JP5949815B2 - Organic thin film transistor - Google Patents

Description

  The present invention relates to an organic thin film transistor.

  With the widespread use of information terminals, there is an increasing need for flat panel displays as computer displays. In addition, with the progress of computerization, the information provided by paper media has been digitized and provided more and more. As a mobile display medium that is thin, light and easy to carry, electronic paper or There is a growing need for digital paper.

  In general, in a flat panel display device, a display medium is formed using an element utilizing liquid crystal, an organic electroluminescence element (hereinafter also referred to as organic EL), electrophoresis, or the like. In such a display medium, a technique using an active drive element formed of a thin film transistor (TFT) as an image drive element is becoming mainstream in order to ensure uniformity of screen brightness, screen rewrite speed, and the like.

  Here, the TFT element is usually a semiconductor thin film such as a-Si (amorphous silicon) or p-Si (polysilicon) or a metal thin film such as a source electrode, a drain electrode, or a gate electrode on a glass substrate. It is manufactured by forming sequentially. The manufacture of flat panel displays using TFTs usually requires high-precision photolithographic processes in addition to the vacuum system equipment such as CVD and sputtering and the thin film forming process that requires a high-temperature treatment process. The load is very large, and the cost of those displays has become enormous with the recent needs for larger displays.

  In recent years, research and development of organic TFT elements using organic semiconductor materials has been actively promoted as a technique to compensate for the disadvantages of conventional TFT elements.

  Since the organic TFT element can be manufactured by a low temperature process, it is said that a light and hard resin substrate can be used, and a flexible display using a resin film as a support can be realized.

  By using an organic semiconductor material that can be manufactured by a wet process such as printing or coating under atmospheric pressure, a display with excellent productivity and a very low cost can be realized. Various organic thin film transistors using organic semiconductors have been proposed, and it is generally known that they can be produced by a simple method by printing or an ink jet method.

  However, organic semiconductor materials for realizing such TFT elements have been studied so far such as acenes such as pentacene and tetracene (see, for example, Patent Document 1), phthalocyanines including lead phthalocyanine, perylene, and the like. Low molecular weight compounds such as tetracarboxylic acid derivatives (see, for example, Patent Document 2), aromatic oligomers typically represented by thiophene hexamers called α-thienyl or sexithiophene (for example, see Patent Document 3), and further. Is a limited type of compounds such as conjugated polymers such as polythiophene, polythienylene vinylene and poly-p-phenylene vinylene, and development of organic semiconductor compositions using new charge transport materials exhibiting high carrier mobility Was long-awaited.

  In addition, a technique using a liquid crystalline polymer compound as an organic semiconductor material having a repeating unit of two or three condensed rings composed of a 5-membered heterocyclic ring and an aromatic ring which may have a substituent (see, for example, Patent Document 4) ), An anthradithiophene which may have a substituent, 2,8-dialkylanthradithiophene (see, for example, Patent Document 5), and a ladder polymer in which a benzene ring and an N-alkylpyrrole ring are alternately condensed. As is known, all have low carrier mobility, and the formed organic semiconductor film has a problem in storage stability with time.

JP-A-5-55568 JP-A-4-167561 JP-A-8-264805 JP 2004-43544 A JP-A-11-195790

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic thin film transistor that is excellent in transistor characteristics and excellent in stability over time even in the air or at high temperature and high humidity. .

  The above object of the present invention is achieved by the following configurations.

1.
The compound represented by any one of the following general formulas (a) to (g) is contained in the organic semiconductor layer, and the mobility immediately after the production is 0.01 (cm ² / V · s) or more, Organic thin film transistor.

(Wherein X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , and R ₃ and R ₄ are hydrogen atoms or substituted. X represents a different group, and the aromatic condensed ring may have an alkyl group or a substituent having an alkyl group.)

2.
2. The organic thin film transistor according to 1 above, wherein the compound is represented by the following general formula ( g ).
General formula ( g )

(Wherein X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , and R ₃ and R ₄ are hydrogen atoms or substituted. X represents a different group, and the aromatic condensed ring may have an alkyl group or a substituent having an alkyl group.)

