JP4882873B2 - Organic EL device and organic EL display panel - Google Patents

Description

  The present invention relates to an organic EL device and an organic EL display panel.

  An organic EL device which is a constituent element of an organic EL (Electroluminescence) display generally has an “organic EL light emitting device” and a “transistor” (TFT / Thin Film Transistor) for driving the organic EL device. A general transistor has a “driving transistor” for driving the light emitting element and a “switching transistor” for turning on / off the driving transistor.

  As an example of a typical structure of an organic EL device, a driving transistor and an organic EL light emitting device are arranged on the same plane (for example, a substrate surface), and the source electrode or drain electrode of the driving transistor and the organic EL light emitting device are arranged. Some pixel electrodes are connected on the same plane (see Patent Document 1). The content described in the cited document 1 is to manufacture a device (for example, a liquid crystal display device) including a thin film element such as a thin film transistor while forming a wall (bank) by the polyimide film 20 using an inkjet method. It is to do. Specifically, a wall made of a polyimide film 20 on the outer periphery of a region to which a liquid material is applied (part of elements of a liquid crystal display device: a color filter 23, a pixel electrode 24, a source / drain region 22, and a data line 26 region). A method is described in which a device is formed by applying a liquid material therein, followed by drying.

By this method, the vacuum process can be reduced, and at the same time, the liquid material to be used can be minimized by surrounding the area to be coated with a polyimide film (partition wall). As a result, the manufacturing cost is reduced. Is done. In addition, the expression “bank” (partition) as used in the cited document 1 means a physical boundary surrounded by a polymer. For example, in a plasma display panel, “rib” has the same meaning. "Is sometimes expressed.
JP 2003-318131 A (refer to paragraphs [0044], [0051], [0056], [0075], FIG. 3, and FIG. 6 (b) in particular)

  As disclosed in the cited document 1, when producing an organic TFT device of a so-called bottom gate type organic EL device, a bank insulating layer (gate insulating film) is formed on the bank layer (wall by the polyimide film 20). It is general that the channel region and the source / drain region are formed afterwards on the gate insulating layer (the cited document 1 shows an example in which the channel region and the source / drain region are formed in this order). However, depending on the configuration of the organic TFT device, the source / drain region and the channel region may be formed in this order.)

At this time, in order to apply the organic TFT material by a printing method such as an ink jet method in a space surrounded by the bank layer (hereinafter referred to as “cell”), the bottom surface of the cell is provided with hydrophilicity and The side surface (that is, the cell inner surface of the bank layer) needs to have water repellency. Therefore, in the process of manufacturing the organic TFT device using the printing method, after forming the bank layer on the gate insulating layer as described above, the inside of the cell is hydrophilized with oxygen plasma, and further CF ₄ (tetra (Fluoromethane) It is provided with a step of performing water repellent treatment on the cell inner surface of the bank layer by performing plasma treatment.

However, as described in the cited document 1, since the prior art is a material of a different system for the bank layer and the gate insulating film (in the case of the cited document 1, paragraphs [0044] and [0054] of the same document. ], The bank layer is made of polyimide, and the gate insulating film is made of silicon nitride (SiNx. Generally, it is made of silicon oxide (SiO ₂ ). For example, when the cell interior is made hydrophilic by oxygen plasma. The surface of the gate insulating film, which is the bottom surface of the cell, is etched, and the residue adheres to the bank layer.

In such a state, when the residue on the inner surface of the bank layer is removed with oxygen plasma and water repellent treatment is performed with CF ₄ plasma, the material constituting the gate insulating film attached to the bank layer (reference document) 1 is silicon nitride (SiNx, generally silicon oxide (SiO ₂ )), the degree of water repellency of the bank layer becomes non-uniform depending on the amount and distribution of the deposited organic EL. There is a problem that the characteristics as a device will be affected. From another point of view, for example, when the inside of a cell is made hydrophilic by oxygen plasma, the bank layer may be etched by oxygen plasma, and the residue obtained by etching the bank layer is deposited on the bottom surface of the cell (the surface of the gate insulating film). However, the characteristics as an organic EL device are affected.

  The present invention solves the above-described problems of the prior art, and in particular, an organic EL having a high electric mobility characteristic by using the same system material for the bank layer and the gate insulating layer provided outside the organic TFT layer. An object is to provide a device and an organic EL display.

In order to achieve the above object, a first organic EL device of the present invention includes an organic EL light emitting device including a pixel electrode, a gate electrode formed on a substrate, and the substrate provided on the gate electrode and the gate electrode. An organic TFT having a gate insulating layer covering the surface, a source electrode and a drain electrode formed on the gate insulating layer with a gap, and an organic TFT layer provided in the gap and connecting the electrodes In the EL device, a bank layer is provided outside the organic TFT layer, and an overcoat layer is provided on a surface including the bank layer and the organic TFT layer, and the overcoat layer, the bank layer, and the gate are provided. The insulating layers are all made of the same polyimide material.

