JP2019117884A - Laminate structure and manufacturing method thereof - Google Patents

Abstract

To provide a laminate structure improved in bias stress resistance, a manufacturing method thereof, and an organic transistor employing the same.SOLUTION: The present invention relates to a laminate structure of an organic semiconductor layer, a solvent soluble polymer layer and a solvent resistant lower layer and interface energy between the solvent soluble polymer layer and the solvent resistant lower layer is 3 mJ/mor less, thereby reducing roughness of an interface between the organic semiconductor layer and the solvent soluble polymer layer. When the interface energy between the solvent soluble polymer layer and the solvent resistant lower layer is 3 mJ/m2 or less, the solvent soluble polymer layer is wet-spread over the solvent resistant lower layer and surface roughness of the solvent soluble polymer layer is reduced, thereby smoothing the interface between the organic semiconductor layer and the solvent soluble polymer layer. The organic semiconductor layer is smooth, thereby forming an excellent organic semiconductor/gate insulation film interface of a reduced charge trap. Thus, an organic transistor configured by employing the laminate structure is improved in bias stress resistance.SELECTED DRAWING: None

Description

  The present invention relates to an organic semiconductor layer and an organic thin film transistor, and more particularly to an organic semiconductor layer containing a low molecular weight organic semiconductor material excellent in coatability applicable to a printing method, and an organic thin film transistor formed using the same. is there.

  BACKGROUND ART Organic semiconductor devices represented by organic thin film transistors are attracting attention in recent years because they have features not found in inorganic semiconductor devices, such as energy saving, low cost and flexibility. This organic semiconductor device is composed of several kinds of materials such as an organic semiconductor layer, a substrate, an insulating layer, an electrode, etc., and the electrical characteristics (carrier mobility, on current and on / off ratio, threshold voltage, current hysteresis, etc.) of the organic semiconductor device And reliability (heat resistance, bias stress resistance, etc.) depend on the properties of the material constituting the device, it is desirable to develop materials and manufacturing methods that provide high electrical properties and high reliability.

  Among them, the organic semiconductor layer responsible for charge carrier movement plays a central role in the device. As a method of producing the organic semiconductor layer, a general method such as a vacuum evaporation method which is carried out by evaporating the organic semiconductor material under high temperature vacuum, a coating method of dissolving the organic semiconductor material in a suitable solvent and coating the solution It is known to. Coating can be carried out using printing technology without using high temperature and high vacuum conditions, so it is considered to be an economically preferable process, and is a coating type organic semiconductor with high coatability and excellent carrier mobility. Layers are desired.

  Generally, in order to form a coating type organic semiconductor layer using printing technology, it is necessary to improve the film formability of the solution, and a method using a solution in which a polymer binder is added to an organic semiconductor material is known.

  For example, an organic thin film transistor formed using an organic semiconductor layer formed using a solution containing a polymer binder such as polystyrene and an organic semiconductor such as a polymer semiconductor has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses that a transistor having good performance characteristics can be produced by using a polymer binder. Preferred polymeric binders are low dielectric constant materials and are stated to preferably contain conjugated bonds, in particular double bonds and / or aromatic rings. It is also desirable that the dielectric constant of the material be less dependent on frequency, which is said to be a feature of non-polar materials. Furthermore, as a low dielectric constant (low polarity) polymer binder, it is described that a copolymer of styrene, α-methylstyrene and butadiene can be suitably used.

  Also, as another method using a solution obtained by adding a polymer binder such as polystyrene to an organic semiconductor material, a method of forming an organic semiconductor layer using a solution containing a specific polyacene compound and a polymer binder (organic binder resin) is proposed. (See, for example, Patent Document 2). According to Patent Document 2, by using the method, the organic semiconductor layer can be uniformly coated on a wide region on the substrate, and mobility and uniformity of the OFET (organic field effect transistor) are improved. Preferred polymeric binders are low dielectric constant materials, and high dielectric constant polymeric binders have been shown to result in reduced mobility, an undesirable increase in current hysteresis. Also, preferred polymer binders are described as copolymers of styrene, alpha methyl styrene and butadiene. However, the organic transistors obtained in Patent Document 1 and Patent Document 2 have a problem in device reliability such as bias stress resistance.

WO 2002-045184 WO 2005-055248

  The present invention has been made in view of the above problems, and an object thereof is to provide a laminated structure suitable for manufacturing an organic transistor excellent in bias stress resistance and a method for manufacturing the same.

  MEANS TO SOLVE THE PROBLEM As a result of earnest examination, in order to solve the said subject, the present inventors discover that the laminated structure of a specific structure can solve the said subject, and came to complete this invention.

That is, the present invention
A laminate structure of an organic semiconductor layer, a solvent-soluble polymer layer, and a solvent-resistant lower layer, wherein the interface energy between the solvent-soluble polymer layer and the solvent-resistant lower layer is 3 mJ / m ² or less It is about the body.

  The invention will be described in more detail below.

  The laminated structure of the present invention is present in the channel region of the organic transistor. Here, the channel region is a region between the source electrode and the drain electrode, and a region overlapping with the gate electrode in the vertical direction.

