WO2007125899A1

WO2007125899A1 - Organic thin-film transistor

Info

Publication number: WO2007125899A1
Application number: PCT/JP2007/058813
Authority: WO
Inventors: Chiyoko Takemura; Shuichi Sugita; Katsura Hirai; Hiroshi Kita
Original assignee: Konica Minolta Holdings, Inc.
Priority date: 2006-04-26
Filing date: 2007-04-24
Publication date: 2007-11-08
Also published as: JP2007294719A

Abstract

An organic thin-film transistor which can be fabricated by a simple wet process, and has excellent transistor characteristics, and an excellent stability with time in the air or in a high humidity environment. The organic thin-film in which a gate electrode, a gate insulating layer, an organic semiconductor layer, a source electrode, and a drain electrode are provided over a substrate is characterized in that the film density of the organic semiconductor layer is 1.15 to 1.33 g/cm3.

Description

Specification

Organic thin film transistor

Technical field

[0001] The present invention relates to an organic thin film transistor.

Background art

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

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

Here, the TFT element is usually a semiconductor thin film such as a-Si (amorphous silicon) or p-Si (polysilicon) or a metal such as a source electrode, a drain electrode, or a gate electrode on a glass substrate. Manufactured by sequentially forming thin films on a substrate. The production of flat panel displays using TFTs usually requires high-precision photolithographic processes in addition to vacuum systems such as CVD and sputtering and thin film forming processes that require high-temperature processing processes. In addition, the cost burden is enormous, and the cost of these displays has become enormous with the recent demand for larger displays.

[0005] In recent years, research and development of organic TFT elements using organic semiconductor materials has been actively promoted as a technology to compensate for the disadvantages of conventional TFT elements (for example, Patent Documents 1 and 2 and Non-Patent Document 1) reference).

[0006] Since the organic TFT element described in the above document can be manufactured by a low-temperature process, it is possible to use a light and difficult-to-break resin substrate, and to use a resin film as a support. It is said that a responsive display can be realized (for example, see Non-Patent Document 2).

[0007] By using an organic semiconductor material that can be manufactured by a wet process such as printing or coating under atmospheric pressure, a display with excellent productivity and a very low cost can be realized. In addition, various organic thin film transistors using organic semiconductors have been proposed, and it is described that they can be produced by a simple method by printing or an ink jet method (see, for example, Patent Document 1).

[0008] The characteristics of an organic transistor or a field effect transistor are that the current when a voltage is applied to the gate electrode (hereinafter referred to as on-current) is large, and the current when no voltage is applied to the on-current and the gate electrode. It is required that the ratio of (off-state current and hereafter) is large.

In order to increase the on-state current in the conventional transistor, it is necessary to increase the carrier mobility in the channel region or increase the number of carriers accumulated in the channel region. However, when the carrier mobility in the channel region is increased, the off-current increases and the desired on-Z off ratio cannot be obtained.

[0010] Furthermore, the organic semiconductor layer deteriorates when left in the air, and the characteristics of the device as a transistor.

Has a problem that it decreases. As one means for solving such a problem, an organic semiconductor layer or an organic thin film transistor is used as a sealing film that also has a polymer material force such as an inorganic material such as a key oxide or a silicon nitride, or a polybutyl alcohol. Therefore, it is proposed to protect (see, for example, Patent Document 3 and Patent Document 4). However, even these sealing technologies are insufficient to maintain the stability of organic thin-film transistors under high humidity, and there are almost no proposals for technologies that have improved the temporal stability under high humidity in this way. The current situation is that nothing has been done.

Patent Document 1: JP-A-10-190001

Patent Document 2: JP 2000-307172 A

Patent Document 3: JP 2002-314093 A

Patent Document 4: Special Table 2003-525521

Non-Patent Document 1: Advanced Material, 2002, No. 2, p. 99 (Review) Non-Patent Document 2: SID '02 Digest p57 Disclosure of the invention

Problems to be solved by the invention

[0011] The present invention has been made in view of the above circumstances, and a first object thereof is to provide an organic thin film transistor that can be manufactured by a simple wet process and has excellent transistor characteristics. The purpose of 2 is to provide an organic thin film transistor having excellent temporal stability even in the air or under high humidity.

Means for solving the problem

[0012] The above-described object of the present invention is achieved by the following configurations.

[0013] 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 film density of the organic semiconductor layer is 1.15 to 1

An organic thin film transistor characterized by being 33 g / cm ³ .

[0014] 2. The organic thin film transistor according to 1, wherein the organic semiconductor layer is characterized by containing ^{^{1 X 10- 2 ~1 X 10 3}} ppm of organic solvent.

[0015] 3. At least one organic semiconductor material constituting the organic semiconductor layer is represented by the following general formula:

3. The organic thin film transistor according to 1 or 2, which is a compound represented by (1).

[0016] [Chemical formula 1] General formula (1)

(In the formula, R to R represent a hydrogen atom or a substituent, and Z and Z are substituted or unsubstituted aromatic.

1 6 1 2

Represents an aromatic hydrocarbon ring or a substituted or unsubstituted aromatic heterocyclic ring, and nl and n2 each represents an integer of 0 to 3. )

4. The organic thin film transistor according to 3, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2). [0018] [Chemical 2]

—General formula (

[In the formula, R and R represent a hydrogen atom or a substituent, and Z and Z represent a substituted or unsubstituted fragrance.

7 8 1 2

5. The substituent R, R in the general formula (2) is represented by the following general formula (3)

7 8

The organic thin film transistor according to 4.

