JP2015207526A - Method of forming functional layer of organic light emission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a functional layer forming method for an organic light emission device in which when a functional layer is formed in each groove space by a wet method with respect to a bank-appended substrate having plural first banks formed along the surface of a base substrate and plural second banks formed in respective groove spaces comparted by the first banks, occurrence of dispersion in film thickness of the functional layer between pixel areas adjacent to each other through the second bank can be suppressed.SOLUTION: In a process of forming a hole transport layer or hole injecting and transporting layer 116, ink is selectively coated on a second bank 114 in a groove space 125 in a first coating step, and a coated ink layer 116a is dried to form a lower layer 116A on the second bank 114. Ink is uniformly coated on the whole groove space 125 in a second coating step. An ink layer is formed in the groove space 125 so as to cover the ink layer 116a and dried, whereby an upper layer is formed to cover the lower layer 116A.

Description

  The present invention relates to a forming method for forming a functional layer in an organic light emitting device, and more particularly to a method for forming a functional layer by applying ink to a region partitioned by a bank.

In recent years, an organic EL device in which a plurality of organic EL elements are arranged in a matrix on a substrate has been put to practical use as a light-emitting display device. This organic EL device has high visibility because each organic EL element emits light, and is excellent in impact resistance because it is a complete solid element.
In the organic EL device, each organic EL element has a basic structure in which a light emitting layer containing an organic light emitting material is disposed between a pair of electrodes of an anode and a cathode, and a voltage is applied between the pair of electrodes during driving. Is applied, and light is emitted along with recombination of holes injected from the anode into the light emitting layer and electrons injected from the cathode into the light emitting layer. In an organic EL device for full-color display, such an organic EL element forms RGB subpixels, and adjacent RGB subpixels are combined to form one pixel.

  In an organic EL device, the light emitting layer of each organic EL element and the light emitting layer of an adjacent organic EL element are generally partitioned by a bank made of an insulating material. Further, an organic layer such as a hole injection layer, a hole transport layer, or a hole injection / transport layer is interposed between the anode and the light emitting layer as necessary, and also between the cathode and the light emitting layer as necessary. An electron injection layer, an electron transport layer, or an electron injection / transport layer is interposed. These organic layers, hole injection layers, hole transport layers, hole injection / transport layers, electron injection layers, electron transport layers, electron injection / transport layers, and the like are collectively referred to as functional layers.

  When manufacturing such an organic EL device, a striped bank (so-called “line bank”) extending in one direction is formed on a substrate, and a functional layer is formed in a groove space defined by the line bank. There is a process to do. For forming the functional layer, a wet method in which an ink for forming a light emitting layer containing a polymer material or a low molecule having a good thin film formability is applied to a concave space by an inkjet method or the like is often used. According to this wet method, an organic layer and a light emitting layer can be formed relatively easily even in a large panel.

Like the image display device disclosed in Patent Document 1, in addition to the line bank (first bank), the second bank having a height lower than the first bank in the direction orthogonal to the first bank is provided on the substrate. In some cases, adjacent pixel regions are partitioned by forming.
In this way, the functional layer forming ink is continuously applied to the entire groove space between the first banks on the substrate in which the first bank and the second bank are formed, thereby forming the groove space. It is possible to form a functional layer with relatively little thickness unevenness in the direction in which the film extends.

JP 2007-234232 A

However, even if ink is continuously applied to the entire groove space partitioned by the first bank as described above to form the functional layer, the film of the functional layer is formed between adjacent pixels across the second bank. Variations in thickness may occur. If the film thickness of the functional layer is different between adjacent pixel regions in this way, the light emission characteristics between the pixels are different, causing image quality degradation.
The present invention has been made in view of the above problems, and is divided by a base substrate, a plurality of first banks extending in one direction along the surface of the base substrate, and a plurality of first banks. When a functional layer is formed in each groove space by a wet method with respect to a banked substrate having a plurality of second banks formed at intervals in one direction in each groove space, the second bank is It is an object to suppress the variation in the thickness of the functional layer between pixel regions adjacent to each other.

  A method for forming a functional layer according to one embodiment of the present invention includes a base substrate, a plurality of first banks extending in one direction along the surface of the base substrate, and a plurality of first banks defined by the plurality of first banks. A formation method for preparing a banked substrate having a plurality of second banks formed at intervals in one direction in a groove space, and forming a functional layer of an organic light emitting device in each groove space, In each groove space of the substrate, a part of the functional layer is formed by selectively applying and drying the first ink containing the material of the functional layer on the plurality of second banks. The remaining part of the functional layer was formed by applying and drying the second ink containing the material of the layer so as to cover a part of the functional layer.

  The drying of the ink here means drying to the extent that the applied ink layer loses its fluidity. Therefore, it includes not only the case of complete drying but also the case of semi-drying.

