JP4248184B2 - Self-luminous display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a self-luminous display device in which each display pixel includes a plurality of display elements.
[0002]
[Prior art]
The demand for flat display devices typified by liquid crystal display devices has rapidly increased, taking advantage of thin, lightweight, and low power consumption for CRT displays. In particular, an active matrix type flat display device in which a switch element is provided for each display pixel can provide a good display quality without crosstalk between adjacent display pixels, so that it can be used in various displays including portable information devices. It has come to be used.
[0003]
In recent years, organic electroluminescence (EL) display devices have been actively developed as self-luminous displays capable of high-speed response and wide viewing angle compared to liquid crystal display devices.
[0004]
As an example, an organic EL display device will be described. An array substrate having display elements arranged in a matrix on one main surface of the substrate, and a counter substrate arranged to face one main surface of the array substrate; It is configured with.
[0005]
Such a display element includes a light emitting layer between an anode and a cathode, and the display elements are partitioned by partition walls having a structure in which a hydrophilic film and a water repellent film are laminated. The light emitting layer is filled with a solution in which a light emitting material is dissolved (hereinafter referred to as a light emitting layer material) into a concave pixel light emitting region composed of partition walls around the anode by a method such as inkjet, and the solvent is removed by drying to form a thin film. Create by forming.
[0006]
[Problems to be solved by the invention]
However, the film thickness profile of the light emitting layer may be affected by the wettability with the surrounding partition walls and the film thickness profile of the film in which the surface tension / viscosity / solvent drying characteristics of the light emitting layer material itself are completed. Since the luminous efficiency of the organic EL element depends on the film thickness, a bright part and a dark part are formed in the pixel, and a desired design luminance cannot be obtained. Further, if the current density of the pixel is increased in order to obtain the design luminance, the lifetime of the pixel is shortened due to partial emission of high luminance. On the other hand, when trying to improve from the composition of the material, it is being considered to control the composition of the insulating material used for the drying process and partition walls, but it is possible to select a combination of materials, such as a combination of special materials and cost. There was a fault.
[0007]
The present invention has been made in view of the above problems, and an object thereof is to realize a self-luminous display device with better display quality. It is another object of the present invention to provide a self-luminous display device that improves the layout of display elements and does not reduce the light emitting area when a plurality of display elements are arranged in one display pixel. It is another object of the present invention to provide a self-luminous display device with higher luminance and longer life without complicating materials and processes. Another object of the present invention is to provide a self-luminous display device in which variation in the thickness of the light emitting layer is suppressed. It is another object of the present invention to provide a self-luminous display device with improved display element shape and reduced electric short-circuit and electric field concentration.
[0008]
[Means for Solving the Problems]
For example, when a display pixel is formed using an EL light emitting polymer, a polymer light emitting layer is formed by filling a solution obtained by dissolving in a normal solvent into a display pixel formed by an insulating film. As a result of observing the film thickness distribution of the light-emitting layer formed after drying in detail, it was confirmed that the film thickness was thicker at the periphery of the pixel and decreased toward the center of the pixel. This tendency was observed when the pixel area was small. It has been found that the film thickness deviation between the peripheral part and the central part can be reduced. However, if the pixel area is reduced, one pixel must be formed with a plurality of elements in order to obtain a desired light emission luminance, resulting in a reduction in aperture ratio. In order to reduce the film thickness deviation by keeping the distance from the peripheral part of the pixel to the center part of the film and to obtain a desired light emitting area, the inventors include a plurality of elements in one pixel. I found that I was able to achieve my goal.
[0009]
The inventors of the present claim 1 includes a plurality of anode films are arranged in a matrix, and a convex portion formed of an insulating material on the anodic film, the prior SL anode layer where the convex portions are formed a light emission layer formed by an inkjet method is disposed, a display pixel and a cathode layer disposed opposite said anode layer through the light-emitting layer, electrically insulated from between the anode layer adjacent It is characterized in that and a partition wall having an opening on the anode layer.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an organic EL display device will be described as an example of an embodiment of the present invention.
FIG. 1 is a schematic circuit diagram of an organic EL display device, and FIG. 2 is a partial schematic cross-sectional view thereof. The organic EL display device 1 includes an array substrate 100 in which display pixels 140 are arranged in a matrix on an insulating support substrate 101 such as glass, and a sealing substrate 200 arranged to face the array substrate 100.
