron transport layer 18 to the light emitting layer 17 can be improved.

(9) Electron transport, electron injection transport layer: 19
(9-1) Electron transport layer 191 (second functional layer)
The electron transport layer 191 has a function of transporting electrons from the counter electrode 20 to the light emitting layer 17. The electron transport layer 191 is arranged adjacent to the cathode side of the hole block / electron transport layer 18, and is composed of a second organic material having at least one of electron transport property and electron injection property. Examples of the second organic material (host material) include π-electron low-molecular-weight organic materials such as oxadiazole derivative (OXD), triazole derivative (TAZ), and phenanthroline derivative (BCP, Bphen). Not limited to these.

Further, the electron transport layer 191 is selected from alkali metals, alkaline earth metals, and rare earth elements such as barium, cesium, lithium, and ytterbium, and has one or more reducing properties for metal fluorides such as sodium fluoride. A configuration that does not contain the metal element M1 is adopted. As a result, the metal element M1 having a reducing property for metal fluoride such as sodium fluoride spreads to the hole block / electron transport layer 18, and the fluoride of the alkali metal in the hole block / electron transport layer 18 is reduced. , It is possible to prevent partial dissociation into alkali metal. Here, even in the case where the electron transport layer 191 does not contain the metal element M1 described above, for example, the alkali metal that substantially constitutes the hole block / electron transport layer 18 in the electron transport layer 191. It may be allowed to contain the metal element M1 as long as it does not dissociate the fluoride of the above.

By setting the thickness of the electron transport layer 191 to 5 nm or more, the metal element M2 contained in the electron injection transport layer 192 spreads to the hole block / electron transport layer 18, and the alkali metal in the hole block / electron transport layer 18 It is possible to prevent the fluoride of the above from being reduced. Further, when the thickness of the electron transport layer 191 is 30 nm or less, the electron injection property into the light emitting layer 17 can be improved.

Due to the above-mentioned configuration in which the metal element M1 having a reducing property for metal fluoride such as sodium fluoride does not exist in the electron transport layer 191, the hole block / electron transport layer 18 contains an alkali metal, an alkaline earth metal, and the like. And a state in which a metal element having a reducing property to a metal fluoride such as sodium fluoride such as a rare earth element does not exist can be configured. From this, the dissociation of sodium fluoride existing in the state of the compound can be suppressed.

(9-2) Electron injection transport layer 192 (third functional layer)
The electron injection transport layer 192 has a function of injecting and transporting electrons supplied from the counter electrode 20 toward the light emitting layer 17. The electron injection transport layer 192 may adopt a configuration in which a second organic material having electron transportability is doped with M2 such as a metal element that enhances electron transportability.

The second organic material (host material) can be selected from the same organic material group as the first organic material described above. The second organic material may be the same material as the first organic material, or may be a different material.

The metal element M2 is selected from alkali metals, alkaline earth metals, rare earth elements such as lithium, barium, calcium, potassium, cesium, sodium, rubidium and other low work function metals, lithium fluoride, itterbium and the like. Low-work-function metal salts such as ru, low-work-function metal oxides such as barium oxide, and low-work-function metal organic complexes such as lithium quinolinol are used. When the electron injection transport layer 192 contains lithium quinolinol, it is reduced by the metal material of the counter electrode 20, and the lithium quinolinol in the electron injection transport layer 192 is dissociated and exists as lithium. There is.

Further, the electron injection transport layer 192 may be composed of one or more metal elements selected from alkali metals, alkaline earth metals and rare earth metals. At this time, the metal element may be ytterbium.

(10) Counter electrode The counter electrode 20 is made of a translucent conductive material and is formed on the second functional layer 19. The counter electrode 20 functions as a cathode.

As the counter electrode 20, for example, a metal thin film or a transparent conductive film such as ITO or IZO can be used. In order to obtain the optical resonator structure more effectively, a metal thin film made of at least one of aluminum, magnesium, silver, aluminum-lithium alloy, magnesium-silver alloy and the like is formed as the material of the counter electrode 20. Is desirable. In this case, the film thickness of the metal thin film is preferably 5 nm or more and 30 nm or less. As a result, the counter electrode 20 becomes translucent, and an optical resonator structure can be constructed between the pixel electrode 13 and each reflecting surface of the counter electrode 20, so that the luminous efficiency can be further improved.

