JP5964703B2 - Organic semiconductor material and organic transistor - Google Patents

Description

The present invention relates to an organic semiconductor material having a benzothienobenzothiophene skeleton and an organic transistor using the same.

Conventionally, a thin film transistor (TFT) using amorphous silicon or polycrystalline silicon has been widely used as a switching element for liquid crystal display devices, organic EL display devices and the like. However, since the CVD apparatus used for manufacturing these TFTs using silicon is expensive, manufacturing a large TFT element causes an increase in manufacturing cost. In addition, since the silicon material is formed at a high temperature, it cannot be applied to plastic substrates, which are candidates for flexible display substrates, due to heat resistance problems. In order to solve this problem, an organic TFT using an organic semiconductor as a channel semiconductor layer instead of a silicon semiconductor has been proposed.

  Since an organic semiconductor can be formed into a solution at a low temperature to form a printed film, it does not require a large-scale manufacturing facility and can be applied to plastics with poor heat resistance, and is expected to lead flexible displays. On the other hand, organic semiconductors have lower carrier mobility than silicon semiconductors, and as a result, the response speed of TFTs has been a problem for practical use. Recently, organic semiconductors with the same mobility as amorphous silicon have been developed. It has been.

For example, Patent Document 1 discloses 2,7-substituted [1] benzothieno [3,2-b] [1] benzothiophene skeleton (hereinafter referred to as [1] benzothieno [3,2-b] [1] benzothiophene. compounds having abbreviated as BTBT) are described, as a substituent, _halogen, C 1 _{-C 18} alkyl, _C 1 _{-C 18} alkyl having _halogen, C 1 _{-C 18 alkyloxy,} C 1 -C ₁₈ alkylthio, or aryl, or is aryl having _halogen, C 1 _{-C 18} alkyl, _C 1 _{-C 18} alkyl having _halogen, C 1 _{-C 18 alkyloxy,} at least one C 1 _{-C 18} alkylthio Things are listed. That the mobility of these compounds ^(cm 2 / Vs) is 0.17~0.31cm ² / Vs.

Patent Document 2 describes a compound having a 2,7-substituted BTBT skeleton, and the substituent is a hydrogen atom or a halogeno-substituted C ₁ -C ₃₆ fatty hydrocarbon group. ing. The mobility of these compounds ^(cm 2 / Vs) has been described to be 0.12~4.5cm ² / Vs.

Patent Document 3 describes a compound having a BTBT skeleton having a halogen atom, an alkyl group, an alkenyl group, a carboxyl group, or a thiol group as a substituent as a substituent. It is said that an organic semiconductor film can be easily formed even by printing film formation by removing or reacting a substituent after film formation using the compound as a precursor.
Further, Patent Document 4 describes a polymer composition containing a compound having a BTBT skeleton having an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an alkoxy group, and the like. It has been reported that by containing a BTBT derivative having a conjugated length extended by an alkenyl group, an alkynyl group, or an aryl group, a semiconductor film stable in air is formed.

  On the other hand, as described above, many organic semiconductor materials with improved mobility have been reported, but when an organic semiconductor thin film is formed by printed film formation, carriers flow because organic semiconductor molecules are randomly arranged during printing. A channel is not formed, and it is difficult to obtain an organic semiconductor film with high mobility. Therefore, in this application, there is a need for an organic semiconductor material that provides a film in which organic semiconductor molecules are easily oriented in one direction during printed film formation and carriers can easily flow.

WO2006-077788 WO2008-47896 JP 2009-275032 A JP 2012-134483 A

However, many conventional materials still have a mobility of less than 1 cm ² / Vs, which is insufficient for driving a liquid crystal display device or an organic EL. Moreover, although the compound of patent document 2 with which high mobility is reported can be spin-coated, in order to express high mobility, it must be heat-processed by the variation in processing temperature and processing time. Even in a TFT manufactured under the same conditions, the variation in mobility is large. That is, in order to suppress variation in mobility, it is necessary to easily form a film in which organic semiconductor molecules are arranged.

In addition, BTBT derivatives having an alkenyl group or the like in Patent Document 3 and Patent Document 4 are introduced as a reactive group or to extend the conjugated length of the BTBT skeleton, and for the purpose of improving molecular orientation. Therefore, variation in mobility cannot be suppressed.
Therefore, in addition to improving the carrier mobility of molecules themselves, organic semiconductor materials are required to easily form a film with high mobility without deterioration in performance even when printed.
Accordingly, an object of the present invention is to provide an organic semiconductor material that provides a film with high carrier mobility and less mobility variation without going through a complicated process.

  In the present invention, as a result of intensive studies, a BTBT derivative into which an aryl group and an alkenyl group are introduced exhibits a liquid crystal phase in a wide temperature range, and crystallizes via a higher-order liquid crystal phase having a high order of molecular arrangement. Therefore, it has been found that a complicated heat treatment is not required even in a printed film formation, and a film with little mobility variation and high mobility is easily formed, and the present invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, the organic semiconductor excellent in the high mobility and the performance stability in TFT can be provided.

