JPWO2008096850A1 - Insulating film material for organic thin film transistor and organic thin film transistor using the same - Google Patents

Abstract

The present invention relates to an insulating film material for an organic thin film transistor comprising a compound having two or more epoxy groups in the molecule, preferably an n-channel type comprising a compound having two or more epoxy groups in the molecule or The present invention relates to an insulating film material for an ambipolar organic thin film transistor.

Description

  The present invention relates to an insulating film material for an organic thin film transistor and an organic thin film transistor using the same.

  As a semiconductor device, for example, a thin film transistor (TFT) has been put into practical use as a switching element such as an active matrix liquid crystal display, and an element using amorphous or polycrystalline silicon as a semiconductor film is widely used.

  In recent years, organic semiconductor materials have attracted attention as semiconductor materials for TFTs. Organic semiconductors can be easily formed into thin films by simple film-forming methods such as spin coating and vacuum deposition, and the manufacturing process temperature can be lowered compared to conventional TFTs using amorphous or polycrystalline silicon. There are advantages.

  Lowering the process temperature enables formation on plastic substrates with low heat resistance, reducing display weight and cost, and diversifying applications by taking advantage of the flexibility of plastic substrates. The effect can be expected.

  By the way, as a semiconductor device, a complementary transistor (CMOS) in which an n-channel MOS transistor (nMOS) and a p-channel MOS transistor (pMOS) are combined in an IC chip is known and widely used. This complementary transistor has a basic structure in which an enhancement type nMOS and a pMOS are connected in series, and has an n channel region and a p channel region.

  Even in a semiconductor device using an organic semiconductor material, a variety of circuits can be manufactured if both a transistor exhibiting p-channel characteristics and a transistor exhibiting n-channel characteristics can be manufactured.

  Also, mainly in the field of organic semiconductor research, a transistor exhibiting both p-channel and n-channel characteristics is defined as having an ambipolar characteristic, and such a transistor is called an ambipolar organic thin film transistor. It is. Here, the ambipolar characteristic refers to the property of exhibiting p-channel characteristics when holes are injected as carriers and exhibiting n-channel characteristics when electrons are injected as carriers. The ambipolar organic thin film transistor is expected to be applied as a light emitting transistor in addition to the application to the CMOS circuit.

However, the development of transistors using organic semiconductor materials so far has mainly been transistors exhibiting p-channel characteristics. This is considered to be because n-channel type characteristics are hindered by the influence of a trap or the like existing at the interface between the organic semiconductor and the gate insulating film. For example, it has been reported that electrons are trapped by hydroxyl groups present on the surface of SiO ₂ (for example, Ray-Ray Chua, Jana Zaumsell, Jui-Fen Chang, Eric C.-W.Ou, Peter K.-). H. Ho, Henning Sirringhaus, Richard H. Friend, Nature, 434, 194-199 (2005)). Therefore, in order to obtain an organic thin film transistor exhibiting n-channel type characteristics, in addition to development of an n-channel type organic semiconductor, development of a good gate insulating film has been strongly demanded.

  In response to the above problem, for example, Friends et al. Show that transistors using various polymers as organic semiconductors exhibit ambipolar characteristics by using a benzocyclobutene derivative (BCB) having no hydroxyl group for the gate insulating film. (E.g., Lay-Ray Chua, Jana Zaumsell, Jui-Fen Chang, Eric C.-W. Ou, Peter K.-H. Ho, Henning Sirringhaus, Richard H. Friend, Nature, 434, 19 199 (2005).).

  In addition, it has been reported that a transistor using a rubrene single crystal exhibits ambipolar characteristics by using polymethyl methacrylate (PMMA) for a gate insulating film (for example, T. Takahashi, T. Takenobu, J., et al. Takeya, Y. Iwasa, Appl. Phys. Lett., 88 (2006) 033505.).

  These attempts are very important. On the other hand, BCB requires a high temperature exceeding 200 ° C. in order to advance the curing reaction, and a plastic substrate having a low heat-resistant temperature cannot be used.

  Further, PMMA has insufficient solvent resistance after coating, and when an organic semiconductor is formed on PMMA by coating, materials that can be used as the organic semiconductor material are limited.

  On the other hand, an insulating film that can be cured at a low temperature of 200 ° C. or lower has been studied for application to a plastic substrate. As such an example, an organic thin film transistor in which polyimide is applied to a gate insulating film has been reported (for example, refer to the 66th Japan Society of Applied Physics Academic Lecture Proceedings (Autumn 2005, Tokushima University), 9a-N-9) . However, only the p-channel type properties are reported here.