When the optical resonator structure as described above is adopted, a transparent conductive film such as ITO or IZO is formed between the second functional layer 19 and the counter electrode 20 with a desired film thickness, and the light emitting layer 17 is formed. It is desirable to adjust the optical distance between the and the counter electrode 20 to an appropriate size.

Further, a transparent conductive film such as ITO or IZO may be formed on the counter electrode 20 to adjust the chromaticity and the viewing angle.

(11) Sealing layer The sealing layer 21 prevents organic layers such as the hole transport layer 16, the light emitting layer 17, and the second functional layer 19 from being exposed to moisture or air and deteriorating. It is provided for this purpose.

The sealing layer 21 is formed by using a translucent material such as silicon nitride (SiN) or silicon oxynitride (SiON).

(12) Others Although not shown in FIG. 3, a polarizing plate for antiglare or an upper substrate may be attached onto the sealing layer 21 via a transparent adhesive. Further, a color filter for correcting the chromaticity of the light emitted by each organic EL element 2 may be attached. As a result, the hole transport layer 16, the light emitting layer 17, the second functional layer 19, and the like can be further protected from external moisture, air, and the like.

3. 3. Manufacturing Method of Organic EL Element The manufacturing method of the organic EL element 2 according to the embodiment will be described below with reference to FIGS. 6 to 10. 6 is a flowchart showing the manufacturing process of the organic EL element 2, and FIGS. 7 to 10 are cross-sectional views schematically showing the manufacturing process of the organic EL element 2.

(1) Substrate Preparation Step First, as shown in FIG. 7A, a TFT layer 112 is formed on the substrate 111 to prepare the substrate 11 (step S1 in FIG. 6). The TFT layer 112 can be formed by a known method for manufacturing a TFT.

(2) Interlayer Insulation Layer Forming Step Next, as shown in FIG. 7B, the interlayer insulation layer 12 is formed on the substrate 11. (Step S2 in FIG. 6).

Specifically, a resin material having a constant fluidity is applied, for example, by a die coating method so as to fill the unevenness on the substrate 11 by the TFT layer 112 along the upper surface of the substrate 11. As a result, the upper surface of the interlayer insulating layer 12 has a flattened shape along the upper surface of the base material 111.

Further, a contact hole (not shown) is formed in the interlayer insulating layer 12 by performing a dry etching method on a portion of the TFT element, for example, on the source electrode. The contact hole is formed by patterning or the like so that the surface of the source electrode is exposed at the bottom thereof.

Next, a connection electrode layer is formed along the inner wall of the contact hole. A part of the upper part of the connection electrode layer is arranged on the interlayer insulating layer 12. For the formation of the connection electrode layer, for example, a sputtering method can be used, and after forming a metal film, patterning may be performed using a photolithography method and a wet etching method.

(3) Pixel Electrode Forming Step Next, as shown in FIG. 7 (c), the pixel electrode material layer 130 is formed on the interlayer insulating layer 12. The pixel electrode material layer 130 can be formed by, for example, a vacuum vapor deposition method, a sputtering method, or the like.

Then, as shown in FIG. 7D, the pixel electrode material layer 130 is patterned by etching to form a plurality of pixel electrodes 13 partitioned by sub-pixels (step S3 in FIG. 6).

(4) Bank / Pixel Restriction Layer Forming Step Next, the bank 14 and the pixel regulation layer 141 are formed (step S4 in FIG. 6).

In the present embodiment, the pixel regulation layer 141 and the bank 14 are formed in separate steps.

(4-1) Formation of Pixel Restriction Layer First, in order to partition the pixel electrode array in the Y direction (FIG. 2) for each sub-pixel, a pixel regulation layer 141 extending in the X direction is formed.

As shown in FIG. 8A, a photosensitive resin material used as a material for the pixel regulation layer 141 is uniformly applied onto the interlayer insulating layer 12 on which the pixel electrode 13 is formed, and the pixel regulation layer material layer is formed. Form 1410. The amount of the resin material applied at this time is determined in advance so that the film thickness of the target pixel regulation layer 141 is obtained after drying.

As a specific coating method, for example, a wet process such as a die coating method, a slit coating method, or a spin coating method can be used. After coating, for example, vacuum drying and low-temperature heat drying (pre-baking) at about 60 ° C. to 120 ° C. are performed to remove unnecessary solvents, and the pixel-regulating layer material layer 1410 is fixed to the interlayer insulating layer 12. preferable.

