JP2021093525A - Self-luminous element and self-luminous display panel - Google Patents

Abstract

To secure a hole block property, an electron injection property, and environmental resistance to improve an element life.SOLUTION: A self-luminous element comprises: a pixel electrode; a luminous layer that is disposed above the pixel electrode and contains luminescent material; a first functional layer that is disposed on the luminous layer and is made from metal fluoride; a second functional layer that is disposed on the first functional layer, contains first organic material having at least one of an electron transport property and an electron injection property, and does not contain one or more metallic elements selected from an alkaline metal, alkaline earth metal, and rare earth elements and having a property of reducing metal fluoride; and a counter electrode disposed above the second functional layer.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 a hole in the light emitting layer. It is required to improve the carrier balance with electrons to improve the efficiency of the light emitting element and to extend the life of the light emitting element.

On the other hand, for example, in Patent Document 1, 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 provided in the electron transport layer. A light emitting device having improved electron injection property and device life by doping with the above has been proposed.

Further, Patent Document 2 proposes a light emitting device in which a hole block layer (HBL) is provided in an adjacent layer on the cathode side of the light emitting layer.

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

However, in the configuration described in Patent Document 1 in which an intermediate layer made of an 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 a sufficient device is used. Life is not obtained. Further, in the configuration described in Patent Document 2 in which the hole block layer is arranged as an 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 the water content in the light emitting layer and the like are low. There is a problem that the environmental resistance is low and the device life is short because the cathode penetrates into the electron transport layer.

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 secure hole blockability, electron injection property, and environmental resistance and improve the element life.

In order to solve the above problems, the self-luminous EL 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. A second function including a first functional layer made of metal fluoride and a first organic material arranged on the first functional layer and having at least one of electron transporting property and electron injecting property. A layer and a counter electrode arranged above the second functional layer are provided, and the second functional layer is selected from an alkali metal, an alkaline earth metal, and a rare earth element with respect to the metal fluoride. It is characterized in that it does not contain one or more metal elements having reducing properties.

In the self-luminous element and the self-luminous display panel according to one aspect of the present disclosure, hole blockability, electron injection property, and environmental resistance are ensured to improve the device life.

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 machine EL panel in the said organic EL display device. 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 block / electron transport layer, the light emitting layer, the electron transport layer, and the electron injection 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. 7. (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. (A) is a schematic diagram showing a laminated structure of the organic EL element 2Z according to the sample 3, and (b) is an operation explanatory view of the organic EL element 2Z. This is an experimental result showing the relationship between the film thickness of the hole block / electron transport layer (first functional layer) and the device life 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 injection transport layer in an organic EL element is appropriately balanced. (A) and (b) are schematic views showing the laminated structure of the conventional organic EL elements 2X and 2Y. (A) and (b) are operation explanatory views of the conventional organic EL elements 2X and 2Y.

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

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. 13 is a schematic view showing a state in which the energy levels of the hole transport layer, the light emitting layer, and the electron injection 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 injection transport layer. Then, the holes supplied from the hole transport layer side and the electrons supplied from the electron injection 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.

14 (a) and 14 (b) are the main parts (parts from the anode to the cathode: hereinafter, also referred to as "light emitting parts") of the conventional organic EL elements 2X and 2Y described in Patent Documents 1 and 2, respectively. 15 (a) and 15 (b) are schematic views showing the laminated structure of the organic EL elements 2X and 2Y, respectively.

In the organic EL element 2X, as shown in FIG. 14A, the hole injection layer 15, the hole transport layer 16, and the organic light emitting layer 17 (hereinafter, may be referred to as “light emitting layer 17”) are formed on the pixel electrode 13. A light emitting portion is formed by laminating an intermediate layer 18X, an electron injection transport layer 19X, and a counter electrode 20 made of a material having high electron injection properties. 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 the electron injection transport layer 19X adjacent to the cathode side is made of a doped alkali metal or A metal element M1 with a low work function selected from alkaline earth metals, such as barium, cesium, and lithium, reduces the fluoride of the alkali metal in the intermediate layer and partially dissociates the alkali metal. A configuration with improved electron injection is adopted.

