JP2006269770A - Organic oriented film and organic semiconductor device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic oriented film having superior orientation, capable of indicating high mobility. <P>SOLUTION: A carrier effective mass (m<SP>*</SP>) satisfies 0<m<SP>*</SP>≤0.8m<SB>e</SB>(where m<SB>e</SB>represents the original mass of the electrons). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic alignment film having excellent alignment that can exhibit high mobility, and an organic semiconductor device using the organic alignment film.

  In recent years, organic materials have been widely used for electronic devices, and some of them have been put into practical use. In the field-effect transistor (hereinafter abbreviated as “FET” as appropriate), inorganic materials have been used in the past. However, diversification of device forms (such as providing flexibility), For the purpose of increasing the area and reducing the cost, attempts have been made to use organic materials, and research continues.

Conventionally, a thin film transistor using an organic material (thin film transistor: hereinafter abbreviated as “TFT” where appropriate. Also, a TFT using an organic material is appropriately referred to as “organic TFT”) is realized by using crystals. However, in a system using a crystal, the mobility is low (about 0.1 to 0.5 cm ² / Vs in a pentacene crystal, although it is not patented). Reference 1) has a problem that it remains at a level that is insufficient for practical use.

On the other hand, in recent years, it has been reported that even in a system using a thin film, the mobility is almost equal to or higher than that of a crystal despite the existence of a grain boundary derived from the use of the thin film (in a pentacene thin film). R & D aiming at practical use using a thin film has been widely conducted in conjunction with 0.7 cm ² / Vs, Non-Patent Document 2) and the ease of film formation. Recently, an example of a thin film that has exhibited higher mobility by performing various devices has been reported (3.0 cm ² / Vs in a pentacene thin film, Non-Patent Document 3). However, even these thin films have a lower mobility than inorganic materials, and even if they are intended for limited applications, they are inadequate for practical use.

J. Takeya et al., Journal of Applied Physics, Vol. 94, No. 9, p. 5800-5804, 2003 D. J. Gundlach et al., IEEE Electron Device Letters, Vol. 18, No. 3, p. 87-89, 1997 H. Klauk et al., Journal of Applied Physics, Vol. 92, No. 9, p. 5259-5263, 2002

  From the above background, it has been required to elucidate the factors governing mobility in a thin film using an organic material and to develop a thin film having an excellent orientation capable of exhibiting high mobility.

  The present invention was devised in view of the above-mentioned problems, and the object thereof is high by providing an organic alignment film having excellent alignment that can exhibit high mobility, and by using this organic alignment film. The object is to provide an excellent organic semiconductor device exhibiting mobility.

  In view of such a problem, the present inventors made a thin film with uniform orientation, performed orientation structure analysis and thin film physical property evaluation, and further theoretically analyzed the difference between the crystal and the thin film. The reason for the difference in degree was clarified. In addition, based on the idea that one of the factors governing mobility is the effective carrier mass, and the mobility increases as the carrier effective mass decreases, further theoretical calculations, analysis, and considerations were performed. As a result, an orientation with a small effective carrier mass, which is considered to have higher mobility in the thin film, was found, and the present invention was completed.

That is, the gist of the present invention, the carrier effective mass (m ^*) is, 0 <m ^* satisfy ≦ 0.8 m _e (where, m _e is. Representing the electronic original mass) be characterized, organic It exists in the alignment film (claim 1).

  Here, it is preferable that the angle (φ) formed between the least square planes of each molecule between the two closest molecules in the unit cell constituting the thin film structure satisfies 0 ≦ φ ≦ 80 ° (Claim 2).

  Further, it preferably comprises an acene compound (claim 3).

  Furthermore, it preferably comprises a pentacene-based compound (claim 4).

  In this case, the lattice constants are a = 7.5 ± 1Å, b = 6.0 ± 1Å, c = 15.4 ± 1Å, α = 90.0 ± 10 °, β = 90.0 ± 10 °, γ = 91.0 ± 10 ° is preferable within each range (Claim 5).

  Further, in the parallel optical system X-ray diffraction out-of-plane measurement (thin film measurement), each range of Bragg angle 2θ = 5.8 ± 0.5 ° and Bragg angle 2θ = 11.5 ± 0.5 ° In the parallel optical system X-ray diffraction in-plane measurement (thin film measurement), the Bragg angle 2θ = 19.1 ± 0.5 ° and the Bragg angle 2θ = 23.7 ± 0.5 ° And a Bragg angle 2θ = 28.1 ± 0.5 °, preferably having a peak in each range (Claim 6).

  Further, another gist of the present invention resides in an organic semiconductor device characterized by using the above-mentioned organic alignment film (claim 7).

  The organic alignment film of the present invention has an excellent alignment that has a small effective carrier mass and can exhibit high mobility. Therefore, it can be suitably used for an organic semiconductor device such as an organic TFT.

  Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the invention.

  In the present specification, “thin film” means a state in which molecules (or atoms) are in a film state in a situation where the constituent molecules (or atoms) are affected by the surface, and “crystal” mainly refers to A state in which molecules (or atoms) are arranged with a three-dimensional periodicity by interaction between constituent molecules (or atoms).

[I. Characteristics of organic alignment film]
The organic alignment film of the present invention has the following characteristics.

[I-1. Features regarding effective carrier mass)
・ Range of effective carrier mass:
Organic alignment film of the present invention, the carrier effective mass value (m ^*) is usually greater than 0, and usually 0.8 m _e, preferably less 0.6 m _e, more preferably less 0.4 m _e Range. However, m _e represents the electronic original mass.

・ Definition of effective carrier mass:
In this specification, “carrier” is an electron or a hole.
Note that in this specification, “electrons” and “holes” refer to electrons and holes in a state affected by a field in a thin film or crystal, respectively.
Further, in this specification, “carrier effective mass” (m ^* ) refers to an effective mass obtained from the curvature of a band structure calculated.

  Various methods are known for calculating the band structure. In this specification, the band structure is obtained by the plane wave expansion method, and the effective mass is obtained from the curvature. Specifically, it calculates | requires according to the procedure of following (i)-(v).