Then, the pixel regulation layer material layer 1410 is patterned by using a photolithography method.

For example, when the pixel regulation layer material layer 1410 has positive photosensitivity, the portion to be left as the pixel regulation layer 141 is shielded from light, and the portion to be removed is transparent through a photomask (not shown). 1410 is exposed.

Next, the pixel regulation layer 141 can be formed by developing and removing the exposed region of the pixel regulation layer material layer 1410. As a specific developing method, for example, the entire substrate 11 is immersed in a developing solution such as an organic solvent or an alkaline solution that dissolves a portion exposed by exposure of the pixel regulation layer material layer 1410, and then a rinsing solution such as pure water is used. The substrate 11 may be washed with.

Then, by firing (post-baking) at a predetermined temperature, a pixel regulation layer 141 extending in the X direction can be formed on the interlayer insulating layer 12 (FIG. 8 (b)).

(4-2) Bank formation Next, the bank 14 extending in the Y direction is formed in the same manner as the pixel regulation layer 141.

That is, the bank material layer 140 is formed by applying a bank resin material on the interlayer insulating layer 12 on which the pixel electrode 13 and the pixel regulation layer 141 are formed by using a die coating method or the like (FIG. 8 (FIG. 8). c)). The amount of the resin material applied at this time is determined in advance so that the height of the target bank 14 is reached after drying.

Then, after patterning the bank 14 extending in the Y direction on the bank material layer 140 by a photolithography method, the bank 14 is formed by firing at a predetermined temperature (FIG. 8 (d)).

In the above, the material layers of the pixel regulation layer 141 and the bank 14 are formed by a wet process and then patterned, but one or both of the material layers are formed by a dry process and a photolithography method is performed. The patterning may be performed by the etching method.

(5) Fourth functional layer (hole injection layer, hole transport layer) forming step The fourth functional layer forming step includes the formation of the hole injection layer 15 and the formation of the hole transport layer 16 (step S5 in FIG. 6). ..

First, the hole injection layer 15 ejects ink containing a conductive polymer material such as PEDOT: PSS (mixture of polythiophene and polystyrene sulfonic acid) from the nozzle 3011 of the coating head 301 of the printing apparatus into the opening 14a. It is formed by coating, volatilizing and / or firing the solvent.

The hole transport layer 16 is formed by applying an ink containing the constituent material of the hole transport layer 16 on the hole injection layer 15 and then volatilizing and removing the solvent and / or firing. Examples of the constituent material of the hole transport layer 16 include polyfluorene and its derivatives, or polymer compounds such as polyarylamine and its derivatives, which do not have a hydrophilic group. The coating method is the same as in the case of the hole injection layer 15.

Note that FIG. 9A shows a schematic cross-sectional view of the display panel 10 when the hole transport layer 16 is formed after the hole injection layer 15 is formed.

(6) Organic Light Emitting Material Layer Forming Step Next, above the hole transport layer 16, the organic light emitting material layers 170 (R), 170 (G), 170 (B) (hereinafter, each) are used as precursors of the light emitting layer 17. The emission color is not distinguished, and simply “organic light emitting material layer 170”) is formed (step S6 in FIG. 6).

Specifically, as shown in FIG. 9B, an ink containing an organic light emitting material which is a constituent material of an organic light emitting layer of a light emitting color corresponding to each opening 14a is applied to a nozzle 3011 of a coating head 301 of a printing apparatus. The organic solvent in the ink is evaporated by sequentially ejecting from the ink and applying it on the hole transport layer 16 in the opening 14a, carrying the substrate 11 after applying the ink into a vacuum drying chamber and heating it in a vacuum environment. .. As a result, the organic light emitting material layer 170 can be formed.

(7) Hole Block / Electron Transport Layer 18 (First Functional Layer) Formation Step As shown in FIG. 10 (a), electron transportability is performed on the organic light emitting material layer 170 and the bank 14 by a vacuum deposition method or the like. A first organic material having at least one of the electron-injectable properties and having a hole-blocking property and sodium fluoride are co-deposited using a vacuum deposition method to obtain a film thickness of 1 nm or more and 10 nm or less, for example. A hole block / electron transport layer 18 is formed by forming a film with a film thickness of 5 [nm] (step S7 in FIG. 6). The hole block / electron transport layer 18 is formed by forming a film in common with each sub-pixel.