  As another example, an organic thin film transistor in which a thermosetting epoxy resin is applied to a gate insulating film has been reported, but only a p-channel type characteristic has been reported (for example, the 67th application). Physics Society Academic Lecture Proceedings (Autumn 2006 Ritsumeikan University), 29a-ZH-9).

  As described above, in order to form various circuits using an organic thin film, it can be suitably used for an n-channel or ambipolar organic thin film transistor and can be cured at a low temperature. The lack of film material was a major problem.

  The present invention has been made in view of the above circumstances, and the object of the present invention is for an organic thin film transistor suitable for an organic thin film transistor, particularly an n-channel or ambipolar organic thin film transistor, in which a curing reaction proceeds even at a low temperature. It is to provide an insulating film material. Furthermore, it is providing the organic thin-film transistor using this insulating film material for organic thin-film transistors.

  The present inventors diligently studied without being bound by the previous examples that n-channel operation is difficult with an insulating film having a hydroxyl group. As a result, we succeeded in obtaining an insulating film material that can be suitably used for an n-channel or ambipolar organic thin film transistor, despite using a compound having an epoxy group that can have a hydroxyl group after curing. The invention has been completed.

The present invention relates to an insulating film material for an organic thin film transistor comprising a compound having two or more epoxy groups in the molecule.
In the present invention, the insulating film material for an organic thin film transistor can be preferably used for an n-channel type or an ambipolar type organic thin film transistor.

  In the insulating film material for an organic thin film transistor of the present invention, the hydrolyzable chlorine content after curing is preferably 1000 ppm or less, and the epoxy equivalent of the compound having two or more epoxy groups in the molecule is 10,000 or less. It is preferable that

  Examples of the compound having two or more epoxy groups in the molecule include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, and bisphenol A novolac type epoxy resin.

  The insulating film material for an organic thin film transistor of the present invention may further contain a phenol novolac resin, a bisphenol novolac resin, or a silylated phenol resin in addition to the compound having two or more epoxy groups in the molecule.

  The present invention also provides an organic thin film transistor comprising at least a substrate, an organic semiconductor layer, a gate insulating film, and a conductor, wherein the gate insulating film is formed using the above-described insulating film material for an organic thin film transistor. About.

  The organic thin film transistor of the present invention is preferably an n-channel type or an ambipolar type.

  The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2007-029143 filed on Feb. 8, 2007, the disclosure of which is incorporated herein by reference.

FIG. 1 is a schematic view showing an example of an element structure of an organic thin film transistor according to an embodiment of the present invention. FIG. 2 is a schematic view showing an example of an element structure of an organic thin film transistor according to another embodiment of the present invention. FIG. 3 is a schematic view showing an example in which the gate insulating film is composed of two layers. FIG. 4 is a graph showing the gate voltage (V _G ) -drain current (I _D ) characteristics when the drain voltage (V _D ) is −20 V (Example 1). 5, in a variety of _{V G,} the drain voltage _{(V D)} - is a graph of drain current _{(I D)} characteristic (Example 1). _6, when the V D = + _60V, is a graph showing the V G -I _D characteristic (Example 1). 7, in a variety of _{V G,} is a graph showing the V D -I _D characteristic (Example 1). FIG. 8 is a graph showing the gate voltage (V _G ) -drain current (I _D ) characteristics when the drain voltage (V _D ) is −20 V (Example 2). 9, in the various _{V G,} is a graph showing the V D -I _D characteristic (Example 2). _10, when the V D = + 50 _V, which is a graph showing the V G -I _D characteristic (Example 2). 11, in various _{V G,} is a graph showing the V D -I _D characteristic (Example 2). FIG. 12 is a graph showing the gate voltage (V _G ) -drain current (I _D ) characteristics when the drain voltage (V _D ) is −20 V (Comparative Example 1). 13, in various _{V G,} is a graph showing the V D -I _D characteristic (Comparative Example 1). _14, when the V D = + 50 _V, which is a graph showing the V G -I _D characteristic (Comparative Example 1). 15, in various _{V G,} is a graph showing the V D -I _D characteristic (Comparative Example 1). _16, when the V D = + 30 _V, which is a graph showing the V G -I _D characteristic (Example 3). _17, when the V D = -40 _V, a graph showing the V G -I _D characteristic (Example 4). 18, in various _{V G,} is a graph showing the V D -I _D characteristic (Example 4). _19, when the V D = + _60V, is a graph showing the V G -I _D characteristic (Example 4). Figure 20 is in a variety of _{V G,} it is a graph showing the V D -I _D characteristic (Example 4). _21, when the V D = -40 _V, a graph showing the V G -I _D characteristic (Example 5). 22, in various _{V G,} is a graph showing the V D -I _D characteristic (Example 5). _23, when the V D = + _40V, is a graph showing the V G -I _D characteristic (Example 5). Figure 24 is in a variety of _{V G,} it is a graph showing the V D -I _D characteristic (Example 5).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Gate insulating film 4 Organic semiconductor layer 5 Source electrode 6 Drain electrode 7 Substrate 8 Gate electrode 9 Gate insulating film 10 Source electrode 11 Drain electrode 12 Organic semiconductor layer 13 Gate electrode 14 Gate insulating film 1
15 Gate insulating film 2
16 Source electrode 17 Drain electrode 18 Organic semiconductor layer 19 Substrate

