JP2008130910A - Organic thin film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film transistor operable with a low gate voltage in which the occurrence of leak currents is suppressed, and high carrier mobility is obtained, and an on/off ratio is large. <P>SOLUTION: In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode and a drain electrode on a substrate, the gate insulating layer is configured of a first insulating layer brought into contact with the gate electrode and a second insulating layer brought into contact with the organic semiconductor layer, and (A) the first insulating layer is formed of the mixture of insulating organic polymer and inorganic particles, and the specific inductive capacity of the first insulating layer is higher than the specific inductive capacity of the second insulating layer, and (B) the second insulating layer is formed of cyclic olefine resin having a polar group, and the arithmetic mean roughness Ra of the interface of the second insulating layer and the organic semiconductor layer is set so as to be 10 nm or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic thin film transistor suitably used for a flat display device such as a liquid crystal display device or an organic electroluminescence display device.

An organic thin film transistor is a transistor having (A) an organic semiconductor layer, (B) a gate electrode, (C) a source electrode, (D) a drain electrode, and (E) a gate insulating layer on a substrate. (B) a bottom gate type having a gate electrode, (E) a (C) source electrode connected by an organic semiconductor layer via a gate insulating layer, and (D) a drain electrode, and a substrate; A top gate type having (A) a source electrode and (D) a drain electrode in contact with the organic semiconductor layer (A) and (E) a gate electrode on the (E) gate insulating layer. Broadly divided.
The organic thin film transistor can be manufactured 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 these characteristics, organic thin film transistors can be applied to image driving elements of flat panel displays such as liquid crystal display devices, organic electroluminescence display devices, and electrophoretic display devices, and sheet displays, electronic paper, electronic price tags, and electronic tags. Application to integrated circuit technology of electronic devices such as electronic tags and biosensors is expected.
In order to improve the expected characteristics of organic thin film transistors, organic gate insulating materials have been actively developed. For example, as an organic field effect transistor having an insulating film having high capacity, high insulation resistance, and flatness of an interface with an organic semiconductor, in a transistor element using an organic semiconductor, the gate insulating film has a high dielectric constant containing at least a polymer. An organic field effect transistor is proposed, which is a laminate including an insulating film and a low dielectric constant insulating film containing a polymer, wherein the dielectric constant difference between the low dielectric constant insulating film and the high dielectric constant insulating film is greater than 1. (Patent Document 1). Materials used for the low dielectric constant insulating film include acrylic resin, styrene resin, polyimide resin, polycarbonate resin, polyester resin, polyvinyl acetate, polyurethane resin, polysulfone resin, epoxy resin, fluororesin, polycylose oxane, poly Examples are polymers such as siloxane.
Further, as an organic thin film transistor having high mobility, high on-current, low leakage current, and high on / off ratio, an insulator layer, a gate electrode and an organic semiconductor layer separated by the insulator layer, and the organic semiconductor layer An organic thin film transistor having a source electrode and a drain electrode provided so as to be in contact with each other and an insulating support substrate, an organic thin film transistor having an average roughness of an interface between the insulator layer and the organic semiconductor layer of 50 nm or less is proposed In addition, a photocurable aromatic acrylate polymer is exemplified as an insulator (Patent Document 2).
JP-A-2005-72569 JP 2004-63975 A

However, in conventional organic gate insulating materials, unless a large film thickness is generally secured, a leakage current due to a tunneling phenomenon flows through the insulating film, resulting in failure to maintain insulation, and further hinders gate bias application. The problem that a high on / off ratio was not obtained was recognized.
An object of the present invention is to provide an organic thin film transistor that can suppress the generation of leakage current, has high carrier mobility, has a large on / off ratio, and can operate at a low gate voltage.

〔式中、Ｒ¹〜Ｒ⁴は、それぞれ独立して、水素原子又は-Ｘ_n-Ｒ'（Ｘは二価の有機基であり、ｎは０又は１であり、Ｒ'は、置換基を有していてもよいアルキル基、置換基を有していてもよい芳香族基、又は極性基である。）であり、Ｒ¹〜Ｒ⁴のうち少なくとも１つは、Ｒ'が極性基である-Ｘ_n-Ｒ'であり、ｍは０〜２の整数である。〕
で表される構造単位、及び／又は、以下の一般式（II）：

〔式中、Ｒ⁵とＲ⁶は、それらが結合する２つの炭素原子と一緒になって、置換基を有していてもよい、酸素原子又は窒素原子を含む、３員又は５員複素環構造を形成し、ｋは０〜２の整数である。〕
で表される構造単位を有するものである、前記〔１〕〜〔５〕のいずれか１項に記載の有機薄膜トランジスタ、並びに
〔７〕保護層をさらに有する前記〔１〕〜〔６〕のいずれか１項に記載の有機薄膜トランジスタ、
を提供するものである。 As a result of intensive studies to solve the above-mentioned problems, the present inventor, as a result, in an organic thin film transistor, a gate insulating layer is formed by a first insulating layer in contact with the gate electrode, and a second insulating layer in contact with the organic semiconductor layer. The first insulating layer has a relative dielectric constant higher than that of the second insulating layer, and the second insulating layer is formed of an alicyclic olefin resin having a polar group. By flattening the interface in contact with the layer, it was found that an organic thin film transistor having a large on / off ratio can be obtained by suppressing the generation of leakage current, and the present invention has been completed based on this finding.
That is, the present invention
[1] In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode and a drain electrode on a substrate, the gate insulating layer is in contact with the organic semiconductor layer and the first insulating layer in contact with the gate electrode. A second insulating layer,
(A) the first insulating layer is formed of a mixture of an insulating organic polymer and inorganic fine particles, and the relative dielectric constant of the first insulating layer is higher than the relative dielectric constant of the second insulating layer;
(B) The second insulating layer is formed of an alicyclic olefin resin having a polar group, and the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is 10 nm or less.
An organic thin film transistor characterized by
[2] The organic thin film transistor according to [1], wherein the gate insulating layer has a thickness of 10 to 500 nm.
[3] The organic thin film transistor according to [1] or [2], wherein the relative dielectric constant of the first insulating layer is 5 or more and the relative dielectric constant of the second insulating layer is 4 or less.
[4] The content of inorganic fine particles in the first insulating layer is 50 to 500 parts by weight with respect to 100 parts by weight of the insulating organic polymer, according to any one of [1] to [3]. Organic thin film transistors,
[5] The organic thin film transistor according to any one of [1] to [4], wherein the inorganic fine particles of the first insulating layer are inorganic metal oxides or nanoparticles of a high dielectric insulator,
[6] The alicyclic olefin resin having a polar group in the second insulating layer is represented by the following general formula (I):

[Wherein, R ^{1 to} R ⁴ are each independently a hydrogen atom or —X _n —R ′ (X is a divalent organic group, n is 0 or 1, and R ′ is a substituent. Or an aromatic group which may have a substituent, or a polar group. At least one of R ^{1 to} R ⁴ is such that R ′ is a polar group. -X _n -R ', and m is an integer of 0-2. ]
And / or the following general formula (II):

[Wherein R ⁵ and R ⁶ are a 3-membered or 5-membered heterocyclic ring containing an oxygen atom or a nitrogen atom, which may have a substituent, together with two carbon atoms to which they are bonded. Forming a structure, k is an integer from 0 to 2; ]
The organic thin film transistor according to any one of [1] to [5], and [7] any one of [1] to [6], further including a protective layer. Or an organic thin film transistor according to claim 1,
Is to provide.