That is, the present invention includes the following items.
1. General formula (1)

（式中、Ｒ_１が置換基を有してもよい炭素数３〜２０のアルケニル基であり、Ｒ_２が芳香族炭化水素基又は複素芳香族基、炭素数２〜２０のアルキル基または炭素数２〜２０のアルケニル基を置換基として持つ芳香族炭化水素基又は複素芳香族基、ハロゲン原子を有する炭素数２〜２０のアルキル基を置換基として持つ芳香族炭化水素基又は複素芳香族基、炭素数３〜２０のアルコキシアルキル基を置換基として持つ芳香族炭化水素基又は複素芳香族基、炭素数３〜２０のアルキルスルファニルアルキル基を置換基として持つ芳香族炭化水素基又は複素芳香族基、炭素数３〜２０のアルキルアミノアルキル基を置換基として持つ芳香族炭化水素基又は複素芳香族基から選ばれる基）
で表される有機半導体材料、
２．１に記載の有機半導体材料を用いてなる有機半導体デバイス、
３．１に記載の有機半導体材料を有機半導体層として用いる有機トランジスタ。

(In the formula, R ₁ is an optionally substituted alkenyl group having 3 to 20 carbon atoms, and R ₂ is an aromatic hydrocarbon group or heteroaromatic group, an alkyl group having 2 to 20 carbon atoms, or carbon. An aromatic hydrocarbon group or heteroaromatic group having an alkenyl group of 2 to 20 as a substituent, an aromatic hydrocarbon group or heteroaromatic group having an alkyl group of 2 to 20 carbon atoms having a halogen atom as a substituent , An aromatic hydrocarbon group or heteroaromatic group having an alkoxyalkyl group having 3 to 20 carbon atoms as a substituent, an aromatic hydrocarbon group or heteroaromatic group having an alkylsulfanylalkyl group having 3 to 20 carbon atoms as a substituent A group selected from an aromatic hydrocarbon group or a heteroaromatic group having an alkylaminoalkyl group having 3 to 20 carbon atoms as a substituent)
An organic semiconductor material represented by
An organic semiconductor device using the organic semiconductor material according to 2.1,
An organic transistor using the organic semiconductor material described in 3.1 as an organic semiconductor layer.

(Compound represented by the general formula (1))
The compound represented by the general formula (1) is a compound having a substituent in the BTBT skeleton, and one substituent is an alkenyl group having 3 to 20 carbon atoms which may have a substituent, and the other The aromatic hydrocarbon group or heteroaromatic group, the aromatic hydrocarbon group or heteroaromatic group having a C2-20 alkyl group or the C2-20 alkenyl group as a substituent. Aromatic hydrocarbon group or heteroaromatic group having an alkyl group having 2 to 20 carbon atoms as a substituent, an aromatic hydrocarbon group or heteroaromatic group having an alkoxyalkyl group having 3 to 20 carbon atoms as a substituent Group, aromatic hydrocarbon group or heteroaromatic group having an alkylsulfanylalkyl group having 3 to 20 carbon atoms as a substituent, aromatic hydrocarbon having a substituent having an alkylaminoalkyl group having 3 to 20 carbon atoms Characterized in that a group or a heteroaromatic group.

(List of substituents of BTBT)
R ₁ in the general formula (1) compounds represented by the present invention is an alkenyl group having 3 to 20 carbon atoms which may have a substituent. When a double bond is directly connected to the BTBT skeleton such as a vinyl group, the conjugated length is excessively widened, and the target higher-order liquid crystal phase is hardly expressed. Therefore, the alkenyl group of the present invention has a double bond directly to the BTBT skeleton. What is not connected is preferable.
Such alkenyl group is not particularly limited, and examples thereof include allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, decenyl group, dodecenyl group, tetradecenyl group, hexadecenyl group, octadecenyl group, eicosenyl group. Group, octadeca-9,12-dienyl group, octadeca-9,12,15-trienyl group, eicosa-11,14-dienyl group, eicosa-11,14,17-trienyl group, eicosa-5,8,11, 14-tetraenyl group, methyl pentenyl group, cyclohexene, linear, such as 4-methyl-cyclohexene, an alkenyl group of branches and the like. These alkenyl groups can be used regardless of cis isomer, trans isomer, or a mixture thereof.

In addition, R ₂ of the compound represented by the general formula (1) of the present invention is substituted with an aromatic hydrocarbon group or a heteroaromatic group, an alkyl group having 2 to 20 carbon atoms, or an alkenyl group having 2 to 20 carbon atoms. An aromatic hydrocarbon group or heteroaromatic group as a group, an aromatic hydrocarbon group or heteroaromatic group having a halogen atom-containing alkyl group having 2 to 20 carbon atoms as a substituent, and an alkoxyalkyl having 3 to 20 carbon atoms An aromatic hydrocarbon group or heteroaromatic group having a substituent as a group, an aromatic hydrocarbon group or heteroaromatic group having a alkyl group having 3 to 20 carbon atoms as a substituent, an alkyl having 3 to 20 carbon atoms The aromatic hydrocarbon group or heteroaromatic group having an aminoalkyl group as a substituent is not particularly limited, and examples thereof include the following.
Examples of the aromatic hydrocarbon group which may have a substituent include phenyl, naphthyl, azulenyl, acenaphthenyl, anthranyl, phenanthryl, naphthacenyl, fluorenyl, pyrenyl, chrysenyl, perylenyl, biphenyl An unsubstituted monocyclic or polycyclic aromatic hydrocarbon group having 6 to 24 carbon atoms such as a p-terphenyl group and a quarterphenyl group,

