JPWO2006129718A1 - Organic thin film transistor - Google Patents

Abstract

Provided is an organic thin film transistor capable of suppressing leakage current in a gate insulating film, obtaining a high insulating film capacity, hardly generating hysteresis, and operating at a low gate voltage. (A) an organic semiconductor film, (B) a gate electrode, (C) a source electrode, (D) a drain electrode, and (E) a functional group having an unshared electron pair on the substrate, and π electrons in the molecular structure An organic thin film transistor having a gate insulating film comprising an organic polymer compound having no bond, preferably an alicyclic olefin polymer having no functional group having an unshared electron pair and having no π-electron bond in the molecular structure.

Description

  The present invention relates to an organic thin film transistor, and more particularly to an organic thin film transistor capable of suppressing leakage current in a gate insulating film, obtaining a high insulating film capacity, hardly generating hysteresis, and operating at a low gate voltage.

  The organic thin film transistor has, for example, a structure in which a substrate, a gate electrode, a gate insulating film, a source electrode, a drain electrode, an organic semiconductor film, and a protective film are stacked in this order. The organic thin film transistor can be obtained by a low-cost manufacturing process under normal temperature and normal pressure, such as a printing method, and has good compatibility with a flexible substrate. Taking advantage of its characteristics, organic thin film transistors can be applied to image drive elements of flat panel displays such as liquid crystal display devices, organic electroluminescence display devices, electrophoretic display devices, sheet displays, electronic paper, electronic price tags, electronic tags, etc. Application to integrated circuit technology of electronic devices such as electronic tags and biosensors is expected.

  In order to improve the expected characteristics of the organic thin film transistor, it is considered to increase the mobility of the organic semiconductor in the channel layer. It is known that the mobility of the organic semiconductor varies depending on the material of the gate insulating film (Patent Document 1 and Patent Document 2), and materials for the organic gate insulating film have been actively developed.

  For example, in the organic thin film transistors disclosed in Patent Document 1 and Patent Document 2, in order to obtain a large drain current, it is better that the electric capacity per unit area of the gate insulating film is large. A highly insulating polymer (such as cyanoethyl pullulan) having a relative dielectric constant is used for the gate insulating film. This cyanoethyl pullulan has a relative dielectric constant of 18.5.

  Patent Document 3 proposes polyacrylonitrile, which is a polymer having a cyano group, as an organic gate insulating material. The relative dielectric constant of polyacrylonitrile is 4.5. Furthermore, Patent Document 3 proposes polymers such as polyimide, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyparaxylene, polyvinylidene fluoride, polyvinylphenol, pullulan, and parylene as gate insulating films and derivatives thereof. . Patent Document 4 further proposes to use a composite material mixed with a material for increasing the dielectric constant in order to obtain a more effective electric field effect.

  However, unless these organic materials have a large film thickness, a gate leakage current due to a tunnel phenomenon flows through the insulating film, and the insulating property cannot be maintained, which further hinders the application of gate bias. In some cases, a high on / off ratio cannot be obtained. Moreover, hysteresis appeared, there were many carrier traps, and the expression of n-type characteristics was insufficient.

Japanese National Patent Publication No. 5-508745 US Pat. No. 5,347,144 JP 2004-179542 A JP-A-8-191162

  An object of the present invention is to provide an organic thin film transistor which can suppress a leakage current in a gate insulating film, obtain a high insulating film capacity, hardly cause hysteresis, and can operate at a low gate voltage.

  As a result of various studies on conventionally used organic gate insulating film materials, the present inventors have found that functional group electron pairs existing in the molecular structure and π electrons such as a benzene ring affect the leakage current. As a result of recognizing and further studying, when a gate insulating film is formed using an organic polymer compound that does not have a functional group having an unshared electron pair and does not have a π-electron bond in the molecular structure, the insulating film has a high quality pin. It has been found that an organic thin film transistor capable of operating at a low gate voltage can be obtained because the film is difficult to form holes, the leakage current in the gate insulating film is suppressed, the high insulating film capacity is obtained, the hysteresis is hardly generated. The present inventors have completed the present invention based on this finding.

  Thus, according to the present invention, there is no functional group having (A) an organic semiconductor film, (B) a gate electrode, (C) a source electrode, (D) a drain electrode, and (E) an unshared electron pair on the substrate. An organic thin film transistor having a gate insulating film containing an organic polymer compound having no π-electron bond in the molecular structure is provided. Also provided is a gate insulating film comprising an organic polymer compound that does not have a functional group having an unshared electron pair and does not have a π-electron bond in the molecular structure. Furthermore, a display device comprising the organic thin film transistor is provided.

The gate insulating film of the present invention is a stable film in which pinholes are hardly formed even at a thin film thickness, and leakage current can be suppressed. The organic thin film transistor of the present invention having this gate insulating film has a high insulating film capacity and can be operated at a low gate voltage. Furthermore, since hysteresis does not occur, semiconductor characteristics can be expressed with high accuracy.
The organic thin film transistor of the present invention is used as an image driving element for flat panel displays such as liquid crystal display devices, organic EL (= abbreviated notation of electroluminescence) display devices, and electrophoretic display devices, and also as sheet display, electronic paper, electronic price tags, The present invention can be applied to integrated circuit technology of electronic devices such as electronic tags, electronic sensors such as biosensors, gas sensors, and memory elements. In particular, since the organic thin film transistor of the present invention can operate at a low voltage, it is suitable for an image driving element of an organic EL display device.

