JP6799567B2 - Organic EL display panel and its manufacturing method, as well as organic EL display device and electronic equipment - Google Patents

Description

The present invention relates to a light emitting display panel in which light emitting elements are arranged and a method for manufacturing the same, and in particular, an organic EL display panel in which organic electroluminescent elements (hereinafter referred to as “organic EL elements”) are arranged in a matric manner and a method for manufacturing the same. The present invention relates to an organic EL display device and an electronic device using an organic EL display panel as an image display unit.

In recent years, as a light emitting type display, an organic EL display panel in which a plurality of organic EL elements are arranged along a matrix direction on a substrate has been put into practical use as a display of an electronic device. Each organic EL element has a basic structure in which a light emitting layer containing an organic light emitting material is arranged between a pair of electrode pairs of an anode and a cathode, and a voltage is applied between the pair of electrode pairs during driving to obtain an anode. This is a current-driven light emitting element generated by recombination of holes injected into the light emitting layer from the cathode and electrons injected into the light emitting layer from the cathode.

Since each organic EL element emits light by itself, the organic EL display panel has high visibility, and since it is a completely solid element, it has excellent impact resistance.
In an organic EL display panel, the light emitting layer is generally partitioned by a partition wall (bank) made of an insulating material for each EL element, and the light emitting layer is partitioned by the partition wall. Further, an organic layer such as a hole injection layer and a hole transport layer is interposed between the anode and the light emitting layer as needed. Further, an electron injection layer, an electron transport layer, and the like are also interposed between the cathode and the light emitting layer, if necessary.

In a full-color display organic EL display panel, such an organic EL element forms sub-pixels of each RGB color, and adjacent RGB sub-pixels are combined to form one pixel.
When forming the light emitting layer and the charge injection layer of each organic EL element, a partition wall separating the adjacent organic EL elements is formed on the substrate, and the organic layer is formed in each element forming region partitioned by each partition wall. A wet process (wet method) in which droplets of a solution containing an organic material and a solvent for forming a light emitting layer or the like (hereinafter, simply referred to as “ink”) is ejected from a nozzle and applied is often used (patented method). Reference 1).

According to this wet process, the organic layer and the light emitting layer can be formed relatively easily even in a large panel, and the material utilization efficiency is high, so that the cost is excellent.

International Publication WO2012 / 004823

By the way, the film thickness of the organic layer suitable for increasing the luminous efficiency of each organic EL element depends on the wavelength of the emitted color.
That is, since the optimum optical path length (resonance condition) in the organic EL element differs between red light, green light, and blue light due to the difference in wavelength, the organic layer is matched to the wavelength of the emitted color in each color sub-pixel. It is desirable to fine-tune the film thickness of the light to improve the luminous efficiency.

However, when the amount of ink dropped is actually adjusted in the wet process to form organic layers with different film thicknesses, the organic layers have different emission colors of sub-pixels due to the influence of the liquid repellency of the partition wall and the surface tension of the ink. It is difficult to align the film shapes, and the display image quality may deteriorate.
The present invention has been made in view of such a problem, and while forming an organic layer by a wet process and aligning the film shapes of the organic layers of each luminous color, the organic layer suitable for each luminous color An organic EL display panel that can secure the layer thickness of the above, improve the luminous efficiency, and suppress the possibility of deterioration of the display image quality, a method for manufacturing such an organic EL display panel, an organic EL display device, and an electronic device. The purpose is to provide.

The organic EL display panel according to one aspect of the present disclosure is an organic EL display panel including a substrate, an interlayer insulating layer formed on the substrate, and an organic EL light emitting portion formed on the interlayer insulating layer. The organic EL light emitting unit is arranged between a plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer and a plurality of partition walls extending in the column direction between the pixel electrodes adjacent to each other in the row direction. And an organic layer including a light emitting layer formed in a region partitioned by the partition wall, and a counter electrode formed above the organic layer, and the organic EL light emitting unit emits a first color. It includes a first light emitting unit having a light emitting layer and a second light emitting unit having a light emitting layer that emits a second color different from the first color, and the first light emitting unit and the second light emitting unit are of the organic layer. The layer thickness is different, and the amount of digging of the interlayer insulating layer in the region partitioned by the partition wall of the first light emitting portion and the second light emitting portion is different.

In addition, here, the description that "the amount of digging of the interlayer insulating layer in the region partitioned by the partition wall of the first light emitting part and the second light emitting part is different" is the light emitting part of one of the light emitting colors. Including the case where the amount of digging of the interlayer insulating layer in the region partitioned by the partition wall is “0”.
Further, the organic EL display device according to another aspect of the present disclosure includes the above-mentioned organic EL display panel and a driving unit for driving the organic EL display panel to display an image.

Further, the electronic device according to another aspect of the present disclosure includes the above-mentioned organic EL display device as an image display unit.
Further, the method for manufacturing an organic EL display device according to another aspect of the present disclosure includes a first step of preparing a substrate, a second step of forming an interlayer insulating layer on the substrate, and organic on the interlayer insulating layer. A method for manufacturing an organic EL display panel including a third step of forming an EL light emitting unit, wherein the organic EL light emitting unit includes a plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer and rows. A plurality of partition walls arranged between the pixel electrodes adjacent to each other in the direction and extending in the row direction, an organic layer including a light emitting layer formed in a region partitioned by the partition walls, and an organic layer formed above the organic layer. A first light emitting unit including a counter electrode and having a light emitting layer that emits a first color, and a second light emitting unit having a light emitting layer that emits a second color different from the first color. The layer thickness of the organic layer is different between the light emitting portion and the second light emitting portion, and in the second step, the interlayer insulating layer in the region partitioned by the partition wall of the first light emitting portion and the second light emitting portion is different. It is characterized by the formation of deep digging.

According to the organic EL display panel and the method for manufacturing an organic EL display panel according to the above aspect, even if an organic layer having a different layer thickness for each color is formed by a wet process, the film shape can be made substantially the same. It is possible to provide an organic EL display panel capable of displaying an image with less deterioration, an organic EL display device provided with such an organic EL display panel, and an electronic device.

It is a block diagram which shows the whole structure of the organic EL display device 1. It is a schematic plan view which enlarged a part of the image display surface of the organic EL display panel 10. It is a schematic cross-sectional view along the line AA of FIG. (A) to (f) are partial cross-sectional views schematically showing a manufacturing process of an organic EL element. (A) to (d) are partial cross-sectional views schematically showing the manufacturing process of the organic EL element following FIG. (A) to (d) are partial cross-sectional views schematically showing the manufacturing process of the organic EL element following FIG. It is a flowchart which shows the manufacturing process of an organic EL element. It is a graph which shows the measurement result of the film shape of the light emitting layer of each color in the manufacturing method of the organic EL element which concerns on embodiment. It is a graph which shows the measurement result of the film shape of the light emitting layer of each color when the height of a partition wall is 1.2 μm. It is a graph which shows the measurement result of the film shape of the light emitting layer of each color when the height of a partition wall is 0.5 μm. (A) to (c) are diagrams schematically showing the correlation between the distance from the pinning position to the substrate and the film shape of the finally formed light emitting layer. It is a schematic cross-sectional view for defining a flat part in the film shape of a light emitting layer. It is a figure which shows the relationship between the ink density and the height of the partition wall required when the light emitting layer of each color is formed with the ink density. (A) to (d) are schematic views for explaining a modification of the process of forming a digging in the interlayer insulating layer. (A) to (d) are schematic views for demonstrating another modification of the process of forming a digging in an interlayer insulating layer. (A) to (d) are schematic views showing the steps following the steps of FIG. It is a figure which shows the example of the television apparatus using the organic EL display panel which concerns on this embodiment. (A) and (b) are schematic diagrams for explaining that the film shape of the formed light emitting layer is different depending on the difference in the amount of ink dropped. It is a schematic diagram for demonstrating that the film shape of the formed light emitting layer can be made uniform even if there is a difference in the amount of dripping ink by this embodiment.

