JP2010062241A - Manufacturing method for organic thin film transistor, organic thin film transistor, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an organic thin film transistor in which a plurality of separated thin films are formed on a substrate through single-time ink jet discharge, to provide the organic thin film transistor which has a small Off current and also has excellent average mobility by the manufacturing method, and to provide a display device having the transistor. <P>SOLUTION: The manufacturing method for the organic thin film transistor including a stage of forming at least one of a conductive layer, insulating layer and organic semiconductor layer on the substrate through an ink jet process comprises the stage of forming the plurality of separated thin films on the substrate through the single-time ink jet discharge when at least the one of the conductive layer, insulating layer and organic semiconductor layer is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an organic thin film transistor, an organic thin film transistor element, and a display device.

  In an FPD (flat panel display) such as a liquid crystal display device (LCD: Liquid Crystal Display), an organic electroluminescence element (hereinafter also referred to as an organic EL element), or an electrophoretic device, an active matrix drive type display device (also referred to as a display or the like). ) Is the mainstream.

  Such a display device (display) is provided with a driving unit composed of a thin film transistor (hereinafter also referred to as TFT) for each pixel, and particularly by using an active matrix driving type display, The screen rewriting speed can be secured.

  In addition, matrix type display elements are used in various types and in large numbers as display elements that realize light weight, thinness, high image quality, and high definition.

  The matrix type display element includes a matrix-like bus wiring, an optical material (light emitting material or light modulation material), and another structure as necessary.

  Here, in the case of a single-color matrix display element, wirings and electrodes need to be arranged in a matrix on the display substrate, but the optical material can be uniformly applied to the entire surface of the display substrate.

  On the other hand, when trying to realize a display device having a color matrix type display element with an organic EL element which is a self-luminous type, three pixel electrodes are arranged for each pixel corresponding to the three primary colors of RGB, In addition, it is necessary to selectively arrange an optical material corresponding to one of RGB for each pixel electrode at a predetermined position.

  Recently, an optical material is applied by an ink jet method in a process of applying an optical material by patterning.

  However, when applying an optical material by an ink jet method, the optical material must be diluted several tens of times with a solvent, so its fluidity is high, and after application, the application position is completely solidified. It has proved difficult to hold on.

  In addition, due to the fluidity of the liquid optical material, there is a problem in that the patterning accuracy is insufficient. The optical material applied to the pixel flows out to the adjacent pixel, so that the optical characteristics of the pixel deteriorate. Alternatively, there is a problem that, for each pixel, a variation in the coating area causes a variation in the coating thickness and a variation in the optical characteristics of the optical material.

  A step of applying an organic semiconductor material dissolved in a solvent to a substrate by an inkjet method in order to solve the problems at the time of applying the ink jet, and a step of forming the organic semiconductor film on the substrate by evaporating the solvent; , A method for selectively forming an organic semiconductor film on a substrate is disclosed (for example, see Patent Document 1).

  However, in the above technique, it is necessary to form a single film formation region (specifically, an organic layer) by ejecting one or more droplets of ink jet. And adjustment of the interval between dots ejected with high accuracy is difficult, and there are problems such as thinning of the organic layer and miniaturization of the film formation region of the organic layer.

  On the other hand, in order to increase the aperture ratio of each pixel of the display and to allow more current to flow through one transistor, it is necessary to form a longer channel width and a shorter channel length in a very small area. Therefore, it is necessary to arrange the comb-shaped electrodes with almost no space between the electrodes.

In addition, there is a problem that discharging a solution for each channel is inefficient in terms of production of a thin film transistor from the viewpoint of cost and time.
JP 2004-253375 A

  An object of the present invention is to provide a method of manufacturing an organic thin film transistor capable of forming a plurality of separated thin films on a substrate by a single inkjet discharge, which has a low off current and an average mobility. An organic thin film transistor is provided, and a display device including the transistor is provided.

  The above object of the present invention has been achieved by the following constitution.

1. In the method of manufacturing an organic thin film transistor, the method includes forming a conductive layer, an insulating layer, and an organic semiconductor layer on a substrate by an inkjet process.
When forming at least one layer of the conductive layer, the insulating layer, and the organic semiconductor layer, the method includes a step of forming a plurality of separated thin films on the substrate by one inkjet discharge. A method for manufacturing an organic thin film transistor.

  2. 2. The method for producing an organic thin film transistor according to 1 above, wherein 2 to 4 organic semiconductor layers separated by one inkjet discharge are formed on the substrate.

  3. 3. The method of manufacturing an organic thin film transistor according to 1 or 2 above, wherein regions having different surface energies are provided on the substrate.

  4). 3. The method for producing an organic thin film transistor according to 1 or 2 above, wherein the surface of the substrate has irregularities.

  5. 5. The method of manufacturing an organic thin film transistor according to any one of 1 to 4, wherein the organic semiconductor layer includes a low molecular organic semiconductor material.

  6). 6. An organic thin film transistor element manufactured using the method for manufacturing an organic thin film transistor according to any one of 1 to 5 above.

  7). 7. A display device comprising the organic thin film transistor element as described in 6 above.

  According to the present invention, a method for manufacturing an organic thin film transistor capable of forming a plurality of separated thin films on a substrate by a single inkjet discharge is provided. The manufacturing method provides low off current and good average mobility. An organic thin film transistor was provided, and a display device including the transistor could be provided.