  According to the method for forming a functional layer according to the above aspect, a lower layer that is a part of the functional layer is formed on the second bank by applying and drying the first ink. Since this lower layer has affinity for the second ink, when the applied second ink dries, the state in which the ink layer is adhered to the lower layer is maintained, and the upper layer of the functional layer is formed on the lower layer. Is formed. As a result, variation in the thickness of the functional layer between pixel regions adjacent to each other across the second bank is suppressed, and the uniformity of the thickness is improved.

  In addition, when an unwetted region occurs when ink is applied to the groove space, a portion where the thickness of the functional layer becomes thin is generated in the vicinity thereof, which may cause luminance unevenness in the pixel. According to the method for forming the functional layer, the non-wetting region does not easily occur, so that the luminance unevenness in the pixel hardly occurs.

1 is a schematic block diagram showing a schematic configuration of an organic EL display device 1 according to an embodiment of the present invention. 3 is a schematic plan view showing an arrangement form of sub-pixels 11a, 11b, and 11c in the display panel 10. FIG. It is a schematic cross section which shows the structure in the AA cross section of FIG. 3 is a process diagram showing a manufacturing process of the display panel 10. FIG. It is a schematic perspective view of the board | substrate 150 with a bank. (A), (b) is a top view which shows the mode of the ink application of the 1st time and the 2nd time. (A)-(c) is a cross-sectional schematic diagram which shows the mode of the 1st ink application | coating. (A)-(c) is a cross-sectional schematic diagram which shows the mode of the 2nd ink application. (A)-(d) is a figure explaining the mechanism in which film thickness dispersion | variation etc. generate | occur | produce in the formation method of the hole transport layer or hole injection and transport layer 116 concerning a comparative example. (A)-(d) is a figure explaining the mechanism in which generation | occurrence | production of film thickness dispersion | variation etc. is suppressed in the formation method of the hole transport layer or hole injection and transport layer 116 concerning embodiment.

[Background to Invention]
As described above, the inventor has a base substrate, a plurality of first banks extending in one direction along the surface of the base substrate, and a groove space defined by the plurality of first banks. When the functional layer of the organic light emitting device is formed on the substrate with bank having the plurality of second banks formed by applying ink to each groove space, the thickness of the formed functional layer is a pixel. The cause of the variation was considered as follows.

When ink is applied to the entire groove space between the first banks, the applied ink layer also covers the second bank, but the volume of the ink decreases in the process of drying the ink layer, so that the drying progresses to some extent. At this stage, the ink layer on the second bank is distributed in such a manner that it is drawn into the ink layers in the pixel regions on both sides of the second bank.
At this time, it suffices that half of the pixels are distributed to the adjacent pixel regions, but the distribution may be uneven. In that case, the amount of ink in the pixel regions on both sides becomes non-uniform, and the thickness of the formed functional layer is different.

In particular, the ink containing the material for the hole transport layer is likely to be repelled on the second bank, and a case where no ink remains on the second bank is likely to occur.
Therefore, it was considered that the ink layer formed by applying ink in the groove space should remain on the second bank without being repelled on the second bank even during drying. Then, a method for keeping the ink layer on the second bank when the ink layer is dried has been studied, and the present invention has been achieved.

[Aspect of the Invention]
A method for forming a functional layer according to one embodiment of the present invention includes a base substrate, a plurality of first banks extending in one direction along the surface of the base substrate, and a plurality of first banks defined by the plurality of first banks. A formation method for preparing a banked substrate having a plurality of second banks formed at intervals in one direction in a groove space, and forming a functional layer of an organic light emitting device in each groove space, In each groove space of the substrate, a part of the functional layer is formed by selectively applying and drying the first ink containing the material of the functional layer on the plurality of second banks. The remaining part of the functional layer was formed by applying and drying the second ink containing the material of the layer so as to cover a part of the functional layer.

  According to the method for forming a functional layer of the above aspect, first, the first ink is selectively applied on the second bank and dried to form a part of the functional layer on the second bank. The At this time, since there is no ink layer on both sides of the second bank, the ink layer of the first ink is not pulled on both sides of the second bank with drying. Therefore, the ink layer is dried on the second bank to form a lower layer that becomes a part of the functional layer.

Since this lower layer has affinity for the second ink, when the applied second ink dries, the state in which the ink layer is adhered to the lower layer is maintained, and the upper layer of the functional layer is formed on the lower layer. Is formed. As a result, variation in the thickness of the functional layer between pixel regions adjacent to each other across the second bank is suppressed, and the uniformity of the thickness is improved.
In addition, when an unwetted region occurs when ink is applied to the groove space, a portion where the thickness of the functional layer becomes thin is generated in the vicinity thereof, which may cause luminance unevenness in the pixel. According to the method for forming the functional layer, the non-wetting region does not easily occur, so that the luminance unevenness in the pixel hardly occurs.