(I) Khon Sham's equation (W. Kohn et al., Physical Review, Vol. 140, No. 4A) based on the structure in which periodic boundary conditions are applied to the constituent atoms and molecules of the unit cell of the material. , P.A1133-A1138, 1965), and calculate the electron density by density functional theory.
In this case, as an exchange correlation functional, PW91 (JP Perdew et al., Physical Review B, Vol. 45, No. 23, p. 13244-13249, 1992, JP Perdew) et al., Physical Review B, Vol. 46, No. 11, p. 6671-6687, 1992) and Norm-conserving pseudopotential (DR Hamann, Physical Review B, Vol. 40, No. 5). , P.2980-2987, 1989).

(Ii) Based on the obtained electron density, the energy eigenvalue was calculated by plane wave expansion method (C. Kittel, “Introduction to solid state physics”, 8th edition, published by Wiley, 2005, p.161-184). The band structure of the material is calculated by the method to obtain the band structure.

の各成分ｋ_x、ｋ_y、ｋ_zで２階微分した値から右辺のテンソルをつくり、これを対角化して、この固有値を求め、その逆数をとることによって、電子の有効質量ｍ^*を求める。

(Iii) Pay attention to the band structure drawn on the reciprocal space, and find the place where the band energy is minimal in the conduction band above the Fermi surface. In general, there are a plurality of these, but two points are selected, that is, the place where the minimum value is the smallest and the place where the second smallest place is located. At these points, according to the right side of the following formula (1), the band energy ε is expressed as a wave vector representing the state.

The right-side tensor is created from the values obtained by second-order differentiation with respect to each component k _x , k _y , and k _z , and this is diagonalized to obtain this eigenvalue, and by taking its reciprocal, the effective electron mass m ^* is obtained. Ask.

の各成分で２階微分した値からテンソルをつくるが、価電子バンドの場合キャリアは電子ではなく正孔すなわちホールであるので、式（２）の場合は式（１）に対して右辺の符号を反転させる。この符号を反転した右辺のテンソルを対角化して固有値を求め、その逆数をとることによって、正孔の有効質量ｍ^*を求める。

(Iv) In the valence band below the Fermi surface, find a place where the band energy has a maximum value. In general, there are a plurality of these, but two points are selected, that is, a place where the maximum value is the largest and a place where the second largest value is found. At these points, according to the right side of the following equation (2), the band energy ε is expressed as a wave vector.

In the case of the valence band, the carrier is not an electron but a hole, that is, a hole. Therefore, in the case of Equation (2), the sign on the right side of Equation (1) is used. Is reversed. The effective value m ^{* of the} hole is obtained by diagonalizing the tensor on the right side with the sign inverted and obtaining the eigenvalue and taking the reciprocal thereof.

である。ここで、ｈはプランク定数を表わす。 In the above equations (1) and (2),

It is. Here, h represents a Planck constant.

(V) There are a plurality of eigenvalues obtained in the above (iii) and (iv), and there are a plurality of effective masses m ^* obtained. However, the effective mass of electrons is the positive value of m ^* in the result of (iii). The effective value of holes is the positive value with the smallest positive value among m ^* in the result of (iv).

  However, when considering application as a thin film device, the effective mass in the direction parallel to the substrate, that is, the in-plane direction of the thin film is considered to be significant. The component in the direction perpendicular to the surface is not considered.

・ Relationship between effective carrier mass and mobility:
The reason why high carrier mobility can be obtained by setting the effective carrier mass (m ^* ) of the organic alignment film within the above range is presumed as follows.

ここで、ｅは電子の電荷であり、τは運動しているキャリアの緩和時間であり、一般に有効質量ｍ^*と絶対温度Ｔに依存する。 There is a relationship expressed by the following formula (3) between the mobility μ and the effective mass m ^* (Ryuzo Abe, New Physics Series 8, “Electric conduction”, Baifukan, 20th printing, 1991 ( (First edition 1969), 1-6, p.11).

Here, e is the charge of the electrons, τ is the relaxation time of the moving carriers, and generally depends on the effective mass m ^* and the absolute temperature T.

ここで、ｌ₀は平均自由行程、ｖ_tは絶対温度Ｔにおける熱運動速度、ｋはボルツマン定数である。 By the way, the relationship represented by the following formulas (4) and (5) is also established (see W. Warta et al., Physical Review B, Vol. 32, No. 2, p. 1172-1182, 1985).

Here, l ₀ is the mean free path, v _t is the thermal motion speed at the absolute temperature T, and k is the Boltzmann constant.

By substituting equation (5) into equation (4) and further substituting equation (4) into equation (3), the mobility is expressed by the following equation (6).

In the equation (6), if the temperature is considered to be fixed and it is assumed that l ₀ does not change greatly, μ is inversely proportional to (m ^* ) ^1/2 .
Therefore, it is considered that the mobility increases as the effective mass decreases.

[I-2. (Features related to orientation structure)
・ Range of angle between two molecules:
In the organic alignment film of the present invention, the angle (φ) formed between the least square planes of each molecule between the two closest molecules in the unit cell constituting the thin film structure is usually 0 ° ≦ φ ≦ 80 °, especially 0 °. ≦ φ ≦ 60 °, more preferably in the range of 0 ° ≦ φ ≦ 50 °. In the present specification, the “angle formed between the least square planes of each molecule between the two closest molecules in the unit cell” is appropriately referred to as “the angle formed between the two molecules”.

・ Definition of angle between two molecules and rotation angle:
In the present specification, the “angle between two molecules” (φ) of the thin film structure of the organic alignment film or the crystal structure of a single crystal specifically refers to a value defined as follows.

  That is, the two molecules A and B closest to each other in the unit cell are considered, and the least square plane of each of the molecules A and B is defined as a molecular plane a and a molecular plane b. Here, the angle formed between the molecular surface a and the molecular surface b is defined as “angle formed between two molecules” φ.

  Next, the rotation axis of the molecule A is selected so that it passes through the center of gravity of the molecule A, is on the molecular surface a, is parallel to the molecular surface a, and is also parallel to the molecular surface b. Then, as shown in FIG. 1, for each of the two molecules A and B, when the molecular plane a and the molecular plane b are vertical, the molecule A is rotated about its rotation axis by θ, before the rotation. The angle between the molecular plane a perpendicular to the molecular plane b and the rotated molecular plane a is defined as “rotation angle” θ. At this time, the relationship between θ and φ is expressed as φ = 90 ° −θ.

