JP2011249035A - Organic el display panel and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL display panel that suppresses luminance unevenness and has a high display quality.SOLUTION: An organic EL display panel 10 includes a substrate 100; a plurality of pixel electrodes 210 arrayed on the substrate 100 to constitute an image display region 900; an organic functional layer 650 including a light emitting layer 600 formed by a coating method and made of a light emitting material, and arranged on the pixel electrodes; a counter electrode 220 arranged on the organic functional layer 650 and shared for the plurality of pixel electrodes 210; a wall-like sealing portion 750 arranged on the substrate 100 so as to surround an outer periphery of the image display region 900; and a sealing plate 700 arranged on the sealing portion 750. The counter electrode 220 is arranged even on an inner wall surface 770 of the sealing portion.

Description

  The present invention relates to an organic EL display panel and a manufacturing method thereof.

  An organic EL display panel is a display panel having a light emitting element (organic EL element) using electroluminescence of an organic compound. The organic EL display panel includes an organic EL element including a pixel electrode, an organic light emitting layer disposed on the pixel electrode, and a counter electrode disposed on the organic light emitting layer. The organic EL material contained in the organic light emitting layer is roughly classified into a combination of a low molecular organic compound (host material and dopant material) and a high molecular organic compound. Examples of the macromolecular organic compound include polyphenylene vinylene called PPV and derivatives thereof. An organic EL display panel using a polymer organic compound can be driven at a relatively low voltage, consumes less power, and is easily adapted to an increase in the size of the display panel.

  The high molecular organic compound can be in the form of a solution dissolved in an aromatic organic solvent such as xylene or toluene. For this reason, it is possible to apply a solution of a polymer organic compound (hereinafter also simply referred to as “ink”) to a predetermined location by a printing method such as an ink jet method to form an organic light emitting layer. That is, as a method of arranging the polymer compound at an appropriate location, it is said that it is easy to cope with the enlargement of the screen of the display panel by adopting a simple and high-capacity inkjet method.

  The organic EL element is a laminated device composed of a plurality of layers such as a pixel electrode, a hole injection layer, and an organic light emitting layer. And it can be said that the film thickness of each layer is an important element which influences the light emission characteristic of an organic EL element. In particular, a high degree of uniformity is required for the thickness of the organic light emitting layer that directly contributes to light emission. The variation in the thickness of the organic light emitting layer causes “brightness unevenness” in the organic EL display panel, which leads to display quality defects in the organic EL display panel.

  In the case of forming an organic light emitting layer by a printing method such as an ink jet method, first, ink is applied to the inside of a partition wall that defines a pixel called a bank. Next, an organic light-emitting layer having a thickness of about 100 nm can be formed by evaporating the organic solvent contained in the ink and drying the ink. It is known that the film thickness and film shape of the organic light emitting layer to be formed depend on the ink drying process.

  For example, even in the case of pixels arranged in the same pixel region on the substrate, the shape of the formed organic light emitting layer may vary. Specifically, the organic light emitting layer in the pixel arranged in the peripheral portion of the pixel display region may have a shape inclined toward the outside of the substrate. This is because the vapor concentration of the organic solvent at the peripheral portion of the pixel region is lower than that at the central portion, and the ink drying rate increases at the peripheral portion of the pixel region. And with the enlargement of a display panel, the variation in the shape of the organic light emitting layer due to the difference in drying speed tends to be particularly remarkable.

  In order to solve the above problems, a method is known in which dummy pixels that do not contribute to light emission are provided around a pixel display region that contributes to light emission, and only pixels having a uniform film thickness emit light (for example, Patent Document 1). Also, by temporarily providing a removable partition enclosure around the ink application area and drying it, the increase in the drying speed at the end of the application area is suppressed, and the application area surface is uniformly dried. A method for forming a uniform film is known (see, for example, Patent Document 2).

Japanese Patent No. 3628997 JP 2007-90200 A

  However, the method described in the cited document 1 has a problem that the display performance of the panel is deteriorated because the ratio of the area of the light emitting region to the panel area is reduced. In addition, since it is necessary to apply ink to a portion that does not contribute to light emission, there is a problem that the use efficiency of the material is lowered and the manufacturing cost of the panel is increased.

  Further, according to the method described in the cited document 2, it is necessary to attach a partition enclosure to the substrate and to remove the partition enclosure from the substrate after the ink is dried. For this reason, fine particles (dust) are likely to be generated when the partition enclosure is mounted and removed. Therefore, when the generated particles adhere to the substrate, the display quality of the display panel deteriorates, and there is a problem that the manufacturing yield decreases.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to suppress the occurrence of luminance unevenness and to provide an organic EL display panel with high display quality, and a method for manufacturing the same. Is to provide.

  That is, according to the present invention, the following organic EL display panel and a method for manufacturing the organic EL display panel are provided.

[1] A substrate, and a plurality of pixel electrodes arranged on the substrate and constituting an image display area,
An organic functional layer disposed on the pixel electrode, including a light emitting layer made of a light emitting material formed by a coating method; and a counter electrode disposed on the organic functional layer and shared with the plurality of pixel electrodes; A wall-shaped sealing portion disposed on the substrate so as to surround an outer periphery of the image display region, and a sealing plate disposed on the sealing portion, and the counter electrode includes the sealing member An organic EL display panel also arranged on the inner wall surface of the stop.

  [2] The organic EL display panel according to [1], wherein the sealing portion is formed of a fired product of glass frit.

  [3] The organic EL display panel according to [1] or [2], wherein a gap is formed inside the sealing portion.

