JP7211269B2 - Resin composition, organic thin film laminated structure and organic thin film transistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition for forming an insulating layer on an organic semiconductor layer, an organic thin film laminate structure, and an organic thin film transistor.

An organic thin film transistor (organic semiconductor transistor) using an organic semiconductor as an active layer is attracting attention as a technique for use in flexible electronic circuits, display devices, and the like. Organic thin-film transistors are characterized by the fact that they are suitable for weight reduction and thickness reduction, and that elements can be formed by coating. That is, since the organic semiconductor layer, the electrode layer, the insulating layer, and the like can be produced by coating the solution, the circuit of the organic thin film transistor can be produced using a printing apparatus.
In recent years, highly soluble organic semiconductors have been developed, and techniques for forming organic semiconductor layers by coating have improved. However, when laminating the insulating layer on the organic semiconductor layer, the application of a solution containing the material of the insulating layer causes swelling or dissolution of the organic semiconductor layer, which may deteriorate the performance of the organic thin film transistor.
In order to solve this problem, it has been reported that an insulating layer is formed from a solution in which a perfluoro-based polymer that does not dissolve an organic semiconductor layer is dissolved in a perfluoro solvent (Non-Patent Document 1). However, the perfluoropolymer insulating layer has a problem that it is easily separated from the organic semiconductor layer, and the durability of the laminated structure of the organic semiconductor layer and the insulating layer is low.
Also, the use of polymethyl methacrylate (PMMA) or polyvinylphenol (PVP) as an insulating layer has been reported (Non-Patent Document 2). However, since the insulating layer in the document uses butyl acetate as a solvent for the material of the insulating layer, swelling or dissolution occurs when the insulating layer is laminated on the organic semiconductor layer formed of a low-molecular-weight organic semiconductor. There is a problem that the performance of the organic semiconductor layer is deteriorated.

Air Stable Cross-Linked Cytop Ultrathin Gate Dielectric for High Yield Low-Voltage Top-Gate Organic Field-Effect Transistors(Xiaoyang Cheng et al, Chem. Mater. 2010, 22, 1559-1566 DOI:10.1021/cm902929b) Ultra-thin polymer gate dielectrics for top-gate polymer field-effect transistors (Yong-Young Noh et al, Org. Electron. 2009,10, 174-180 DOI:10.1016/j.orgel.2008.10.021)

The present invention provides a resin composition that does not deteriorate the performance of the organic semiconductor layer due to swelling or dissolution when laminated on the organic semiconductor layer, can form an insulating layer that has good adhesion to the organic semiconductor layer, and has good applicability. , to provide a stack structure and an organic thin film transistor.

The present invention provides a resin composition that does not swell or dissolve the organic semiconductor layer when forming the insulating layer on the organic semiconductor layer by using a mixed solvent obtained by mixing an insulating polymer and a plurality of solvents, and that has good coatability. is based on the knowledge that can be prepared, and has the following configuration.

[1] A resin composition containing the following (A) to (D) used for forming an insulating layer on an organic semiconductor layer.
(A) an insulating polymer, (B) a first solvent that dissolves the insulating polymer, (C) a second solvent that does not dissolve the organic semiconductor constituting the organic semiconductor layer, and (D) the first solvent. and a third solvent compatible with each of said second solvents.

[2] The first solvent dissolves both the insulating polymer and the organic semiconductor, and the second solvent dissolves neither the insulating polymer nor the organic semiconductor. , The resin composition according to [1], wherein the third solvent does not dissolve the organic semiconductor.

[3] The first solvent is a non-fluorinated solvent containing no fluorine atoms in the molecule, and the second solvent and the third solvent are fluorine-containing solvents each containing a fluorine atom in the molecule. The resin composition according to [1] or [2], wherein the second solvent and the third solvent have different weight ratios of fluorine atoms in the molecule.

[4] The resin composition according to any one of [1] to [3], wherein the content of the first solvent is 50 parts by volume or less in a total of 100 parts by volume of the first to third solvents. thing.
[5] The insulating polymer according to any one of [1] to [4], wherein the number of fluorine atoms accounts for 50% or less of the total number of hydrogen atoms and halogen atoms contained in the repeating unit. The described resin composition.
[6] The resin composition according to any one of [1] to [5], wherein the insulating polymer is a (meth)acrylic resin.
[7] The resin composition according to any one of [1] to [6], further comprising (E) a coupling agent.

[8] An organic thin film laminated structure comprising an organic semiconductor layer formed on a substrate and an insulating layer laminated in contact with the organic semiconductor layer, wherein the insulating layer is [1] to [7] An organic thin film laminate structure formed using the resin composition according to any one of .
[9] The organic thin film laminated structure according to [8], wherein the organic semiconductor has a molecular weight of 2000 or less.

[10] An organic thin film transistor comprising the organic thin film multilayer structure according to [8], a source electrode, a drain electrode and a gate electrode.
[11] The source electrode and the drain electrode are formed on the substrate, the organic semiconductor layer is laminated to cover the substrate, the source electrode and the drain electrode, and the gate electrode is the insulating layer. The organic thin film transistor according to [10], which is formed in
[12] The source electrode and the drain electrode are formed on the organic semiconductor layer, the insulating layer is laminated to cover the organic semiconductor layer, the source electrode and the drain electrode, and the gate electrode is The organic thin film transistor according to [10], which is formed on the insulating layer.

[13] The gate electrode is formed on the substrate, a second insulating layer is formed on the substrate so as to cover the gate electrode, and the source electrode and the drain electrode form the second insulating layer. wherein the organic semiconductor layer is laminated over the second insulating layer, the source electrode and the drain electrode, and a first insulating layer is laminated on the organic semiconductor layer. The organic thin film transistor according to [10].
[14] The gate electrode is formed on the substrate, a second insulating layer is formed on the substrate so as to cover the gate electrode, and the organic semiconductor layer is laminated on the second insulating layer. wherein the source electrode and the drain electrode are formed on the organic semiconductor layer, and a first insulating layer is laminated on the organic semiconductor layer, the source electrode and the drain electrode [10] The organic thin film transistor described.

