JP5500534B2 - Organic semiconductor device - Google Patents

Description

  The present invention relates to an organic semiconductor element including a photo-alignment film and an organic semiconductor film.

  In recent years, research and development of organic semiconductor elements aimed at display applications has been activated by taking advantage of the characteristics of organic materials that can be increased in area, such as ultralight, compact, and flexible.

  It is known that the carrier mobility of an organic semiconductor film strongly depends on its crystallinity and crystal form, and the carrier mobility in a single crystal of an organic semiconductor depends on the crystal orientation (see, for example, Non-Patent Document 1). .)

An organic semiconductor film for an organic semiconductor element is generally manufactured by a vacuum deposition method or a solution method. Specifically, when pentacene or oligothiophene is deposited on an insulating film by vacuum deposition, it is known that a thin-film crystal phase in which these molecules are aligned on the insulating film surface on a substantially vertical average is obtained. (For example, see Non-Patent Documents 2 to 6.) When the insulating film is SiO _2, the molecular orientation is improved by modifying the SiO ₂ surface with HMDS or OTS, and accordingly, the carrier mobility is improved. In addition, it has been reported that in pentacene, a thin film crystal phase in which pentacene molecules are aligned on the insulating film surface in an almost vertical direction on average can be obtained by the solution method (for example, Non-Patent Document 7, (See Patent Document 1).
However, in these methods, since in-plane anisotropy cannot be controlled, alignment control is insufficient. When considering application to organic field effect transistors, in order to maximize the charge mobility of an organic semiconductor element, the crystal axis with the maximum mobility, such as a single crystal, is set for each organic semiconductor element. It is necessary to align in the channel length direction. That is, development of in-plane orientation control technology is desired in addition to aligning semiconductor material molecules on an insulating film of a substrate.

Appl.Phys.Lett.88,252106 (2006) M J.RES. & DEV.VOL.45 No.1 JANUARY 2001 Thin Solid Films 464-465 (2004) 398-402 Bull.Chem.Soc.Jpn., 76,1561-1567 (2003) Liquid Crystal Volume 10 Issue 1 52-59 (2006) nature materials Vol.5 222-228 (2006) Synthetic Metals 153 (2005) 1-4 JP 2004-256532 A

  An object of the present invention is to provide an organic semiconductor element in which the orientation of organic semiconductor molecules (particularly the orientation in the substrate plane) is controlled to improve the crystallinity and morphology of the organic semiconductor film and to improve the carrier mobility. And

  The inventors diligently studied to solve the problems of the present invention. As a result, by using a polyimide photo-alignment film having a very large in-plane anisotropy as an alignment template insulating film for organic semiconductor molecules, not only the pentacene molecules are aligned almost vertically on the insulating film surface, but also in-plane The inventors have found that the orientation in the direction can also be controlled, and have completed the present invention.

式中、Ａ‖は配向処理方向に平行な偏光成分を有する赤外光を配向膜に入射させたときの特性基振動による吸光度であり、Ａ⊥は配向処理方向に垂直な偏光成分を有する赤外光を配向膜に入射させたときの配向膜の特性基振動による吸光度である。
［３］ 前記配向処理が、アゾ基の光異性化反応を利用した配向処理である前記［１］項または前記［２］項記載の有機半導体素子。
［４］ 前記配向処理が、ポリアミック酸膜に直線偏光紫外光を照射した後に、熱イミド化する配向処理である前記［１］項または前記［２］項記載の有機半導体素子。
［５］ 前記有機半導体膜が、光配向膜上に真空蒸着法により製膜されることを特徴とする前記［１］〜［４］のいずれか１項記載の有機半導体素子。
［６］ 前記有機半導体膜が、光配向膜上に溶液法により製膜されることを特徴とする前記［１］〜［４］のいずれか１項記載の有機半導体素子。
［７］ 前記有機半導体膜が、光配向膜上に製膜することで面内異方性を形成することができる有機半導体化合物を含有することを特徴とする前記［１］〜［６］のいずれか１項記載の有機半導体素子。
［８］ 前記有機半導体化合物が、アセン、オリゴチオフェン、ジチエニルアセン、２，７−ジフェニル[１]ベンゾチエノ[３，２−ｂ][１]ベンゾチエノフェン、ポルフィリン、ルブレンまたはこれらの誘導体からなる群から選ばれる少なくとも１種である前記［７］項記載の有機半導体素子。 The present invention has the following configuration.
[1] An organic semiconductor element including a photo-alignment film and an organic semiconductor film. The photo-alignment film is polyimide that has been subjected to alignment treatment by light irradiation. The organic semiconductor film is a surface on the photo-alignment film. An organic semiconductor element having internal anisotropy.
[2] When the photo-alignment film is subjected to alignment treatment by light irradiation, the absolute value | Δ | of the alignment index of the alignment film represented by the formula (1) is 0 <| Δ | ≦ 1 The organic semiconductor element according to the above [1].