  [4] A step of arranging a plurality of pixel electrodes constituting the image display region on the substrate, a step of applying an ink containing a light emitting material and a volatile organic solvent on the pixel electrode, Forming an outer peripheral wall having a height of 3 mm or more surrounding the outer periphery on the substrate; drying the ink applied on the pixel electrode to form a light emitting layer; and forming the light emitting layer on the light emitting layer and the outer peripheral wall. A step of forming a counter electrode on an inner wall surface; and a wall-shaped sealing portion disposed so as to surround the outer periphery of the image display area by disposing a sealing plate on the outer peripheral wall and crushing the outer peripheral wall. Forming an organic EL display panel.

  [5] The method for manufacturing an organic EL display panel according to [4], wherein the squeezed outer peripheral wall is baked with a laser to form the sealing portion.

  [6] The method for producing an organic EL display panel according to [4] or [5], wherein the outer peripheral wall is formed using a glass frit material.

  [7] The method for producing an organic EL display panel according to [6], wherein the glass frit material contains an organic solvent of the same type as the organic solvent contained in the ink.

  [8] The method for manufacturing an organic EL display panel according to any one of [4] to [7], wherein the outer peripheral wall is formed on the substrate with a distance of 100 μm or more from an edge of the image display region.

  [9] The method for manufacturing an organic EL display panel according to any one of [4] to [8], wherein an upper portion of the outer peripheral wall is inclined in an outer peripheral direction of the substrate.

  [10] The method for manufacturing an organic EL display panel according to any one of [4] to [9], wherein the outer peripheral wall has a step shape that is higher on the outside than on the inside.

  Since the organic EL display panel of the present invention has a uniform light emitting layer thickness, the occurrence of luminance unevenness is suppressed, and the display quality is extremely high.

  According to the method for manufacturing an organic EL display panel of the present invention, in a state where an outer peripheral wall having a predetermined height is formed so as to surround the outer periphery of the image display region, the ink containing the light emitting material applied to the predetermined portion is dried. Therefore, the drying speed of the ink can be made uniform, and the film thickness of the formed light emitting layer can be made uniform. For this reason, according to the manufacturing method of the organic EL display panel of this invention, generation | occurrence | production of a brightness nonuniformity is suppressed and an organic EL display panel with high display quality can be manufactured.

It is a top view which shows typically one Embodiment of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows typically one Embodiment of the manufacturing method of the organic electroluminescent display panel of this invention. It is sectional drawing which shows an example of the structure of an outer peripheral wall typically. It is sectional drawing which shows typically the other example of the structure of an outer peripheral wall. It is sectional drawing which shows typically the other example of the structure of an outer peripheral wall. It is a graph which shows the vapor | steam density | concentration on a board | substrate when there is no outer peripheral wall computed by the fluid analysis. It is a graph which shows the vapor | steam density | concentration on a board | substrate with and without an outer peripheral wall calculated by the fluid analysis. It is a graph which shows the measurement result of the film | membrane profile of the light emitting layer (dry film | membrane) formed in Reference Example 1. 6 is a graph showing the measurement results of the film profile of the light emitting layer (dry film) formed in Comparative Reference Example 1. It is a graph which shows the measurement result of the film | membrane profile of the light emitting layer (dry film | membrane) formed in the comparative reference example 2. It is a top view which shows typically the pattern of the light emitting layer, bank, and outer peripheral wall which were formed on the glass substrate in the reference example 1. FIG. It is XX sectional drawing of FIG. 12A.

1. Manufacturing method of organic EL display panel The manufacturing method of the organic EL display panel of the present invention includes (1) a step of arranging a plurality of pixel electrodes on a substrate (hereinafter also referred to as “first step”), and (2) light emission. A step of applying ink containing a material on the pixel electrode (hereinafter also referred to as “second step”), and (3) a step of forming an outer peripheral wall having a predetermined height on the substrate surrounding the outer periphery of the image display region ( (Hereinafter also referred to as “third step”), (4) a step of drying the ink to form a light emitting layer (hereinafter also referred to as “fourth step”), and (5) a step of forming a counter electrode (hereinafter referred to as “fourth step”). And (6) a step of disposing a sealing plate on the outer peripheral wall (hereinafter also referred to as “sixth step”).

  In the method for producing an organic EL display panel of the present invention, (i) a step of applying an ink containing a light emitting material, (ii) a predetermined height so as to surround an outer periphery of a region to which the ink is applied (image display region). One of the features includes a step of forming an outer peripheral wall on the substrate, and (iii) a step of drying the ink to form a light emitting layer. As described above, in the manufacturing method of the present invention, since the periphery of the applied ink is dried in a state surrounded by the outer peripheral wall, a local increase in the ink drying speed at the end of the image display region can be suppressed. For this reason, the film thickness of the light emitting layer formed can be made uniform.

  In addition, the execution order of the step (i) and the step (ii) is not particularly limited, and any step may be executed first. However, it is preferable to perform the step (ii) after the step (i) because the ink can be easily applied to a more accurate location without being restricted by the presence of the outer peripheral wall.

The drying speed (flux) of the ink can be expressed by the following formula (1) from Fick's law.
J = −D · (dc / dx) (1)
(J: flux, D: diffusion coefficient, c: vapor concentration, x: position)

  From the above equation (1), it can be seen that the drying speed of the ink can be expressed as a function of the vapor concentration of the organic solvent contained in the ink. For this reason, in order to uniformly dry the ink in the application region, it is necessary that the vapor concentration is uniform on the application region. In addition, since the interaction of the vapor is small in the outer portion of the application region, the ink tends to diffuse and the vapor concentration tends to be small.

  FIG. 7 is a graph showing the vapor concentration on the substrate calculated by fluid analysis when there is no outer peripheral wall. FIG. 7 shows the distribution of the vapor concentration of cyclohexylbenzene (CHB) after standing for 120 seconds under atmospheric pressure conditions after ink application. This fluid analysis was performed using a product name “FLUENT” (manufactured by Fluent Asia Pacific), which is general-purpose computational fluid dynamics software.