According to the present invention, by using a specific mixed solvent as a solvent for the insulating polymer, it is possible to suppress swelling and dissolution of the organic semiconductor layer when laminating the insulating layer. Moreover, by using a mixture of a plurality of types of solvents, it is possible to adjust the applicability of the resin composition containing the insulating polymer. Therefore, it is possible to provide an organic thin film laminated structure and an organic thin film transistor in which an insulating layer having good adhesion is laminated on an organic semiconductor layer without degrading the performance of the organic semiconductor layer.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows typically the organic thin film lamination structure of this invention. (a) Cross-sectional view schematically showing the structure of an organic thin-film transistor having a bottom-contact/top-gate structure, (b) Cross-sectional view schematically showing the structure of an organic thin-film transistor having a top-contact/top-gate structure, (c) ) Cross-sectional view schematically showing the structure of an organic thin-film transistor having a bottom-contact/bottom-gate structure, (d) Cross-sectional view schematically showing the structure of an organic thin-film transistor having a top-contact/bottom-gate structure (a) to (c) Graphs showing the electrical characteristics of the organic thin film transistor produced using the laminated structure of Example 2 (Vd = -5 [V]) (a) to (c) Graphs showing the electrical characteristics of the organic thin film transistor produced using the laminated structure of Example 2 (Vd = -30 [V])

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The examples described in the embodiments are intended to facilitate understanding of the present invention, and the present invention can be implemented in aspects other than those illustrated.

[Resin composition]
The resin composition of the present invention is for forming an insulating layer on an organic semiconductor layer, comprising (A) an insulating polymer, (B) a first solvent that dissolves the insulating polymer, (C) the organic It contains a second solvent that does not dissolve the semiconductor layer, and (D) a third solvent that is compatible with each of the first solvent and the second solvent.

[(A) Insulating polymer]
The insulating polymer is a material for the insulating layer, and is preferably an insulating material that is less likely to mix with or interact with the organic semiconductor layer. Examples of such insulating materials include resins whose main skeleton is mainly composed of saturated hydrocarbons (polyolefin resins), resins whose main skeletons are mainly composed of saturated hydrocarbons and aromatic hydrocarbons, and fluorinated polymers ( fluorinated polymer), polysiloxane, and the like. These resins can be used singly or in combination of two or more.

The insulating layer preferably has low interaction with the organic semiconductor layer and also has good adhesion to the organic semiconductor layer. From the viewpoint of improving adhesion to the organic semiconductor layer, it is preferable that the insulating polymer has 50% or less fluorine atoms in the total number of hydrogen atoms and halogen atoms contained in the repeating unit. , 30% or less, and more preferably 0%, that is, no fluorine atom is contained in the repeating unit.

Specific examples of the insulating polymer containing no fluorine atom in the repeating unit include (meth)acrylic resin, polyvinylpyrrolidone, polystyrene, polystyrene-ethylene copolymer, polyvinylcyclohexane, and the like. These can be used singly or in combination of two or more.

From the viewpoint of improving the adhesion to the organic semiconductor layer, the insulating polymer is preferably a (meth)acrylic resin. The (meth)acrylic resin preferably has a weight average molecular weight of 1,000 to 500,000, more preferably 2,000 to 100,000, and even more preferably 3,000 to 20,000. In the present specification, the numerical range A to B means A or more and B or less. In addition, the (meth)acrylic resin has good solubility in the first solvent, and also has the advantage of being excellent in handleability when forming an insulating layer with a desired thickness on the organic semiconductor layer.

[(B) First solvent]
The first solvent dissolves the insulating polymer and functions as a solvent or dispersion medium for the insulating polymer. In the present invention, “dissolving the insulating polymer” means that the solubility of the insulating polymer forming the insulating layer at room temperature (25° C.) is 0.1% by weight or more. From the viewpoint of reducing the number of coatings required for forming the insulating layer, the solubility of the insulating polymer in the first solvent is preferably 1% by weight or more, more preferably 10% by weight or more.

The first solvent may dissolve the organic semiconductor in addition to the insulating polymer. In the present invention, "to dissolve an organic semiconductor" means that the solubility at room temperature (25°C) of the organic semiconductor used for forming the organic semiconductor layer is 0.0003% by weight or more. A mixed solvent that does not dissolve the organic semiconductor can be obtained by mixing the first solvent that dissolves the organic semiconductor with a second solvent and a third solvent that will be described later.

The first solvent is, for example, an aliphatic hydrocarbon solvent such as pentane, hexane, heptane; an alicyclic hydrocarbon solvent such as cyclohexane; an aromatic hydrocarbon solvent such as benzene, toluene, xylene; Hydrocarbon solvents; halogenated hydrocarbon solvents such as dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene and dichlorobenzene; heterocyclic solvents such as 3-chlorothiophene; diethyl ether, t-butyl methyl ether, tetrahydrofuran, dioxane Ether or alcohol solvents such as , methanol, ethanol, isopropanol, butyl cellosolve; Ester solvents such as ethyl acetate, ethyl lactate, γ-butyrolactone; Ketone solvents such as acetone, cyclopentanone, cyclohexanone; Acetonitrile, N-methyl-2-pyrrolidone , N,N-dimethylformamide; and organic solvents such as sulfur-containing solvents such as dimethylsulfoxide. From the viewpoint of dissolving the insulating polymer at a high concentration, non-fluorine-based solvents containing no fluorine atoms in the molecule are preferred.

[(C) Second solvent]
The second solvent does not dissolve the organic semiconductor, and prevents the organic semiconductor layer from swelling or dissolving when the organic semiconductor layer is laminated to cover the insulating layer with the solution containing the insulating polymer. In the present invention, "does not dissolve the organic semiconductor" means that the solubility of the organic semiconductor used for forming the organic semiconductor layer at room temperature (25°C) is less than 0.0003% by weight.

Solubility in a solvent varies depending on the type of organic semiconductor. Low-molecular-weight organic semiconductors are more soluble in organic solvents than high-molecular-weight organic semiconductors. Therefore, when an insulating layer is formed on an organic semiconductor layer formed using a low-molecular-weight organic semiconductor, the organic semiconductor layer tends to swell or dissolve. Therefore, the resin composition of the present invention uses a low-molecular-weight organic semiconductor by mixing a first solvent that dissolves an insulating polymer with a second solvent that does not dissolve an organic semiconductor and a third solvent. It is possible to suppress the occurrence of swelling and dissolution in the organic semiconductor layer formed by A low-molecular-weight organic semiconductor is an organic semiconductor that does not have a repeating structure of basic units.