<< Background to one aspect of this disclosure >>
Conventionally, the organic light emitting layer in an organic EL display panel is often formed by a dry process (dry method) such as vacuum deposition, but in recent years, it has become wet due to advances in coating technology, especially printing equipment technology. Technology for forming an organic light emitting layer in a process is becoming widespread.
In the wet process, an ink in which an organic light emitting material is dissolved in an organic solvent is printed on a necessary place by a printing device or the like and then dried to form an organic light emitting layer. Even a large organic EL display panel can be used. This is because the equipment cost can be suppressed and the material utilization rate is high, which is excellent in terms of cost.

However, in order to construct the optical resonance structure in the wet process, it is necessary to adjust the dropping amount of the ink of each emission color in order to make the thickness of the organic emission layer of the organic EL element of each emission color different.
This causes a problem that it is difficult to align the profile of the surface of the organic light emitting layer after drying (hereinafter, referred to as “film shape”) between light emitting colors having different film thicknesses.

18 (a) and 18 (b) are cross-sectional views schematically showing a film shape forming process, FIG. 18 (a) shows a case where the film thickness of the light emitting layer is large, and FIG. 18 (b) shows a case where the film thickness is large. , The case where the film thickness of the light emitting layer is small is shown.
As shown in FIG. 18A, a pixel electrode 13 is formed on the interlayer insulating layer 12, and a pair of partition walls 14 having a predetermined height are erected on both sides so as to sandwich the pixel electrode 13.

The partition wall 14 is made of an organic material having a certain liquid repellency, and when ink is dropped between a pair of partition walls 14 (hereinafter, referred to as “opening”), the surface tension of the ink and the liquid repellency of the partition wall 14 are obtained. Depending on the nature, an upwardly raised ink pool 170 is formed. When the organic solvent in the ink sump 170 evaporates and dries, the film shape 171 of the light emitting layer comes into contact with the inner wall of the partition wall 14 at the pinning position P1 and becomes a concave shape recessed downward at the center of the opening.

On the other hand, when the film thickness of the light emitting layer is small, as shown in FIG. 18 (b), a smaller amount of ink than in the case of FIG. 18 (a) is dropped on the opening to form an ink pool 170. When this is dried, the film shape has a large difference between the pinning position P2 and the center of the opening as shown by the thick line 171 and becomes a steeper concave shape than in the case of FIG. 18A.
Such a phenomenon occurs because the distance from the top of the partition wall 14 at the pinning positions P1 and P2 in the direction perpendicular to the main surface of the interlayer insulating layer 12 hardly changes regardless of the amount of ink dropped.

The reason why there is no difference in the pinning position is that the contact angle between the ink and the partition wall 14 is kept within a predetermined range due to the relationship between the liquid repellency of the composition material of the partition wall 14 and the surface tension of the ink, and the vicinity of the partition wall 14 Since the organic solvent tends to evaporate and dry faster than the central portion, it is considered that the position (pinning position) of the film in contact with the partition wall 14 is fixed first.

In order to deal with this, (1) the partition wall 14 is configured to change the height between the side having a large film thickness and the side having a small film thickness (the height of the partition wall 14 on the side having a small film thickness is lowered), (2). ) It is conceivable that the inner wall surface of the partition wall 14 is surface-treated to change the degree of liquid repellency (wetting property) between the large film thickness side and the small film thickness side, but in the configuration (1), the top surface of the partition wall 14 is used. In order to provide the step, the width of the partition wall 14 has to be increased by design, and the area of the space (opening) sandwiched by the partition wall 14 is reduced by that amount, which may reduce the light emission efficiency. Further, regarding the configuration of (2), the partition wall 14 has also been miniaturized due to the recent high definition, and it is technically technical to apply different surface treatments to the side surface of the partition wall 14 corresponding to each sub-pixel having a different emission color. It is difficult, and even if it is possible, it is not realistic in terms of cost, and the merit of adopting the wet process is greatly diminished.

Therefore, the inventors of the present application do not change the pinning position for each emission color to align the film shapes of the light emitting layers having different film thicknesses, but conversely, the pinning position of the light emitting layer of each emission color does not change. This is one aspect of the present disclosure, which has been studied repeatedly on a method for aligning film shapes by utilizing the method.
19 (a) and 19 (b) are schematic views for explaining the basic principle of the present disclosure, and in this example, the height of the partition wall 14 is lower than that of FIG.

Then, the distance of the pinning position P3 from the top of the partition wall 14 is the same as that of the pinning positions P1 and P2, but the volume of the opening below the pinning position P3 is smaller, so that as shown in FIG. 19A. Even when the amount of ink dropped is small, the drop in the central portion is small when the ink is dried, and the concave shape of the film shape 171 is very gentle as compared with the case of FIG. 18B.

When the film thickness of the light emitting layer is large, the height of the partition wall 14 remains the same, and as shown in FIG. 19B, the interlayer insulating layer 12 is provided with the dug portion 125 having a depth of d1. The volume of the opening below the pinning position P4 is increased by the amount corresponding to the increased amount of ink.
As a result, even when the amount of ink dropped is larger than that in FIG. 19 (a), the amount of drop in the central portion when dried is about the same as in FIG. 19 (a), so that the film shape is the same as in FIG. 19 (a). It is almost the same as the case of FIG. 19B, and it is possible to align the film shapes of different emission colors.

That is, a digging corresponding to the difference in the amount of ink to be dropped is provided directly under the light emitting region of the opening of the partition wall, and the amount of ink existing above the assumed pinning position is the same in the sub-pixels of each light emitting color. The surface shape of the ink sump 170 immediately after dropping (see FIGS. 19A and 19B) is made to be substantially the same, but the film shape of the luminescent color having a different film thickness is formed. It was found that it is possible to align.

<< Outline of one aspect of the present disclosure >>
The organic EL display panel according to one aspect of the present disclosure is an organic EL display panel including a substrate, an interlayer insulating layer formed on the substrate, and an organic EL light emitting portion formed on the interlayer insulating layer. The organic EL light emitting unit is arranged between a plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer and a plurality of partition walls arranged in the row direction and extended in the column direction. And an organic layer including a light emitting layer formed in a region partitioned by the partition wall, and a counter electrode formed above the organic layer, and the organic EL light emitting unit emits a first color. It includes a first light emitting unit having a light emitting layer and a second light emitting unit having a light emitting layer that emits a second color different from the first color, and the first light emitting unit and the second light emitting unit are of the organic layer. The layer thickness is different, and the amount of digging of the interlayer insulating layer in the region partitioned by the partition wall of the first light emitting portion and the second light emitting portion is different.

According to this aspect, even if the film thickness of the organic layer of each emission color is different, the film shapes can be made uniform.
Further, in the organic EL display panel according to another aspect of the present disclosure, in the above aspect, of the first light emitting unit and the second light emitting unit, the light emitting unit having a longer wavelength of the light emitting color is the other light emitting unit. The amount of digging of the interlayer insulating layer is larger than that of the above.

As a result, it is possible to make the film shape of the organic layer of each emission color uniform while ensuring the layer thickness of the organic layer according to the wavelength of the emission color.
Further, in the organic EL display panel according to another aspect of the present disclosure, in the above aspect, the height of the pinning position where the upper surface of the organic layer and the partition wall in the first light emitting portion and the second light emitting portion are in contact with each other and the organic The height of the partition wall and the amount of digging of the interlayer insulating layer are set so that the difference from the height of the center position of the upper surface of the layer is equal to or less than a predetermined value.