Also, is further formed a planarization layer on the surface of the overcoat layer, the a planarization layer, and the overcoat layer, and the bank layer and the gate insulating layer may consist of the same material polyimide.

Furthermore, the organic EL display of the present invention is characterized in that an organic EL display is formed by combining a plurality of the organic EL devices according to claim 1 or 2 .

  As described above, according to the present invention, in a technique for manufacturing an organic EL device and an organic EL display using a printing method such as an inkjet method, a bank layer and a gate insulating layer provided outside the organic TFT layer are provided. An organic EL display using an organic EL device that can stabilize the functional characteristics of the organic TFT device by using the same system material, and has less unevenness in luminance and emission color in the pixel region. Can be provided.

  An organic EL device and an organic EL display according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

  1A is a schematic diagram (top view) showing the structure of an organic EL display according to an embodiment of the present invention, and FIG. 1B is an organic EL display according to an embodiment of the present invention. FIG. 1C is a schematic view showing a cross section (No. 1) of an organic TFT device constituting the organic EL display according to the embodiment of the present invention. The schematic which shows is shown.

<< Configuration of Transistor Device >>
In FIG. 1B, the transistor device 10 is a bottom-gate transistor having a gate electrode in the lower layer. The transistor device 10 includes a gate electrode 2 provided on the substrate 1, a gate insulating layer 3 provided so as to cover the gate electrode 2, a source electrode 4 provided on the gate insulating layer 3, On the gate insulating layer 3, on the gap G between the source electrode 4 and the drain electrode 5, the drain electrode 5 arranged on the same plane as the source electrode 4 with a gap G, and on the gate electrode 4. And an organic TFT layer 7 electrically connected across the drain electrode 5.

  At this time, a bank layer 6 a is provided on the surface of the gate insulating layer 3 and outside the source electrode 4 and the drain electrode 5, and between the source electrode 4 and the drain electrode 5 by a printing method such as an inkjet method. When the organic TFT material is applied to the gap G (channel region), the organic TFT material serves to prevent leakage of the organic TFT material into other channel regions. An overcoat layer 8 is formed on the surface including the bank layer 6 a and the organic TFT layer 7, and a planarizing film layer 9 is formed on the surface of the overcoat layer 8.

  Below, the structural member of this transistor device 10 is demonstrated.

<Board>
As the substrate 1, a glass substrate, a plastic substrate, or the like can be used. Further, a flexible substrate may be used. When this transistor element is used for an organic EL display, a flexible substrate is preferable. Specific examples of the material include a PET film (PET) and a PEN film (PEN: Polyethylene Naphthalate).

<Gate electrode>
The gate electrode 2 is provided on the substrate 1. As shown in FIG. 1B, the transistor device 10 according to the present embodiment is called “bottom gate type” because the gate electrode 2 is provided in the lowermost layer. The material of the gate electrode 2 is not particularly limited. For example, the gate electrode 2 includes a laminated film of a Cr film (5 nm or less) and an Au film (about 100 nm) or a laminated film of a Ti film (5 nm or less) and an Au film (about 100 nm). Is done. Although the Cr film and the Ti film mainly act as an adhesive film, it may be more preferable to use a Ti film that hardly oxidizes.

<Gate insulation layer>
The gate insulating layer 3 is provided between the gate electrode 2 and the plane on which the source electrode 4 and the drain electrode 5 are disposed. The gate insulating layer 3 can be composed of a commonly used insulating layer, such as a polymer insulating layer (specifically, any one of polyimide, acrylic, cycloten, and polystyrene).

<Source electrode and drain electrode>
The source electrode 4 and the drain electrode 5 are disposed on the upper surface of the gate insulating layer 3 formed on the substrate 1 and are separated from each other by a gap G. As the source electrode 4 and the drain electrode 5, a conductive metal such as aluminum, chromium, molybdenum chromium, titanium, gold, silver, or copper, or an organic conductor such as a polythiophene derivative can be used. In particular, it is preferable to use silver having a characteristic of high light reflectance.

<Organic TFT layer>
The organic TFT layer 7 is formed between the source electrode 4 and the drain electrode 5, and electrically connects the source electrode 4 and the drain electrode 5. The organic TFT layer 7 is made of a polycrystalline material, is formed on the gap G between the source electrode 4 and the drain electrode 5, and has excellent electrical characteristics from the source electrode 4 to the drain electrode 5.