In the formula, A‖ is the absorbance due to the characteristic group vibration when infrared light having a polarization component parallel to the alignment treatment direction is incident on the alignment film, and A⊥ is a red light having a polarization component perpendicular to the alignment treatment direction. This is the absorbance due to the characteristic group vibration of the alignment film when external light is incident on the alignment film.
[3] The organic semiconductor element according to the above [1] or [2], wherein the alignment treatment is an alignment treatment using a photoisomerization reaction of an azo group.
[4] The organic semiconductor element according to the item [1] or [2], wherein the alignment treatment is an alignment treatment in which thermal imidization is performed after the polyamic acid film is irradiated with linearly polarized ultraviolet light.
[5] The organic semiconductor element according to any one of [1] to [4], wherein the organic semiconductor film is formed on a photo-alignment film by a vacuum deposition method.
[6] The organic semiconductor element according to any one of [1] to [4], wherein the organic semiconductor film is formed on a photo-alignment film by a solution method.
[7] The above-mentioned [1] to [6], wherein the organic semiconductor film contains an organic semiconductor compound capable of forming in-plane anisotropy by being formed on a photo-alignment film. The organic-semiconductor element of any one of Claims.
[8] The organic semiconductor compound is selected from the group consisting of acene, oligothiophene, dithienyl acene, 2,7-diphenyl [1] benzothieno [3,2-b] [1] benzothienophen, porphyrin, rubrene, or derivatives thereof. The organic semiconductor device according to the above [7], which is at least one selected.

  ADVANTAGE OF THE INVENTION According to this invention, the organic-semiconductor element with the outstanding mobility is obtained by improving the orientation controllability of the molecule | numerator of the organic-semiconductor compound in an organic-semiconductor film.

式中、Ａ‖は配向処理方向に平行な偏光成分を有する赤外光を配向膜に入射させたときの特性基振動による吸光度であり、Ａ⊥は配向処理方向に垂直な偏光成分を有する赤外光を配向膜に入射させたときの配向膜の特性基振動による吸光度である。 The organic semiconductor element of the present invention includes a photo-alignment film and an organic semiconductor film, and the photo-alignment film is polyimide that has been subjected to alignment treatment by light irradiation, and the organic semiconductor film is a surface on the photo-alignment film. It is an organic semiconductor film having internal anisotropy. In the present invention, a photo-alignment film can be obtained by setting the absolute value of the orientation index of the alignment film represented by the specific formula to 0 <| Δ | ≦ 1 by irradiating the alignment film with light and performing an alignment treatment. By forming a molecule of an organic semiconductor compound such as a pentacene molecule on this photo-alignment film by a vacuum deposition method or a solution method, the in-plane anisotropy of the organic semiconductor film can be controlled, It can be oriented almost vertically. Thereby, an organic semiconductor element having excellent mobility can be obtained.

In the formula, A‖ is the absorbance due to the characteristic group vibration when infrared light having a polarization component parallel to the alignment treatment direction is incident on the alignment film, and A⊥ is a red light having a polarization component perpendicular to the alignment treatment direction. This is the absorbance due to the characteristic group vibration of the alignment film when external light is incident on the alignment film.

  In the present invention, the orientation state of organic semiconductor molecules such as pentacene molecules can also be evaluated by the orientation index Δ of the photo-alignment film represented by the formula (1).

  A rubbing method, a photo-alignment method, a transfer method and the like are generally known as an alignment treatment method for the alignment film. In the present invention, a method for performing alignment treatment by irradiating light, that is, a photo-alignment method is used. Many alignment mechanisms such as photolysis, photoisomerization, photodimerization, and photocrosslinking have been proposed for the photoalignment method, but can be similarly applied as long as the object of the present invention is achieved. It is. In the present invention, the alignment treatment direction refers to the polarization direction of light used for the alignment treatment. A photo-alignment method that can be particularly preferably used in the present invention is a method utilizing a photoisomerization reaction such as an azo group, and after irradiating a linearly polarized ultraviolet light to a polyamic acid film containing an azo group or the like in the main chain, An alignment treatment is performed by thermal imidization. According to this orientation treatment method, a large orientation index Δ, which was difficult with the conventional rubbing method or transfer method, can be easily obtained, and the orientation index can be finely controlled by the irradiation amount of linearly polarized ultraviolet light, so that particularly excellent mobility is achieved. It is possible to manufacture an organic semiconductor device having

The orientation index Δ of the photo-alignment film can be evaluated by infrared absorption spectroscopy using polarized infrared light. This method is a method for evaluating molecular orientation by detecting infrared dichroism in which the amount of infrared absorption when two linearly polarized infrared rays orthogonal to a sample are incident differs depending on the molecular orientation. That is, a polarizer is arranged between a light source of an infrared spectrophotometer (preferably FT-IR) and a sample holder holding a sample having a photo-alignment film, and the alignment treatment direction is parallel to the polarization direction of the polarizer. In this manner, the sample is fixed to the sample holder, and the infrared absorbance is measured. Next, in the state where the sample is fixed to the sample holder, the sample holder is rotated 90 degrees, and the infrared absorbance is measured so that the polarized infrared light passing through the polarizer is incident on the sample perpendicular to the alignment treatment direction. In the infrared absorbance thus obtained, Δ is calculated from the value at the peak wavelength of absorption or the integrated intensity caused by molecular vibration polarized in parallel or perpendicular to the molecular axis of polyimide. Incidentally, the scope of the method, the silicon and calcium fluoride (fluorite: CaF _2), such as limited to a sample infrared light is created on a substrate which transmits. Since infrared light does not pass through the glass substrate, this method cannot measure the molecular orientation of the sample prepared on the glass substrate. However, when the orientation index is evaluated using absorption of the π-π * transition of azobenzene, a glass substrate can be used because it can be evaluated by ultraviolet / visible light absorption.