In general, the organic layer 17 including the organic light emitting layer has a property of easily absorbing and permeating water. Further, the metal element M1 has an active property and tends to react with water in the light emitting layer 17 to deteriorate the characteristics and the device life.

On the other hand, in the organic EL element 2X, an intermediate layer 18X made of an alkali metal fluoride is provided between the electron injection transport layer 19X and the light emitting layer 17, and moisture and the like in the light emitting layer 17 are electron injection transport layer. While preventing penetration into 19X and improving environmental resistance, a part of the metal compound in the intermediate layer 18X is reduced by the metal element M1 contained in the electron injection transport layer 19X and partially dissociated into an alkali metal. By doing so, it is said that it has a function of improving the electron injection property from the intermediate layer 18X to the light emitting layer 17.

According to the study of the inventor, in this organic EL element 2X, as shown in FIG. 15A, 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 By adopting the above, the electron injection property into the light emitting layer 17 is improved, and the shortage of electrons in the light emitting layer 17 is suppressed.

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 described later is provided as an adjacent layer on the cathode side of the light emitting layer 17, the light emitting layer 17 is provided. There are not enough holes and excitons blocked from the electron injection transport layer 19X. 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 injection transport layer 19X, so that the blocking property of the intermediate layer 18X with respect to holes and excitons is lowered. Be done. If this hole blocking property is low, holes invade the electron injection transport layer 19X side and combine with electrons in the electron injection transport layer 19X to generate excitons, causing deterioration of the electron injection transport layer 19X and shortening the device life. descend. Further, if the blocking property for excitons is low, it is assumed that the excitons generated in the light emitting layer 17 diffuse to the electron injection transport layer 19X, causing deterioration of the electron injection transport layer 19X and shortening the device life.

Further, the presence of the metal compound in the intermediate layer 18X makes it possible to prevent the permeation of moisture and the like in the light emitting layer 17 into the electron injection transport layer 19X and enhance the environmental resistance. When a part of the metal compound is reduced by the metal element contained in the electron injection transport layer 19X, there is a concern that the metal compound is dissociated and the environmental resistance of the intermediate layer 18X is lowered.

On the other hand, in the organic EL element 2Y, as shown in FIG. 14B, the hole injection layer 15, the hole transport layer 16, the light emitting layer 17, the hole block layer 18Y (HBL), and the electron injection transport layer 19Y are on the pixel electrode 13. And the counter electrode 20 are laminated to form a light emitting portion.

In the organic EL element 2Y, as shown in FIG. 15B, by adopting the hole block layer 18Y having a larger absolute value of the HOMO level than the light emitting layer 17 as an adjacent layer on the cathode side of the light emitting layer 17, the light emitting layer 17 The movement of holes and excitons from the electron injection transport layer 19Y to the electron injection transport layer 19Y is blocked. This makes it possible to confine holes in the light emitting layer 17 and increase the ratio of holes bonded to electrons, and to efficiently convert exciton energy into light.

However, since the hole block layer 18Y made of an organic material has insufficient function of preventing the permeation of water and the like in the light emitting layer 17 into the electron injection transport layer 19Y and enhancing the environmental resistance, active electron injection is performed. It is assumed that the transport layer 19Y is deteriorated, and the device life is shortened due to a decrease in electron injection property and a deterioration in carrier balance.

In particular, a wet process (wet method) in which a solution containing an organic material and a solvent for forming an organic layer capable of reducing costs (hereinafter, simply referred to as "ink") is applied by a printing apparatus to form the organic layer is performed. In the organic EL element manufactured by using the organic EL element, the residual amount of water in the organic layer is much larger than that in the case of forming a film by a dry process (dry method) such as a vapor deposition method, so that the water in the lower organic layer is electron-injected. It is feared that it permeates the transport layer and reacts with the alkali metal or the like in the electron injection transport layer, resulting in a large deterioration in light emission characteristics. Therefore, in an element configuration in which the light emitting layer is made of a coating film, further improvement in environmental resistance has been required.