Here, the difference between the height of the pinning position where the upper surface of the organic layer and the partition wall are in contact with each other and the height of the center position of the upper surface of the organic layer is 700 nm or less.
Further, it is desirable that the bottom surface of the dug portion of the interlayer insulating layer is flat.
According to this aspect, the film shape of the organic layer between each emission color can be made uniform with many flat portions and a high aperture ratio.

Further, in the organic EL display panel according to another aspect of the present disclosure, in the above aspect, the pixel electrode is made of a metal thin film having light reflectivity.
According to this aspect, it is possible to construct a suitable optical resonance structure in each of the first and second light emitting portions having different light emitting colors to improve the luminous efficiency.
Further, the organic EL display device according to another aspect of the present disclosure includes an organic EL display panel according to each of the above aspects and a driving unit that drives the organic EL display panel to display an image.

Further, the electronic device according to another aspect of the present disclosure includes the organic EL display device as an image display unit.
According to this aspect, it is possible to display a high-quality image in which the luminous efficiency of the emitted color is stable.
Further, the method for manufacturing an organic EL display panel according to another aspect of the present disclosure includes a first step of preparing a substrate, a second step of forming an interlayer insulating layer on the substrate, and an organic EL on the interlayer insulating layer. A method for manufacturing an organic EL display panel including a third step of forming a light emitting portion, wherein the organic EL light emitting portion includes a plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer and a row direction. A plurality of partition walls arranged between the pixel electrodes adjacent to the above and extending in the row direction, an organic layer including a light emitting layer formed in a region partitioned by the partition walls, and an organic layer formed above the organic layer. The first light emitting unit includes a first light emitting unit including a counter electrode and having a light emitting layer that emits a first color, and a second light emitting unit that has a light emitting layer that emits a second color different from the first color. The layer thickness of the organic layer is different between the portion and the second light emitting portion, and in the second step, the interlayer insulating layer in the region partitioned by the partition wall of the first light emitting portion and the second light emitting portion has a different depth. An electrode digging is formed.

According to this aspect, it is possible to manufacture an organic EL display panel capable of displaying a high-quality image having excellent luminous efficiency as described above.
Further, in the method for manufacturing an organic EL display panel according to another aspect of the present disclosure, in the above aspect, the interlayer insulating layer is made of a photosensitive resin material, and in the second step, the interlayer is used by using a halftone mask. Digging of different depths in the insulating layer is formed in a single photolithography process.

As a result, it is possible to easily form diggings having different depths in the interlayer insulating layer without increasing the man-hours so much.
In each of the above-described embodiments, "upper" does not mean an upward direction (vertically upward) in absolute spatial recognition, but a relative position based on the stacking order in the laminated structure of the organic EL display panel. It is defined by the relationship. Specifically, in the organic EL display panel, the direction perpendicular to the main surface of the substrate and the direction from the substrate toward the laminate side is the upward direction. Further, for example, the expression "on the substrate" does not mean only the region directly in contact with the substrate, but also includes the region above the substrate via the laminate. Further, for example, when the expression "above the substrate" is used, it does not mean only the upper region separated from the substrate, but also includes the region on the substrate.

<< Embodiment >>
Hereinafter, the organic EL 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 signboard, a large screen for commercial facilities), and the like.

The organic EL display device 1 includes an organic EL display panel 10 and a drive control unit 200 electrically connected to the organic EL display panel 10.
In the present embodiment, the organic EL display panel 10 is a top emission type display panel whose upper surface is a rectangular image display surface. In the organic EL 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 organic EL display panel 10 adopts an active matrix method as an example.

The drive control unit 200 includes a drive circuit 210 connected to the organic EL 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 organic EL display panel 10 as an example, but the configuration of the drive control unit 200 is not limited to this, and the number of drive circuits 210 is not limited to this. And the position 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 organic EL display panel 10 is defined as the X direction, and the direction along the short side of the upper surface of the organic EL display panel 10 is defined as the Y direction. ..

2. 2. Configuration of Organic EL Display Panel 10 (A) Planar Configuration FIG. 2 is a schematic plan view in which a part of the image display surface of the organic EL display panel 10 is enlarged. In the organic EL 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. They are arranged in a shape. The sub-pixels 100R, 100G, 100B are arranged alternately in the X direction (row direction), and a set of sub-pixels 100R, 100G, 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 (column direction), the sub pixel row CR, the sub pixel row CG, and the sub pixel row CB are configured by arranging only one of the sub pixel 100R, the sub pixel 100G, and the sub pixel 100B, respectively. .. As a result, the pixels P of the organic EL display panel 10 as a whole are arranged in a matrix along the X and Y directions, 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 (see FIG. 3) that emit light in the colors R, G, and B are arranged in the sub-pixels 100R, 100G, and 100B, respectively.
Further, the organic EL display panel 10 according to the present embodiment employs a so-called line bank method. That is, a plurality of partition walls (banks) 14 for partitioning the sub-pixel rows CR, CG, and CB for each row are arranged at intervals in the X direction, and in each sub-pixel row CR, CG, and CB, the sub-pixels 100R, 100G, 100B 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 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 surface of the light emitting layer. In FIG. 2, the partition wall 14 and the pixel regulation layer 141 are represented by dotted lines, which is because the pixel regulation layer 141 and the partition wall 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 of the organic EL element FIG. 3 is a schematic cross-sectional view taken along the line AA of FIG.
In the organic EL display panel 10, one pixel is composed of three sub-pixels that emit light of R, G, and B, respectively. Each sub-pixel is composed of an organic EL element that emits a corresponding color.
Since the organic EL elements of each color basically have almost 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 13, a partition wall 14, a hole injection layer 15, a hole transport layer 16, a light emitting layer 17, an electron transport layer 18, and electrons. It is composed of an injection layer 19, a counter electrode 20, and a sealing layer 21.
The substrate 11, the interlayer insulating layer 12, the electron transport layer 18, the electron injection layer 19, the counter electrode 20, and the sealing layer 21 are not formed for each pixel, but a plurality of organic EL display panels 10 include. It is commonly formed in the organic EL element 2.

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

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

Further, on the upper surface of the interlayer insulating layer 12, digging portions 125R and 125G are formed at locations corresponding to the light emitting regions of R and G. The digging amount (depth) of the digging portion 125R is larger than that of the digging 125G, and the bottoms of both are flat portions parallel to the main surface of the substrate 11.
It is desirable in terms of optical design to form the above-mentioned optical resonance structure in the layer thicknesses of the light emitting layers 17 (R), 17 (G), and 17 (B) in the sub-pixels of each light emitting color by the dug portions 125R and 125G. The film shape can be made uniform while making a difference. Since the optical resonance structure itself has a well-known structure, it will not be described in detail.

In the present embodiment, a negative type photosensitive resin is used as the interlayer insulating layer 12, and the dug portions 125R and 125G are formed by a photolithography method using a halftone mask. Details will be described later.
(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 the present 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 zinc oxide) is laminated on the metal layer. May be good.
(4) Partition / Pixel Restriction Layer The partition 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 line.

An electrically insulating material is used for the partition wall 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 partition wall 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 partition wall 14 preferably has resistance to an organic solvent and heat. Further, in order to suppress the outflow of ink, it is preferable that the surface of the partition wall 14 has a predetermined liquid repellency.
In the portion where the pixel electrode 13 is not formed, the bottom surface of the partition wall 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 15 improves the electrical insulation of the pixel electrodes 13 adjacent to each other in the Y direction, suppresses the step breakage of the organic light emitting layer 16 in each of the sub-pixel rows CR, CG, and CB, and forms the pixel electrodes 13. It has a role of improving the electrical insulation between the counter electrode 17 and the like.
Specific examples of the electrically insulating material used for the pixel regulation layer 15 include a resin material and an inorganic material exemplified as the material of the partition wall 14. Further, when the organic light emitting layer 16 to be the upper layer is formed, it is preferable that the surface of the pixel regulation layer 15 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 on the pixel electrode 13 for the purpose of promoting the injection of holes from the pixel electrode 13 into the light emitting layer 17. The hole injection layer 15 is, for example, an oxide such as Ag (silver), Mo (molybdenum), Cr (chromium), V (vanadium), W (tungsten), Ni (nickel), Ir (iridium), or A layer made of a conductive polymeric material such as PEDOT (a mixture of polythiophene and polystyrene sulfonic acid).