[0020] [Chemical 3] General formula

[In the formula, R to R represent a substituent, and X represents Si, Ge, or Sn.]

9 11

6. The organic thin film transistor according to any one of 1 to 5, wherein the organic semiconductor layer is a layer formed by a coating method using an organic solvent.

The invention's effect

According to the present invention, it is possible to provide an organic thin film transistor that can be produced by a simple wet process, has excellent transistor characteristics, and has excellent temporal stability even in the atmosphere or at high temperatures and high humidity.

Brief Description of Drawings

[0023] 圆 1] is a diagram showing a configuration example of an organic thin film transistor of the present invention. FIG. 2 is an example of a schematic equivalent circuit diagram of the organic thin film transistor of the present invention.

Explanation of symbols

[0024] 1 Organic semiconductor layer

2 Source electrode

3 Drain electrode

4 Gate electrode

5 Insulation layer

6 Support

7 Gate bus line

8 Sourcenos line

9 Board

10 TFT sheet

11 Organic TFT

12 Output element

13 Storage capacitor

14 Vertical drive circuit

15 Horizontal drive circuit

BEST MODE FOR CARRYING OUT THE INVENTION

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

[0026] Film density of organic semiconductor layer

The film density of the organic semiconductor layer according to the present invention is 1.15-: L 33 gZcm ³ , more preferably 1.16-1.31 g / cm ³ . As a result, it is possible to provide an organic thin film transistor having excellent transistor characteristics and excellent stability over time even in the air or at high temperatures and high humidity.

[0027] The method for measuring the film density of the present invention will be described.

[0028] The film density of the present invention can be determined by an X-ray reflectivity measurement method. When X-rays are incident on the surface of a material with a flat surface like Si, total reflection occurs at an incident angle of Θc or less. This angle is called the total reflection critical angle (hereinafter referred to as the critical angle). The critical angle varies depending on the electron density (refractive index) of the material, which is as small as 0.22 ° for Si with respect to CuK α-rays. According incidence angle of the X-ray is greater than this angle, the X-ray enters the increasingly deep material, the material having the ideal plane decreases sharply in proportion to the theta ⁴ at an angle of more than theta c. When another material with a different electron density is uniformly stacked on a substrate of such a material, the reflected X-rays of the substrate and thin film interface and the thin film surface force interfere with each other, strengthening or weakening each other, Vibration due to X-ray interference appears on the reflectance profile. This phenomenon was first observed by Kiessig in 1931, and this oscillation is called Kiessig fringe. The period of this vibration has information on the thickness of the film, and the amplitude of the vibration has angle dependence and includes information on the density of the film, the roughness of the surface and the interface. The X-ray reflectivity measurement method is a method for determining the film thickness, density, surface or interface roughness by analyzing this profile.

[0029] More specifically, the reflectance at an extremely low angle, for example, 0.2 to 2 degrees, is measured, and the obtained reflectance curve is fitted to the reflectance equation of the multilayer film sample obtained from the Fresnel equation. By doing so, the film density can be obtained. Refer to L. G. Parratt, Phis. Rev., 95, 359 (1954) for the fitting method.

[0030] Specifically, the X-ray generation source targets copper and operates at 50 kV-300 mA. X-rays monochromatized with a multilayer mirror and Ge (111) channel cut monochromator are used. Measurements are made using software ATX—Crystal Guide Ver. 6. 5. 3. 4 and after halving and alignment adjustment, 2 0 Ζ ω = 0 degree to 1 degree from 0.002 degree Zstep to 0.05 degree Zmin Scan with. After measuring the reflectance curve under the above measurement conditions, it can be obtained using GXRR Ver. 2.1.0.0 analysis software manufactured by Rigaku Corporation.

[0031] << Organic solvent >>

(Organic solvent content)

The organic semiconductor layer according to the present invention, the organic solvent ^{^{1 X 10- 2 ~1 X 10 3}} ppm contained, rather preferably the organic solvent 0. 1: containing LOOppm.

[0032] The amount of the organic solvent contained in the organic semiconductor layer according to the present invention is measured by gas chromatography mass spectrometry (PT—GCZMS) equipped with a purge & trap sampler. be able to. Specifically, an organic thin-film transistor element of lOcm x IOcm square was fabricated, and the organic solvent contained in the organic semiconductor layer was adsorbed to the gas recovery chamber and the organic gas adsorption tube (TENAX GR), and PT-GCZMS measurement was performed. Went. The solvent concentration was determined from a calibration curve prepared using a reference sample with a known concentration.

[0033] (Type of organic solvent)

The organic solvent according to the present invention is not particularly limited, but aromatic hydrocarbons, aromatic halogenated hydrocarbons that are preferred are aromatic hydrocarbons, aromatic halogenated hydrocarbons, aliphatic hydrocarbons or aliphatic halogenated hydrocarbons. More preferred are hydrogen or aliphatic hydrocarbons.

[0034] Examples of the organic solvent for the aromatic hydrocarbon include, but are not limited to, toluene, xylene, mesitylene, methylnaphthalene, and the like.

Examples of the organic solvent for the aromatic halogenated hydrocarbon include, for example, black benzene, bromobenzene, iodine benzene, o dichroic benzene, m-dichroic benzene, o dibromobenzene, m-dibromobenzene, o jodobenzene, m-Jodobenzene, chlorotolenene, bromotolenene, odonotolene, dichlorotonolene, jib mouth motonolene, difluoronorotolene, chloroxylene, bromoxylene, odoxylene, chloroethanolobenzene, bromoethenolebenzene, odode Forces that can include ethynolebenzene, dichloroethinolebenzene, dibu-methyl methacrylate, chlorocyclopentagen, chlorocyclopentagen, etc. The present invention is not limited to these.