(8) Electron Transport Layer 191 (Second Functional Layer) Formation Step As shown in FIG. 10 (b), at least one of electron transport property and electron injection property is provided on the hole block / electron transport layer 18. An electron transport layer 191 is formed by forming a second organic material having a film thickness of 5 nm or more and 30 nm or less, for example, a film thickness of 10 [nm] by a vacuum deposition method (step S9 in FIG. 6). At this time, the film formation of the electron transport layer 191 does not contain one or more metal elements M1 selected from alkali metals, alkaline earth metals, and rare earth elements and having a reducing property for metal fluorides such as sodium fluoride. A second organic material is deposited on the surface. The electron transport layer 191 is formed by forming a film in common with each sub-pixel.

(9) Electron Injection Transporting Layer 192 (Third Functional Layer) Forming Step As shown in FIG. 10 (c), the electron transporting layer 191 has at least one property of electron transporting property and electron injecting property. The organic material of 2 and the metal element M2 which is a dope metal are co-deposited by a vacuum vapor deposition method to form a film with a film thickness of 5 nm or more and 50 nm or less, for example, a film thickness of 10 nm [nm], and an electron injection transport layer is formed. The concentration forming 192 is such that the weight content ratio of the doped metal is 3 wt or more and 60 wt%, for example, 10 wt%. Further, a metal thin film selected from alkali metals, alkaline earth metals, and rare earth elements may be used. In that case, the film thickness is 0.1 nm or more and 5 nm or less, for example, 1 nm to form the electron injection transport layer 192 (step S9 in FIG. 6). The electron injection transport layer 192 is formed by forming a film in common with each sub-pixel.

(10) Counter electrode forming step Next, the counter electrode 20 is formed on the functional layer 19 (step S10 in FIG. 6).
In the counter electrode forming step, first, silver, aluminum, or the like is formed on the functional layer 19 by a sputtering method or a vacuum vapor deposition method (FIG. 10 (d)).

(11) Sealing layer forming step Next, as shown in FIG. 10E, the sealing layer 21 is formed on the counter electrode 20 (step S11 in FIG. 6). The sealing layer 21 can be formed by forming a film of SiON, SiN, or the like by a sputtering method, a CVD method, or the like.

As described above, the display panel 10 shown in FIG. 3 is manufactured. The above manufacturing method is merely an example and can be appropriately changed according to the purpose.

4. Experimental results of luminous efficiency and drive voltage using the organic EL element 2 First, in the organic EL element 2, the weight ratio of sodium fluoride in the hole block / electron transport layer is different, and the drive voltage and the drive voltage when a predetermined voltage is applied are different. Luminous efficiency was measured. Table 1 shows the measurement results of the drive voltage and the luminous efficiency. The drive voltage reduction rate and the luminous efficiency in Table 1 are relative values based on a sample having a weight ratio of sodium fluoride of 0%.

As a test sample, a sample with the following specifications was used.

No. 1: In the laminated structure of the organic EL element 2, the adjacent layer (hole block / electron transport layer 18) on the cathode side of the light emitting layer 17 is changed to a hole block layer having a sodium fluoride weight ratio of 0%. 2: In the laminated structure of the organic EL element 2, the sample No. 1 in which the weight ratio of sodium fluoride in the hole block / electron transport layer 18 is 30 wt%. 3: In the laminated configuration of the organic EL element 2, a sample in which the adjacent layer (hole block / electron transport layer 18) on the cathode side of the light emitting layer 17 is changed to an intermediate layer in which the weight ratio of sodium fluoride is 100%. No. The laminated structure and film thickness in 1-3 are the hole injection layer [50 nm], the hole transport layer [20 nm], the light emitting layer [85 nm], the adjacent layer [5 nm] on the cathode side of the light emitting layer, the electron transport layer [10 nm], and the like. An electron injection transport layer [1 nm] was used as a counter electrode. The drive voltage is an applied voltage at a current density of 1 mA / cm ² , and the drive voltage reduction rate is [drive voltage before change] / [drive voltage after change].