The smaller the molecular weight of the low-molecular-weight organic semiconductor, the more likely it is to swell or dissolve when laminating an insulating layer. By adjusting the mixing ratio of the first solvent and the second solvent, for example, an organic semiconductor layer formed using a low-molecular-weight organic semiconductor having a molecular weight of 1500 or less, or further 1000 or less, swells or dissolves. An insulating layer can be formed without causing

The organic semiconductor layer can be formed by combining one or more organic semiconductors. When the organic semiconductor layer is composed of two or more kinds of organic semiconductors, the weight average molecular weights of the plurality of organic semiconductors are used as the molecular weight of the organic semiconductor.

A fluorine-based solvent containing a fluorine atom in the molecule can be used as the second solvent. From the viewpoint of improving the orthogonality with the organic semiconductor, the weight ratio of fluorine atoms in the molecules of the fluorine-based solvent is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more.

((D) third solvent)
The third solvent is compatible with each of the first solvent and the second solvent. In the present invention, the term "exhibiting compatibility" means that no separation occurs when a solvent is mixed at a weight ratio of 1:1 at room temperature, ultrasonic waves are applied for 10 minutes, and the mixture is allowed to stand for 1 hour. .

A fluorine-based solvent can be used as the third solvent in the same manner as the second solvent, but the weight ratio of fluorine atoms in the molecule is different from that of the second solvent. In addition to the first and second solvents, the use of a third solvent compatible with each of them facilitates preparation of a resin composition having a high resin content. Therefore, it is possible to improve the coatability of the resin composition when forming a film of the solution containing the insulating polymer on the organic semiconductor layer in a desired shape.
In the third solvent, from the viewpoint of improving compatibility with each of the first and second solvents, the weight ratio of fluorine atoms in the molecule of the fluorine-based solvent is preferably 20 to 80%. ~75% is more preferred, and 55-70% is even more preferred.

From the viewpoint of adjusting and increasing the concentration of the resin composition, the third solvent preferably has a higher solubility of the insulating polymer at room temperature than the second solvent. Therefore, as the third solvent, a solvent that dissolves the insulating polymer but does not dissolve the organic semiconductor layer may be used.

The solubility of the insulating polymer in fluorine-based solvents at room temperature is, for example, polymethacryl The solubility of methyl acid (PMMA, weight average molecular weight 15,000) is used for evaluation. When the resin composition contains two types of fluorinated solvents, the fluorinated solvent used in the mixed solvent that dissolves PMMA at a higher concentration is the third solvent.

(fluorinated solvent)
A fluorine-based solvent is a solvent having a fluorine atom in its molecule, and is used as the second solvent and the third solvent. By using a mixture of two or more fluorine-based solvents as a solvent for the insulating polymer, the property of not swelling or dissolving the organic semiconductor layer (hereinafter also referred to as “orthogonality” as appropriate) and the insulating polymer can be easily formed. It becomes a resin composition having a property that it can be applied to a surface (hereinafter also referred to as “applicability” as appropriate).

Fluorinated solvents can be used as the second and third solvents. Therefore, the fluorine-based solvent can be used as the second solvent or the third solvent depending on the combination. That is, the same fluorine-based solvent becomes the second solvent or the third solvent depending on the organic semiconductor layer, the insulating polymer and the first solvent contained in the resin composition.

When using two types of fluorine-based solvents, both of which have orthogonality to the organic semiconductor layer and compatibility with the first solvent and another fluorine-based solvent (second or third solvent), A fluorine-based solvent in which the insulating polymer is highly soluble is used as the third solvent. Here, the high solubility of the insulating polymer means that the insulating polymer has high solubility at room temperature, or that the same concentration of the insulating polymer can be dissolved at a lower temperature.

Examples of fluorine-based solvents include 2H,3H-decafluoropentane, perfluoropentane, trifluoroethanol, tetrafluoro-1-propanol, hexafluoro-2-propanol, ethyl trifluoroacetate, perfluorotributylamine, perfluoro toluene, 1,3-(trifluoromethyl)benzene, perfluorodecalin, octadecafluorodecahydronaphthalene, perfluorocyclopentene and the like. Commercially available products include, for example, various types of Novec represented by Novec7100 manufactured by 3M, various types of Fluorinert represented by FC-43, and CT-Solv. 180 and the like.

By adjusting the contents of the first to third solvents described above according to the types of the organic semiconductor and the insulating polymer, a resin composition having excellent applicability and orthogonality to the organic semiconductor layer can be obtained. From the viewpoint of improving the orthogonality to the organic semiconductor layer formed by the low-molecular-weight organic semiconductor, the content of the first solvent in the total 100 parts by volume of the first to third solvents is 50 parts by volume or less. It is preferably 30 volume parts or less, more preferably 10 volume parts or less. From the same point of view, the combined content of the second solvent and the third solvent in the total 100 parts by weight of the first to third solvents is preferably 50 parts by volume or more, more preferably 70 parts by volume or more. , more preferably 90 parts by volume or more.

[(E) Coupling agent]
The resin composition preferably contains a coupling agent in addition to the components described above. By containing a coupling agent, the adhesion between the organic semiconductor layer and the insulating layer can be enhanced. As the coupling agent, a silane-based coupling agent such as fluoroalkyltriethoxysilane is preferred. The following (a) to (e) are preferable, and (a) and (b) are more preferable, from the viewpoint of forming an insulating layer having good adhesion to the organic semiconductor layer.

Examples of silane coupling agents include 1H,1H,2H,2H,-heptadecafluorodecyltriethoxysilane, 1,2-bis(triethoxysilyl)ethane, (pentafluorophenyl)triethoxysilane, triethoxyphenyl Silane, 3-(triethoxysilyl)propyl methacrylate, tetraethyl orthosilicate, triethoxymethylsilane, (3-aminopropyl)triethoxysilane, etc., and non-silane coupling agents include pentafluorobenzenethiol. is mentioned.
The amount of the coupling agent compounded may be, for example, about 1 part by weight in 100 parts by weight of the resin composition.