  As shown in FIG. 7, the vapor concentration gradually decreases as the distance from the center of the substrate increases, and the vapor concentration rapidly decreases at the end of the application region. Thus, it can be seen that the vapor concentration is relatively high at the center of the substrate and the ink drying speed is slow. On the other hand, it is considered that the ink drying speed is fast at the edge of the substrate. It is presumed that this causes uneven drying of the ink within the surface of the substrate, resulting in variations in the shape of the formed dry film (light emitting layer). The variation in the shape of the light emitting layer leads to luminance unevenness, which causes the display characteristics of the organic EL display panel to deteriorate.

  FIG. 8 is a graph showing the vapor concentration on the substrate in “when there is an outer peripheral wall” and “when there is no outer peripheral wall” calculated by fluid analysis. As shown in FIG. 8, when the height of the outer peripheral wall is 1 mm, it can be seen that the vapor concentration distribution is the same as that without the outer peripheral wall. On the other hand, when the height of the outer peripheral wall is 3 mm, it is clear that the decrease in the vapor concentration at the end of the substrate is suppressed. Therefore, it is clear that not only the outer peripheral wall but also the ink drying unevenness can be suppressed by setting the outer peripheral wall to a predetermined height or more. This is because, when the outer peripheral wall is lower than the amount of ink vapor generated, the ink vapor leaks out over the outer peripheral wall. If the outer peripheral wall is sufficiently higher than the amount of ink vapor generated, it is considered that the ink vapor is stored in the region surrounded by the outer peripheral wall.

  In the manufacturing method of the present invention, the sealing portion is formed using the outer peripheral wall, and the substrate and the sealing plate are bonded. That is, the outer peripheral wall used for uniformly drying the ink is used as a member constituting the organic EL display panel. Therefore, since there is no step of removing the outer peripheral wall, fine particles (dust) generated with the removal of the outer peripheral wall do not adhere to the substrate or the like. For this reason, it is difficult for the display quality of the display panel to deteriorate due to contamination of dust and the like, and the manufacturing yield can be improved.

  Hereinafter, each step of the manufacturing method of the organic EL display panel of the present invention will be described in detail.

(First step)
In the first step, a plurality of pixel electrodes are formed in a matrix on the substrate. The pixel electrode is formed, for example, by forming an electrode material film on a substrate by sputtering or the like, then masking the electrode material film with a resist, and then etching and patterning. The film thickness of the pixel electrode is preferably about 100 to 200 nm. If the film thickness of the pixel electrode is too thin, the film thickness tends to be non-uniform.

  Note that a hole injection layer may be formed over the pixel electrode. The material of the hole injection layer is usually a transition metal oxide. The hole injection layer can be formed on the pixel electrode by sputtering, for example.

In addition, it is preferable to form a bank that defines the light emitting region so as to cover a part or all of the periphery of the pixel electrode. When a hole injection layer is formed on the pixel electrode, a bank may be formed so as to cover part or all of the periphery of the hole injection layer on the pixel electrode. As the bank material, a photosensitive resin material containing a resin such as polyimide or acrylic resin can be used. Note that a fluorine compound may be introduced into the resin. If the photosensitive resin composition is used, the bank can be patterned by a photolithography process (coating, baking, exposure, development, and baking). Although not particularly limited, for example, TMAH is baked at 100 ° C. for 2 minutes, exposure is i-line having a main peak at 365 nm of 200 mJ / cm ² , and development is 0.2% by mass. (Tetramethylammonium hydroxide) 60 seconds, rinse with pure water for 60 seconds, and firing may be performed at 220 ° C. for 60 minutes using a drying furnace.

  Note that after the bank is formed, an ink containing a hole transport material may be applied onto the hole injection layer. The hole transport layer can be formed by drying and baking the applied ink. The applied ink contains a desired hole transport material and an organic solvent. The organic solvent is determined according to the type of the hole transport material. Examples of the organic solvent include aromatic solvents such as anisole. The means for applying ink is not particularly limited. Examples of the ink application means include an inkjet method, a dispenser method, a nozzle coating method, a spin coating method, a die coating method, an intaglio printing method, and a relief printing method. A preferred ink application means is an ink jet method.

(Second step)
In the second step, ink containing a light emitting material is applied onto the pixel electrode. When a hole injection layer or a hole transport layer is formed on the pixel electrode, ink is applied onto the pixel electrode through these layers. When a bank is formed, ink is applied on the pixel electrode in the area defined by the bank.

  The ink contains a light emitting material and a volatile organic solvent. What is necessary is just to select an organic solvent according to the kind of luminescent material. Examples of the organic solvent include cyclohexylbenzene (CHB), anisole, methoxytoluene, heptylbenzene and the like. Examples of the ink application means include an inkjet method, a dispenser method, a nozzle coating method, a spin coating method, a die coating method, an intaglio printing method, and a relief printing method. A preferred ink application means is an ink jet method.

(Third step)
In the third step, an outer peripheral wall surrounding the outer periphery of the image display area is formed on the substrate. Here, the “image display area” means an area where a plurality of pixel electrodes are arranged on the substrate. The outer peripheral wall is preferably formed immediately after the ink containing the light emitting material is applied and before the ink is dried.