3 .
3. The organic thin film transistor according to 1 or 2 , wherein at least one X is represented by S or Se.

4).
_3. The organic thin film transistor according to 1 or 2 above, wherein at least one X is represented by N (R ₃ ).

5.
The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 5 or more, 5. The organic thin film transistor according to any one of 4 above.

6).
The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 12 or more, 5. The organic thin film transistor according to any one of 5 above.

7).
The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 18 or more, The organic thin film transistor according to any one of 6 .

8).
Any one of 1 to 7 above, wherein the aromatic condensed ring has a substituent selected from an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 18 or more. An organic thin film transistor according to claim 1.

9.
The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 18 or more, The organic thin-film transistor in any one of 8 .

10.
The organic thin film transistor according to any one of claims 1 to 9, wherein the organic semiconductor layer, characterized in that it is formed by vapor deposition or coating.

11.
The organic semiconductor layer is formed by coating using a solution obtained by dissolving at least 0.1% of the organic semiconductor material comprising the compound having an alkyl group or a substituent having an alkyl group. 10. The organic thin film transistor according to 10 .

  According to the present invention, an organic thin film transistor (hereinafter also referred to as TFT) having excellent transistor characteristics and excellent temporal stability even in the air or at high temperature and high humidity could be provided.

It is a figure which shows the structural example of the organic thin-film transistor of this invention. It is an example of the schematic equivalent circuit schematic of the organic thin-film transistor of this invention.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

《Organic semiconductor material》
The organic semiconductor material of the present invention has, as a partial structure, at least three or more aromatic condensed rings in which an aromatic heterocyclic ring composed of at least one benzene ring and at least two adjacent rings is condensed. It is a compound which may have an alkyl group or a substituent having an alkyl group in the condensed group ring. Here, at least three or more aromatic condensed rings in which an aromatic heterocyclic ring composed of at least one benzene ring and at least two adjacent rings are condensed are specifically represented by the following general formula (1). Is done.

In the general formula (1), X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , and R ₃ and R ₄ are hydrogen atoms. Or, although it represents a substituent, each X may be different. Z represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and n represents an integer of 0 to 7. When the total of n is 2 or more, the plurality of Z may be the same or different.

When X is N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , the substituent represented by R ₃ or R ₄ is not particularly limited as long as it is a substitutable group. For example, an alkyl group, a cycloalkyl group, an aryl group, an aromatic heterocyclic group, a heterocyclic group, an alkoxyl group, a cycloalkoxyl group, an aryloxy group, an alkylthio group, a cycloalkylthio group, an arylthio group and the like are preferably substituted. As a group. X is preferably S or Se, and more preferably S. Each X may be different.

  Examples of the aromatic hydrocarbon ring represented by Z include benzene, naphthalene, anthracene, azulene, fluorene, phenanthrene, indene, and pyrene. Examples of the aromatic heterocyclic ring include thiophene, furan, pyrrole, Examples include pyridine, pyridazine, pyrimidine, pyrazine, triazine, imidazole, pyrazole, thiazole, benzimidazole, benzoxazole, and quinazole.

  The compound which has the partial structure represented by the general formula (1) and may have an alkyl group or a substituent having an alkyl group in the partial structure is further represented by the following general formula (2). .

In General formula (2), R < ₁ >, R < ₂ > represents the substituent which has a hydrogen atom, an alkyl group, or an alkyl group. m1 and m2 represent an integer of 0 to 4. However, m1 + m2 is an integer of 1 or more. When m1 is 2 or more, the plurality of R ₁ may be the same or different. When m2 is 2 or more, the plurality of R ₂ may be the same or different. A ₁ and A ₂ represent a hydrogen atom or a substituent, and m3 and m4 represent an integer of 0 to 4. X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , but may be different from each other. R ₃ and R ₄ represent a hydrogen atom or a substituent, Z represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and n represents an integer of 0 to 7. When n is 2 or more, the plurality of Z may be the same or different.

Examples of the alkyl group represented by R ₁ and R ₂ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a tridecyl group, and a tetradecyl group. , Pentadecyl group, cyclopentyl group, cyclohexyl group and the like.