The figure which shows the example of the top gate type organic thin-film transistor of this invention. The figure which shows the example of the bottom gate type organic thin-film transistor of this invention. The figure which shows the structural example of a well-known typical organic EL element. The figure which shows the structural example for one pixel of the organic electroluminescent display apparatus of this invention. 1 is a diagram showing an example of a circuit of an active matrix type organic EL display device of the present invention. In Example 1, it is a figure which shows the dependence of the spin speed of the thickness of an insulating thin film, and the density | concentration of a solvent. It is a figure which shows the image (image) of the AFM of an insulating thin film in Example 1. FIG. 6 is a diagram showing a current-voltage curve of an MIM structure element of Example 2. FIG. It is a figure which shows the electrical capacitance-frequency curve of the MIM structure element of Example 2. FIG. (A) is a diagram showing the operating characteristics of an organic TFT in which the organic semiconductor film obtained in Example 3 is a pentacene thin film, the gate insulating film is an alicyclic olefin polymer thin film having a thickness of about 260 nm, and the substrate is glass; (B) is a figure which shows the square root of the drain current of (a) as a function of the gate voltage in a saturated state in order to calculate field effect mobility. (A) is a diagram showing the operating characteristics of an organic TFT in which the organic semiconductor film obtained in Example 3 is a pentacene thin film, the gate insulating film is an alicyclic olefin polymer thin film having a thickness of about 450 nm, and the substrate is polyethylene terephthalate. (B) is a figure which shows the square root of the drain current of (a) as a function of the gate voltage in a saturation state, in order to calculate a field effect mobility. It is a figure which shows the hysteresis characteristic in the operating characteristic of organic TFT with which the organic-semiconductor film obtained in Example 3 is a pentacene thin film, a gate insulating film is an alicyclic olefin polymer thin film about 450 nm thick, and a board | substrate is glass.

Explanation of symbols

2, 5: Organic thin film transistor; 4: Capacitor; 6: Organic EL element; 11: Substrate; 11 ': Transparent substrate; 12: Undercoat layer; 14: Drain electrode; 15: Source electrode; 18: Gate electrode; 23: Protective film (sealing film); 54: Lower electrode layer (anode); 55: Upper electrode layer (cathode); 62: Luminescent material layer;

The organic thin film transistor of the present invention has (A) an organic semiconductor film, (B) a gate electrode, (C) a source electrode, (D) a drain electrode, and (E) a gate insulating film on a substrate.
The organic thin film transistor has (A) a source electrode and (D) a drain electrode in contact with an organic semiconductor film, and (B) a top gate type having (B) a gate electrode on the (E) gate insulating film thereon. (B) a gate electrode, and (E) a bottom gate type having (C) a source electrode and (D) a drain electrode connected to each other by (A) an organic semiconductor film via a gate insulating film; It is divided roughly into.

  FIG. 1 shows an example of a top gate type. In the top gate type organic thin film transistor shown in FIG. 1A, an undercoat layer 12 containing a compound selected from a polymer or an inorganic oxide and an inorganic nitride is provided on a substrate 11, and the organic layer is in contact with the undercoat layer 12. A semiconductor film 16, a drain electrode 14, and a source electrode 15 are provided, and a gate electrode 18 is provided on the organic semiconductor film 16 through a gate insulating film 17. A protective film (sealing film) 23 is provided as the outermost layer. FIG. 1B shows a configuration in which the order of stacking the drain electrode and the source electrode and the organic semiconductor film is changed.

  FIG. 2 shows an example of a bottom gate type. In the bottom gate type organic thin film transistor shown in FIG. 2A, the substrate 11 has an undercoat layer 12 containing a compound selected from a polymer or an inorganic oxide and an inorganic nitride, and is in contact with the undercoat layer 12. An organic semiconductor film 16 is provided through a gate electrode 18 and a gate insulating film 17. Further, a drain electrode 14 and a source electrode 15 are provided in contact with the organic semiconductor film 16. FIG. 2B shows a configuration in which the order of stacking the drain electrode and the source electrode and the organic semiconductor film is changed.

  The organic semiconductor film (A) constituting the organic thin film transistor of the present invention is formed of an organic semiconductor material. Examples of the organic semiconductor material include π-conjugated materials. Examples of the π-conjugated material include polypyrroles such as polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), and poly (3,4-disubstituted pyrrole), polythiophene, and poly (3-substituted thiophene). , Polythiophenes such as poly (3,4-disubstituted thiophene) and polybenzothiophene, polyisothianaphthenes such as polyisothianaphthene, polychenylene vinylenes such as polychenylene vinylene, poly (p-phenylene vinylene) Poly (p-phenylene vinylene) s such as polyaniline, polyaniline, poly (N-substituted aniline), poly (3-substituted aniline), polyaniline such as poly (2,3-substituted aniline), polyacetylenes such as polyacetylene, Polydiacetylenes such as polydiacetylene, and polyazule such as polyazulene , Polypyrenes such as polypyrene, polycarbazoles such as polycarbazole and poly (N-substituted carbazole), polyselenophenes such as polyselenophene, polyfurans such as polyfuran and polybenzofuran, poly (p-phenylene), etc. Poly (p-phenylene) s, polyindoles such as polyindole, polypyridazines such as polypyridazine, naphthacene, pentacene, hexacene, heptacene, dibenzopentacene, tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene, coronene , Terylene, Ovalene, Quoterylene, Circaanthracene and other polyacenes and derivatives obtained by substituting a part of carbon of the polyacenes with atoms such as N, S and O, and functional groups such as carbonyl groups (triphenodioxazine, Examples thereof include polymers such as riphenodithiazine, hexacene-6,15-quinone, etc.), polyvinyl carbazole, polyphenylene sulfide, polyvinylene sulfide, and polycyclic condensates described in JP-A No. 11-195790.

  In addition, α-sexithiophene, α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-, which are the same repeating units as those polymers, for example, which are thiophene hexamers Examples thereof include oligomers such as bis (3-butoxypropyl) -α-sexithiophene and styrylbenzene derivatives.