  The “angle between two molecules” (φ) employs the smaller of the two complementary angles, and is defined to always be in the range of 0 ° ≦ φ ≦ 90 °. For example, even when the molecule A is rotated in the direction opposite to the direction shown in FIG. 1, the angle that is the inner angle of the triangle is adopted, and φ is always determined to be 90 ° or less.

・ Relationship between angle between two molecules and mobility:
The reason why the high carrier mobility can be obtained by setting the angle (φ) between the two molecules of the organic alignment film within the above range is presumed as follows.

  That is, when the molecular orbitals are spread on the molecular plane defined above, as shown in FIG. 2, the molecular planes are perpendicular to each other (the state shown in FIG. 2 (a)) and almost parallel (FIG. 2). (The state shown in (b)), that is, as θ increases and φ decreases, the interaction between orbits increases, so the difference between the new two levels caused by the bimolecular interaction increases. . Such an infinitely repeated interaction between molecules can be considered as a solid, and the new level generated by the interaction becomes a continuous band. As can be seen from the interaction between molecules, when the overlap between orbits is large in a solid, the bandwidth is widened. At this time, if the band edge (upper or lower end of each band) can be approximated by a quadric surface, it can be said that the curvature increases as the band width increases. Here, as can be seen from the above-described effective mass equations (1) and (2), the carrier at the band edge is apparently lighter. Therefore, it is considered that the mobility increases from the relationship between the carrier effective mass and the mobility described above. Conversely, as the bandwidth becomes narrower, the carrier becomes heavier. Therefore, it is considered that the mobility is lowered from the relationship between the carrier effective mass and the mobility described above.

[I-3. Features regarding X-ray diffraction]
As described later, the organic alignment film of the present invention is preferably produced using a pentacene compound (pentacene and / or a derivative thereof) as a raw material. This is hereinafter referred to as “the pentacene thin film of the present invention” as appropriate.
The pentacene thin film of the present invention has the following characteristics in X-ray diffraction measurement.

・ Lattice constant:
The pentacene thin film of the present invention preferably has a lattice constant in the following range.

That is, the value of a should be in the range of 7.5 ± 1 cm, specifically in the range of usually 6.5 mm or more, especially 7.0 mm or more, and usually 8.5 mm or less, especially 8.0 mm or less. Is preferred.
In addition, the value of b should be in the range of 6.0 ± 1 、, specifically, usually 5.0Å or more, especially 5.5Å or more, and usually 7.0 通常 or less, especially 6.5 、 or less. Is preferred.
In addition, the value of c should be in the range of 15.4 ± 1 mm, specifically, 14.4 mm or more, especially 14.9 mm or more, and usually 16.4 mm or less, especially 15.9 mm or less. Is preferred.

The value of α is in the range of 90.0 ± 10 °, specifically, usually 80.0 ° or more, especially 85.0 ° or more, and usually 100.0 ° or less, especially 95.0 ° or less. It is preferable that it is the range of these.
Further, the value of β is in the range of 90.0 ± 10 °, specifically, usually 80.0 ° or more, especially 85.0 ° or more, and usually 100.0 ° or less, especially 95.0 ° or less. It is preferable that it is the range of these.
Further, the value of γ is in the range of 91.0 ± 10 °, specifically, usually 81.0 ° or more, especially 86.0 ° or more, and usually 101.0 ° or less, especially 96.0 ° or less. It is preferable that it is the range of these.

  A pentacene thin film having a lattice constant within the above range is preferable because the thin film structure itself is a governing factor of mobility.

X-ray diffraction peak:
The pentacene thin film of the present invention preferably has a peak in each of the following regions in parallel optical system X-ray diffraction out-of-plane measurement (thin film measurement).
A region where the Bragg angle 2θ is 5.8 ± 0.5 °. Specifically, the region where 2θ is usually 5.3 ° or more, preferably 5.5 ° or more, and usually 6.3 ° or less, preferably 6.1 ° or less.
A region where the Bragg angle 2θ = 11.5 ± 0.5 °. Specifically, the region where 2θ is usually 11.0 ° or more, preferably 11.2 ° or more, and usually 12.0 ° or less, preferably 11.8 ° or less.

The pentacene thin film of the present invention preferably has a peak in each of the following regions in parallel optical system X-ray diffraction in-plane measurement (thin film measurement).
A region where the Bragg angle 2θ = 19.1 ± 0.5 °. Specifically, the region where 2θ is usually 18.6 ° or more, preferably 18.8 ° or more, and usually 19.6 ° or less, preferably 19.4 ° or less.
A region where the Bragg angle 2θ = 23.7 ± 0.5 °. Specifically, the region where 2θ is usually 23.2 ° or more, preferably 23.4 ° or more, and usually 24.2 ° or less, preferably 24.0 ° or less.
A region where the Bragg angle 2θ = 28.1 ± 0.5 °. Specifically, a region where 2θ is usually 27.6 ° or more, preferably 27.8 ° or more, and usually 28.6 ° or less, preferably 28.4 ° or less.

  A pentacene thin film having a peak in the above range in parallel optical system X-ray diffraction out-of-plane measurement and in-plane measurement is preferable because the thin film structure itself is the controlling factor of mobility.

-X-ray diffraction measurement method, lattice constant determination method:
In the present invention, parallel optical system X-ray diffraction out-of-plane measurement and in-plane measurement of a pentacene thin film can be performed under the following conditions.

  Various known X-ray diffraction measurement devices can be used as the measurement device. As a specific example, there is Rigaku RINT200PC (in-plane gonio mounted) used in the column of [Example 1] described later.

As the measurement conditions, the conditions described below are preferable.
<Out-of-plane measurement>
・ X-ray source: CuKα
・ Scanning axis: 2θ
-Incident angle (θ): 1.0 °
-Scanning range (2θ): 3.0 ° or more <In-plane measurement>
・ X-ray source: CuKα
・ Scanning axis: φ / 2θχ
-Incident angle θ: 1.0 °
・ Fixed angle 2θ: 1.0 °
-Scanning range (2θχ): 3.0 ° or more

  The lattice constant of the pentacene thin film is determined with reference to known single crystal structures in various polymorphs based on the X-ray diffraction patterns obtained by in-plane measurement and out-of-plane measurement.