In order to solve the above problems, the inventor has diligently studied a laminated structure of an organic EL device that secures hole blockability, electron injection property, and environmental resistance and improves the device life, and relates to one aspect of the present disclosure. It came up with the idea of an organic EL element and an 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 a first light emitting element composed of a pixel electrode, a light emitting layer containing a light emitting material arranged above the pixel electrode, and a metal fluoride arranged on the light emitting layer. A functional layer, a second functional layer arranged on the first functional layer and containing a first organic material having at least one of electron transporting property and electron injecting property, and the second functional layer. A counter electrode arranged above the layer is provided, and the second functional layer is one or more metals selected from alkali metals, alkaline earth metals, and rare earth elements and having a reducing property with respect to the metal fluoride. It is characterized by containing no element. 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 such a configuration, a metal element having a reducing property for metal fluoride such as sodium fluoride spreads to the first functional layer, and the metal fluoride such as sodium fluoride constituting the first functional layer is reduced. It is possible to prevent partial dissociation of sodium, prevent deterioration of hole blocking property, and improve electron injection property from the first functional layer to the light emitting layer. As a result, the hole blocking property and the electron injecting property can be ensured, and the carrier balance in the light emitting layer can be improved.

Further, by preventing the dissociation of sodium fluoride in the first functional layer, it is possible to suppress the permeation of water in the light emitting layer into the second functional layer and improve the environmental resistance. As a result, in the self-luminous element and the self-luminous display panel, hole blockability, electron injection property, and environmental resistance can be ensured, and the element life 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.

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

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

With such a configuration, the device life can be sharply increased as compared with the range other than the above.

In another aspect, in any of the above embodiments, the film thickness of the first functional layer may be 1 nm or more and 5 nm or less.

With such a configuration, the device life 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 such a configuration, the metal element contained in the third functional layer (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 at the same time, It is possible to improve the electron injection property into the light emitting layer.

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, 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 second 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. It may be composed of the above metal elements. Further, the metal element contained in the third functional layer may be ytterbium.

With this configuration, the presence of a second functional layer (electron transport layer) that does not contain a metal element that has a reducing property for metal fluoride such as sodium fluoride causes the third functional layer (electron injection transport layer) to have. The structure is such that the influence of the contained metal elements and the like does not spread to the sodium fluoride in the first functional layer. Therefore, the content of the metal element or the like 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 metal elements and the like in the third functional layer in consideration of the reducing property of sodium fluoride in the first functional layer, and the electron injectability and electron transport property in the third functional layer are further improved. It can be further enhanced.

In another aspect, in any of the above embodiments, the metal element contained in the third functional layer may have a different constitution from the metal element contained in the first functional layer.

With such a configuration, a first functional layer made of sodium fluoride can be realized.

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, at least one of the hole injection property and the hole transport property from the pixel electrode is 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 the luminous efficiency can be expected to be improved.

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 12 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 element life.

<< 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 FIGS. 2 and 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 sequences CR, CG, and CB, a plurality of pixel regulation layers 141 that insulate the sub-pixels 100R, 100G, and 100B from each other 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 hole block / electron transport layer 18, the electron transport layer 191 and the electron injection transport layer 192, the counter electrode 20, and the sealing layer 21 are not formed for each pixel. It is commonly formed in a plurality of organic EL elements 2 included in the display panel 10.

(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, a molybdenum sulfide, copper, zinc, aluminum, stainless steel, a metal substrate such as magnesium, iron, nickel, gold, and silver, a semiconductor substrate such as gallium arsenic, and a plastic substrate. 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. As a result, it is possible to suppress a decrease in luminous efficiency and a decrease in device life.

The hole block / electron transport layer 18 is a first functional layer arranged adjacent to the cathode side of the light emitting layer 17 and in which metal fluoride, for example, sodium fluoride (NaF) is deposited by vapor deposition.

The hole block / electron transport layer 18 is formed of sodium fluoride having a predetermined film thickness, so that the electron transport property can be improved. Moreover, since sodium fluoride is not reduced by the metal element M1 and the metal element M2 described later, it exists as a compound in the hole block / electron transport layer 18. By preventing the dissociation of sodium fluoride in this way, it is possible to prevent a decrease in hole blocking property.

Further, the metal fluoride other than sodium 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.