Furthermore, metal phthalocyanines such as copper phthalocyanine and fluorine-substituted copper phthalocyanine described in JP-A-11-251601; naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4-trifluoromethyl) Benzyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (1H, 1H-perfluorooctyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (1H, 1H-perfluorobutyl) naphthalene 1,4,5,8-tetracarboxylic acid diimide and N, N′-dioctylnaphthalene 1,4,5,8-tetracarboxylic acid diimide, naphthalene 2,3,6,7 -Naphthalene tetracarboxylic acid diimides such as tetracarboxylic acid diimide and anthracene 2,3,6,7-te Condensed ring tetracarboxylic acid diimides such as anthracene tetracarboxylic acid diimides such as tracarboxylic acid diimide; fullerenes such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₄ , carbon nanotubes such as SWNT, merocyanine dyes And pigments such as hemicyanine pigments.

  Among these π-conjugated materials, thiophene, chelenylene vinylene, phenylene vinylene, p-phenylene, and at least one of these substituents are used as repeating units, and the number n of the repeating units is 4 to 10. At least one selected from the group consisting of oligomers and polymers in which the number n of repeating units is 20 or more; condensed polycyclic aromatic compounds such as pentacene; fullerenes; condensed ring tetracarboxylic acid diimides; and metal phthalocyanines preferable.

  Other organic semiconductor materials include tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTTF-iodine complex, TCNQ-iodine complex. , And the like. Further examples include σ conjugated polymers such as polysilane and polygermane, and organic / inorganic hybrid materials described in Japanese Patent Application Laid-Open No. 2000-260999.

  In the present invention, for example, a material having a functional group such as acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, benzoquinone derivative, tetracyanoethylene, and tetracyanoquinodimethane are used for the organic semiconductor film. And materials that can accept electrons, such as derivatives thereof, materials that have functional groups such as amino groups, triphenyl groups, alkyl groups, hydroxyl groups, alkoxy groups, and phenyl groups, substituted amines such as phenylenediamine , Anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and its derivatives, tetrathiafulvalene and its derivatives, etc. .

  These organic semiconductor films can be prepared by vacuum deposition, molecular beam epitaxial growth, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, plasma polymerization method, electrolytic polymerization method, chemical method, etc. Examples thereof include a polymerization method, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method, and an LB method.

  The film thickness of the organic semiconductor film varies depending on the organic semiconductor material used, but is usually 1 μm or less, preferably from a monolayer thickness to 400 nm.

  The (B) gate electrode, (C) source electrode, and (D) drain electrode constituting the organic thin film transistor of the present invention are formed of a conductive material. Examples of conductive materials include platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, and oxide. Tin antimony, indium tin oxide (ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, Gallium, niobium, sodium, sodium-potassium alloy, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / oxide Miniumu mixture, lithium / aluminum mixture and the like. In addition, known conductive polymers whose conductivity is improved by doping or the like, such as conductive polyaniline, conductive polypyrrole, and conductive polythiophene (polyethylenedioxythiophene and polystyrenesulfonic acid complex, etc.) can be mentioned.

  In particular, the material for forming the (C) source electrode and the (D) drain electrode is preferably a material having low electrical resistance at the contact surface with the organic semiconductor film among the materials listed above. Gold, silver, ITO, conductive polymer and carbon are preferred.

  As the gate electrode, source electrode, and drain electrode used in the present invention, those formed using a fluid electrode material such as a solution, paste, ink, dispersion liquid, etc. containing the above conductive material, in particular, a conductive polymer, Or what was formed using the fluid electrode material containing the metal microparticle containing platinum, gold | metal | money, silver, and copper is preferable.

  As the fluid electrode material containing metal fine particles, for example, a known conductive paste may be used. Preferably, metal fine particles having an average particle diameter of 1 to 50 nm, preferably 1 to 10 nm are used as necessary. Using a dispersion stabilizer, a material dispersed in a dispersion medium that is water or an arbitrary organic solvent is used. The average particle diameter can be measured by a photon correlation method.

  As the material of the metal fine particles, in addition to the aforementioned platinum, gold, silver, copper, nickel, chromium, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, Tungsten, zinc or the like may be used.

  As a method for producing such a dispersion of fine metal particles, 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, colloidal method, coprecipitation method, etc. And a chemical production method for producing metal fine particles. After forming an electrode using these metal fine particle dispersions and drying the solvent, the metal fine particles are thermally fused by heating in the range of 100 to 300 ° C., preferably 150 to 200 ° C. as necessary. To form an electrode pattern having a desired shape.

  Another method of forming the electrode is to form a conductive thin film by sputtering or vapor deposition using the conductive material as a raw material, then form a pattern with photoresist, and then remove the unnecessary thin film by etching to form an electrode pattern. Photolithographic method, metal mask method on which a metal mask is placed on a substrate and sputtering or vapor deposition is performed as it is, electrode pattern is formed, and a photoresist pattern is formed on a metal foil such as aluminum or copper by thermal transfer or ink jet Then, a known method such as a method of forming an electrode pattern by removing an unnecessary thin film by etching may be used. Alternatively, a conductive polymer solution or dispersion, a dispersion containing metal fine particles, or the like may be directly patterned by an ink jet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning a conductive ink or conductive paste containing a conductive polymer or metal fine particles by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used. The thickness of the electrode is not particularly limited, but is usually 20 to 500 nm, preferably 50 to 200 nm.