  In the method for producing an organic thin film transistor of the present invention, an organic film capable of forming a plurality of separated thin films on a substrate by a single ink jet discharge with the structure defined in any one of claims 1 to 5. A method for producing a thin film transistor was provided, and an organic thin film transistor having a low off-current and good average mobility could be provided by the production method.

  Further, it was found that the display device provided with the organic thin film transistor element of the present invention exhibits good light emission characteristics.

  Hereinafter, details of each component according to the present invention will be sequentially described.

<< Method for Manufacturing Organic Thin Film Transistor >>
The method of manufacturing an organic thin film transistor according to the present invention includes the step of forming at least one layer of a conductive layer, an insulating layer, and an organic semiconductor layer on a substrate by an inkjet process as described in claim 1. In
When forming at least one layer of a conductive layer, an insulating layer, and an organic semiconductor layer, it is possible to form a plurality of separated thin films on a substrate by a single inkjet discharge. It has been made thinner.

  In addition, it is possible to form a patterning film in an inkjet process, which conventionally required multiple inkjet ejections for patterning (reducing the number of inkjet ejections), thereby reducing the cost of manufacturing thin film transistors. Was able to be realized.

  In the method for producing an organic thin film transistor of the present invention, when forming at least one layer of a conductive layer, an insulating layer, and an organic semiconductor layer, a plurality of separated thin films are formed on a substrate by a single inkjet discharge (specifically, Means that the conductive layers, insulating layers, and organic semiconductor layers of a plurality of transistors are formed by a single inkjet discharge.) Preferably, the conductive layers, insulating layers, and organic layers described above are used. It is preferable that a plurality of separated thin films are formed on the substrate by each inkjet discharge, and particularly preferably, 2 to 4 semiconductor layers are separated by one inkjet discharge. Each of the organic semiconductor layers of the transistor is preferably formed.

As a means for forming at least one layer of the conductive layer (electrode), insulating layer and organic semiconductor layer according to the present invention as a plurality of thin films separated on a substrate,
(A) providing regions with different surface energies on the substrate;
(B) providing irregularities on the surface of the substrate;
Etc. are mentioned as a preferable method.

  The conductive layer (electrode), insulating layer, organic semiconductor layer and the like according to the present invention will be described in detail in the configuration of the organic thin film transistor described later.

  Hereinafter, it demonstrates in order.

(A) Providing a Region with Different Surface Energy on the Substrate As for providing a region with different surface energy on the substrate, one pixel in a part of the manufacturing process of the display device of the present invention shown in FIGS. A description will be given focusing on the process of providing each of the two transistors on the top with an organic semiconductor layer by one drop of ink jet ejection.

  In the embodiment, a mode in which an organic semiconductor layer is formed in a high surface energy region and a mode in which conductive layers such as a source electrode and a drain electrode are formed are specifically shown.

  FIG. 1A is a circuit diagram showing a part of the display device 100 of the present invention. In the display device 100, a plurality of scanning lines 103 and a plurality of power supply lines 108 provided in a direction intersecting with the plurality of scanning lines 103 are arranged on a substrate (not shown). It has a configuration. A pixel region (also simply referred to as a pixel) is provided for each intersection of the scanning line 103 and the power supply line 108.

  1A to 1C, two transistors, that is, a switching thin film transistor T1 and a driving thin film transistor T2 are provided on one pixel.

  In the pixel region, a scanning signal is supplied to a gate electrode (not shown) through a scanning line 103, a switching thin film transistor T1, a storage capacitor C that holds an image signal through the switching thin film transistor T1, and the An organic EL element 106 is provided in the driving thin film transistor T2 and the driving thin film transistor T2 that supply the image signal held by the holding capacitor C to the gate electrode. 109 represents grounding.

  In FIG. 1A, as a region for providing the switching thin film transistor T1 and the driving thin film transistor T2 disposed in the pixel region, a high surface energy region 101 is formed in the pixel region in which T1 and T2 are provided.

  A region other than the high surface energy region 101 is shown as a low surface energy region 102 in the pixel region.

  In the formation of the switching thin film transistor T1 and the driving thin film transistor T2, details of providing each of the high surface energy regions 101 in the regions where the organic semiconductor layers are provided will be described in the organic thin film transistor 2 of the embodiment described later. (Not specifically shown in FIG. 1) After providing a gate electrode (not shown) and a gate insulating layer (not shown) on the octyltrichlorosilane (OTS) monomolecular film (SAM After forming a film: Self assembled monolayer (self-assembled film), ultraviolet irradiation (254 nm) is performed through a mask from a low-pressure mercury lamp, the OTS in the exposed part is photodegraded, and the region where the SAM film disappears is A high surface energy region 101 is formed, and the high surface energy region 101 is The organic semiconductor material is supplied by the ink jet discharge, and the organic semiconductor layer 111 is formed.

(High surface energy region)
In FIG. 1A, the difference in surface energy between each of the switching thin film transistor T1 and the driving thin film transistor T2 forming the high surface energy region and the other region in the pixel region is 3 mN / m to 50 mN / m. It is preferable to adjust so that it is the range.

  The surface energy can be obtained by measuring the contact angle. The contact angle can be measured using a contact angle meter (CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.) in an environment of 20 ° C. and 50% RH. Measured below and obtained.

  From the contact angle, the degree of hydrophobicity on the substrate surface can be determined by measuring the contact angle of water. In addition, the measurement of the surface energy of the high surface energy region and other regions on one pixel is performed indirectly by separately preparing a sample with or without the SAM film and measuring the surface energy, for example. Can also be measured.