Of the above, the hole injection layer 15 made of a metal oxide has a function of injecting holes into the light emitting layer 17 in a stable manner or assisting the generation of holes, which is a major task. Has a function.
In this embodiment, the hole injection layer 15 is made of tungsten oxide. When the hole injection layer 15 is formed of a transition metal oxide, it takes a plurality of oxidation numbers, so that a plurality of levels can be taken. As a result, hole injection becomes easy and contributes to a reduction in driving voltage. To do.

(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 is formed by a wet process using, for example, polyfluorene or a derivative thereof, or a polymer compound such as polyarylamine or a derivative thereof, which does not have a hydrophilic group.

(7) 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.
As the material of the light emitting layer 17, a known material can be used. Specifically, for example, an oxinoid compound, a perylene compound, a coumarin compound, an azacmarin compound, an oxazole compound, an oxaziazole compound, a perinone compound, a pyrolopyrrole compound, a naphthalene compound, an anthracene compound, a fluorene compound, a fluorantene compound, a tetracene compound, and pyrene. Compounds, coronen compounds, quinolone compounds and azaquinolone compounds, pyrazoline derivatives and pyrazolone derivatives, rhodamine compounds, chrysene compounds, phenanthrene compounds, cyclopentadiene compounds, stylben compounds, diphenylquinone compounds, styryl compounds, butadiene compounds, dicyanomethylenepyran compounds, dicyanomethylene Thiopyran compound, fluorescein compound, pyririum compound, thiapyrrium compound, selenapyrylium compound, tellropyrylium compound, aromatic aldaziene compound, oligophenylene compound, thioxanthene compound, cyanine compound, aclysine compound, metal complex of 8-hydroxyquinoline compound, 2 -It is preferably formed of a fluorescent substance such as a metal complex of a bipyridine compound, a complex of a shift salt and a group III metal, an oxine metal complex, or a rare earth complex.

(8) Electron transport layer The electron transport layer 18 has a function of transporting electrons from the counter electrode 20 to the light emitting layer 17. The electron transport layer 18 is made of an organic material having high electron transport properties, and does not contain alkali metals and alkaline earth metals.
Examples of the organic material used for the electron transport layer 18 include π-electron low molecular weight organic materials such as an oxadiazole derivative (OXD), a triazole derivative (TAZ), and a phenanthroline derivative (BCP, Bphen).

(9) Electron injection layer The electron injection layer 19 has a function of injecting electrons supplied from the counter electrode 20 toward the light emitting layer 17. The electron injection layer 19 is formed by, for example, doping an organic material having high electron transport property with a doping metal selected from an alkali metal or an alkaline earth metal.
The metals corresponding to alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), and the metals corresponding to alkaline earth metals are Calcium (Ca), Strontium (Sr), Barium (Ba), Rubidium (Ra).

In this embodiment, barium (Ba) is doped.
Examples of the organic material used for the electron injection layer 19 include π-electron low-molecular-weight organic materials such as an oxadiazole derivative (OXD), a triazole derivative (TAZ), and a phenanthroline derivative (BCP, Bphen). Be done.
(10) Counter electrode The counter electrode 20 is made of a translucent conductive material and is formed on the electron injection layer 19. The counter electrode 20 functions as a cathode.

As the material of the counter electrode 20, for example, ITO or IZO can be used, but in order to obtain the optical resonance structure more effectively, the material of the counter electrode 20 is silver, a silver alloy, aluminum, or an aluminum alloy. It is desirable to use a metal such as. In this case, since the counter electrode 20 needs to have translucency, the film thickness is formed as a thin film of about 20 nm or less.
(11) Encapsulation layer The encapsulation layer 21 deteriorates when organic layers such as the hole transport layer 16, the light emitting layer 17, the electron transport layer 18, and the electron injection layer 19 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 an adhesive. By laminating these, the hole transport layer 16, the light emitting layer 17, the electron transport layer 18, and the electron injection layer 19 can be further protected from moisture, air, and the like.

3. 3. Manufacturing Method of Organic EL Display Panel 10 Hereinafter, a manufacturing method of the organic EL display panel 10 will be described with reference to the drawings.
4 (a) to (f), FIGS. 5 (a) to 5 (d), and FIGS. 6 (a) to 6 (d) are schematic cross-sectional views showing states in each step in the manufacture of the organic EL display panel 10. is there. Further, FIG. 7 is a flowchart showing a manufacturing process of the organic EL display panel 10.

(1) Substrate Preparation Step First, as shown in FIG. 4A, a TFT layer 112 is formed on the substrate 111 to prepare the substrate 11 (step S1 in FIG. 7). The TFT layer 112 can be formed by a known method for manufacturing a TFT.
(2) Interlayer Insulation Layer Forming Step Next, as shown in FIG. 4B, an interlayer insulation layer 12 having the dug portions 125R and 125G is formed on the substrate 11 (step S2 in FIG. 7).

Specifically, a negative-type photosensitive resin material having a constant fluidity is applied, for example, by a die coating method along the upper surface of the substrate 11 so as to fill the unevenness on the substrate 11 by the TFT layer 112. 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.
Next, a digging portion is formed in a region where the light emitting layer 17 is planned to be formed in the sub-pixels of each light emitting color of the interlayer insulating layer 12.

Since the film thickness of the blue (B) light emitting layer having the shortest wavelength is the thinnest, it is not necessary to form a digging portion (in the present specification, the digging amount is defined as "0". .).
Therefore, a photomask 120 is arranged on the upper surface of the interlayer insulating layer 12 for exposure. The photomask 120 has a first halftone section 1201, a second halftone section 1202, and a full exposure section 1203, and is formed so that the light transmittance increases in this order.

The positions of the first halftone unit 1201 and the second halftone unit 1202 correspond to the planned formation positions of the light emitting layer 17 (R) and the light emitting layer 17 (G) in the sub-pixels 100R and 100G, respectively. The transmittance of the first halftone section 1201 and the second halftone section 1202 exposes the planned formation positions of the dug portions 125R and 125G of the interlayer insulating layer 12 to the required depths at a predetermined exposure time. It is set so that it can be done.

By developing and cleaning after the exposure, the dug portions 125R and 125G are formed on the upper surface of the interlayer insulating layer 12 as shown in FIG. 4D.
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) Step of Forming Pixel Electrode / Hole Injection Layer Next, as shown in FIG. 4E, 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.

Further, the hole injection material layer 150 is formed on the pixel electrode material layer 130. The hole injection material layer 150 can be formed by, for example, a reactive sputtering method or the like.
Then, as shown in FIG. 4 (f), the pixel electrode material layer 130 and the hole injection material layer 150 are patterned by etching, and a plurality of pixel electrodes 13 and hole injection layers 15 partitioned for each sub-pixel are formed. And are formed (step S3 in FIG. 7).

The method of forming the pixel electrode 13 and the hole injection layer 15 is not limited to the above method. For example, the pixel electrode material layer 130 is patterned to form the pixel electrode 13, and then the hole injection layer 15 is formed. You may.
Further, the hole injection layer 15 may be formed by a wet method after the partition wall 14 is formed.