  As a material for the outer peripheral wall, a glass frit material (that is, a glass paste) is preferably used. The glass frit material usually contains a glass frit which is powdery glass and an organic solvent. The glass frit material has a higher viscosity than a general resin material. For this reason, if a glass frit material is used, it can have a certain height and can easily form a good outer peripheral wall made of shape retention. The organic solvent contained in the glass frit material is preferably the same type of organic solvent as the organic solvent contained in the ink for forming the light emitting layer. By using the same type of organic solvent as the organic solvent contained in the ink for forming the light emitting layer or the like, vapor of the organic solvent is also generated from the outer peripheral wall. For this reason, the decrease in the vapor concentration of the organic solvent in the vicinity of the outer peripheral wall (that is, the end of the image display region) can be more effectively suppressed, and the film thickness of the formed light emitting layer can be made more uniform. Can do.

  The outer peripheral wall is formed by applying a material for forming the outer peripheral wall such as a glass frit material. Examples of the application means include a dispenser method using a dispenser, a nozzle coating method, a die coating method, and the like. A preferable application means such as a glass frit material is a dispenser method.

The outer peripheral wall is a structure for accumulating the vapor of the organic solvent generated from the ink of the light emitting material. When the evaporation rate of the organic solvent is high, it is necessary to form a high outer peripheral wall in order to store the vapor of the organic solvent inside. That is, the required height of the outer peripheral wall is determined by the evaporation rate of the organic solvent contained in the ink. For example, when the organic solvent is cyclohexylbenzene (CHB) (evaporation rate at 25 ° C. and atmospheric pressure: 6.441 × 10 ⁻⁶ kg / (m ² · sec)), the height of the outer peripheral wall is 3 mm or more, preferably 3 to 5 mm. Further, when the organic solvent is methoxytoluene (evaporation rate at 25 ° C. and atmospheric pressure: 41.77 × 10 ⁻⁶ kg / (m ² · sec)), the height of the outer peripheral wall is 20 mm or more, Preferably, it is 20 to 24 mm. Furthermore, when the organic solvent is phenoxytoluene (evaporation rate at 25 ° C. and atmospheric pressure: 1.829 × 10 ⁻⁶ kg / (m ² · sec)), the height of the outer peripheral wall is 0.9 mm. As mentioned above, Preferably it is 1-3 mm.

  The evaporation rate of the organic solvent generated from the ink of the luminescent material was calculated from the weight loss by thermogravimetry (TG) / differential thermal analysis (DTA). The trade name “EXSTAR TG / DTA7000” (manufactured by SII Nanotechnology) was used for TG / DTA.

  In addition, about the implementation order of a 2nd step and a 3rd step, it does not specifically limit, Any step may be implemented first. However, it is preferable to perform the third step after the second step because the ink can be easily applied to a more accurate location without being restricted by the presence of the outer peripheral wall.

(4th step)
In the fourth step, the ink applied onto the pixel electrode is dried in a state where the periphery of the image display area is surrounded by an outer peripheral wall having a predetermined height. Thereby, a light emitting layer can be formed. The means for drying the ink is not particularly limited, but it is preferable to dry the ink by, for example, drying under reduced pressure. The vacuum drying may be performed, for example, by using a vacuum chamber and reducing the pressure in the chamber to an ultimate pressure of about 5 Pa with a vacuum pump or the like. The outer peripheral wall can be dried simultaneously with the drying of the ink. Usually, after the ink is dried, it is baked for about 10 minutes using an IR furnace or a hot plate. The baking temperature is appropriately set depending on the type of the light emitting material, and is, for example, around 130 ° C.

(5th step)
In the fifth step, counter electrodes are formed on all upper surfaces of the image display region including the upper surface of the light emitting layer. The counter electrode can be formed by, for example, a sputtering method. When the counter electrode is formed on all the upper surfaces of the image display area, the counter electrode is also formed on the inner wall surface of the outer peripheral wall at the same time.

(6th step)
In the sixth step, a sealing plate is disposed on the outer peripheral wall. At that time, the outer peripheral wall is crushed to form a wall-shaped sealing portion (dam (DAM)) arranged so as to surround the outer periphery of the image display region. An organic EL display panel can be obtained by pasting the substrate and the sealing plate through the formed wall-shaped sealing portion.

  Normally, the wall-shaped sealing portion is formed by firing the deformed outer peripheral wall. However, when the constituent material of the outer peripheral wall is a glass frit material, it is preferable to fire the glass frit by irradiating the deformed outer peripheral wall with a laser. Since the temperature required for firing the glass frit is usually as high as 400 to 800 ° C., the glass frit on the outer peripheral wall is fired while irradiating a laser having a narrow focal range while avoiding the influence on portions other than the outer peripheral wall. be able to.

2. Organic EL Display Panel The organic EL display panel of the present invention is manufactured by the above-described method for manufacturing the organic EL display panel of the present invention. The organic EL display panel of the present invention includes a substrate, a plurality of pixel electrodes arranged on the substrate, an organic functional layer including a light emitting layer, a counter electrode disposed on the organic functional layer, and an outer periphery of the image display region. The wall-shaped sealing part arrange | positioned on a board | substrate so that may be enclosed, and the sealing board arrange | positioned on a sealing part. Hereinafter, each component will be described.

(substrate)
The material of the substrate differs depending on whether the display panel is an organic EL or a bottom emission type or a top emission type. For example, in the case of the bottom emission type, the substrate is required to be transparent. Therefore, in the case of the bottom emission type, examples of the material of the substrate include glass, quartz, and transparent plastic. On the other hand, in the case of the top emission type, the substrate does not need to be transparent. Therefore, in the case of the top emission type, the material of the substrate is arbitrary as long as it is an insulator, and is, for example, opaque plastic or metal.

  When the organic EL display panel is an active matrix type, a thin film transistor (drive TFT) for driving the organic EL element is built in the substrate. The source electrode or drain electrode of the TFT built in the substrate is connected to the pixel electrode. Further, the pixel electrode may be arranged on the same plane as the source electrode or drain electrode of the TFT. Note that the organic EL display panel may be laminated on the TFT.