o-tolyl group, m-tolyl group, p-tolyl group, 2,4-xylyl group, 2,6-xylyl group, mesityl group, duryl group, 4-ethylphenyl group, 4-n-propylphenyl group, 4 -Isopropylphenyl group, 4-n-butylphenyl group, 4-n-pentylphenyl group, 4-n-hexylphenyl group, 4-n-decaphenyl group, 4-stearylphenyl group, 9,9'-dihexylfur An alkyl-substituted aromatic hydrocarbon group in which the aromatic hydrocarbon group is substituted with an alkyl group having 1 to 18 carbon atoms, such as an oleenyl group;
An alkenyl-substituted aromatic hydrocarbon group in which the aromatic hydrocarbon group is substituted with an alkenyl group having 2 to 20 carbon atoms, such as a styryl group, 4-butenylphenyl group, and 4-octadecenylphenyl group;

The aromatic hydrocarbon group such as 4-fluorophenyl group, 2,6-fluorophenyl group, 4-chlorophenyl group, 2,3,4,5,6-perfluorophenyl group is fluorine atom, chlorine atom, bromine A halogenated aromatic hydrocarbon group substituted with a halogen such as an atom,
4- (2-ethoxyethyl) phenyl group, 4- (2-n-hexyloxyethyl) phenyl group, 4- (2-n-heptyloxyethyl) phenyl group, 4- (2-n-tetradecyloxyethyl) ) Phenyl group, 4- (2-cyclohexyloxyethyl) phenyl group, 4- (12-ethoxydodecyl) phenyl group, 4- (cyclohexyloxyethyl) phenyl group, etc., the aromatic hydrocarbon group has 3 to 20 carbon atoms. An alkoxyalkyl-substituted aromatic hydrocarbon group substituted with an alkoxyalkyl group of

4- (methylsulfanylpropyl) phenyl group, 4- (2-n-hexylsulfanylethyl) phenyl group, 4- (3-n-decylsulfanylpropyl) phenyl group, 4- (cyclohexylsulfanylpropyl) phenyl group, etc. An alkylsulfanylalkyl-substituted aromatic hydrocarbon group in which the aromatic hydrocarbon group is substituted with an alkylsulfanylalkyl group having 3 to 20 carbon atoms,

The above aromatic hydrocarbon groups such as 4- (3-octylaminopropyl) phenyl group, 4- (3-dodecylaminopropyl) phenyl group, and 4- (diethylaminoethyl) phenyl group are alkylamino having 3 to 20 carbon atoms. And alkylaminoalkyl-substituted aromatic hydrocarbon group substituted with an alkyl group.

Examples of the heteroaromatic group which may have a substituent include a pyrrolyl group, an indolyl group, a furyl group, a thienyl group, an imidazolyl group, a benzofuryl group, a triazolyl group, a benzotriazolyl group, a benzothienyl group, and a pyrazolyl group. , Indolizinyl group, quinolinyl group, isoquinolinyl group, carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, indolinyl group, thiazolyl group, pyridyl group, pyrimidyl group, pyrazinyl group, pyridazinyl group, thiadiazinyl group, oxadiazolyl group, benzoquinolinyl group, 5- or 6-membered heteroaromatic groups such as thiadiazolyl, pyrrolothiazolyl, pyrrolopyridazinyl, tetrazolyl and oxazolyl groups, and polycyclic heteroaromatics in which benzene is fused to the heteroaromatic group Group,
An alkyl-substituted heteroaromatic group in which the heteroaromatic group is substituted with an alkyl group having 1 to 20 carbon atoms, such as a 5-methylthienyl group, a 5-hexylthienyl group, a 5-decathienyl group, and a 5-stearylthienyl group;

A halogenated heteroaromatic group in which the heteroaromatic group is substituted with a halogen such as a fluorine atom, a chlorine atom or a bromine atom, such as a fluoropyridinyl group or a fluoroindolyl group;
5- (2-ethoxyethyl) thienyl group, 5- (2-n-tetradecyloxyethyl) thienyl group, 5- (2-cyclohexyloxyethyl) thienyl group, 5- (12-ethoxydodecyl) thienyl group, etc. An alkoxyalkyl-substituted heteroaromatic group in which the aromatic hydrocarbon group is substituted with an alkoxyalkyl group having 3 to 20 carbon atoms,

5- (methylsulfanylpropyl) thienyl group, 5- (2-n-hexylsulfanylethyl) thienyl group, 5- (3-n-decylsulfanylpropyl) thienyl group, 5- (cyclohexylsulfanylpropyl) thienyl group, etc. An alkylsulfanylalkyl-substituted heteroaromatic group in which the aromatic hydrocarbon group is substituted with an alkylsulfanylalkyl group having 3 to 20 carbon atoms,
Alkylaminoalkyl having 3 to 20 carbon atoms, such as 5- (3-octylaminopropyl) thienyl group, 5- (3-dodecylaminopropyl) thienyl group, 5- (diethylaminoethyl) thienyl group, etc. An alkylaminoalkyl-substituted heteroaromatic group substituted with a group, and the like.

Specific examples of the present invention having the substituents described above include the following.
However, it is not limited to these.