[0036] Examples of the organic solvent for the aliphatic hydrocarbon include octane, 4-methylheptane, 2-methylheptane, 3 methylheptane, 2,2 dimethylhexane, 2,3 dimethylhexane, and 2,4 dimethyl. Hexane, 2,5 Dimethylhexane, 3,3 Dimethylhexane, 3,4 Dimethylhexane, 3 Ethylhexane, 2, 2,3 Trimethylpentane, 2, 2,4 Trimethylpentane, 2, 3, 3 Trimethylpentane, 2, 3, 4 trimethylpentane, 2-methyl-3 ethylpentane, 3-methyl-3 ethylpentane, decane, 2, 2, 3, 3-tetramethyl hexane, 2, 2, 5, 5-tetramethyl hexane, 3, 3, 5 Trimethylheptane, Nonane, 2, 2, 5 Trimethylhexane, 4 Ethylheptane, 2, 3 Dimethylheptane, 2 Methyloctane, Dodecane, Hexane, 2-Methylpentane, 3-Methyl Pentane, 2, 2-dimethyl butane, 2, 3-dimethylbutane, heptane, hexane methyl , 3-Methylhexane, 2,2-Dimethylpentane, 2,3-Dimethylpentane, 2,4-Dimethylpentane, 3,3-Dimethylpentane, 3-Ethylpentane, 2,2,3-Trimethylbutane, etc. Cyclic aliphatic hydrocarbons such as cycloaliphatic hydrocarbons, cyclohexane, cyclopentane, methylcyclohexane, methylcyclopentane, p-menthane, decalin, cyclohexylbenzene and the like. However, it is not limited to these. As the aliphatic hydrocarbon used in the present invention, a cyclic aliphatic hydrocarbon is preferable.

[0037] Examples of the organic solvent for the aliphatic halogenated hydrocarbon include, for example, black mouth form, promophor, dichloromethane, dichloroethane, trichloroethane, difluoroethane, funoleo mouth mouth ethane, black mouth propane, dichloropropane, and black mouth pentane. The power that can include hexane and the like. The present invention is not limited to these.

[0038] These organic solvents used in the present invention may be used alone or in combination of two or more.

[0039] The organic solvent according to the present invention preferably has a boiling point of 50 to 250 ° C. In adjusting the amount of the organic solvent to be included in the organic semiconductor layer, if the boiling point of the organic solvent is lower than 50 ° C, the volatility becomes too high, so that a desired amount of the organic solvent is added to the organic semiconductor layer. When the temperature is higher than 250 ° C, it is necessary to expose the organic semiconductor layer at a higher temperature than necessary to adjust the amount of the organic solvent contained in the organic semiconductor layer to a desired amount. This results in deterioration of the semiconductor layer, which is not preferable.

[0040] << Organic thin film transistor >>

An organic thin film transistor includes a top gate type having a source electrode and a drain electrode connected by an organic semiconductor channel (active layer) on a support, and a gate electrode on the gate electrode via a gate insulating layer. First, it is roughly classified into a bottom gate type having a gate electrode and having a source electrode and a drain electrode connected by an organic semiconductor channel through a gate insulating layer. The organic thin film transistor of the present invention may be either a top gate type or a bottom gate type, and may be in any form.

[0041] (Organic semiconductor material)

The organic semiconductor material according to the present invention constituting the organic semiconductor channel is a semiconductor. Any organic compound can be selected as long as it works.

[0042] Examples of the organic semiconductor material include acenes such as pentacene and tetracene disclosed in JP-A-5-55568 and phthalocyanines including lead phthalocyanine disclosed in JP-A-4-167561 and the like. In addition, porphyrins such as benzoborphyrin disclosed in JP-A-2004-319982, etc., other low molecular weight compounds such as perylene, its tetracarboxylic acid derivatives, tetrathiafulvalenes, etc., and JP-A-8-2648 05 A aromatic oligomer based on a thiophene hexamer called chenille or succitiphene, as well as polythiophene, poly-ethylene vinylene, and poly-p-phenylene-ethylene. Polymers etc. (Many of these are Advanced Materi-al, 2002, No. 2, page 99. Listed) it is generally known. Among them, the effect of the present invention is more exhibited when an organic semiconductor material is a low molecular weight compound, and particularly when a low molecular weight organic semiconductor material having a number average molecular weight of 5000 or less is used, the mobility is high. More preferred in obtaining organic thin film transistors to drive.

[0043] Among the organic semiconductor materials described above, as low molecular weight compounds, for example, pyrene, coronene, ovalen and the like and derivatives thereof, anthracene, pentacene and the like and derivatives thereof (acenes), rubrene and the derivatives thereof and the like. Preferred examples include condensed polycyclic hydrocarbons, benzodithiophene, anthradithiophene, condensed polycyclic aromatic compounds containing heteroatoms represented by derivatives thereof, and the like, and thiophene oligomers. Can be mentioned. Examples of pentacenes include pentacene derivatives having substituents described in International Publication Nos. 03Z16599, 03Z28125, U.S. Pat.No. 6,690,029, JP-A-2004-107216, etc. Examples include pentacene precursors described in Publication No. 2003-136964, acenes described in Amer. Chem. Soc., Vol. 127, No. 14.4986, and derivatives thereof.

[0044] The organic semiconductor material is preferably a compound represented by the general formula (1).