  The (E) gate insulating film used in the organic thin film transistor of the present invention is a film containing an organic polymer compound that does not have a functional group having an unshared electron pair and does not have a π electron bond in the molecular structure. In addition to the organic polymer compound that does not have a functional group having an unshared electron pair and does not have a π-electron bond in the molecular structure, the gate insulating film has a range that does not inhibit the expression of the desired effect of the present invention. An organic polymer compound having the functional group and / or π-electron bond may be included. In the present specification, the “functional group” refers to an atomic group that is not involved in the formation of the skeleton structure of the main chain of the organic polymer compound and is bonded to the main chain and branched from the main chain.

  In this specification, an unshared electron pair is an electron which is paired two by two without being involved in a bond with another atom among the outermost electrons of the atom. It is also called a lone electron pair or a non-bonded electron pair. In the present invention, the functional group having an unshared electron pair is a group bonded to the main chain and branched from the main chain, and does not include those based on the main chain itself. For example, an ether group in the case where an ether group (—O—) is present in the main chain itself as in polyoxyethylene, and an imino group in the case where an imino group (> NH) is present in the main chain itself as in polyamine is an unshared electron pair. It is not included in the functional group having A nitrile group when there is a nitrile group bonded to the main chain such as polyacrylonitrile, or a fluorine group when there is a fluorine group bonded to the main chain such as polytetrafluoroethylene is a functional group having an unshared electron pair. included.

In this specification, a π-electron bond refers to a bond formed by electrons belonging to a π orbit. A π orbital is a type of orbit that accommodates electrons in a molecule, and orbitals that are distributed in a direction perpendicular to the axis (bonding axis) connecting the nuclei of one bond are above and below the molecular plane. This is an electron orbit created in the horizontal direction.
Specific examples of the bond having a π-electron bond include a carbon-carbon double bond and triple bond, a nitrogen-carbon triple bond, a carbon-oxygen double bond, and a benzene or naphthalene double bond. Can be mentioned.

The organic polymer compound contained in the gate insulating film of the present invention is a compound having no functional group having an unshared electron pair and having no π-electron bond in the molecular structure as described above. Any of these compounds can achieve the desired effects of the present invention. The organic polymer compound used in the present invention has a small relative dielectric constant and is usually 3 or less. The relative dielectric constant can be measured by a capacitance method using an LCR meter (manufactured by Agilent Technologies, product number 4284A).
Examples of such organic polymer compounds include polyolefins such as polyethylene, polypropylene, and polybutene; alicyclic olefin polymers; polyamines; polyethers; Of these, alicyclic olefin polymers are preferred from the viewpoint that the frequency dependence of the dielectric constant is small.

  The alicyclic olefin polymer suitably used in the present invention is a polymer having a cycloalkane structure in the main chain and / or side chain. From the viewpoint of mechanical strength and heat resistance, a polymer containing a cycloalkane structure in the main chain is preferred. In addition, examples of the cycloalkane structure include monocyclic rings and polycyclic rings (condensed polycyclic rings, bridged rings, etc.). The number of carbon atoms constituting one unit of the cycloalkane structure is not particularly limited, but is usually 4-30, preferably 5-20, and more preferably 5-15. Various properties such as strength, heat resistance and moldability are highly balanced and suitable. Moreover, the alicyclic olefin polymer used in the present invention is usually a thermoplastic resin.

  In the alicyclic olefin polymer, the repeating unit having a cycloalkane structure is usually 30 to 100% by weight, preferably 50 to 100% by weight, more preferably 70% in all repeating units in the main chain of the alicyclic olefin polymer. ~ 100% by weight. If the ratio of the repeating unit having a cycloalkane structure is within these ranges, the heat resistance is excellent.

  The alicyclic olefin polymer is usually obtained by subjecting an olefin having a ring structure to addition polymerization or ring-opening polymerization, and optionally hydrogenating an unsaturated bond portion and an aromatic ring portion.

Examples of the olefin having a ring structure used for obtaining the alicyclic olefin polymer include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, and tetracyclo [7.4. .1 ^10,13 . 0 ^2,7 ] polycyclic unsaturated hydrocarbons such as trideca-2,4,6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- Unsaturated hydrocarbons having a monocyclic structure such as (2-methylbutyl) -1-cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene And derivatives thereof; aromatic vinyl compounds such as styrene, α-methylstyrene, and divinylbenzene; and alicyclic vinyl compounds such as vinylcyclohexane, vinylcyclohexene, vinylcyclopentane, and vinylcyclopentene. The olefins having a ring structure can be used alone or in combination of two or more.

  A monomer copolymerizable with an olefin having a ring structure can be subjected to addition copolymerization, if necessary. Specific examples thereof include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1 -Pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, etc., ethylene or α-olefin having 2 to 20 carbon atoms; 1,4-hexadiene, 4-methyl-1, Non-conjugated dienes such as 4-hexadiene, 5-methyl-1,4-hexadiene and 1,7-octadiene; conjugated dienes such as 1,3-butadiene and isoprene It is. These monomers can be used alone or in combination of two or more.

  Polymerization of an olefin having a ring structure can be carried out according to a known method. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually performed at a polymerization temperature of -50 ° C to 100 ° C and a polymerization pressure of 0 to 5 MPa. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst.

  Specific examples of alicyclic olefin polymers include hydrides of ring-opening polymers of norbornene monomers, addition polymers of norbornene monomers and hydrides thereof, norbornene monomers and vinyl compounds (ethylene and , Α-olefins, etc.) and their hydrides, monocyclic cycloalkene polymers and their hydrides, alicyclic conjugated diene monomer polymers and their hydrides, vinyl alicyclic carbonization Examples thereof include a polymer of a hydrogen monomer and a hydrogenated product thereof, and a product obtained by hydrogenating an aromatic ring of a polymer of an aromatic vinyl compound. Among these, hydrides of ring-opening polymers of norbornene monomers, addition polymers of norbornene monomers, addition polymers of norbornene monomers and vinyl compounds (= ethylene, α-olefins, etc.) An aromatic ring hydride of an aromatic olefin polymer is preferable, and a hydride of a ring-opening polymer of a norbornene monomer is particularly preferable. The above alicyclic olefin polymers can be used alone or in combination of two or more. Here, the norbornene-based monomer is a monomer having a norbornene structure as shown in Chemical Formula 1. When a norbornene-based monomer is subjected to ring-opening polymerization, a polymer having a repeating unit as shown in Chemical Formula 2 is obtained. When this is hydrogenated, a polymer having a repeating unit as shown in Chemical Formula 3 is obtained.