[I-4. Absorption spectrum)
The organic alignment film of the present invention is usually 1.80 eV or more, especially 1.82 eV or more, more preferably 1.83 eV or more, usually 1.90 eV or less, especially 1.88 eV or less, when absorption spectrum measurement is performed. It is preferable that a clear peak with the largest intensity appears in the range of 1.87 eV or less. Moreover, it is preferable that a peak also appears in the range of usually 2.07 eV or more, particularly 2.09 eV or more, further 2.10 eV or more, usually 2.17 eV or less, particularly 2.15 eV or less, and further 2.14 eV or less. .

  Moreover, the organic alignment film of the present invention is converted to s-polarized light in the region of 1.3 eV to 1.8 eV in the absorption spectrum for polarized incident light from an oblique direction with respect to the film when the polarization absorption spectrum is measured. On the other hand, it is preferable that the absorption in the corresponding region is weak in p-polarized light, and that the ratio of (absorption intensity for s-polarized light) / (absorption intensity for p-polarized light) is larger. preferable.

[II. Manufacturing method of organic alignment film]
The method for producing the organic alignment film of the present invention will be described below with reference to preferred examples. However, the manufacturing method of the organic alignment film of the present invention is not limited to the following examples.

[II-1. material〕
The compound used as the raw material for the organic alignment film of the present invention is not particularly limited, and various organic compounds known for their properties as semiconductor materials can be used. From the viewpoint of achieving, a condensed polycyclic aromatic hydrocarbon compound is preferred.

The condensed polycyclic aromatic hydrocarbon compound may be either a cata-condensed ring compound or a peri-condensed compound, but is preferably a cata-condensed ring compound.
The catacyclic ring compound may be an acene compound having a linear condensed ring system or a phenic compound having a bent condensed ring system, but an acene compound is preferable.

・ Acene compounds:
In the present specification, the “acene compound” refers to a compound selected from the group consisting of a compound represented by the following general formula (A) (hereinafter abbreviated as “acene” as appropriate) or a derivative thereof.

上記一般式（Ａ）中、ｎは、通常１以上、好ましくは２以上、更に好ましくは３以上、また、通常７以下、好ましくは６以下、更に好ましくは５以下の整数を表わす。

In the general formula (A), n represents an integer of usually 1 or more, preferably 2 or more, more preferably 3 or more, and usually 7 or less, preferably 6 or less, more preferably 5 or less.

Examples of the acene derivative include a compound in which one or two or more substituents are bonded to the acene of the general formula (A).
The types of substituents include halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), nitro groups, cyano groups, carboxyl groups, carbonyloxy groups, acyl groups, amino groups, hydroxyl groups, thiol groups, monovalent organic groups. Etc.

Examples of the monovalent organic group include an alkyl group having 1 to 20 carbon atoms, an alkenyl group, and an alkynyl group; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 4 to 30 carbon atoms; Alkynyl group, alkoxy group having aryl group or aryloxy group; alkyl group, alkenyl group, alkynyl group, alkylthio group having aryl group or arylthio group; carbox having the above alkyl group, alkenyl group, alkynyl group, aryl group Acid ester group; sulfonic acid ester group having the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group; primary to tertiary substituted silyl group substituted by the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group; Substituted by the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group The like primary-tertiary-substituted amino group. In the case of an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, an alkynyl group, or a group containing these aliphatic hydrocarbon groups in the structure, the aliphatic hydrocarbon group is linear, branched, It may have any annular structure.
Any two or more of these organic groups may be bonded to each other to form a ring.

  In addition, these organic groups may be further substituted with another substituent. The type of the substituent is not particularly limited as long as it does not depart from the gist of the present invention. Examples include halogen atom; nitro group; cyano group; sulfonic acid group; carbonyloxy group; carboxyl group; amino group; An alkynyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, a carboxylic acid ester group, a sulfonic acid ester group, an alkyl and / or aryl-substituted silyl group, an alkyl and / or Aryl-substituted amino group; amide group and the like. When the substituent is an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, or an alkynyl group, or a group containing these aliphatic hydrocarbon groups in the structure, the aliphatic hydrocarbon group is a straight chain It may have any structure of a shape, a branch shape, and a ring shape.

  In addition, when it has the above-mentioned further substituent, carbon number of these organic groups is the value of the whole organic group also including the substituent, and is 30 or less normally, Preferably it is the range of 20 or less.

  The number of substituents possessed by the acene compound is not particularly limited, and may be 0, 1 or 2 or more. When the acene compound has two or more substituents, these substituents may be the same or different.

・ Pentacene compounds:
Among the acene compounds described above, particularly from the viewpoint of suppressing the effective carrier mass and achieving higher carrier mobility, the compound represented by the following general formula (B), that is, selected from the group consisting of pentacene or derivatives thereof (Hereinafter, abbreviated as “pentacene-based compound” where appropriate).

In the general formula (B), R ^{1 to} R ¹⁴ each independently represents a hydrogen atom or a monovalent substituent. The kind of the monovalent substituent is not particularly limited, but the substituents exemplified above for the acene compound, that is, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), nitro group, cyano group, carboxyl group, carbonyl Examples thereof include an oxy group, an acyl group, an amino group, a hydroxyl group, a thiol group, and a monovalent organic group. Specific examples of the monovalent organic group are the same as those exemplified above for the acene compound. The kind of substituent that the organic group may further have and the number of carbon atoms of the organic group are the same as those described above for the acene compound. Further, when R ^{1 to} R ¹⁴ are substituents, any two or more may be bonded to each other to form a ring, as described above for the acene compound.

・ Specific examples of acene compounds:
Specific examples of preferred acene-based compounds as the raw material for the organic alignment film of the present invention include compounds represented by the following formulas (C-1) to (C-6). However, the raw material of the organic alignment film of the present invention is not limited to these compounds.

上に挙げた具体例の中でも、式（Ｃ−１）で表わされるペンタセンが特に好ましい。

Among the specific examples given above, pentacene represented by the formula (C-1) is particularly preferable.