  The laminated structure of the present invention is characterized in that it is a laminated structure of an organic semiconductor layer, a solvent-soluble polymer layer, and a solvent resistant lower layer. Here, in the present invention, “solvent-soluble polymer” refers to a polymer in which 1% by weight or more dissolves in the solvent of the organic semiconductor to be used at the stage of forming the organic semiconductor layer, “solvent resistant lower layer” The term indicates a layer which does not dissolve in the solvent at the stage of forming the organic semiconductor layer. The “organic semiconductor layer”, “solvent-soluble polymer layer”, and “solvent-resistant lower layer” indicate that the layer has an organic semiconductor, a solvent-soluble polymer, and solvent resistance, respectively.

The laminated structure of the present invention is characterized in that the organic semiconductor layer and the solvent resistant lower layer have a laminated structure by being in contact with each other via the solvent-soluble polymer layer. In the laminated structure of the present invention, the interface energy between the solvent-soluble polymer layer and the solvent-resistant lower layer is 3 mJ / m ² or less, so that the interface between the organic semiconductor layer and the solvent-soluble polymer layer is It is characterized in that the roughness is small. Here, when the interfacial energy between the solvent-soluble polymer layer and the solvent-resistant lower layer is 3 mJ / m ² or less, the solvent-soluble polymer layer is wet and spread on the solvent-resistant lower layer, and the solvent-soluble polymer layer By reducing the surface roughness of the above, the interface between the organic semiconductor layer and the solvent-soluble polymer layer can be smoothed. Then, since the organic semiconductor layer is smooth, a good organic semiconductor / gate insulating film interface with few charge traps is formed, and the organic transistor using the laminated structure of the present invention has excellent bias stress resistance. It will be Interfacial energy between the solvent soluble polymer layer and the solvent resistance underlayer is preferably at 2 mJ / m ² or less, and more preferably 1 mJ / m ² or less.

The interface energy (γ _SL ) between the solvent-soluble polymer layer and the solvent-resistant lower layer can be determined from the following formula (1).

γ _SL = γ _S + γ _L −2 (γ _S ^d γ _L ^d ) ^1/2 −2 (γ _S ^p γ _L ^p ) ^1/2 (1)
(Wherein, γ _S is the surface energy of the solvent resistant lower layer, γ _L is the surface energy of the solvent soluble polymer, γ _S ^d is the dispersion term of the solvent resistant lower layer surface energy, and γ _S ^p is the solvent resistant lower layer Polar term of surface energy, γ _L ^d is dispersion term of surface energy of solvent-soluble polymer, and γ _L ^p shows polar term of surface energy of solvent-soluble polymer.)
Here, the solvent-resistant lower layer of the present invention is a lower layer of a laminated structure of an organic semiconductor layer and a solvent-soluble polymer layer, and indicates a surface on which the solvent-soluble polymer is formed. In the case of the organic transistor, depending on the device structure, the solvent resistant lower layer may be a gate insulating layer.

  The organic semiconductor used in the present invention is not particularly limited as long as it has semiconductor characteristics, and either a low molecular semiconductor or a high molecular semiconductor can be used.

  In the present invention, when the organic semiconductor is a low molecular semiconductor, for example, a compound represented by the following general formula (2) can be mentioned.

(Here, ring structures Ar ¹ and Ar ⁵ each independently represent a thiophene ring, a thiazole ring, or a benzene ring, and ring structures Ar ² and Ar ⁴ each independently represent a thiophene ring, a benzene ring, or cyclobutene And a ring structure Ar ³ represents a benzene ring, a thiophene ring, or a cyclobutene ring, R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or a carbon number 4-20 aryl group, alkenyl group having 2 to 20 carbon atoms, or alkynyl group having 2 to 20 carbon atoms, and R ⁵ and R ⁶ each independently represent a hydrogen atom, trialkylsilylethynyl group, carbon The alkyl group is an alkyl group of 1 to 20 or an alkoxy group having 1 to 20 carbon atoms, m is an integer of 1 or 2, n is an integer of 0 to 2, and o is an integer of 0 or 1. If the structure Ar ³ is thiophene ring or a cyclobutene ring, o is zero.)
The ring structures Ar ¹ and Ar ⁵ of the organic semiconductor each independently represent a thiophene ring, a thiazole ring or a benzene ring, and a thiophene ring and a thiazole ring are preferable because of high mobility.

The ring structures Ar ² and Ar ⁴ each independently represent a thiophene ring, a benzene ring, or a cyclobutene ring, and a thiophene ring is preferable because of high oxidation resistance.

The ring structure Ar ³ represents a benzene ring, a thiophene ring or a cyclobutene ring, and a benzene ring is preferable because of high heat resistance.

Each of R ³ and R ⁴ independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 4 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or 20 is an alkynyl group, preferably an alkyl group having 1 to 20 carbon atoms from the viewpoint of solubility.

The alkyl group having 1 to 20 carbon atoms in R ³ and R ⁴ is, for example, methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, n-pentyl group, n-hexyl group, isohexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-octadecyl group, 2-ethylhexyl group, 3-ethylheptyl group, 3-ethyldecyl, A linear or branched alkyl group such as 2-hexyldecyl group may be mentioned. And since it shows high mobility and high solubility especially among them, a C3-C12 alkyl group is preferable, and n-propyl, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl Groups, n-octyl groups, n-nonyl groups and n-decyl groups are more preferred.