  However, R1 and R2 in Chemical Formula 3 represent a substituent that does not have an unshared electron pair and has no π-electron bond, and R1 and R2 may be bonded to form a ring. R1 and R2 in Chemical Formula 1 and Chemical Formula 2 are those in which the alicyclic olefin polymer finally obtained through various production steps does not have a functional group having an unshared electron pair and does not have a π-electron bond. As long as it is, it is not particularly limited, but preferably represents a substituent having no unshared electron pair and having no π-electron bond, and R1 and R2 may be bonded to form a ring.

  The alicyclic olefin polymer used in the present invention is not particularly limited by its molecular weight. The molecular weight of the alicyclic olefin polymer is a polystyrene-reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using cyclohexane as a solvent, and is usually 1,000 to 1,000,000, preferably It is in the range of 5,000 to 500,000, more preferably 10,000 to 250,000. When the weight average molecular weight (Mw) of the alicyclic olefin polymer is within this range, heat resistance, adhesiveness, surface smoothness and the like are balanced, which is preferable.

  The molecular weight distribution of the alicyclic olefin polymer is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by GPC using cyclohexane as a solvent, and is usually 5 or less, preferably 4 Below, more preferably 3 or less. The glass transition temperature of the alicyclic olefin polymer is preferably 70 ° C. or higher, more preferably 120 ° C. or higher, and most preferably 140 ° C. or higher. The glass transition temperature can be measured with a differential scanning calorimeter.

  The gate insulating film of the present invention has an organic polymer that does not have a functional group having an unshared electron pair and does not have a π-electron bond in the molecular structure as long as the desired effect of the present invention is not inhibited. Other known organic polymer compounds may be contained in addition to the compounds. The content of the organic polymer compound having no functional group having an unshared electron pair and having no π electron bond in the molecular structure in the gate insulating film is preferably 70 to 100% by weight, more preferably 90 to 90% by weight. 100% by weight. In addition, other colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, antioxidants, lubricants, solvents, etc. are added as appropriate. It may be what you did.

  The gate insulating film can be formed by vacuum deposition, molecular beam epitaxy, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, plasma polymerization, electrolytic polymerization, chemical polymerization, Examples thereof include a combination method, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method, and an LB method. Of these, the wet method is preferred. The wet method is a method in which the organic polymer compound constituting the gate insulating film and optionally the compounding agent are dissolved in a solvent to obtain a solution, the solution is cast, the solvent is removed, and a film is formed. Examples thereof include spin coating, blade coating, dip coating, roll coating, bar coating, die coating, screen printing, and ink jet printing. Also, a printing method called soft lithography such as microcontact printing or micromolding can be applied.

  The thickness of the gate insulating film is not particularly limited, and any thickness may be used as long as the insulating property is maintained. In general, the thickness is preferably 20 nm or more and 1 μm or less, more preferably 80 to 500 nm, but is not limited thereto. It is desirable to make it as thin as possible as the size of the organic thin film transistor element becomes smaller.

  A preferable organic thin film transistor of the present invention has a protective film (for example, the protective film 23 in FIGS. 1 and 2) in the outermost layer. The protective film is, for example, a silicon oxide film, a silicon nitride film or a silicon oxynitride film formed by a CVD method or a sputtering method, a polyparaxylene film formed by a thermal CVD method, a polyimide film formed by coating, an alicyclic olefin A polymer film, an ultraviolet curable epoxy resin film, an acrylic resin film, and the like are preferable.

  In the organic thin film transistor shown in FIGS. 1 and 2, a substrate 11 is used to support the thin film organic thin film transistor. The substrate is not particularly limited, and any material may be used. In general, materials that are preferably used are flexible plastic substrates such as alicyclic olefin polymers in addition to polycarbonate, polyimide and polyethylene terephthalate (PET), but glass substrates such as quartz, soda glass, inorganic alkali glass, etc. A silicon wafer or the like can also be used.

  In the organic thin film transistor of the present invention, the substrate and / or protective film is preferably composed of the above-described alicyclic olefin polymer. Since the alicyclic olefin polymer has low moisture permeability and gas permeability, if the substrate and / or protective film is made of the above-described alicyclic olefin polymer, the effect of preventing deterioration of the organic semiconductor film is high.

  In addition, the organic thin film transistor of the present invention may have an organic semiconductor protective film in order to suppress deterioration of transistor characteristics due to deterioration of the organic semiconductor layer due to air, deterioration due to a coating solvent used during manufacturing, or the like. By providing the organic semiconductor protective film, durability against bending and the like is improved, which also contributes to suppressing deterioration of transistor characteristics.

  As the organic semiconductor protective film, a material that does not affect the organic semiconductor film after the manufacturing process of the organic semiconductor transistor or after the manufacturing is used. As a material that can be used for the organic semiconductor protective film, an acrylic polymer or copolymer such as polymethyl methacrylate (PMMA), a known polymer such as a urethane resin, a polyester resin, or a polyolefin resin is used in view of the influence on the organic semiconductor film. In addition, you can choose. In addition, for example, homopolymers and copolymers composed of components such as polyvinyl alcohol, 2-hydroxyethyl methacrylate (HEMA), acrylic acid, and acrylamide can be used.