Specific examples of other condensed polycyclic aromatic hydrocarbon compounds:
Among the compounds that can be used as the raw material for the organic alignment film of the present invention, examples of condensed polycyclic aromatic hydrocarbon compounds other than acene compounds (for example, phen compounds and peri-fused compounds) include perylene and its Derivatives: Pyrene and derivatives thereof: Terylene and derivatives thereof: Catalylene and derivatives thereof.

Specific examples thereof include compounds represented by the following formulas (D-1) to (D-8).

In the above formulas (D-5) to (D-8), A each independently represents an oxygen atom or a group represented by N—R (wherein R is independently a hydrogen atom or It represents an arbitrary substituent, and examples of the substituent include the same substituents as those described as R ^{1 to} R ¹⁴ in the above formula (B).

Specific examples of compounds other than condensed polycyclic aromatic hydrocarbon compounds:
Among the compounds that can be used as the raw material for the organic alignment film of the present invention, examples of the compounds other than the condensed polycyclic aromatic hydrocarbon compound include oligothiophene and derivatives thereof; oligophenylene and derivatives thereof; (thiophene / phenylene) copolymer. oligomer (BP1T represented by the following chemical formula, BP2T, BP3T etc.) and derivatives thereof; phthalocyanine (copper phthalocyanine (CuPc), etc.) and their derivatives; fullerene (C _60, C _72, etc.) and derivatives thereof, and the like.

・ Combination of raw material compounds:
As the raw material for the organic alignment film of the present invention, any one of the various compounds exemplified above may be used alone, or two or more may be used in any combination and in any ratio. However, as described above, at least one of the raw materials is preferably an acene compound, and all of the raw materials are more preferably an acene compound.

・ Synthesis and acquisition of raw material compounds:
The various compounds exemplified above as raw materials for the organic alignment film of the present invention can be synthesized by known methods. Moreover, you may use about the thing for which synthetic products are available on the market etc.

  For example, among the acene compounds described above, anthracene, tetracene, and pentacene are easily available as reagents (for example, manufactured by Aldrich). Hexacene is described in, for example, RG Harvey, “Polycyclic Aromatic Hydrocarbons”, published by Wiley-VCH, 1997, p.193-195. These can be obtained by the synthesis methods.

・ Purification method of raw material compounds:
In the production of the organic alignment film of the present invention, it is preferable to use a high-purity raw material compound. Therefore, the acene-based compound synthesized or obtained by the above-described method is used after purification and purification. It is preferable.

  The purification method is not particularly limited, and preferred methods include a sublimation purification method, a zone purification method, and a plate sublimation method. The specific procedure is not particularly limited and may be performed according to a conventional method. For example, in the case of sublimation purification method, OD Jurchescu et al., Applied Physics Letters, Vol.84, No.16, p.3061-3063, Examples include vacuum sublimation under a temperature gradient described in 2004.

·Additive:
In addition, as needed, it is also possible to add another material as an additive in order to control the performance of a raw material compound. For example, the contact resistance with the metal electrode can be reduced by adding FeCl ₃ , or the n-type semiconductor characteristics can be obtained by adding Ca.

[II-2. Film formation]
The organic alignment film of the present invention is manufactured by forming a film using the above-described raw materials. The method of film formation is not particularly limited, but normally, a method (evaporation method) of forming a film by heating, vaporizing and evaporating the raw material compound and depositing it on the substrate is suitably used.

  Hereinafter, the details of the vapor deposition method will be described by taking as an example the case of using the above-described acene-based compound as a raw material compound. However, the film formation conditions for producing the organic alignment film of the present invention are not limited to the following conditions.

·substrate:
The material of the substrate surface on which the raw material compound is formed is not particularly limited, and may be selected according to the intended use of the organic alignment film. Inorganic materials include silicon compounds (silicon oxide, silicon nitride, silicon oxynitride, etc.), metal oxides (aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, lanthanum oxide, hafnium oxide, etc.), ferroelectrics ( And barium zirconate titanate, lead zirconate titanate, etc.). Examples of the organic material include polymer materials (polyvinylphenol, polyvinyl alcohol, polyimide, polyacrylonitrile, parylene, polymethyl methacrylate, cyanoethyl pullulan, polyvinylidene fluoride, polystyrene, or a compound using them). Of these, silicon oxide, aluminum oxide, and polyvinylphenol are preferable.

The film-forming surface on the substrate surface is preferably flat, and the surface roughness is usually 2 nm RMS or less, preferably 0.5 nm RMS or less.
Further, the shape, thickness and size of the substrate are arbitrary.

・ Surface modification:
In addition, it is preferable to perform surface modification in order to optimize the surface energy of the substrate surface before vapor deposition of the raw material compound. The surface modification procedure is not particularly limited, but it is usually performed by bringing a surface modifier such as a silane coupling agent into contact with the substrate surface.

  Examples of surface modifiers include octadecyltrichlorosilane, hexamethyldisilazane, polyalphamethylstyrene, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3 , 4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ -Methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β- (aminoethyl) γ-aminopro Rutrimethoxysilane, N-β- (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl-aminopropyltrimethoxysilane , Γ-chloropropylmethoxysilane, γ-mercaptopropyltrimethoxysilane, 3-trihydroxysilylmethylphosphonate sodium salt, nitroclotris (methylene) triphosphonic acid, tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphite, diethylphosphate ethyl Triethoxysilane or the like is preferable.

  As an example of the surface modification procedure, an example of a method of modifying the surface of silicon oxide using octadecyltrichlorosilane will be described. Hexadecane is used as a solvent, and the substrate before the organic alignment film deposition is immersed in a 2% by weight solution of octadecyltrichlorosilane. The environmental conditions at this time are preferably in a range of room temperature to 200 ° C. in an anhydrous atmosphere, and the pressure is preferably atmospheric pressure. The immersion time is usually preferably in the range of 1 minute to 4 hours. After immersion, the substrate is washed to remove excess octadecyltrichlorosilane. For example, xylene is preferable as the cleaning agent. However, the above-described conditions such as temperature, pressure, time, and cleaning agent are not limited to those described above, and can be appropriately selected according to other conditions.