Examples of the substituent having an alkyl group represented by R ₁ or R ₂ include a silylethynyl group substituted with an alkyl group, an aryl group substituted with an alkyl group (for example, a phenyl group, a biphenyl group, a naphthyl group), An aromatic heterocyclic group substituted with an alkyl group (for example, furyl group, thienyl group, pyridyl group, imidazolyl group, etc.), alkoxyl group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, Octyloxy groups, dodecyloxy groups, etc.), cycloalkoxyl groups (eg, cyclopentyloxy groups, cyclohexyloxy groups, etc.), aryloxy groups substituted with alkyl groups (eg, phenoxy groups, naphthyloxy groups, etc.), alkylthio groups (eg, , Methylthio group, ethylthio group, propylthio group, pentylthio Hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group substituted by alkyl group (for example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group ( For example, a methyloxycarbonyl group, an ethyloxycarbonyl group, a butyloxycarbonyl group, an octyloxycarbonyl group, a dodecyloxycarbonyl group, etc.), an aryloxycarbonyl group substituted with an alkyl group (for example, a phenyloxycarbonyl group, a naphthyloxycarbonyl group) Etc.), alkylsulfamoyl group, alkylcarbonyl group, alkylcarbonyloxy group, alkylcarbonylamino group, alkylcarbamoyl group, alkylureido group, alkylsulfinyl Group, alkylsulfonyl group, arylsulfonyl group substituted by alkyl group, alkylamino group, fluoroalkyl group, trifluoroalkyl group, pentafluoroalkyl group, alkylsilyl group and the like, but the present invention is limited to these. It is not a thing.

The substituent represented by A ₁ or A ₂ is not particularly limited as long as it is a substitutable group. For example, an aryl group, an aromatic heterocyclic group, an aryloxy group, an arylthio group, an aryloxycarbonyl group, A halogen atom, a cyano group, etc. are mentioned. Among these, an aryl group is preferable, and a phenyl group is more preferable.

R ₁ and R ₂ are preferably an alkyl group, an alkylsilylethynyl group, an aryl group substituted with an alkyl group, an aryl group substituted with an alkylsilylethynyl group, a trialkylsilylethynyl group, a trialkylsilylethynyl group Is more preferably a substituted phenyl group.

  X is synonymous with X in the general formula (1), and Z is also synonymous with Z in the general formula (1).

In the following general formula (3), R ₁ , R ₂ , A ₁ , A ₂ , X, and Z have the same meanings as those in general formula (2). l represents an integer of 1 to 5. l is preferably an integer of 1 to 4.

  The organic semiconductor material of the present invention is preferably a compound represented by the general formula (2) or (3).

Examples of these include the following compounds, but the present invention is not limited thereto.

《Organic solvent》
The organic solvent according to the present invention is not particularly limited as long as the organic semiconductor material of the present invention can be dissolved to prepare a solution with an appropriate concentration, but a chain ether solvent such as diethyl ether or diisopropyl ether, Cyclic ether solvents such as tetrahydrofuran and dioxane, ketone solvents such as acetone and methyl ethyl ketone, aliphatic halogenated hydrocarbon solvents such as chloroform and 1,2-dichloroethane, toluene, o-dichlorobenzene, nitrobenzene, m-cresol, etc. And aromatic hydrocarbon solvents such as hexane and cyclohexane, N-methylpyrrolidone, carbon disulfide, and the like.

  The organic solvent according to the present invention is preferably an aromatic hydrocarbon, an aromatic halogenated hydrocarbon, an aliphatic hydrocarbon or an aliphatic halogenated hydrocarbon, more preferably an aromatic hydrocarbon or an aromatic halogenated hydrocarbon.

  Examples of the aromatic hydrocarbon organic solvent include toluene, xylene, mesitylene, methylnaphthalene, and the like, but the present invention is not limited thereto.