[0012]
The array substrate 100 includes a plurality of signal lines 110, a plurality of scanning lines 120 disposed substantially orthogonal to the signal lines 110, and pixel switches 130 disposed near the intersections of the signal lines 110 and the scanning lines 120. And a display pixel 140 connected to each pixel switch 130. Each display pixel 140 includes a plurality of display elements PX _n, the drive control device 141 for driving the display element PX _n. For example, the pixel switch 130 includes an n-type thin film transistor, the drive control element 141 includes a p-type thin film transistor, and each display element PX _n includes an anode, a cathode, and a light emitting layer EM sandwiched between these electrodes. The source electrode of the pixel switch 130 is connected to the signal line 110, the gate electrode is connected to the scanning line 120, and the drain electrode is connected to the gate electrode G of the drive control element 141. Further, the source electrode S of the drive control element 141 is connected to the power supply line VDD, and the drain electrode D is connected to the anode film AD.
[0013]
In the case of performing color display, light corresponding to each display pixel 140 is emitted, and here, light corresponding to wavelengths of red, blue, and green is emitted. The light emission shape of each display pixel 140 substantially matches the shape of a pixel light emission region described later.
[0014]
Here, each display pixel 140 of the array substrate 100 will be described in more detail. 3A and 3B are a part of the display pixel 140 of FIG. 2, in which FIG. 3A is a schematic plan view, and FIG. 3B is a schematic cross-sectional view. Each anode is constituted by an anode film AD provided in an island shape for each display pixel 140, and each cathode is constituted by a cathode film CD continuously disposed in common with each display pixel 140. At least one of the anode film AD and the cathode film CD is formed of a light-transmitting conductive film. Here, for example, the anode film AD is a light-transmitting conductive film such as ITO (Indium Tin Oxide), and the cathode film CD is made of Ba. Is done. The film thickness of the light transmissive conductive film is usually preferably about 10 to 150 nm. Further, a protective layer 150 such as Al is laminated so as to cover the cathode film CD.
[0015]
The partition wall 160 partitioning the pixel light emitting region of each display pixel 140 is formed with a two-layer structure of, for example, a first partition wall 161 and a second partition wall 162 stacked on the first partition wall 161. For example, the second partition 162 is formed of a water-repellent film made of an organic insulating material. Emitter layer EM is arranged in the opening of the partition walls 160, constituting the plurality of display elements PX _n. The partition wall 160 needs to have a height that prevents the light emitting material from flowing out to other adjacent pixel light emitting regions when the light emitting layer material is filled. In addition, the opening of the first partition 161 is formed to have the same diameter as the opening of the second partition 162 or smaller than the opening of the second partition 162.
[0016]
And in the present invention comprises one or more convex portions 170 on the anode layer AD pixel emission area corresponding to the opening of the partition wall 160 is divided into each of a plurality of display elements PX _n. The convex portion 170 is a hydrophilic film made of, for example, an inorganic insulating material such as SiN or SiO. Of the anode film AD provided corresponding to each display pixel 140, a portion where the convex portion 170 is not disposed functions as an anode. To do. The height of the convex portion 170 is equal to or less than the height of the partition wall 160 separating each display pixel 140, and preferably has a height substantially equal to the film thickness of the light emitting layer EM, and is approximately 50 to 200 nm. The width of the convex portion 170 is desirably narrow so as not to reduce the light emitting area. The shape of the convex portion 170 is a circular shape, when each display pixel 140 includes three or more display elements PX _n, a plurality of annular-shaped having different sizes according to the display device PX _n number It has a convex part. These convex portions are arranged so as to include other convex portions having a smaller area (the size of the outer shape) on the outer periphery thereof, and each convex portion does not branch or cross each other. Moreover, you may provide the convex part of a predetermined shape inside the smallest cyclic | annular convex part.
[0017]
Each display element PX _n separated in such a convex portion 170, the in comprising the area (the size of the outer shape) periphery is formed differently each is smaller than the display element PX _n all areas made in the outer peripheral It is formed so as to contain. That is, each display pixel 140 includes a ring-shaped display element PX _n having a different size, or a display element PX _n having a predetermined shape inside the smallest annular convex portion 170, and a display element PX having a large outer shape. _It arrange | positions so that _n may include the display element PXn with a smaller external dimension.