(4) Partition / Pixel Restriction Layer Forming Step Next, the partition 14 and the pixel regulation layer 141 are formed (step S4 in FIG. 7). In the present embodiment, the partition wall 14 and the pixel regulation layer 141 are formed at the same time by using the halftone mask as follows.
First, as shown in FIG. 5A, a resin material is applied to the interlayer insulating layer 12 on which the pixel electrode 13 and the hole injection layer 15 are formed by the film thickness of the partition wall 14 to form the partition wall material layer 140. To do. As a specific coating method, for example, a wet method such as a die coating method, a slit coating method, or a spin coating method can be used.

After coating, for example, it is preferable to perform vacuum drying and low temperature heat drying (prebaking) at about 60 ° C. to 120 ° C. to remove unnecessary solvents and fix the partition wall material layer 140 to the interlayer insulating layer 12.
Next, the partition material layer 140 is exposed via a photomask (not shown).
For example, when the partition wall material layer 140 has positive photosensitivity, the portion where the partition wall material layer 140 is left is shielded from light, and the portion to be removed is exposed.

In the case of this example, since the pixel regulation layer 141 has a smaller film thickness than the partition wall 14, it is necessary to semi-expose the partition wall material layer 140 on the portion of the pixel regulation layer 141.
Therefore, the photomask used in this exposure step includes a light-shielding portion arranged at a position corresponding to the partition wall 14 to completely block light, a translucent portion arranged at a position corresponding to the pixel regulation layer 141, and the like. Those having a translucent portion arranged at a position corresponding to the exposed portion of the pixel electrode 13 other than the above are used.

The translucency of the translucent portion is determined so that when exposed for a predetermined time, the partition wall material layer 140 on the pixel electrode 13 is fully exposed, and the pixel restricting layer 141 remains unexposed by the height thereof. ..
Next, by developing and removing the exposed region of the partition wall material layer 140, the partition wall 14 and the pixel regulation layer 141 having a smaller film thickness can be formed. 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 the exposed portion of the partition wall material layer 140, and then the substrate is rinsed with a rinsing solution such as pure water. 11 may be washed.

As a result, a partition wall 14 having a shape extending in the Y direction and a pixel regulating layer 141 extending in the X direction can be formed on the interlayer insulating layer 12.
(5) Hole Transport Layer Forming Step Next, as shown in FIG. 5 (c), an ink containing the constituent material of the hole transport layer 16 is applied to the opening 14a defined by the partition wall 14 in a printing apparatus. It is discharged from the nozzle 3011 of the head 301 and applied onto the hole injection layer 15 in the opening 14a. At this time, the hole injection layer 15 is applied so as to extend along the Y direction (FIG. 2) above the pixel electrode row. Then, it is dried to form the hole transport layer 16 (step S5 in FIG. 7).

(6) Light-emitting layer forming step Next, the light-emitting layer 17 is formed above the hole transport layer 16 (step S6 in FIG. 7).
Specifically, as shown in FIG. 7D, ink containing a luminescent material having a luminescent color corresponding to each opening 14a is sequentially ejected from the nozzle 3011 of the coating head 301 of the printing apparatus into the opening 14a. Is applied on the hole transport layer 16. At this time, the ink is applied so as to be continuous even above the pixel regulation layer 141. As a result, the ink can flow along the Y direction, the uneven coating of the ink can be reduced, and the film thickness of the light emitting layer 17 in the same sub-pixel row can be made uniform. The amount of ink dropped in each emission color is controlled so that the film thickness becomes thinner in the order of the light emitting layers 17 (R), 17 (G), and 17 (B).

Then, the substrate 11 after the ink is applied is carried into the vacuum drying chamber and heated in a vacuum environment to evaporate the organic solvent in the ink. As a result, the light emitting layer 17 can be formed.
(7) Electron Transport Layer Forming Step Next, as shown in FIG. 6A, the electron transport layer 18 is formed on the light emitting layer 17 and the partition wall 14 (step S7 in FIG. 7). The electron transport layer 18 is formed, for example, by forming an electron transportable organic material in common with each sub-pixel by a vapor deposition method.

(8) Electron Injection Layer Forming Step Next, as shown in FIG. 6B, an electron injection layer 19 is formed on the electron transport layer 18 (step S8 in FIG. 7). The electron injection layer 19 is formed, for example, by forming an electron-transporting organic material and a doped metal in common on each sub-pixel by a co-evaporation method.
(9) Counter electrode forming step Next, as shown in FIG. 6 (c), the counter electrode 20 is formed on the electron injection layer 19 (step S9 in FIG. 7). In the present embodiment, the counter electrode 20 is formed by forming a film of silver, aluminum, or the like by a sputtering method or a vacuum vapor deposition method.

(10) Sealing layer forming step Next, as shown in FIG. 6D, the sealing layer 21 is formed on the counter electrode 20 (step S10 in FIG. 7). The sealing layer 21 can be formed by forming a film of SiON, SiN, etc. by a sputtering method, a CVD method, or the like.
As a result, the organic EL display panel 10 is completed.

The above manufacturing method is merely an example and can be changed as appropriate.
4. The film shape of each light emitting layer FIG. 8 shows the hole injection layer 15 and the hole transport layer of each RGB organic EL element when the partition wall 14 is formed at a height of 0.8 μm in the method for manufacturing the organic EL display panel. 16. It is a graph which shows the result of having measured the height from the pixel electrode 13 of the surface of the light emitting layer 17. The digging portions 125R and G are provided in the organic EL elements of R and G.

In FIG. 8, the broken line is the height of the surface of the hole injection layer 15, the solid line (thin line) is the height of the surface of the hole transport layer 16, and the solid line (thick line) at the top is the surface of the light emitting layer 17. The measured value of the height of is shown. Each measurement was performed using an atomic force microscope (AFM).
As shown in the figure, although the film thickness of each of the RGB light emitting layers 17 is different, it can be seen that in the film shape of the upper surface thereof, the flat portion occupies most of the opening width and is uniform in each color. ..

9 and 10 are graphs showing the detection results of the film shape when the heights of the partition walls 14 are 1.2 μm and 0.5 μm, respectively. Even when the height of the partition wall 14 is changed in this way, the digging structure of the interlayer insulating layer 12 is adopted as in the present embodiment, and the digging amount is set to a depth corresponding to the difference in each film thickness. As a result, the film shapes of the light emitting layers 17 of the RGB light emitting colors can be substantially made uniform.

However, when the height of the partition wall 14 is 1.2 μm (FIG. 9), the curvature of the portion close to the partition wall 14 becomes larger than that in the case of FIG. 8 (height of the partition wall 14 is 0.8 μm). The area of the flat part in the center of the opening is slightly smaller.
Further, when the height of the partition wall 14 in FIG. 10 is 0.5 μm, it can be seen that the central portion of the opening is slightly raised above the portions at both ends thereof.

11 (a), (b), and (c) are schematic views showing slightly exaggerated differences in film shape when the same amount of ink is dropped on openings having different heights of the partition walls 14. is there.
In the actual production line, after applying the ink of the light emitting layer, it is carried into the vacuum drying device and dried, but until it is carried into the vacuum device and the atmosphere inside the device is lowered to the target atmospheric pressure. It takes some waiting time. Generally, since the organic solvent of ink is highly volatile, the organic solvent evaporates even during the above waiting time.

The upper part of each of FIGS. 11A, 11B, and 11C schematically shows the change in film shape during the waiting time before vacuum drying. The broken line 1701 shows the surface shape of the ink pool immediately after the ink is dropped, and the solid line 1702 shows the surface shape of the ink pool after the lapse of the waiting time.
As described above, the pinning position from the top of the partition wall 14 hardly changes. Further, at this stage, the drying speed is not so high, and the speed at which the solute (organic material) moves in the ink is sufficiently faster than the drying speed. Therefore, when the partition wall 14 is high as shown in the upper part of FIG. 11A. The central part is greatly depressed. After that, when vacuum dried (lower part of FIG. 11A), the drying progresses rapidly, the viscosity of the ink increases, and the moving speed of the solute slows down. Therefore, the solid line 1703 keeps the shape of the liquid surface in the upper part. The indicated film shape will be formed.