(Pixel electrode)
The pixel electrode is a conductive member disposed on the substrate. The pixel electrode normally functions as an anode, but may function as a cathode. When the organic EL display panel is a bottom emission type, the pixel electrode is required to be a transparent electrode, and may be formed of ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), tin oxide, or the like. When the organic EL display panel is a top emission type, the pixel electrode is required to have light reflectivity. The light-reflective pixel electrode includes, for example, an alloy containing silver, more specifically, a silver-palladium-copper alloy (also referred to as APC), a silver-rubididium-gold alloy (also referred to as ARA), a molybdenum-chromium alloy (MoCr). Or a nickel-chromium alloy (also referred to as NiCr), an aluminum alloy, or the like. The thickness of the pixel electrode is usually 100 to 500 nm, preferably about 150 nm.

(Hole injection layer and hole transport layer)
At least one of a hole injection layer and a hole transport layer may be disposed on the pixel electrode. The hole injection layer means a layer made of a hole injection material. Examples of the hole injection material include poly (3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (referred to as PEDOT-PSS) and derivatives thereof (copolymers and the like). In addition, the hole injection material may include oxides such as WOx (tungsten oxide), MoOx (molybdenum oxide), and VOx (vanadium oxide); combinations thereof; WOx doped with Mo and the like. The thickness of the hole injection layer is usually 10 nm or more and 100 nm or less, preferably about 30 nm.

  The hole transport layer is a layer having a role of blocking the transport of electrons to the hole injection layer, a role of efficiently transporting holes to the light emitting layer, and the like. The hole transport layer is a layer made of a copolymer of fluorene and an aromatic amine, for example. The thickness of the hole transport layer is usually from 10 nm to 100 nm, preferably about 30 nm.

(bank)
It is preferable that the bank defining the light emitting region is formed so as to cover part or all of the periphery of the pixel electrode. The bank is a structure made of a resin such as polyimide or acrylic resin. These resins are preferably fluororesins having fluorine atoms in at least some of the repeating units. Examples of the fluororesin include fluorinated polyolefin resin, fluorinated polyimide resin, fluorinated polyacrylic resin, and the like. Further specific examples of the fluororesin include a fluorine-containing polymer described in JP-T-2002-543469; a trade name “LUMIFLON” (registered trademark, Asahi Glass Co., Ltd.), which is a copolymer of fluoroethylene and vinyl ether. Manufactured) and the like. The height of the bank from the substrate is usually 0.1 μm to 2 μm, preferably 0.8 μm to 1.2 μm.

  The shape of the bank is preferably a forward tapered shape. The forward taper shape means a shape in which the barrier surface of the bank is inclined and the area of the bottom surface of the bank is larger than the area of the upper surface of the bank. When the bank shape is tapered, the taper angle is usually 20 ° to 80 °, preferably 30 ° to 50 °.

  The wettability of the bank upper surface is preferably low, and is preferably lower than the wettability of the bank wall surface. The top surface of the bank means a surface including the top of the bank. Specifically, the contact angle between the bank upper surface and water is usually 80 ° or more, preferably 90 ° or more. The contact angle between the bank upper surface and anisole is usually 30 ° to 70 °. On the other hand, the contact angle between the bank wall surface and anisole is usually 3 ° to 30 °. In addition, it means that the wettability of the surface is so low that the value of a contact angle is high.

(Organic functional layer)
An organic functional layer including at least one light emitting layer is disposed on the pixel electrode. In addition, when a hole injection layer and a hole transport layer are arrange | positioned on a pixel electrode, an organic functional layer is arrange | positioned on a pixel electrode through these layers. When the bank is provided, the organic functional layer is disposed in a region defined by the bank. Although the thickness of an organic functional layer is not specifically limited, What is necessary is just about 50-200 nm, for example.

  The organic EL material contained in the light emitting layer is appropriately selected for each sub-pixel according to the color (RGB) of light emitted from the sub-pixel (organic EL element). The organic EL material may be either a high molecular organic EL material or a low molecular organic EL material, but a high molecular organic EL material is preferable from the viewpoint of forming by a coating method. By using the polymer organic EL material, the light emitting layer can be easily formed without damaging other members.

  Examples of the polymer organic EL material include polyparaphenylene vinylene and derivatives thereof, polyacetylene and derivatives thereof, polyphenylene and derivatives thereof, polyparaphenylene ethylene and derivatives thereof, poly-3-hexylthiophene and derivatives thereof, polyfluorene and derivatives thereof Etc. are included.

  Examples of the low molecular organic EL material include a combination of a dopant material and a host material. Examples of dopant materials include BCzVBi (4,7-diphenyl-1,10-phenanthroline), coumarin, rubrene, DCJTB ([2-tert-butyl-6- [2- (2,3,6,7-tetrahydro). -1,1,7,7-tetramethyl-1H, 5H-benzo [ij] quinolizin-9-yl) vinyl] -4H-pyran-4-ylidene] malononitrile) and the like. Examples of the host material include DPVBi (4,4'-bis (2,2-diphenylethenyl) biphenyl), Alq3 (tris (8-quinolinolato) aluminum) and the like.

  In addition to the light emitting layer, the organic functional layer may include a hole transport layer (interlayer), an electron injection layer, an electron transport layer, and the like. The hole transport layer has a function of efficiently transporting holes to the organic light emitting layer and a function of blocking the entry of electrons into the pixel electrode (or hole injection layer). Therefore, the hole transport layer is disposed between the pixel electrode and the light emitting layer. The material of the hole transport layer may be a high molecular material or a low molecular material as long as it is an organic material having a hole transport property. Examples of the hole transporting organic material include a copolymer containing a fluorene moiety and a triarylamine moiety, and a low molecular weight triarylamine derivative.