[Laminate structure]
An organic thin film laminate structure can be produced using the resin composition of the present invention. If the insulating layer is formed using the resin composition described above, it is possible to suppress deterioration in the performance of the organic thin film lamination due to dissolution or swelling. Also, it is possible to provide an organic thin film lamination structure having good adhesion between the insulating layer and the organic thin film lamination.

FIG. 1 is a cross-sectional view showing the configuration of an organic thin film laminated structure 1 of the present invention. As shown in the figure, the organic thin film laminated structure 1 comprises an organic semiconductor layer 12 formed on a substrate 11 and an insulating layer 13 covering the organic semiconductor layer 12 laminated thereon. Hereinafter, members having the same function are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The substrate 11 supports the organic semiconductor layer 12 and the insulating layer 13. Examples of the substrate 11 include a glass substrate, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), aromatic polyester ( A plastic substrate (resin substrate) made of liquid crystal polymer) or the like, a quartz substrate, a silicon substrate, a gallium arsenide substrate, or the like can be used. When the organic thin film laminated structure 1 having flexibility is used, the substrate 11 is made of resin.

The substrate 11 may have a self-assembled monolayer (SAM) formed using a known silane coupling agent. Silane coupling agents include, for example, hexamethyldisilazane, decyltriethoxysilane, triethoxytridecafluorooctylsilane, phenethyltriethoxysilane, and (3-mercaptopropyl)triethoxysilane. The surface treatment can adjust the liquid repellency of the substrate 11 and the film quality of the organic semiconductor layer 12 .

The organic semiconductor layer 12 is mainly composed of an organic semiconductor compound exhibiting semiconductor-like electrical conductivity. Examples of organic semiconductor compounds include naphthalene, anthracene, tetracene, pentacene, hexacene, phthalocyanine, perylene, hydrazone, triphenylmethane, diphenylmethane, stilbene, arylvinyl, pyrazoline, triphenylamine, triarylamine, oligothiophene, phthalocyanine or Low-molecular-weight organic semiconductor compounds such as derivatives thereof, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylenevinylene), polytinylenevinylene, Polymer organic semiconductor compounds (conjugated polymer materials) such as polyarylamines, pyrene formaldehyde resins, ethylcarbazole formaldehyde resins, fluorene-bithiophene copolymers, fluorene-arylamine copolymers, or derivatives thereof. . These organic semiconductor compounds can be used singly or in combination of two or more.

Thianoacene (thiophene-containing condensed polycyclic aromatic compound) derivatives have attracted attention as materials exhibiting high mobility among low-molecular-weight organic semiconductor compounds.
Thianoacenes include, for example, dinaphthothiophene, dianthrathiophene, dinaphthothienothiophene, benzothienobenzothiophene, and dinaphthobenzodithiophene.

３，９－ジヘキシル ジナフト［２，３－ｂ：２′，３′－ｄ］チオフェン（3,9-dihexyl dinaphtho[2,3-b:2′,3′-d]thiophene、分子量４５２．７０、Ｃ６－ＤＮＴ－ＶＷ） Specific examples of thianocene derivatives include the compounds shown below.

3,9-dihexyl dinaphtho[2,3-b:2′,3′-d]thiophene (molecular weight 452.70 , C6-DNT-VW)

（３，１１－ジノニル ジナフト［２，３－ｄ：２′，３′－ｄ′］ベンゾ［１，２－ｂ：４，５－ｂ’］ジチオフェン(3,11- dinonyl dinaphtho[2,3-d:2′,3′-d′]benzo[1,2-b:4,5 b’]dithiophene)、分子量６４３．００、Ｃ９－ＤＮＢＤＴ－ＮＷ）

(3,11-dinonyl dinaphtho[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (3,11-dinonyl dinaphtho[2,3 -d:2′,3′-d′]benzo[1,2-b:4,5 b′]dithiophene), molecular weight 643.00, C9-DNBDT-NW)

（２－デシル－７－フェニル［１］ベンゾチエノ［３，２－ｂ］［１］ベンゾチオフェン（2-Decyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene）、分子量４５６．７１、Ｐｈ－ＢＴＢＴ－Ｃ１０）

(2-Decyl-7-phenyl[1]benzothieno[3,2-b][1]benzothiophene, molecular weight 456.71, Ph-BTBT-C10)

The insulating layer 13 constituting the organic thin film laminate structure 1 is formed using the resin composition of the present invention. Therefore, even the organic semiconductor layer 12 made of a low-molecular-weight organic semiconductor compound can be prevented from swelling and dissolving when the insulating layer 13 is laminated. Therefore, the organic thin film laminated structure 1 can maintain its function without degrading the performance of the organic semiconductor layer 12 when laminating the insulating layer 13 .

As described above, in general, the organic semiconductor layer 12 formed of a low-molecular-weight organic semiconductor compound having a small molecular weight is more soluble in an organic solvent than that formed of a high-molecular-weight organic semiconductor compound having a large molecular weight. highly sexual. The resin composition of the present invention can adjust the solubility (orthogonality) with respect to the organic semiconductor layer 12 by mixing and using the first to third solvents. Therefore, even if the organic semiconductor layer 12 is made of an organic semiconductor compound having a molecular weight of 2000 or less, 1500 or less, or even 1000 or less, the insulating layer 13 can be formed on the organic semiconductor layer 12 without deteriorating performance due to dissolution or swelling. can be stacked.

Examples of low-molecular-weight organic semiconductor compounds having a molecular weight of 2,000 or less include the following, in addition to the specific examples of thianocene derivatives.

（N,N'-Di-n-octyl-3,4,9,10-perylenetetracarboxylic Diimide、分子量６１４．７９、ＰＴＣＤＩ－Ｃ８）

（5,5'-(9,9'-spirobi[fluorene]-2,7-diyl)bis(2,9-di(tridecan-7-yl)anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline)-1,3,8,10(2H,9H)-tetraone、分子量１８２２．４８、ＳＦ－ＰＤＩ）

(N,N'-Di-n-octyl-3,4,9,10-perylenetetracarboxylic Diimide, molecular weight 614.79, PTCDI-C8)

(5,5'-(9,9'-spirobi[fluorene]-2,7-diyl)bis(2,9-di(tridecan-7-yl)anthra[2,1,9-def:6,5 ,10-d'e'f']diisoquinoline)-1,3,8,10(2H,9H)-tetraone, molecular weight 1822.48, SF-PDI)

(organic thin film transistor)
The present invention can be implemented as an organic thin film transistor including the organic thin film laminated structure described above, a source electrode, a drain electrode, and a gate electrode. Organic thin film transistors are used, for example, as switching elements of flexible displays.
FIGS. 2(a) and 2(b) show an organic thin film laminate structure 1 (see FIG. 1) in which an organic semiconductor layer 12 and an insulating layer 13 are laminated on a substrate 11, in addition to a source electrode 14 and a drain electrode 15. 2 is a cross-sectional view schematically showing the structure of organic thin-film transistors 2 and 3 having a top-gate structure in which is provided closer to the substrate 11 than the gate electrode 16. FIG.