As shown in Table 1, the drive voltage reduction rate and the luminous efficiency were in the order of sample 2> sample 3> sample 1 from the largest measured value. Specifically, Sample 1 having a weight ratio of sodium fluoride of 0% had a high hole blocking property but a low electron injecting property, so that the carrier balance in the light emitting layer was poor, resulting in the lowest luminous efficiency. Further, the sample 3 having a weight ratio of 100% has lower hole blocking property than the sample 1, but has improved electron injection property, so that the drive voltage reduction rate and the luminous efficiency are improved by about 5% and 18%, respectively. It was observed.

On the other hand, in the sample 3 having a weight ratio of 30%, the drive voltage reduction rate and the luminous efficiency were improved by 15% and 40%, respectively, as compared with the sample 1. In Sample 3, a small amount of sodium fluoride is obtained by mixing 30% by weight of sodium fluoride with the first organic material having at least one of electron transporting property and electron injecting property and having hole blocking property. The electric field is concentrated on the surface to improve the electron injection property, and at least the hole blocking property of the first organic material improves the carrier balance in the light emitting layer. It is probable that the luminous efficiency increased.

Next, in the organic EL element 2, the weight ratio of sodium fluoride in the hole block / electron transport layer 18 was changed stepwise, and the relationship between the weight ratio, the drive voltage reduction rate, and the luminous efficiency was investigated. FIG. 11 is an experimental result showing the relationship between the weight ratio of sodium fluoride in the hole block / electron transport layer 18 and the luminous efficiency in the organic EL element 2. The drive voltage reduction rate and the luminous efficiency in FIG. 11 are relative values based on the measured values at a weight ratio of sodium fluoride of 0%.

The test sample is a sample in which an intermediate layer having a weight ratio of sodium fluoride of 0, 10, 30, 50, 70, 100 wt% is arranged on the adjacent layer on the cathode side of the light emitting layer 17 in the organic EL element 2. Laminated structure and film thickness in each sample. The drive voltage reduction rate is also the same.

As shown in FIG. 11, in the range of the weight ratio of sodium fluoride in the hole block / electron transport layer 18 exceeding 0% and 70 wt% or less, the luminous efficiency and the driving voltage decrease rate are steeper than in the other ranges. There was a significant increase.

Further, in the range of 5% to 70 wt%, the luminous efficiency increased to about 19% or more, and the drive voltage reduction rate increased to about 7% or more.

Further, in the range of 10% to 50 wt%, a peak region B in which the luminous efficiency was about 37% or more and the drive voltage reduction rate was about 13% or more was confirmed.

In the peak region B, it is considered that the drive voltage is lowered due to the improvement of the carrier balance with the increase of the exciton density in the light emitting layer because the hole blocking property is higher than that in the case where the weight ratio exceeds 50%. Further, in the peak region B, it is considered that the electron injection property is higher than that in the case where the weight ratio is less than 10%, the carrier balance of the light emitting layer is improved, and the drive voltage is lowered. It is considered that the carrier balance is improved and the luminous efficiency is increased due to the high hole blocking property and electron injection property.

Further, when the weight ratio of sodium fluoride exceeds 50%, the drive voltage reduction rate and the luminous efficiency increase as compared with the case where the weight ratio is less than 10%. It is considered that the electron injecting property has a greater influence than the hole blocking property.

In the conventional organic EL element 2X, as described above, the intermediate layer composed of a layer made of a metal compound such as sodium fluoride is a metal element M2 contained in an adjacent electron transport layer, for example, barium, cesium, or the like. Fluoride of the alkali metal in the intermediate layer is reduced by lithium or the like and partially dissociated into the alkali metal, thereby increasing the electron mobility.

On the other hand, in the organic EL element 2, the electron transport layer 191 does not contain metal elements such as alkali metals, alkaline earth metals, and rare earth elements, which have a reducing property for metal fluorides such as sodium fluoride. , Sodium fluoride does not dissociate. Therefore, sodium fluoride exists as a compound in the whole block / electron transport layer 18. In the organic EL element 2, the reason why the drive voltage lowering property and the luminous efficiency are increased in the peak region B is that the sodium fluoride in the first organic material is locally present, so that the sodium fluoride is locally present. It is considered that this is because the electric field concentration is generated and the electron injection property is improved due to the tunnel phenomenon, and the carrier balance of the light emitting layer is improved. On the other hand, according to the study of the inventor, the organic EL element 2 is improved in the driving voltage lowering property and the luminous efficiency as compared with the conventional organic EL element 2X. Therefore, the dissociation of sodium fluoride in the organic EL element 2 is observed. It is considered that the prevention of the above and the presence of sodium fluoride as a compound also contributes to the suppression of the decrease in hole blocking property.