Further, when the height of the partition wall 14 is lower than that in the case of FIG. 11A as shown in FIG. 11B and is balanced with the amount of ink dropped, as shown in the upper part thereof. In addition, in the natural drying before vacuum drying, the surface of the ink pool is almost flat as shown by the solid line 1702, and during vacuum drying, the ink pool is rapidly dried while the film shape is almost maintained (the figure (Fig. b) See solid line 1703 at the bottom).

Further, when the height of the partition wall 14 is lower than that in the case of FIG. 11 (b) as shown in FIG. 11 (c), the natural state before vacuum drying is shown as shown in the upper figure thereof. In drying, the film shape bulges slightly upward (broken line 1701), and during vacuum drying, the film shape is rapidly maintained while being almost maintained (see the lower part of Fig. (C), solid line 1703). ).
As described above, the height of the partition wall 14, more specifically, the volume of the opening below the pinning position determined by the height of the partition wall 14, its liquid repellency, and the surface tension of the ink, and the amount of ink dropped and the solvent. By appropriately adjusting the type and the like, it is possible to obtain a more desirable shape in which the proportion of the flat portion in the film shape of the light emitting layer is a predetermined value or more.

FIG. 12 is a diagram schematically showing an enlarged film shape of the blue light emitting layer 17 formed in the case of FIG. 11B.
As shown in the figure, the light emitting layer 17 has a central flat portion 172 and a portion (riding portion) 173 that rides up to the pinning position P4 along the side surface of the partition wall 14.
Although the term "flat portion" is microscopically affected by the surface shape of the base, it is conceivable that the surface of the flat portion 172 may have minute irregularities. When a continuous region in which the difference from the surface height of the thinnest portion of the central portion of the film shape of the layer 17 is within 400 nm is defined as a “flat portion”, the direction in which the partition wall 14 extends (row) of the flat portion. The ratio of the width W1 in the direction orthogonal to the direction (FIG. 2: X direction) to the narrowest width W2 in the X direction of the opening 14a of the adjacent partition wall 14 (hereinafter referred to as “flatness”) is 90%. The above is desirable. This is because the desired aperture ratio and luminous efficiency can be obtained for each sub-pixel.

Then, in order to satisfy the condition of the flatness of the film shape as described above, the same experiment as in FIGS. 8 to 10 was carried out under the formation conditions (height of partition wall, material of partition wall, material of solvent of ink, dropping of ink). When the amount) was changed, the difference h (see FIG. 12) between the height of the pinning position P4 and the height of the lowest position at the center of the film shape of the light emitting layer was 700 nm or less. It turned out that it was desirable to determine the conditions.

In order to obtain even better luminous efficiency, the flatness of the flat portion where the difference from the surface height of the thinnest portion of the central portion of the film shape of the light emitting layer 17 is 100 nm or less is 90% or more. Is more desirable.
Then, in the opening where the red and green light emitting layers having a larger film thickness than the blue light emitting layer are formed, the interlayer insulating layer 12 is provided with a digging portion having a depth corresponding to the difference, so that each light emitting color can be obtained. The film shape of the light emitting layer in charge can be adjusted to the optimum state.

5. Relationship between the required amount of ink and the amount of digging In FIG. 13, the target film thicknesses of the light emitting layers 17 (R), 17 (G), and 17 (B) are set to 0.12 μm, 0.08 μm, and 0.04 μm, respectively. It is a table when the required liquid amount of ink in the case of this is calculated.
In the same table, the amount of each ink is positive on the base (in the embodiment) of the ink top surface (liquid level) on the assumption that the cross-sectional area of the ink pool on the surface orthogonal to the normal of the substrate is constant. Although the hole transport layer 16 is provided, here, for convenience of explanation, the surface of the interlayer insulating layer 12 having no dug portion will be described as a base.) The height from the liquid surface to the liquid surface (liquid height) is set to μm. It is written as a unit.

In addition, the required height of the partition wall is based on the assumption that the material of the partition wall is not liquid-repellent, and even if 3 μm of ink is applied to the height of the partition wall, the ink pool can be maintained (does not overflow) due to its surface tension. Therefore, the height from the base is used. Each ink density is shown as a volume percentage.
In the table of FIG. 13, for example, when the ink density is 0.5%, in order to obtain the film thicknesses of the light emitting layers of R, G, and B of 0.12 μm, 0.08 μm, and 0.04 μm, respectively, the ink is used. The amount is the liquid height, and 24 μm, 16 μm, and 8 μm are required.

Since the film thickness of the light emitting layer of B is the smallest, it is not necessary to provide a digging portion in the interlayer insulating layer in this portion, and the liquid height of the blue ink is a standard for determining the required partition height. When the ink can be piled up to 3 μm on the partition wall as described above, the required partition wall height is 5 μm, which is obtained by subtracting the above 3 μm from the liquid height of the blue ink of 8 μm.
The value 16.0 μm, which is obtained by subtracting the minimum value of the liquid height (8 μm of B) from the maximum value of the liquid height of the ink (24 μm of R), is the amount of digging of the interlayer insulating layer in the organic EL element of R Δ (Δ = MAX). -MIN). Further, the amount of digging of the interlayer insulating layer in the green (G) organic EL element using the ink having the same concentration is 16 μm-8 μm = 8 μm.

Similarly, for other ink densities, the partition height and the amount of digging are required.
When the ink density is 1.6% or more, the liquid height indicating the amount of blue ink is less than 3 μm of the ink filling height, so that the height of the partition wall is calculated to be 0 μm. It should be okay, but in reality, it is desirable that there is at least 0.1 μm as a partition for filling ink.

When the ink density is the same for RGB as described above, the required partition height is in the range of 0.1 μm to 5.0 μm when the ink density is in the range of 0.5% to 10%. The amount of digging in the organic EL element of R is in the range of 0.8 μm to 16 μm.
However, since the above is just an example of a trial calculation in a model case, an appropriate correction coefficient is obtained by an experiment or the like and applied to an actual design.

Next, a case where the density of the ink in each emission color is changed without forming a dug portion in the interlayer insulating layer 12 will be examined.
According to the table of FIG. 13, for example, when the height of the partition wall is 2.0 μm, the ink for forming the light emitting layer for blue light emission has an ink density of 0.8% and a liquid height of 5 μm. is required. If you want to make the liquid height of the ink amount the same 5 μm with the ink for green light emission, you need to make the ink density 1.6%, and further, the liquid height of the ink amount is the same with the ink for red light emission. If you want to make it 5 μm, you need to increase the ink density to 2.4%.

However, the ink density (viscosity) is an important factor for smooth ejection from the nozzle of the printing apparatus and precise positioning, and it is considered that there is a certain limit to the range in which the ink density can be taken. In particular, in the above example, the ink density for red light emission is three times as high as the ink density for blue light emission, and the viscosities are significantly different. Therefore, the pinning position may become unstable between the light emitting layers of each light emitting color, or the degree of wetting and spreading of the ink to the opening may differ, and the film shape may become uneven.

Further, if the ink density is high, it may cause troubles such as nozzle clogging of the printing apparatus. Furthermore, it takes time to manage the ink density, and there is a strong demand for design changes and for reducing manufacturing costs by using the same printing device and the same ink for models with different specifications as much as possible.
Considering the above points, it is desirable to adjust the film thickness by adjusting the amount of ink dropped, which is easy to control, without changing the existing ink density as much as possible. At that time, the organic EL element of each emission color as described above. By adjusting the amount of digging of the interlayer insulating layer in the above and aligning the film shapes, it is possible to obtain a high-quality organic EL display panel having a good emission light rate and a small variation in aperture ratio for each emission color. is there.