  The organic thin film transistor of the present invention hardly generates leak current, can be operated with a low gate voltage, and has a large on / off ratio. Therefore, according to the organic thin film transistor of the present invention, for example, an excellent flat display device with low power consumption and high contrast can be manufactured.

An organic thin film transistor of the present invention includes a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate. The organic thin film transistor includes: a first insulating layer in contact with the gate electrode; A second insulating layer in contact with the semiconductor layer;
(A) the first insulating layer is formed of a mixture of an insulating organic polymer and inorganic fine particles, and the relative dielectric constant of the first insulating layer is higher than the relative dielectric constant of the second insulating layer;
(B) The second insulating layer is formed of an alicyclic olefin resin having a polar group, and the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is 10 nm or less.

  FIG. 1 is a schematic cross-sectional view of one embodiment of the organic thin film transistor of the present invention. In the organic thin film transistor of this embodiment, a gate electrode 2 is provided on a substrate 1, and the gate electrode 2 and the substrate 1 are covered with a first insulating layer 3. A second insulating layer 4 is provided on the first insulating layer 3, and the second insulating layer 4 is in contact with the organic semiconductor layer 5. Further, a source electrode 6 and a drain electrode 7 are provided in contact with the organic semiconductor layer 5. A protective layer 8 is provided as the outermost layer. Such a schematic cross-sectional view shows one embodiment of a bottom-gate organic thin film transistor. Hereinafter, from the viewpoint of simplifying the description, the description will be made mainly based on the configuration of the bottom gate type organic thin film transistor. However, the organic thin film transistor of the present invention may be a top gate type organic thin film transistor.

  There is no restriction | limiting in particular in the board | substrate used for this invention, For example, flexible plastic substrates, such as a polycarbonate, a polyimide, a polyethylene terephthalate, an alicyclic olefin resin; Glass substrates, such as quartz, soda glass, an inorganic alkali glass; Silicon wafer etc. And the like.

In the present invention, examples of the conductive material constituting the gate electrode, the source electrode, and the drain electrode include platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, palladium, and 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, carbon paste, beryllium, Magnesium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / And the like aluminum mixtures. In addition, a conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene (polyethylenedioxythiophene and polystyrenesulfonic acid complex, etc.), and the like can be given.
In the present invention, the material constituting the source electrode and the drain electrode preferably has a small electric resistance at the contact surface with the organic semiconductor layer. In the case of a p-type semiconductor, platinum, gold, silver, ITO, carbon, and conductivity A polymer can be particularly preferably used.

In the present invention, the gate electrode, the source electrode, and the drain electrode are formed using a fluid electrode material such as a solution, paste, ink, or dispersion liquid containing the above conductive material, in particular, a conductive polymer, or It is preferably formed using a fluid electrode material containing fine metal particles such as platinum, gold, silver and copper. As a fluid electrode material containing metal fine particles, metal fine particles having an average particle diameter of 1 to 50 nm, preferably 1 to 10 nm are usually added to a dispersion medium such as water or an organic solvent using a dispersion stabilizer as required. A dispersed material can be mentioned. The average particle diameter can be measured by a photon correlation method.
As a method for producing such metal fine particles, for example, a metal ion is reduced in a liquid phase such as a physical generation method such as a gas evaporation method, a sputtering method, or a metal vapor synthesis method, or a colloid method or a coprecipitation method. Examples thereof include a chemical production method for producing metal fine particles. After forming an electrode using the obtained dispersion of metal fine particles and drying the solvent, the metal fine particles are thermally fused by heating at 100 to 300 ° C., preferably 150 to 200 ° C., if desired. An electrode pattern having a desired shape can be formed.
Another method for forming the electrode is to form a conductive thin film by a method such as vapor deposition or sputtering using the above-mentioned conductive material as a raw material, then form a photoresist pattern, and then remove the unnecessary thin film by etching to form an electrode pattern. A photolithographic method for forming a metal mask, a metal mask method for forming an electrode pattern by directly depositing a metal mask on a substrate, and a photoresist pattern by thermal transfer or ink jet on a metal foil such as aluminum or copper There are known methods such as a method of forming an electrode by removing an unnecessary metal thin film by etching after forming the electrode. Further, 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 a lithographic method or laser ablation. Furthermore, 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. Although there is no restriction | limiting in particular in the thickness of an electrode, It is preferable that it is 20-500 nm, and it is more preferable that it is 50-200 nm.

  In the present invention, the organic semiconductor material constituting the organic semiconductor layer is not particularly limited, and examples thereof include a π-conjugated material. 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) ), Poly (3,4-disubstituted thiophene), polythiophenes such as polybenzothiophene; polyisothianaphthenes such as polyisothianaphthene; polychenylene vinylenes such as polychenylene vinylene; poly (p-phenylene) Poly (p-phenylene vinylenes) such as vinylene; polyanilines such as polyaniline, poly (N-substituted aniline), poly (3-substituted aniline), poly (2,3-disubstituted aniline); polyacetylene, polydiacetylene Polyacetylenes such as; Polyazulenes such as polyazulene; Polypyrenes such as polypyrene; Polycarbazole Polycarbazoles such as poly (N-substituted carbazole); polyselenophenes such as polyselenophene; polyfurans such as polyfuran and polybenzofuran; poly (p-phenylene) s such as poly (p-phenylene); Polyindoles such as indole; polypyridazines such as polypyridazine; naphthacene, pentacene, hexacene, heptacene, dibenzopentacene, tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene, coronene, terylene, ovarene, quaterylene, circumcamanthracene, etc. Polyacenes; and derivatives obtained by substituting some of the carbons of the polyacenes with functional groups such as nitrogen, sulfur, oxygen and other functional groups such as carbonyl groups (such as triphenodioxazine, triphenodithiazine, hexacene-6,15-quinone). Polymers such as polyvinyl carbazole, polyphenylene sulfide, and polyvinylene sulfide; polycyclic condensates having two or three 6-membered rings and fused aromatic rings and condensed with 5-membered heteroaromatic rings; And so on.