  Other materials for the organic semiconductor protective film include materials containing inorganic oxides and inorganic nitrides. Inorganic oxides 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 yttrium trioxide. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide. Inorganic nitrides such as silicon nitride and aluminum nitride; and smectite group layered silicate compounds such as ionite, saponite, hectorite, soconite, stevensite, swinholderite, montmorillonite, beidellite, nontronite, and bolcon score It is done.

  The method for forming the organic semiconductor protective film is not particularly limited. For example, the vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, atmospheric pressure By dry process such as plasma method, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, etc., patterning such as printing or inkjet Examples include wet processes such as methods. Moreover, you may add a heat baking process. The thickness of the organic semiconductor protective film is preferably 0.1 μm to 10 μm.

  The organic thin film transistor shown in FIGS. 1 and 2 which is an example of the embodiment of the present invention has an undercoat layer containing a compound selected from a polymer or an inorganic oxide and an inorganic nitride.

  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 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.

  Polymers used for the undercoat layer containing polymer include polyester resin, polycarbonate resin, cellulose resin, 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 copolymer Polymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, chlorinated polyvinyl chloride, ethylene-vinyl chloride copolymer, vinyl polymers such as ethylene-vinyl acetate copolymer, polyamide resin, ethylene-butadiene resin, Tajien - rubber-based resin such as acrylonitrile resin, silicone resin, and fluorine resins.

  The undercoat layer is not particularly limited by the formation method. Examples of the method for forming the undercoat layer include dry processes such as vacuum deposition, molecular beam epitaxial growth, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, and atmospheric pressure plasma. And wet processes such as spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, and other methods such as printing and ink jet patterning. Can be mentioned.

The display device of the present invention includes the organic thin film transistor. In order to describe the display device of the present invention more specifically, an organic EL display device will be described as an example.
In the organic EL display device of the present invention, each pixel formed in a matrix arrangement on a substrate has at least one organic EL element and at least two organic thin film transistors for driving the organic EL element. is there. At least one of the organic thin film transistors is the above-described organic thin film transistor of the present invention.

  The organic EL element is not particularly limited, and has, for example, a structure (SH-A structure) in which a hole transport layer and a light emitting material layer are formed between a hole injection electrode serving as an anode and an electron injection electrode serving as a cathode. A structure in which a light emitting material layer and an electron transport layer are formed between a hole injection electrode and an electron injection electrode (SH-B structure), or between a hole injection electrode and an electron injection electrode, Examples include a structure (DH structure) in which a hole transport layer, a light emitting material layer, and an electron transport layer are formed. Regardless of the structure, the organic EL element has a light emitting material layer and a hole (or electron) transport layer in which holes injected from a hole injection electrode (anode) and electrons injected from an electron injection electrode (cathode) are used. It operates on the principle that light is emitted by recombination within the interface and the light emitting material layer.

  FIG. 3 shows a configuration example of a typical organic EL element. The organic EL element shown in FIG. 3 includes a transparent substrate 11 ′, a lower electrode layer (anode) 54, a light emitting material layer 62, and an upper electrode layer (cathode) 55. A protective film 23 is provided as the outermost layer. The transparent substrate 11 'has a light transmittance in the visible region of 400 to 700 nm of 50% or more, is smooth, and does not change characteristics when forming each layer of the electrode or organic EL element. Is preferred.

  The transparent substrate 11 'can be formed of a material selected from the group consisting of plastic, glass, quartz, silicon, and ceramic. In particular, when plastic is used as the substrate material, a flexible and lightweight organic EL display can be obtained. The plastic is preferably selected from the group consisting of polycarbonate resin, polyethersulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin and alicyclic olefin polymer. The average thickness of the substrate is usually 30 μm to 3 mm, preferably 50 to 300 μm.

  Examples of the material constituting the lower electrode layer 54 include a material for emitting light from the lower electrode layer, and specifically, a conductive metal oxide, a translucent metal, or a laminate thereof. Specifically, indium oxide, zinc oxide, tin oxide, and their composite materials such as indium tin oxide (ITO), indium oxide zinc, conductive glass (NESA etc.), gold, platinum, silver Copper, etc. are used, and among them, ITO, indium / zinc oxide, and tin oxide are preferable. As the lower electrode layer, an organic transparent conductive film such as polyaniline or a derivative thereof or polythiophene may be used.

The average thickness of the lower electrode layer can be appropriately selected in consideration of light transmittance and electrical conductivity, but is usually 10 nm to 10 μm, preferably 100 to 500 nm.
It is convenient that the lower electrode layer is transparent or translucent because the emission efficiency of light emission is good. Examples of the method for producing the lower electrode layer include a vacuum deposition method, a sputtering method, and a laminating method in which a metal thin film is thermocompression bonded.

There is no restriction | limiting in particular in the material which comprises the luminescent material layer 62, A well-known thing can be used as a luminescent material in a conventional organic EL element. Specific examples of such light-emitting materials include fluorescent brighteners such as benzothiazole, benzimidazole, and benzoxazole, metal chelated oxinoid compounds, styrylbenzene compounds, distyrylpyrazine derivatives, and aromatic dimethylidine compounds. Etc.
Two or more kinds of light emitting materials may be mixed and used in the light emitting material layer, or two or more light emitting material layers may be laminated. Examples of a method for manufacturing the light emitting material layer include a vacuum deposition method and a casting method.
The average thickness of the light-emitting material layer varies depending on the material used, and may be selected so that the driving voltage and the light emission efficiency are appropriate. Usually, the thickness is 1 nm to 1 μm, preferably 2 nm to 500 nm. .