The film thickness of the hole block / electron transport layer 18 is thicker than 0 nm and is 5 nm or less, more preferably 1 nm or more and 5 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 5 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 light emitting layer, the hole block / electron transport layer, the electron transport layer, and the electron injection 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 movement of holes and excitons from the light emitting layer 17 to the electron transporting layer 191 can be blocked. As a result, holes invade the electron injection transport layer 192 side and combine with electrons in the electron injection transport layer 192 to generate excitons, which causes deterioration of the electron injection transport layer 192 or in the light emitting layer 17. It is possible to prevent the generated excitons from diffusing into the electron injection transport layer 192, causing deterioration of the electron injection transport layer 192 and shortening the device life.

Further, as shown in FIG. 5B, a part of sodium fluoride in the hole block / electron transport layer 18 is reduced by the metal element contained in the electron injection transport layer 192, so that the metal compound is dissociated. It is possible to prevent deterioration of the hole block property and the environmental resistance of the hole block / electron transport layer 18.

Further, as described above, by setting the film thickness of the hole block / electron transport layer 18 to 5 nm or less, electron injection from the hole block / electron transport layer 18 into the light emitting layer 17 as shown in FIG. 5 (b). The sex can be improved. As a result, the electron injection property into the light emitting layer 17 is high, the carrier balance in the light emitting layer 17 is improved, so that the luminous efficiency can be increased and the current density required to secure a predetermined brightness is low. Therefore, it is possible to prevent the device life from being shortened.

(9) Electron transport layer, 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 first organic material having at least one of electron transport property and electron injection property. Examples of the first 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 is a metal fluoride in the hole block / electron transport layer 18 such as sodium fluoride. A configuration that does not contain one or more metal elements M1 having a reducing property with respect to the compound 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 constituting the hole block / electron transport layer 18 is reduced. Therefore, it is possible to prevent the alkali metal from being partially dissociated. 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.

Further, 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 metal element M2 in the hole block / electron transport layer 18 spreads. It is possible to prevent the fluoride of the alkali metal 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.

(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, low-work-function metal organic complexes such as lithium quinolinol, and the like 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 electron injection transport layer 192. 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 electron injection transport layer 192 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 deteriorates when organic layers such as the hole transport layer 16, the light emitting layer 17, the electron transport layer 191 and the electron injection transport layer 192 are exposed to moisture or air. It is provided to prevent this from happening.

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 electron transport layer 191 and the electron injection transport layer 192 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) Layer 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 layer 17 can be formed (step S6 in FIG. 6).

(7) Hole Block / Electron Transport Layer 18 (First Functional Layer) Formation Step As shown in FIG. 10A, sodium fluoride is deposited on the organic light emitting layer 17 and the bank 14 by a vacuum deposition method or the like. A hole block / electron transport layer 18 is formed by forming a film thickness thicker than 0 nm and 5 nm or less, more preferably 1 nm or more and 5 nm or less, for example, 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 first 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 S8 in FIG. 6). At this time, the film formation of the electron transport layer 191 contains one or more metal elements M1 selected from alkali metals, alkaline earth metals, and rare earth elements and having a reducing property with respect to the above metal fluoride, for example, sodium fluoride. The first organic material is deposited so that it does not exist. 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 having 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 Form 192 (step S9 in FIG. 6). The concentration 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.

As a result, the functional layer 19 is formed.

(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 Device Life and Drive Voltage Using Organic EL Element 2 In the organic EL element 2, the device life was measured by differently stacking the light emitting layer 17 to the counter electrode 20. Table 1 shows the measurement results of the device life. The element life in Table 1 is the light emission time until the brightness drops to 97% of the initial value, and is a relative value with respect to the sample 1.

供試サンプルとして、比較例に係るＮｏ．１〜３、実施例に係るサンプル４を用いた。以下に各サンプルの仕様を示す。図１１（ａ）はサンプル３に係る有機ＥＬ素子２Ｚの積層構造を示す模式図、（ｂ）は動作説明図である。なお、有機ＥＬ素子２Ｚでは、第２の機能層を電子輸送層１９１Ｚ、第３の機能層を電子注入輸送層１９２Ｚと表記している。

As a test sample, No. 1 according to a comparative example. Samples 1 to 3 and Examples were used. The specifications of each sample are shown below. FIG. 11A is a schematic view showing a laminated structure of the organic EL element 2Z according to the sample 3, and FIG. 11B is an operation explanatory view. In the organic EL element 2Z, the second functional layer is referred to as an electron transport layer 191Z, and the third functional layer is referred to as an electron injection transport layer 192Z.