  Examples of the organic solvent for the aromatic halogenated hydrocarbon include chlorobenzene, bromobenzene, iodobenzene, o-dichlorobenzene, m-dichlorobenzene, o-dibromobenzene, m-dibromobenzene, o-diiodobenzene, m- Diiodobenzene, chlorotoluene, bromotoluene, iodotoluene, dichlorotoluene, dibromotoluene, difluorotoluene, chloroxylene, bromoxylene, iodoxylene, chloroethylbenzene, bromoethylbenzene, iodoethylbenzene, dichloroethylbenzene, dibromoethylbenzene, chlorocyclopentadiene, Although chlorocyclopentadiene etc. can be mentioned, this invention is not limited to these.

  Examples of the aliphatic hydrocarbon organic solvent include octane, 4-methylheptane, 2-methylheptane, 3-methylheptane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane, 3-ethylhexane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, 2,3,3- Trimethylpentane, 2,3,4-trimethylpentane, 2-methyl-3-ethylpentane, 3-methyl-3-ethylpentane, decane, 2,2,3,3-tetramethylhexane, 2,2,5, 5-tetramethylhexane, 3,3,5-trimethylheptane, nonane, 2,2,5-trimethylhexane, 4-ethylheptane, 2,3-di Tilheptane, 2-methyloctane, dodecane, hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, heptane, 2-methylhexane, 3-methylhexane, 2,2 -Chain aliphatic hydrocarbons such as dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2,2,3-trimethylbutane, cyclohexane, cyclo Examples include cycloaliphatic hydrocarbons such as pentane, methylcyclohexane, methylcyclopentane, p-menthane, decalin, and cyclohexylbenzene, but the present invention is not limited thereto. As the aliphatic hydrocarbon used in the present invention, a cyclic aliphatic hydrocarbon is preferable.

  Examples of the organic solvent for the aliphatic halogenated hydrocarbon include chloroform, bromoform, dichloromethane, dichloroethane, trichloroethane, difluoroethane, fluorochloroethane, chloropropane, dichloropropane, chloropentane, and chlorohexane. It is not limited to these.

  These organic solvents used in the present invention may be used alone or in combination of two or more.

《Organic thin film transistor》
The organic thin film transistor has a source electrode and a drain electrode connected by an organic semiconductor channel (active layer) on a support, a top gate type having a gate electrode on the support, and a gate electrode on the support. 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 channel through a gate insulating layer. The organic thin film transistor of the present invention may be either the top gate type or the bottom gate type, and the form is not limited.

  In the present invention, the method for forming the organic semiconductor layer is typified by a deposition process formed by vacuum deposition, a coating method such as cast coating, dip coating, or spin coating, or a printing method such as inkjet printing or screen printing. Although a solution process etc. are mentioned, in this invention, it is preferable to form an organic-semiconductor film | membrane on a board | substrate by a solution process. Among these, a method of applying an organic semiconductor solution onto a substrate heated to room temperature or above by drop cast coating is more preferable for improving the orientation of the organic semiconductor or promoting the growth of the crystalline film.

  Further, in order to make the present invention more effective, the organic semiconductor film is protected by using a known inorganic material or organic polymer material or the like on the organic semiconductor layer or the organic thin film transistor itself composed of necessary components. It is preferable to form a protective film (sealing film). As a method for forming the protective film, a known technique as described in JP-T-2003-525521, JP-A-2004-506985, JP-A-2002-314093, and JP-A-2003-258164 is applied. be able to. In addition, an insulating film used as a gate insulating layer, which will be described later, can be applied as a protective film, and a support described later can be further attached onto an organic thin film transistor prepared on the support, or laminated with a polymer sheet. A protective film may be formed by.

  A substrate used in the present invention (for example, an insulating film such as a thermal oxide film formed on a silicon substrate) may be subjected to surface treatment in advance. As the surface treatment, it is more preferable to form a self-aligned thin film on the substrate as in the case of treatment with a silane coupling agent. Examples of the silane coupling agent include octadecyltrichlorosilane, nonyltrichlorosilane, octyltrichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, n-butyltrichlorosilane, i-butyltrichlorosilane, ethyltrichlorosilane, methyltrichlorosilane, Known trimethylchlorosilane, hexamethyldisilazane, 4-phenylbutyltrichlorosilane, 3-phenoxypropyltrichlorosilane, phenyltrichlorosilane, cyclohexyltrichlorosilane, heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane Although a material is mentioned as a preferable example, this invention is not restricted to these.