Also, having the same repeating unit as the polymer as described above, for example, α-sexual thiophene which is a thiophene hexamer, α, ω-dihexyl-α-sexual thiophene, α, ω-dihexyl-α-quinkethiophene, α , ω-bis (3-butoxypropyl) -α-sexualthiophene, oligomers such as styrylbenzene derivatives, and the like. Further, metal phthalocyanines such as copper phthalocyanine, chlorine or fluorine-substituted copper phthalocyanine; naphthalene-1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4-trifluoromethylbenzyl) 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, N, N'-dioctylnaphthalene-1,4,5,8-tetracarboxylic acid diimide, naphthalene-2,3,6,7- Naphthalene tetracarboxylic acid diimides such as tetracarboxylic acid diimide; anthracene tetracarboxylic acid diimide such as anthracene-2,3,6,7-tetracarboxylic acid diimide Condensed ring tetracarboxylic acid diimides such as CFCs; fullerenes such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₄ ; carbon nanotubes such as single-walled carbon nanotubes (SWNT); merocyanine dyes, hemicyanine dyes, etc. Examples thereof include 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 of the repeating units is 4 to 10. An oligomer; a polymer having 20 or more repeating units; a condensed polycyclic aromatic compound such as pentacene; a fullerene; a condensed ring tetracarboxylic acid diimide; a metal phthalocyanine can be suitably used.

Further, as other organic semiconductor materials, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, bisethylenetetrathiafulvalene (BEDTTTTF) -iodine Complexes, organic molecular complexes such as tetracyanoquinodimethane (TCNQ) -iodine complex; σ-conjugated polymers such as polysilane and polygermane; organic / inorganic hybrid materials such as phenethylammonium tin iodide and butyldiammonium iodide iodide, etc. Can be mentioned.
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, tetracyanoquinodimethane is used for the organic semiconductor layer. Materials that accept electrons, such as derivatives thereof, materials having functional groups such as amino groups, triphenyl groups, alkyl groups, hydroxyl groups, alkoxyl groups, and phenyl groups, phenylenediamine Substituent amines such as, anthracene, benzoanthracene, substituted benzoanthracene, pyrene, substituted pyrenes, carbazole and derivatives thereof, tetrathiafulvalene and derivatives thereof, and the like are included as donor materials that are donors of electrons be able to.
In the present invention, the method for forming the organic semiconductor layer is not particularly limited. For example, a vacuum deposition method, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a chemical vapor deposition method ( CVD), sputtering method, plasma polymerization method, electrolytic polymerization method, chemical polymerization method, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, Langmuir An example is a Blodget (LB) method. In the present invention, the thickness of the organic semiconductor layer is preferably 1 μm or less, and more preferably the thickness of the monomolecular layer is 400 nm or less.

The gate insulating layer of the present invention comprises a first insulating layer in contact with the gate electrode and a second insulating layer in contact with the organic semiconductor layer,
(A) the first insulating layer is formed of a mixture of an insulating organic polymer and inorganic fine particles, and the relative dielectric constant of the first insulating layer is higher than the relative dielectric constant of the second insulating layer;
(B) The second insulating layer is formed of an alicyclic olefin resin having a polar group, and the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is 10 nm or less.
The gate insulating layer of the present invention only needs to have the first insulating layer and the second insulating layer, and further includes any other insulating layer as long as the desired effect of the present invention is not inhibited. You may do it. In general, the gate insulating layer of the present invention is preferably formed of two layers, the first insulating layer and the second insulating layer.
The relative dielectric constant of the first insulating layer is preferably 5 or more, more preferably 10 or more, and further preferably 15 or more, from the viewpoint of satisfactorily expressing the desired effect of the present invention. . The upper limit of the relative dielectric constant is usually about 50. In the present invention, the relative dielectric constant is measured at a frequency of 100 kHz at 25 ° C. in accordance with the method described in Examples below.
In the present invention, the relative dielectric constant of the first insulating layer is higher than that of the second insulating layer, and the relative dielectric constant of the first insulating layer is twice the relative dielectric constant of the second insulating layer. The above is preferable.
The thickness of the first insulating layer is not particularly limited, and may be any thickness as long as the insulating property is maintained, but is usually 5 to 500 nm, preferably 10 to 300 nm.
The relative dielectric constant of the second insulating layer is preferably 4 or less, more preferably 2 to 4, preferably 2.5 to 3.5 from the viewpoint of satisfactorily expressing the desired effect of the present invention. More preferably. The lower limit of the relative dielectric constant is usually about 2.
The arithmetic mean roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is 10 nm or less, preferably 5 nm or less. If the arithmetic average roughness Ra of the second insulating layer is within such a range, it is desirable that high carrier mobility is exhibited and the on / off ratio of the organic thin film transistor is increased. In the present invention, the arithmetic average roughness Ra can be measured using a focused ion beam apparatus (FIB) and determined according to JIS B 0601.
There is no restriction | limiting in particular in the thickness of a 2nd insulating layer, From a viewpoint of expressing the desired effect of this invention favorably, it is preferable that it is less than 300 nm, and it is more preferable that it is 50-270 nm.
The effective dielectric constant of the entire gate insulating layer can be adjusted by appropriately setting the relative dielectric constant and film thickness of the first insulating layer and the relative dielectric constant and film thickness of the second insulating layer. The thickness of the gate insulating layer as a whole is not particularly limited as long as the insulating property is maintained, but is preferably 10 to 500 nm.

The first insulating layer is formed of a mixture of an insulating organic polymer and inorganic fine particles.
Examples of the insulating organic polymer include alicyclic olefin resin, novolac resin, phenol resin, acrylic resin, olefin resin, vinyl chloride resin, epoxy resin, melamine resin, urea resin, aromatic polyether, polyester, polyamide , Polyamideimide, polyimide, polycarbonate, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyarylate, polyphenylene sulfide, polyethersulfone, polyetherketone, polyphthalamide, polyethernitrile, polybenzimidazole, polysiloxane, polymethylmethacrylate, poly Methacrylamide, nitrile rubber, acrylic rubber, polytetrafluoroethylene, polybutene, polypentene, ethylene-propylene copolymer, ethylene-propylene Pyrene-diene copolymer, ethylene-butene-diene copolymer, polybutadiene, polyisoprene, butyl rubber, polymethylpentene, polystyrene, styrene-butadiene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated polyisoprene, Examples thereof include hydrogenated polybutadiene. These insulating organic polymers can be used alone or in admixture of two or more. Among these, the alicyclic olefin resin can be suitably used because the frequency dependence of the dielectric constant is small.