No. 1: Organic EL element 2X shown in FIG. 14A: Sodium fluoride layer (NaF) on the cathode side adjacent layer of the light emitting layer 17, and metal element M1 having a reducing property on sodium fluoride on the cathode side adjacent layer. Sample No. 1 with an electron injection transport layer (EIL) made of an organic material doped with sodium fluoride. 2: Organic EL element 2Y shown in FIG. 14 (b): A hole block layer (HBL) is doped in the adjacent layer on the cathode side of the light emitting layer 17, and M2 such as a metal element that enhances electron transportability is doped in the adjacent layer on the cathode side. Sample No. 1 with an electron injection transport layer (EIL) made of organic material. 3: 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 the hole block layer (HBL). Sample No. 2 in which an electron transport layer (ETL) made of an organic material containing no metal element M1 having a reducing property for sodium fluoride was arranged between the injection transport layer (EIL). 4: In the laminated structure of the organic EL element 2, the laminated structure in which the thickness of the sodium fluoride layer of the adjacent layer (hole block / electron transport layer 18 (NaF)) on the cathode side of the light emitting layer 17 is 5 nm: hole block. A sample in which an electron transport layer (ETL) made of an organic material containing no metal element M1 having a reducing property against sodium fluoride is arranged between the electron transport layer 18 (NaF) and the electron injection transport layer (EIL). Sample No. The laminated structure and film thickness of 1 and 2 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, and the electron injection transport layer [1 nm]. , The counter electrode was used. In addition, sample No. The laminated structure and film thickness in 3 and 4 are such that an electron transport layer [10 nm] is provided between the adjacent layer on the cathode side of the light emitting layer and the electron injection transport layer.

As shown in Table 1, the device life was in the order of sample 4> sample 1> sample 2> sample 3 in descending order of value. Specifically, when the element life of the sample 1 is used as a reference, the element life of the sample 2 is about 3%, and the element life of the sample 3 is about 1%. Since the hole block layer in Samples 2 and 3 has high hole block property but low electron injection property, the device life is shortened due to deterioration of carrier balance, and water and the like in the light emitting layer 17 are transferred to the electron injection transport layer. It is considered that the function of preventing permeation and enhancing the environmental resistance is insufficient, which causes deterioration of the active electron injection transport layer and shortens the device life.

On the other hand, in Sample 4 according to the example, improvement in life was observed as compared with Samples 1 to 3.

The sample 4 according to the example showed a significant improvement in the device life as compared with the sample 3. That is, in sample 3, as shown in FIG. 11B, the hole block layer has insufficient function of preventing the permeation of water and the like in the light emitting layer 17 into the electron injection transport layer 192Z and enhancing the environmental resistance. Therefore, even when the electron transport layer 191Z does not contain the metal element M1, the element life is short. On the other hand, in Sample 4, it is presumed that the element life was extended because the sodium fluoride layer constituting the hole block / electron transport layer 18 had excellent environmental resistance.

Further, in the sample 4 according to the example, an improvement was observed in which the element life was increased to 204% as compared with the sample 1.

The reason for this is that in sample 4, the hole block / electron transport layer 18 is formed because the adjacent layer on the cathode side of the hole block / electron transport layer 18 does not contain the metal element M1 having a reducing property for sodium fluoride. It is probable that by preventing the dissociation of sodium fluoride, the deterioration of the hole blocking property could be prevented and the movement of holes and excitons could be blocked. As a result, holes invade the electron injection transport layer 192 side and combine with electrons in the electron injection transport layer 192 to generate excitons, which causes deterioration of the electron injection transport layer 192 or in the light emitting layer 17. It is possible to prevent the generated excitons from diffusing into the electron injection transport layer 192, causing deterioration of the electron injection transport layer 192 and shortening the device life.

Further, in sample 4, by preventing the dissociation of sodium fluoride in the hole block / electron transport layer 18, it is possible to suppress the permeation of water and the like in the light emitting layer 17 into the electron transport layer 191 and the electron injection transport layer 192. It is considered that the environmental resistance was improved as compared with Sample 1.