In general formula (1), R to R represent a hydrogen atom or a substituent, and Z and Z are substituted or

1 6 1 2

Represents an unsubstituted aromatic hydrocarbon ring, or a substituted or unsubstituted aromatic heterocyclic ring, nl and n2. Represents an integer of ~ 3. Examples of the substituent represented by R to R include an alkyl group (e.g., a methyl group, ethyl group).

1 6

Group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group) Group), alkenyl group (eg beryl group, aryl group, etc.), alkynyl group (eg ethynyl group, triethylsilylethynyl group, triisopropylpropylethylinyl group, propargyl group, etc.), aryl Group (e.g., phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, xylyl group, naphthyl group, anthryl group, azulyl group, acenaphthyl group, fluoro group, phenanthryl group, indenyl group) Group, pyrenyl group, biphenyl group, etc.), aromatic heterocyclic group (for example, furyl group, chael group, pyridyl group, pyridazyl group, Midyl group, birazyl group, triazyl group, imidazolyl group, pyrazolyl group, thiazolyl group, benzoimidazolyl group, benzoxazolyl group, quinazolyl group, phthalazyl group, etc.), heterocyclic group (for example, pyrrolidyl group, imidazolidyl group, morpholyl group) Aryl group, oxazolidyl group, etc.), alkoxyl group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxyl group (for example, cyclopentyloxy group, Cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.) ) A cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), an arylthio group (for example, phenylthio group, naphthylthio group, etc.), an alkoxycarbo group (for example, methyloxycarbonyl group, ethyloxycarbonyl) Group, butyloxycarbonyl group, oxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxy group (for example, phenyl group, naphthyloxy group, etc.) ), Sulfamoyl groups (for example, aminosulfol groups, methylaminosulfol groups, dimethylaminosulfol groups, butylaminosulfol groups, hexylaminosulfol groups, cyclohexylaminosulfol groups) , Octylaminosulfol group, dodecylaminosulfol group, phenolaminosulfol group, naphthyl Ruaminosuruho - group, 2-pyridyl aminosulfonyl - Le group), Ashiru group (e.g., Asechiru group, Echirukarubo - group, propyl carbo - Le Group, pentyl carbo yl group, cyclohexyl carbo yl group, oct yl carbo ol group, 2-ethyl hexyl carbo yl group, dodecyl carbo yl group, phen carbonyl group, naphthyl carbonyl group, pyridyl carbonyl group, etc. ), An acyl group (for example, an acetyloxy group, an ethylcarbonyloxy group, a butylcarbonyloxy group, an octylcarboxoxy group, a dodecylcarboxoxy group, a phenylcarboxyl group, etc.), an amide group (for example, Methyl carbolumino group, ethyl carbolumino group, dimethyl carbolumino group, propyl carbolumino group, pentyl carbolumino group, cyclohexyl carbolumino group, 2-ethyl hexylcarbo-lamino group, octylcarbo-lumino group, Dodecyl polyamino group, phenyl polyamino group, Tilcarbonylyl group, etc.), strong rubamoyl group (eg, aminoamino group, methylaminocarbol group, dimethylaminocarbol group, propylaminocarbol group, pentylamino force group, cyclohexyl) Aminocarbol, octylaminocarbol, 2-ethylhexylaminocarbol, dodecylaminocarbol, phenolaminocarbol, naphthylaminocarbole Group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2 —Pyridylaminoureido group, etc.), sulfier group (eg methylsulfier group, ethylsulfi- Group, butylsulfyl group, cyclohexylsulfyl group, 2 —ethylhexylsulfyl group, dodecylsulfuryl group, phenylsulfuryl group, naphthylsulfuryl group, 2-pyridylsulfyl group, etc.) Alkylsulfol groups (eg, methylsulfol group, ethylsulfol group, butylsulfol group, cyclohexylsulfol group, 2-ethylhexylsulfol group, dodecylsulfol group, etc.), arylsulfol- Group (for example, phenylsulfol group, naphthylsulfol group, 2-pyridylsulfol group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, amino-group, naphthylamino group, 2-pyridylamino group, etc.), halogen Atom (for example, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon group (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group) etc) , A cyan group, a silyl group (for example, a trimethylsilyl group, a triethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, a phenyljetylsilyl group, etc.).

[0047] These substituents may be further substituted with the above substituents, or a plurality thereof may be bonded to each other to form a ring.

[0048] Among them, a preferable substituent is an alkyl group, more preferably 2 to 2 carbon atoms.

0 is an alkyl group, particularly preferably an alkyl group having 6 to 12 carbon atoms.

[0049] Examples of the substituted or unsubstituted aromatic hydrocarbon ring represented by Z and Z include phenyl

1 2

Group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulyl group, acenaphthyl group, fluorol group, phenanthryl group, indenyl group, pyrenyl group, biphenyl group -Lyl group etc. are mentioned.

[0050] Examples of the substituted or unsubstituted aromatic heterocycle represented by Z and Z include a furyl group,

1 2

Examples include a chenyl group, a pyridyl group, a pyridazyl group, a pyrimidyl group, a birazyl group, a triazyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, a benzoimidazolyl group, a benzoxazolyl group, a quinazolyl group, and a phthalazyl group.

[0051] The organic semiconductor material is preferably a compound represented by the general formula (2).

[0052] In the general formula (2), R and R represent a hydrogen atom or a substituent, and Z and Z are substituted or

7 8 1 2

An unsubstituted aromatic hydrocarbon ring or a substituted or unsubstituted aromatic heterocyclic ring is represented, and n 1 and n2 represent an integer of 0 to 3.

[0053] The substituents represented by R and R are the same as the substituents represented by R to R in the general formula (1).

7 8 1 6

It is righteousness.