  First, an organic thin film transistor using the insulating film material for an organic thin film transistor of the present invention will be described. The organic thin film transistor of the present invention is an organic thin film transistor including at least a substrate, an organic semiconductor layer, a gate insulating film, and a conductor. An organic thin film transistor usually has a source electrode, a drain electrode, and a gate electrode as conductors, but any of the conductors can also serve as a substrate. Examples of the organic thin film transistor of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an example of the element structure of the organic thin film transistor of the present invention. This organic thin film transistor is formed by forming a gate electrode 2, a gate insulating film 3, and an organic semiconductor layer 4 in this order on a substrate 1, and further forming a source electrode 5 and a drain electrode 6 thereon, and a top contact type. It is what is called.

  Moreover, FIG. 2 is a figure which shows another example of the element structure of the organic thin-film transistor of this invention. This organic thin film transistor is obtained by forming a gate electrode 8, a gate insulating film 9, a source electrode 10 and a drain electrode 11 on a substrate 7, and further forming an organic semiconductor layer 12 thereon, and is called a bottom contact type. Is.

  FIG. 3 is a view showing still another example of the element structure of the organic thin film transistor of the present invention. In this organic thin film transistor, a gate electrode 13, gate insulating films 14 and 15, a source electrode 16 and a drain electrode 17 are formed on a substrate 19, and an organic semiconductor layer 18 is further formed thereon. The organic thin film transistor of this example has two layers of gate insulating films.

  In addition to these, there are various kinds of element structures of organic thin film transistors, but there is no particular limitation. For example, the configuration described in “Organic thin film transistor operability improvement technology, material development, production method, element design, technical information association, 2003, P11” can be cited as an example.

  In the organic thin film transistor of the present invention, a substrate made of a material such as plastic, glass or silicon can be used. In the case where silicon is used, silicon can also function as a conductor (eg, a gate electrode).

  In the organic thin film transistor of the present invention, the gate electrode, the source electrode, and the drain electrode are formed of a conductor. The conductor to be used is not particularly limited. For example, silicon, doped silicon, platinum (Pt), gold (Au), silver (Ag), copper (Cu), chromium (Cr), aluminum (Al), Calcium (Ca), barium (Ba), indium-tin oxide (ITO), polythiophene-polystyrene sulfonic acid (PEDOT-PSS) and the like are suitable.

  The method for forming these electrodes is not particularly limited, and for example, a vacuum deposition method, a printing method, an ink jet method, or the like can be used.

  In the organic thin film transistor of the present invention, various low molecular compounds, oligomers and polymers can be used for the organic semiconductor layer, and there is no particular limitation. As the low molecular weight compound, for example, pentacene, rubrene, phthalocyanine, perylene, fullerene, or a derivative thereof can be used. As the oligomer, for example, oligothiophene or a derivative thereof can be used.

  Examples of the polymer include poly-p-phenylene vinylene (PPV), polyfluorene, fluorene-benzothiadiazole copolymer, fluorene-triphenylamine copolymer, fluorene-dithiophene copolymer, polythiophene, polyaniline, polyacetylene, polypyrrole. Alternatively, derivatives thereof and the like can be used.

  Alternatively, an organic semiconductor precursor may be formed as the organic semiconductor layer, and then converted to an organic semiconductor by applying light or heat. Examples of such a convertible material include, for example, “P. B. Shea, J. Kanicki, LR Pattison, P. Petroff, M. Kawano, H. Yamada, N. Ono, J. Appl. Phys. 100,034502 (2006) ". This material can be converted into a tetrabenzoporphyrin derivative by heating and can be used as a material for the organic semiconductor layer.