[0018]
Thus, by making the shape of the plurality of display elements PX _n included in the display pixel 140 with the ring shape, without forming a display element PX _n having a sharp edge, forming the emitter layer EM in the edge portion Film defects can be reduced. And generation | occurrence | production of the unfilled part of the light emitting layer EM can be suppressed, and generation | occurrence | production of the electrical short between an anode and a cathode can be reduced. Further, by disposing one or more convex portions 170 in the pixel light emitting region, it is possible to dispose the light emitting layer EM in which the variation in film thickness is suppressed, reducing electric field concentration and improving display quality. can do. An organic EL display device with high luminance and long life can be realized.
[0019]
Further, by disposing the display element having a large outer shape so as to include the display element having a small outer shape, the display element can be laid out without substantially reducing a region contributing to light emission.
[0020]
As an example, FIG. 3 illustrates a case where a circular pixel light emitting region is provided. In this example, in the case where each display pixel 140 has two display elements PX _1, PX _2, the width d ₁ of the first display element PX ₁ ring has a periphery defining a size of the pixel light-emitting region And a circular second display element PX ₂ having a diameter d ₂ . These display elements PX ₁ and PX ₂ are divided by an annular convex portion 170 having a width D ₁ .
[0021]
The second size of the display element PX ₂ of diameter _{d 2} which is enclosed width _{d 1} of the first display element PX ₁ in the first display element PX ₁ are identical. In this way, by keeping the distance between the light emitting layer EM of each display element PX ₁ and PX ₂ and the end of the convex portion 170 or the partition wall 160 uniform, the wettability with the end portion and the distance from the end portion are reduced. The influence on the film thickness of the light emitting layer EM can be made uniform.
[0022]
Further, each display element is symmetrically arranged in the display pixel 140 by arranging the display elements having similar shapes and disposing the display elements having a small outer shape so that the display elements having a large outer shape of the display element are included. The film thickness variation due to electric field concentration and shape can be suppressed.
[0023]
In the above-described embodiment, the case where each display pixel 140 includes two display elements has been described. However, as illustrated in FIG. 4, a plurality of display elements PX ₁ to ₃ may be included. Also in this case, it is desirable that the light emission width d ₁ of the outermost display element PX ₁ and the innermost display element PX ₂ diameter d ₂ are equal, and further, the width d of the annular display element PX ₃ disposed therebetween. _It is desirable that the size of ₃ is also equal (d ₁ = d ₂ = d ₃ ). Further, it is desirable that the annular display elements PX ₁ and PX ₃ except the innermost display element PX ₂ are similar in shape.
[0024]
Further, as shown in FIG. 5, a plurality of annular convex portions 171, 172 and a convex portion 172 having the smallest outer diameter have a circular convex portion 173, and all of the display elements PX _{1 to 3} are displayed. May be annular. Also in this case, it is desirable that the widths of the annular display elements PX ₁ to 3 are equal (d ₁ = d ₂ = d ₄ ), and it is desirable that they are similar in shape.
[0025]
Further, the pixel light emission shape is not limited to a circle, and may be a regular polygon shape as shown in FIG. When the light emitting layer EM is applied using an inkjet nozzle, it is desirable to form the pixel light emission shape so that the aspect ratio is 1: 1.
[0026]
Further, by forming each display element in a regular polygon shape and having an internal angle θ formed by each side having an angle of 90 ° or more, electric field concentration due to an acute edge can be reduced. Further, in the case of having an acute angle edge, it is possible to suppress a manufacturing defect such that the light emitting layer material does not spread over the edge portion and becomes unfilled. And generation | occurrence | production of the electrical short circuit resulting from an unfilled part can be prevented.
[0027]
Next, an example of a method for manufacturing the organic EL display device 1 will be described.
On the substrate on which the signal lines 110, the scanning lines 120, the pixel switches 130, the drive control elements 141, etc. are arranged in a matrix array, for example, ITO is deposited as an anode film AD material to a film thickness of 50 nm by vapor deposition, sputtering, etc. An anode film AD corresponding to the display pixel 140 is formed by patterning using a photolithography method.
[0028]
On the anode film AD, for example, a SiN film is formed as a first partition material to a thickness of 100 nm, and continuously, for example, a polyimide is formed as a second partition material so as to have a thickness of 3000 nm on the first partition film. To do. The film thickness of the first partition 161 is preferably set to be substantially the same as the film thickness of the light emitting layer EM, and the film thickness of the second partition 162 is determined by the light emitting layer material of each display pixel 140 when the light emitting layer material is applied. It is desirable to set the level so as not to be applied to the adjacent display pixels 140.