The aryl group having 4 to 20 carbon atoms for R ³ and R ⁴ is, for example, phenyl group, p-tolyl group, p- (n-hexyl) phenyl group, p- (n-octyl) phenyl group, p- (2) Alkyl substituted phenyl group such as -ethylhexyl) phenyl group; 2-furyl group; 2-thienyl group; 5-fluoro-2-furyl group, 5-methyl-2-furyl group, 5-ethyl-2-furyl group, 5 -(N-propyl) -2-furyl group, 5- (n-butyl) -2-furyl group, 5- (n-pentyl) -2-furyl group, 5- (n-hexyl) -2-furyl group , 5- (n-octyl) -2-furyl group, 5- (2-ethylhexyl) -2-furyl group, 5-fluoro-2-thienyl group, 5-methyl-2-thienyl group, 5-ethyl-2 -Thienyl group, 5- (n-propyl) -2-thienyl group 5- (n-butyl) -2-thienyl group, 5- (n-pentyl) -2-thienyl group, 5- (n-hexyl) -2-thienyl group, 5- (n-octyl) -2-thienyl group And alkyl substituted chalcogenophene groups such as 5- (2-ethylhexyl) -2-thienyl group and the like.

The alkenyl group having 2 to 20 carbon atoms in R ³ and R ⁴ is, for example, ethenyl group, n-propenyl group, n-butenyl group, n-pentenyl group, n-hexenyl group, n-heptenyl group, n-octenyl group , N-nonel group, n-decenyl group, n-dodecenyl group and the like.

The alkynyl group having 2 to 20 carbon atoms as R ³ and R ⁴ is, for example, ethynyl group, n-propynyl group, n-butynyl group, n-pentynyl group, n-hexynyl group, n-heptynyl group, n-octynyl group , N-nonynyl group, n-decynyl group, n-dodecynyl group and the like.

R ⁵ and R ⁶ each independently represent a hydrogen atom, a trialkylsilylethynyl group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms, and is a hydrogen atom because of high mobility Is preferred.

Trialkylsilylethynyl group in R ⁵ and R ^6, for example, trimethylsilyl ethynyl group, triethylsilyl ethynyl, triisopropylsilylethynyl group, and the like.

The alkyl group having 1 to 20 carbon atoms for R ⁵ and R ⁶ is, for example, methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, n-pentyl group, n-hexyl group, isohexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-octadecyl group, 2-ethylhexyl group, 3-ethylheptyl group, 3-ethyldecyl, A linear or branched alkyl group such as 2-hexyldecyl group may be mentioned. Among them, an alkyl group having 1 to 8 carbon atoms is preferable because of its high mobility and high solubility, and a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, n -Hexyl group, n-heptyl group and n-octyl group are more preferable.

The alkoxy group having 1 to 20 carbon atoms for R ⁵ and R ⁶ is, for example, a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isobutoxy group, an n-pentyloxy group, an n-hexyloxy group, an isohexyloxy group, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-dodecyloxy, n-tetradecyloxy, 2-ethylhexyloxy, 3-ethylheptyloxy, 2-hexyl A linear or branched alkyl group such as a desiloxy group may be mentioned. And since it shows high mobility and high solubility especially, a C1-C8 alkoxy group is preferable, and a methoxy group, an ethoxy group, n-propoxy group, n-butoxy group, isobutoxy group, n-pentyloxy group is preferable. Further preferred are an n-hexyloxy group, an isohexyloxy group, an n-heptyloxy group and an n-octyloxy group.

  m is an integer of 1 or 2, but is preferably 1 because of high solubility.

  n is an integer of 0 to 2 and is preferably 1 because π stacking is strong.

o represents an integer of 0 or 1, and is preferably 0 because of high heat resistance. When the ring structure Ar ³ is a thiophene ring or a cyclobutene ring, o is 0.

  Since the organic semiconductor used in the present invention has a high melting point, a structure having a condensed ring number of 5 or more is preferable.

  The organic semiconductor used in the present invention is more preferably a compound represented by the following general formula (3) because of its high symmetry and high mobility.

(Here, X represents sulfur or CHCHCH and Y represents CH or nitrogen. R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, carbon R ^{4 to} C 20 aryl groups, C 2 to C 20 alkenyl groups, or C 2 to C 20 alkynyl groups are shown, and R ⁵ and R ⁶ each independently represent a hydrogen atom or C 1 to 20 carbon atoms And R represents an alkyl group, an alkoxy group having 1 to 20 carbon atoms, or a trialkylsilylethynyl group, m represents an integer of 1 or 2, and n represents an integer of 0 to 2, provided that when X is CH = CH, Y represents Y. Indicates CH.)
Furthermore, the organic semiconductor used in the present invention is particularly preferably a compound represented by the following general formula (4) because of its high solubility.

(Here, R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 4 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or C2-20 alkynyl group is shown.)
As a specific example of the organic semiconductor used in the present invention, one having the following structure can be mentioned.

  In the present invention, when the organic semiconductor is a polymer semiconductor, examples of the polymer semiconductor include polymer semiconductors containing any of the repeating units of the structures shown in the following (A) to (I).