(Counter electrode)
The counter electrode is a conductive member disposed on the organic functional layer. In addition, this counter electrode is also arrange | positioned also on the inner wall face of the sealing part mentioned later. The counter electrode normally functions as a cathode, but may function as an anode.

  The material of the counter electrode differs depending on whether the organic EL device is a bottom emission type or a top emission type. When the organic EL device is a top emission type, the counter electrode needs to be transparent. Therefore, the material of the counter electrode is preferably a conductive member having a transmittance of 80% or more. Thereby, a top emission organic EL display panel with high luminous efficiency, low power consumption, and long life can be obtained.

  Such a transparent electrode may be composed of a layer containing an alkaline earth metal, a layer made of an electron-transporting organic material, and a metal oxide layer. Examples of alkaline earth metals include magnesium, calcium, barium and the like. The electron transporting organic material is, for example, an electron transporting organic semiconductor material. The metal oxide is not particularly limited, but for example, indium tin oxide or indium zinc oxide.

  The transparent cathode may be composed of a layer containing an alkali metal, an alkaline earth metal, or a halide thereof and a layer containing silver. The layer containing silver may be comprised only from silver, and may be comprised from a silver alloy. Moreover, you may provide a refractive index adjustment layer with high transparency on the layer containing silver. The light extraction efficiency can be improved by providing the refractive index adjustment layer.

  The counter electrode may be formed on the surface of each light emitting layer, but is usually formed so as to cover a plurality of light emitting layers in common. The counter electrode is usually formed by a sputtering method and is not necessarily separated for each light emitting layer. That is, if the pixel electrode is controlled independently for each organic EL element as in the active matrix type, the TFT element that drives the organic EL element is independent, so that the counter electrode is shared by a plurality of light emitting layers. be able to.

(Sealing part)
The sealing portion (dam (DAM)) is a portion formed by deforming the above-described outer peripheral wall and firing it by laser irradiation or the like as necessary. This sealing portion is a wall-shaped component arranged so as to surround the outer periphery of the image display area. In addition, the board | substrate and the sealing plate mentioned later are bonded together through the sealing part.

  The outer peripheral wall, which is a precursor of the sealing portion, is formed of a material such as a glass frit material. For this reason, when the outer peripheral wall is formed of a glass frit material, the sealing portion formed by deforming and baking the outer peripheral wall is formed of a fired product of glass frit.

  A counter electrode is formed on the inner wall surface of the outer peripheral wall which is a precursor of the sealing portion. For this reason, the counter electrode is also formed on the inner wall surface of the sealing portion formed by deforming the outer peripheral wall.

(Sealing plate)
A sealing plate is disposed on the sealing portion. This sealing plate is bonded to the substrate via a sealing portion. As the sealing plate, a glass plate or a resin plate can be used. When the display panel is a bottom emission type with organic EL, the sealing plate may not be transparent.

(Flattening layer)
A flattening layer is usually formed between the image display area (organic EL element) and the sealing plate. This planarization layer is formed, for example, by filling a resin material between the image display region (organic EL element) and the sealing plate.

(Organic EL display panel)
When a voltage is applied between the pixel electrode and the counter electrode of the organic EL display panel having the above-described configuration, holes from the pixel electrode and electrons from the counter electrode are injected into the light emitting layer. The injected holes and electrons are combined inside the light emitting layer, and excitons are generated. The light emitting layer emits light by this exciton, and light is emitted. Hereinafter, embodiments of the organic EL display panel of the present invention will be described with reference to the drawings.

  1 and 2 are a top view and a cross-sectional view schematically showing an embodiment of the organic EL display panel of the present invention. In addition, in FIG. 1, description of the sealing plate is abbreviate | omitted for convenience. As shown in FIGS. 1 and 2, the organic EL display panel 10 of the present embodiment includes a substrate 100, a pixel electrode 210, a hole injection layer 510, red (R), green (G), and blue (B). The organic functional layer 650 including the three-color light emitting layer 600, the bank 400, the sealing portion 750 formed around the image display region 900, the counter electrode 220, and the sealing plate 700 are included.

  The material of the substrate 100 is, for example, glass. In addition, a metal wiring or a transistor circuit may be formed on the substrate 100. The pixel electrode 210 is a conductive layer disposed on the substrate 100. The pixel electrode 210 is made of, for example, a light reflective metal such as APC. Usually, a plurality of pixel electrodes 210 are arranged in a matrix on the substrate 100.

  The light emitting layer 600 is disposed on the hole injection layer 510. The thickness of the light emitting layer 600 is preferably 50 to 150 nm. The banks 400 are arranged in a pixel shape or a line shape on the substrate 100 and the hole injection layer 510 so as to define the region of the light emitting layer 600. The sealing portion 750 is disposed so as to surround the outer periphery of the image display area 900. The sealing part 750 is formed of, for example, a fired product of glass frit. Note that a void 800 is preferably formed inside the sealing portion 750. For example, the void 800 may be formed when the outer peripheral wall 300 (see FIG. 3F) that is a precursor of the sealing portion 750 is bent and crushed. By forming a gap inside the sealing part 750, the impact resistance of the sealing part 750 is improved.

  The counter electrode 220 is a light-transmitting conductive layer disposed (surface-formed) on the light emitting layer 600 and on the inner wall surface 770 of the sealing portion. The material of the counter electrode is, for example, ITO. A sealing plate 700 is disposed on the sealing portion 750. The sealing plate 700 is a member for protecting the pixel electrode 210, the hole injection layer 510, the light emitting layer 600, the counter electrode 220, and the like from moisture, heat, impact, and the like. Sealing with the sealing plate 700 is performed by applying a laser from the sealing plate 700 side to the outer peripheral wall in a state where the deformed outer peripheral wall (not shown), which is a precursor of the sealing portion 300, and the sealing plate 700 are in close contact. Irradiation can be performed by firing the outer peripheral wall. Note that the counter electrode 220 is disposed between the sealing portion 750 and the sealing plate 700.