The material constituting the upper electrode layer 55 (cathode) is preferably a material having a small work function, and is a mirror body that reflects emitted light from the light emitting material layer toward the upper electrode layer and directs it toward the lower electrode layer. More preferably. Specifically, metals such as lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium, europium, terbium, ytterbium, And an alloy of two or more metals selected from these, or one or more metals selected from these, and selected from gold, silver, platinum, copper, manganese, titanium, cobalt, nickel, tungsten, and tin An alloy with one or more metals, graphite, a graphite intercalation compound, or the like is used. Specific examples of the alloy include magnesium-silver alloy, magnesium-indium alloy, magnesium-aluminum alloy, indium-silver alloy, lithium-aluminum alloy, lithium-magnesium alloy, lithium-indium alloy, and calcium-aluminum alloy. . The upper electrode layer may have a laminated structure of two or more layers. Examples of the method for producing the upper electrode layer include a vacuum deposition method, a sputtering method, an ion plating method, and a plating method.
The average thickness of the upper electrode layer can be appropriately selected in consideration of electric conductivity and durability, but is usually 10 nm to 10 μm, preferably 100 to 500 nm.

The organic EL element may have other layers in addition to the transparent substrate 11, the lower electrode layer 54, the light emitting material layer 62, the upper electrode layer 55, and the protective film 23. Examples of the other layers include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.
The hole injection layer is a layer provided adjacent to the anode and refers to a layer having a function of improving hole injection efficiency from the anode. The average thickness of the hole injection layer is usually 1 nm to 100 nm, preferably 2 nm to 50 nm.
The hole transport layer 21 refers to a layer having a function of transporting holes. The thickness of the hole transport layer differs depending on the material used and may be selected so that the drive voltage and the light emission efficiency are appropriate, but at least a thickness that does not cause pinholes is required. If the thickness is too thick, the driving voltage of the element increases, which is not preferable. Therefore, the average thickness of the hole transport layer is usually 1 nm to 1 μm, preferably 2 nm to 500 nm.
Examples of materials used for the hole injection layer and the hole transport layer include those conventionally known as hole transport compounds in organic EL devices.

The electron transport layer refers to a layer having a function of transporting electrons.
The thickness of the electron transport layer varies depending on the material used and may be selected so that the driving voltage and the light emission efficiency are appropriate values, but at least a thickness that does not cause pinholes is required. If it is too thick, the driving voltage of the organic EL element becomes high, which is not preferable. Therefore, the average thickness of the electron transport layer is usually 1 nm to 1 μm, preferably 2 nm to 500 nm.
The electron injection layer is a layer provided adjacent to the cathode and has a function of improving the electron injection efficiency from the cathode and has an effect of lowering the driving voltage of the element.
The average thickness of the electron injection layer is usually 1 nm to 100 nm, preferably 2 nm to 50 nm. Examples of materials used for the electron transport layer and the electron injection layer include those conventionally known as electron transport compounds in organic EL devices. Examples of the method for manufacturing the other layers include spin coating, casting, and vacuum deposition.

  FIG. 4 is a circuit configuration example for one pixel of the organic EL display device of the present invention. As a configuration for one pixel of the organic EL display device, at least two organic thin film transistors for driving the EL element are usually required for at least one organic EL element, that is, a driving transistor and a writing transistor. However, in the configuration example of FIG. 4, only the drive transistor is shown, and the write transistor is omitted. At least one of the driving transistor and the writing transistor is constituted by the organic thin film transistor of the present invention.

  In FIG. 4, the anode of the organic EL element and the drain electrode 14 of the organic thin film transistor 5 (drive transistor) of the present invention are connected. Then, for example, in an active matrix circuit as shown in FIG. 5, the organic thin film transistor 2 (write transistor) is turned on by a voltage applied sequentially to the scan electrodes 1 connected to the horizontal drive circuit, and the vertical drive circuit An amount of charge corresponding to the display signal from the data electrode 3 connected to is stored in the capacitor 4. The drive transistor 5 operates according to the amount of charge accumulated in the capacitor 4, a current is supplied to the organic EL element 6, and the organic EL element is turned on. This lighting state is maintained until a voltage is applied to the scan electrode 1.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not restrict | limited to the following Example. Parts and% are based on weight unless otherwise specified.

Example 1
An insulating film was obtained by spin-coating 5 ml of a 5% cyclohexane solution of an alicyclic olefin polymer (manufactured by Nippon Zeon Co., Ltd .: ZEONEX (registered trademark) 480R) on a glass substrate and a glass substrate on which aluminum was deposited. The rotation was performed at 2000 to 7000 rpm for 30 seconds.
Further, 5 ml of a 2.5% cyclohexane solution of an alicyclic olefin polymer (manufactured by Nippon Zeon Co., Ltd .: ZEONEX (registered trademark) 480R) was spin-coated on a glass substrate and a glass substrate on which aluminum was vapor-deposited to obtain insulating films. . The rotation was performed at 2000 rpm for 30 seconds.

  FIG. 6 shows the dependency of the thickness of the insulating thin film obtained in Example 1 on the spin rate and the solvent concentration. Moreover, the image of the atomic force microscope (AFM) image of the insulating thin film surface obtained in Example 1 is shown in FIG. As shown in FIG. 7, a very smooth surface was obtained with the alicyclic olefin polymer (RMS <0.3 nm). From these results, it can be seen that an extremely thin uniform thin film was obtained by the alicyclic olefin polymer.