(Here, substituents R ^{7 to} R ³⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and 1 represents an integer of 1 to 4).
R ⁷ to R ³⁰ are respectively independently a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms.

The alkyl group having 1 to 20 carbon atoms in R ^{7 to} R ³⁰ is, for example, methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, n-pentyl group, n-hexyl group, isohexyl group, n-Heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-octadecyl group, 2-ethylhexyl group, 3-ethylheptyl group, 3-ethyldecyl group And linear or branched alkyl groups such as 2-hexyldecyl group.

  l is an integer of 1 to 4;

  The molecular weight of the polymer semiconductor is preferably 2,000 to 1,000,000, and 10,000 to 1,000,000, since the polymer semiconductor and the polymer are easily separated and have high mobility. More preferably, 20,000 to 500,000 are particularly preferred. Here, the molecular weight of the polymer semiconductor refers to the weight average molecular weight (Mw) in terms of polystyrene.

  The polymer semiconductor used in the present invention is more preferably one having the structure of (A) because an organic transistor with high carrier mobility can be obtained.

  There is no restriction | limiting in particular about the thickness of an organic-semiconductor layer, For example, 1 nm-1,000 nm are mentioned, 5 nm-300 nm are preferable, and 10 nm-100 nm are more preferable from the ease of control of a film thickness.

The solvent-soluble polymer used in the present invention functions as a polymer binder and is not particularly limited as long as the interfacial energy with the solvent resistant lower layer when used as a solvent-soluble polymer layer is 3.0 mJ / m ² or less. For example, polystyrene, poly (α-methylstyrene), poly (4-methylstyrene), poly (1-vinylnaphthalene), poly (2-vinylnaphthalene), poly (styrene-block-butadiene-block-styrene), Poly (styrene-block-isoprene-block-styrene), poly (vinyltoluene), poly (styrene-co-2,4-dimethylstyrene), poly (chlorostyrene), poly (styrene-co-α-methylstyrene) , Poly (styrene-co-butadiene), poly (ethylene-co-norbornene), polycarba , Poly (triarylamine), poly (9,9-dioctylfluorene-co-dimethyltriarylamine), poly (N-vinylcarbazole), poly (methyl methacrylate), poly (ethyl methacrylate), n-propyl poly (methacrylate), Polyisopropyl methacrylate, n-butyl polymethacrylate, phenyl polymethacrylate, methyl polyacrylate, ethyl polyacrylate, n-propyl polyacrylate, polar cyclic polyolefins, polysulfones, acrylonitrile-styrene copolymer, methyl Methacrylate-styrene copolymers etc. can be mentioned. As the solvent-soluble polymer used in the present invention, it is possible to use one type of solvent-soluble polymer alone or as a mixture of two or more types of solvent-soluble polymers. Furthermore, it is also possible to mix and use solvent soluble polymers of different molecular weights.

  In the present invention, the glass transition temperature (Tg) of the solvent-soluble polymer is preferred because it is more suitable to cope with the process temperature at the time of manufacturing an electronic device using an organic semiconductor (the performance of the organic transistor is not reduced by the process heating at the time of manufacturing). Is preferably 105 ° C. or higher, and examples of the solvent-soluble polymer include poly (α-methylstyrene), poly (bisphenol A carbonate (PC), polyphenylene oxide (PPO) and polar cyclic polyolefins. But can not be limited to these.

  As the solvent-soluble polymer used in the present invention, one having its surface energy adjusted by a surface treatment agent can be used. As a surface treatment agent, a silane coupling agent can be used, and as a specific example thereof, for example, 1,1,1,3,3,3-hexamethyldisilazane, phenyltrimethoxysilane, octyltrichlorosilane, (beta) -phenethyl trichlorosilane, (beta) phenethyl trimethoxysilane etc. can be mentioned.

  The roughness Ra of the interface between the organic semiconductor and the solvent resistant lower layer is preferably 10 nm or less, and more preferably 7 nm or less, in order to enhance bias stress resistance.

  The average thickness of the solvent-soluble polymer layer does not inhibit the contact between the organic semiconductor and the source electrode, the drain electrode, or the gate insulating film when the laminated structure of the present invention is used for the organic transistor. And 30 nm or less, and more preferably 25 nm or less. Here, the roughness Ra of the interface between the organic semiconductor and the solvent-soluble polymer, and the average film thickness of the solvent-soluble polymer can be determined using a hybrid laser microscope of Lasertec Corporation.

  Examples of the material used for the solvent resistant lower layer of the present invention include a crosslinked polymer, a self-assembled monolayer, an inorganic film and the like, and a solvent resistant to a solvent when forming a solvent soluble polymer. There is no particular limitation as long as there is a sex. When the solvent resistant lower layer is also used as a gate insulating film (in the case of an organic transistor in which the gate insulating film is on the lower side of the organic semiconductor layer), solvent resistance to the solvent among the examples of the gate insulating film described later Some of them are also suitably used.

  The two layers of the organic semiconductor layer and the solvent-soluble polymer layer of the present invention may be prepared using a mixed solution of an organic semiconductor and a solvent-soluble polymer (layer separation when forming a layer using this solution) (2 layers), and may be formed stepwise from each solution.