The characteristic group frequency of the photo-alignment film used in the present invention is, for example, the peak of the strong infrared absorption spectrum is around 1370 cm ⁻¹ due to the stretching vibration of the C—N bond of the (CO) ₂ NC structure, and the phenyl group C near 1503cm ^-1 due to the stretching vibration of -C bonds, preferably to assess the orientation index Δ by maximum peak height or the integrated intensity of the absorbance spectrum in the vicinity 1726 cm ^-1 due to the asymmetric stretching vibration of C = O.

  The photo-alignment film used in the present invention is a photo-alignment film in which the absolute value | Δ | of the orientation index of the alignment film represented by the formula (1) is 0 <| Δ | ≦ 1. When there is no in-plane anisotropy, that is, when there is no orientation, | Δ | = 0, and when it is completely oriented in either direction, | Δ | = 1. If the absolute value | Δ | of the alignment index of the photo-alignment film is larger than 0, the in-plane anisotropy of the organic semiconductor film can be obtained. Furthermore, the larger the absolute value | Δ | of the orientation index of the orientation film, the greater the in-plane anisotropy of the organic semiconductor film, and the mobility of the organic semiconductor element is improved.

  The film thickness of the photo-alignment film used in the present invention is not particularly specified, but is usually 10 to 150 nm. When used for the purpose of controlling the orientation of the organic semiconductor film on the gate insulating film, a sufficient effect can be obtained with about 10 nm. In addition, the alignment film itself can be used as a gate insulating film. In this case, it is necessary to make it relatively thick as necessary. Usually, it is about 50 to 150 nm.

  The aligning agent that can form the photo-alignment film used in the present invention is a solution in which a polymer compound such as polyamic acid, polyamic acid ester, soluble polyimide, and polyamideimide is dissolved in a solvent. In the present invention, this solution is called varnish. A photo-alignment film is formed by applying this alignment agent onto a substrate, drying the solvent, and then performing an alignment treatment. The polymer compound may be a copolymer such as a random copolymer or a block copolymer, and a plurality of types of polymer compounds may be used in combination.

  A particularly preferred aligning agent for forming the alignment film used in the present invention is a polyamic acid obtained by reacting a tetracarboxylic dianhydride or the like with a diamine or a soluble polyimide obtained by a dehydration reaction of the polyamic acid or the like. Contains varnish.

  In the present invention, the photo-alignment treatment may utilize a photoisomerization reaction, a photolysis reaction, a photodimerization reaction, a photocrosslinking reaction, or the like. The polymer compound forming the alignment film needs to have a molecular structure that causes such a reaction when irradiated with light.

  In the case of performing photo-alignment treatment using a photoisomerization reaction, for example, when the aligning agent is a solution of polyamic acid or soluble polyimide, at least one tetracarboxylic dianhydride as a raw material thereof And / or at least one of diamines preferably has a structure that undergoes a photoisomerization reaction such as an azo group.

  Particularly preferably, a diamine represented by the general formula (2) is used.

  In addition, when photo-alignment treatment is performed by photolysis reaction, for example, when the aligning agent is a polyamic acid or a soluble polyimide solution, the raw materials tetracarboxylic dianhydride and diamine are not particularly limited. It can be used without.

  Furthermore, in the case where the photo-alignment treatment is performed by a photodimerization reaction, for example, when the alignment agent is a solution of polyamic acid or soluble polyimide, at least one of tetracarboxylic dianhydride as a raw material, and At least one of the diamines preferably has a structure that undergoes a photodimerization reaction such as a cinnamoyl group, a coumarin group, or a chalcone group.

  Furthermore, in the case where the photo-alignment treatment is performed by a photocrosslinking reaction, for example, when the alignment agent is a polyamic acid or a soluble polyimide solution, at least one tetracarboxylic dianhydride that is a raw material thereof, and At least one of diamines preferably has a structure that undergoes a photocrosslinking reaction such as a benzophenone group.

  Other tetracarboxylic dianhydrides that give a polyamic acid or soluble polyimide, which is a polymer compound contained in the alignment agent used in the present invention, are aromatic (heteroaromatic rings) in which a dicarboxylic anhydride is bonded directly to an aromatic ring. And aliphatic systems (including heterocyclic systems) in which the dicarboxylic anhydride is not directly bonded to the aromatic ring.

Specific examples of the tetracarboxylic dianhydride that can be used in the present invention are as follows.

  Among these, Formula (3-1), Formula (3-2), Formula (3-7), Formula (3-13), Formula (3-17), Formula (3-18), Formula (3) -19), formula (3-20), formula (3-27), formula (3-28), and tetracarboxylic dianhydride represented by formula (3-29) are preferable. More preferably, Formula (3-1), Formula (3-7), Formula (3-13), Formula (3-17), Formula (3-19), Formula (3-20), and Formula (3- It is a tetracarboxylic dianhydride represented by 29).

  Other tetracarboxylic dianhydrides that can be used in the present invention are not limited to these, and other compounds having various molecular structures exist within the scope of achieving the object of the present invention. Not too long. Moreover, these tetracarboxylic dianhydrides can be used not only alone but also in combination of two or more.

  The orientation of the aliphatic tetracarboxylic dianhydride is likely to be lost, particularly when firing at a low temperature of 180 ° C. or lower. On the other hand, aromatic tetracarboxylic dianhydrides are excellent in alignment stability. Therefore, it is more preferable to use an aromatic tetracarboxylic dianhydride and an aliphatic tetracarboxylic dianhydride in combination.

In the present invention, specific examples of diamines having no side chain structure that give polyacic acid or soluble polyimide, which is a polymer compound used in the aligning agent, are as follows.
N in the following specific examples is an integer of 1-20. Any hydrogen in the cyclohexane ring and the benzene ring may be replaced by halogen or alkyl having 1 to 5 carbon atoms.