[0029]
The second partition material is made of an organic insulating film, and any organic insulating film may be used as long as it achieves its purpose. However, a photosensitive material is desirable from the viewpoint of simplicity of the process. For example, as an organic insulating film that gives a positive pattern, a photosensitive compound such as naphthoquinonediazide is added to an alkali-soluble polymer derivative such as phenol resin, polyacrylic resin, polyamide resin, or polyamic acid, and then exposed and exposed to alkali development. The material which can obtain a pattern is mentioned. Examples of the organic insulating film that gives a negative pattern include a photosensitive composition whose dissolution rate in a developer is slowed by irradiation with actinic radiation, for example, a photosensitive composition having a functional group that is cross-linked by irradiation with actinic radiation. For example, a photosensitive composition containing a compound having an epoxy group that crosslinks upon irradiation with actinic radiation can be used.
[0030]
Next, the second partition wall film is patterned to form a grid-like second partition wall 162 having an opening at a position corresponding to the pixel light emitting region. In the present embodiment, the opening has a circular shape, but is not limited thereto.
[0031]
Subsequently, the first partition wall layer is patterned into a predetermined shape, the first partition wall 161 having an opening that defines the pixel light-emitting region, at the same time to form the convex portion 170 to partition the display elements PX _n. For example, in this embodiment arranged a diameter within the display pixel 140 (inside) _{d 2,} the annular convex portion 170 of the width _{D 1} of the first partition wall 161 ends at a position equidistant _{d 1.} The convex portion 170 formed in this way is almost the same as the outer peripheral shape of the light emission shape of the pixel light emission region. Here, d ₂ = d ₁ and, for example, D ₁ is set to 0.1 μm. Thus, since the convex part 170 is simultaneously formed with the same material as the 1st partition 161, the convex part 170 can be formed, without increasing a material and a process and without increasing cost.
[0032]
Next, the light emitting layer EM is formed on the anode. Here, it is formed with an organic laminated structure including an anode buffer layer and an organic light emitting layer EM. As the anode buffer layer material, a polythiophene derivative, a polyaniline derivative (for example, a mixture of polyethylenedioxythiophene and polystyrene sulfonic acid, or a mixture of polyaniline and polystyrene sulfonic acid) and the like can be used. The thickness of the anode buffer layer is usually about 1 to 100 nm. The anode buffer layer is formed by a spin coating method or an ink jet method.
[0033]
As the organic light emitting layer material, those usually used for organic EL elements can be used. As such, for example, red includes a polymer compound having an alkyl or alkoxy substituent on the benzene ring of the polyvinylene styrene derivative, and a polymer compound having a cyano group on the vinylene group of the polyvinylene styrene derivative. Examples of green include a polyvinylene styrene derivative in which an alkyl, alkoxy, or aryl derivative substituent is introduced into a benzene ring. Examples of blue include polyfluorene derivatives such as a copolymer of dialkylfluorene and anthracene. In addition, a light emitting material having a low molecular weight may be added to these high molecular compounds. The film thickness of the organic light emitting layer has an optimum film thickness depending on the material, but is usually about 50 to 200 nm.
[0034]
For the light emitting layer, a solution containing each component is formed by an inkjet method.
First, an anode buffer layer material is formed by spin coating on each pixel light-emitting region divided by the partition 160 composed of the first partition 161 and the second partition 162, and heated at 120 ° C. for 3 minutes to obtain a thickness. A 30 nm anode buffer layer was formed.
[0035]
Thereafter, a predetermined amount of an organic light emitting layer material of each color is dropped by an inkjet method on the anode buffer layer of the pixel light emitting region corresponding to each color, and dried at 90 ° C. for 1 hour, and an organic light emitting layer EM having a thickness of 80 nm. Formed. For example, for red and blue pixels, a PPV derivative was synthesized with reference to the literature (Adv. Mater. 1998, 10, 1340) and dissolved in tetralin at 1%, and for blue pixels, the literature (Adv. 1998, 10, 993), a derivative of dihexylfluorene and anthracene was synthesized and similarly dissolved in tetralin to obtain an organic light emitting layer material.
[0036]
At this time, by arranging the convex portion 170 in the pixel light emitting region, the light emitting region can be divided, and the film thickness variation of the light emitting layer EM after drying can be effectively suppressed.
[0037]
Subsequently, Ba was vapor-deposited as a cathode material at a film thickness of 90 mm at a vacuum degree of 10-7 Pa to form a cathode film CD. Subsequently, Al was deposited to a thickness of 1500 mm to form a protective layer 150.