  Any solvent can be used as the solvent for the solution for forming an organic semiconductor layer in which the organic semiconductor of the present invention is dissolved, as long as it can dissolve the organic semiconductor and / or the solvent-soluble polymer according to the present invention. May be

  The organic solvent which can be used in the present invention is not particularly limited. For example, tetralin, indane, mesitylene, o-xylene, m-xylene, isopropylbenzene, pentylbenzene, cyclohexylbenzene, 1,2,4-trimethylbenzene , Toluene, anisole, 2-methyl anisole, 3-methyl anisole, 2,3-dimethyl anisole, 3,4- dimethyl anisole, 2,6-dimethyl anisole, benzothiazole, ethyl phenyl ether, butyl phenyl ether, 1,2 -Aromatic compounds such as methylenedioxybenzene, 1,2-ethylenedioxybenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene; cyclohexanone, isophorone, methyl ethyl ketone Ketones; saturated aliphatic compounds such as octane, nonane, decane, dodecane and decalin; esters such as phenyl acetate and cyclohexyl acetate; dipropylene glycol dimethyl ether, dipropylene glycol diacetate, dipropylene glycol methyl-n-propyl ether , Dipropylene glycol methyl ether acetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, ethylene glycol monomethyl ether acetate, Propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoether And glycols such as diethylene glycol monobutyl ether acetate; triacetylene etc., among which aromatic compounds are preferred because of their high solubility, and tetralin, mesitylene, o Xylene, m-xylene, 1,2,4-trimethylbenzene, anisole, 2-methylanisole, 3-methylanisole, 2,3-dimethylanisole, 3,4-dimethylanisole, 2,6-dimethylanisole, benzothiazole More preferred are 1,2-methylenedioxybenzene, 1,2-ethylenedioxybenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,4-dichlorobenzene.

  As the organic solvent used in the present invention, it is possible to use one kind of organic solvent alone or to use two or more kinds of organic solvents having different properties such as boiling point, polarity, solubility parameter and the like.

  The solution for forming an organic semiconductor layer of the present invention can be prepared by mixing and dissolving the organic semiconductor and / or the polymer of the present invention with an organic solvent.

  The concentration of the organic semiconductor in the solution for forming an organic semiconductor layer of the present invention is not particularly limited, but when it is in the range of 0.001 to 50.0% by weight, handling becomes easier, and when forming an organic semiconductor layer The efficiency of the In addition, when the viscosity of the solution for forming an organic semiconductor layer is in the range of 0.3 to 100 mPa · s, more suitable coatability is exhibited.

  When prepared using a mixed solution of an organic semiconductor and a solvent-soluble polymer, the mixing composition ratio of the organic semiconductor and the solvent-soluble polymer is not particularly limited, but it is more preferable to form the laminated structure of the present invention For this reason, the weight of the polymer is preferably in the range of 0.0001 to 100% by weight, more preferably in the range of 0.0001 to 50% by weight, based on the weight of the organic semiconductor, and 0.0001 to 30%. The range by weight is particularly preferred.

  There is no restriction | limiting in particular as a coating method at the time of forming a layer using the mixed solution of an organic semiconductor and a solvent-soluble polymer, For example, Simple coating methods, such as spin coat, drop cast, dip coat, cast coat; Dispenser Printing methods such as inkjet, slit coat, blade coat, flexographic printing, screen printing, gravure printing, offset printing, etc., and among them, spin coating, dispenser, and the like because they can be easily and efficiently produced. More preferably, it is an inkjet. Further, the temperature at that time is not particularly limited, and the coating can be performed in a state where the substrate or the solution is heated. When heating, in order to apply uniformly, it is preferable to apply below the glass transition temperature of a polymer, and it is more preferable to apply at 70 degrees C or less.

  When the organic solvent is dried and removed from the applied organic semiconductor layer and the polymer layer, the drying conditions are not particularly limited. For example, the organic solvent can be dried and removed under normal pressure or reduced pressure. There is no particular limitation on the temperature for drying and removal, but in order to prevent the polymer from flowing, it is preferable to carry out at a temperature below the glass transition temperature of the polymer.

  The organic semiconductor layer formed from the solution for forming an organic semiconductor layer of the present invention can be used as an organic semiconductor layer of an organic semiconductor device, particularly an organic transistor.

  An organic transistor can be obtained by laminating an organic semiconductor layer provided with a source electrode and a drain electrode on a substrate and a gate electrode via an insulating layer, and the organic semiconductor layer of the present invention is formed on the organic semiconductor layer. By using an organic semiconductor layer formed of a solution, an organic transistor can be provided which exhibits excellent semiconductor and electrical characteristics.

  The structure by the cross-sectional shape of a general organic transistor is shown in FIG. Here, (A) is a bottom gate-top contact type, (B) is a bottom gate-bottom contact type, (C) is a top gate-top contact type, and (D) is a top gate-bottom contact type 1 is an organic semiconductor layer, 2 is a substrate, 3 is a gate electrode, 4 is a gate insulating layer, 5 is a source electrode, 6 is a drain electrode, and the laminated structure of the present invention is any of organic compounds. It is possible to apply also to a transistor.