The organic thin film transistor 2 having the bottom contact/top gate structure shown in FIG. 2(a) will be described below.
The substrate 11 supports each layer (each portion) that constitutes the organic thin film transistor 2 . An underlying layer may be provided on the substrate 11 . For example, the underlying layer has the effect of preventing diffusion of ions from the surface of the substrate 11 or the effect of improving the adhesion between the source electrode 14 and the drain electrode 15 and the substrate 11 . The underlayer can be composed of, for example, silicon oxide (SiO ₂ ), silicon nitride (SiN), polyimide, polyamide, polymer made insoluble by cross-linking, or the like.

A source electrode 14 and a drain electrode 15 are arranged side by side on the substrate 11 with a predetermined distance therebetween along the channel length direction. The source electrode 14 and the drain electrode 15 are made of metal materials such as Ag, Al, Au, Cr, Cu, In, Mo, Nb, Nd, Ni, Pd, Pt, Ta, Ti, W, or alloys containing these. is constructed using Materials used for the source electrode 14 and the drain electrode 15 may be appropriately selected depending on the charge injection into the organic semiconductor layer.

Materials constituting the source electrode 14 and the drain electrode 15 include, in addition to metal materials, conductive oxides such as ITO, FTO, ATO, and _SnO2 ; carbon materials such as carbon black, carbon nanotubes, and fullerene; polyacetylene, polypyrrole; Polythiophene such as PEDOT (poly-ethylenedioxythiophene), polyaniline, poly(p-phenylene), poly(p-phenylenevinylene), polyfluorene, polycarbazole, polysilane, or conductive polymer materials such as derivatives thereof. , one or more of these may be used in combination. The conductive polymer materials described above are usually doped with iron chloride, iodine, an inorganic acid, an organic acid, a polymer such as polystyrene sulfonic acid, or the like, and used in a state of being imparted with conductivity.

The thickness of the source electrode 14 and the drain electrode 15, and the channel length and channel width of these electrodes are appropriately set according to the application. And it is sufficient.

In order to increase the efficiency of charge injection from the source electrode 14 and the drain electrode 15 to the organic semiconductor layer 12, the source electrode 14 and the drain electrode 15 can be surface-treated or provided with a carrier injection layer. Examples of the surface treatment include UV-O ₃ treatment, plasma treatment using O ₂ and the like, and treatment for forming a self-assembled monolayer represented by pentafluorobenzenethiol.

When a carrier injection layer is provided, the carrier injection layer provided between the source electrode 14/organic semiconductor layer 12 and the carrier injection layer provided between the drain electrode 15/organic semiconductor layer 12 may be made of the same material. , may be made of different materials. The carrier injection layer is formed using compounds such as tetrafluorotetracyanoquinodimethane, hexaazatriphenylenehexacarbonitrile and molybdenum oxide.

The organic semiconductor layer 12 is formed on the substrate 11 in contact with the source electrode 14 and the drain electrode 15 so as to entirely cover these electrodes. The same organic semiconductor as used in the organic thin film laminate structure 1 (see FIG. 1) can be used for forming the organic semiconductor layer 12 . The organic semiconductor layer 12 can be made thinner and lighter, and has excellent flexibility, so it is suitable for application to the organic thin film transistor 2 . The average thickness of the organic semiconductor layer 12 is, for example, about 1 to 500 nm.

FIG. 2A shows a configuration in which the organic semiconductor layer 12 is provided so as to cover the source electrode 14 and the drain electrode 15, but the configuration is not limited to this, and the region between the source electrode 14 and the drain electrode 15 A configuration in which the organic semiconductor layer 12 is provided only in (the channel region) may be employed.

In the organic thin film transistor 2 , an insulating layer 13 is laminated so as to cover the organic semiconductor layer 12 , and a gate electrode 16 is provided on the insulating layer 13 . The insulating layer 13 insulates the source electrode 14 and the drain electrode 15 from the gate electrode 16 .

Depending on the weight-average molecular weight of the insulating polymer used as the material of the insulating layer 13, the viscosity of the resin composition may increase and the coating properties of the resin composition may deteriorate. For example, when a layer of a resin composition is formed using an inkjet method, ejection of droplets may become unstable. Therefore, from the viewpoint of improving the applicability of the resin composition, the weight-average molecular weight of the insulating polymer that is the material of the insulating layer 13 is preferably 1,000 to 500,000, more preferably 2,000 to 100,000. , 3,000 to 20,000 are more preferred. Also, the insulating polymer having a lower weight-average molecular weight has a higher solubility in a solvent. Therefore, by using the insulating polymer having a relatively low weight-average molecular weight as described above, the concentration of the resin composition can be increased and the insulating layer 13 can be formed with a small number of applications. Note that the insulating layer 13 is not limited to a single-layer structure, and may have a laminated structure of two or more layers.

The gate electrode 16 is formed on the insulating layer 13 stacked on the organic semiconductor layer 12 . The gate electrode 16 is provided so as to overlap at least a region between the source electrode 14 and the drain electrode 15 . As a material for forming the gate electrode 16, the same material as for the source electrode 14 and the drain electrode 15 can be used. Although the thickness of the gate electrode 16 is not particularly limited, for example, the average thickness is about 10 to 1000 nm.

FIG. 2(b) is a cross-sectional view schematically showing the structure of an organic thin film transistor having a top-contact/top-gate structure. The organic thin-film transistor 3 shown in the figure has a source electrode 14 and a drain electrode 15 provided on the surface of an organic semiconductor layer 12 provided on a substrate 11. It is provided on the substrate 11 so as to cover the electrode 15 . The gate electrode 16 is formed on the insulating layer 13 as in the organic thin film transistor 2 .