[0054] Examples of the substituted or unsubstituted aromatic hydrocarbon ring represented by Z and Z include the general formula (1

1 2

) Of z) and z is the same as the substituted or unsubstituted aromatic hydrocarbon ring represented by z.

1 2

[0055] The substituted or unsubstituted aromatic heterocycle represented by Z and Z includes Z in the general formula (1).

1 2 1

, Z is synonymous with a substituted or unsubstituted aromatic heterocyclic ring.

2

[0056] The substituents R and R in the general formula (2) are preferably represented by the general formula (3).

7 8

Good.

In the general formula (3), R / R represents a substituent, and X represents Si, Ge, or Sn.

9 11

[0058] Examples of the substituent represented by R to R include the substituent represented by R to R in the general formula (1). It is synonymous. X is preferably S and Ge is Ge.

Examples of these are the following compounds: The present invention is not limited to these.

[0060] [Chemical 4]

[0061] [Chemical 5] [9>] [2900]

[0063] In the present invention, the organic semiconductor layer may be formed by a vacuum deposition process or a coating method such as cast coating, dip coating, spin coating, ink jet printing, screen printing, or the like. In the present invention, it is preferable to form an organic semiconductor film on a substrate by a solution process.

[0064] Further, the organic solvent contained in the organic semiconductor layer according to the present invention may be contained by forming the organic semiconductor film and then encapsulating it in a solvent vapor. It is preferably used when preparing an organic semiconductor material solution or dispersion and applying it to the solution process.

[0065] Further, when an organic solvent having a relatively low boiling point is used, a preferable organic semiconductor film can be obtained even when the substrate temperature is near room temperature. However, when an organic solvent having a higher boiling point is used, a substrate is used. It is preferable to adjust the organic solvent content to an appropriate amount by heating or the like. In this case, after forming the organic semiconductor wet film, the organic solvent content may be adjusted by, for example, heating or placing the substrate in a vacuum. A method of applying the organic semiconductor solution onto the heated substrate However, adjusting the organic solvent content and improving the orientation of the organic semiconductor is more preferable for promoting the growth of the crystalline film.

[0066] Further, in order to make the present invention more effective, a known inorganic material or organic polymer is added to the organic thin film transistor itself formed on the organic semiconductor layer or by necessary constituent elements. It is preferable to form a protective film (sealing film) for protecting the organic semiconductor film using a remer material or the like. As a method for forming the protective film, there are known techniques such as JP-T-2003-525521, JP-A-2004-506985, JP-A-2002-314093, JP-A-2003-258164, etc. Can be applied. In addition, an insulating film used as a gate insulating layer, which will be described later, can also be applied as a protective film, and a support described later is further attached to an organic thin film transistor manufactured on the support, or laminated with a polymer sheet. Thus, a protective film may be formed.

[0067] The substrate used in the present invention may be subjected to surface treatment in advance. As the surface treatment, it is more preferable to form a self-aligned thin film on the substrate, such as a treatment with a silane coupling agent. Examples of the silane coupling agent include octadecyl trichlorosilane, nonyltrichlorosilane, octyltrichlorosilane, octyltrimethoxysilane, octyltriethoxysilane, n-butyltrichlorosilane, i-butyltrichlorosilane, and ethyltrichlorosilane. , Methyltrichlorosilane, trimethylchlorosilane, hexamethyldisilazane, 4-phenylbutyltrichlorosilane, 3-phenoxypropyltrichlorosilane, phenyltrichlorosilane, cyclohexyltrichlorosilane, heptadecafluoro-1, 1, 2,

Known materials such as 2-tetrahydrodecyltrichlorosilane are preferred examples. 1S The present invention is not limited to these. As for the surface treatment method using a silane coupling agent, a known method such as disclosed in JP-A-2004-327857, JP-A-2005-32774, JP-A-2005-158765, etc. can be applied. it can. For example, a vapor phase method such as a CVD method, a liquid phase method such as a spin coating method or a dip coating method, a screen printing method, a micromold method, a micro contact method, a printing method such as an inkjet method, or the like can be applied. .

[0068] Further, before the treatment with the silane coupling agent, the surface of the substrate (for example, an insulating film such as a thermal oxide film formed on the silicon substrate) is hydrophilized such as oxygen plasma treatment or UV ozone treatment. It is generally known that the treatment (treatment for forming hydroxyl OH on the surface) is preferable for forming a dense and strong self-assembled monomolecular film. Is also described. Furthermore, even if a generally well-known orientation treatment such as rubbing is performed, there is no problem. [0069] The thickness of the organic semiconductor layer formed in the present invention is not particularly limited, but the characteristics of the obtained organic thin film transistor (TFT) are often greatly influenced by the thickness of the semiconductor layer. The film thickness varies depending on the semiconductor material, but in general: Lm or less, particularly 10 to 3 OOnm is preferred.

[0070] The organic semiconductor layer includes, for example, a material having a functional group such as acrylic acid, acetamide, a dimethylamino group, a cyan group, a carboxyl group, a nitro group, a benzoquinone derivative, tetracyanethylene, and tetracyan Materials that serve as acceptors, such as noquinodimethane and derivatives thereof, and materials having 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, force rubazole and its derivatives, tetrathiafulvalene and its derivatives, etc. Such a material may be contained and so-called doping treatment may be performed.

[0071] The doping means introducing an electron-donating molecule (acceptor) or an electron-donating molecule (donor) into the thin film as a dopant. Therefore, the doped thin film is a thin film containing the organic semiconductor material and dopant used in the present invention. Any of an acceptor and a donor can be used as the dopant used in the present invention, and a known material can be used as the acceptor and donor, and a known process can be used for the introduction thereof.