  Specific examples of the substrate include, for example, polyethylene terephthalate, polyethylene naphthalate, polymethyl methacrylate, polymethyl acrylate, polyethylene, polypropylene, polystyrene, cyclic polyolefin, halogenated cyclic polyolefin, polyimide, polycarbonate, polyvinyl phenol, polyvinyl alcohol, poly (poly (poly) Diisopropyl fumarate), poly (diethyl fumarate), poly (diisopropyl maleate), polyether sulfone, polyphenylene sulfide, plastic substrate such as cellulose triacetate; glass, quartz, aluminum oxide, silicon, highly doped silicon, silicon oxide, dioxide Inorganic material substrates such as tantalum, tantalum pentoxide, indium tin oxide; gold, copper, chromium, titanium, aluminum It can include a metal substrate such as um. Note that when highly doped silicon is used for the substrate, the substrate can also serve as the gate electrode.

  There is no restriction | limiting in particular as a gate electrode which concerns on this invention, For example, aluminum, gold | metal | money, silver, copper, highly doped silicon, tin oxide, indium oxide, indium tin oxide, chromium, titanium, tantalum, graphene, a carbon nanotube etc. And inorganic materials; organic materials such as doped conductive polymers (eg, PEDOT-PSS).

  In addition, the above-mentioned inorganic material can be used without any problem as a metal nanoparticle ink. In this case, the solvent is a polar solvent such as water, methanol, ethanol, 2-propanol, 1-butanol, 2-butanol, etc. because of appropriate dispersibility; carbon number such as hexane, heptane, octane, decane, dodecane, tetradecane etc. 6 to 14 aliphatic hydrocarbon solvents; toluene, xylene, mesitylene, ethylbenzene, pentylbenzene, hexylbenzene, octylbenzene, cyclohexylbenzene, tetralin, indane, anisole, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, It is preferable that they are C7-C14 aromatic hydrocarbon solvents, such as a 1, 2- dimethyl anisole, a 2, 3- dimethyl anisole, a 3, 4- dimethyl anisole. After the application of the nanoparticle ink, annealing is preferably performed in a temperature range of 80 ° C. to 200 ° C. in order to improve the conductivity.

  The gate insulating layer according to the present invention is not particularly limited. For example, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, tantalum oxide, tantalum pentoxide, indium tin oxide, tin oxide, vanadium oxide, titanium Inorganic materials such as barium titanate and bismuth titanate; polymethyl methacrylate, polymethyl acrylate, polyimide, polycarbonate, polyvinyl phenol, polyvinyl alcohol, poly (diisopropyl fumarate), poly (diethyl fumarate), polyethylene terephthalate, polyethylene naphthalate, Ethyl polycinnamate, methyl polycinnamate, ethyl polycrotonate, polyether sulfone, polypropylene-co-1-butene, polyisobutylene, polypropylene, polycyclopentane Polycyclohexane, polycyclohexane-ethylene copolymer, polyhalogenated cyclopentane, polyhalogenated cyclohexane, polyhalogenated cyclohexane-ethylene copolymer, halogenated cyclic polyolefin, BCB resin (trade name: Cycloten, Dow Chemical Co., Ltd.) Polymer insulating materials such as Parylene.TM., Such as Cytop.TM., Teflon.TM., Parylene C, and the like.

  In addition, the surfaces of these gate insulating layers are, for example, octadecyltrichlorosilane, decyltrichlorosilane, decyltrimethoxysilane, octyltrichlorosilane, octadecyltrimethoxysilane, β-phenethyltrichlorosilane, β-phenethyltrimethoxysilane, phenyltrichloride, and the like. Even silanes such as chlorosilane, phenyltrimethoxysilane and phenyltriethoxysilane; and silylamines such as hexamethyldisilazane can be used.

  The material of the source electrode and the drain electrode may be the same as that of the gate electrode, and may be the same as or different from the material of the gate electrode, and different materials may be stacked. Moreover, in order to raise the injection | pouring efficiency of a carrier, surface treatment can also be implemented to these electrode materials. Examples of surface treatment agents used for surface treatment include benzenethiol, pentafluorobenzenethiol, 4-fluorobenzenethiol, 4-methoxybenzenethiol and the like.

The organic transistor obtained by using the solution for forming an organic semiconductor layer of the present invention preferably has a carrier mobility of 0.5 cm ² / V · s or more because of its fast operability.

  In the organic transistor obtained by using the solution for forming an organic semiconductor layer of the present invention, the threshold voltage shift ΔVth is preferably 3 V or less, more preferably 1 V or less, because of high resistance to bias stress.

  The solution for forming an organic semiconductor layer of the present invention and the organic semiconductor layer formed therefrom are organic thin film transistor applications such as electronic paper, organic EL display, liquid crystal display, IC tag (RFID tag), memory, sensor, etc .; organic EL display Materials: Organic semiconductor laser materials; Organic thin film solar cell materials; It can be used for electronic materials such as photonic crystal materials, and since organic semiconductors become crystalline thin films, they can be used as semiconductor layer applications of organic transistors preferable.

  By using the stacked structure of the present invention, it is possible to provide an organic transistor having high bias stress resistance.

  EXAMPLES The present invention will be described in more detail by the following examples, but the present invention is not limited by these examples.