(Synthesis of the compound of the present invention)
The compound of the present invention can be synthesized by a combination of known and commonly used methods.
An example of a synthetic route can include the following.
(Example of synthetic route)

First, BTBT and unsaturated fatty acid chloride are subjected to Friedel-Crafts acylation reaction to introduce an unsaturated hydrocarbon ketone group at one end, and Wolff-Kishner reduction is performed to obtain an alkenylated compound. Next, the other side of the alkenyl substitution site is nitrated with fuming nitric acid, then reduced to an amino group with tin powder, then diazotized with a nitrous acid compound, and further iodinated by a Sandmeyer reaction to have a compound having an alkenyl group and iodine Get. Finally, the target compound can be obtained by Suzuki-Miyaura coupling between the compound and an aromatic or heteroaromatic boric acid compound.
The reaction is not particularly limited, and a known and commonly used reagent can be used, and any known and commonly used reaction temperature can be applied.

The reaction is not particularly limited, and a known and commonly used reagent can be used, and any known and commonly used reaction temperature can be applied.
The organic semiconductor material of the present invention obtained as described above is crystallized via a high-order liquid crystal phase with high order of molecular arrangement, and the arrangement of molecules is controlled after film formation. Express degree. In particular, the organic semiconductor material of the present invention is an asymmetric molecule having an alkenyl group on one side and an aromatic hydrocarbon group or heteroaromatic group on the other, which does not inhibit the liquid crystal phase and has a high molecular arrangement order. By adopting a structure, a wide liquid crystal phase temperature range is developed, and variation in mobility between elements is less than that of conventional compounds. Therefore, it is useful for various organic semiconductor devices.

(Liquid crystal phase)
The liquid crystal phase represented by the compound of the present invention is preferably a liquid crystal phase selected from the group consisting of SmB, SmBcryst, SmI, SmF, SmE, SmJ, SmG, SmK, and SmH. This is because when the liquid crystal material according to the present invention is used as an organic semiconductor in a liquid crystal phase, these liquid crystal phases have low fluidity, so that ionic conduction is difficult to induce, and because the molecular alignment order is high, high movement in the liquid crystal phase. This is because the degree can be expected. In addition, when the liquid crystal substance according to the present invention is used as an organic semiconductor in a crystal phase, these liquid crystal phases are less fluid than N phase, SmA phase, and SmC phase, so that the liquid crystal phase is increased by increasing the temperature. This is because the element is not easily destroyed even when it is transferred to. When the liquid crystal phase appears only in the temperature lowering process, once crystallized, the crystal temperature region is widened, which is convenient for application in the crystal phase. The compound of the present invention is characterized by showing a phase of SmBcryst, SmE, SmF, SmI, SmJ, SmG, SmK, or SmH in the temperature lowering process.

Further, among these SmBcryst, SmE, SmF, SmI, SmJ, SmG, SmK, or SmH, when SmE, SmG, which is a higher-order Sm phase, raises the temperature of the organic semiconductor material from the crystal phase, Particularly preferred as a liquid crystal phase appearing in a temperature region adjacent to the liquid crystal phase.
In addition, a liquid crystal substance in which a high-order liquid crystal phase appears in addition to a liquid-like low-order liquid crystal phase (N phase, SmA phase, or SmC phase) has high liquidity in the low-order liquid crystal phase. Since the molecular orientation is easier to control than the higher-order liquid crystal phase, the molecules are pre-aligned in the lower-order liquid crystal phase and then transferred to the higher-order liquid crystal phase. Since a liquid crystal thin film with few defects can be obtained, the quality of the liquid crystal thin film or the crystal thin film can be improved.

  When a liquid crystal material is used as an organic semiconductor, an operating temperature required for a device using the liquid crystal material is usually −20 ° C. to 80 ° C. Therefore, in the present invention, SmBcryst, SmE, SmF, SmI, SmJ, SmG, SmK, or The temperature region where the SmH phase appears is required to be −20 ° C. or higher. In addition, when the liquid crystal substance according to the present invention is used as an organic semiconductor in a crystal phase, it is effective to improve the quality by using a thin film in a liquid crystal state (liquid crystal thin film) as a precursor for producing a crystal thin film. For this reason, considering the simplicity of the process and the ease of selection of the substrate, the temperature at which the liquid crystal phase of the liquid crystal material appears is preferably 200 ° C. or lower.

  By using a molecular unit of an aromatic π-electron condensed ring system having a ring number of 3 or more as a charge transporting molecular unit corresponding to a core part in a liquid crystal molecule, redundancy of transfer integration for fluctuation of molecular position can be secured, Similarly, since the molecular conformation is fixed by adopting a molecular unit having a condensed ring structure instead of a π-electron conjugated molecular unit in which a plurality of benzene, thiophene, etc. are connected by a single bond, transfer integration Can be expected to increase the mobility, which helps improve mobility. Therefore, the BTBT skeleton of the present invention is effective as the unit.

  On the other hand, even if a large condensed ring structure is adopted as the core part of the charge transporting molecular unit, a substance in which a hydrocarbon chain is directly connected to the core part, such as dialkylpentacene and dialkylbenzothienobenzothiophene, is used. In general, the liquid crystal phase is not stabilized, and generally, the liquid crystal phase is not developed, or even if the liquid crystal phase is developed, only a low-order liquid crystal phase such as an SmA phase is developed (Liquid Liquid Crystal. Vol. 34. No. 9 (2007) 1001-1007. Liquid Crystal.Vol.30.No.5 (2003) 603-610). For this reason, even if a large condensed ring structure is simply used for the charge transporting molecular unit, high mobility cannot be realized in the liquid crystal phase. For the first time, a high-order liquid crystal can be obtained by adopting a molecular structure in the core part that connects another structural unit to give the degree of freedom of flip-flop motion of the molecule to the charge transporting molecular unit like the BTBT skeleton. Realization of high mobility in the liquid crystal phase is expected.