(B) providing irregularities on the surface of the substrate;
As for providing a region having unevenness on the surface of the substrate, for example, after forming a thin film such as the SAM film, the region having unevenness can be provided by light irradiation through a mask.

  The unevenness | corrugation which concerns on this invention is represented by surface roughness Ra as described in JISB0601-1994, and a concrete surface roughness meter or an AFM (Atomic Force Microscope: An atomic force microscope) can be used.

  In FIG. 1A, after the high surface energy region 101 is provided in each of the transistors T1 and T2, as shown in FIG. 1B, the two transistors T1 and T2 have a high height by one inkjet discharge. An ink jet droplet 110 containing an organic semiconductor material is supplied so as to cover the surface energy region 101.

  In the process in which the inkjet droplet 110 is supplied and dried, the droplet containing the organic semiconductor material converges on the high surface energy region 101, and as shown in FIG. 1C, the organic semiconductor layer is formed on the transistors T1 and T2. 111 is obtained.

  As a preferable example having a circuit diagram of the display device of the present invention manufactured in the steps of FIGS. 1A to 1C, there is an organic electroluminescence display panel (also referred to as an organic EL display panel). This will be briefly described with reference to FIG.

  In the organic EL display panel of FIG. 2, the scanning line 103 and the power feeding property 108 are provided on the substrate 502 so as to be electrically separated from each other at positions orthogonal to each other, and the scanning line 103 and the power feeding line 108 are further provided. A connected organic thin film transistor element 505 (FIG. 1 shows a configuration having two transistors T1 and T2), and light emitting portions R (red), G (green) connected to the organic thin film transistor element 505, A plurality of island-shaped pixel electrodes (also referred to as display electrodes) corresponding to B (blue) are formed.

  The details of the solvent for inkjet discharge, the substrate constituting the organic semiconductor layer, the electrode, and the organic semiconductor layer according to the method for manufacturing the organic thin film transistor of the present invention will be described separately. In the method for manufacturing the organic thin film transistor of the present invention, In the case of constituting an organic thin film transistor, it is formed on a substrate having a highly hydrophobic film such as a gate insulating film (for example, a thermal oxide film of silicon). A thing with high property is preferable. As the solvent having a high affinity for the substrate, an aliphatic hydrocarbon is suitable. Aromatic hydrocarbons such as toluene, chain aliphatic hydrocarbons such as hexane and heptane, cyclic aliphatic hydrocarbons such as cyclohexane and cyclopentane, and halogenated hydrocarbons such as chloroform and 1,2-dichloroethane, Depending on the type of organic semiconductor material used, such as chain ethers such as diethyl ether and diisopropyl ether, cyclic ethers such as tetrahydrofuran and dioxane, ketones such as acetone and methyl ethyl ketone, etc. Good. An optimum material can be selected and used depending on the substrate material on which the organic semiconductor material film is formed.

  In addition, another solvent having high solubility in the organic semiconductor material may be used to promote the dissolution of the organic semiconductor material. When applied on the substrate, the solvent can be used within a range that does not cause repelling.

  The content of the organic semiconductor material in the solvent varies depending on the type of the solvent to be used and the specific selection of the organic semiconductor material to be described later, but by applying these liquid materials on the substrate by coating, the thin film is formed. In order to form it, the content of the organic semiconductor material in the solution (in the dispersion) from the viewpoint of effectively preventing uniform spreading on the substrate and pinholes of the coating film on the substrate, etc. Is dissolved (may be partially dispersed) in the range of 0.01% by mass to 10.0% by mass, preferably 0.1% by mass to 5.0% by mass.

  Note that in the present invention, when forming at least one layer of the conductive layer, the insulating layer, and the organic semiconductor layer, a step of forming a plurality of separated thin films on the substrate by one inkjet discharge is performed. In addition to inkjet discharge, the film formation method includes spin coating, screen printing, inkjet printing, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, Reverse roll coater method, transfer roll coater method, gravure coater method, kiss coater method, cast coater method, spray coater method, slit orifice coater method, calendar coater method, dipping method, spray method, dripping method, Langmyer / Blodgett method, etc. Various solution processes as required It can be used.

<Structure of organic thin film transistor>
A layer configuration example of the organic thin film transistor element of the present invention will be described with reference to FIG.

  The organic thin film transistor element of the present invention is formed of a base material, a gate electrode, a gate insulating film, an organic semiconductor layer, a source electrode, and a drain electrode, and is a type of transistor generally called a MIS type (metal-insulator-semiconductor type) transistor. is there.

  In the MIS transistor, the electric field applied to the gate electrode is adjusted to control the conductivity of the semiconductor layer through the insulating layer, and as a result, the amount of current flows from the source electrode installed at both ends of the semiconductor layer to the drain electrode. Can be controlled.

  Among such MIS transistors, they can be classified into several types according to the structure of each layer.

  First, a top gate type having a source electrode and a drain electrode connected by an organic semiconductor film (hereinafter also referred to as an organic semiconductor layer) on a substrate, and having a gate electrode on the gate electrode via a gate insulating layer, First, it is roughly classified into a bottom gate type having a gate electrode and having a source electrode and a drain electrode connected by an organic semiconductor film through a gate insulating layer.

  Furthermore, when viewed from the gate electrode, the source electrode and the drain electrode can be distinguished into a bottom contact type in front of the organic semiconductor layer and a top contact type on the other side of the organic semiconductor layer, and by combining both, Four types of organic thin film transistors can be configured. The organic thin film transistor of the present invention may be any of the top gate type, the bottom gate type, the top contact type, and the bottom contact type, and can be selected according to the use of the organic thin film transistor.