In the examples, for the roughness Ra of the interface between the organic semiconductor and the solvent-soluble polymer and the thickness of the solvent-soluble polymer layer, the channel region (100 μm ² ) was measured using a hybrid laser microscope (manufactured by Lasertec Corporation). , Analyzed. Regarding electrical properties, using a semiconductor parameter analyzer (4200 SCS manufactured by Keithley), the drain voltage (Vd = −20 V) and gate voltage (Vg) are scanned in 1 V steps from +5 to −20 V, and transfer characteristics (Id-Vg) The evaluation of

Synthesis example 1
(Synthesis of material used for solvent resistant lower layer (crosslinked polymer 1))
10.0 g of polystyrene-b-poly (ethylene butylene) -b-polystyrene (hereinafter referred to as SEBS) having a weight average molecular weight of 280,000 in a 500 mL Schlenk tube in a nitrogen box, 300 mL of dehydrated methylene chloride, cinnamic acid chloride 3 .4g was charged and dissolved at room temperature under stirring. The Schlenk tube was cooled with ice water, and 4.6 g of trifluoromethanesulfonic acid (hereinafter referred to as "TFMS") was added dropwise over 10 minutes with a syringe. The color of the polymer solution was colored in reddish purple along with the dropping. After completion of the addition, the ice water bath was removed and the reaction was allowed to proceed at room temperature for 40 hours. The reaction solution was again cooled with ice water, and then a saturated aqueous solution in which 5.6 g of saturated sodium bicarbonate was dissolved was added to neutralize TFMS and hydrochloric acid in the system. The reaction was transferred to a separatory funnel and the methylene chloride layer was separated. The aqueous layer was further washed three times with methylene chloride and separated to obtain a methylene chloride solution of the polymer. This solution is filtered through a 3 μm Teflon filter, reprecipitated with 1.5 L of methanol, and the polymer is isolated by filtration twice, and then dried under reduced pressure at 50 ° C. and 8.8 g The crosslinked polymer 1 of

As a result of analysis by ¹ H-NMR, it was confirmed that the content of chalcone group of the obtained crosslinked polymer 1 was 7.7 mol%.

  The SEBS used was synthesized according to the production method described in Japanese Patent No. 2777239, and it was confirmed that the content of styrene units was 28 mol%.

Example 1
(Preparation of mixed solution of organic semiconductor and solvent soluble polymer)
In a 10 ml sample tube under air, 1.5 g of m-xylene, 12 mg (0.8 wt%) of 2,7-di (n-hexyl) dithienobenzodithiophene (compound 1), and PMMA (manufactured by Aldrich, Mw 350, An organic semiconductor / solvent-soluble polymer mixed solution was prepared by adding 0000.75 mg (0.05 wt%) and heating at 50 ° C. for dissolution.
(Preparation of laminated structure)
Crosslinked PVP was formed as a solvent resistant lower layer on a glass substrate (interface energy with PMMA 0.22 mJ / m ² ). Ag was vacuum deposited on the entire surface to a thickness of 50 nm, a source / drain electrode of L / W = 10/10 μm was formed by photolithography, and electrode modification was performed with pentafluorobenzenethiol. The mixed solution of the organic semiconductor and solvent-soluble polymer prepared by the above-mentioned method was dispenser printed at room temperature on the source / drain electrode under air and heated at 90 ° C. for 10 minutes to produce a laminated structure.
(Fabrication of organic transistor)
Parylene was vacuum-deposited as a gate insulating film to a thickness of 600 nm on the laminated structure manufactured by the above method. A shadow mask was placed on the channel, and 50 nm of Ag was vapor-deposited as a gate electrode, to fabricate a top gate-bottom contact type organic transistor.
(Measurement of electrical properties before bias stress test)
From the transfer characteristics of the organic thin film transistor manufactured by the above method, the carrier mobility of holes was 2.35 cm ² / V · s (p type), and the threshold voltage was 0.45 V.

From the measurement results of the electrical properties before the bias stress test, it was found that the obtained organic thin film transistor exhibited good electrical properties.
(Measurement of electrical properties after bias stress test)
After applying a gate voltage of +30 V to the organic thin film transistor manufactured by the above method for one hour in the atmosphere (bias stress test), the transfer characteristics were measured. As a result, the carrier mobility was 2.35 cm ² / V · s (p-type), and the threshold voltage was 0.60 V (ΔVth = + 0.15 V) from the transfer characteristics.

From the measurement results of the electrical properties after the bias stress test, it was found that the obtained organic thin film transistor is excellent in bias stress resistance.
(Analysis of laminated structure)
After measuring the electrical properties, the gate electrode and the gate insulating film were peeled off with a tape. Furthermore, the organic semiconductor was ultrasonically removed in a poor solvent, and the exposed polymer layer was analyzed. The interface roughness Ra between the organic semiconductor layer and the solvent-soluble polymer, that is, the Ra of the PMMA surface was 6 nm, and the average film thickness of PMMA was 11 nm.

Example 2
(Preparation of mixed solution of organic semiconductor and solvent soluble polymer)
Preparation of mixed solution of organic semiconductor and solvent-soluble polymer in the same manner as in Example 1 except that 1.5 mg (0.1 wt%) of polar cyclic polyolefin 1 (Mw = 44,000 by GPC) was used instead of PMMA Did.

  The structure of polar cyclic polyolefin 1 is shown below.