[0072] Taking the bottom gate type organic thin film transistor which is one of the preferred embodiments of the present invention as an example, the organic thin film transistor includes a gate electrode, a gate insulating film, an active layer, a source electrode and a drain electrode on a support. Are configured by being optimally arranged.

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

The [0074] Further, for example, after forming the gate insulating film, a source and drain electrode pattern is formed on the gate insulating film, and an organic semiconductor channel is formed by patterning between the source and drain electrodes. .

[0075] As described above, the gate electrode, the gate insulating film, the active layer (organic semiconductor layer), the source electrode, and the drain electrode are appropriately patterned and arranged optimally on the support, if necessary. The organic thin film transistor of the present invention can be obtained.

In the following, other components constituting the organic thin film transistor other than the organic thin film transistor active layer (organic semiconductor layer (thin film)) obtained by the production method of the present invention will be described.

In the present invention, the material for forming the source electrode, the drain electrode and the gate electrode is not particularly limited as long as it is a conductive material, and is platinum, gold, silver, nickel, chromium, copper, iron, tin. , Antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide, antimony, indium oxide 'tin (ITO), fluorine-doped acid zinc, zinc, carbon , Graphite, glassy carbon, silver paste, and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium-potassium alloy, magnesium Z copper Mixture, Magnesium Z Silver Mixture, Ma Gnesium / aluminum mixtures, magnesium Z indium mixtures, aluminum Z acid / aluminum mixtures, lithium Z aluminum mixtures are used, with platinum, gold, silver, copper, aluminum, indium, iota and carbon being particularly preferred. Alternatively, a known conductive polymer whose conductivity has been improved by driving or the like, for example, conductive polyarrin, conductive polypyrrole, conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, etc. is also suitable. Used. Of these, a material having a low electrical resistance is preferred on the contact surface with the semiconductor layer.

[0078] As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method from a conductive thin film formed using a method such as vapor deposition or sputtering using the above as a raw material, aluminum, copper or the like. There is a method of forming an electrode on a metal foil using a resist by thermal transfer, ink jet or the like. Conductive polymer solutions or dispersions, conductive The fine particle dispersion may be directly patterned by inkjet, or may be formed from the coated film by lithography, laser abrasion, or the like. Furthermore, a method of patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as relief printing, intaglio printing, lithographic printing, or screen printing can also be used.

[0079] In the present invention, the source and drain electrodes are preferably formed from a fluid electrode material such as a solution, dispersion or conductive fine particle dispersion of the conductive polymer. For example, conductive fine particles such as metal are dispersed in a dispersion medium such as water, an organic solvent or a mixture thereof, preferably using a dispersion stabilizer such as an organic material, and a paste or ink is used. It is preferable to form an electrode by preparing a conductive fine particle dispersion and coating and patterning it.

[0080] Metal materials of conductive fine particles (metal fine particles) include platinum, gold, silver, cobalt, nickel, chromium, copper, iron, tin, antimony, lead, tantalum, indium, palladium, tellurium, Forces that can use yuum, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, zinc, etc.Platinum, gold, silver, copper, conol, chromium, iridium, nickel, palladium, especially with a work function of 4.5 eV or more Molybdenum and tungsten are preferred.

[0081] As a method for producing such a metal fine particle dispersion, metal ions in a liquid phase, such as a physical generation method such as a gas evaporation method, a sputtering method, a metal vapor synthesis method, a colloid method, or a coprecipitation method are used. Examples of the chemical production method include reduction to produce fine metal particles, preferably disclosed in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A-2000-239853, and the like. Metal fine particles produced by the gas evaporation method described in JP-A-2001-254185, 2001-53028, 2001-35255, 2000-124157, 2000-123634, etc. It is a dispersion.

[0082] The average particle diameter of the dispersed metal fine particles is preferably 20 nm or less from the viewpoint of the effect of the present invention.

[0083] In addition, it is preferable to add a conductive polymer to the metal fine particle dispersion, and if the source electrode and the drain electrode are formed by pressing, heating, etc., the organic semiconductor is formed by the conductive polymer. Can make ohmic contact with the layer. That is, the surface of the metal fine particles Further, the effect of the present invention can be further enhanced by interposing a conductive polymer to reduce the contact resistance to the semiconductor and heat-fusing the metal fine particles.

As the conductive polymer, it is preferable to use a known conductive polymer whose conductivity has been improved by doping or the like. For example, conductive polyarine, conductive polypyrrole, conductive polythiophene, polyethylenedioxy A complex of thiophene and polystyrene sulfonic acid is preferably used.

[0085] The content of the metal fine particles is preferably LV, preferably 0.00001-0. If this amount is exceeded, fusion of the metal fine particles may be inhibited.

[0086] After forming electrodes with these metal fine particle dispersions, the metal fine particles are thermally fused to form source and drain electrodes. It is also preferable to promote fusion by applying a pressure of about 1 to 50000 Pa, more preferably about 1000 to 10,000 Pa at the time of electrode formation.

[0087] As a method of patterning like an electrode using the metal fine particle dispersion, for example, there is a patterning method by a printing method using the metal fine particle dispersion as an ink. In addition, there is a method of patterning by an ink jet method, which is a method of discharging a dispersion of metal fine particles from an ink jet head and patterning the dispersion of metal fine particles. As a discharge method of the ink jet head force, On-demand type such as piezo method and bubble jet (registered trademark) method can be patterned by a known method such as continuous jet type ink jet method such as electrostatic suction method.