Next, in the organic EL device 2, the film thickness of the sodium fluoride layer of the hole block / electron transport layer 18 was changed stepwise, and the relationship between the film thickness and the device life was investigated. FIG. 12 is an experimental result showing the relationship between the film thickness of the hole block / electron transport layer 18 (first functional layer) and the device life in the organic EL element 2. The element life in FIG. 12 is a relative value based on the measured value in the sample 1 described above.

The test sample is a sample in which a sodium fluoride layer having a film thickness of 0.5, 1, 3, 5, 6, and 7 nm is arranged as a hole block / electron transport layer 18 in the organic EL element 2, and in each sample. The laminated structure, film thickness, and drive voltage reduction rate are also the same.

As shown in FIG. 12, in the range of the film thickness of the sodium fluoride layer constituting the hole block / electron transport layer 18 of 1 nm or more and 5 nm or less, a peak region in which the device life increases sharply is observed as compared with the other ranges. It was observed.

Further, in this example, a peak was observed in which the device life was further improved in the range larger than 3 nm and 5 nm or less.

The reason why the device life sharply decreases when the film thickness exceeds 5 nm is that at the beginning of the life, the electron injection property deteriorates due to the increase in the tunneling barrier due to the increase in the film thickness, and the hole block / electron transport layer 18 and the electrons. It is considered that electrons are accumulated at the interface with the transport layer and a strong electric field is applied, so that the load on the organic material of the electron transport layer is increased and the deterioration of the electron transport layer is accelerated. Then, it is presumed that the deterioration of the electron transport layer further deteriorates the electron injection property and promotes the shortening of the life.

Further, the reason why the device life is shortened when the film thickness is less than 1 nm is that it is difficult to form a uniform film in manufacturing, and the effect of the environmental resistance of the sodium fluoride layer in the hole block / electron transport layer 18 is lowered. Can be considered. Further, if the film thickness is less than 1 nm, it is considered that the hole blocking property is lowered, the carrier balance is deteriorated, and the device life is shortened.

In the experiment shown in FIG. 12, the drive voltage had the lowest film thickness of 5 nm and the best carrier balance was 5 nm. However, since the carrier balance varies depending on the structure of other layers in the laminated structure, for example, the electron / hole mobility in the light emitting layer, the hole injection layer, the constituent material of the hole transport layer, etc., the carrier balance is adjusted including these factors. By doing so, the film thickness having the best carrier balance can be adjusted as appropriate.

5. Experimental results of luminous efficiency and driving voltage using the organic EL element 2 The driving voltage and luminous efficiency were measured using samples 3 and 4 as test samples. Table 2 shows the measurement results of the drive voltage reduction rate and the luminous efficiency. The drive voltage is an applied voltage at a current density of 1 mA / cm ² , and is represented by a relative value as the drive voltage reduction rate in Table 2. The drive voltage reduction rate is [drive voltage before change] / [drive voltage after change]. The drive voltage reduction rate and the luminous efficiency in Table 2 are relative values with respect to the sample 3.

表２に示すように、実施例に係るサンプル４では、サンプル３に比べて、駆動電圧低下率、発光効率に、それぞれ、５％、１８％程度の改善が見られた。ホールブロック層を用いたサンプル３は、ホールブロック性は高いが電子注入性が低いために発光層におけるキャリアバランスが悪く発光効率が低い結果となった。これに対し、実施例に係るサンプル４では、サンプル３に比べて、電子注入性が高く、発光層のキャリアバランスの改善にして駆動電圧が低下したと考えられる。また、サンプル４では、ホールブロック性及び電子注入性が高いことにより、キャリアバランスが改善し発光効率が増加したと考えられる。

As shown in Table 2, in Sample 4 according to the example, improvement of about 5% and 18% was observed in the drive voltage reduction rate and the luminous efficiency, respectively, as compared with Sample 3. In Sample 3 using the hole block layer, the hole block property was high, but the electron injection property was low, so that the carrier balance in the light emitting layer was poor and the luminous efficiency was low. On the other hand, it is considered that the sample 4 according to the example has higher electron injection property than the sample 3, and the drive voltage is lowered due to the improvement of the carrier balance of the light emitting layer. Further, in Sample 4, it is considered that the carrier balance was improved and the luminous efficiency was increased due to the high hole blocking property and electron injection 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 M1 contained in an adjacent electron extraction transport layer, for example, barium. The fluoride of the alkali metal in the intermediate layer is reduced by cesium, lithium, etc., and the alkali metal is partially dissociated, thereby enhancing the electron injection property.