  Saturated or unsaturated hydrocarbon chains are connected to the structure (core part) in which another rigid structural unit such as an aromatic hydrocarbon or heteroaromatic structure is connected to the BTBT skeleton, and the molecule has a rod-like molecular shape. By imparting the anisotropy and liquidity, the liquid crystal phase can be induced with a high probability. When connecting hydrocarbon chains, it is common to connect two hydrocarbon chains, but even when there is only one hydrocarbon chain, a liquid crystal phase can often be developed. In this case, in general, the appearance temperature region of the liquid crystal phase is often asymmetric between the temperature lowering process and the temperature increasing process.

  This generally helps to extend the temperature range of the liquid crystal phase to a low temperature in the temperature lowering process, and conversely to expand the crystal phase to a high temperature range in the temperature rising process. In particular, when unsaturated hydrocarbon chains are connected, the liquid crystal transition temperature tends to decrease. This characteristic means that when a polycrystalline thin film of a liquid crystal material is used as an organic semiconductor, the liquid crystal thin film can be produced at a lower temperature when the polycrystalline thin film is produced using the liquid crystal thin film (thin liquid crystal phase thin film) as a precursor. However, there is an advantage that the process becomes easier. In addition, the fact that the crystal phase temperature in the temperature rising process spreads to a high region means that the thermal stability of the produced polycrystalline film is improved, which is convenient as a material. On the other hand, when two hydrocarbon chains are added, the developed liquid crystal phase is generally stabilized, which is convenient for application to a device using the liquid crystal phase.

  When a substance is synthesized based on the basic molecular design described above, the usefulness of the substance according to the present invention basically exhibits a higher-order smectic phase when used as an organic semiconductor in a liquid crystal phase. In addition, when used as an organic semiconductor in the crystalline phase, it is difficult to form cracks or voids in the crystalline thin film when cooled from a temperature higher than the crystalline phase temperature, and a low-order liquid crystal phase is expressed adjacent to the crystalline phase. It is made use of by choosing what does not. In other words, when used as an organic semiconductor in a liquid crystal phase, a liquid crystal phase other than a nematic phase, SmA phase, or SmC phase is expressed in a temperature region adjacent to the crystal phase, or when used as an organic semiconductor in a crystal phase. The criterion is that cracks and voids are less likely to form when cooled to a crystalline phase after cooling from a higher temperature range than the crystalline phase.

(Screening method)
This can be easily determined by the screening method (determination method) described below. For details of each measurement method used in this screening method, the following documents can be referred to as necessary.
Reference A: How to use a polarizing microscope: Experimental Chemistry 4th Edition, Volume 1, Maruzen, P429-435
Reference B: Evaluation of liquid crystal materials: Experimental Chemistry Course, 5th edition, 27, P295-300, Maruzen: Introduction to Liquid Crystal Science Experiments, Japanese Liquid Crystal Society, Sigma Publishing

(S1) After the isolated test substance is purified by column chromatography and recrystallization, it is confirmed by thin layer chromatography on silica gel that the test substance shows a single spot (that is, not a mixture).
(S2) Using a capillary phenomenon, the sample heated to the isotropic phase is injected into a 15 μm thick cell in which a slide glass is bonded through a spacer. Once the cell is heated to the isotropic phase temperature, the texture is observed with a polarizing microscope, and it is confirmed that no dark field is formed in a temperature region lower than the isotropic phase. This indicates that the molecular long axis is horizontally oriented with respect to the substrate, which is a requirement for subsequent texture observation.
(S3) The texture with a microscope is observed while cooling the cell at an appropriate temperature drop rate, for example, about 5 ° C./min. At this time, if the cooling rate is too high, the formed structure becomes small and detailed observation becomes difficult, so the temperature is increased to the isotropic phase again, the cooling rate is adjusted, and the structure is easily observed. The condition that the size of the tissue is easily 50 μm or more is set.

  (S4) The texture is observed while cooling from the isotropic phase to room temperature (20 ° C.) under the conditions set in (S3) above. When the sample crystallizes in the cell during this period, cracks and voids are generated as the lattice contracts, and black lines or regions having a certain size appear in the observed texture. When a sample is injected, a black area (generally round) similar to the presence of air is generated locally, but the black lines and areas generated by crystallization appear distributed in the tissue and at the boundary so that they can be easily distinguished. it can. These can be easily distinguished from other tissues found in the texture because no disappearance or color change is observed even when the polarizer and the analyzer are rotated. The temperature at which this texture appears is defined as the crystallization temperature, and it is confirmed that the texture appearing in a temperature region higher than that temperature is not a nematic phase, SmA phase, or SmC phase. When the sample shows a nematic phase, a characteristic schlieren texture expressed as a pincushion shape (a typical schlieren texture) is observed, and when it shows an SmA phase or an SmC phase, it has a fan shape called a fan-like texture. Since a characteristic texture having a uniform structure (a typical Fan-like texture) is observed in the region, it can be easily determined from the characteristic texture.