[0038]
In addition, a sealing material made of an ultraviolet curable resin is applied to the peripheral portion of the main surface of the sealing substrate 200 and is bonded to the main surface of the array substrate 100 in an inert gas atmosphere such as N ₂ or Ar. Then, ultraviolet cured by irradiating the sealing material, and creates an organic EL display device 1 organic EL display element PX _n is sealed between the support substrate 101 and the sealing substrate 200.
[0039]
The color display type active matrix organic EL display device formed in this way showed high emission luminance.
[0040]
In the above-described embodiment, the case where the anode and the source / drain electrode of the TFT are on the same plane has been described. However, an insulating film is disposed on the source / drain electrode, and the anode is disposed on the insulating film. Alternatively, the anode and the drain electrode D of the drive control element 141 may be electrically connected through a contact hole formed in the insulating film.
[0041]
In the above-described embodiment, the bottom emission type in which light is extracted from the array substrate 100 side and used as a display surface has been described. However, the present invention is not limited to this, and the cathode is formed of a light-transmitting conductive film to extract light from the counter substrate side. It may be a top emission type. For example, Pt is formed as the anode, and Mg: Ag is deposited as the cathode at a deposition rate ratio of 9: 1, and ITO is disposed thereon. At this time, Mg: Ag can be formed into a thin film to the extent that it has optical transparency.
[0042]
As the substrate used for the array substrate 100, any substrate can be used as long as it can hold the light emitting layer structure. A glass substrate is generally used, but may be flexible such as a plastic sheet according to the purpose of the device.
[0043]
In addition, the light emitting layer EM has been described as having a two-layer structure of an anode buffer layer and an organic light emitting layer, but a three-layer structure having a cathode buffer layer between the cathode and the organic light emitting layer, or a functional composite. You may comprise with a single layer structure.
[0044]
Further, the present invention is not limited to the organic EL display device, and can be applied to a self-luminous display device in general.
[0045]
【The invention's effect】
As described above in detail, according to the present invention, variation in the film thickness of the light emitting layer is suppressed, and a self-luminous display device having high display performance can be achieved. Further, by improving the layout of the display element, it is possible to realize a self-luminous display device with reduced electrical shorts and electric field concentration without reducing the light emitting area.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an organic EL display device according to an embodiment of the present invention.
FIG. 2 is a partial schematic cross-sectional view of an organic EL display device according to an embodiment of the present invention.
3A is a partial plan view of a display pixel according to an embodiment of the present invention, and FIG. 3B is a partial cross-sectional view thereof.
4A is a partial plan view of a display pixel according to another embodiment of the present invention, and FIG. 4B is a partial cross-sectional view thereof.
5A is a partial plan view of a display pixel according to another embodiment of the present invention, and FIG. 5B is a partial cross-sectional view thereof.
6A is a partial plan view of a display pixel according to another embodiment of the present invention, and FIG. 6B is a partial cross-sectional view thereof.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Organic EL display device 100 ... Array substrate 110 ... Signal line 120 ... Scan line 130 ... Pixel switch 140 ... Display pixel 141 ... Drive control element 150 ... Protection Layer 160 ... partition 161 ... first partition 162 ... second partition 170 ... convex portion 200 ... sealing substrate AD ... anode film CD ... cathode film EM ... Light emitting layer PX _n ... display element

Claims (7)

A plurality of anode films arranged in a matrix ;
A convex portion made of an insulating material on the anode film;
A light emission layer formed by an inkjet method is disposed on the front Symbol anode layer in which the convex portions are formed,
A display pixel and a cathode layer disposed opposite said anode layer through the front Symbol luminescent layer,
Electrically insulates between adjacent contact the anode layer, a self-luminous display device characterized by comprising a partition wall, a having an opening on the anode membrane.   The self-luminous display device according to claim 1, wherein the partition wall has a height higher than that of the convex portion.   The self-luminous display device according to claim 1, wherein the convex portion is made of an inorganic insulating material.   The self-luminous display device according to claim 1, wherein the convex portion has an annular shape that is equidistant from the end of the opening of the partition wall.   The self-luminous display device includes a plurality of annular convex portions having different outer sizes, and the convex portion having a larger outer shape includes a convex portion having a smaller size. The self-luminous display device described. The display element is self-luminous display apparatus according to claim 4, wherein you being a circular or regular polygonal shape. 4. Symbol placement of self-luminous display device characterized by the this annular width equal each of the display elements.

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