  The method for optimizing the surface energy of the substrate surface is not limited to the chemical surface modification treatment, but includes ion implantation treatment, sputter etching treatment, plasma treatment, rubbing treatment, and the like. There are also methods such as forming quantum dots.

・ Vapor deposition:
The organic alignment film can be deposited by a heat heating method, an electron beam vapor deposition method, a laser vapor deposition method, or the like. Using a vacuum evaporation system, place the above-mentioned raw material compound in a boat or crucible inside the apparatus in a state of facing the above-mentioned substrate, and then use the appropriate vacuum pump to fully After reducing the pressure, the boat or crucible is heated to evaporate the raw material compound and deposit it on the substrate surface to form a film.

The deposition conditions are not particularly limited, but are preferably as follows.
The degree of vacuum in the vapor deposition apparatus is usually preferably in the range of 1 × 10 ⁻⁴ Pa or less.
The temperature of the substrate is usually room temperature or higher, preferably 50 ° C. or higher, and usually 100 ° C. or lower, particularly preferably 75 ° C. or lower.
The deposition rate is usually 0.01 nm / second or more, preferably 0.02 nm / second or more, and usually 0.5 nm / second or less, particularly preferably 0.1 nm / second or less.
The film thickness is preferably in the range of usually 10 nm or more, especially 30 nm or more, and usually 100 nm or less, especially 50 nm or less.
It should be noted that after the deposition, post-treatment such as annealing may be added as necessary.

・ Characteristics of organic alignment film:
The organic alignment film of the present invention obtained by the above procedure usually shows the characteristics of a p-type semiconductor, and the mobility of holes serving as carriers is usually 1 cm ² / Vs or more, preferably 2 cm ² / Vs or more. Very high value. Furthermore, by performing various measures for improving the mobility as shown in Non-Patent Document 3, it is possible to obtain a higher mobility exceeding 3 cm ² / Vs.

  The carrier mobility can be obtained, for example, by preparing an FET (for example, an FET having a structure shown in FIG. 4 described later) using this organic alignment film and measuring the DC voltage-current characteristics.

このとき、Ｖ_DSは一定である。 The mobility is calculated based on the following formula (7) indicating the voltage-current characteristics when the FET is saturated.

At this time, V _DS is constant.

In the above formula (7), each symbol represents the following definition.
μ: Mobility (m ² / Vs)
W: Channel width (m)
L: Channel length (m)
C _i : Capacitance per unit area of insulating film (F / m ² )
_ID : drain current (A)
V _GS : Gate-source voltage (V)
V _T : FET threshold voltage (V)
V _DS : drain-source voltage (V)

[III. Applications of organic alignment film]
The organic alignment film of the present invention is preferably used as an organic semiconductor layer in various organic semiconductor devices because it is excellent in orientation as described above and exhibits high carrier mobility. Among them, it is particularly suitably used as a semiconductor layer (charge transport layer) such as an organic TFT that requires high mobility.

[III-1. Organic TFT]
3A to 3C are each abbreviated as an organic field effect transistor (hereinafter referred to as “organic field effect transistor” or “organic FET” as appropriate) as an example of an organic TFT which is a kind of the organic semiconductor device of the present invention. It is sectional drawing which shows the structural example of () typically. As shown in FIGS. 3A to 3C, the basic structure of the organic FET of the present invention is that an insulating layer 3 and a gate electrode 2 isolated by the insulating layer 3 are formed on a supporting substrate 1. And a charge transport layer 4 and a source electrode 5 and a drain electrode 6 provided so as to be in contact with the charge transport layer 4. The organic alignment film of the present invention can be used as, for example, the charge transport layer 4 described above. In addition, the order in which each layer is laminated | stacked in particular is not restrict | limited, You may laminate | stack in any order of Fig.3 (a)-(c), Furthermore, you may laminate | stack in another order. Furthermore, the organic FET of the present invention is not limited to the field effect transistor having the structure shown in FIGS. 3A to 3C, and may be formed on any two layers or on the outermost layer, as shown in FIGS. Layers other than those shown in c) may be further formed.

  The organic TFT of the present invention can be used as a switching element for driving an active matrix display, for example. This utilizes the fact that the current between the source and drain can be switched by the voltage applied to the gate, so that the switch is turned on only when a voltage is applied to or supplied to a certain display element, and the circuit is disconnected at other times. By doing so, a high-speed, high-contrast display is performed. Examples of such a display include an organic EL display, a liquid crystal display, electronic paper (electrophoretic element, electronic powder fluid, electrochromic, etc.) and the like.

  In addition, the organic TFT of the present invention can be suitably used in applications such as a sheet-type scanner transistor, a pressure sensor (artificial skin) transistor, and an IC tag transistor.

[III-2. Others]
In addition to the organic TFT, the organic semiconductor device of the present invention is used as an element for handling electrical signals such as a diode, an oscillation element, an integrated circuit; a light / electric conversion element such as a light emitting diode, a photoelectric tube, or a semiconductor laser; And various other sensors such as thermistors; semiconductor electrodes and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded.

[Example 1]
・ Measurement of characteristics of organic alignment film:
Using pentacene as a raw material compound of the organic alignment film, an organic FET provided with an organic alignment film satisfying the provisions of the present invention was prepared by the following procedure, and the characteristics thereof were measured. A schematic cross-sectional view of the produced organic FET is shown in FIG.

  As the substrate 11, a single crystal silicon wafer having a silicon oxide layer 11a formed on the surface by thermal oxidation was used.

  After the substrate 11 was washed before vapor deposition, a surface modification treatment was performed by the following procedure for the purpose of improving the electrical properties of the organic alignment film. A solution in which octadecyltrichlorosilane was used as a surface modifier and dissolved in a solvent (hexadecane) at a concentration of 2% by weight was prepared, and the substrate 11 was immersed in this solution for 4 hours. As environmental conditions at this time, the temperature was room temperature and the pressure was atmospheric pressure. After immersion, the substrate 11 was cleaned using xylene as a cleaning solution. After cleaning, the substrate 11 was dried.