  Among these, Formula (4-5), Formula (4-6), Formula (4-7), Formula (4-8), Formula (4-9), Formula (4-10), Formula (4) -11), formula (4-12), formula (4-13), formula (4-14), formula (4-15), formula (4-16), formula (4-17), formula (4- 18), Formula (4-23), Formula (4-27), Formula (4-32), Formula (4-33), Formula (4-34), Formula (4-35), and Formula (4- The diamine represented by 36) is preferred. By using these diamines, a high orientation index Δ is easily obtained.

  In the present invention, specific examples of diamines having other side chain structures that give polyacic acid or soluble polyimide, which is a polymer compound used in the aligning agent, are as follows.

  As the diamine having a side chain structure, one or more of various diamines having a side chain structure branched from the main chain of the amine can be used. The diamine having a side chain structure is preferably a diamine represented by the general formula (5) because it improves the molecular alignment stability of the organic semiconductor compound.

In the general formula (5), the bonding position relationship between the two amino groups is preferably meta or para. Furthermore, in the general formula (5), two amino groups are bonded to the phenyl ring carbon, but each of the two amino groups is 3 when the bonding position of “R ² —R ¹ —” is the 1st position. It is preferably bonded to the 5-position or 2-position and 5-position.

In the general formula (5), R ¹ is a single bond, —O—, —COO—, —OCO—, —CO—, —CONH— or — (CH ₂ ) _m —, where m is 1 Is an integer of ˜6, and R ² is carbon when the positional relationship between the group having a steroid skeleton, the group represented by the following general formula (6), or two amino groups bonded to the benzene ring is para. An alkyl having 1 to 20 carbon atoms, or an alkyl having 1 to 10 carbon atoms or phenyl when the positional relationship is meta. In the alkyl, any —CH ₂ — is independently —CF ₂ —, — CHF—, —O—, —CH═CH— or —C≡C— may be substituted, and —CH ₃ may be substituted with —CH ₂ F, —CHF ₂ or —CF ₃ , The hydrogen bonded to the phenyl ring-forming carbon is independently -F. _{-CH 3, -OCH 3, -OCH 2} F, may be replaced with -OCHF ₂ or -OCF _3.

In the general formula (6), A ¹ and A ² each independently represent a single bond, —O—, —COO—, —OCO—, —CONH—, —CH═CH—, or C 1-20. Alkylene, R ³ and R ⁴ are each independently —F or —CH ₃ , and ring S is 1,4-phenylene, 1,4-cyclohexylene, 1,3-dioxane-2,5- Diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, naphthalene-1,5-diyl, naphthalene-2,7-diyl or anthracene-9,10-diyl, R ⁵ is —H, -F, alkyl having 1 to 20 carbon atoms, a fluorine-substituted alkyl having 1 to 20 carbon atoms, having 1 to 20 carbon atoms alkoxy, _-CN, -OCH 2 F, a -OCHF ₂ or -OCF _3, a and b Are independently an integer from 0 to 4 And when a or b is 2 to 4, adjacent A ¹ or A ² are different groups, c, d and e each independently represent an integer of 0 to 3, and e is 2 or 3 The plurality of rings S may be the same group or different groups, and f and g each independently represent an integer of 0 to 2 and c + d + e ≧ 1.

  Examples of the diamine represented by the general formula (5) include diamines represented by the formulas (5-1) to (5-11).

In the formula, R ⁵ is preferably alkyl having 3 to 12 carbons or alkoxy having 3 to 12 carbons, more preferably alkyl having 5 to 12 carbons or alkoxy having 5 to 12 carbons. R ⁶ is preferably alkyl having 1 to 10 carbons or alkoxy having 1 to 10 carbons, more preferably alkyl having 3 to 10 carbons or alkoxy having 3 to 10 carbons.

  Of these, diamines represented by formula (5-2), formula (5-4), formula (5-5), and formula (5-6) are more preferable.

  The diamine of the present invention may contain the diamine represented by the general formula (5) alone or may contain two or more kinds.

  Furthermore, a diamine having a side chain structure other than the diamine represented by the general formula (5) can be used as long as the object of the present invention is not impaired. Examples of such a diamine having a side chain structure include diamines represented by formulas (5'-1) to (5'-20).

In the formulas (5′-1) to (5′-3), R ⁷ is preferably alkyl having 4 to 16 carbons, and more preferably alkyl having 6 to 16 carbons. In formula (5′-4), R ⁸ is preferably alkyl having 6 to 20 carbons, and more preferably alkyl having 8 to 20 carbons.

In the formula, R ⁹ is preferably alkyl having 3 to 12 carbons or alkoxy having 3 to 12 carbons, more preferably alkyl having 5 to 12 carbons or alkoxy having 5 to 12 carbons. R ¹⁰ is preferably alkyl having 1 to 10 carbons or alkoxy having 1 to 10 carbons, more preferably alkyl having 3 to 10 carbons or alkoxy having 3 to 10 carbons.

  Furthermore, siloxane type diamine which has a siloxane bond can be mentioned as another diamine which can be used together with said diamine which can be used by this invention. Although this siloxane type diamine is not specifically limited, What is represented by Formula (7) can be preferably used in this invention.