  An example of a specific layer structure of the element is shown in FIGS. 3 (a) to 3 (e) below.

  3A and 3C show top layer / bottom contact layer configuration examples. A source electrode 2 and a drain electrode 3 are provided on a base 6, and an organic semiconductor film 1 is formed thereon. Further, the gate insulating layer 5 is formed in contact with the organic semiconductor film 1, and the gate electrode 4 is provided thereon.

  FIG. 3B shows an example of a layer structure of a top gate / top contact type. A substrate 6 has a gate electrode 4 on which a gate insulating layer 5 is formed. The organic semiconductor film 1 is formed thereon, and the source electrode 2 and the drain electrode 3 are formed in contact with the organic semiconductor film 1.

  FIGS. 3D and 3F show examples of bottom gate / bottom contact type layer structures. A substrate 6 has a gate electrode 4 on which a gate insulating layer 5 is formed. The source electrode 2 and the drain electrode 3 are formed thereon, and the organic semiconductor film 1 is formed thereon.

  FIG. 3E shows a layer configuration example of a bottom gate / top contact type. A substrate 6 has a gate electrode 4 on which a gate insulating layer 5 is formed. The organic semiconductor film 1 is formed thereon, and the source electrode 2 and the drain electrode 3 are formed thereon.

  More preferably, the organic thin film transistor of the present invention has a bottom-gate / bottom-contact type structure shown in FIGS. 3 (c) and 3 (f).

  Since the organic semiconductor material may be deteriorated by oxygen, moisture, heat, or the like, the damage in forming other layers can be reduced by forming it in the latter half of the process as much as possible.

  From this point of view, the bottom gate / bottom contact type element can form the organic semiconductor layer in the second half of the process, so that an organic thin film transistor having good characteristics with little deterioration can be obtained.

<< Electrode (also referred to as conductive layer) >>
Next, an electrode material for forming the gate electrode and the source / drain electrode and a method for forming the electrode material will be described.

  In the organic thin film transistor of the present invention, the material constituting the gate electrode and the wiring portion connecting the electrode and the power source is not particularly limited as long as it is a conductive material, and is formed of a known electrode material. The electrode material is not particularly limited as long as it is a conductive material. Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, Germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium , Scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum Miniumu mixture, a magnesium / indium mixture, aluminum / aluminum oxide mixture, a lithium / aluminum mixture, or the like is used. Alternatively, a known conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene (polyethylenedioxythiophene and polystyrenesulfonic acid complex, etc.) is also preferably used.

  Further, the material for forming the source / drain electrode is not particularly limited as long as it contains a metal that can be combined with the above-described electrode modifying compound among the materials listed above. Platinum, gold, silver, nickel, chromium, Copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc , Carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, Lithium, aluminum, magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, and lithium / aluminum mixtures.

  Among them, those having a small electric resistance at the contact surface with the semiconductor layer are preferable, and platinum, gold, silver, and copper are preferable when the semiconductor layer is a p-type semiconductor. Among them, gold is preferable because it has a small potential difference with respect to the organic semiconductor material and has a small carrier injection barrier from the electrode to the organic semiconductor. Further, since gold does not form an oxide film on the electrode surface due to oxidation or the like, there is no fear that the reactivity between the electrode surface and the electrode modifying compound according to the present invention is lowered.

  As the conductive material other than the contact surface with the semiconductor, it is more preferable to use a metal other than gold or another conductive material. For example, there are materials below the contact surface of the source / drain and connection wiring to the source / drain.

  As a method for forming an electrode, a conductive thin film formed using a dry process such as vapor deposition or sputtering using the above as a raw material, and a method for forming an electrode shape using a known photolithography method or a lift-off method, aluminum, copper, or the like A method in which a resist is formed on a metal foil by thermal transfer, ink jet, etc., patterned by etching, transferred by laser ablation, etc., or a conductive polymer solution or dispersion containing metal fine particles, conductive ink, conductive A method of forming a conductive paste or the like by a solution process such as a printing method such as relief printing, intaglio printing, lithographic printing, screen printing, and ink jet process (also simply referred to as an ink jet method or an ink jet printing method) is preferable, and an ink jet process is particularly preferable. It is done.

  As a means for forming the shape of the source electrode and the drain electrode, it is preferable to use a photolithographic method or an inkjet method.

  The above-described electrode modifying compound is an electrode having a controlled thickness because the surface of the electrode is oxidized to form an oxide film, or when dirt due to an organic substance is attached, the reactivity with the electrode decreases. Since it may be difficult to form a coating layer of a modifying compound, when forming a coating layer using the above-described electrode modifying compound, an electrode is formed using a known cleaning method immediately before forming the coating layer. It is preferable to clean the surface cleanly.

  Examples of such an electrode surface cleaning method include treatment with strong acid and strong alkali, ultraviolet irradiation, ozone treatment, corona discharge treatment, plasma treatment and the like. Of these, plasma treatment is preferred, and atmospheric pressure plasma treatment is more preferred.

  The atmospheric pressure plasma treatment is a treatment in which a gas containing plasma generated by applying an electric field between opposing electrodes under atmospheric pressure is sprayed onto a substrate. Atmospheric pressure plasma processing has a higher density of active species than vacuum plasma processing, so the electrode surface can be processed at high speed and high efficiency, and since there is no need to use a vacuum during processing, the number of processes can be reduced. There is an advantage that you can. The atmospheric pressure plasma treatment can be performed with reference to Japanese Patent Application Laid-Open No. 2003-309266.