Pentacene was deposited on the dried substrate 11 under the following conditions.
The substrate 11 was carried into the vacuum evaporation apparatus, and the pentacene and the substrate 11 placed in a tungsten boat were arranged so as to face each other. After reducing the pressure inside the vacuum evaporation apparatus to 1 × 10 ⁻⁴ Pa using a vacuum pump, the boat was heated to evaporate pentacene, and a pentacene film was formed on the surface of the substrate 11. The deposition conditions at this time were a substrate temperature of 60 ° C., a deposition rate of 0.05 nm / second, and finally an organic alignment film 12 (organic alignment film of Example 1) 12 made of pentacene having a thickness of 50 nm.

On the organic alignment film 12, gold was further evaporated through a shadow mask to form a source electrode 13 and a drain electrode 14, thereby producing an organic FET having the configuration shown in FIG.
When the characteristics of the organic alignment film of Example 1 were examined using the obtained organic FET, the characteristics of the p-type semiconductor were shown, and the mobility of holes serving as carriers was 2 cm ² / Vs.

-X-ray diffraction measurement:
An organic alignment film (pentacene thin film) for X-ray diffraction measurement was prepared by the same procedure as that for preparing the organic alignment film described in “Measurement of characteristics of organic alignment film” above. However, the surface modification treatment was not performed in order to avoid the influence of the base during X-ray diffraction measurement.

  The obtained organic alignment film was subjected to X-ray diffraction out-of-plane measurement and in-plane measurement by the following procedure.

As a measuring device, Rigaku RINT200PC (with in-plane gonio) was used.
The measurement conditions were as follows.

<Out-of-plane measurement>
・ X-ray output (CuKα): 50 kV, 250 mA
・ Scanning axis: 2θ
-Incident angle (θ): 1.0 °
Scanning range (2θ): 3.0 to 50.0 °
・ Measurement mode: Step
・ Scanning width: 0.05 °
・ Counting time: 1.0 sec
・ Slit ISS: 5.0 ° (H)
IS: 0.1mm
RSS: 0.5 ° (V)

<In-plane measurement>
・ X-ray output (CuKα): 50 kV, 250 mA
・ Scanning axis: φ / 2θχ
-Incident angle θ: 1.0 °
・ Fixed angle 2θ: 1.0 °
Scan range (2θχ): 3.0 to 50.0 °
・ Measurement mode: Step
・ Step width: 0.05 °
・ Counting time: 3.0 sec
・ Slit ISS: 0.5 ° (H)
IS: 0.1mm
RSS: 0.5 ° (H)

In addition, in the above-mentioned conditions, the definition of each symbol is as follows.
ISS: Incident Soller Slit
IS: Incident Slit
RSS: Receiving Soller Slit
H: Horizontal
V: Vertical

  FIG. 5 shows a diffraction pattern obtained by out-of-plane measurement, and FIG. 6 shows a diffraction pattern obtained by in-plane measurement. As is apparent from these diffraction patterns, the organic alignment film of Example 1 has peaks at Bragg angles 2θ = 5.8 ° and 11.5 ° in out-of-plane measurement, and in-plane In the measurement, there were peaks at Bragg angles 2θ = 19.1 °, 23.7 °, and 28.1 °. Any of these peaks are within the preferred range defined in the present invention.

Subsequently, based on these diffraction patterns, the lattice constant of the organic alignment film of Example 1 was determined by the following procedure.
First, the lattice constant c was determined from the out-of-plane diffraction pattern. Furthermore, since the value of c substantially coincided with the major axis of the pentacene molecule itself, α and β were determined on the assumption that the c axis was perpendicular to the substrate. a and b were determined from the in-plane diffraction pattern. γ is an X-ray diffraction pattern (in-plane and out-of-plane) and packing with a known pentacene single crystal structure (Campbell et al., Acta Crystallographica, Vol. 14, p.705-p.711, 1961).

  As a result, the determined lattice constants were a = 7.5Å, b = 6.0Å, c = 15.4Å, α = 90.0 °, β = 90.0 °, and γ = 91.0 °. It was. Any of these lattice constants is within the preferable range defined in the present invention.

-Angle between two molecules and effective carrier mass:
For the organic alignment film of Example 1, the angle between two molecules and the effective carrier mass were determined by the following procedure.

The electron density calculation and band calculation by the density functional method are described in [I-1. This was carried out according to the procedure described in “Definition of effective carrier mass” in the column “Characteristics relating to effective carrier mass”.
For integration in the reciprocal lattice space for electron density calculation for pentacene thin films, see Monkhorst-Pack method (HJ Monkhorst et al., Physical Review B, Vol.13, No.12, p.5188-5192, 1976). 8), the k points of 8 points obtained by dividing the Brillouin zone into 2 × 2 × 2 grids were sampled and performed in a space of 84 × 64 × 168 grids considering cut-off energy up to 80 Ry (1088 eV).

に平行、且つ重心が原点と

の位置にあり、それぞれの分子面が

及び

に平行とした。このとき、二分子面のなす角はφ＝７７．３°である。 The basic thin film structure includes two pentacene molecules in a lattice determined by X-ray diffraction measurement. The structure of the pentacene molecule in the thin film lattice was the molecular structure in a single crystal described in Campbell et al., Acta Crystallographica, Vol. 14, p.705-711, 1961. The arrangement of pentacene molecules in the thin film lattice is

Parallel to the center of gravity

Each molecular plane is

as well as

Parallel to At this time, the angle formed by the bimolecular plane is φ = 77.3 °.

  This structure was used as the initial structure, and the structure was optimized so that the bias of the force applied to the two molecules was alleviated by the steepest descent method while the lattice constant was fixed. The molecules are not rotated by the structure optimization, and therefore the molecular planes of the two molecules may be on the diagonal of the unit cell. Note that the simulation result of the X-ray diffraction pattern in this oriented structure was consistent with the actually measured pattern.

  The electronic structure calculation and the band calculation were performed on this optimized structure. From the obtained band diagram, the above [I-1. According to the procedures (iii) and (iv) of “Definition of effective carrier mass” in the column “Characteristics relating to effective carrier mass”, two points, Γ point and Z point, were selected for both holes and electrons.

の各成分の微小変化量により

として、下記式

により計算した。ここで、｛ｉ，ｊ，ｋ｝＝｛ｘ，ｙ，ｚ｝である。 Next, the effective mass tensor was calculated from the two points of the Γ point and the Z point by a numerical difference, and the eigenvalues were obtained by further diagonalizing. For numerical differences, the difference width is the wave vector

By the minute change amount of each component of

As

Calculated by Here, {i, j, k} = {x, y, z}.