In the method for forming a functional layer of the above aspect, the following may be performed.
When the first ink is applied to each groove space of the banked substrate, the first ink applied on the second banks adjacent to each other is applied so as not to contact each other.
When the second ink is applied to each groove space of the banked substrate, the applied second ink is applied so as to be continuous in one direction.

The first ink and the second ink have the same composition. Here, “the same composition” means that the types of components contained in the ink are the same. As a result, a common ink can be used as the first ink and the second ink, which contributes to improved workability during ink application.
The second bank has a lower height from the surface of the base substrate than the first bank.
The second bank has a lower liquid repellency with respect to the first ink than the first bank. Thereby, the paintability of the first ink on the second bank can be enhanced, and the adhesion of the first ink onto the second bank can be enhanced.

[Embodiment]
Hereinafter, an overall configuration and a manufacturing method of the organic EL device according to the embodiment will be described, and a method for manufacturing a functional layer of the organic EL device will be described in detail.
1. Schematic Configuration A schematic configuration of the organic EL display device 1 according to the embodiment will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the organic EL display device 1 includes a display panel 10 and a drive / control circuit unit 20 connected thereto. The display panel 10 is a kind of organic light emitting device, and is an organic EL panel using an electroluminescent phenomenon of an organic material.
As shown in FIG. 2, in the display panel 10, a plurality of subpixels 11a, 11b, and 11c are two-dimensionally arranged in the X direction and the Y direction. In this display panel 10, as an example, the subpixel 11a emits red light (R), the subpixel 11b emits green light (G), and the subpixel 11c emits blue light (B). One pixel (pixel) is constituted by three subpixels 11a, 11b, and 11 adjacent in the X direction.

As shown in FIG. 1, the drive / control circuit unit 20 in the organic EL display device 1 includes four drive circuits 21 to 24 and one control circuit 25.
2 shows an example in which one pixel is configured by combining three subpixels 11a, 11b, and 11c. However, the configuration of the pixel (pixel unit) is not limited to this, and a combination of four or more subpixels is possible. May constitute one pixel.
2. Configuration of Display Panel 10 In the display panel 10, a plurality of subpixels 11a to 11c are two-dimensionally arranged on a substrate (not shown) as shown in FIG. As shown in FIG. 3, each of the subpixels 11 a to 11 c includes a plurality of first banks 115 extending in the Y direction and a plurality of first banks 115 formed at intervals in the Y direction between the first banks 115. It exists in an area (subpixel area) partitioned by two banks 114. In FIG. 5, reference numerals 12a, 12b, and 12c indicate subpixel regions corresponding to the subpixels 11a, 11b, and 11c.

FIG. 3 is a schematic cross-sectional view showing the AA cross section of FIG. 2.
The display panel 10 is based on a TFT substrate 110 in which a TFT layer 101 is formed on a substrate 100. Although not shown in detail, the TFT layer 101 includes three electrodes, a gate, a source, and a drain, a semiconductor layer, a passivation film, and the like.
An interlayer insulating layer 102 is stacked on the TFT substrate 110.

The interlayer insulating layer 102 has a substantially flat upper surface, and subpixels 11a to 11c are formed thereon.
Since the subpixels 11a to 11c have the same basic configuration, the subpixel 11a will be described as a representative.
The subpixel 11 a includes an anode 103 and a hole injection layer 104 that are sequentially stacked on the interlayer insulating layer 102.

The anode 103 is connected to the upper electrode (electrode connected to the source or drain) of the TFT layer 101 through a contact hole (not shown) provided in the interlayer insulating layer 102.
A first bank 115 is formed on the interlayer insulating layer 102 so as to cover both edges of the hole injection layer 104 in the X direction. Although not shown in FIG. 3, a second bank 114 is formed on the interlayer insulating layer 102 so as to cover both edges of the hole injection layer 104 in the Y direction (see FIGS. 7A and 7C). ).

  As shown in FIG. 3, a hole transport layer or hole injection / transport layer 116, an organic light emitting layer 117, and an electron transport layer 118 are stacked between the first banks 115. The hole transport layer or hole injection / transport layer 116, the organic light emitting layer 117, and the electron transport layer 118 are continuously formed in the Y direction, and are not only in the subpixel region but also on the second bank 114. Is also formed.

A cathode 119 and a sealing layer 120 are sequentially formed so as to entirely cover the electron transport layer 118 and the side and top surfaces of the first bank 115.
The sealing layer 120 has a function of suppressing exposure of an organic layer such as the organic light emitting layer 117 to moisture or exposure to air.
A substrate 124 having a black matrix layer 122 and a color filter layer 123 is bonded to the sealing layer 120 with a resin layer 121 interposed therebetween.

The display panel 10 having the above configuration is a top emission type, and emits light in the Z direction as indicated by an arrow in FIG.
3. Constituent material of display panel 10 Substrate 100:
The substrate 100 is, for example, a glass substrate, a quartz substrate, a silicon substrate, molybdenum sulfide, copper, zinc, aluminum, stainless steel, magnesium, iron, nickel, gold, silver or other metal substrate, a gallium arsenide based semiconductor substrate, a plastic substrate, or the like. Etc. are used.