The organic thin film transistor of the present invention can also be implemented as a bottom gate structure in which the gate electrode is provided closer to the substrate than the source and drain electrodes.
FIG. 2(c) is a cross-sectional view schematically showing the structure of the organic thin film transistor 4 having a bottom contact/bottom gate structure according to this embodiment. As shown in the figure, the organic thin film transistor 4 has a gate electrode 16 formed on a substrate 11 and an insulating layer 17 formed on the substrate 11 so as to cover the gate electrode 16 . A source electrode 14 and a drain electrode 15 are formed on the surface of an insulating layer 17, an organic semiconductor layer 12 is laminated on the insulating layer 17 so as to cover the source electrode 14 and the drain electrode 15, and an insulating layer 13 is an organic semiconductor layer. It is laminated to cover layer 12 and insulating layer 13 .

FIG. 2(d) is a cross-sectional view showing another configuration example of the organic thin film transistor having a top-contact/bottom-gate structure. As shown in the figure, the organic thin-film transistor 5 has a gate electrode 16 formed on a substrate 11, an insulating layer 17 formed on the substrate 11 so as to cover the gate electrode 16, and an organic semiconductor layer 12. It is laminated on the insulating layer 17 . A source electrode 14 and a drain electrode 15 are formed on the organic semiconductor layer 12 , and an insulating layer 13 is laminated on an insulating layer 17 so as to cover the organic semiconductor layer 12 , the source electrode 14 and the drain electrode 15 .

In each of the organic thin film transistors 2 to 5 shown in FIGS. 2(a) to 2(d), the insulating layer 13 laminated in contact with the organic semiconductor layer 12 is formed of the resin composition of the present invention. . Therefore, when laminating the insulating layer 13 on the organic semiconductor layer 12 , swelling or dissolution of the organic semiconductor layer 12 can be suppressed, and deterioration of the performance of the organic semiconductor layer 12 can be prevented.

Examples of the present invention are described below, but the present invention is not limited to these examples. Raw materials used in Examples and Comparative Examples are shown below.
<(A) Insulating polymer>
Polymethyl methacrylate (PMMA, weight average molecular weight 15,000)
<(B) First Solvent>
PGMEA: 2-methoxy-1-methylethyl acetate AcOEt: ethyl acetate toluene chloroform <(C) second solvent>
HFIP: hexafluoro-2-propanol <(D) third solvent>
Novec7300: hydrofluoroether <(E) coupling agent>
17FDTES: 1H,1H,2H,2H,-heptadecafluorodecyltriethoxysilane Et (TES) ₂ : 1,2-bis(triethoxysilyl)ethane F5B-TES: (pentafluorophenyl)triethoxysilane PhTES: tri Ethoxyphenylsilane MA-Pr-TES: 3-(triethoxysilyl)propyl methacrylate EtO-TES: Tetraethyl orthosilicate PFBT: Pentafluorobenzenethiol <Insulating layer forming resin>
CYTOP (CTL-809A, 9% by mass solution, amorphous fluororesin, manufactured by AGC Co., Ltd.)
<Organic semiconductor compound>
C6-DNT-VW: 3,9-dihexyl dinaphtho[2,3-b:2',3'-d]thiophene C9-DNBDT-NW: 3,11-dinonyl dinaphtho[2,3-d:2', 3′-d′]benzo[1,2-b:4,5-b′]dithiophene <substrate>
Silicon substrate (100 nm of the surface is converted to SiO ₂ by thermal oxidation treatment)

In Reference Examples, Examples, and Comparative Examples, organic semiconductor layers were formed using low-molecular-weight organic semiconductor compounds. Low-molecular-weight organic semiconductor compounds have good coatability, but have high solubility in organic solvents. Therefore, when laminating the insulating layer on the organic semiconductor layer, the organic semiconductor layer is likely to be dissolved or swelled.

(Reference example)
C6-DNT-VW was dissolved in a mixed solvent of toluene and ortho-dichlorobenzene (toluene: ortho-dichlorobenzene-=2:1, volume (volume) ratio) to a concentration of about 0.5% by mass, and polystyrene (weight An average molecular weight of 3,000) was added to 0.2% by mass to prepare an organic semiconductor solution. A silicon substrate with a SiO ₂ film that had been subjected to UV-O ₃ treatment for 30 minutes was placed on a spin coater, about 10 ml of the organic semiconductor solution was dropped, applied at 1,000 rpm for 5 seconds, and a hot plate at 120 ° C. was applied. and dried for 5 minutes to obtain a substrate sample having an organic semiconductor layer formed thereon.
The sample was added to a mixed solvent obtained by mixing an organic solvent and a fluorinated solvent shown in Table 1 at a ratio shown in Table 1 (organic solvent: fluorinated solvent = 6:4 to 1:9, volume (volume) ratio), Half of the substrate was immersed in the closed container for 1 minute. After the immersion, the sample was taken out from the container, dried by an air blow, and then the surface condition was observed. Table 1 shows the results.

As shown in the results of Table 1, by using a mixed solvent in which a fluorine-based solvent is added to a non-fluorine-based solvent, an organic semiconductor compound that dissolves in toluene at room temperature in an amount of 0.5% by mass or more and has high solubility in organic solvents. Dissolution of the organic semiconductor layer formed of (C6-DNT-NW) could be prevented.
When using an organic semiconductor compound that is highly soluble in an organic solvent, such as the C6-DNT-NW organic semiconductor layer, the content of the fluorine-based solvent in the mixed solvent is 90 from the viewpoint of stably preventing dissolution. % by volume (% by volume) or more is preferable.