  In addition, it is desirable that the source electrode, the drain electrode, and the like have a comb shape.

<< Organic semiconductor layer (also referred to as organic semiconductor film) >>
As the organic semiconductor material constituting the organic semiconductor layer (organic semiconductor film) according to the present invention, it is preferable to use a low molecular organic semiconductor material. Examples of the low molecular organic semiconductor material include various condensed polycyclic aromas shown below. Group compounds and conjugated compounds can also be used.

  Examples of the condensed polycyclic aromatic compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, thacumanthracene, bisanthene, zeslen, heptazelene. , Pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, and the like, and derivatives and precursors thereof.

  Examples of the conjugated compound include polythiophene and its oligomer, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, tetrathiafulvalene compound, quinone Compounds, cyano compounds such as tetracyanoquinodimethane, fullerenes and derivatives or mixtures thereof.

  In particular, among polythiophene and oligomers thereof, thiophene hexamer α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3- Oligomers such as butoxypropyl) -α-sexithiophene can be preferably used.

  Furthermore, porphyrin, copper phthalocyanine, metal phthalocyanines such as fluorine-substituted copper phthalocyanine described in JP-A No. 11-251601, naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4- Trifluoromethylbenzyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide with N, N′-bis (1H, 1H-perfluorooctyl), N, N′-bis (1H, 1H-perfluorobutyl) and N, N'-dioctylnaphthalene 1,4,5,8-tetracarboxylic acid diimide derivatives, naphthalene 2,3,6,7 naphthalene tetracarboxylic acid diimides such as tetracarboxylic acid diimide, and anthracene 2,3,6 Condensation of anthracene tetracarboxylic acid diimides such as 7-tetracarboxylic acid diimide Organic molecules such as tetracarboxylic acid diimides, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTTF-iodine complex, TCNQ-iodine complex Complexes, fullerenes such as C60, C70, C76, C78, and C84, carbon nanotubes such as SWNT, dyes such as merocyanine dyes and hemicyanine dyes, σ-conjugated polymers such as polysilane and polygerman, and JP-A 2000-260999 The organic-inorganic hybrid material described in the publication can also be used.

  Among these π-conjugated materials, at least one selected from the group consisting of condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic acid diimides, metal phthalocyanines, and metal porphyrins is preferable.

  As a method for forming the organic semiconductor layer, physical vapor deposition methods such as a vacuum deposition method, an MBE (Molecular Beam Epitaxy) method, an ion cluster beam method, a low energy ion beam method, an ion plating method, and a sputtering method ( PVD method) and chemical vapor deposition (CVD method) dry process, spin coating method, screen printing method, ink jet process, air doctor coater method, blade coater method, rod coater method, knife coater method, squeeze coater Method, reverse roll coater method, transfer roll coater method, gravure coater method, kiss coater method, cast coater method, spray coater method, slit orifice coater method, calendar coater method, dipping method, spray method, dripping method, Langmyr A solution process such as a blow jet method can be mentioned, but in the present invention, it is particularly preferable to use an ink jet process.

  In the organic thin film transistor of the present invention, it is preferable to form the organic semiconductor layer by a solution process among the above processes. If it can be formed by a solution process, the number of steps can be greatly reduced, and not only can an organic thin film transistor be formed by a simple process, but also a crystal larger than that formed by a dry process can be formed. As a result, an organic thin film transistor having good mobility can be formed.

  The film thickness of these organic semiconductor films is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the organic semiconductor film, and the film thickness varies depending on the organic semiconductor, but is generally 10 nm. ˜1 μm, preferably 20 nm to 500 nm, more preferably 30 nm to 300 nm.

<< Gate insulating film (also called insulating layer) >>
As the gate insulating layer (insulating layer) of the organic thin film transistor of the present invention, various insulating films can be used. For example, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium titanate. Strontium, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, barium titanate, magnesium barium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, niobium tantalate Metal oxides such as bismuth and trioxide yttrium, metal nitrides such as silicon nitride, aluminum nitride, boron nitride, and titanium nitride, polymethyl methacrylate (PMMA), polyvinylphenol (PVP), poly Nyl alcohol (PVA), polyimide, polyamide, polyester, polyacrylate, photo radical polymerization system, photo cation polymerization photo curable resin such as epoxy resin and oxetane resin, or copolymer containing acrylonitrile component, polyvinyl phenol, Examples include polyvinyl alcohol, novolak resin, and organic insulating materials such as resins made from natural polysaccharides such as cyanoethyl pullulan and triacetyl cellulose, gelatin, and parylene formed by low-temperature chemical vapor deposition, Combinations of these can also be used.

  Among these materials, it is preferable to use a material having a high dielectric breakdown voltage and a high relative dielectric constant. With a material having a high dielectric breakdown voltage, the film pressure of the insulating film can be reduced, the production speed can be increased, and the occurrence of cracks and peeling when the element is bent can be reduced. If a material having a high relative dielectric constant is used, a channel can be formed with a low gate voltage, and an organic thin film transistor that can be driven with a low voltage can be obtained. As an insulating film material satisfying such characteristics, silicon oxide, silicon nitride, polyvinylphenol, and polyimide can be preferably used.