  In the organic thin film transistor of the present invention, the thickness of the organic semiconductor layer is not particularly limited, but is preferably 10 nm to 100 μm, more preferably 20 nm to 10 μm, and most preferably 30 nm to 1 μm.

  Next, the insulating film material for organic thin film transistors of the present invention (hereinafter also simply referred to as insulating film material) will be described in detail. The insulating film material is an insulating layer mainly formed between the organic semiconductor layer and the gate electrode, and the insulating film material of the present invention is made of, for example, a mixture containing a compound having two or more epoxy groups in the molecule. It is formed. Hereinafter, the composition of this mixture will be described in detail.

  The compound having two or more epoxy groups in the molecule is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy Resin, bisphenol A novolac type epoxy resin, salicylaldehyde novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin Examples thereof include epoxy resins such as resins, aliphatic cyclic epoxy resins and their halides and hydrogenated products, and these may be used alone or in combination of two or more. . Bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolac epoxy resin, or bisphenol A novolac epoxy resin are preferable. Among these, bisphenol A novolac type epoxy resins or phenol novolac type epoxy resins are preferable because the n-channel type characteristics of the produced organic thin film transistor are good.

The epoxy equivalent of the compound having two or more epoxy groups in the molecule is not particularly limited, but is preferably 10,000 or less, more preferably 5000 or less, and most preferably 2000 or less. If the epoxy equivalent is too large, the solvent resistance after curing tends to be insufficient.
Further, the epoxy equivalent of the compound having two or more epoxy groups in the molecule is not particularly limited, but is preferably 100 or more, more preferably 130 or more, and most preferably 175 or more. If the epoxy equivalent is too small, the cured product tends to be brittle.

  In addition to the compound having two or more epoxy groups in the molecule, a curing agent may be added to the mixture as necessary. The curing agent may be selected in consideration of curing characteristics, and is not particularly limited. For example, bisphenol A, bisphenol F, phenol which is a compound having two or more dicyandiamide or phenolic hydroxyl groups in one molecule. A novolak resin, a bisphenol novolak resin, a cresol novolak resin, a salicylaldehyde novolak resin, a halide, a hydride, a triazine structure-containing material, or the like of these phenol resins can be used. Silylated phenol resins and their halides, hydrides, triazine structure-containing materials and the like can also be used. As the silylated phenol resin, for example, a compound obtained by introducing a silyl group into a compound having two or more phenolic hydroxyl groups in one molecule can be used. The silyl group can be introduced, for example, by reacting an alkoxysilane with an epoxidized phenol resin such as a bisphenol A type epoxy resin. These curing agents may be used alone or in combination of two or more. The curing agent is preferably a phenol novolac resin, a bisphenol novolac resin, or a silylated phenol resin.

  The amount of the curing agent is not particularly limited. For example, in the case of a curing agent having a phenolic hydroxyl group, it may be blended so that the hydroxyl group is in the range of 0.5 to 2.0 equivalents relative to the epoxy group. preferable.

  When dicyandiamide is used as the curing agent, it is preferably blended so as to be in the range of about 2 to 5 parts by weight with respect to 100 parts by weight of the compound having two or more epoxy groups in the molecule.

  Moreover, when using silylated phenol resin as a hardening | curing agent, it is preferable to mix | blend so that a silyl group may be in the range of 0.1-10.0 equivalent with respect to an epoxy group.

  In addition to the compound having two or more epoxy groups in the molecule, a curing accelerator may be added to the mixture as necessary. Although it does not specifically limit as a hardening accelerator, For example, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt etc. can be used.

  The blending amount of the curing accelerator is not particularly limited, but is preferably in the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the compound having two or more epoxy groups in the molecule. More preferably, it is in the range of -1.0 part by weight. When the amount of the curing accelerator is less than 0.001 part by weight, insufficient curing tends to occur, and when it exceeds 10 parts by weight, the performance of the organic thin film transistor tends to be deteriorated.

  In addition to the compound having two or more epoxy groups in the molecule, particles having a relative dielectric constant of 10 or more may be added to the mixture as necessary. Such particles are not particularly limited. For example, barium titanate, strontium titanate, calcium titanate, magnesium titanate, lead titanate, lead zirconate titanate, titanium dioxide, barium zirconate, calcium zirconate , Lead zirconate, barium strontium titanate, zirconium dioxide and the like.