  As the organic TFT material constituting the organic TFT layer 7, fluorene-thiophene copolymer (F8T2), tetrabenzoporphyrin, oligothiophene, pentacene, rubrene, etc. may be used. it can. In particular, tetrabenzoporphyrin may be used particularly in the case of a bottom gate electrode (a gate electrode disposed on the lower side of the channel when the substrate on which the channel is formed is on the lower side).

  The organic TFT layer 7 can be formed by applying a non-aqueous solution containing an organic semiconductor material to a non-aqueous solvent such as ethyl benzoate and then drying it. In this case, by drying the organic semiconductor solution of the convex droplets, the outer solvent dries faster, and the organic semiconductor material easily flows from the center toward the outer side.

<Bank layer>
As shown in FIG. 1B, the bank layer 6a is formed on the surface of the gate insulating layer 3 and outside the source electrode 4 and the drain electrode 5, and the source electrode 4 and the drain electrode 5 are formed by a printing method such as an inkjet method. When the organic TFT material is applied to the gap G (channel region) between the two, it serves to prevent the organic TFT material from leaking to other channel regions. As a specific material, any one of polyimide, acrylic, cycloten, and polystyrene is preferable. In addition, as shown in FIG.1 (c), the bank layer 6b may be formed in each surface of the source electrode 4 and the drain electrode 5, and a channel region may be formed.

  In the present embodiment, the formation of the bank layer in the case of the bottom gate type transistor device is described. However, when considering application to the top gate type transistor device, after forming the source electrode / drain electrode, After the bank layer is formed and the organic TFT layer is formed, the gate insulating layer is formed. If the bank layer and the gate insulating layer are made of the same material, the electric transfer is the same as in the case of the bottom gate type transistor device. It becomes possible to provide an organic EL device and an organic EL display having a high degree of temperature characteristics.

<Overcoat layer>
The overcoat layer 8 mainly serves to promote the electron transfer of the organic TFT layer 7 and to protect the organic TFT layer 7 from oxygen and water vapor in the air.

<Planarization film layer>
The planarizing film layer 9 is formed so as to cover the overcoat layer 8 described above, and an anode electrode of an organic EL material is formed on the planarizing film layer 9, so that the surface constituting the anode electrode is flat. Yes. Since the surface of the planarizing film layer 9 constituting the anode electrode is flat, it is possible to make the direction of light extraction when the light is reflected constant.

<< Configuration of organic EL light emitting device >>
The organic EL light emitting device includes a pixel electrode (not shown), an upper electrode (not shown), and an organic EL light emitting layer sandwiched between both electrodes, and may further have an arbitrary member. Between the two electrodes, a hole transport layer, an electron transport layer, or the like may be formed in addition to the organic EL light emitting layer. The materials such as the hole transport layer and the electron transport layer may be appropriately selected, and the thickness of each layer may be appropriately set to about several tens of nm.

<< Method of Manufacturing Transistor Element >>
Next, a manufacturing method of the bottom gate type transistor device 10 according to the present embodiment will be described with reference to FIG.
(Process 1)
A glass substrate, a plastic substrate, or a flexible substrate is prepared as the substrate 1.
(Process 2)
A gate electrode 2 is formed on the substrate 1 using a Cr or Au material (FIG. 2A).
(Process 3)
A gate insulating layer 3 is formed to cover the gate electrode 2 (FIG. 2B). As the gate insulating layer 3, for example, an insulating polymer such as polyimide, acrylic, cycloten, or polystyrene is used.
(Process 4)
Next, the source electrode 4 is provided on the gate insulating layer 3, and the drain electrode 5 is arranged on the same plane as the source electrode 4 with the gap G spaced apart (FIG. 2C). The source electrode 4 and the drain electrode 5 may be formed using a Cr or Au material.
(Process 5)
Then, using the gravure printing method as shown in FIG. 3, a bank layer 6a is formed on the surface of the gate insulating layer 3 and outside the source electrode 4 and the drain electrode 5 (FIG. 2D). As a material of the bank layer 6a at this time, an insulating polymer such as polyimide, acrylic, cycloten, or polystyrene may be used as in the gate insulating layer 3 described above. In addition, as shown in FIG.1 (c), the structure which provides the bank layer 6b on each surface of the source electrode 4 and the drain electrode 5 may be sufficient.

[Gravure printing method]
FIG. 3 shows a gravure printing apparatus 30. The gravure printing apparatus 30 is disposed so as to face the printing roll 31 and a printing roll (plate) 31 that has a peripheral side surface as a roll surface 31 a and can rotate around a rotation axis. The pressure drum roll 32 that rotates around the rotation axis, the supply roll 33 that rotates around the rotation axis and supplies ink to the printing roll 31, and the ink supplied to the supply roll 33 are controlled to a certain amount. The doctor 34 is configured. In the gravure printing apparatus 3 of the present embodiment, the (film) substrate 1 passes between the printing roll 31 and the impression cylinder roll 32 and proceeds in one direction.