  As a special case, in the material that transitions from SmA phase to SmB phase, SmC phase to SmF, SmI phase, the visual field changes instantaneously at the phase transition temperature, but the phase transition texture almost changes. In some cases, the texture of the formed SmB phase, SmF phase, and SmI phase may be mistaken for the SmA phase and the SmC phase, so care should be taken. In that case, it is important to be aware of the instantaneous visual field changes seen at the phase transition temperature. When this confirmation is necessary, after confirming the number of intermediate phases by DSC, X-ray diffraction is measured in each temperature region, and a high-angle region (15-30 in the determination of θ-2θ) peculiar to each phase. If the presence or absence of a peak is confirmed, the SmA phase, the SmC phase (no peak), the SmB phase, the SmF phase, and the SmI phase (all have a peak) can be easily determined.

(S5) A material in which no black structure is observed by texture observation with a polarizing microscope at room temperature (20 ° C.) can be used as an organic semiconductor material. Therefore, this substance is a higher-order liquid crystal phase or crystal at room temperature. Regardless of the phase (including metastable crystalline phase), it shall be treated as a category of the present invention.
From the viewpoint of applying the organic semiconductor material according to the present invention to a device, the energy levels of the HOMO and LUMO of the core part are also important. In general, the HOMO level of an organic semiconductor is determined by dissolving a test substance in a dehydrated organic solvent such as dichloromethane to a concentration of, for example, 1 mmol / L to 10 mmol / L, and adding a supporting electrolyte such as a tetrabutylammonium salt. Add about 0.2 mol / L, insert a working electrode such as Pt, a counter electrode such as Pt, and a reference electrode such as Ag / AgCl into this solution, then sweep at a rate of about 50 mV / sec with a potentiostat, and CV curve The HOMO level and LUMO level can be estimated from the difference between the peak potential and the reference potential, for example, a known substance such as ferrocene. If the HOMO level and LUMO level are out of the potential window of the organic solvent used, the HOMO-LUMO level is calculated from the absorption edge of the UV-visible absorption spectrum and subtracted from the measured level. Can be estimated. This method is described in J. Org. Pomerehne, H.C. Vestweber, W.W. Guss, R.A. F. Mahrt, H.M. Bassler, M.M. Porsch, and J.M. Daub, Adv. Mater. , 7, 551 (1995).

In general, the HOMO and LUMO levels of an organic semiconductor material provide a measure of electrical contact with the anode and cathode, respectively, and charge injection is limited by the size of the energy barrier determined by the difference from the work function of the electrode material. So be careful. The work function of a metal is often silver (Ag) 4.0 eV, aluminum (Al) 4.28 eV, gold (Au) 5.1 eV, calcium (Ca) 2.87 eV, as examples of materials used as electrodes. Chromium (Cr) 4.5 eV, copper (Cu) 4.65 eV, magnesium (Mg) 3.66 eV, molybdenum (Mo) 4.6 eV, platinum (Pt) 5.65 eV, indium tin oxide (ITO) 4. 35 to 4.75 eV and zinc oxide (ZnO) 4.68 eV, but from the above viewpoint, the work function difference between the organic semiconductor material and the electrode substance is preferably 1 eV or less, more preferably 0.8 eV or less. More preferably, it is 0.6 eV or less. As for the work function of the metal, the following documents can be referred to as necessary.
Document D: Chemical Handbook Fundamentals Revised 5th Edition II-608-610 14.1 b Work Function (Maruzen Publishing Co., Ltd.) (2004)

  Since the HOMO and LUMO energy levels are affected by the size of the conjugated π-electron system in the core, the size of the conjugated system is a reference when selecting a material. As a method of changing the HOMO and LUMO energy levels, it is effective to introduce a hetero element into the core portion.

Applicable organic semiconductor devices include diodes, organic transistors, memories, photodiodes, light emitting diodes, light emitting transistors, sensors such as gas sensors, biosensors, blood sensors, immune sensors, artificial retinas, taste sensors, RFID, etc. Is mentioned.
Especially, since the organic-semiconductor material of this invention has a high charge mobility of 0.1 cm < ² > / Vs or more, the application to an organic transistor or a light-emitting device is especially useful. The organic transistor can be suitably used as a switching transistor, a signal driver circuit element, a memory circuit element, a signal processing circuit element, or the like of a pixel constituting the display. Examples of the display include a liquid crystal display, a dispersed liquid crystal display, an electrophoretic display, a particle rotating display element, an electrochromic display, an organic electroluminescence display, and electronic paper.

In addition, an organic transistor usually has a source electrode, a drain electrode and a gate electrode, a gate insulating layer, and an organic semiconductor layer, and there are various types of transistors depending on the arrangement of each electrode and each layer. The organic semiconductor material of the present invention is not limited to the type of transistor, and can be used for any transistor. For the types of transistors, reference can be made to Aldrich Basic Material Science No. 6 “Basics of Organic Transistors”.

(Confirmation of mobility as a semiconductor)
It is possible to confirm that the organic semiconductor material of the present invention has a mobility suitable for operation as a semiconductor by an experiment in a later-described example (measurement of transient photocurrent by Time-of-flight method). . For details on the confirmation of mobility by such a method, see, for example, the document Appl. Phys. Lett. , 71 No. 5 602-604 (1997).