As the plastic substrate, either a thermoplastic resin or a thermosetting resin may be used.
For example, polyolefin such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), cyclic polyolefin, modified polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide (PI), Polyamideimide, polycarbonate, poly- (4-methylbenten-1), ionomer, acrylic resin, polymethyl methacrylate, acrylic-styrene copolymer (AS resin), butadiene-styrene copolymer, polio copolymer (EVOH) ), Polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), precyclohexane terephthalate (PCT), polyethers, polyether ketones Polyethersulfone (PES), polyetherimide, polyacetal, polyphenylene oxide, modified polyphenylene oxide, polyarylate, aromatic polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluororesins, styrene, polyolefin Various types of thermoplastic elastomers such as polyvinyl chloride, polyurethane, fluororubber, chlorinated polyethylene, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester, silicone resin, polyurethane, or these And copolymers, blends, polymer alloys and the like. Moreover, the laminated body which laminated | stacked 1 type or 2 types or more among these can also be used.

Interlayer insulating layer 102:
In the manufacturing process of the display panel 10, an etching process, a baking process, or the like may be performed. Therefore, the interlayer insulating layer 102 is desirably formed of a material that has durability against these processes. The interlayer insulating layer 102 is formed of, for example, an organic compound such as polyimide, polyamide, or acrylic resin.

Anode 103:
Since the display panel 10 is a top emission type, the surface of the anode 103 preferably has high reflectivity. The anode 103 is made of a metal material containing silver (Ag) or aluminum (Al).
The anode 103 can be not only a single layer structure made of a metal material but also a laminate of a metal layer and a transparent conductive layer. Examples of the material for the transparent conductive layer include indium tin oxide (ITO) and indium zinc oxide (IZO).

Hole injection layer 104:
The hole injection layer 104 is formed of, for example, an oxide such as silver (Ag), molybdenum (Mo), chromium (Cr), vanadium (V), tungsten (W), nickel (Ni), iridium (Ir), or PEDOT. It is made of a conductive polymer material such as (mixture of polythiophene and polystyrene sulfonic acid).

Second bank 114:
The second bank 114 is formed of a photosensitive organic material. Specific examples of the organic material include acrylic resins, polyimide resins, siloxane resins, phenol resins, and the like.
However, the material of the second bank 114 is not limited to an organic material, and may be formed of an inorganic insulating material such as SiO ₂ (silicon oxide), SiN (silicon nitride), or SiON (silicon oxynitride).
(6) First bank 115
The material of the first bank 115 may be the same as or different from the material of the second bank 114.

The first bank 115 preferably has liquid repellency with respect to the ink for forming the hole transport layer or the hole injection / transport layer 116, the organic light emitting layer 117, and the like by a wet method. Therefore, it is preferable to use a fluorine-based resin as the material of the first bank 115.
As the structure of the first bank 115, not only a single-layer structure but also a multilayer structure of two or more layers can be adopted. In the case of a multilayer structure, the above materials can be used in combination for each layer.

Hole transport layer or hole injection / transport layer 116:
The hole transport layer or the hole injection / transport layer 116 can be formed using, for example, a polymer compound such as polyfluorene or a derivative thereof, or polyarylamine or a derivative thereof.
Organic light emitting layer 117:
Examples of the material of the organic light emitting layer 117 include liparaphenylene vinylene (PPV), polyfluorene, oxinoid compound, perylene compound, coumarin compound, azacoumarin compound, oxazole compound, oxadiazole compound, perinone compound, pyrrolopyrrole compound, naphthalene compound, Anthracene compound, fluorene compound, fluoranthene compound, tetracene compound, pyrene compound, coronene compound, quinolone compound and azaquinolone compound, pyrazoline derivative and pyrazolone derivative, rhodamine compound, chrysene compound, phenanthrene compound, cyclopentadiene compound, stilbene compound, diphenylquinone compound, Styryl compound, butadiene compound, dicyanomethylenepyran compound, dicyanomethylenethiopyran compound, full Resin compounds, pyrylium compounds, thiapyrylium compounds, serenapyrylium compounds, telluropyrylium compounds, aromatic aldadiene compounds, oligophenylene compounds, thioxanthene compounds, cyanine compounds, acridine compounds, metal complexes of 8-hydroxyquinoline compounds, 2-bipyridine compounds Examples thereof include fluorescent substances such as metal complexes, Schiff salts and Group III metal complexes, oxine metal complexes, and rare earth complexes.