式中、Ｒ^１１およびＲ^１２は独立して炭素数１〜３のアルキルまたはフェニルであり、Ｒ^１３はメチレン、フェニレンまたはアルキル置換されたフェニレンである。ｘは１〜６の整数であり、ｙは１〜１０の整数である。

In the formula, R ¹¹ and R ¹² are each independently alkyl or phenyl having 1 to 3 carbon atoms, and R ¹³ is methylene, phenylene or alkyl-substituted phenylene. x is an integer of 1-6, and y is an integer of 1-10.

  Other diamines that can be used in the present invention are not limited to these, and it goes without saying that other compounds having various molecular structures exist within the scope of achieving the object of the present invention. These diamines can be used alone or in combination of two or more.

  On the other hand, diamines that can be used in the present invention are also aromatic systems (including heteroaromatic ring systems) in which an amino group is directly bonded to an aromatic ring, as well as the tetracarboxylic dianhydrides described above. Aliphatic systems (including heterocyclic systems) with no group attached can be used.

  Furthermore, in addition to these tetracarboxylic dianhydrides and diamines, it is also possible to use a polyamic acid, a monoamine and / or a monocarboxylic anhydride that forms the reactive terminal of a soluble polyimide. In order to improve the adhesion to the substrate, an aminosilicon compound can be introduced.

  Examples of aminosilicon compounds are paraaminophenyltrimethoxysilane, paraaminophenyltriethoxysilane, metaaminophenyltrimethoxysilane, metaaminophenyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, and the like.

  Although the density | concentration of the high molecular compound in the aligning agent used for this invention is not specifically limited, 0.1 to 40 weight% is preferable. When the aligning agent is applied to the substrate, an operation of diluting the polymer compound contained therein with a solvent in advance may be required for film thickness adjustment. When the concentration of the polymer compound is 40% by weight or less, the viscosity of the aligning agent becomes preferable, and when the aligning agent needs to be diluted for film thickness adjustment, the solvent can be easily mixed with the aligning agent. Therefore, it is preferable. In the case of a coating method such as a spinner method or a printing method, in order to keep the film thickness good, it is usually often 10% by weight or less. Other coating methods such as a dipping method or an ink jet method may further reduce the concentration. On the other hand, when the concentration of the polymer compound is 0.1% by weight or more, the thickness of the obtained alignment film tends to be preferable. Accordingly, the concentration of the polymer compound is 0.1% by weight or more, preferably 0.5 to 10% by weight in a coating method such as a normal spinner method or printing method. However, depending on the method of applying the alignment agent, it may be used at a dilute concentration. As the substrate, silicon wafer, glass, polyethylene naphthalate, polyimide or other plastics can be used.

  In the aligning agent used in the present invention, the solvent used together with the polymer compound can be applied without particular limitation as long as it is a solvent capable of dissolving the polymer compound. Such a solvent includes a wide range of solvents that are generally used in the production process and applications of polymer compounds such as polyamic acid and soluble polyimide, and can be appropriately selected according to the purpose of use. Examples of these solvents are as follows.

  Examples of aprotic polar organic solvents that are the parent solvents for polyamic acids and soluble polyimides include N-methyl-2-pyrrolidone, dimethylimidazolidinone, N-methylcaprolactam, N-methylpropionamide, N, N-dimethyl. Mention may be made of lactones such as acetamide, dimethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide, N, N-diethylacetamide, and γ-butyrolactone.

  Examples of other solvents for improving coating properties include alkyl lactate, 3-methyl-3-methoxybutanol, tetralin, isophorone, ethylene glycol monoalkyl ethers such as ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, etc. Diethylene glycol monoalkyl ether, ethylene glycol monoalkyl and phenyl acetate, triethylene glycol monoalkyl ether, propylene glycol monoalkyl ether such as propylene glycol monobutyl ether, dialkyl malonate such as diethyl malonate, dipropylene such as dipropylene glycol monomethyl ether Listed are glycol monoalkyl ethers and ester compounds such as these glycol monoethers. Rukoto can.

  Among these, N-methyl-2-pyrrolidone, dimethylimidazolidinone, γ-butyrolactone, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether and the like can be particularly preferably used. .

  The alignment agent used in the present invention can contain various additives as necessary. For example, when it is desired to improve the coating property, a surfactant that meets such a purpose may be blended, and when it is desired to improve the adhesion to the substrate, a silane coupling agent or a titanium-based coupling agent may be blended.

  As a coating method in the alignment agent coating step, a spinner method, a printing method, a dipping method, a dropping method, an ink jet method and the like are generally known. These methods are similarly applicable in the present invention. Moreover, as a method of a drying process, a method of performing heat treatment in an oven or an infrared furnace, a method of performing heat treatment on a hot plate, and the like are generally known. These methods are equally applicable in the present invention. The drying step is preferably performed at a relatively low temperature within a range where the solvent can be evaporated.

  Next, a heat treatment step necessary for the dehydration / ring closure reaction and a step of orientation treatment of the obtained coating film are performed. In the steps of the heat treatment and the alignment treatment, the alignment treatment may be performed following the heat treatment, or conversely, the heat treatment may be performed after the alignment treatment. Further, the heat treatment and the alignment treatment can be performed simultaneously. These methods vary depending on the alignment treatment method, but an optimum method is appropriately applied.

  As the method for the heat treatment step, the same method as that for the drying step described above can be applied, and the heat treatment step is generally preferably performed at a temperature of about 150 to 300 ° C.