[0088] As a method of heating or pressurizing, known methods such as a method used for a heating laminator and the like can be used.

[0089] The ability to use various insulating films as the gate insulating layer. Particularly preferred is a high dielectric constant oxide film having a high relative dielectric constant.

[0090] Examples of the inorganic oxide include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, titanium Strontium acid, barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantanolate, bismuth tantalate, bismuth tritium German thorium and the like. Of these, silicon oxide, acid aluminum, acid tantalum and acid titanium are preferred. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

[0091] The film can be formed by vacuum deposition, molecular beam epitaxy, ion cluster beam method, low energy ion beam method, ion plating method, CVD method, sputtering method, atmospheric pressure plasma method (large Wet processes such as atmospheric pressure plasma CVD method), dip coating method, casting method, reel coating method, bar coating method, die coating method, and other wet processes such as printing and ink jet patterning methods. Can be used.

[0092] The wet process includes a method of applying and drying a liquid in which inorganic oxide fine particles are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as necessary. A so-called sol-gel method is used in which a solution of a precursor of the product, for example, an alkoxide is applied and dried.

[0093] Of these, the preferred! / Is the atmospheric pressure plasma method.

[0094] The method of forming an insulating film by the atmospheric pressure plasma method is a process in which a thin film is formed on a substrate by discharging at atmospheric pressure or near atmospheric pressure to excite reactive gas to form a thin film on a substrate. [Kyotsu Hiramatsu, JP-A-11-61406, JP-A-11-133205, JP-A-2000-121804, JP-A-2000-147209, JP-A-2000-185362, etc. Thus, a highly functional thin film can be formed with high productivity.

[0095] Further, as a method for forming the organic compound film, polyimide, polyamide, polyester, poly acrylate, photo radical polymerization type, photo-power thione polymerization type photocurable resin, or attalyl nitrile component is contained. Copolymers, polybuluphenol, polybulualcohol, novolac resin, cyanoethyl pullulan, and the like can also be used.

[0096] The wet process is preferred as a method of forming the organic compound film.

[0097] The inorganic oxide film and the organic oxide film can be laminated and used in combination. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

[0098] The support is made of glass or a flexible resin sheet. For example, a plastic film can be used as the sheet. Examples of the plastic film include Polyethylene terephthalate (PET), Polyethylene naphthalate (PEN), Polyetherol sulfone (PES), Polyetherimide, Polyetheretherketone, Polyphenylene sulfide, Polyarylate, Polyimide, Polycarbonate (PC), Cellulose triacetate (TAC), Examples thereof include a film having cellulose acetate propionate (CAP) and the like. In this way, by using a plastic film, it is possible to reduce the weight as compared with the case of using a glass substrate, to improve portability, and to improve resistance to impact.

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

[0100] FIG. 1 (a) shows a case in which metal fine particles are contained on the support 6 by patterning gold or the like by vapor deposition using a mask, or after forming a pattern of a layer containing metal fine particles. The source electrode 2 and the drain electrode 3 are formed by heating and pressurizing the layers, and the organic semiconductor material layer 1 is formed between the source and drain electrodes, and the gate insulating layer 5 is formed thereon. Further, an organic TFT is formed by forming a gate electrode 4 thereon.

[0101] FIGS. 1 (b) and 1 (c) show other configuration examples of the top gate type organic thin film transistor.

[0102] Figures 1 (c!) To (f) show configuration examples of bottom-gate organic TFTs. In FIG. 1 (d), after the gate electrode 4 is formed on the support 6, the gate insulating layer 5 is formed, the source electrode 2 and the drain electrode 3 are formed thereon, and the gate between the source and drain electrodes is formed. A bottom gate type organic TFT is formed by forming an organic semiconductor material layer 1 on an insulating layer. Similarly, other configuration examples are shown in (e) and (f). In particular, in FIG. 5 (f), the gate electrode 4 is formed on the support 6, the gate insulating layer 5 is formed, the organic semiconductor material layer 1 is formed thereon, and then the source electrode 2 and the drain are further formed. An electrode 3 is formed to form an organic TFT. 9 is a substrate.

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

[0104] The TFT sheet 10 has a large number of organic TFTs 11 arranged in a matrix. 7 is a gate bus line of each organic TF T11, and 8 is a source bus line of each organic TFT11. An output element 12 such as a liquid crystal or an electrophoretic element is connected to the source electrode of each organic TFT 11 to constitute a pixel in the display device. The pixel electrode is used as the input electrode of the photosensor Also good. In the example shown in the figure, the liquid crystal is shown as an output element in an equivalent circuit having resistance and capacitor power. 13 is a storage capacitor, 14 is a vertical drive circuit, and 15 is a horizontal drive circuit.

Example

[0105] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “%” in the examples represents “mass%”.

[0106] Examples

An organic thin film transistor element (hereinafter referred to as TFT element) 1 having the layer configuration shown in FIG. 1 (f) was produced.

First, a 2000 A thick thermal oxide film was formed on a Si wafer having a specific resistance of 0.02 Ω′cm as the gate electrode 4 to form the gate insulating layer 5. Hereinafter, this is referred to as a substrate 1.

A deposited film (thickness 25 nm) of Compound 1 was formed on the substrate 1 using a vacuum deposition machine. Further, gold was deposited on the surface of the film using a mask to form the source electrode 2 and the drain electrode 3. The source electrode 2 and the drain electrode 3 each have a width of 100 μm, a thickness of 200 nm, a channel width W = 5 mm, and a channel length L = 50 m. Finally, the TFT film 1 was fabricated by sealing with a polyimide thin film so that the above-described deposited film (organic semiconductor layer) of Compound 1 was not exposed to the external environment.