Electron transport layer 118:
The electron transport layer 118 is formed of, for example, an oxadiazole derivative (OXD), a triazole derivative (TAZ), a phenanthroline derivative (BCP, Bphen), or the like.
Cathode 119:
Since the display panel 10 is a top emission type, the cathode 119 is formed of a light transmissive material. Specific examples of the material include indium tin oxide (ITO) and indium zinc oxide (IZO).

Sealing layer 120:
The sealing layer 120 is also formed of a light transmissive material.
The material of the sealing layer 120 is, for example, silicon nitride (SiN), silicon oxynitride (SiON), or the like. Further, a sealing resin layer made of a resin material such as an acrylic resin or a silicone resin may be provided over a layer formed using a material such as silicon nitride (SiN) or silicon oxynitride (SiON).

Resin layer 121:
The resin layer 121 is formed from a transparent resin material, for example, an epoxy resin material. However, other than this, a silicone resin or the like can also be used.
Black matrix layer 122:
The black matrix layer 122 is formed of an ultraviolet curable resin material containing a black pigment having excellent light absorption and light shielding properties. Examples of the ultraviolet curable resin include acrylic ultraviolet curable resin materials.

Color filter layer 123
The color filter layer 123 is formed of a material that selectively transmits visible light in the wavelength range of each color of red (R), green (G), and blue (B), for example, a material based on a known acrylic resin. .
Substrate 124:
The substrate 124 is, for example, a glass substrate, a quartz substrate, a silicon substrate, molybdenum sulfide, copper, zinc, aluminum, stainless steel, magnesium, iron, nickel, gold, silver, or a metal substrate, a gallium arsenide base, like the substrate 100 described above. For example, a semiconductor substrate, a plastic substrate, or the like can be used.

5. Manufacturing Method of Display Panel 10 A manufacturing method of the display panel 10 will be described based on the process diagram of FIG.
In manufacturing the display panel 10, first, a TFT substrate is prepared (step S1). This TFT substrate is obtained by forming the TFT layer 101 on the upper surface of the substrate 100 and is manufactured by a known technique.

Next, an organic material is applied on the TFT substrate to form the interlayer insulating layer 102 (step S2).
The substrate having the interlayer insulating layer 102 thus formed on the TFT substrate is used as a base substrate, and the anode 103 and the hole injection layer 104 are sequentially stacked on the interlayer insulating layer 102 (steps S3 and S4). The anode 103 is formed by, for example, forming a metal film using a sputtering method or a vacuum deposition method and then patterning the metal film using a photolithography method and an etching method.

The hole injection layer 104 is formed, for example, by forming a film made of a metal oxide (for example, tungsten oxide) using a sputtering method and then patterning using a photolithography method and an etching method.
Next, the second bank 114 is formed as follows (step S5).
A bank material (photosensitive photoresist material) for forming the second bank 114 is uniformly applied on the hole injection layer 104. Thereafter, the applied bank material is exposed to light using a patterned mask. Then, a second bank 114 bank pattern is formed by removing uncured excess bank material with a developer.

Next, the first bank 115 is formed as follows (step S6).
A bank material (negative photosensitive resin composition) for forming the first bank 115 is uniformly applied on the second bank 114 on the hole injection layer 104. A mask having an opening corresponding to the pattern of the first bank 115 to be formed is overlaid on the applied bank material layer and exposed from above the mask.

Thereafter, the bank material is patterned by washing out the excess bank material with an alkaline developer to form the bank pattern of the first bank 115.
A UV (ultraviolet) irradiation process and a baking process are performed on the formed second bank 114 and first bank 115 (step S7). The UV irradiation treatment is performed for 150 to 200 seconds, for example. The baking process is performed at a temperature of 150 to 230 ° C. for 10 to 20 minutes, for example.

FIG. 5 is a schematic perspective view of the banked substrate 150 in which the second bank 114 and the first bank 115 are formed on the base substrate including the substrate 100 and the interlayer insulating layer 102.
In the banked substrate 150, a plurality of groove spaces 125 defined by a plurality of first banks 115 are formed in the Y direction on the upper surface side, and each groove space 125 is partitioned by a second bank 114 to form a plurality of grooves. Sub-pixel regions 12 (12a, 12b, 12c) are formed.

  Next, a hole transport layer or a hole injection / transport layer 116 is formed in the groove space 125 defined by the adjacent first banks 115 (step S8). The hole transport layer or the hole injection / transport layer 116 is formed by a printing method (coating method), and a groove between the adjacent first banks 115 is filled with ink containing a constituent material for the hole transport layer or the hole injection / transport layer 116. It is done by baking after applying to the space.

Although this process will be described in detail later, the hole transport layer or the hole injection / transport layer 116 is also formed on the second bank 114 exposed in the groove space defined by the two adjacent first banks 115. Form.
Similarly, the organic light emitting layer 117 and the electron transport layer 118 are sequentially stacked in the groove space 125 defined by the adjacent first banks 115 (steps S9 and S10). The organic light emitting layer 117 and the electron transport layer 118 are also formed by applying an ink containing each constituent material and baking it as described above.