Regarding the tunnel phenomenon in organic EL devices, "Bright high efficiency blue organic light-emitting diodes with Al ₂ O ₃ / Al cathodes" H. Tang, et al (Applied Physics Letters, November 3, 1997, Volume 71, Issue) 18, pp. 2560-2562), by using an aluminum film having an insulator _{layer made of Al 2} O ₃ on the electron transport layer side for the cathode that injects electrons into the electron transport layer _{, Al 2} O It is disclosed that electrons are injected into the electron transport layer by the tunnel phenomenon through the layer _{3 to improve the current injection efficiency.}

5. Summary As described above, in the embodiment of the present disclosure, the organic EL element 2 is arranged on the light emitting layer 17 containing the organic light emitting material arranged above the pixel electrode 13 and the light emitting layer 17, and has electron transportability and electron transportability. On the first functional layer 18 and the first functional layer 18 formed by mixing a first organic material having at least one of the electron-injectable properties and having a hole-blocking property and sodium fluoride. Arranged, containing a second organic material having at least one of electron transporting and electron injecting properties, selected from alkali metals, alkaline earth metals, and rare earth elements, with respect to metal fluorides such as sodium fluoride. A second functional layer 191 that does not contain one or more reducing metal elements M2 and a counter electrode 20 arranged above the functional layer are provided.

Further, the metal element M2 may be composed of one or more metal elements selected from barium, lithium, cesium, and ytterbium.

With this configuration, the metal element M1 having a reducing property for metal fluoride such as sodium fluoride spreads to the hole block / electron transport layer 18, and the fluoride of the alkali metal in the hole block / electron transport layer 18 is reduced. Therefore, it is possible to prevent partial dissociation into the alkali metal and prevent the hole blocking property from being lowered. At the same time, the electron injection property into the light emitting layer 17 can be improved. As a result, the hole blocking property and the electron injecting property can be ensured, the carrier balance in the light emitting layer can be improved, and the luminous efficiency can be improved.

In the conventional organic EL element 2X, as described above, the intermediate layer composed of a layer made of a metal compound such as sodium fluoride is a metal element M2 contained in an adjacent electron transport layer, for example, barium, cesium, lithium or the like. As a result, the fluoride of the alkali metal in the intermediate layer was reduced and partially dissociated into the alkali metal, thereby enhancing the electron injectability.

On the other hand, in the organic EL element 2, as described above, the metal element M1 having a reducing property for metal fluoride such as sodium fluoride is not present in the electron transport layer 191 and is therefore included in the electron injection transport layer 192. The structure is such that the influence of M2 such as a metal element does not spread to the sodium fluoride in the hole block / electron transport layer 18. Therefore, the content of M2 such as a metal element contained in the electron injection transport layer 192 can be optimally set with respect to the electron injection property and the electron transport property in the electron injection transport layer 192. It is not necessary to determine the content of M2 such as a metal element in consideration of the reducing property of the fluoride of the alkali metal in the intermediate layer, and the electron injection property and the electron transport property in the electron injection transport layer 192 can be further enhanced.

≪Modification example≫
Although the organic EL element 2 and the like according to the embodiment have been described above, the present invention is not limited to the above embodiment except for its essential characteristic components. For example, it is realized by arbitrarily combining the components and functions in each embodiment within the range obtained by applying various modifications to each embodiment and the gist of the present invention. Forms are also included in the present invention. Hereinafter, as an example of such a form, a modified example of the organic EL element and the organic EL display panel will be described.

(1) The organic EL device according to the embodiment has a configuration in which a hole injection layer and a hole transport layer are present between the pixel electrode and the light emitting layer, but the present invention is not limited to this. For example, a configuration in which a hole transport layer or a hole transport layer exists may exist without using the hole injection layer and the hole transport layer. Further, a configuration may include any one of a hole injection layer, a hole transport layer, and an electron injection transport layer, or a configuration including a plurality or all of them at the same time. Further, all of these layers do not have to be made of an organic compound, and may be made of an inorganic substance or the like.