The usefulness of organic semiconductors when applied to devices is based on the mobility of the material. This is because the device characteristics are limited by mobility. Conventionally, an amorphous organic semiconductor has a high mobility of about 10 ⁻² cm ² / Vs, and generally has a value of 10 ⁻⁵ to 10 ⁻³ cm ² / Vs. Accordingly, a high mobility exceeding 10 ⁻² cm ² / Vs exhibited by the liquid crystal phase, in particular, a mobility exceeding 0.1 cm ² / Vs exhibited by the high-order smectic phase is difficult to realize with an amorphous organic semiconductor material, and the liquid crystal material The advantage of is obvious.

  Since the liquid crystalline material exhibits a crystal phase like the non-liquid crystal material, it goes without saying that when the liquid crystal material is used as an organic semiconductor, it can be used not only in the liquid crystal phase but also in the crystalline phase as an organic semiconductor. In general, the mobility in the crystal phase is often about half to one digit higher than the mobility in the liquid crystal phase. In particular, transistor applications that require high mobility and large diffusion lengths of charges and excitons. The use of a crystalline phase is effective for the required application to solar cells and the like.

(Confirm semiconductor device operation)
As shown in the Examples, it is possible to confirm that the organic semiconductor material of the present invention can be used as an organic transistor by fabricating an FET and evaluating its characteristics.
For details of the semiconductor device operation confirmation by such a method, see, for example, the document S.A. F. Nelson, Y .; -Y. Lin, D.D. J. et al. Gundlach, and T.G. N. Jackson, Temperature-independent transport in high-mobility penentene transistors, Appl. Phys. Lett. , 72, no. 15 1854-1856 (1998).

The invention is explained in more detail in the examples.
<Fabrication of transistor>
A silicon wafer with a thermal oxide film (heavy doped p-type silicon (P + -Si), thermal oxide film (SiO ₂ ) thickness: 300 nm) was cut to 20 × 25 mm, and this cut silicon wafer (hereinafter abbreviated as a substrate) Ultrasonic cleaning was performed in the order of neutral detergent, ultrapure water, isopropyl alcohol (IPA), acetone, and IPA.
Next, the liquid crystalline organic semiconductor compound was dissolved in xylene to prepare a solution. The concentration of the solution was 1 wt% to 0.5 wt%. The solution and a glass pipette for applying the solution to the substrate are heated in advance on a hot stage to a predetermined temperature, and the substrate is placed on a spin coater placed in an oven. After raising the temperature to 0 ° C., the solution was applied onto the substrate, and the substrate was rotated (about 3000 rpm, 30 seconds). After stopping the rotation, the substrate was quickly taken out and cooled to room temperature.
Further, a source / drain electrode was formed on the substrate coated with the organic semiconductor layer by pattern deposition of gold through a metal mask using a vacuum deposition method (2 × 10 ⁻⁶ Torr) (channel length: Channel width = 75 μm: 3000 μm).
The evaluation of the fabricated organic transistor was conducted by applying a sweep current to the gate electrode (P + -Si) using a source / measurement unit with two power supplies in a normal atmosphere. This was performed by measuring (transfer characteristics) while (Vsg: +40 to −60 V) (voltage Vsd between source electrode and drain electrode: −80 V). The mobility was calculated from the slope of √Id−Vg in the transfer characteristic by a known method using a saturation characteristic equation. In addition, the measurement of mobility was performed about five transistors, The average value and the standard deviation were described.

Example 1
Tetrahedron Letters, Vol. BTBT (7.2 g, 30 mmol) obtained by the method described on pages 52 and 285 was dissolved in 400 mL of dichloromethane, cooled to −70 ° C., 15.9 g (120 mmol) of aluminum chloride was added, and then Journal of Medicinal Chemistry, Vol. . A solution prepared by dissolving 8.16 g (30 mmol) of 9-hexadecenoyl chloride obtained by the method described on pages 36, 2595 in 20 mL of dichloromethane was added dropwise. Further, after stirring for 4 hours at the same temperature, the reaction solution was poured into cold water, and the precipitated crystals were collected by filtration and washed with distilled water and methanol in this order. The obtained crystals were recrystallized from toluene to obtain 10.3 g (yield 72%) of 7- (9-hexadecenoyl) BTBT as pale yellow crystals.

Next, 7- (9-hexadecenoyl) BTBT 10 g (21 mmol), potassium hydroxide 4.7 g (84 mmol), and hydrazine hydrate 63 mL (0.53 mol) were added to diethylene glycol 980 mL, and the mixture was stirred at 100 ° C. for 1 hour, Furthermore, it reacted at 210 degreeC for 5 hours. The reaction mixture was cooled and the precipitated crystals were collected by filtration and then washed with distilled water and methanol in this order. The obtained crystals were recrystallized from toluene to obtain 8.1 g (yield 83.5%) of 7- (9-hexadecene) BTBT pale yellow crystals.