Next, the cathode 119 and the sealing layer 120 are sequentially stacked so as to cover the electron transport layer 118 and the top surfaces of the first banks 115 (steps S11 and S12). The cathode 119 and the sealing layer 120 can be formed using, for example, a sputtering method.
Thereafter, the display panel 10 is completed by bonding the color filter substrate on which the color filter layer 123 and the black matrix layer 122 are formed to the substrate 124 (step S13).

The dimensions of the first bank 115, the second bank 114, and the sub-pixel region 12 to be formed will be exemplified below.
The first bank 115 has a height (height from the upper surface of the interlayer insulating layer 102) of 1 μm and a width of 30 μm.
The second bank 114 has a height (height from the upper surface of the interlayer insulating layer 102) of 0.5 μm and a width of 15 to 20 μm.

The sub-pixel 11 has a length (Y direction length) of 300 μm and a width (X direction width) of 50 μm.
(Step of forming hole transport layer or hole injection / transport layer 116)
The hole transport layer or the hole injection / transport layer is performed twice by applying the ink for the hole transport layer or the hole injection / transport layer to the groove spaces 125 in the banked substrate 150 shown in FIG. 116 is formed.

FIGS. 6A and 6B are plan views showing the state of the first and second ink application.
7A to 7C are schematic cross-sectional views showing the state of the first ink application, and FIGS. 8A to 8C are schematic cross-sectional views showing the state of the second ink application.
The positions where ink is landed (landing positions) are indicated by circles in FIGS. 6 (a) and 6 (b), and are indicated by arrows in FIGS. 7 (a) and 8 (a).

First application and drying:
In the first application, as shown in FIG. 6A, the nozzle head 200 is scanned in the X direction, or the nozzle head 200 is fixed and a base (not shown) on which the banked substrate 150 is placed. ) In the X direction, ink is selectively applied on the second bank 114 in the groove space 125.

That is, it is assumed that ink is applied on the second bank 114 in the entire area of the groove space 125 and ink is not applied or applied to the area other than the second bank 114 (sub-pixel area 12). However, the application amount is reduced.
In the example shown in FIG. 6A, among the plurality of nozzles 201 provided in the nozzle head 200, the nozzle 201 with a cross (x) is not used, and only the nozzle 201 passing over the second bank 114 is used. Thus, ink is landed on the second bank 114.

Here, the ink (first ink) ejected from the nozzle head 200 is a solution obtained by dissolving the material of the hole transport layer or the hole injection / transport layer 116 in a solvent.
FIG. 7B shows a state in which the ink layer 116a is formed on the second bank 114 as a result of the first ink application.
By drying the applied ink layer 116a, a lower layer 116A is formed on the second bank 114 as shown in FIG. The lower layer 116 </ b> A is a layer that constitutes a part of the hole transport layer or the hole injection / transport layer 116.

The mode of applying the first ink will be described in more detail. In the groove space 125, one or more inks are applied on each second bank 114. When a plurality of droplets are dropped on each second bank 114, the dropping position may be one row or two rows as shown in FIG.
The ink layer 116a may cover only a part of the surface of the second bank 114 exposed in the groove space 125, or the ink layer 116a is exposed in the groove space 125 as in the example shown in FIG. The entire surface of the second bank 114 may be covered.

  In the example shown in FIG. 7B, the ink layer 116 a is formed not only on the second bank 114 but also across the peripheral portion of the sub-pixel region 12. As described above, the ink layer 116a may straddle the peripheral portion of the sub-pixel region 12, but the ink layers 116a applied on the second banks adjacent in the Y direction are separated from each other so as not to be connected. To.

The drying of the ink layer 116a is preferably performed under reduced pressure because it can be quickly dried at a low temperature.
Second application and drying:
As shown in FIG. 6B, ink is applied to the entire groove space 125 while scanning the nozzle head 200 in the X direction. At the time of the second application, the ink is uniformly applied to the entire groove space 125 using the plurality of nozzles 201 provided in the nozzle head 200 as a whole.

The ink (second ink) used here is also a solution obtained by dissolving the material of the hole transport layer or the hole injection / transport layer 116 in a solvent. The second ink may have the same composition as the first ink used for the first application (that is, the same type of solvent), or the type of solvent may be different.
FIG. 8B shows a state in which an ink layer 116 b that covers the ink layer 116 a and is continuous in the Y direction is formed in the groove space 125 as a result of the second ink application. The height of the ink layer 116b immediately after application is, for example, about 20 μm.

By drying the applied ink layer 116b, as shown in FIG. 8C, an upper layer 116B covering the lower layer 116A is continuously formed in the Y direction.
The ink layer 116b is also preferably dried by drying under reduced pressure.
The upper layer 116B is a layer constituting the remaining part of the hole transport layer or the hole injection / transport layer 116. That is, the lower layer 116A and the upper layer 116B are combined to form the hole transport layer or the hole injection / transport layer 116.