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, the sodium fluoride of the hole block / electron transport layer 18 exists as a compound. In the organic EL element 2, the reason why the drive voltage lowering property and the luminous efficiency are increased in the peak region (FIG. 12) is that the sodium fluoride in the first organic material is locally present in the sodium fluoride. It is considered that this is because the electric field concentration is locally 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 the 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, In 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} electrons by tunneling through the layer of O ₃ is injected into the electron transport layer, current injection efficiency is disclosed to be improved.

6. 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 is made of sodium fluoride. A first organic material arranged on the first functional layer (hole block / electron transport layer) 18 and the first functional layer 18 and having at least one property of electron transport property and electron injection property. A second functional layer (electron transport layer) 191 that contains, is selected from alkali metals, alkaline earth metals, and rare earth elements, and does not contain one or more metal elements M1 having a reducing property for metal fluorides such as sodium fluoride. And a counter electrode 20 arranged above the second functional layer.

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 sodium fluoride in the hole block / electron transport layer 18 is reduced. It is possible to prevent partial dissociation of sodium and prevent deterioration of hole blocking property. 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, and the carrier balance in the light emitting layer can be improved. Further, by preventing the dissociation of sodium fluoride in the hole block / electron transport layer 18, it is possible to suppress the permeation of water in the light emitting layer 17 into the electron injection transport layer 192 and improve the environmental resistance. As a result, in the organic EL device, hole blockability, electron injection property, and environmental resistance can be ensured, and the device life can be improved.

Further, the metal element M1 may be composed of one or more metal elements selected from barium, lithium, cesium, and ytterbium.

With such a configuration, it is possible to specifically realize an organic EL device that secures hole blockability and electron injection property, improves carrier balance in the light emitting layer, and improves device life.

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 M1 contained in the adjacent electron injection transport layer 19X, for example, barium, cesium, etc. Fluoride of the alkali metal in the intermediate layer is reduced by lithium or the like, and the alkali metal is partially dissociated, thereby enhancing the electron injection property.

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 alkali metal fluoride in the hole block / electron transport layer 18, and the electron injection property and the electron transport property in the electron injection transport layer 192 are further improved. Can be 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, the hole transport layer or the electron injection transport layer may be present 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 colloidal quantum dots (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 (17)

With pixel electrodes,
A light emitting layer containing a light emitting material arranged above the pixel electrode and
A first functional layer arranged on the light emitting layer and made of metal fluoride, and
A second functional layer arranged on the first functional layer and containing a first organic material having at least one of electron transporting property and electron injecting property.
A counter electrode arranged above the second functional layer is provided.
The second functional layer is a self-luminous element selected from alkali metals, alkaline earth metals, and rare earth elements, and does not contain one or more metal elements having a reducing property with respect to the metal fluoride. 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 5 nm or less. The self-luminous element according to claim 5, wherein the film thickness of the first functional layer is 1 nm or more and 5 nm or less. The self-luminous element according to any one of claims 1 to 6, 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 7, wherein the film thickness of the first functional layer is equal to or less than the film thickness of the second functional layer. Further, on the second functional layer and below the counter electrode, a second organic material having at least one of electron transporting property and electron injecting property is added to an alkali metal and an alkaline earth. The self-luminous element according to any one of claims 1 to 8, 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 8. The self-luminous element according to claim 9 or 10, wherein the metal element contained in the third functional layer is ytterbium. The self-luminous element according to any one of claims 1 to 9, wherein the metal element contained in the third functional layer is different from the metal element contained in the first functional layer. The self-luminous element according to any one of claims 1 to 12, wherein the pixel electrode is light reflective and the counter electrode is semipermeable. Any of claims 1 to 13, 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 14, 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 14 or 15, 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 16 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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