(2) In the display panel 10 according to the above embodiment, as shown in FIG. 2, the stretching direction of the pixel regulation layer 141 is the long axis X direction of the display panel 10, and the stretching direction of the bank 14 is the short axis of the display panel 10. Although it was in the Y direction, the stretching directions of the pixel restricting layer 141 and the bank 14 may be opposite. Further, the stretching direction of the pixel insulating layer and the bank may be a direction irrelevant to the shape of the display panel 10.

Further, in the display panel 10 according to the above embodiment, the image display surface is rectangular as an example, but the shape of the image display surface is not limited and can be changed as appropriate.

Further, in the display panel 10 according to the above embodiment, the pixel electrode 13 is a rectangular flat plate-shaped member, but the present invention is not limited to this.

Further, although the line bank type organic EL display panel has been described in the above embodiment, it may be a so-called pixel bank type display panel in which each sub-pixel is surrounded by banks on all four sides. ..

(3) In the above embodiment, all of the hole injection layer 15, the hole transport layer 16, and the light emitting layer 17 are formed by a printing method (coating method), but only one of them is used as a coating film formed by the printing method. May be good. In the finished product of the display panel 10, whether or not a specific layer is a coating film can be easily determined by detecting the water content or solvent remaining on the film.

(4) In the above embodiment, the hole injection layer 15 is formed by a printing method using an ink containing a conductive polymer material, but a transition metal oxide may be formed by a vapor deposition method or a sputtering method. Good. Since the oxide of the transition metal has a plurality of oxidation numbers, it is possible to take a plurality of levels, and as a result, the injection of holes can be facilitated and the driving voltage can be reduced. Tungsten oxide is suitable as such a metal oxide.

As a result, the hole injection amount can be increased in accordance with the increase in the electron injection amount, the carrier balance can be achieved in a state where the exciton amount is larger, and further improvement in luminous efficiency can be expected.

In this case, the metal material layer of the pixel electrode and the tungsten oxide layer are first laminated, and then patterning is performed using a photolithography method and a wet etching method to form the pixel electrode 13 and the hole injection layer 15 at the same time. After that, the manufacturing process can be simplified by forming the bank 14 and the pixel regulation layer 141.

(5) In the display panel 10 according to the above embodiment, sub-pixels 100R, 100G, and 100B that emit light in R, G, and B colors are arranged, but the emission color of the sub-pixels is not limited to this, for example. , R, G, B and may be four colors of yellow (Y). Further, in one pixel P, the number of sub-pixels is not limited to one per color, and a plurality of sub-pixels may be arranged. Further, the arrangement of the sub-pixels in the pixel P is not limited to the order of red, green, and blue as shown in FIG. 2, and may be in the order in which these are interchanged.

(6) Further, the display panel 10 according to the above embodiment adopts an active matrix method, but the present invention is not limited to this, and a passive matrix method may be adopted.

Further, it can be applied not only to the top emission type organic EL display panel but also to the bottle emission type organic EL display panel.

In the case of the bottom emission type, the counter electrode 20 is a light-reflecting anode, and the pixel electrode 13 is made of a light-transmitting (including semi-light-transmitting) material to serve as a cathode. The stacking order of the other first functional layer 22, the intermediate layer 18, the second functional layer 19, and the like is also different accordingly.

It can also be applied to a self-luminous display panel such as a quantum dot display device using a colloidal quantum dot (Quantum Dot).

≪Supplement≫
Each of the embodiments described above shows a preferable specific example of the present invention. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, processes, order of processes, etc. shown in the embodiments are examples, and are not intended to limit the present invention. Further, among the components in the embodiment, the steps not described in the independent claims showing the highest level concept of the present invention will be described as arbitrary components constituting the more preferable form.

Further, the order in which the above steps are executed is for exemplifying for the purpose of specifically explaining the present invention, and may be an order other than the above. Further, a part of the above steps may be executed at the same time (parallel) with other steps.

Further, for the sake of easy understanding of the invention, the scale of the component of each figure given in each of the above embodiments may be different from the actual scale. Further, the present invention is not limited to the description of each of the above embodiments, and can be appropriately modified without departing from the gist of the present invention.

Further, at least a part of the functions of each embodiment and its modifications may be combined.

Further, the present invention also includes various modifications in which modifications within the range that can be conceived by those skilled in the art are made to the present embodiment.