Hereinafter, a method for forming a bank layer by a gravure printing method will be specifically described. First, the printing roll 31, the impression cylinder roll 32, and the supply roll 33 arranged in a tank (not shown) in which a resin material (a constituent material of the bank layer) is stored are rotated, respectively. A resin material is supplied onto the roll surface 31a. At this time, it is desirable that the resin material be supplied at a constant amount by the doctor 34. Then, the recess on the roll surface 1a is filled with a resin material, and the resin material is transferred to the surface of the substrate 1 and patterned into a desired shape.
(Step 6)
The transistor device manufactured up to FIG. 1D is exposed to oxygen plasma to expose the bottom surface of the space (cell) surrounded by the bank layers 6a and 6b (the gate insulation surrounded by the source electrode 4 and the drain electrode 5). After making the surface of the layer 3 hydrophilic, the cell side surface of the wall surfaces of the bank layers 6a and 6b is made hydrophilic by CF ₄ plasma (not shown).
(Step 7)
A convex droplet organic TFT solution containing an organic TFT material is applied to a non-aqueous solvent so as to cover the gap G (channel region) between the source electrode 4 and the drain electrode 5 (FIG. 2E). In addition, application | coating can be performed using the dispenser method, the inkjet method, etc., for example. Moreover, there is no problem even if it uses a roll printing method.
(Process 8)
The organic TFT solution is dried, and the organic TFT material is crystallized on the gap G between the source electrode 4 and the drain electrode 5 to obtain the organic TFT layer 7 (FIG. 2E). The organic TFT layer 7 makes it possible to electrically connect the source electrode 4 and the drain electrode 5.
(Step 9)
After the overcoat layer 8 is formed on the surface including the bank layer 6 a and the organic TFT layer 7, the planarizing film layer 9 is formed on the surface of the overcoat layer 8.

  At this time, the overcoat layer 8, the bank layers 6a and 6b, and the gate insulating layer 3 are made of the same material (that is, the overcoat layer 8 is also an insulating polymer such as polyimide, acrylic, cycloten, or polystyrene). ). Further, the planarizing film layer 9, the overcoat layer 8, the bank layers 6a and 6b, and the gate insulating layer 3 are made of the same system material (that is, the planarizing film layer 9 is also made of polyimide, acrylic, cycloten, polystyrene). It may be made of an insulating polymer). Of the gate insulating layer 3, the bank layers 6 a and 6 b, the overcoat layer 8 and the planarizing film layer 9, any two adjacent layers are preferably made of the same material.

  As described above, the bottom-gate transistor element according to this embodiment can be manufactured.

  The organic EL device and the organic EL display of the present invention can be used not only as an organic EL television, for example, but also as a display unit in various electronic devices such as portable information processing devices such as word processors and personal computers and wristwatch-type electronic devices. be able to.

(A) is a diagram (upper surface) schematically showing the structure of the organic EL display according to the embodiment of the present invention, and (b) is one of the organic TFT devices constituting the organic EL display according to the embodiment. The figure which shows the outline which shows the cross section (the 1), (c) is the figure which shows the outline which shows one cross section (the 2) which comprises the organic EL display which concerns on the embodiment The figure explaining the manufacturing method of the bottom gate type transistor element concerning embodiment of this invention Schematic showing a gravure printing apparatus according to an embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Gate insulating layer 4 Source electrode 5 Drain electrode 6 Bank layer 7 Organic TFT layer 8 Overcoat layer 9 Planarizing film layer G Gap 10 Transistor device

Claims (3)

An organic EL light emitting device including a pixel electrode;
A gate electrode formed on the substrate;
A gate insulating layer covering a surface of the gate electrode and a substrate provided on the gate electrode;
A source electrode and a drain electrode formed on the gate insulating layer with a gap;
An organic TFT layer provided in the gap and connecting the electrodes;
An organic EL device having
A bank layer is provided outside the organic TFT layer, and an overcoat layer is provided on the surface including the bank layer and the organic TFT layer,
The overcoat layer, the bank layer, and the gate insulating layer are all made of the same polyimide-based material. A planarization film layer is further formed on the surface of the overcoat layer, and the planarization film layer, the overcoat layer, the bank layer, and the gate insulating layer are made of the same polyimide material. claim 1 Symbol placement organic EL device to. By combining a plurality of organic EL device according to claim 1 or 2, an organic EL display, characterized in that the organic EL display.

Images