  In addition to the compound having two or more epoxy groups in the molecule, a solvent may be added to the mixture. The solvent to be used is not particularly limited. For example, chloroform, methylene chloride, dichloroethane, tetrahydrofuran, toluene, xylene, mesitylene, anisole, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, ethyl cellosolve acetate, ethylene glycol monomethyl ether, methanol , Ethanol, N, N-dimethylformamide, N, N-dimethylacetamide, gamma butyrolactone, cyclohexanone and the like can be used. The amount of the solvent added may be appropriately selected depending on the method of application to the substrate and the thickness of the gate insulating film, and is not particularly limited.

  Next, a method for forming a gate insulating film of an organic thin film transistor using the mixture will be described in detail.

  In order to form a gate insulating film using a mixture, for example, the mixture is formed by an inkjet method, a casting method, a dipping method, a relief printing, an intaglio printing, an offset printing, a lithographic printing, a relief printing reverse offset printing, a screen printing, a gravure After coating on a desired substrate by a known method such as printing or spin coating, the polymerization reaction is advanced by light irradiation or heat treatment to cure a compound having two or more epoxy groups in the molecule. Can be done.

  The application of the mixture onto the desired substrate can usually be carried out in the temperature range of -20 to + 300 ° C, preferably 10 to 100 ° C, particularly preferably 15 to 50 ° C.

  In addition, a light source such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a fluorescent lamp, a light emitting diode, or sunlight can be used for the light irradiation. Moreover, the said heat processing can be performed on a hotplate or in oven, and can be implemented at the temperature range of 0- + 300 degreeC, Preferably it is 20-250 degreeC, Most preferably, it is 80-200 degreeC.

  In the present invention, the hydrolyzable chlorine content in the insulating film material is preferably 1000 ppm or less. The hydrolyzable chlorine content of the gate insulating film (cured product of the insulating film material) formed using the insulating film material of the present invention is also preferably 1000 ppm or less. If the hydrolyzable chlorine content is too high, the n-channel characteristics of the organic thin film transistor tend to deteriorate. The hydrolyzable chlorine content in the insulating film material can be measured by adding a potassium hydroxide / ethanol solution to the insulating film material, heating and hydrolyzing it, and titrating with an aqueous silver nitrate solution. In the present invention, the amount of hydrolyzable chlorine content measured by this method is defined as the hydrolyzable chlorine content in the gate insulating film after curing.

  The thickness of the gate insulating film formed by the above method is not particularly limited, but is preferably 1 nm to 10 μm, more preferably 2 nm to 5 μm, and most preferably 5 nm to 1 μm. If the thickness of the gate insulating film is too small, a leakage current tends to occur between the gate and the source, and if it is too large, the driving voltage tends to increase.

In the organic thin film transistor of the present invention, the gate insulating film may be composed of two or more layers. An example of the case where the gate insulating film is composed of two layers as described above is shown in FIG. 3, but is not limited thereto. In this case, any one layer of the gate insulating film is formed from a mixture containing a compound having two or more epoxy groups in the molecule. The gate insulating film as the other layer may be formed from a mixture containing a compound having two or more epoxy groups in the molecule, or may be formed using another mixture or an inorganic material such as SiO _2. .

  Other mixtures are not particularly limited, but include, for example, 1,1,1,3,3,3-hexamethyldisilazane (HMDS), organic silane compounds such as octadecyltrichlorosilane (OTS), polyimide, acrylic resin, etc. A mixture of

The insulating film material for an organic thin film transistor of the present invention can be cured at a low temperature and is suitable for an organic thin film transistor, particularly an n-channel type or an ambipolar type organic thin film transistor.
In addition, the organic thin film transistor of the present invention can exhibit n-channel or ambipolar characteristics.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these.
Example 1
[Production of Organic Thin Film Transistor Using Insulating Film Material of the Present Invention 1]
On the n-doped Si wafer, 50 nm of Al was deposited to form a gate electrode. All subsequent work was performed in a glove box into which nitrogen gas was introduced.