  The insulating film can be formed by vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, chemical vapor deposition (CVD) method, sputtering method, atmospheric pressure plasma CVD. Dry processes such as spray coating, spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, etc. And a method of forming the surface of the gate electrode by oxidation or nitridation. Among these, an inkjet process is preferable.

  As a wet process, for example, for an Au electrode, an insulating molecule having a functional group capable of forming a chemical bond with a gate electrode, such as a hydrocarbon modified at one end with a mercapto group and an alkylsilane. Thus, an insulating film can also be formed on the surface of the gate electrode by coating the surface of the gate electrode in a self-organizing manner by a method such as immersion.

  The insulating film can also be formed by using a technique such as oxidizing or nitriding the surface of the gate electrode. Examples of the method for oxidizing the gate electrode include an oxidation method using oxygen plasma and an anodic oxidation method. As a method for nitriding the surface of the gate electrode, a nitriding method using nitrogen plasma can be exemplified.

  Among these, the method for forming an inorganic thin film is preferably an anodic oxidation method, an atmospheric pressure plasma CVD method, or a combination thereof.

  The anodized film can be formed on the surface of the metal by anodizing a metal that can be anodized by a known method. Examples of the metal that can be anodized include aluminum and tantalum. Any electrolyte solution that can form a porous oxide film can be used as the anodizing treatment. Generally, sulfuric acid, phosphoric acid, oxalic acid, chromic acid, boric acid, sulfamic acid, benzenesulfone, and the like can be used. An acid or the like, or a mixed acid obtained by combining two or more of these or a salt thereof is used.

The treatment conditions for anodization vary depending on the electrolytic solution used, and thus cannot be specified in general. In general, the concentration of the electrolytic solution is 1% by mass to 80% by mass, and the temperature of the electrolytic solution is 5 ° C. to 70 ° C. It is preferable to adjust the current density to 0.5 A / dm ^{2 to} 60 A / dm ² , voltage 1 V to 100 V, and electrolysis time 10 seconds to 5 minutes.

A preferred anodizing treatment is a method in which an aqueous solution of sulfuric acid, phosphoric acid or boric acid is used as the electrolytic solution and the treatment is performed with a direct current, but an alternating current can also be used. Preferably the concentration of these acids is 5 wt% to 45 wt%, temperature 20 ° C. to 50 ° C. of the electrolytic solution at a current density of ^{0.5A / dm 2 ~20A / dm 2} 20 seconds to 250 seconds electrolytic treatment It is preferable to do this.

  The atmospheric pressure plasma CVD method is a fine particle generated by introducing a raw material compound that forms a thin film into a plasma generated by applying an electric field between opposing electrodes under atmospheric pressure, and causing a chemical reaction in the plasma. Is a method of forming a thin film by depositing on a substrate, and the method is known as described in JP-A-11-43781, JP-A-2003-179234, WO04 / 75279, etc. It can be created using the technology.

  As the method for forming an insulating film made of an organic compound, the wet process is preferable.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

"substrate"
As the substrate for forming the organic thin film transistor, various materials can be used, for example, ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide, silicon, germanium, gallium arsenide, gallium phosphide, A semiconductor substrate such as gallium nitrogen, paper, nonwoven fabric, etc., and a substrate made of a metal such as stainless steel and aluminum having a thickness that can be bent can be used, but in the present invention, the substrate is preferably made of a resin, For example, a plastic film sheet can be used.

  Examples of the plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), Examples thereof include films made of cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like.

  By using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, and the portability can be improved and the resistance to impact can be improved. Further, it becomes possible to incorporate or integrate a field effect transistor into a display device or electronic device having a curved shape.

<Underlayer>
In the organic thin film transistor of the present invention, when the substrate is a plastic film, an undercoat layer containing a compound selected from an inorganic oxide and an inorganic nitride, and a polymer in order to improve the adhesion between the substrate and the organic thin film transistor It is preferable to have at least one of the undercoat layers containing.

  Inorganic oxides contained in the undercoat layer include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, titanate Examples thereof include lead lanthanum, strontium titanate, barium titanate, barium fluoride magnesium, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Examples of the inorganic nitride include silicon nitride and aluminum nitride.

  Of these, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, and silicon nitride are preferable.

  In the present invention, as a method for forming an undercoat layer containing a compound selected from inorganic oxides and inorganic nitrides, the same method for forming an inorganic oxide or inorganic nitride as the above-described gate insulating film forming method is used. However, it is preferably formed by an atmospheric pressure plasma method.

  Polymers used for the undercoat layer containing polymer include polyester resin, polycarbonate resin, cellulose resin, gelatin, acrylic resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, phenoxy resin, norbornene resin, epoxy resin, vinyl chloride Vinyl acetate copolymer, vinyl chloride resin, vinyl acetate resin, copolymer of vinyl acetate and vinyl alcohol, partially hydrolyzed vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile Copolymers, ethylene-vinyl alcohol copolymers, polyvinyl alcohol, chlorinated polyvinyl chloride, ethylene-vinyl chloride copolymers, vinyl polymers such as ethylene-vinyl acetate copolymers, polyamide resins, ethylene-butadiene Down resin, a butadiene - rubber resin such as acrylonitrile resin, silicone resin, and fluorine resins.