The thickness of the hole transport layer or hole injection / transport layer 116 after drying is several tens of nm (for example, 20 nm).
(Effects of the hole transport layer or hole injection / transport layer 116)
According to the method of forming the hole transport layer or the hole injection / transport layer 116, the lower layer 116A is formed on the second bank 114 by the first ink application and drying. The lower layer 116A has affinity for the ink layer 116b formed by ink application for the second time. This is because the solute of the ink layer 116b and the lower layer 116A are made of the same hole transport layer or hole injection / transport layer 116 material.

Therefore, when the ink layer 116b is dried, the state in which the ink layer 116b is attached on the lower layer 116A is maintained, and the upper layer 116B is also formed on the lower layer 116A. As a result, the hole transport layer or the hole injection / transport layer 116 formed in the groove space 125 has good film thickness uniformity.
In addition, when an unwetted region is generated, a portion where the film thickness is reduced is generated in the vicinity thereof, which may cause luminance unevenness in the pixel. The method for forming the hole transport layer or the hole injection / transport layer 116 described above According to the above, since the non-wetting region of the hole transport layer or the hole injection / transport layer 116 is unlikely to occur, luminance unevenness hardly occurs in the pixel.

This effect will be described below in comparison with a comparative example.
FIG. 9 shows the mechanism of the variation in film thickness of the hole transport layer or hole injection / transport layer 116 between pixels, the hole transport layer or the hole transport layer or hole injection / transport layer 116 according to the comparative example. It is a figure explaining the mechanism in which the non-wetting area | region of the hole injection and transport layer 116 generate | occur | produces. FIG. 10 shows a variation in the film thickness of the hole transport layer or hole injection / transport layer 116 between pixels and the hole transport layer or hole in the method for forming the hole transport layer or hole injection / transport layer 116 according to the embodiment. It is a figure explaining the mechanism in which generation | occurrence | production of the unwetted area | region of the injection | pouring and transport layer 116 is suppressed.

In the method of forming the hole transport layer or hole injection / transport layer 116 according to the comparative example, the ink for forming the hole transport layer or hole injection / transport layer 116 is applied to the entire groove space 125 at one time.
At this time, as shown in FIG. 9A, an ink layer is formed in the entire groove space 125, and the second bank 114 is also covered with the ink layer.

As the ink layer is dried, the ink layer tends to shrink toward the center of the subpixel. Accordingly, in the subpixel peripheral portion (near the second bank 114) in the ink layer, FIG. As shown by the white arrow in (b), a force F1 directed toward the center of the sub-pixel acts.
With this force F1, as shown in FIG. 9C, the portion of the ink layer on the second bank 114 is separated from the second bank 114 and positioned on both sides of the second bank 114 (both sides in the Y direction). Move to one of the subpixels. At this time, it is not particularly determined which subpixel the subpixels located on both sides of the portion of the ink layer on the second bank 114 move across the second bank 114.

Accordingly, among the plurality of subpixels, there are subpixels in which a large portion of the ink layer on the second bank 114 flows, and subpixels in which a small amount of the ink layer flows. The film thickness of the cum transport layer 116 varies.
When the display panel 10 is manufactured using the hole transport layer or the hole injection / transport layer 116 having a variation in film thickness as described above, the luminance varies among the sub-pixels.

In addition, when ink is applied by the method of the comparative example, an unwet area in which no ink layer exists on the second bank 114 is generated by the force F1, and a hole transport layer or a sub-pixel is formed in the peripheral area of the subpixel. A portion where the thickness of the hole injection / transport layer 116 is considerably thin may occur.
In FIG. 9D, the thickness of the hole transport layer or the hole injection / transport layer 116 is reduced in the region indicated by C.

Thus, when the display panel 10 is manufactured using a thin portion of the hole transport layer or the hole injection / transport layer 116 in the peripheral portion of the subpixel, the light emission becomes abnormal in the thin portion and the luminance is increased. Cause unevenness.
On the other hand, according to the method for forming the hole transport layer or hole injection / transport layer 116 according to the embodiment, the ink layer 116a is formed on each second bank 114 by the first ink application. At this time, as shown in FIG. 7B, since the ink layers 116a applied on the second banks adjacent in the Y direction are not connected to each other, the ink layer 116a is also dried and contracts. The ink layer 116 a is not pulled to the center of the subpixel region 12.

Therefore, the ink layer 116 a is not peeled off from the second bank 114, and the lower layer 116 A is formed on the second bank 114.
Next, by the second ink application, an ink layer 116b is formed in the entire groove space 125 so as to cover the lower layer 116A formed on the second bank 114 as shown in FIG.
When the ink layer 116b is dried, the ink layer 116b tends to shrink toward the center of the pixel. Accordingly, in the pixel peripheral portion (the vicinity of the second bank 114) in the ink layer 116b, FIG. The point where the force F1 acts as shown by the white arrow in (b) and (c) is the same as in the comparative example.