On the substrate on which the gate electrode was formed, a phenol novolac type epoxy resin (2.08 g, epoxy equivalent 205, manufactured by Dainippon Ink and Chemicals, product name EPICLON), bisphenol A novolak (1.14 g, hydroxyl group equivalent) 118, Dainippon Ink and Chemicals, product name Phenolite), 2-ethyl-4-methylimidazole (3.2 mg) and anisole (18.3 mL) were mixed at room temperature (25 ° C.) using a spin coater. It apply | coated to the whole surface on the conditions of 3000min- ¹ . Thereafter, the substrate was heated on a hot plate at 80 ° C. for 15 minutes, 130 ° C. for 60 minutes, and 180 ° C. for 60 minutes to advance the polymerization reaction of the mixture to form a gate insulating film of 300 nm. In addition, it was 1000 ppm or less when the hydrolysable chlorine content in a mixture was calculated | required by the titration method using silver nitrate aqueous solution.

  Next, pentacene (manufactured by Sigma-Aldrich) as an organic semiconductor is formed to a thickness of 50 nm on the gate insulating film by a vacuum evaporation method, and further, Au is formed to a thickness of 30 nm by a vacuum evaporation method through a metal mask. And the drain electrode was formed. The gate width (W) was 1 mm, and the gate length (L) was 50 μm.

  The voltage-current characteristics of the organic thin film transistor thus fabricated were measured using a pA meter / DC voltage source (Hewlett Packard 4140B) and a digital electrometer (Advantest TR8652) in nitrogen at room temperature.

Further, the gate insulating film, a 1.5 mm (φ) Al electrode is formed on an n-doped Si wafer, and the gate insulating film capacitance (C ₀ ) at a frequency of 1 kHz using an impedance analyzer (Hewlett Packard 4192A). ) Was measured.

FIG. 4 shows a gate voltage (V _G ) -drain current (I _D ) characteristic when the drain voltage (V _D ) is −20V. When a negative voltage is applied to the V _{G, |} I D | is increased, the characteristics of the p-channel type was observed. The mobility (μ) was calculated from the V _G- ( _ID ) ^1/2 characteristic using the following formula, and was μ = 0.135 cm ² / Vs.
Further, in FIG. 5, the various _{V G,} the drain voltage _{(V D)} - shows the drain current _{(I D)} characteristic.

Further, in FIG. _6, V D = + during _60V, it shows the V G -I _D characteristic. When a positive voltage is applied to V _G, once the I _D is decreased, it has increased I _D, characteristics of the n-channel type was observed. The mobility at this time was μ = 4.14 × 10 ⁻⁴ cm ² / Vs.

Further, in FIG. 7, in the various _{V G,} it shows a V D -I _D characteristic.
Thus, both p-channel and n-channel characteristics were confirmed, and it was confirmed that the organic thin film transistor had ambipolar characteristics.

(Example 2)
[Production of Organic Thin Film Transistor Using Insulating Film Material of the Present Invention 2]
As gate insulating film materials, phenol novolac type epoxy resin (2.08 g, epoxy equivalent 205, manufactured by Dainippon Ink and Chemicals, product name EPICLON), silylated phenol resin (1.45 g, hydroxyl group equivalent 145, bisphenol) F-type epoxy resin and diphenyldimethoxysilane were reacted with each other), and a mixture consisting of 2-ethyl-4-methylimidazole (3.2 mg) and anisole (18.3 mL) was used in the same manner as in Example 1. Thus, an organic thin film transistor was produced. In addition, it was 1000 ppm or less when the hydrolysable chlorine content in a mixture was calculated | required by the titration method using silver nitrate aqueous solution.

FIG. 8 shows the gate voltage (V _G ) -drain current (I _D ) characteristics when the drain voltage (V _D ) is −20V. When a negative voltage is applied to the V _{G, |} I D | is increased, the characteristics of the p-channel type was observed. Further, in FIG. 9, in the various _{V G,} it shows a V D -I _D characteristic.

Further, in FIG. _10, when the V D = + 50 _V, shows the V G -I _D characteristic. When a positive voltage is applied to V _G, once the I _D is decreased, it has increased I _D, characteristics of the n-channel type was observed.
Further, in FIG. 11, in the various _{V G,} it shows a V D -I _D characteristic.
Thus, both p-channel and n-channel characteristics were confirmed, and it was confirmed that the organic thin film transistor had ambipolar characteristics.

(Comparative Example 1)
[Production of organic thin film transistor using polyimide as gate insulating film 1]
An organic thin film transistor was prepared in the same manner as in Example 1 except that polyimide was used as the gate insulating film, and voltage-current characteristics were measured. FIG. 12 shows a gate voltage (V _G ) -drain current (I _D ) characteristic when the drain voltage (V _D ) is −20V. When a negative voltage is applied to the V _{G, |} I D | is increased, the characteristics of the p-channel type was observed. Further, in FIG. 13, in the various _{V G,} it shows a V D -I _D characteristic.