[Protective layer]
Moreover, it is also possible to provide a protective layer on the organic thin film transistor of the present invention. Examples of the protective layer include inorganic oxides or inorganic nitrides, metal thin films such as aluminum, polymer films with low gas permeability, and laminates thereof. By having such a protective layer, organic thin film transistors Durability is improved. As a method for forming these protective layers, the same method as the method for forming the gate insulating film described above can be used. Further, the protective layer may be provided by a method such as simply laminating a film in which various inorganic oxides are laminated on a polymer film.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  Moreover, the structure of the organic-semiconductor material (1) used for an Example is shown below.

Example 1
<< Manufacture of Organic Thin Film Transistor 1 >>: Comparative Example The manufacture of the organic thin film transistor 1 (comparative example) will be described based on a circuit diagram showing a part of the display device shown in FIG. However, in the manufacture of the organic thin film transistor 1 (comparative example), the high surface energy regions 101 and 102 shown in FIG. 1A are not provided.

  A thermal oxide film having a thickness of 200 nm was formed on an n-type Si wafer having a specific resistance of 0.02 Ω · cm to form a gate insulating film.

  Next, a 1% by weight toluene solution of the organic semiconductor material (1) is prepared, and each channel (specifically, a region where the switching thin film transistor T1 and the driving thin film transistor T2 are formed) using an inkjet head having a drop size of 14 pl. Each was discharged from directly above.

(Inkjet discharge is a mode in which two droplets are discharged.)
As a result, the organic semiconductor thin film was formed in the region including each channel part, but the organic semiconductor film was partially formed in the other region, and as a result, the organic semiconductor layer was a continuous film. There was also.

  Cabot silver nano ink was ejected to both ends of the organic semiconductor layer using an inkjet head.

Satellite dots were also confirmed, but the average mobility calculated from the Id-Vg curve of the resulting transistor element was 0.01 cm ² / Vs, the off current was 100 pA, the off current was large, and the transistor characteristics were Was found to be practically insufficient.

  In the element patterns formed in this comparative example and example, comb electrodes having a channel length of 10 μm and a channel width of 500 μm are arranged with a gap of 2 channels and 100 μm per pixel.

<< Manufacture of Organic Thin-Film Transistor 2 >>: Present Invention As described in FIGS. 1A to 1C, the organic thin-film transistor 2 (present invention) described in the circuit diagram showing a part of the display device of the present invention is provided. Manufactured.

  In manufacturing the organic thin film transistor 2 (the present invention), the high surface energy regions 101 and 102 shown in FIG. 1A are provided.

  Here, the manufacturing process of the organic thin-film transistor 2, which is a preferred embodiment of the present invention, will be described with reference to FIG.

A 200 nm-thick thermal oxide film was formed on an n-type Si wafer 201 having a specific resistance of 0.02 Ω · cm to form a gate insulating film 202. (Fig. 4 (a))
This substrate was immersed in a toluene solution (0.1% by mass, 60 ° C.) of octyltrichlorosilane (OTS) to form an OTS SAM film 203 on the entire surface. (Fig. 4 (b)
When this surface was covered with a mask having an opening only in the channel portion and exposed to ultraviolet light (254 nm), the exposed portion 204 was formed with a higher surface energy region than the non-exposed portion.

  This was confirmed by separately preparing a substrate with or without the SAM film 203 and measuring the surface energy.

  The surface of the low surface energy SAM film was 25 mN / m, and the surface corresponding to the exposed portion of the high surface energy was 70 mN / m. Incidentally, the exposure unit 204 corresponds to the high surface energy region 101 in FIG. (FIG. 4 (c)).

  Next, a 1% by mass toluene solution of the organic semiconductor material (1) is prepared, and a switching thin film transistor T1 and a driving thin film transistor T2 in the pixel are arranged as shown in FIG. 1B using an ink jet head having a drop size of 14 pl. One drop was discharged to the area.

  As a result, an organic semiconductor layer 205 having a thickness of 200 nm was formed on the exposed portion 204. (FIG. 4 (d)).

  When both ends of the organic semiconductor layer 205 were covered with a mask having an opening only in the channel portion and exposed to ultraviolet light (254 nm), an exposed portion 206 having a higher surface energy than the non-exposed portion was formed. (FIG. 3 (e)). Separately, the surface energy difference between the exposed portion 204 and the non-exposed portion of the surface energy of the exposed portion 206 was 45 mN / m. (FIG. 4 (e)).

  Next, the silver nano ink described above was ejected to the exposure unit 206 using an ink jet head, and the source electrode 207 and the drain electrode 208 were produced. (FIG. 4 (f)).

The average mobility calculated from the Id-Vg curve of the obtained organic thin film transistor 2 was 0.1 cm ² / Vs, and the off current was 1 pA, indicating good transistor characteristics.

<< Manufacture of organic thin film transistor 3 >>
As shown in FIGS. 1A to 1C, the organic thin film transistor 3 (the present invention) described in the circuit diagram showing a part of the display device of the present invention is manufactured.

  In the production of the organic thin film transistor 3 (the present invention), the high surface energy regions 101 and 102 shown in FIG. 1A are provided.

  Here, the manufacturing process of the organic thin-film transistor 3, which is a preferred embodiment of the present invention, will be described with reference to FIG.

A gate electrode 302 was formed by patterning Cr on a glass substrate using photolithography. Next, a polysilazane toluene solution was spin-coated and heat-treated to form a SiO ₂ thin film, which was used as the gate insulating film 303. (FIGS. 5A to 5C).

  Next, it was immersed in a toluene solution of octyltrichlorosilane (OTS) (0.1% by mass, 60 ° C.) to form an OTS SAM film (self-assembled film) on the entire surface. (FIG. 5D).