  The alignment treatment method that can be used in the present invention is a method of performing alignment treatment by irradiating light, that is, a photo-alignment method. As described above, a number of alignment mechanisms such as photolysis, photoisomerization, photodimerization, and photocrosslinking methods have been proposed for the photoalignment method, but as long as the object of the present invention is achieved. Other methods can be applied in the same manner. A photo-alignment method that can be particularly preferably used in the present invention is a method utilizing a photoisomerization reaction such as an azo group, and after irradiating a linearly polarized ultraviolet light to a polyamic acid film containing an azo group or the like in the main chain, An alignment treatment is performed by thermal imidization.

The photo-alignment treatment conditions may be any as long as the object of the present invention is achieved. As a light source used for the alignment treatment, a low-pressure mercury lamp, a high-pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, a deep UV lamp, an excimer laser, or the like can be used. In the case of the photoisomerization method, the wavelength of light used for the alignment treatment is 300 to 600 nm, more preferably 340 to 500 nm. This is because light having a wavelength of 300 nm or more hardly causes photodecomposition of the coating film, and light having a wavelength of 600 nm or less facilitates the photoisomerization reaction. Moreover, it is preferable to remove low-wavelength light using a long wavelength transmission filter or a band pass filter. Note that it is preferable to use an ultraviolet / visible continuous light source and a bandpass filter in combination, and simultaneously irradiate ultraviolet light and visible light. Light irradiation is performed from the direction perpendicular to the substrate surface with light that has been linearly polarized through a polarizing filter or polarizing prism. The amount of light used for the alignment treatment depends on the type of liquid crystal alignment agent used and the wavelength of the light source, but the higher the irradiation amount, the stronger the photoalignment treatment and the higher the alignment index Δ in the organic semiconductor on the alignment film. It is done. As a guideline, the light irradiation amount when the alignment treatment is performed using a Deep UV lamp and a 340 to 500 nm band pass filter is 50 J / cm ² or more, preferably 150 J / cm ² or more.

  During the alignment treatment, light may be irradiated to the substrate coated with the alignment agent through a photomask. In this case, only the portion necessary for the orientation can be selectively subjected to the orientation treatment.

  Any method may be used as a method for forming an organic semiconductor film used in the present invention as long as an organic semiconductor film having in-plane anisotropy can be formed on the photo-alignment film, but preferably by a solution method or a vacuum deposition method. is there. More preferred is a vacuum evaporation method.

  The solution method can be performed using a spin coating method, an inkjet method, a dipping method, a casting method, a bar coating method, or the like. Further, after film formation, heat treatment may be performed as necessary.

  The organic semiconductor compound used in the organic semiconductor element of the present invention is not particularly limited as long as it is a compound that can form in-plane anisotropy on the photo-alignment film when formed on the photo-alignment film, but has high crystallinity. A compound having high charge mobility is suitable. Examples of the organic semiconductor compound include acene, oligothiophene, 1,4 dithienyl acene, 2,6-diphenylbenzo (1,2-b: 4,5b ′) dithienophen, porphyrin, rubrene or acene, oligothiophene, 1,4 dithienyl acene. 2,6-diphenylbenzo (1,2-b: 4,5b ′) dithienophen, porphyrin, rubrene or derivatives thereof. More preferred are acene, oligothiophene, 2,6-diphenylbenzo (1,2-b: 4,5b ′) dithienophene, porphyrin, and rubrene.

As the acene that can be used in the present invention, a compound represented by the general formula (8) can be preferably used in the present invention.

In General formula (8), n is 1-5, R < ¹⁴ >, R < ¹⁵ >, R < ¹⁶ >, R < ¹⁷ > is hydrogen or a C1-C12 alkyl, alkyloxy, and alkyl ketone independently. Preferably n is 1-4 and R < ¹⁴ >, R < ¹⁵ >, R < ¹⁶ > and R < ¹⁷ > are all hydrogen. More preferably, n is 2 to 3, and R ¹⁴ , R ¹⁵ , R ¹⁶ , and R ¹⁷ are all hydrogen.

  In the present invention, 1,4-di (thienyl) acene represented by the general formula (9) can be preferably used.

一般式（９）において、ｎは０〜５であり、Ｒ^１８、およびＲ^１９は独立して、水素、炭素数が１〜２０のアルキル、アルキルオキシまたはアルキルケトンである。好ましくはＲ^１８、およびＲ^１９は炭素数が１〜１５のアルキルある。

In the general formula (9), n is 0 to 5, and R ¹⁸ and R ¹⁹ are independently hydrogen, alkyl having 1 to 20 carbons, alkyloxy, or alkyl ketone. Preferably R < ¹⁸ > and R < ¹⁹ > are C1-C15 alkyl.

  The α oligothiophene represented by the general formula (10) is a thiophene having a linear structure and can be preferably used in the present invention.

一般式（１０）において、ｎは３〜７であり、Ｒ^２０、およびＲ^２１は独立して水素、炭素数が１〜２０のアルキル、アルキルオキシまたはアルキルケトンである。好ましくはＲ^２０、およびＲ^２１は炭素数が１〜１５のアルキルある。

In General formula (10), n is 3-7, R < ²⁰ > and R < ²¹ > are hydrogen, a C1-C20 alkyl, alkyloxy, or alkyl ketone independently. Preferably R < ²⁰ > and R < ²¹ > are C1-C15 alkyl.

  2,7-diphenyl [1] benzothieno [3,2-b] [1] benzothienophene represented by the general formula (11) can be preferably used in the present invention.