Figure _14, V D = + during 50 _V, shows the V G -I _D characteristic. When a positive voltage is applied to V _G, although I _D decreases, it did not increase again.
Further, in FIG. 15, in the various _{V G,} show V D -I _D characteristic, never increases again becomes _{I D} is positive. N-channel type characteristics were not observed, and ambipolar characteristics were not confirmed.

(Example 3)
[Production of Organic Thin Film Transistor Using Insulating Film Material of the Present Invention 3]
An n-doped Si wafer was used as the substrate and gate electrode. All subsequent work was performed in a glove box into which nitrogen gas was introduced.

On the substrate, phenol novolac type epoxy resin (2.08 g, epoxy equivalent 205, manufactured by Dainippon Ink & Chemicals, product name EPICLON), bisphenol A novolak (1.14 g, hydroxyl equivalent 118, Dainippon Ink A mixture consisting of Chemical Industry Co., Ltd., product name Phenolite), 2-ethyl-4-methylimidazole (3.2 mg) and anisole (18.3 mL) was applied to the entire surface with a spin coater at room temperature and 3000 min ^−1. Applied. Thereafter, the substrate was heated on a hot plate at 80 ° C. for 15 minutes, 130 ° C. for 60 minutes, and 180 ° C. for 60 minutes to advance the polymerization reaction of the mixture to form a gate insulating film of 300 nm. In addition, it was 1000 ppm or less when the hydrolysable chlorine content in a mixture was calculated | required by the titration method using silver nitrate aqueous solution.

Next, a toluene solution of fluorene-benzothiadiazole copolymer (concentration: 1.0 wt%) was applied on the entire surface of the gate insulating film with a spin coater under conditions of room temperature and 3000 min ⁻¹ , and then on a hot plate, 80 The organic semiconductor layer was formed at 80 nm by drying at a temperature of 15 minutes.

  Next, Al was deposited to a thickness of 50 nm by a vacuum vapor deposition method through a metal mask to form a source electrode and a drain electrode. The gate width (W) was 1 mm, and the gate length (L) was 50 μm. In the same manner as in Example 1, voltage-current characteristics were measured.

Figure _16, V D = + during 30 _V, shows the V G -I _D characteristic. When a positive voltage is applied to V _G, I _D increases, the characteristics of the n-channel type was observed. The mobility (μ) was calculated from the V _G- (I _D ) ^1/2 characteristic using Equation 1, and was μ = 3.34 × 10 ⁻⁵ cm ² / Vs.

(Comparative Example 2)
[Production of organic thin film transistor using polyimide as gate insulating film 2]
An organic thin film transistor was prepared in the same manner as in Example 3 except that polyimide was used as the gate insulating film, and voltage-current characteristics were measured. However, the operation as a transistor could not be confirmed.

Example 4
[Fabrication of Organic Thin Film Transistor Using Insulating Film Material of the Present Invention 4]
An n-doped Si wafer was used as the substrate and gate electrode. All subsequent work was performed in a glove box into which nitrogen gas was introduced.

On the substrate on which the gate electrode is formed, a phenol novolac type epoxy resin (2.08 g, epoxy equivalent 205, manufactured by Dainippon Ink and Chemicals, product name EPICLON), bisphenol A novolak (1.14 g, hydroxyl group, etc.) 118, Dainippon Ink & Chemicals, product name Phenolite), 2-ethyl-4-methylimidazole (3.2 mg) and anisole (18.3 mL) were mixed at room temperature, 3000 min ⁻ with a spin coater. ^The coating was applied to the entire surface under the condition of ¹ . Then, it heated at 80 degreeC for 15 minutes, 130 degreeC for 60 minutes, and 180 degreeC for 60 minutes on the hotplate, the polymerization reaction of the mixture was advanced, and 300 nm of gate insulating films were formed. In addition, it was 1000 ppm or less when the hydrolysable chlorine content in a mixture was calculated | required by the titration method using silver nitrate aqueous solution.

Next, according to “S. Ito, N. Ochi, T. Murashima, H. Uno, N. Ono, Heterocycles, 52, 399-411 (2000)” as an organic semiconductor precursor on the gate insulating film. The synthesized chloroform solution (0.4 wt%) of the general formula (1) was spin-coated at 3000 min ⁻¹ . Thereafter, the substrate was heated at 170 ° C. for 30 minutes and at 200 ° C. for 30 minutes to convert to the general formula (2), thereby forming an organic semiconductor layer.