  As a surface treatment method using a silane coupling agent, a known method as disclosed in JP-A Nos. 2004-327857, 2005-32774, and 2005-158765 is applied. Can do. For example, a vapor phase method such as a CVD method, a liquid phase method such as a spin coating method or a dip coating method, and a printing method such as a screen printing method, a micromold method, a micro contact method, and an ink jet method can be applied.

  Further, before the treatment with the silane coupling agent, it is possible to perform a hydrophilic treatment (treatment for forming a hydroxyl group-OH on the surface) such as oxygen plasma treatment or UV ozone treatment on the substrate surface. It is generally known that it is preferable for forming an organized monolayer, and is also described in the above-mentioned patent documents. Furthermore, generally well-known orientation processing such as rubbing may be performed.

  Although there is no restriction | limiting in particular as the film thickness of the organic-semiconductor layer formed in this invention, The characteristic of the obtained organic thin-film transistor (TFT) is largely influenced greatly by the film-thickness of an organic-semiconductor layer, The film thickness Although it varies depending on the organic semiconductor material, it is generally 1 μm or less, preferably 10 to 300 nm.

  The organic semiconductor layer includes, for example, materials having functional groups such as acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, benzoquinone derivatives, tetracyanoethylene and tetracyanoquinodimethane, and their A material that serves as an acceptor for accepting electrons such as a derivative, a material having a functional group such as an amino group, a triphenyl group, an alkyl group, a hydroxyl group, an alkoxy group, or a phenyl group, a substituted amine such as phenylenediamine, It contains so-called doping treatment by containing a material that serves as a donor as an electron donor, such as anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and derivatives thereof, and tetrathiafulvalene and derivatives thereof. You may give it.

  The doping means introducing an electron-donating molecule (acceptor) or an electron-donating molecule (donor) into the thin film as a dopant. Therefore, the doped thin film is a thin film containing the organic semiconductor material of the present invention and a dopant. As the dopant used in the present invention, either an acceptor or a donor can be used. A known material can be used as the acceptor or donor, and a known process can be used for introduction thereof.

  Taking the bottom gate type organic thin film transistor which is one of the preferred embodiments of the present invention as an example, the organic thin film transistor is optimally arranged with a gate electrode, a gate insulating film, an active layer, a source electrode and a drain electrode on a support. It is constituted by being done.

  Therefore, for example, after forming a gate electrode on a support, a gate insulating film is formed, and after forming an active layer (organic semiconductor layer (thin film)) on the gate insulating film by the above method, a source, The organic thin film transistor of the present invention is formed by forming the drain electrode.

  Further, for example, after forming the gate insulating film, a source / drain electrode pattern may be formed on the gate insulating film, and an organic semiconductor channel may be formed between the source / drain electrodes by patterning.

  As described above, the gate electrode, the gate insulating film, the active layer (organic semiconductor layer), the source electrode, and the drain electrode are appropriately patterned and optimally arranged on the support, respectively, so that the organic thin film transistor of the present invention is provided. Is obtained.

  Hereinafter, other components constituting the organic thin film transistor other than the active layer (organic semiconductor layer (thin film)) of the organic thin film transistor of the present invention will be described.

  In the present invention, the material for forming the source electrode, the drain electrode and the gate electrode 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-potassium alloy, magnesium / copper mixture, magnesium / silver mixture, magne Um / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture is used, in particular platinum, gold, silver, copper, aluminum, indium, ITO and carbon are preferable. Alternatively, a known conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylenedioxythiophene and polystyrenesulfonic acid, or the like is also preferably used. Especially, a thing with little electrical resistance in a contact surface with an organic-semiconductor layer is preferable.