6. Effect (summary)
(1) According to the organic EL display panel 10 according to the above embodiment, when the layer thickness of the light emitting layer of each light emitting color is different, the amount of digging of the interlayer insulating layer is adjusted according to the required layer thickness. As a result, the film shape of the light emitting layer of each light emitting color can be made uniform. Further, by setting the height of the partition wall to a predetermined value, the flatness of the light emitting layer after drying can be improved, and the luminous efficiency can be improved.

Here, the specific amount of digging in the organic EL element of each emission color can be obtained by the following method.
(A) The thickness of the flat portion of the light emitting layer in each light emitting color is obtained by an optical design for constructing an optical resonance structure.
(B) The amount of ink to be dropped at each light emitting layer formation position is determined from the determined layer thickness of the light emitting layer of each color, the ink density to be used, and the shape (capacity) of the opening on which the light emitting layer should be formed. ..

(C) Based on the surface shape of the ink sump in a specific emission color (blue in the above), the surface shape of the ink sump of other emission colors is the same (that is, above the pinning position of the ink sump). (Hereinafter, so that the amount of ink swelling is the same) and the amount of digging in the organic EL element of another emission color are determined.
Further, the height of the partition wall is determined so that the amount of ink swelling in the above (c) is within an appropriate range (see FIG. 11 (b)) and the flatness of the light emitting layer after drying is 90% or more. To. Specifically, the difference between the height of the center position and the height of the pinning position of the light emitting layer after drying may be set to be 700 nm or less.

This makes it possible to provide an organic EL display panel capable of displaying a high-quality image with excellent luminous efficiency while efficiently forming an organic light emitting layer by a wet process.
(2) Further, in the interlayer insulating layer forming step, the interlayer insulating layer is formed of a photosensitive resin material and exposed and developed using halftone masks having different light transmittances to obtain different depths at once. Since it is possible to form a digging part of the material, the effect obtained is large even though the man-hours do not increase so much.

≪Modification example≫
As described above, an embodiment of an organic EL display panel and a method for manufacturing an organic EL display panel has been described as one aspect of the present invention, but the present invention has nothing to do with the above description except for its essential characteristic components. It is not limited. Hereinafter, a modified example which is another embodiment of the present invention will be described.

(1) Modification Example of Interlayer Insulation Layer Forming Step In the above embodiment, a halftone mask is used to form digging portions having different depths in the interlayer insulation layer 12 in one photolithography step. It is not limited to this.
(1-1) When Multilayer Exposure is Performed FIGS. 14 (a) to 14 (d) are schematic views showing a first modification example for forming a dug portion in the interlayer insulating layer 12.

In this modification, it is assumed that the interlayer insulating layer 12 is made of a positive organic resin material.
First, the surface of the interlayer insulating layer 12 is exposed through a mask 121 that fully exposes only the corresponding portion of the dug portion 125R (FIG. 14A), which is developed and then washed to remove unnecessary portions. By leaving, the first digging is performed in the portion to be formed of the digging portion 125R, and the digging portion 125R'is formed (FIG. 14 (b)).

Next, the interlayer insulating layer 12 is exposed using the mask 122 in order to fully expose the portions corresponding to the dug portion 125R and the dug portion 125G (FIG. 14 (c)). Then, after developing this, it is washed and unnecessary portions are washed away to form the dug portions 125R and 125G (FIG. 14 (d)).
The exposure amounts for the first and second times are determined so that the depths of the dug portions 125R and 125G are the target values.

In the embodiment, since the transmittance in the halftone portion of the photomask is specified, there is an advantage that the number of man-hours can be reduced, but the mask is not versatile. However, according to this modification. Since various digging amounts can be set simply by controlling the exposure amount of the first and second times, the depth of the digging part can be adjusted flexibly in response to model changes and ink type changes. ..

(1-2) When Etching is Performed FIGS. 15 (a) to 15 (d) and FIGS. 16 (a) to 16 (d) are schematic views showing deformation examples when the dug portions 125R and 125G are formed by etching. Is.
First, the resist 123 is applied to the surface of the interlayer insulating layer 12 (FIG. 15A). Then, using a mask (not shown), the position of the resist 123 corresponding to the dug portion 125R is exposed, developed, and washed to form an opening 123R in the resist 123, and a dry etching process is performed using the resist 123 as a mask. This is done to form a dug portion 125R'in the interlayer insulating layer 12 (FIG. 15 (c)). Then, the resist 123 is removed with an organic solvent such as acetone (FIG. 15 (d)).

Next, as shown in FIG. 16A, the resist 124 is applied onto the interlayer insulating layer 12, and the positions of the resist 123 corresponding to the dug portions 125R and 125G are exposed using a mask (not shown). , Developed and washed to form openings 124R and 124G in the resist 124, and dry etching using the resist 124 as a mask to form dug portions 125R and 125G in the interlayer insulating layer 12 (FIG. 16C). ). Then, the resist 124 is removed with an organic solvent such as acetone (FIG. 16 (d)).

In addition, in order to form the dug portions 125R and 125G, wet etching may be performed instead of dry etching.
Further, a pretreatment step may be provided in which the interlayer insulating layer 12 is fully exposed before FIGS. 14 (a) and 15 (a) to prepare the surface of the interlayer insulating layer 12.
(2) In the above embodiment, the partition wall 14 and the pixel regulation layer 141 having different heights are simultaneously formed in one step by using a halftone mask, but the partition wall 14 and the pixel regulation layer 141 are formed in another step. It doesn't matter.

For example, first, a pixel regulation layer 141 for partitioning a pixel electrode row in the Y direction is formed.
As a specific method for forming the pixel regulation layer 141, for example, a resin material is applied to the upper surface of the substrate 11 on which the pixel electrode 13 is formed by a die coating method or the like. Then, the pixel regulation layer 141 can be formed by patterning the resin material so as to form the pixel regulation layer 141 between the pixel electrodes 13 adjacent to each other in the Y direction using a photolithography method and then firing the resin material. ..

Next, the partition wall resin, which is the material of the partition wall 14, is uniformly applied by, for example, a die coating method to form a partition wall material layer, patterned on the partition wall material layer by a photolithography method, and then fired. The partition wall 14 is formed.
(3) Deformation Example of Laminated Structure of Organic EL Element In the above embodiment, the laminated structure of the organic EL element includes an electron transport layer 18, an electron injection layer 19, a hole injection layer 15, and a hole transport layer 16. However, it is not limited to this. For example, it may be an organic EL element having no electron transport layer 18 or an organic EL element having no hole transport layer 16. Further, for example, a single hole injection transport layer may be provided instead of the hole injection layer 15 and the hole transport layer 16. Further, for example, an intermediate layer made of an alkali metal may be provided between the light emitting layer 17 and the electron transport layer 18.

However, a minimum configuration (a basic configuration in which an organic light emitting layer is interposed between a pixel electrode and a counter electrode) is required to exert a function as an organic EL element.
(4) In the organic EL 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 organic EL display panel 10, and the stretching direction of the partition wall 14 is the organic EL. Although it was in the Y direction of the minor axis of the display panel 10, the stretching directions of the pixel regulation layer 141 and the partition wall 14 may be opposite. Further, the stretching direction of the pixel insulating layer and the partition wall may be a direction irrelevant to the shape of the organic EL display panel 10.

Further, in the organic EL 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 organic EL 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, even a so-called pixel bank type organic EL display panel in which each sub-pixel is surrounded on all four sides by a partition wall is used. I do not care.

(5) In the organic EL 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, in addition to R, G, and B, four colors of yellow (Y) may be used. 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.