In the present invention, as the inorganic fine particles of the first insulating layer, usually inorganic metal oxides or nanoparticles of a high dielectric insulator are preferably used. The inorganic metal oxide nanoparticles are not particularly limited, and examples thereof include nanoparticles such as Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , CeO _2, and ZrO ₂ . The nanoparticles of high dielectric insulator is not particularly limited, for _{example, Ba 4 Sr 1-d TiO} 3 ( wherein, d satisfies 0 <d <1;. BST ), PbZr e Ti 1- _e O ₃ (wherein _e satisfies 0 <e <1; PZT), Bi ₄ Ti ₃ O ₁₂ , BaMgF ₄ , SrBi ₂ (Ta _1-f Nb _f ) ₂ O ₉ (where f is 0 <f <1 is satisfied), Ba (Zr _1-g Ti _g ) O ₃ (wherein g satisfies 0 <g <1; BZT), BaTiO ₃ , SrTiO ₃ and Bi ₄ Ti ₃ O Nanoparticles such as ₁₂ . _{Incidentally, Ba d Sr 1-d TiO} 3 is what is referred to as Barium Strontium Titanate, usually, BaTiO ₃ and SrTiO ₃ in a weight ratio: in _{(BaTiO 3 SrTiO 3) 1:} 9~9: 1 in It is obtained by mixing at a ratio. These nanoparticles can be used alone or in admixture of two or more. As said nanoparticle, a thing with a dielectric constant of 5 or more is preferable, From this viewpoint, the nanoparticle of a highly dielectric insulator is used suitably normally. The average particle diameter of the nanoparticles is usually 50 nm or less, preferably 1 to 50 nm, more preferably 1 to 30 nm. The dielectric constant can be measured according to JIS K 6911, and the average particle diameter can be measured by a dynamic light scattering method.
The relative dielectric constant of the first insulating layer can be easily adjusted, for example, by appropriately selecting the quantitative ratio between the insulating organic polymer and the inorganic fine particles. As content of the inorganic fine particle in a 1st insulating layer, it is 50-500 weight part normally with respect to 100 weight part of said insulating organic polymers, and 100-300 weight part is preferable.

  The second insulating layer is formed using an alicyclic olefin resin having a polar group (hereinafter referred to as a polar group-containing alicyclic olefin resin). The alicyclic olefin resin is excellent in adhesion, planarization, low water absorption, and the like, and the second insulating layer greatly contributes to the performance expression of the organic thin film transistor of the present invention. The relative dielectric constant of the second insulating layer can be easily adjusted, for example, by appropriately selecting and using a polar group-containing alicyclic olefin resin described later.

  In the organic thin film transistor of the present invention, the method for forming the gate insulating layer is not particularly limited. The gate insulating layer can be formed by, for example, forming the first insulating layer and laminating the second insulating layer on the insulating layer according to the method described below.

  The first insulating layer is preferably formed using a resin composition a containing an insulating organic polymer and inorganic fine particles. Although it does not specifically limit as the resin composition a, Usually, what contains a polar group containing alicyclic olefin resin, an inorganic fine particle, a crosslinking agent, and a solvent is used suitably. Hereinafter, the composition used for forming the first insulating layer is referred to as a first coating liquid.

  As a preferable example of the polar group-containing alicyclic olefin resin, a polar group-containing alicyclic olefin resin having a structural unit represented by the following formula (I) and / or a structural unit represented by the formula (II): Is mentioned. Preferred examples of the inorganic fine particles include the nanoparticles. Preferred examples of the crosslinking agent include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, polyphenol having two or more epoxy groups, preferably three or more epoxy groups. Polyfunctional epoxy compounds such as type epoxy resins, cycloaliphatic epoxy resins, aliphatic glycidyl ethers, and epoxy acrylate polymers. Examples of the solvent include a monoalkylene glycol solvent; a polyalkylene glycol solvent; a monoalkylene glycol alkyl ester solvent; a polyalkylene glycol alkyl ester solvent; a monoalkylene glycol diester solvent; a polyalkylene glycol diester solvent;

  The resin composition a used for forming the first insulating layer can be produced according to a known method. The solid content concentration of the resin composition a can be appropriately selected in consideration of a desired thickness of the resin film, a coating method, and the like, but is preferably 5 to 40% by weight. The prepared resin composition a is usually preferably used after removing foreign matters using a filter having a pore diameter of 0.1 to 5 μm.

  The second insulating layer is formed by mixing a polar group-containing alicyclic olefin resin and an arbitrary cross-linking agent and solvent shown as a preferable example of the cross-linking agent and the solvent used in the resin composition a. It is preferable to form using the resin composition b. The polar group-containing alicyclic olefin resin is preferably a polar group-containing alicyclic olefin resin having a structural unit represented by the following formula (I) and / or a structural unit represented by the formula (II). The solid content concentration of the resin composition b is usually 2 to 10% by weight. Hereinafter, the composition used for forming the second insulating layer is referred to as a second coating liquid.

  In the first coating liquid and the second coating liquid described above, if desired, colorants such as pigments and dyes, adhesion assistants, dispersants, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, You may make it contain well-known compounding agents, such as anti-aging agent and a lubricant, suitably.

The method for forming the first insulating layer is not particularly limited, and examples thereof include a coating method and a film lamination method.
The coating method is a method in which the first coating liquid is applied on the substrate on which the gate electrode is formed, and then the solvent is removed by heating and drying. Examples of the method for applying the first coating liquid on the substrate include spraying, spin coating, roll coating, die coating, doctor blade, spin coating, bar coating, and screen printing. Can do. Although it can select suitably according to the kind and compounding ratio of each component, heat drying temperature is 30-150 degreeC normally, and heat drying time is 0.5 to 90 minutes normally.
In the film laminating method, the first coating liquid is applied on a resin film, a metal film, etc., and then the solvent is removed by heating and drying to obtain a B stage film, and then the B stage film is laminated on the substrate. It is a method to do. The heating and drying conditions can be appropriately selected according to the type and mixing ratio of each component, but the heating temperature is usually 30 to 150 ° C., and the heating time is usually 0.5 to 90 minutes. . Film lamination can be performed using a pressure bonding machine such as a pressure laminator, press, vacuum laminator, vacuum press, roll laminator and the like.