  As a method of forming an electrode, a method of forming an electrode using a known photolithographic method or a lift-off method with a conductive thin film formed using a method such as vapor deposition or sputtering using the above as a raw material, on a metal foil such as aluminum or copper In addition, there is a method of forming an electrode using a resist by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by ink jetting, or may be formed from a coating film by lithography, laser ablation, or the like. Furthermore, a method of patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  In the present invention, the source and drain electrodes are preferably formed from a fluid electrode material such as a solution or dispersion of the conductive polymer or a conductive fine particle dispersion. For example, conductive fine particles made of metal or the like are used. Preferably, using a dispersion stabilizer made of an organic material, it is dispersed in a dispersion medium that is water, an organic solvent, or a mixture thereof to form a conductive fine particle dispersion such as paste or ink, and this is coated and patterned. It is preferable to form an electrode.

  Examples of conductive fine metal materials (metal fine particles) include platinum, gold, silver, cobalt, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium. Germanium, molybdenum, tungsten, zinc, and the like can be used, and platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, and tungsten having a work function of 4.5 eV or more are particularly preferable.

  As a method for producing such a metal fine particle dispersion, metal ions are reduced in the liquid phase, such as a physical generation method such as gas evaporation method, sputtering method, metal vapor synthesis method, colloid method, coprecipitation method, etc. Examples of the chemical production method for producing metal fine particles include colloidal methods described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, and JP-A-2000-239853. Fine metal particle dispersions produced by the gas evaporation method described in JP-A Nos. 2001-254185, 2001-53028, 2001-35255, 2000-124157, and 2000-123634 It is.

  The average particle diameter of the dispersed metal fine particles is preferably 20 nm or less from the viewpoint of the effect of the present invention.

  In addition, it is preferable to contain a conductive polymer in the metal fine particle dispersion. If the source electrode and the drain electrode are formed by patterning and pressing, heating, etc., ohmic contact with the organic semiconductor layer is possible with the conductive polymer. And can. That is, the effect of the present invention can be further enhanced by interposing a conductive polymer on the surface of the metal fine particles, reducing the contact resistance to the organic semiconductor, and thermally fusing the metal fine particles.

  As the conductive polymer, a known conductive polymer whose conductivity has been improved by doping or the like is preferably used. For example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, polyethylenedioxythiophene and polystyrenesulfonic acid complex Etc. are preferably used.

  The content of the metal fine particles is preferably 0.00001 to 0.1 in terms of mass ratio with respect to the conductive polymer. If this amount is exceeded, fusion of the metal fine particles may be inhibited.

  After forming electrodes with these metal fine particle dispersions, the metal fine particles are thermally fused to form source and drain electrodes. It is also preferable to promote fusion by applying a pressure of about 1 to 50000 Pa, and further about 1000 to 10000 Pa at the time of electrode formation.

  As a method of patterning like an electrode using the metal fine particle dispersion, for example, there is a patterning method by a printing method using the metal fine particle dispersion as an ink. In addition, there is a method of patterning by an ink jet method, which is a method of discharging a metal fine particle dispersion from an ink jet head and patterning the dispersion of metal fine particles. Patterning can be performed by a known method such as an on-demand type (registered trademark) type or a continuous jet type ink jet method such as an electrostatic suction type.

  As a method of heating or pressurizing, a known method including a method used for a heating laminator or the like can be used.

  Various insulating films can be used as the gate insulating layer, and an inorganic oxide film having a high relative dielectric constant is particularly preferable.

  Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and trioxide yttrium. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  The film formation method includes vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, atmospheric pressure plasma method (atmospheric pressure plasma CVD method). And wet processes such as a dip coating method, a casting method, a reel coating method, a bar coating method, a coating method such as a die coating method, and a patterning method such as printing or ink jetting, and can be used depending on the material.

  The wet process is a method of applying and drying a liquid in which fine particles of inorganic oxide are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required, or an oxide precursor, for example, A so-called sol-gel method in which a solution of an alkoxide body is applied and dried is used.

  Of these, the atmospheric pressure plasma method is preferred.

  The method for forming an insulating film by the atmospheric pressure plasma method is a process in which a thin film is formed on a substrate by discharging at atmospheric pressure or a pressure in the vicinity of atmospheric pressure to excite a reactive gas to form a thin film on a substrate. 11-61406, 11-133205, JP-A 2000-121804, 2000-147209, and 2000-185362. Thereby, a highly functional thin film can be formed with high productivity.