  Next, 6.01 g (13 mmol) of 7- (9-hexadecene) BTBT was dissolved in 320 mL of dichloromethane and then cooled to −50 ° C., and 24 mL of 1.2 M dichloromethane solution of fuming nitric acid was added dropwise over 30 minutes. After further stirring at −50 ° C. for 2 hours, 26 mL of saturated aqueous sodium hydrogen carbonate solution was added to stop the reaction. The lower layer was separated by separation, washed with 10% brine, dried over anhydrous magnesium sulfate and concentrated to dryness to obtain a crude solid. This solid was recrystallized from methyl isobutyl ketone to obtain 4.01 g (yield, 61%) of yellow crystals of 2- (9-hexadecene) -7-nitroBTBT.

Next, 3.04 g (6 mmol) of 2- (9-hexadecene) -7-nitroBTBT and 1.84 g of tin powder are suspended in 30 mL of acetic acid, and slowly heated to about 70 ° C. with stirring and 5.4 mL of concentrated hydrochloric acid. It was dripped. Furthermore, after reacting at 100 ° C. for 1 hour, the mixture was cooled to 10 ° C. or lower and the solid was collected by filtration. This solid was dispersed in about 100 mL of chloroform, washed sequentially with concentrated aqueous ammonia and saturated brine, dried over anhydrous magnesium sulfate, and concentrated to dryness to obtain a crude solid. This solid was separated and purified on a silica gel column (chloroform / cyclohexane = 1/2, 1% triethylamine added) and recrystallized from petroleum benzine to give slightly gray 2-amino-7- (9-hexadecyl) BTBT 2.24 g (Yield, 78%) was obtained.

Furthermore, 60 mL of dichloromethane was added to 1.91 g (4 mmol) of 2-amino-7- (9-hexadecyl) BTBT, and 864 mg of trifluoroborate ether complex and 504 mg of t-butyl nitrite were added dropwise under cooling at −15 ° C. After raising the reaction temperature to 5 ° C. in about 1 hour, a solution of 1.6 g of iodine, 1.32 g of potassium iodide and 100 mg of tetrabutylammonium iodide in a dichloromethane-THF mixture (1: 2) 12 mL was added. The mixture was reacted for 8 hours under reflux with heating, diluted with chloroform, washed successively with 10% sodium thiosulfate, 5M sodium hydroxide, and 10% brine, dried over anhydrous sodium sulfate, and concentrated to dryness. The resulting dark brown crude solid was purified on a silica gel column (chloroform / cyclohexane = 1/2) and crystallized from chloroform-methanol. Subsequently, recrystallization from ligroin yielded 988 mg of 2- (9-hexadecene) -7-iodoBTBT (yield 42%).

Finally, 8 mL of dioxane, 0.5 mL of 2M tripotassium phosphate, 73 mg (0.6 mmol) of phenylboric acid were added to 294 mg (0.5 mmol) of 2- (9-hexadecene) -7-iodoBTBT, and argon gas was added for 20 minutes. After bubbling, tetrakis (triphenylphosphine) palladium 30 mg (0.025 mmol, Tokyo Chemical Industry) and tricyclohexylphosphine 13 mg (0.045 mmol, Wako Pure Chemical Industries) were added, and the mixture was heated and stirred at 95 ° C. for 22 hours. The reaction solution was diluted with chloroform, washed with 10% brine, and the lower layer was concentrated to dryness to obtain a crude solid. This solid was recrystallized from xylene to obtain 172 mg (yield 64%) of the compound represented by (Chemical Formula 5 ).

(Example 2)
As a result of evaluating the compound obtained in Example 1 by the above method, it was as follows.
Mobility: 0.65 cm ² / Vs
・ Standard deviation of mobility: 0.042
On-off ratio: 2.0 × 10 ⁶

(Comparative Example 1)

ＷＯ２００６／０７７８８８記載の方法にて上記化合物を合成し、実施例２と同様の手法で評価した結果は下記の通りであった。
・移動度：０．１１ｃｍ^２／Ｖｓ
・移動度の標準偏差：０．０５９
・オンオフ比：１．０×１０^６

The above compounds were synthesized by the method described in WO2006 / 077788, and the results evaluated by the same method as in Example 2 were as follows.
Mobility: 0.11 cm ² / Vs
-Mobility standard deviation: 0.059
On-off ratio: 1.0 × 10 ⁶

  The compound of the present invention can be used as an organic semiconductor, and can be used for an organic transistor using the organic semiconductor material as an organic semiconductor layer.

Claims (3)

General formula (1)

(In the formula, _{R 1} is an alkenyl group having a carbon number of 3 to 20, _{R 2} is an aromatic hydrocarbon group or a heteroaromatic group, an alkyl group or an alkenyl group having 2 to 20 carbon atoms having 2 to 20 carbon atoms Aromatic hydrocarbon group or heteroaromatic group as a substituent, an aromatic hydrocarbon group or heteroaromatic group having a halogen atom-containing alkyl group having 2 to 20 carbon atoms as a substituent, or an alkoxy group having 3 to 20 carbon atoms An aromatic hydrocarbon group or heteroaromatic group having an alkyl group as a substituent, an aromatic hydrocarbon group or heteroaromatic group having an alkylsulfanylalkyl group having 3 to 20 carbon atoms as a substituent, 3 to 20 carbon atoms A group selected from an aromatic hydrocarbon group or a heteroaromatic group having an alkylaminoalkyl group as a substituent)
Organic semiconductor material represented by An organic semiconductor device comprising the organic semiconductor material according to claim 1. An organic transistor using the organic semiconductor material according to claim 1 as an organic semiconductor layer.