一般式（１１）において、Ｒ^２２、およびＲ^２３は独立して水素、炭素数が１〜２０のアルキル、アルキルオキシまたはアルキルケトンである。好ましくはＲ^２２、およびＲ^２３は水素もしくは炭素数が１〜１５のアルキルある。

In the general formula (11), R ²² and R ²³ are independently hydrogen, alkyl having 1 to 20 carbons, alkyloxy, or alkyl ketone. Preferably, R ²² and R ²³ are hydrogen or alkyl having 1 to 15 carbons.

  The technique of manufacturing an organic semiconductor element using the photo-alignment film in the present invention can be effectively used for application applications of organic semiconductors. Examples of organic semiconductor applications include thin film semiconductor elements, RFIDs, lasers, sensors, solar cells, and diodes.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to these Examples. In addition, the name of the tetracarboxylic dianhydride, diamine, and solvent which are used by an Example and a comparative example is shown by an abbreviation. This abbreviation may be used in the following description.

Tetracarboxylic acid dianhydride pyromellitic dianhydride: PMDA
・ Diamine 4,4′-diaminoazobenzene: DAZ
・ Solvent N-methyl-2-pyrrolidone: NMP

1) Preparation of aligning agent 2.4660 g of DAZ and 30.00 g of dehydrated NMP were introduced into a 200 ml four-necked flask equipped with a thermometer, stirrer, raw material charging inlet and nitrogen gas inlet, and stirred under a dry nitrogen stream. Dissolved. While maintaining the temperature of the reaction system at 5 ° C., 2.5340 g of PMDA was added (PMDA / DAZ raw material molar ratio = 50/50), and after reacting for 30 hours, 65.00 g of dehydrated NMP was added, and 5 wt% A polyamic acid aligning agent was prepared. When the temperature rose due to heat of reaction during the reaction, the reaction was carried out at a reaction temperature of about 70 ° C. or lower. The polyamic acid obtained here had a weight average molecular weight of Mw = 24600 and a degree of dispersion in MNP of 2.9.

2) Application of aligning agent After the aligning agent was diluted with NMP to 1.60% by weight, a silicon wafer substrate (low-doped n-type with dry thermal oxide film 300 nm, Si (100), resistivity: 5-10 The coating was applied with a spinner. The coating conditions were 3000 rpm and 60 seconds.

3) Photo-alignment treatment and baking After coating, the light that was converted into linearly polarized light through a Grand Taylor polarization prism using a 500 W Deep UV lamp (UXM-501MD) manufactured by Ushio Inc. as a light source from time 0 min. Irradiated for 120 minutes. Thereafter, the alignment film was baked by performing a heat treatment at 250 ° C. for 120 minutes in a nitrogen atmosphere. The photo-alignment treatment conditions were a wavelength region of 340 to 500 nm using a bandpass filter manufactured by Asahi Spectroscopic Co., Ltd., and the irradiation light intensity was 88 mW.

4) Measurement of film thickness Automatic polarization analyzer (APE-100) manufactured by Shimadzu Corporation was used to determine the film thickness of the alignment film produced on the quartz glass substrate under exactly the same conditions except that optical alignment treatment was not performed. ) And a measurement wavelength of 632.8 nm (He—Ne laser) at an incident angle of 62.5 degrees, it was 11 nm.

5) Calculation of orientation index Δ The infrared absorption spectrum of the obtained alignment film was measured using an FT-IR apparatus (spectrometer: Mattson Galaxy 3020, detector: mercury cadmium telluride) at a measurement temperature of 29 ° C. and a total of 400 times. It measured on condition of this. Infrared light transmitted through the polarizer was irradiated from the direction perpendicular to the substrate surface of the alignment film. The infrared light spectrum was measured when the alignment treatment direction of the sample and the polarization direction were measured in parallel, and the infrared light spectrum when measured in the vertical direction. In the case of an alignment film, the integrated intensity of absorption having a peak in the vicinity of 1370 cm ⁻¹ (baseline 1321 to 1445 cm ⁻¹ ) attributed to stretching vibration of (CO) ₂ NC bond is used, and the difference in absorbance of the alignment film (A ⊥−A‖) and the sum of the absorbance of the alignment film (A⊥ + A‖) were calculated. On the other hand, in the case of pentacene, the difference in absorbance (A⊥-A‖) using the integrated intensity (baseline 947 to 968 cm ^-1 ) of absorption having a peak in the vicinity of 955 which is the out-of-plane vibration of CH and the alignment film The sum of absorbance (A⊥ + A‖) was calculated. Next, the orientation index Δ was calculated from the values of (A⊥−A‖) and (A⊥ + A‖) obtained according to the formula (1). (Figures 1 and 2)

6) Vapor Deposition of Pentacene Film Using pentacene (purchased from Aldrich) as the organic semiconductor material, a thickness of the substrate on the polyimide photo-alignment film is measured by vacuum deposition at a substrate temperature of room temperature, a deposition rate of 0.3 nm / min, and a pressure of 10 ⁻⁵ Pa. A 30 nm pentacene thin film was formed by vacuum evaporation.

7) X-ray diffraction of the pentacene vapor deposition film was performed using Rigaku Ultima III (FIG. 2).
The X-ray diffraction data shows that the pentacene thin film is a thin film phase crystal whose molecular long axis is oriented perpendicularly to the alignment film as an average. Furthermore, an improvement in the diffraction intensity of pentacene is observed by the photo-alignment treatment, and an improvement in crystallinity can be confirmed.