Width _{W 1} of the sealing portion 750 is generally 0.5 to 2 mm, preferably 1-1.5 mm.

(Method for manufacturing organic EL display panel)
Next, the manufacturing method of the organic EL display panel of this embodiment will be described. 3A to 3G are cross-sectional views schematically showing an embodiment of a method for producing an organic EL display panel of the present invention. The manufacturing method of the organic EL display panel of the present embodiment includes (1) a first step (FIG. 3A) in which a plurality of pixel electrodes 210 are arranged on the substrate 100, and (2) an ink 550 containing a light emitting material. The second step (FIG. 3C) applied on the substrate 210 and (3) the outer peripheral wall 300 having a predetermined height surrounding the outer periphery of the image display area 900 are formed on the substrate 100, and then the ink 550 is dried to emit the light emitting layer 600. (4) the fourth step (FIG. 3F) for forming the counter electrode 220, and (5) the fifth step for disposing the sealing plate 700 on the outer peripheral wall 300. (FIG. 3G).

  (1) In the first step (FIG. 3A), a plurality of pixel electrodes 210 are arranged in a matrix on the substrate 100. Note that a hole injection layer 510 can be formed on the pixel electrode 210. As shown in FIG. 3B, it is also preferable to form the bank 400 so as to cover the periphery of the hole injection layer 510 on the pixel electrode 210 and to expose a part of the surface of the hole injection layer.

  (2) In the second step (FIG. 3C), an ink 550 containing a light-emitting material in a region defined by the bank 440 on the hole injection layer 510 is applied by, for example, an inkjet method.

(3) In the third step (FIGS. 3D and 3E), first, the outer peripheral wall 300 is formed on the substrate 100 so as to surround the outer periphery of the image display region 900. The height H of the outer peripheral wall 300 is 3 mm or more, preferably 3 to 5 mm (see FIG. 4). The width W ₂ of the outer peripheral wall 300 is preferably 200 to 700 μm, and more preferably 300 to 500 μm. When the width W of the outer peripheral wall is too narrow, it is difficult to form such a narrow outer peripheral wall. On the other hand, when the width of the outer peripheral wall 300 is too thick, the effective image display area may be narrowed.

  Further, the outer peripheral wall 300 is preferably formed on the substrate 100 with a separation of 100 μm or more from the edge of the image display region 900, and more preferably with a separation of 0.5 to 2 mm (see FIG. 4). If the distance L from the edge of the image display area 900 to the outer peripheral wall 300 is too short, the deformed outer peripheral wall 300 may flow into the image display area 900 when the outer peripheral wall 300 is deformed in a later step. On the other hand, if the distance L is too long, the effective image display area may be narrowed.

  As shown in FIG. 5, the outer peripheral wall 310 is preferably formed so that the upper portion thereof is inclined in the outer peripheral direction of the substrate 100. By inclining the upper part of the outer peripheral wall 310 in the outer peripheral direction of the substrate 100, it is possible to more effectively suppress the deformed outer peripheral wall 300 from flowing into the image display region 900 side. Moreover, as shown in FIG. 6, it is also preferable to form the outer peripheral wall 320 in a stepped shape with the outer side being higher than the inner side. By forming the outer peripheral wall 320 in a staircase shape having a stepped portion 370 as shown in FIG. 6, it is possible to more effectively suppress the deformed outer peripheral wall 300 from flowing into the image display region 900 side. .

  Next, the light emitting layer 600 can be formed by drying the ink 550 and the outer peripheral wall 300 on the hole injection layer 510.

  (4) In the fourth step (FIG. 3F), the counter electrode 220 is formed on the light emitting layer 600. The counter electrode 220 is also formed on the inner wall surface of the outer peripheral wall 300.

  (5) In the fifth step (FIG. 3G), the sealing plate 700 is disposed on the outer peripheral wall 300 while crushing the outer peripheral wall 300. Next, the sealing portion 750 is formed by irradiating the outer peripheral wall 300 that has been crushed and deformed with laser from the sealing plate 700 side and appropriately applying pressure. Thereby, the substrate 100 and the sealing plate 700 can be bonded together via the sealing portion 750. The organic EL display panel 10 can be manufactured by the above steps.

  Hereinafter, the present invention will be described more specifically based on experimental examples.

(Reference Example 1)
As shown in FIGS. 12A and 12B, an APC film having a thickness of 150 nm was formed as a pixel electrode 215 on a glass substrate 100 (Asahi Glass Co., Ltd., 370 mm × 470 mm × 0.7 mm) by a sputtering method. A WOx film having a thickness of 30 nm was formed as a hole injection layer 520 on the formed APC film (pixel electrode 215) by a sputtering method. On the formed WOx film (hole injection layer 520), an acrylic material (a negative photosensitive resin material manufactured by Asahi Glass Co., Ltd.) is applied as a bank material by a spin coating method to form a coating film. For 2 minutes. Exposure was performed by irradiating with ultraviolet light having a wavelength of 365 nm for 10 seconds at an exposure illuminance of 20 mW / cm ² through a photomask. After developing with 0.2% by mass of a TMAH (tetramethylammonium hydroxide) aqueous solution (trade name “NMD-3”, manufactured by Tokyo Ohka Kogyo Co., Ltd.), it was washed with pure water. Line-shaped banks 410 were formed on the WOx film by post-baking at 220 ° C. for 60 minutes in a clean oven. The opening width of the formed bank 410 was 65 μm, and the length (height) from the surface of the hole injection layer 520 to the upper end of the bank 410 was 1 μm.