  The organic compound film can be formed by using polyimide, polyamide, polyester, polyacrylate, photo radical polymerization system, photo cation polymerization system photo curable resin, copolymer containing acrylonitrile component, polyvinyl phenol, polyvinyl alcohol. , Novolak resin, cyanoethyl pullulan, and the like can also be used.

  The wet process is preferred as the method for forming the organic compound film.

  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.

  Moreover, a support body is comprised with glass or a flexible resin-made sheet | seat, for example, a plastic film can be used as a sheet | seat. 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. Thus, by using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, flexibility can be improved and resistance to impact can be improved.

  In particular, when a plastic film is used as a support, for example, a gas barrier layer as disclosed in Japanese Patent Application Laid-Open No. 2004-134694 is used to protect organic thin film transistor elements from oxygen, liquid (water), light, and the like. It is preferable to further have a barrier layer having at least one layer or a multilayer structure.

  FIG. 1 shows a structural example of an organic thin film transistor (TFT) of the present invention.

  In FIG. 1A, gold or the like is patterned on the support 6 by vapor deposition using a mask, or a layer containing metal fine particles is formed, and then the layer containing metal fine particles is heated and pressurized. A source electrode 2 and a drain electrode 3 are formed by fusing, etc., an organic semiconductor material layer 1 is formed between the source and drain electrodes, a gate insulating layer 5 is formed thereon, and a gate electrode is further formed thereon. 4 is formed to form an organic TFT.

  FIGS. 1B and 1C show other configuration examples of the top gate type organic thin film transistor.

  1D to 1F show configuration examples of bottom-gate organic TFTs. In FIG. 1D, after forming the gate electrode 4 on the support 6, the gate insulating layer 5 is formed, the source electrode 2 and the drain electrode 3 are formed thereon, and the gate between the source and drain electrodes is formed. A bottom gate type organic TFT is formed by forming an organic semiconductor material layer 1 on an insulating layer. Similarly, other configuration examples are shown in FIGS. In particular, in FIG. 1 (f), after forming the gate electrode 4 on the support 6, the gate insulating layer 5 is formed, the organic semiconductor material layer 1 is formed thereon, and then the source electrode 2 and the drain electrode 3 are further formed. It is formed to form an organic TFT.

  FIG. 2 is an example of a schematic equivalent circuit diagram of a TFT sheet configured like an output element such as a liquid crystal or an electrophoretic element using the organic thin film transistor.

  The TFT sheet 10 has a large number of organic TFTs 11 arranged in a matrix. 7 is a gate bus line of each organic TFT 11, and 8 is a source bus line of each organic TFT 11. For example, an output element 12 such as a liquid crystal or an electrophoretic element is connected to the source electrode of each organic TFT 11 to constitute a pixel in the display device. The pixel electrode may be used as an input electrode of the photosensor. In the illustrated example, a liquid crystal as an output element is shown by an equivalent circuit composed of a resistor and a capacitor. 13 is a storage capacitor, 14 is a vertical drive circuit, and 15 is a horizontal drive circuit.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Production of organic thin film transistor elements >>
An organic thin film transistor element (hereinafter referred to as a TFT element) 1 having the layer configuration shown in FIG.

  First, a thermal oxide film having a thickness of 2000 mm was formed on a Si wafer having a specific resistance of 0.02 Ω / cm as the gate electrode 4 to form the gate insulating layer 5. Hereinafter, this is referred to as a substrate.

  While heating the substrate on a hot plate in a nitrogen atmosphere, a 0.1% toluene solution of the comparative compound (C-1) was dropped onto the substrate to form a coating film (thickness 50 nm). Furthermore, gold was deposited on the surface of this film using a mask to form source and drain electrodes. A TFT element 1 having a width of 100 μm, a thickness of 200 nm, a channel width W = 3 mm, and a channel length L = 20 μm was prepared.