  When the first coating liquid contains a cross-linking agent, it is preferable to perform a cross-linking reaction of the resin after obtaining the resin film. The method of crosslinking the resin film formed on the substrate can be appropriately selected according to the type of the crosslinking agent used, but is usually performed by heating. The heating can be performed using, for example, a hot plate or an oven. The heating temperature is usually preferably 180 to 250 ° C., and the heating time can be appropriately selected according to the size, thickness, equipment used, and the like of the resin film. For example, when a hot plate is used, it is usually preferably 5 to 60 minutes, and when an oven is used, it is usually preferably 30 to 90 minutes. If desired, the heating can be performed in an inert gas atmosphere such as nitrogen, argon, helium, neon, xenon, krypton, or the like.

The second insulating layer is formed on the first insulating layer by using, for example, a coating method or a film lamination method in the same manner as the method for forming the first insulating layer using the second coating liquid. By forming the insulating layer using the second coating liquid containing the polar group-containing alicyclic olefin resin, a second insulating layer having excellent flatness can be easily obtained. Next, when an organic semiconductor layer is formed on the second insulating layer, the interface between the second insulating layer and the organic semiconductor layer satisfies the predetermined arithmetic average roughness Ra.
The arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is the same as the arithmetic average roughness Ra of the surface of the insulating layer after the second insulating layer is formed. By measuring the arithmetic average roughness Ra of the surface of the second insulating layer, the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer can be known. On the other hand, after the organic semiconductor layer is formed on the second insulating layer, a cross section of the organic thin film transistor in a direction perpendicular to the insulating layer and the organic semiconductor layer is obtained, and the FIB is used based on the cross section. The arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer can be measured.

  The above-described method for forming the first and second insulating layers is a so-called wet method. For example, according to a known method, a vacuum deposition method, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method are used. Alternatively, the insulating layer may be formed by a so-called dry method such as ion plating, chemical vapor deposition (CVD), sputtering, plasma polymerization, electrolytic polymerization, or chemical polymerization.

  In the present invention, the alicyclic olefin resin suitably used for forming the substrate and the gate insulating layer is a polymer having a cycloalkane structure in the main chain and / or side chain. The alicyclic olefin resin polymerizes an olefin monomer having a ring structure and a carbon-carbon double bond (hereinafter referred to as a cyclic olefin monomer), and if necessary, an unsaturated bond moiety and / or It is obtained by hydrogenating an aromatic ring part, and has a cyclic olefin monomer unit as a structural unit. In the present specification, the cyclic olefin monomer unit includes a cyclic olefin monomer unit after hydrogenation. Examples of the ring structure in the cyclic olefin monomer include a cycloalkane structure, a cycloalkene structure, and an aromatic ring structure. In addition, the ring structure may be monocyclic or polycyclic (fused polycyclic, bridged ring, combined polycyclic, etc.). The number of carbon atoms constituting the ring structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, and more preferably 5 to 15.

  The alicyclic olefin resin may have a monomer unit other than the cyclic olefin monomer as a structural unit. The proportion of the cyclic olefin monomer unit in all the constituent monomer units of the alicyclic olefin resin is appropriately selected as desired, but is usually 30 to 100% by weight, preferably 50 to 100% by weight, more preferably. Is 70 to 100% by weight.

A polar group-containing alicyclic olefin resin is suitable as the alicyclic olefin resin. The polar group-containing alicyclic olefin resin is used as an essential component of the second insulating layer. The proportion of polar groups present in the polar group-containing alicyclic olefin resin is not particularly limited. The polar group is usually 30 to 100 mol%, preferably 50 to 100 mol%, more preferably 70 to 100 mol% of the constituent monomer in the total number of constituent monomer units of the alicyclic olefin resin. It should be present in the unit. There is no particular limitation on the type and number of polar groups present in each constituent monomer unit.

Examples of the polar group include a carboxyl group (hydroxycarbonyl group), an alkoxycarbonyl group, a dicarboxylic anhydride group (carbonyloxycarbonyl group), a hydroxyl group (hydroxyl group), a nitrile group, an epoxy group, an oxetanyl group, and an imide group. Etc.
For example, as an example where the polar group is a hydroxyl group, a substituent containing a phenolic hydroxyl group such as a hydroxyphenyl group or a hydroxyphenylalkyl group; a substitution containing an alcoholic hydroxyl group such as a hydroxyalkyl group, a hydroxyalkoxyl group or a hydroxyalkoxycarbonyl group A hydroxymethoxy group and a hydroxyethoxyl group are preferable.
Examples of the polar group being an imide group include an N-phenyldicarboximide group.

  The alicyclic olefin resin may have only one kind of polar group as described above, may have two or more kinds, and preferably has two or more kinds. Among these, it is more preferable to have both a carboxyl group and an imide group.

  As the polar group-containing alicyclic olefin resin in the present invention, for example, those having a structural unit represented by the following formula (I) and / or a structural unit represented by the formula (II) are suitable. Those having both the structural units are more preferred.

Wherein (I), R ¹ ~R ⁴ are each independently a hydrogen atom or -X _n -R '(X is a divalent organic group, n is 0 or 1, R' is , An optionally substituted alkyl group, an optionally substituted aromatic group, or a polar group), and at least one of R ^{1 to} R ⁴ is R ′. Is a polar group —X _n —R ′, and m is an integer of 0-2. ]

[In the formula (II), R ⁵ and R ⁶ together with the two carbon atoms to which they are bonded contain an oxygen atom or a nitrogen atom which may have a substituent, or It forms a membered heterocyclic structure, and k is an integer of 0-2. ]

  In the general formula (I), examples of the divalent organic group represented by X include a methylene group, an ethylene group, and a carbonyl group. The alkyl group which may have a substituent represented by R ′ is usually a linear or branched alkyl group having 1 to 7 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, An isopropyl group etc. are mentioned. The aromatic group that may have a substituent is usually an aromatic group having 6 to 10 carbon atoms, and examples thereof include a phenyl group and a benzyl group. Examples of the polar group include a carboxyl group, an alkoxycarbonyl group, a hydroxyl group, a nitrile group, an epoxy group, and an oxetanyl group. The alkoxycarbonyl group is usually an alkoxycarbonyl group having a linear or branched alkyl chain portion having 1 to 7 carbon atoms which may have a substituent, such as a methoxycarbonyl group, an ethoxycarbonyl group, An isobutoxycarbonyl group etc. are mentioned. Examples of substituents for these groups include alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl; phenyl, xylyl, tolyl, And aryl groups having 6 to 12 carbon atoms such as naphthyl group.

In the general formula (II), R ⁵ and R ⁶ are formed together with two carbon atoms to which they are bonded to each other, and may contain an oxygen atom or a nitrogen atom which may have a substituent 3 Examples of the membered heterocyclic structure include an epoxy structure. In addition, as a 5-membered heterocyclic structure formed by including an oxygen atom or a nitrogen atom, R ⁵ and R ⁶ together with two carbon atoms to which they are bonded may have a substituent, Examples thereof include a dicarboxylic anhydride structure [—C (O) —O—C (O) —] and a dicarboximide structure [—C (O) —N—C (O) —]. As a substituent of an oxygen atom or a nitrogen atom, a phenyl group, a naphthyl group, an anthracenyl group etc. are mentioned, for example.