(resin composition)
(Example 1)
A resin composition shown below was prepared.
Resin composition: PMMA is dissolved in a mixed solvent of PGMEA, HFIP and Novec7300 (5) (PGMEA: HFIP: Novec7300 = 1:4:5, volume ratio) so that PMMA becomes 5% by mass. prepared.
C9-DNBDT-NW was dissolved in a mixed solvent of mesitylene and orthodichlorobenzene (mesitylene: orthodichlorobenzene = 1:1, volume ratio) so that the concentration was about 0.2% by mass, and polystyrene (weight average molecular weight 3, 000) was added to 0.1% by mass to prepare an organic semiconductor solution.
A silicon substrate with a SiO ₂ film that had been subjected to UV-O ₃ treatment for 30 minutes was placed on a spin coater (manufactured by Mikasa: MS-A100), and 100 μl of the organic semiconductor solution was dropped and applied at 1,000 rpm for 5 seconds. Then, the substrate was moved to a hot plate at 120° C. and dried for 5 minutes to form an organic semiconductor layer.
The substrate on which the organic semiconductor layer was formed was placed on a spin coater, and about 200 μl of the resin composition was dropped and coated at 2,000 rpm for 30 seconds. After drying for 10 minutes, the substrate was transferred to a hot plate at 120° C. and dried for 10 minutes to form an insulating layer. As a result of film thickness measurement with a palpable profilometer, the film thickness was about 1 μm.
The resin composition had good applicability, and a film could be formed on the substrate on which the organic semiconductor layer was formed by the method described above.
(Comparative example 1)
Resin composition: PGMEA and Novec7300 were mixed (PGMEA:Novec7300=1:9, volume ratio) so that PMMA was 3% by mass. When Novec 7300 was added to a solution of PMMA and PGMEA, PMMA precipitated and a resin composition could not be prepared.
(Comparative example 2)
Resin composition: A resin composition was prepared by mixing PGMEA and HFIP (PGMEA:HFIP=1:9, volume ratio) so that PMMA would be 3% by mass. The resin composition had poor applicability, and it was not possible to form a film on the substrate on which the organic semiconductor layer was formed by the method described above.

The following organic thin film laminated structure was produced, and a cross stitch test (JIS-K-5400) by tape peeling was performed, and the number of remaining layers was counted to evaluate the adhesion between the organic semiconductor layer and the insulating layer.
Table 2 shows the remaining number of 100 squares according to the ratio of the remaining region of the insulating layer. For example, in the organic thin film laminated structure of Example 2, out of 100 squares, 57 had an area of 10% or more remaining, 6 had an area of 50% or more, and 100% of the area indicates that 0 remained.

(Organic thin film laminated structure)
(Example 2)
Using the resin composition of Example 1, an organic semiconductor layer was formed under the same conditions as in Example 1 to produce an organic thin film laminate structure.
(Example 3)
An organic thin film laminate structure was produced in the same manner as in Example 2, except that 1% by mass of (E) 17FDTES was added to the resin composition of Example 1.
(Examples 4-9)
Instead of 17FDTES, Et(TES) ₂ (Example 4), PFBT (Example 5), F5B-TES (Example 6), Ph-TES (Example 7), MA-Pr-TES (Example 8 ) or EtO-TES (Example 9) was used in the same manner as in Example 3 to fabricate an organic thin film laminate structure.

(Comparative Example 3)
A resin composition containing CYTOP was used to form an insulating layer, and an organic thin film laminate structure was produced as follows.
CYTOP (CTL-809A, 9% by mass solution) was treated with CT-Solv. 180 and adjusted to 7% by mass was used as a resin composition. The coating conditions were as follows: a substrate having the same organic semiconductor layer as in Example 1 was placed on a spin coater, about 200 µl of the resin composition was dropped, applied at 1,000 rpm for 30 seconds, and hot at 60 °C. The substrate was transferred to a plate and dried for 5 minutes, and then transferred to a hot plate at 120° C. and dried for 10 minutes to form an insulating layer. As a result of film thickness measurement with a palpable profilometer, the film thickness was about 1 μm.
(Comparative Example 4)
Instead of the substrate on which the organic semiconductor layer was formed used in Comparative Example 3, a silicon substrate with a SiO ₂ film which had been subjected to UV-O ₃ treatment for 30 minutes was used to directly form an insulating layer on the substrate.

比較例３、４の結果から、ＣＹＴＯＰを用いた絶縁層は、シリコン基板との密着性は良好であるものの、有機半導体層との密着性が悪いことが分かった。ＣＹＴＯＰに代えてＰＭＭＡを用いた絶縁膜は、有機半導体層との密着性が良好であった。また、樹脂組成物に（Ｅ）カップリング剤を添加することにより、有機半導体層と絶縁層との密着性を向上させることができ、シラン系カップリング剤が密着性を向上させる効果に優れていた。

From the results of Comparative Examples 3 and 4, it was found that the insulating layer using CYTOP has good adhesion to the silicon substrate, but poor adhesion to the organic semiconductor layer. The insulating film using PMMA instead of CYTOP had good adhesion to the organic semiconductor layer. Further, by adding the (E) coupling agent to the resin composition, the adhesion between the organic semiconductor layer and the insulating layer can be improved, and the silane coupling agent is excellent in the effect of improving the adhesion. rice field.

(organic thin film transistor)
(Example 13)
Using the resin composition of Example 3, an organic thin film transistor was produced and its electrical characteristics were evaluated.
A mixed solvent was prepared by mixing ethanol and water at a volume ratio of 8:2, and MPTES ((3-Mercaptopropyl)triethoxysilane) was added to 0.1 v/v% (vol%) to adjust the MPTES solution. bottom. A silicon substrate with a SiO ₂ film that had been subjected to UV-O ₃ treatment for 30 minutes was immersed in the MPTES solution for 10 minutes, air blown, and then dried on a hot plate at 120°C. This substrate was placed in a vapor deposition apparatus, a gold electrode with a thickness of 20 nm was formed by patterning using a contact electrode metal mask, and UV-O ₃ treatment was performed for 30 minutes to prepare a substrate with electrodes.

The substrate with the electrodes is placed on a spin coater, about 10 ml of the organic semiconductor material solution is dropped, applied at 1,000 rpm for 5 seconds, the substrate is moved to a hot plate at 120° C., and dried for 5 minutes. , to form an organic semiconductor layer.
The substrate on which the organic semiconductor layer was formed was placed in a spin coater, and the resin composition of Example 3 was applied under the same conditions as in Example 1 to form an insulating layer. After air blowing, it was placed in a vapor deposition apparatus, and a patterned silver electrode with a film thickness of 100 nm was formed using a metal mask for gate electrodes.
The structure of the obtained organic semiconductor transistor is of a bottom-contact/top-gate type, where the gold electrode is the contact electrode (source electrode and drain electrode) and the silver electrode is the gate electrode. The contact electrode was a counter electrode and was patterned with a channel length of 100 μm and a channel width of 2000 μm, and the gate electrode was arranged so as to cover the channel region.