When there are three or more types of emission colors in this way, and the sub-pixels that emit two different types of emission colors are the first light emitting unit and the second light emitting unit, the dug portion in the interlayer insulating layer 12 By making the depth of the light emitting layer different depending on the film thickness of the light emitting layer of those light emitting colors, a film shape more uniform than the conventional one can be obtained.
(6) In the above embodiment, since the layer thickness of the blue organic EL element having the shortest emission color is the smallest, the interlayer insulating layer is not provided with a digging portion. May also provide a digging in this part. By that amount, the amount of digging of the interlayer insulating layer in the sub-pixels of other red and green emission colors becomes deeper.

(7) In the above embodiment, the digging portion (digging portion 125R) of the organic EL element having a large layer thickness of the light emitting layer is the digging portion (digging portion) of the organic EL element having a smaller layer thickness. Although it was formed so as to be deeper than 125G), the magnitude relation of the layer thickness of the light emitting layer and the magnitude relation of the digging amount do not always match.
It is assumed that the ink density can be changed for each emission color within the range permitted by the specifications of the printing apparatus to be used. For example, in the table of FIG. 13, considering the case where the ink density for R is 1.6% and the ink density for G is 1.0%, the required amount of ink for R is 7.5 μm at the liquid height. However, the liquid height of the required ink amount for G is 8.0 μm, and the ink required amount is reversed between R and G, and the digging amount of the digging portion 125G is the digging of the digging portion 125R. This is because there may be a case where the amount is larger than the amount of ink.

(8) In the above embodiment, the film thickness of the light emitting layer is adjusted so that the optical path difference satisfies a predetermined condition in order to obtain the optical resonance effect by making the pixel electrode 13 light reflective. In addition to or instead of the light emitting layer, the film thickness of the hole injection layer and / or the hole transport layer under the light emitting layer may be changed to obtain the optical resonance effect. In short, the film thickness of the entire organic layer including the light emitting layer may be adjusted.

This is because even when the hole injection layer and the hole transport layer are formed by a wet process to have different layer thicknesses, the same problem as when the light emitting layer is formed occurs, and it is necessary to provide a digging portion.
(9) It is desirable that the shape of the bottom surface of the dug portion is as flat as possible. This is because if the bottom surface is curved, the shape affects the surface shape of each layer laminated above, and it becomes difficult to flatten the film shape of the light emitting layer.

However, since the main purpose of the "flatness" required for the digging portion is to make the film shapes of the light emitting layers of each color uniform, the interlayer insulating layer 12 in the blue organic EL element having no digging portion is provided. It suffices as long as it is as flat as the surface.
Further, in the example shown in FIG. 3, since the digging amount of the digging portions 125R and 125G is not so deep, the side shape of the digging portion does not matter so much, but digging as shown in FIG. 19B. When the portion is deep and the light emitting layer or another organic layer comes into contact with the inner surface of the dug portion, the inner surface of the dug portion is the dug portion as shown in FIG. 19 (b). It is desirable that the shape is formed so as to be continuously connected to the inner surface of the digging portion, and the angle between the inner surface of the digging portion and the inner surface of the digging portion is as small as possible.

If a step is formed at the connecting portion between the inner surface of the digging portion and the inner surface of the digging portion, or if there is a gap at the bottom of the partition wall, pinning may be formed at that portion, and the light emitting layer. This is because it becomes difficult to form a film in the film shape as designed.
(10) In the organic EL display panel 10 according to the above embodiment, the pixel electrode 13 is an anode and the counter electrode 17 is a cathode, but the present invention is not limited to this, and the pixel electrode 13 is a cathode and the counter electrode 17 is an anode. It may be a structure. When the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer and the like are provided, the stacking order thereof is also appropriately modified depending on the positions of the cathode and the anode.

(11) Further, the organic EL 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.
(12) As shown in FIG. 17, the organic EL display panel shown in the above embodiment is used as a display panel for a display unit 301 of a television 300 and various electronic devices such as a personal computer, a form terminal, and a commercial display. be able to.
≪Supplement≫
The organic EL display panel and its manufacturing method, the organic EL display device, and the electronic device according to the present disclosure have been described above based on the embodiments and modifications, but the present invention has been described in the above embodiments and modifications. It is not limited. By arbitrarily combining the components and functions in the embodiment and the modified example, the form obtained by applying various modifications that a person skilled in the art can think of, and the embodiment and the modified example without departing from the spirit of the present invention. The realized form is also included in the present invention.

The organic EL display panel according to the present disclosure can be widely used as a display panel used in various electronic devices.

1 Organic EL display device 2 Organic EL display device 10 Organic EL display panel 11 Substrate 12 Thin film transistor 13 Pixel electrode 14 Partition 15 Hole injection layer 16 Hole transport layer 17 Light emitting layer 18 Electron transport layer 19 Electron injection layer 20 Opposite electrode 21 Sealing layer 100B, 100G, 100R Sub-pixel 111 Base material 112 TFT layer 125R, 125G Digging part 140 Partition material layer 141 Pixel regulation layer

Claims (8)

With the board
The interlayer insulating layer formed on the substrate and
The organic EL light emitting portion formed on the interlayer insulating layer and
It is an organic EL display panel equipped with
The organic EL light emitting unit is
A plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer, a plurality of partition walls arranged between the pixel electrodes adjacent in the row direction and extending in the column direction, and a region partitioned by the partition wall are formed. The organic layer including the light emitting layer and the counter electrode formed above the organic layer are included.
The organic EL light emitting unit includes a first light emitting unit having a light emitting layer that emits a first color, and a second light emitting unit having a light emitting layer that emits a second color different from the first color.
Wherein the first light emitting portion second light emitting unit, the layer thickness of the organic layer is different Rutotomoni, engraved interlayer insulating layer in the regions divided by the first light emitting portion and said partition wall of the second light-emitting portion The amount is different ,
Of the first light emitting unit and the second light emitting unit, the light emitting unit having a longer wavelength of the light emitting color is an organic EL display panel in which the amount of digging of the interlayer insulating layer is larger than that of the other light emitting unit . The height of the pinning position where the upper surface of the organic layer and the partition wall are in contact with each other, the difference between the height of the center position of the upper surface of the organic layer, the organic EL display panel according to claim 1 is 700nm or less. The organic EL display panel according to claim 1 or 2 , wherein the bottom surface of the dug portion of the interlayer insulating layer is flat. The organic EL display panel according to any one of claims 1 to 3 , wherein the pixel electrode is made of a metal thin film having light reflectivity. The organic EL display panel according to any one of claims 1 to 4 ,
An organic EL display device including a drive unit that drives the organic EL display panel to display an image. An electronic device including the organic EL display device according to claim 5 as an image display unit. The first step of preparing the board and
The second step of forming the interlayer insulating layer on the substrate and
The third step of forming the organic EL light emitting portion on the interlayer insulating layer,
It is a manufacturing method of an organic EL display panel including
The organic EL light emitting unit is
A plurality of pixel electrodes arranged in a matrix on the interlayer insulating layer, a plurality of partition walls arranged between the pixel electrodes adjacent in the row direction and extending in the column direction, and a region partitioned by the partition wall are formed. A first light emitting portion having a light emitting layer including a light emitting layer and a counter electrode formed above the organic layer and emitting a first color, and a second light emitting portion different from the first color. Including a second light emitting part having a light emitting layer that emits color,
The layer thickness of the organic layer is different between the first light emitting portion and the second light emitting portion, and in the second step, interlayer insulation is provided in the region of the first light emitting portion and the second light emitting portion separated by the partition wall. Digging of different depths is formed in the layers ,
A method for manufacturing an organic EL display panel in which, of the first light emitting unit and the second light emitting unit, the light emitting unit having a longer wavelength of the light emitting color has a deeper digging of the interlayer insulating layer than the other light emitting unit . The interlayer insulating layer is made of a photosensitive resin material.
The method for manufacturing an organic EL display panel according to claim 7 , wherein in the second step, a halftone mask is used to dig a different depth in the interlayer insulating layer in one photolithography step.

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