Example 2
The same alicyclic olefin polymer as in Example 1 5% cyclohexane solution 5 ml, aluminum was deposited on one side of the thin film obtained by spin coating at 4000 rpm for 30 seconds, and gold was deposited on the other side, and the size was 1 mm × 1 mm. An element having a metal-insulator-metal (MIM (Metal-Insulator-Metal)) structure was obtained. In the vapor deposition of aluminum and gold, the degree of vacuum was less than 1 × 10 ⁻² Pa, the substrate temperature was RT (room temperature), and the film thickness was about 200 nm.
Also, aluminum and gold were vapor-deposited in the same manner as described above on a thin film obtained by spin coating for 30 seconds at 2000 rpm with 5 ml of a 2.5% cyclohexane solution of the same alicyclic olefin polymer as in Example 1 to obtain a device having an MIM structure.

  The electrical characteristics of these MIM structural elements were evaluated by measuring current-voltage curves, capacitance-frequency curves, and the like, and the results are shown in FIGS. 8 and 9 (measurement devices are HP4284A LCR Meter and R6245-2-Channel). Current Voltage Source / Monitor).

As shown by the current-voltage curve in FIG. 8, this MIM structure element has a very small leakage current and a high withstand voltage (> 1 × 10 ⁶ V / cm). Furthermore, as shown in FIG. 9, it turns out that an electrical capacitance does not depend so much on a frequency (20-1 MHz).

Example 3
A bottom gate type organic thin film transistor (TFT) (Stagger type) as shown in FIG. A glass substrate (25 mm × 10 mm × 1 mm) or a polyethylene terephthalate film substrate (25 mm × 10 mm × 0.5 mm) was used as the substrate. The gate electrode was formed by evaporating aluminum on the substrate. The aluminum was deposited such that the degree of vacuum was less than 1 × 10 ⁻² Pa, the temperature of the substrate was RT (room temperature), and the film thickness was about 200 nm. As the gate insulating film, the same alicyclic olefin polymer 5% as in Example 1 having a thickness of about 450 nm obtained by spin-coating 5 ml of cyclohexane solution at 4000 rpm for 30 seconds, and alicyclic olefin polymer 2.5% A cyclohexane solution having a thickness of about 260 nm obtained by spin coating at 2000 rpm for 30 seconds was used.

The organic semiconductor film was formed by vapor-depositing pentacene on the gate insulating film. The vapor deposition of pentacene is performed so that the degree of vacuum is less than 2 × 10 ⁻³ Pa, the substrate temperature is RT (room temperature), the deposition temperature is 185 ° C., the deposition rate is 0.06 nm / s, and the film thickness is about 50 nm. It was. The source electrode and the drain electrode (W = 5 mm; L = 20-70 μm) were formed by covering a metal mask on the organic semiconductor film and depositing gold thereon. Gold was deposited so that the degree of vacuum was less than 1 × 10 ⁻² Pa, the temperature of the substrate was RT (room temperature), and the film thickness was about 200 nm.

  The electrical characteristics of these TFTs were evaluated by measuring current-voltage curves, and the results are shown in FIGS. 10 to 12 (the measuring apparatus is R6425 2 Channel Current-Voltage Source / Monitor).

In FIG. 10A, pentacene is used for the organic semiconductor film, the thickness of the gate insulating film is about 260 nm (C _i = 7.66 nF / cm ² ), the substrate is glass, and the shape between the source and drain is This shows the operating characteristics of a TFT in which W = 5 mm and L = 70 μm. 10 (b) is the square root vs. _{V G} plot of _{I D} of FIG. 10 (a), the mobility from the slope of the curve was calculated to 0.042 ^cm 2 / Vs.

In FIG. 11A, pentacene is used for the organic semiconductor film, the gate insulating film has a thickness of about 450 nm (C _i = 4.50 nF / cm ² ), the substrate is a polyethylene terephthalate film, and the source-drain gap This shows the operating characteristics of the TFT with the shape of W = 5 mm and L = 50 μm. FIG. 11B is a square root vs. V _G plot of _{ID in} FIG. 11A, and the mobility was calculated to be 0.20 cm ² / Vs from the slope of the curve.

FIG. 12 shows the sweep characteristics of a TFT in which pentacene is used for the organic semiconductor film, the gate insulating thin film has a thickness of about 450 nm, and the substrate is glass. FIG upper 12 is _V D -I _D diagram when changing between the _{V D} + 10V and -60V at a constant state _{V G,} V the lower part _{V D} at steady state (-60V) a _V G -I _D diagram when changing between the _G + 20V and -60 V. From these results, it can be seen that the organic TFT of the present invention has good characteristics with very little hysteresis.

Claims (10)

On the substrate, (A) an organic semiconductor film, (B) a gate electrode, (C) a source electrode, (D) a drain electrode, and (E) a functional group having an unshared electron pair, and π in the molecular structure An organic thin film transistor having a gate insulating film comprising an organic polymer compound having no electronic bond. The organic thin film transistor according to claim 1, wherein the gate insulating film is formed by a wet method. The organic thin film transistor according to claim 1 or 2, wherein the organic polymer compound is an alicyclic olefin polymer. Furthermore, the organic thin-film transistor in any one of Claims 1-3 which has a protective film. The organic thin film transistor according to claim 4, wherein the substrate and / or the protective film is made of an alicyclic olefin polymer. A gate insulating film comprising an organic polymer compound having no functional group having an unshared electron pair and having no π-electron bond in the molecular structure. The gate insulating film according to claim 6, wherein the organic polymer compound is an alicyclic olefin polymer. A step of obtaining a solution by dissolving an organic polymer compound having no functional group having an unshared electron pair and having no π-electron bond in the molecular structure in a solvent, and after casting the solution, removing the solvent; A method for producing an organic thin film transistor, comprising a step of forming a gate insulating film. A display device comprising the organic thin film transistor according to claim 1. Each pixel formed in a matrix arrangement on the substrate has at least one organic EL element and at least two organic thin film transistors for driving the organic EL element,
An organic EL display device, wherein at least one of the organic thin film transistors is the organic thin film transistor according to claim 1.

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