  When this surface was covered with a mask having an opening only in the channel portion and subjected to UV exposure (254 nm), the surface energy of the exposed portion 305 increased compared to the non-exposed portion. (FIG. 5 (e)).

  Next, a 1% by mass toluene solution of the organic semiconductor material (1) was prepared, and one drop was discharged per pixel using an inkjet head having a drop size of 14 pl.

  As a result, an organic semiconductor layer 306 having a thickness of 50 nm is formed only in each channel portion (for example, the public surface energy region 101 formed in the portions T1 and T2 in FIG. 1A). No semiconductor film was formed in this region. (FIG. 5 (f)).

  When both ends of the organic semiconductor layer 306 were covered with a mask having an opening only in the channel portion and exposed to ultraviolet light (254 nm), an exposed portion 307 having a higher surface energy than the non-exposed portion was formed. (FIG. 4 (g)). Separately, the surface energy difference between the surface energy of each of the exposure part 305 and the exposure part 307 and the non-exposure part was 40 mN / m. (FIG. 5 (g)).

  Next, the above silver nano-ink was ejected to the exposure portions 307 formed at both ends of the organic semiconductor difference 306 using an ink jet head, thereby forming the source electrode 308 and the drain electrode 308, respectively. (FIG. 5 (h)).

The average mobility calculated from the Id-Vg curve of the obtained organic thin film transistor element 3 was 0.1 cm ² / Vs, and the off current was 10 pA.

<< Manufacture of organic thin film transistor 4 >>
As shown in FIGS. 1A to 1C, the organic thin film transistor 4 (the present invention) described in the circuit diagram showing a part of the display device of the present invention is manufactured.

  In the manufacture of the organic thin film transistor 4 (the present invention), the high surface energy regions 101 and 102 shown in FIG. 1A are provided.

  Here, the manufacturing process of the organic thin-film transistor 4 which is a preferable embodiment of this invention is demonstrated using FIG.

  An electrode ink containing silver nanoparticles was patterned on the glass substrate 401 using an jet head to form a gate electrode 402. (FIGS. 6A and 6B).

Next, a polysilazane toluene solution was spin-coated and heat-treated to form a SiO ₂ thin film, which was used as the gate insulating layer 403. (FIG. 6C).

The surface of this SiO ₂ was covered with a SAM film of octyltrichlorosilane (OTS), the surface was subjected to a hydrophobic treatment (FIG. 6 (d)), and then irradiated with a UV lamp (254 nm) through a mask. The SAM film was removed, and an exposed portion 405 was formed. (FIG. 6 (e)).

  Next, a PEDOTPSS aqueous solution was discharged onto the substrate from directly above the center of the channel region. The PEDOTPSS aqueous solution was formed only in a region having a relatively high surface energy (UV exposure portion) to form a source electrode 406 and a drain electrode 407, respectively. (FIG. 6 (g)).

  As a result, irregularities were formed in which the channel portion was concave and the source electrode 406 and the drain electrode 407 were convex.

  Next, a 1% by weight toluene solution of the organic semiconductor material (1) is discharged to the center of the two channels as shown in FIG. 1B, and the organic semiconductor material ( 1) was supplied, and the organic semiconductor layer 409 (in FIG. 1C, the organic semiconductor layer 111) was formed by solvent volatilization. (FIG. 6 (h)).

The average mobility calculated from the Id-Vg curve of the obtained organic thin film transistor element 4 was 0.1 cm ² / Vs, and the off current was 10 pA.

It is the schematic which shows a part of manufacturing process of the display apparatus of this invention. It is a general | schematic fragmentary enlarged view of the organic electroluminescent display which is a display apparatus of this invention. It is a schematic diagram which shows the layer structural example of the organic thin-film transistor of this invention. It is a figure explaining the method of this invention which manufactures a thin-film transistor. It is a figure explaining the method of this invention which manufactures a thin-film transistor. It is a figure explaining the method of this invention which manufactures a thin-film transistor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic-semiconductor film 2 Source electrode 3 Drain electrode 4 Gate electrode 5 Gate insulating layer 6 Base | substrate 100 Display apparatus 101 High energy surface area 102 Low surface energy area in a pixel area 103 Scan line 106 Organic EL element 108 Feed line 109 Ground 110 Inkjet liquid Drop 111 Organic semiconductor layer T1 Switching thin film transistor T2 Drive thin film transistor

Claims (7)

In the method of manufacturing an organic thin film transistor, the method includes forming a conductive layer, an insulating layer, and an organic semiconductor layer on a substrate by an inkjet process.
When forming at least one layer of the conductive layer, the insulating layer, and the organic semiconductor layer, the method includes a step of forming a plurality of separated thin films on the substrate by one inkjet discharge. A method for manufacturing an organic thin film transistor. The method for producing an organic thin film transistor according to claim 1, wherein 2 to 4 organic semiconductor layers separated by one inkjet discharge are formed on the substrate. The method for producing an organic thin film transistor according to claim 1, wherein regions having different surface energies are provided on the substrate. The method for producing an organic thin film transistor according to claim 1 or 2, wherein the surface of the substrate has irregularities. The method for producing an organic thin film transistor according to any one of claims 1 to 4, wherein the organic semiconductor layer contains a low-molecular organic semiconductor material. An organic thin film transistor element manufactured using the method for manufacturing an organic thin film transistor according to claim 1. A display device comprising the organic thin film transistor element according to claim 6.

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