  The structural unit represented by the formula (I) and the structural unit represented by the formula (II) are both cyclic olefin monomer units. The ratio of the structural unit represented by the formula (I) and / or the structural unit represented by the formula (II) in the total structural units of the polar group-containing alicyclic olefin resin is usually 30 to 100 weights. %, Preferably 50 to 100% by weight, more preferably 70 to 100% by weight. When both structural units are included, the quantitative ratio of the structural unit represented by the formula (I) and the structural unit represented by the formula (II) [the structural unit of the formula (I): the structure of the formula (II) The unit] is preferably 10:90 to 90:10 by weight, and more preferably 50:50 to 80:20.

  Other examples of the polar group-containing alicyclic olefin resin suitably used in the present invention include, for example, a polymer of a monocyclic cycloalkene and a hydride thereof having the polar group; an alicyclic conjugated diene monomer. And polymers thereof and hydrides thereof; polymers of vinyl alicyclic hydrocarbon monomers and hydrides thereof; hydrides of aromatic rings of polymers of aromatic vinyl compounds; and the like.

  The polar group-containing alicyclic olefin resin is, for example, a cyclic olefin monomer having a polar group (hereinafter referred to as a polar group-containing cyclic olefin monomer), or a polar group-containing cyclic olefin monomer and the cyclic olefin. It can be obtained by subjecting the monomer and other polymerizable monomer to addition polymerization or ring-opening polymerization according to a known method, and optionally hydrogenating. The polar group may be present in the other monomer in addition to the cyclic olefin monomer. When the polar group is present in the other monomer, the polar group may not be present in the cyclic olefin monomer.

Examples of the polar group-containing cyclic olefin monomer include 5-hydroxycarbonylbicyclo [2.2.1] hept-2-ene, 5-methyl-5-hydroxycarbonylbicyclo [2.2.1] hept-2. -Ene, 5-carboxymethyl-5-hydroxycarbonylbicyclo [2.2.1] hept-2-ene, 8-methyl-8-hydroxycarbonyltetracyclo
[4.4.0.1 ^2,5 .1 ^7,10] dodeca-3-ene, 8-carboxymethyl-8-hydroxycarbonyl tetracyclo [4.4.0.1 ^2,5 .1 ^7,10 ] Cyclic olefin monomers having one carboxyl group such as dodec-3-ene; 5-exo-6-endo-dihydroxycarbonylbicyclo [2.2.1] hept-2-ene, 8-exo-9- end - dihydroxy carbonyl tetracyclo [4.4.0.1 ^{2, 5} .1 ^7,10] dodeca-3-ene, bicyclo [2.2.1] hept-2-ene-5,6-dicarboxylic acid anhydride things, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodeca-3-ene-8,9-dicarboxylic anhydride, hexacyclo [6.6.1.1 ^3,6 .1 ^{10 13} .0 ^2,7 .0 ^9,14] heptadec-4-ene-11,12-cyclic olefin monomer having two carboxyl groups, such as dicarboxylic anhydrides; 5- (4-hydroxyphenyl) bicyclo [2.2.1] hept-2-ene, 5-methyl-5- (4-hydroxyphenyl) bicyclo [2.2.1] hept-2-ene, 5-carboxymethyl -5- (4-hydroxyphenyl) bicyclo [2.2.1] hept-2-ene, 8-methyl-8- (4-hydroxyphenyl) tetracyclo [4.4.0.1 ^{2, 5} .1 ^{7 , 10]} dodeca-3-ene, 8-carboxy-methyl-8- (4-hydroxyphenyl) tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dec-3-one hydroxy, such ene And cyclic olefin monomers having a phenyl group; N-substituted imide group-containing cyclic olefin monomers such as N- (4-phenyl)-(5-norbornene-2,3-dicarboximide); and the like. These monomers can be used alone or in admixture of two or more.

  Examples of other monomers that can be polymerized with the cyclic olefin monomer include ethylene; propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, and 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- Α-C2-C20 such as 1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene Olefin; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and 1,7-octadiene, and those substituted with polar groups Examples include monomer substitution products. These monomers can be used alone or in admixture of two or more.

  The cycloaliphatic olefin resin used in the present invention has a polystyrene-reduced weight average molecular weight (Mw) of 1,000 to 1,000,000 as measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent. It is preferably 5,000 to 500,000, more preferably 10,000 to 250,000. When the weight average molecular weight (Mw) of the alicyclic olefin resin is 1,000 to 1,000,000, it is possible to form a resin film in which wet heat resistance, adhesion, surface smoothness and the like are balanced. As the molecular weight distribution of the alicyclic olefin resin, the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by gel permeation chromatography using THF as a solvent is 5 or less. Preferably, it is 4 or less, more preferably 3 or less.

The organic thin film transistor of the present invention can further be provided with a protective layer. By providing the protective layer, deterioration of the organic semiconductor layer due to air and deterioration due to a coating solvent used at the time of manufacturing can be prevented, and deterioration of characteristics as a transistor can be suppressed.
As the protective layer, it is preferable to use a material that does not adversely affect the organic semiconductor layer during the manufacturing process of the organic thin film transistor or after the manufacturing. Examples of the material used for the protective layer include acrylic polymers such as polymethyl methacrylate and poly 2-hydroxyethyl methacrylate, polyvinyl alcohol, polyacrylic acid, polyacrylamide, urethane resin, polyester resin, polyolefin resin, and copolymers thereof. It can be appropriately selected from the above.
Examples of other materials for the protective layer include inorganic oxides, inorganic nitrides, and other materials containing inorganic substances. Examples of 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, titanate Examples include strontium, barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Among these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide can be preferably used. Examples of the inorganic nitride include silicon nitride and aluminum nitride. Examples of other inorganic substances include smectite layered silicate compounds such as ionite, saponite, hectorite, sauconite, stevensite, spinolite, montmorillonite, beidellite, nontronite, and bolconscoreite.

  In the present invention, the method for forming the protective layer is not particularly limited, and for example, vacuum deposition, molecular beam epitaxial growth, ion cluster beam, low energy ion beam, ion plating, chemical vapor deposition (CVD) ), Dry methods such as sputtering method, atmospheric pressure 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., A wet method such as a method by patterning such as printing or ink jet can be used. Further, a heating and baking process can be added to the film forming process. The thickness of the protective layer is preferably 0.1 to 10 μm.