  Next, Au was deposited in a thickness of 30 nm by a vacuum deposition method through a metal mask to form a source electrode and a drain electrode. The gate width (W) was 1 mm, and the gate length (L) was 50 μm. The voltage-current characteristics of the organic thin film transistor thus produced were measured in the same manner as in Example 1.

_17, when the V D = -40 _V, shows the V G -I _D characteristic. When a negative voltage is applied to the V _{G, |} I D | is increased, the characteristics of the p-channel type was observed.
Further, in FIG. 18, in the various _{V G,} it shows a V D -I _D characteristic.

Further, in FIG. _19, V D = + during _60V, shows the V G -I _D characteristic. When a positive voltage is applied to V _G, once the I _D is decreased, it has increased I _D, characteristics of the n-channel type was observed.
Further, in FIG. 20, in the various _{V G,} it shows a V D -I _D characteristic.
Thus, both p-channel and n-channel characteristics were confirmed, and it was confirmed that the organic thin film transistor had ambipolar characteristics.

(Example 5)
[Fabrication of Organic Thin Film Transistor 5 Using Insulating Film Material of the Present Invention]
As gate insulating film materials, phenol novolac type epoxy resin (2.08 g, epoxy equivalent 205, manufactured by Dainippon Ink and Chemicals, product name EPICLON), silylated phenol resin (1.45 g, hydroxyl group equivalent 145, bisphenol) F-type epoxy resin and diphenyldimethoxysilane were reacted with each other), and a mixture consisting of 2-ethyl-4-methylimidazole (3.2 mg) and anisole (18.3 mL) was used in the same manner as in Example 4. An organic thin film transistor was prepared, and voltage-current characteristics were measured. In addition, it was 1000 ppm or less when the hydrolysable chlorine content in a mixture was calculated | required by the titration method using silver nitrate aqueous solution.

_21, when the V D = -40 _V, shows the V G -I _D characteristic. When a negative voltage is applied to the V _{G, |} I D | is increased, the characteristics of the p-channel type was observed.
Further, in FIG. 22, in the various _{V G,} it shows a V D -I _D characteristic.

Further, in FIG. _23, when the V D = + _40V, shows the V G -I _D characteristic. When a positive voltage is applied to V _G, once the I _D is decreased, it has increased I _D, characteristics of the n-channel type was observed.
Further, in FIG. 24, in the various _{V G,} it shows a V D -I _D characteristic.
Thus, both p-type and n-type characteristics were confirmed, and it was confirmed that the organic thin film transistor had ambipolar characteristics.

(Comparative Example 3)
[Preparation of organic thin film transistor using SiO ₂ as gate insulating film]
An organic thin film transistor was fabricated in the same manner as in Example 4 except that SiO ₂ (film thickness 100 nm) was used as the gate insulating film, and voltage-current characteristics were measured. Although p-channel type characteristics were observed, no n-channel type characteristics were observed, and no ambipolar characteristics were observed.

Claims (9)

  An insulating film material for an organic thin film transistor comprising a compound having two or more epoxy groups in the molecule.   An insulating film material for an n-channel or ambipolar organic thin film transistor comprising a compound having two or more epoxy groups in the molecule.   The insulating film material for an organic thin film transistor according to claim 1 or 2, wherein a hydrolyzable chlorine content after curing is 1000 ppm or less.   The insulating film material for an organic thin film transistor according to any one of claims 1 to 3, wherein an epoxy equivalent of a compound having two or more epoxy groups in a molecule is 10,000 or less.   The compound having two or more epoxy groups in the molecule is any one or more selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, and bisphenol A novolak type epoxy resin. The insulating film material for organic thin-film transistors in any one of Claims 1 thru | or 4 containing these.   Furthermore, the insulating film material for organic thin-film transistors of Claim 5 containing any one or more selected from the group which consists of a phenol novolak resin, a bisphenol novolak resin, and a silylated phenol resin.   An organic thin film transistor comprising at least a substrate, an organic semiconductor layer, a gate insulating film, and a conductor, wherein the gate insulating film comprises the organic thin film transistor insulating film material according to any one of claims 1 to 6. Organic thin film transistor formed by using.   8. The organic thin film transistor according to claim 7, which is an n-channel type.   The organic thin film transistor according to claim 7, which is an ambipolar type.

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