  An ink containing a luminescent material and cyclohexylbenzene as a solvent was applied to the line-shaped region defined by the formed bank 410 by an inkjet method. Around the image display area, a glass frit and a glass frit material containing cyclohexylbenzene as a solvent were applied by a dispenser method to form an outer peripheral wall 330 having a height of 3 mm. The glass substrate 100 is placed in a vacuum chamber with an internal temperature of 25 ° C., and the vacuum chamber is depressurized with a vacuum pump at an exhaust speed of depressurizing from atmospheric pressure to 10 Pa in 30 seconds to dry the ink (and outer peripheral wall). 610 was formed. Table 1 shows the measurement results of film thickness uniformity of the formed light emitting layer 610 (dry film). Moreover, the measurement result of a film | membrane profile is shown in FIG. In addition, the measuring method of a film profile and film thickness uniformity is shown below.

[Measurement of Film Profile and Film Thickness Uniformity]: The film shape of the light emitting layer (dry film) located at the end of the image display area was measured with an atomic force microscope (trade name “AS-7B”, manufactured by Takano Co., Ltd.). ) To measure the film profile and film thickness uniformity. The film thickness uniformity was calculated by the following formula (2). The film profile and the film thickness uniformity were measured for an area (effective pixel area) 7.5 μm or more from the bank in the ink application area.
Film thickness uniformity (%) = {(maximum film thickness−minimum film thickness) / (2 × average film thickness)} × 100
... (2)

(Comparative Reference Example 1)
A light emitting layer was formed in the same manner as in Reference Zero Example 1 except that an outer peripheral wall having a height of 1 mm was formed. Table 1 shows the measurement results of the film thickness uniformity of the formed light emitting layer (dry film). Moreover, the measurement result of a film profile is shown in FIG.

(Comparative Reference Example 2)
A light emitting layer was formed by the same operation as in Reference Example 1 except that the outer peripheral wall was not formed. Table 1 shows the measurement results of the film thickness uniformity of the formed light emitting layer (dry film). Moreover, the measurement result of a film | membrane profile is shown in FIG.

  From the results shown in Table 1, it is clear that in Reference Example 1 in which the outer peripheral wall having a height of 3 mm was formed, the film thickness uniformity was significantly improved as compared with Comparative Reference Example 2 in which the outer peripheral wall was not formed. It is. In addition, the film thickness uniformity of Comparative Reference Example 1 in which the outer peripheral wall having a height of 1 mm was formed was equivalent to the film thickness uniformity of Comparative Reference Example 2 in which the outer peripheral wall was not formed. This agrees with the tendency of the vapor concentration obtained by fluid analysis (see FIG. 8), and it is clear that uniforming the vapor concentration without variation contributes to uniform film profile. It is.

  According to the present invention, it is possible to provide an organic EL display panel that suppresses occurrence of luminance unevenness and has high display quality.

DESCRIPTION OF SYMBOLS 10 Organic EL display panel 100 Substrate 210,215 Pixel electrode 220 Counter electrode 300,310,320,330 Outer peripheral wall 350 Inner peripheral surface of outer peripheral wall 370 Stepped part 400,410 Bank 510,520 Hole injection layer 550 Ink 600,610 Light emitting layer 650 Organic functional layer 700 Sealing plate 750 Sealing portion 770 Inner wall surface of sealing portion 800 Air gap 900 Image display region

Claims (10)

A substrate,
A plurality of pixel electrodes arranged on the substrate and constituting an image display region;
An organic functional layer disposed on the pixel electrode, including a light emitting layer made of a light emitting material formed by a coating method;
A counter electrode disposed on the organic functional layer and shared with the plurality of pixel electrodes;
A wall-shaped sealing portion disposed on the substrate so as to surround the outer periphery of the image display region;
A sealing plate disposed on the sealing portion,
An organic EL display panel in which the counter electrode is also disposed on an inner wall surface of the sealing portion.   The organic EL display panel according to claim 1, wherein the sealing portion is formed of a fired product of glass frit.   The organic EL display panel according to claim 1, wherein a gap is formed inside the sealing portion. Arranging a plurality of pixel electrodes constituting an image display area on a substrate;
Applying an ink containing a luminescent material and a volatile organic solvent on the pixel electrode;
Forming an outer peripheral wall having a height of 3 mm or more surrounding the outer periphery of the image display area on the substrate;
Drying the ink applied on the pixel electrode to form a light emitting layer;
Forming a counter electrode on the light emitting layer and on the inner wall surface of the outer peripheral wall;
Disposing a sealing plate on the outer peripheral wall and crushing the outer peripheral wall to form a wall-shaped sealing portion disposed so as to surround the outer periphery of the image display region;
The manufacturing method of the organic electroluminescent display panel which has this.   The method for producing an organic EL display panel according to claim 4, wherein the squeezed outer peripheral wall is baked by a laser to form the sealing portion.   The method for producing an organic EL display panel according to claim 4, wherein the outer peripheral wall is formed using a glass frit material.   The method for producing an organic EL display panel according to claim 6, wherein the glass frit material contains the same type of organic solvent as the organic solvent contained in the ink.   The method for manufacturing an organic EL display panel according to any one of claims 4 to 7, wherein the outer peripheral wall is formed on the substrate so as to be spaced from the edge of the image display region by 100 μm or more.   The method of manufacturing an organic EL display panel according to claim 4, wherein an upper portion of the outer peripheral wall is inclined in an outer peripheral direction of the substrate.   10. The method of manufacturing an organic EL display panel according to claim 4, wherein the outer peripheral wall has a stepped shape that is higher on the outer side than on the inner side.

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