  The organic thin-film transistor of this invention is used suitably for manufacture of flat display apparatuses, such as a liquid crystal display device and an organic electroluminescent display apparatus, for example.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
The first insulating layer is formed of a mixture of barium titanate fine particles and a polar group (carboxyl group; hereinafter the same) -containing alicyclic olefin resin, and the second insulating layer is a polar group-containing alicyclic olefin resin. The organic thin-film transistor currently formed by this was produced.
8- carboxy tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodeca-3-ene 58.4 wt%, N-phenyl - (5-norbornene-2,3-dicarboximide) Hydrogenated product of copolymer of 38.9% by weight and 1,5-hexadiene 2.7% by weight [Nippon Zeon Co., Ltd.], polyfunctional epoxy compound having an alicyclic structure as a crosslinking agent [Daicel Chemical Industry Co., Ltd., EHPE3150 (product name), molecular weight of about 2,700, number of epoxy groups 15] 25 parts by weight, (1,2,2,6,6-pentamethyl-4-piperidyl / tridecyl)- 1,2,3,4-butanetetracarboxylate 5 parts by weight, γ-glycidoxypropyltrimethoxysilane 5 parts by weight as an adhesion aid, barium titanate having an average particle size of 30 nm as inorganic fine particles [Kyoritsu Material Co., Ltd. Alkoxide method titanic acid 50 parts by weight of a lithium and a silicone surfactant [Shin-Etsu Chemical Co., Ltd., KP341 (product name)] 0.05 parts by weight were mixed, and 157 parts by weight of diethylene glycol ethyl methyl ether and N-methyl-2-pyrrolidone were mixed. 8 parts by weight was added and mixed by stirring to prepare a first coating solution. The relative dielectric constant of the resin film containing barium titanate formed from the first coating solution was measured at 25 ° C. and 100 kHz using an impedance analyzer [Toyo Technica Co., Ltd., Model 1260]. there were.
The second coating solution was prepared in the same manner as the first coating solution except that barium titanate was not used. When the relative dielectric constant of the resin film formed from the second coating solution was measured in the same manner, it was 2.8.
On a glass substrate of 25 mm × 10 mm × 1 mm [Corning, Corning 1737 (product name)], the degree of vacuum is less than 1 × 10 ⁻² Pa, the substrate temperature is room temperature, aluminum is deposited to a film thickness of 200 nm, and the gate electrode Formed.
On this glass substrate, the above-mentioned first coating solution was spin-coated at a rotation speed of 2,000 rpm for 30 seconds, the solvent was evaporated, and prebaked at 85 ° C. for 2 minutes using a hot plate, A first insulating layer was formed and further post-baked by heating at 230 ° C. for 15 minutes using an oven.
On the 1st insulating layer, said 2nd coating liquid was spin-coated for 30 second at the rotation speed of 5,000 rpm, the solvent was evaporated, and the 2nd insulating layer with a film thickness of 200 nm was formed. When the arithmetic average roughness Ra of the second insulating layer was measured using a focused ion beam apparatus (FIB) [manufactured by Hitachi, Ltd., FB-2100], it was 3 nm.
On the second insulating layer, pentacene was deposited to a film thickness of 50 nm with a degree of vacuum of less than 1 × 10 ⁻³ Pa, a substrate temperature of room temperature, a deposition temperature of 185 ° C., a deposition rate of 0.06 nm / s. Thus, an organic semiconductor layer was formed. Further, the organic semiconductor layer is covered with a metal mask, and gold is deposited to a thickness of 200 nm at a vacuum of less than 1 × 10 ⁻² Pa, a substrate temperature of room temperature, and a source electrode and a drain electrode (W = 5 mm; L = 20 to 70 μm), and an organic thin film transistor was obtained.
About the obtained organic thin-film transistor, the electrical property was evaluated using the semiconductor tester [Corporation | KK ADVANTEST, R6425]. The leakage current was 1.0 × 10 ⁻¹⁰ A / cm ² and the on / off ratio was 1.0 × 10 ⁵ .
Example 2
An organic thin film transistor was produced in which the first insulating layer was formed of a mixture of barium titanate fine particles and an acrylic resin, and the second insulating layer was formed of a polar group-containing alicyclic olefin resin.
Barium titanate with an average particle size of 30 nm [Kyoritsu Material Co., Ltd., alkoxide] in a mixture of 100 parts by weight of an acrylic resin solution [Daicel Chemical Industries, Ltd., trade name “Cyclomer PACA200M”] and 400 parts by weight of propylene glycol monomethyl ether acetate [Method Barium Titanate] Using the first coating liquid obtained by mixing 80 parts by weight, the others were prepared according to Example 1 and evaluated.
The relative dielectric constant of the resin film containing barium titanate formed from the first coating solution was 16. The arithmetic average roughness Ra of the second insulating layer was 8 nm. The leakage current of the organic thin film transistor was 5.0 × 10 ⁻¹⁰ A / cm ² , and the on / off ratio was 5.0 × 10 ⁵ .