The organic EL element and the like according to the present disclosure are, for example, a method for manufacturing an organic EL element and an organic EL panel used as various display devices, television devices, displays for portable electronic devices, etc. for home use, public facilities, or business use. Etc., it can be suitably used.

1 Organic EL display device 2 Organic EL element 10 Organic EL panel 11 Substrate 12 Interlayer insulation layer 13 Pixel electrode (anode)
15 hole injection layer 16 hole transport layer 17 light emitting layer 170 organic light emitting material layer 18 hole block / electron transport layer (first functional layer)
19 Electron transport layer / Electron injection transport layer 191 Electron transport layer (second functional layer)
192 Electron injection transport layer (third functional layer)
20 Opposite electrode (cathode)
21 Sealing layer 23 Transparent conductive film

Claims (20)

With pixel electrodes,
A light emitting layer containing a light emitting material arranged above the pixel electrode and
A first function formed by mixing a first organic material which is arranged above the light emitting layer, has at least one of electron transporting property and electron injecting property, and has hole blocking property, and metal fluoride. Layer and
A second organic material that is located above the first functional layer and has at least one of electron transporting and electron injecting properties, is selected from alkali metals, alkaline earth metals, and rare earth elements. A second functional layer containing no one or more metal elements having a reducing property with respect to the metal fluoride,
With the counter electrode arranged above the second functional layer,
Self-luminous element equipped with. The self-luminous element according to claim 1, wherein the metal fluoride is a fluoride of an alkali metal, an alkaline earth metal, and a rare earth element. The self-luminous device according to claim 1 or 2, wherein the metal fluoride is sodium fluoride. The self-luminous element according to any one of claims 1 to 3, wherein the metal element is one or more metal elements selected from barium, lithium, cesium, and ytterbium. The self-luminous element according to any one of claims 1 to 4, wherein the film thickness of the first functional layer is 1 nm or more and 10 nm or less. The self-luminous element according to any one of claims 1 to 5, wherein the first functional layer is a vapor-deposited film of the first organic material and sodium fluoride. The self-luminous device according to any one of claims 1 to 6, wherein the concentration of sodium fluoride contained in the first functional layer is 70 wt% or less. The self-luminous device according to claim 7, wherein the concentration of sodium fluoride contained in the first functional layer is 10 wt% or more and 50 wt% or less. The self-luminous element according to any one of claims 1 to 8, wherein the film thickness of the second functional layer is 5 nm or more and 30 nm or less. The self-luminous element according to any one of claims 1 to 9, wherein the film thickness of the first functional layer is equal to or less than the film thickness of the second functional layer. The self-luminous element according to any one of claims 1 to 10, wherein the absolute value of HOMO of the first organic material is 6.0 eV or more. The self-luminous device according to any one of claims 1 to 11, wherein the value of the triplet excitation level of the first organic material is 2.0 eV or more. Further, a third organic material having at least one of electron transporting property and electron injecting property, which is above the second functional layer and below the counter electrode, includes an alkali metal and an alkaline earth. The self-luminous element according to any one of claims 1 to 12, further comprising a third functional layer doped with one or more metal elements selected from metals and rare earth metals. Further, above the second functional layer and below the counter electrode, a third functional layer composed of one or more metal elements selected from alkali metals, alkaline earth metals and rare earth metals is provided. The self-luminous element according to any one of claims 1 to 12. The self-luminous element according to claim 13 or 14, wherein the metal element contained in the third functional layer is ytterbium. The self-luminous element according to any one of claims 1 to 14, wherein the pixel electrode is light reflective and the counter electrode is semipermeable. Any of claims 1 to 16, wherein a fourth functional layer containing an organic material having at least one of hole transportability and hole injection property is provided above the pixel electrode and below the light emitting layer. The self-luminous element according to item 1. The self-luminous element according to claim 17, wherein the film thickness of at least one of the light emitting layer and the fourth functional layer differs depending on the wavelength of the light emitted by the light emitting layer. The self-luminous element according to claim 17 or 18, wherein at least one of the light emitting layer and the fourth functional layer is a coating film. A plurality of self-luminous elements according to any one of claims 1 to 19 are arranged in a matrix on the substrate, and the light emitting layers in the self-luminous elements adjacent to each other in the row direction extend in the column direction. Self-luminous display panel separated by.

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