[0109] Further, the substrate in which the source electrode 2 and the drain electrode 3 were formed on the above-described vapor-deposited film of the compound 1 was sealed in a container containing toluene vapor in a nitrogen atmosphere, and the solvent contained as shown in Table 1. After adjusting the amount, the TFT element 2 and the TFT element 3 were produced by sealing with a polyimide thin film.

[0110] In TFT elements 1 to 3, the organic solvent content in the organic semiconductor layer was determined by PT-GC / MS measurement.

<0111> <Production of TFT elements 4-14>

Using the substrate 1 prepared above, surface treatment with hexamethyldisilazane (immerse the substrate in 1% toluene solution of hexamethyldisilazane heated to 60 ° C for 10 minutes, then wash with toluene, This was used as substrate 2. [0112] A 0.5% black mouth form solution of compound 4 (poly (3-hexylthiophene), regioregular, Aldrich, PHT, average molecular weight 89000) was spin-coated (lOOOOrpm, 30 seconds) on substrate 2. A coating film (thickness 25 nm) was formed. Further, after forming the source electrode 2 and the drain electrode 3 in the same manner as the TFT elements 2 and 3, the TFT element 4 was fabricated by pasting a sealing film.

[0113] In the fabrication of TFT element 4, the same operation as TFT element 4 was performed except that the organic semiconductor material was changed from compound 4 to compound 5 and the organic solvent was changed from 1,2 to dichlorobenzene. Thus, a TFT element 5 was produced. As Compound 5, Exemplified Compound (3) described in US Patent Application Publication No. 2003-164 495 was used.

[0114] Furthermore, in the fabrication of TFT element 4, the organic semiconductor material and the organic solvent were changed as shown in Table 1, and the solvent content was adjusted as shown in Table 1 by controlling the dry state of the coating film. TFT elements 6 to 14 were produced in the same manner except for the above.

[0115] In TFT elements 4 to 14, the organic solvent content in the organic semiconductor layer was determined by PT-GC / MS measurement.

<0116> <Production of TFT elements 15-22>

While the substrate 1 produced above was heated on a hot plate in a nitrogen atmosphere, a 1,2-dichlorobenzene solution of compound 1 (0.1%) was developed on the substrate, and a coating film (thickness) 2 5 nm). Further, after forming the source electrode 2 and the drain electrode 3 in the same manner as the TFT elements 2 and 3, the TFT element 15 was fabricated by attaching a sealing film.

[0117] Furthermore, in the production of TFT element 15, the organic semiconductor material and the organic solvent were changed as shown in Table 1, and the solvent content was adjusted as shown in Table 1 by controlling the dry state of the coating film. Other than the above, TFT elements 16 to 22 were produced in the same manner.

[0118] In the TFT elements 15 to 22, the content of the organic solvent in the organic semiconductor layer was determined by PT-GC / MS measurement.

[0119] [Chemical 7]

Compound 4 Compound 5

1]

(Transistor characteristics)

The TFT element 122 fabricated as described above showed the operating characteristics of a p-channel enhancement type FET. For each TFT element, the carrier mobility is calculated from the saturation region force of the I–V characteristics, and the ON / OFF ratio (with a drain bias of 40 V is assumed. The ratio of drain current values at 50 V and OV) was determined, and the results are shown in Table 2. The carrier mobility and ONZOFF ratio were also evaluated when left for 1 month at 25 ° C and 45% humidity, and when left for 1 month at 50 ° C and 60% humidity. The results are shown in Table 2.

[Table 2]

[0123] From Table 2, the film density 1. 33gZcm ³ larger TFT element 1 of the organic semiconductor layer, with respect to mobility hot, but also the degree of deterioration decreases one digit in a high humidity, OFF current It was found that the decrease in the ON / OFF ratio due to the increase was quite noticeable.

[0124] Further, it was found that the transistor characteristics of the TFT elements 4 and 5 in which the film density of the organic semiconductor layer was less than 1.15 gZcm ³ were much inferior to those of the TFT element of the present invention.

[0125] From the above results, the organic thin film transistor of the present invention having an organic semiconductor layer density of 1.15-; L. 33 gZcm ³ has transistor characteristics (carrier mobility, ONZO FF ratio) compared to the comparison. Excellent, stable over time even in the air or at high temperatures and high humidity As a result, it became a thin film transistor.

Claims

Claims [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 organic semiconductor layer has a film density of 1.15 to: L 33 g / cm 3 An organic thin film transistor characterized in that: [2] The organic thin film transistor according to [1], wherein the organic semiconductor layer contains 1 X 10-2 to 1 X 103 ppm of an organic solvent. [3] The organic material according to claim 1 or 2, wherein at least one organic semiconductor material constituting the organic semiconductor layer is a compound represented by the following general formula (1): Thin film transistor.

[Chemical formula 1] General formula (1)

1 6 1 2

4. The organic thin film transistor according to claim 3, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).

[Chemical 2]

—General formula (2)

(In the formula, R and R represent a hydrogen atom or a substituent, and Z and Z are substituted or unsubstituted aromatics.

7 8 1 2

The substituents R and R in the general formula (2) are represented by the following general formula (3)

7 8

5. The organic thin film transistor according to claim 4.

[Chemical formula 3] General formula

(Wherein R to R represent a substituent, and X represents Si, Ge or Sn.)

9 11

[6] The organic thin film transistor according to any one of [1] to [5], wherein the organic semiconductor layer is a layer formed by a coating method using an organic solvent.