  A TFT element 2 was produced in the same manner as the TFT element 1 except that the comparative compound (C-1) was replaced with the comparative compound (C-2) (pentacene, a commercially available reagent manufactured by Aldrich). did.

  Further, TFT elements 3 to 15 were produced in the same manner as the TFT element 1 except that the comparative compound (C-1) was replaced with the exemplary compounds according to the present invention shown in Table 1.

<< Evaluation of TFT element >>
(Transistor characteristics)
The TFT elements 1 to 15 fabricated as described above exhibited the operating characteristics of p-channel enhancement type FETs. For each TFT element, the carrier mobility is obtained from the saturation region of the IV characteristic, and further the ON / OFF ratio (the drain bias value is 40 V, the drain current value ratio when the gate bias is -50 V and 0 V) is obtained. The results are shown in Table 1. Also, when left for 1 month under conditions of 25 ° C. and humidity 45%, and when left for 1 month under conditions of 50 ° C. and humidity 60%, the carrier mobility and the ON / OFF ratio were also evaluated. It is shown in Table 1.

  From Table 1, the organic thin film transistor using the organic semiconductor material of the present invention for the organic semiconductor layer has higher mobility, superior solution process suitability, and the effect of suppressing deterioration with time in the atmosphere, particularly high temperature, It was found that the effect of suppressing deterioration with time under high humidity was great. On the other hand, when the comparative compound (C-1) or (C-2) is used for the organic semiconductor layer, it is difficult to form a uniform crystalline thin film by a solution process, and desirable transistor characteristics can be obtained even immediately after the device is formed. I couldn't.

1 Organic Semiconductor Layer 2 Source Electrode 3 Drain Electrode 4 Gate Electrode 5 Insulating Layer 6 Support 7 Gate Bus Line 8 Source Bus Line 10 TFT Sheet 11 Organic TFT
12 Output element 13 Storage capacitor 14 Vertical drive circuit 15 Horizontal drive circuit

Claims (11)

The compound represented by any one of the following general formulas (a) to (g) is contained in the organic semiconductor layer, and the mobility immediately after the production is 0.01 (cm ² / V · s) or more, Organic thin film transistor.

(Wherein X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , and R ₃ and R ₄ are hydrogen atoms or substituted. X represents a different group, and the aromatic condensed ring may have an alkyl group or a substituent having an alkyl group.) The compounds, organic thin film transistor according to claim 1, characterized by being represented by the following general formula (g).
General formula ( g )

(Wherein X represents S, Se, SO ₂ , O, N (R ₃ ), Si (R ₃ ) R ₄ or C (R ₃ ) R ₄ , and R ₃ and R ₄ are hydrogen atoms or substituted. X represents a different group, and the aromatic condensed ring may have an alkyl group or a substituent having an alkyl group.) At least one of the X is an organic thin film transistor according to claim 1 or 2, characterized by being represented by S or Se. At least one of the X is an organic thin film transistor according to claim 1 or 2, characterized by being represented by N (R _3). The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 5 or more. the organic thin film transistor according to any one of 1-4. The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 12 or more. the organic thin film transistor according to any one of 1-5. The aromatic condensed ring has a substituent selected from an alkyl group, an alkylsilylethynyl group or an alkylarylethynyl group, and the total carbon number of all the substituents is 18 or more. the organic thin film transistor according to any one of 1-6. Said aromatic condensed ring, alkylsilyl ethynyl group or an optionally substituted group selected from alkyl aryl ethynyl group, according to claim 1-7, characterized in that the total number of carbon atoms of all the substituents is 18 or more The organic thin-film transistor in any one. The organic thin film transistor according to any one of claims 1-8, characterized in that it comprises a said aromatic fused ring, an alkyl group or an alkyl silyl ethynyl group. The organic thin film transistor according to any one of claims 1 to 9, wherein the organic semiconductor layer, characterized in that it is formed by vapor deposition or coating. The organic semiconductor layer is formed by coating using a solution obtained by dissolving at least 0.1% of the organic semiconductor material comprising the compound having an alkyl group or a substituent having an alkyl group. 10. The organic thin film transistor according to 10 .

Images