  However, since the lower layer 116A and the ink layer 116b are made of the same material as described above, the lower layer 116A and the ink layer 116b always have an affinity. Therefore, the ink layer 116b is not separated from the lower layer 116A and remains on the second bank 114. Therefore, the force F2 indicated by the white arrow acts in the direction opposite to the force F1 in the pixel peripheral portion in the ink layer 116b. As a result, the amount of the ink layer portion on the second bank 114 flowing into the sub-pixel is also reduced.

As a result, the formed hole transport layer or hole injection / transport layer 116 also exists on the second bank as shown in FIG. 10D, and the hole transport layer or hole injection / transport layer 116 is located between the sub-pixels. Therefore, variation in luminance between sub-pixels can also be suppressed.
Further, there is no occurrence of an unwetted area where no ink layer exists on the second bank 114 in the peripheral area of the pixel in the ink layer 116b, and the film thickness of the hole transport layer or the hole injection / transport layer 116 in the peripheral area of the pixel. The phenomenon of thinning is also suppressed.

Therefore, it is possible to suppress the occurrence of luminance unevenness in the pixel when the display panel 10 is manufactured.
In the hole transport layer or the hole injection / transport layer 116, the portion existing above the second bank does not contribute to light emission, but does not adversely affect the light emission characteristics.
[Modifications, etc.]
(1) By changing the bank material used for the first bank and the second bank, or by changing the UV processing conditions for the first bank and the second bank, the second bank is better than the first bank. The liquid repellency with respect to ink may be lowered. Thereby, the affinity of the ink with respect to the second bank is improved, and the effect of suppressing the film thickness variation of the hole transport layer or the hole injection / transport layer 116 can be further enhanced.

(2) The viscosity of the first ink may be increased and the viscosity of the second ink may be decreased.
By increasing the viscosity of the first ink, the ink layer applied on the second bank can be kept on the second bank without spreading over the sub-pixel region at the first ink application.
(3) In the above embodiment, the case where the hole transport layer or the hole injection / transport layer 116 of the display panel 10 is formed by the wet method has been described. However, the functional layers other than the hole transport layer or the hole injection / transport layer are formed by the wet method. For example, when the light emitting layer, the hole injection layer, the electron transport layer, and the electron injection layer are formed by a wet method, the same effect can be obtained and the same effect can be obtained.

Further, the present invention is not limited to the organic EL display panel, and can be applied to, for example, a case where a functional layer in organic EL illumination is formed, and the same effect can be obtained.
(4) In the above embodiment, the case where the functional layer of the top emission type display panel 10 is formed has been described as an example. However, the embodiment can also be applied to form the functional layer of the bottom emission type display panel. Similar effects can be obtained.

  The method for forming a functional layer according to the present invention is useful for manufacturing an organic light emitting device such as an organic EL display device.

DESCRIPTION OF SYMBOLS 1 Organic EL display device 10 Display panel 11a-11c Subpixel 12a-12c Subpixel area | region 100 Substrate 101 TFT layer 102 Interlayer insulating layer 103 Anode 104 Hole injection layer 110 TFT substrate 114 Second bank 115 First bank 116b Ink layer 116 Hole Transport layer or hole injection / transport layer 116A Lower layer 116B Upper layer 116a Ink layer 117 Organic light emitting layer 118 Electron transport layer 119 Cathode 120 Sealing layer 121 Resin layer 122 Black matrix layer 123 Color filter layer 124 Substrate 125 Groove space 150 Substrate with bank 200 Nozzle head 201 nozzle

Claims (6)

A base substrate, a plurality of first banks extending in one direction along the surface of the base substrate, and a groove space defined by the plurality of first banks spaced apart in the one direction. A formation method of preparing a banked substrate having a plurality of second banks and forming a functional layer of an organic light emitting device in each groove space,
A part of the functional layer is formed by applying and drying a first ink containing the material of the functional layer on a plurality of second banks selectively in each groove space of the banked substrate. ,
Applying the second ink containing the material of the functional layer to each groove space so as to cover a part of the functional layer and drying, thereby forming the remaining part of the functional layer.
A method for forming a functional layer. When the first ink is applied to each groove space of the banked substrate, the first ink applied on the second banks adjacent to each other is applied so as not to contact each other.
The method for forming a functional layer according to claim 1. When applying the second ink to each groove space of the banked substrate,
The applied second ink is applied so as to be continuous in the one direction.
The method for forming a functional layer according to claim 1. The first ink and the second ink have the same composition.
The method for forming a functional layer according to claim 1. The second bank is lower in height from the surface of the base substrate than the first bank.
The method for forming a functional layer according to claim 1. The second bank has less liquid repellency with respect to the first ink than the first bank.
The method for forming a functional layer according to claim 1.

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