Comparative Example 1
An organic thin film transistor was produced in which the insulating layer was only one layer made of a polar group-containing alicyclic olefin resin that did not contain barium titanate fine particles.
8- carboxy tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodeca-3-ene 58.4 wt%, N-phenyl - (5-norbornene-2,3-dicarboximide) Hydrogenated product of copolymer of 38.9% by weight and 1,5-hexadiene 2.7% by weight [Nippon Zeon Co., Ltd.], polyfunctional epoxy compound having an alicyclic structure as a crosslinking agent [Daicel Chemical Industry Co., Ltd., EHPE3150 (product name), molecular weight of about 2,700, number of epoxy groups 15] 25 parts by weight, (1,2,2,6,6-pentamethyl-4-piperidyl / tridecyl)- 1,2,3,4-butanetetracarboxylate 5 parts by weight, γ-glycidoxypropyltrimethoxysilane 5 parts by weight as an adhesion aid and silicone surfactant [Shin-Etsu Chemical Co., Ltd., KP341 (product name )] 0.05 part by weight Stirred and mixed by adding 157 parts by weight of glycol ethyl methyl ether and N- methyl-2-pyrrolidone 8 parts by weight, to prepare a coating liquid. The relative dielectric constant measured at 25 ° C. and 100 kHz of the resin film containing no barium titanate formed from this coating solution was 2.8.
On a glass substrate of 25 mm × 10 mm × 1 mm [Corning, Corning 1737 (product name)], the degree of vacuum is less than 1 × 10 ⁻² Pa, the substrate temperature is room temperature, aluminum is deposited to a film thickness of 200 nm, and the gate electrode Formed.
This glass substrate is spin-coated with the above coating solution at a rotation speed of 1,700 rpm for 30 seconds, the solvent is evaporated, and prebaked at 85 ° C. for 2 minutes using a hot plate to form an insulating layer having a thickness of 300 nm. Then, it was further post-baked by heating at 230 ° C. for 15 minutes using an oven to form an insulating layer. In the same manner as in Example 1, the arithmetic average roughness Ra of the insulating layer was measured and found to be 3 nm.
On the insulating layer, pentacene is evaporated to a thickness of 50 nm with a degree of vacuum of less than 1 × 10 ⁻³ Pa, a substrate temperature of room temperature, a deposition temperature of 185 ° C., a deposition rate of 0.06 nm / s, and organic A semiconductor layer was formed. Further, the organic semiconductor layer is covered with a metal mask, and gold is deposited to a thickness of 200 nm at a vacuum of less than 1 × 10 ⁻² Pa, a substrate temperature of room temperature, and a source electrode and a drain electrode (W = 5 mm; L = 20 to 70 μm), and an organic thin film transistor was obtained.
About the obtained organic thin-film transistor, it carried out similarly to Example 1, and evaluated the electrical property. The leakage current was 2.0 × 10 ⁻⁹ A / cm ² and the on / off ratio was 1.0 × 10 ⁴ .
Comparative Example 2
An organic thin film transistor in which the first insulating layer was an acrylic resin containing no barium titanate fine particles and the second insulating layer was a polar group-containing alicyclic olefin resin was produced.
As the first coating liquid, an acrylic resin solution [manufactured by Daicel Chemical Industries, Ltd., trade name “Cyclomer PACA200M”] was used, and an organic thin film transistor was prepared according to Example 1 and evaluated.
The relative dielectric constant of the resin film not containing barium titanate formed from the first coating solution was 3.6. The arithmetic average roughness Ra of the second insulating layer was 3 nm. The leakage current of the organic thin film transistor was 5.0 × 10 ⁻⁸ A / cm ² , and the on / off ratio was 1.0 × 10 ⁴ .
Comparative Example 3
An organic thin film transistor was produced in which the first insulating layer was formed of a mixture of barium titanate fine particles and an acrylic resin, and the second insulating layer was formed of an acrylic resin.
As a 1st coating liquid, barium titanate with an average particle diameter of 30 nm is added to a mixed solution of 100 parts by weight of an acrylic resin solution [manufactured by Daicel Chemical Industries, Ltd., trade name “Cyclomer PACA200M”] and 400 parts by weight of propylene glycol monomethyl ether acetate. [Kyoritsu Material Co., Ltd., alkoxide-based barium titanate] Using a mixture of 80 parts by weight, an acrylic resin solution [manufactured by Daicel Chemical Industries, trade name “Cyclomer PACA200M”] is used as the second coating liquid. According to Example 1, an organic thin film transistor was produced and evaluated.
The relative dielectric constant of the resin film containing barium titanate formed from the first coating solution was 18. The arithmetic average roughness Ra of the second insulating layer was 50 nm. The leakage current of the organic thin film transistor was 6.0 × 10 ⁻¹⁰ A / cm ² , and the on / off ratio was 1.0 × 10 ⁵ .
The results of Examples 1-2 and Comparative Examples 1-3 are shown in Table 1.

As shown in Table 1, the gate insulating layer has a two-layer structure, and the first insulating layer in contact with the gate electrode is formed of a mixture of barium titanate nanoparticles and a predetermined insulating organic polymer. The dielectric constant of the first insulating layer is higher than the dielectric constant of the second insulating layer in contact with the organic semiconductor layer, and the second insulating layer is formed of a polar group-containing alicyclic olefin resin, The organic thin film transistors of Example 1 and Example 2 in which the arithmetic average roughness Ra of the layer (the same as the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer) is 3 nm or 8 nm have leakage currents Small, large on / off ratio, and excellent performance.
In contrast, the organic thin film transistors of Comparative Example 1 and Comparative Example 2 in which the first insulating layer does not contain inorganic fine particles and the second insulating layer are formed of an acrylic resin, and the arithmetic average roughness Ra of the insulating layer. The organic thin film transistor of Comparative Example 3 having a thickness of 50 nm has a large leakage current and / or a small on / off ratio.

  According to the organic thin film transistor of the present invention, for example, an excellent flat display device with low power consumption and high contrast can be manufactured.

It is typical sectional drawing of the one aspect | mode of the organic thin-film transistor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 1st insulating layer 4 2nd insulating layer 5 Organic-semiconductor layer 6 Source electrode 7 Drain electrode 8 Protective layer

Claims (7)

In an organic thin film transistor having a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode on a substrate, the gate insulating layer is in contact with the gate electrode, and the second insulating layer is in contact with the organic semiconductor layer. An insulating layer,
(A) the first insulating layer is formed of a mixture of an insulating organic polymer and inorganic fine particles, and the relative dielectric constant of the first insulating layer is higher than the relative dielectric constant of the second insulating layer;
(B) The second insulating layer is formed of an alicyclic olefin resin having a polar group, and the arithmetic average roughness Ra of the interface between the second insulating layer and the organic semiconductor layer is 10 nm or less.
An organic thin film transistor characterized by the above.   The organic thin film transistor according to claim 1, wherein the thickness of the gate insulating layer is 10 to 500 nm.   The organic thin-film transistor according to claim 1 or 2, wherein the relative dielectric constant of the first insulating layer is 5 or more and the relative dielectric constant of the second insulating layer is 4 or less.   The organic thin-film transistor of any one of Claims 1-3 whose content of the inorganic fine particle in a 1st insulating layer is 50-500 weight part with respect to 100 weight part of insulating organic polymers.   The organic thin film transistor according to any one of claims 1 to 4, wherein the inorganic fine particles of the first insulating layer are nanoparticles of an inorganic metal oxide or a high dielectric insulator. The alicyclic olefin resin having a polar group in the second insulating layer is represented by the following general formula (I):

[Wherein, R ^{1 to} R ⁴ are each independently a hydrogen atom or —X _n —R ′ (X is a divalent organic group, n is 0 or 1, and R ′ is a substituent. Or an aromatic group which may have a substituent, or a polar group. At least one of R ^{1 to} R ⁴ is such that R ′ is a polar group. -X _n -R ', and m is an integer of 0-2. ]
And / or the following general formula (II):

[Wherein R ⁵ and R ⁶ are a 3-membered or 5-membered heterocyclic ring containing an oxygen atom or a nitrogen atom, which may have a substituent, together with two carbon atoms to which they are bonded. Forming a structure, k is an integer from 0 to 2; ]
The organic thin-film transistor of any one of Claims 1-5 which has a structural unit represented by these. The organic thin film transistor according to claim 1, further comprising a protective layer.

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