The capacitance (C) of the insulating film used for calculating the mobility was measured. The contact electrode metal mask and the gate electrode metal mask had a rectangular pattern of 1 mm×4 mm, and the gold electrode and the silver electrode were arranged with the organic semiconductor layer and the insulating layer sandwiched therebetween. Capacitance measurement (Cf measurement) using a semiconductor parameter analyzer (Keysight: B1500A) was 2.57 nF/cm ² .

The organic semiconductor transistor was measured using a semiconductor parameter analyzer (Keysight: B1500A). Using a three-terminal prober, a drain voltage (V _d ) and a gate voltage (V _g ) were applied with the source electrode as a reference. The current _Id flowing between the source and the drain was measured while _Vg was continuously changed while _Vd was kept constant. From the obtained I _d -V _g curve, carrier mobility and threshold voltage were calculated using various parameters (channel length, channel width, capacitance of insulating film). For the calculation, the drain current-gate voltage characteristic correlation in the linear region of Equation 1 and the drain current-gate voltage characteristic correlation in the saturation region of Equation 2, which are expressed by the following equations, were used.

Ｉ_ｄ：ドレイン電流、Ｗ：チャネル幅、Ｌ：チャネル長、μ：ホール移動度、
Ｃ：絶縁膜の静電容量、Ｖ_ｇ：ゲート電圧、Ｖ_ｔｈ：閾値電圧、Ｖ_ｄ：ドレイン電圧

Ｉ_ｄ:ドレイン電流、Ｗ:チャネル幅、Ｌ:チャネル長、μ:ホール移動度、
Ｃ:絶縁膜の静電容量、Ｖ_ｇ:ゲート電圧、Ｖ_ｔｈ:閾値電圧

I _d : drain current, W: channel width, L: channel length, μ: hole mobility,
C: capacitance of insulating film, V _g : gate voltage, V _th : threshold voltage, V _d : drain voltage

I _d : drain current, W: channel width, L: channel length, μ: hole mobility,
C: capacitance of insulating film, V _g : gate voltage, V _th : threshold voltage

The results are shown in Table 3, FIGS. 4(a)-4(c) and FIGS. 5(a)-5(c). As shown in these figures and tables, it was confirmed that the organic thin film transistor produced using the laminated structure of Example 3 exhibited the electrical characteristics of the transistor, and that the organic semiconductor layer and the insulating film each functioned.

INDUSTRIAL APPLICABILITY The present invention can be used as a resin composition for forming an insulating layer provided in contact with an organic semiconductor layer in an organic thin film laminated structure of an organic thin film transistor.

1: Organic thin film laminated structure 2, 3, 4, 5: Organic thin film transistor 11: Substrate 12: Organic semiconductor layer 13: Insulating layer (first insulating layer)
14: source electrode 15: drain electrode 16: gate electrode 17: insulating layer (second insulating layer)

Claims (13)

It contains the following (A) to (D) used to form an insulating layer on the organic semiconductor layer ,
(A) an insulating polymer (B) a first solvent that dissolves the insulating polymer (C) a second solvent that does not dissolve the organic semiconductor constituting the organic semiconductor layer (D) the first solvent and the second solvent A third solvent that is compatible with each of the two solvents
A resin composition in which the content of the first solvent is 50 parts by volume or less in a total of 100 parts by volume of the first to third solvents. the first solvent dissolves both the insulating polymer and the organic semiconductor;
wherein the second solvent dissolves neither the insulating polymer nor the organic semiconductor;
2. The resin composition according to claim 1, wherein said third solvent does not dissolve said organic semiconductor. the first solvent is a non-fluorinated solvent containing no fluorine atoms in the molecule,
Each of the second solvent and the third solvent is a fluorine-based solvent containing a fluorine atom in the molecule, and the second solvent and the third solvent each contain a fluorine atom in the molecule. different proportions,
The resin composition according to claim 1 or 2. In the insulating polymer, the ratio of the number of fluorine atoms to the total number of hydrogen atoms and halogen atoms contained in the repeating unit is 50% or less.
The resin composition according to any one of claims 1 to 3 . The insulating polymer is a (meth)acrylic resin
The resin composition according to any one of claims 1-4 . Furthermore, (E) containing a coupling agent
The resin composition according to any one of claims 1-5 . An organic thin film laminated structure comprising an organic semiconductor layer formed on a substrate and an insulating layer laminated in contact with the organic semiconductor layer,
An organic thin film laminate structure, wherein the insulating layer is formed using the resin composition according to any one of claims 1 to 6 . The organic semiconductor compound forming the organic semiconductor layer has a molecular weight of 2000 or less.
The organic thin film laminated structure according to claim 7 . An organic thin film transistor comprising the organic thin film laminated structure according to claim 7 , a source electrode, a drain electrode and a gate electrode. the source electrode and the drain electrode are formed on the substrate;
the organic semiconductor layer is laminated over the substrate, the source electrode and the drain electrode;
The gate electrode is formed on the insulating layer
The organic thin film transistor according to claim 9 . the source electrode and the drain electrode are formed on the organic semiconductor layer;
the insulating layer is laminated to cover the organic semiconductor layer, the source electrode and the drain electrode;
The gate electrode is formed on the insulating layer
The organic thin film transistor according to claim 9 . the gate electrode is formed on the substrate;
a second insulating layer formed on the substrate to cover the gate electrode;
the source electrode and the drain electrode are formed on the second insulating layer;
the organic semiconductor layer is laminated to cover the second insulating layer, the source electrode and the drain electrode;
A first insulating layer is laminated to the organic semiconductor layer
The organic thin film transistor according to claim 9 . the gate electrode is formed on the substrate;
a second insulating layer formed on the substrate to cover the gate electrode;
The organic semiconductor layer is laminated on the second insulating layer,
the source electrode and the drain electrode are formed on the organic semiconductor layer;
A first insulating layer is laminated on the organic semiconductor layer, the source electrode and the drain electrode
The organic thin film transistor according to claim 9 .

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