(Preparation of laminated structure)
The crosslinked polymer 1 was formed into a film as a solvent-resistant lower layer on a glass substrate (interface energy with polar cyclic polyolefin 1 0.12 mJ / m ² ). After drying at 50 ° C. for 1 minute, it was crosslinked by irradiation with ultraviolet light of 250 mJ / cm ² . Ag was vacuum deposited on the entire surface to a thickness of 50 nm, a source / drain electrode of L / W = 10/10 μm was formed by photolithography, and electrode modification was performed with pentafluorobenzenethiol. An organic semiconductor / solvent-soluble polymer mixed solution prepared by the above method was spin-coated at room temperature on the source / drain electrode under air, and heated at 90 ° C. for 20 minutes to produce a laminated structure.
(Fabrication of organic thin film transistor)
Cytop (made by Asahi Kasei Co., Ltd.) was spin-coated as a gate insulating film to the laminated structure produced by the above-mentioned method. Ag was vacuum-deposited on the entire surface to a thickness of 50 nm, and a gate electrode was formed on the channel by photolithography to fabricate a top gate-bottom contact type organic thin film transistor.
(Measurement of electrical properties before bias stress test)
From the transfer characteristics of the organic thin film transistor manufactured by the method described above, the carrier mobility of holes was 1.82 cm ² / V · s (p type), and the threshold voltage was −0.41 V.

From the measurement results of the electrical properties before the bias stress test, it was found that the obtained organic thin film transistor exhibited good electrical properties.
(Measurement of electrical properties after bias stress test)
After applying a gate voltage of +30 V to the organic thin film transistor manufactured by the above method for one hour in the atmosphere (bias stress test), the transfer characteristics were measured. As a result, the carrier mobility was 1.87 cm ² / V · s (p type) and the threshold voltage was −0.39 V (ΔVth = + 0.02 V) from the transfer characteristics.

From the measurement results of the electrical properties after the bias stress test, it was found that the obtained organic thin film transistor is excellent in bias stress resistance.
(Analysis of laminated structure)
The analysis was conducted in the same manner as in Example 1. As a result, the interface roughness Ra between the organic semiconductor layer and the solvent-soluble polymer layer, that is, the Ra of the polar cyclic polyolefin 1 surface is 1 nm, and the average film thickness of the polar cyclic polyolefin 1 is It was 24 nm.

Comparative Example 1
(Preparation of mixed solution of organic semiconductor and solvent soluble polymer)
An organic semiconductor / solvent-soluble polymer mixed solution was prepared in the same manner as in Example 1 except that PSt (manufactured by Aldrich, Mw 280,000) (interface energy of 4.2 mJ / m ² with crosslinked PVP) was used instead of PMMA. Preparation was done.
(Preparation of laminated structure)
A laminated structure was produced in the same manner as in Example 1.
(Measurement of electrical properties before bias stress test)
From the transfer characteristics of the organic transistor manufactured by the above method, the carrier mobility of holes was 2.55 cm ² / V · s (p-type), and the threshold voltage was 0.56 V.

From the measurement results of the electrical properties before the bias stress test, it was found that the obtained organic thin film transistor exhibited good electrical properties.
(Measurement of electrical properties after bias stress test)
After applying a gate voltage of +30 V to the organic thin film transistor manufactured by the above method for one hour in the atmosphere (bias stress test), the transfer characteristics were measured. As a result, the carrier mobility was 2.46 cm ² / V · s (p type) and the threshold voltage was 1.69 V (ΔVth = + 1.13 V) from the transfer characteristics.

From the measurement results of the electrical properties after the bias stress test, it was found that the obtained organic thin film transistor is inferior in bias stress resistance.
(Analysis of laminated structure)
The analysis was conducted in the same manner as in Example 1. As a result, the interface roughness Ra between the organic semiconductor layer and the solvent-soluble polymer layer, that is, Ra on the PSt surface was 12 nm, and the average film thickness of PSt was 31 nm.

  By using the laminated structure of the present invention, an organic thin film transistor having excellent semiconductor and electrical properties can be manufactured, so that application as a semiconductor device material can be expected.

FIG. 5 is a view showing a structure based on the cross-sectional shape of the organic thin film transistor.

(A): bottom gate-top contact type organic thin film transistor (B): bottom gate-bottom contact type organic thin film transistor (C): top gate-top contact type organic thin film transistor (D): top gate-bottom contact type organic thin film transistor 1: Organic semiconductor layer 2: substrate 3: gate electrode 4: gate insulating layer 5: source electrode 6: drain electrode

Claims (5)

A laminated structure of an organic semiconductor layer, a solvent-soluble polymer layer, and a solvent-resistant lower layer, and the interface energy between the solvent-soluble polymer layer and the solvent-resistant lower layer is 3 mJ / m ² or less Feature of laminated structure. The laminated structure according to claim 1, wherein the average film thickness of the solvent-soluble polymer is 30 nm or less. The laminate structure according to claim 1 or 2, wherein the roughness Ra of the interface between the organic semiconductor layer and the solvent-soluble polymer layer is 10 nm or less. A method for producing a laminate structure, comprising heating the laminate at a temperature not higher than the glass transition temperature of a polymer used for the solvent-soluble polymer layer. An organic transistor comprising the laminated structure according to any one of claims 1 to 3 in a channel region of the transistor.

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