8) Form of pentacene vapor deposition film surface (Fig. 3)
AFM (JEOL JSPM-5200) was used. On the photo-alignment film, it was confirmed that the crystal grains of pentacene were larger than those without light treatment.

9) Relationship between the orientation index Δ at 1370 cm ⁻¹ of the orientation film and the UV exposure amount in the photo-alignment treatment (FIG. 4)
With the photo-alignment treatment time, the orientation index Δ of the alignment film increases rapidly, and a tendency to saturate at about 320 J / cm ² is observed.

10) Relationship between the orientation index Δ at 955 cm ⁻¹ of the pentacene film and the UV exposure amount in the photo-alignment treatment (FIG. 4).
An increase in the orientation index of the alignment film and an increase in the orientation index of the pentacene molecule are almost correlated. When the UV exposure is less than 25 J / cm ^{2, the} molecular orientation is parallel to the average molecular orientation direction of the polyimide molecules (perpendicular to the polarization direction) as the average of pentacene. When the exposure dose is at least / cm ^2, an arrangement of pentacene molecules occurs such that the molecular plane of pentacene is perpendicular to the average molecular orientation direction (perpendicular to the polarization direction) of the polyimide molecules.

11) Manufacture of an organic semiconductor element A highly doped n-type silicon wafer (Si (100), resistivity 0.01 to 0.0180 ohm cm) with a dry thermal oxide film (300 nm) is used as a substrate, as described in Example 1. After forming a photo-alignment film with a UV exposure amount of 320 J / cm ² , a pentacene film (thickness: 30 nm) under the conditions of temperature (room temperature), vapor deposition rate 0.3 nm / min, and pressure 10 ⁻⁵ Pa by a vacuum vapor deposition method. Formed. Thereafter, a comb electrode was prepared by vapor deposition using a comb electrode mask (FIG. 5), and a top contact type TFT device was manufactured. The channel length is L = 0.08 mm, the channel width is 140 mm, and the electrode Au thickness is 10 nm.

12) Characteristic evaluation of TFT The characteristic of the said TFT was measured using two 487 picometer / voltage source units by Keithley.
The gate voltage (V _g ) was changed by 5 V between 10 V and −30 V, and the source-drain voltage (V _d ) -current (I _d ) characteristics were measured to confirm the FET characteristics (the upper diagram in FIG. 6). . The, _V g -I _d characteristics of the time of V _d = -30 V shown in FIG. 6 below.
The carrier mobility determined from the relational expression I _d = W / 2L [μC _i (V _g −V _T ) ² ] of the saturation region is that the average molecular arrangement direction of the pentacene molecular plane is relative to the source-drain electrode direction. When vertical, μ⊥ = 1.94 × 10 ⁻³ cm ² v ⁻¹ s ⁻¹ , and when the average molecular arrangement direction of the pentacene molecular plane is parallel to the source-drain electrode direction, μ‖ = 9 The effect of controlling the in-plane anisotropy of the pentacene molecule was confirmed at 6 × 10 ⁻⁴ cm ² v ⁻¹ s ⁻¹ .

  By using the organic semiconductor element of the present invention, the organic semiconductor element can be easily formed at low cost. Furthermore, since the semiconductor characteristics are very excellent, the organic semiconductor element of the present invention has excellent electronic characteristics and can be suitably used in the field of electronics and the like.

The graph which shows the infrared absorption spectrum (upper) of an orientation film, and the infrared absorption spectrum of a pentacene vapor deposition film (lower). The graph which shows XRD of a pentacene vapor deposition film. AMF photograph of a pentacene deposited film. Graph showing the orientation index of the alignment film (top) and graph showing the orientation index of the pentacene deposited film (bottom) The schematic diagram which shows a comb-tooth electrode. Graph showing TFT element characteristics (upper: relationship between Vd and Id, lower: relationship between Vg and Id1 ^{/ 2} )

Claims (5)

An organic semiconductor element including a photo-alignment film and an organic semiconductor film. The photo-alignment film is a polyimide that has been subjected to a heat treatment after an alignment process by light irradiation, and the organic semiconductor film is a vacuum on the photo-alignment film. An organic semiconductor element formed by vapor deposition and having in-plane anisotropy on the photo-alignment film,
The optical alignment film is subjected to alignment treatment by light irradiation, so that the absolute value | Δ | of the alignment index of the alignment film represented by formula (1) is 0.2 ≦ | Δ | ≦ 0. 8 is an organic semiconductor element.

In the formula, A‖ is the absorbance due to the characteristic group vibration when infrared light having a polarization component parallel to the alignment treatment direction is incident on the alignment film, and A⊥ is a red light having a polarization component perpendicular to the alignment treatment direction. This is the absorbance due to the characteristic group vibration of the alignment film when external light is incident on the alignment film. The organic semiconductor element according to claim 1, wherein the alignment treatment is an alignment treatment using a photoisomerization reaction of an azo group. The alignment treatment is a radiation of linearly polarized ultraviolet light to the polyamic acid film, wherein the heat treatment, the organic semiconductor device according to claim 1, wherein the thermal imidization. The said organic-semiconductor film contains the organic-semiconductor compound which can form in-plane anisotropy by forming into a film on a photo-alignment film, The any one of Claims 1-3 characterized by the above-mentioned. Organic semiconductor element. The organic semiconductor compound is at least selected from the group consisting of acene, oligothiophene, dithienyl acene, 2,7-diphenyl [1] benzothieno [3,2-b] [1] benzothienophen, porphyrin, rubrene or derivatives thereof. The organic semiconductor element according to claim 4, which is one type.

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