The obtained value of effective carrier mass is shown in Table 1 described later. 0.2 m _e in Γ point for holes, a value of 0.7 m _e are obtained in the Z point, also, for the electronic 0.3 m _e, a value of 1.3 m _e are obtained in the Z point Γ point It was. Therefore, the above [I-1. As is apparent from the description of “range of effective carrier mass” and “relationship between effective carrier mass and mobility” in the column “Characteristics related to effective carrier mass”, the organic alignment film of this example is expected to have high mobility. The

・ Absorption spectrum measurement:
An organic alignment film (pentacene thin film) for absorption spectrum measurement was prepared by the same procedure as that for preparing the organic alignment film described in “Measurement of characteristics of organic alignment film” above. However, the film was formed by changing the substrate to transparent glass for spectrum measurement. Moreover, the film thickness of the obtained organic alignment film was about 80 nm.

  The obtained organic alignment film was measured for absorption spectrum by microspectroscopy in order to avoid the influence of macroscopic nonuniformity. The measurement conditions of the microspectrophotometry are shown below.

<Microscope>
・ Device: Metal system microscope (Olympus)
Objective lens: 100 times (NA = 0.40, β = 47 °)
・ Reference sample: Glass substrate (not formed)

<Spectroscope>
・ Device: Instant multi-photometry system MCPD-113 (Otsuka Electronics Co., Ltd.)
・ Resolution: 2.4nm
・ Center wavelength: 550nm, 850nm
・ Accumulation time: 10,000 msec
・ Number of integration: 4 × 2 ・ Measurement point: Near the center

  In addition, a halogen lamp was used as a light source, and the measurement was performed when the light was incident perpendicularly to the organic alignment film to be measured and when the light was incident obliquely at an angle of 59 ± 2 ° from the vertical. The measurement region by the microspectroscopy method was 5.8 μmφ in the case of normal incidence, and about 5.8 × 12 μm in an unfocused ellipse in the case of oblique incidence of 59 ± 2 ° from the vertical.

  The obtained absorption spectrum is shown in FIG. As is apparent from FIG. 7, the absorption spectrum due to the normal incident light and the absorption spectrum due to the obliquely incident s-polarized light and the p-polarized light at 59 ± 2 ° from the normal are clearly large in the vicinity of 1.85 eV and 2.12 eV. A peak is observed. Further, in the case of oblique incidence of 59 ± 2 ° from the vertical, specific absorption is observed only in the s-polarized light in the region of 1.3 eV to 1.8 eV, while in the corresponding region in the p-polarized light Absorption was not observed. This indicates that the obtained film has a good orientation with respect to the substrate surface.

[Example 2]
-Angle between two molecules and effective carrier mass:
In the structure of the organic alignment film of Example 1 (at this time, the molecular plane between the two molecules is on the diagonal of the unit cell, respectively), [I-2. In accordance with the description of “Definition of angle between two molecules and rotation angle” in the column of “Characteristics related to orientation structure”, the molecule having the center of gravity at the origin is rotated 20 ° clockwise around the rotation axis (θ = 32. 7 °), that is, φ = 57.3 ° (the organic alignment film in this state is referred to as “organic alignment film of Example 2”). From the obtained band diagram, it is stably present when carriers are injected. The two points, the Γ point and the Z point, were selected for both holes and electrons. The carrier effective mass was calculated for the Γ point and the Z point by the same calculation method as in Example 1.

The obtained value of effective carrier mass is shown in Table 1 described later. The hole obtained a value of 0.6 m _e in Γ point and point Z, the electron was obtained a value of 0.7 m _e in Γ point and Z point. Therefore, the above [I-1. As is clear from the description of “range of effective carrier mass” and “relation between effective carrier mass and mobility” in the column “Characteristics relating to effective carrier mass”, the organic alignment film of Example 2 also has high mobility. Be expected.

[Comparative Example 1]
A known pentacene single crystal was used as Comparative Example 1.

・ Characteristics of pentacene single crystal:
The mobility of the pentacene single crystal is described in Non-Patent Document 1 described above. According to this document, the value of the mobility of hole induced by an electric field in a pentacene single crystal is 0.1 to 0.5 cm ² / Vs.

-Carrier effective mass:
As the pentacene single crystal, lattice constants and molecular structures described in Campbell et al., Acta Crystallographica, Vol. 14, p.705-p.711, 1961 were used. For the two molecules in the lattice, the structure was relaxed while the lattice constant was fixed. Again, no change in molecular rotation occurred.

  The calculation of the electron density and the band calculation of the pentacene single crystal are the same as those described in [I-1. The procedure described in “Definition of effective carrier mass” in the column “Characteristics relating to effective carrier mass” is performed. In addition, the integration in the reciprocal lattice space was performed in a 90 × 70 × 180 grid space in which 8 k points of a 2 × 2 × 2 grid were sampled and the cut-off energy was considered up to 80 Ry (1088 eV). From the obtained band diagram, the above [I-1. According to the procedures (iii) and (iv) of “Definition of effective carrier mass” in the column “Characteristics relating to effective carrier mass”, two points, Γ point and B point, were selected for both holes and electrons. The carrier effective mass was calculated for the Γ point and the B point by the same calculation method as in Example 1.

The obtained value of effective carrier mass is shown in Table 1 described later. 3.1m _e in Γ point for holes, a value of 2.6 m _e is obtained at point B, the electronic 1.9m _e, a value of 2.2 m _e is obtained at point B at Γ point. Therefore, the above [I-1. As is clear from the description of “range of effective carrier mass” and “relation between effective carrier mass and mobility” in the column “Characteristics relating to effective carrier mass”, the high mobility of the pentacene single crystal of Comparative Example 1 is I can't expect it.

-X-ray diffraction measurement:
The X-ray diffraction measurement results of the pentacene single crystal were referred to the description of Campbell et al., Acta Crystallographica, Vol. 14, p.705-711, 1961. According to this document, the pentacene single crystal is triclinic, and a = 7.93 Å, b = 6.14 Å, c = 16.03 ＝; α = 101.9 °, β = 112.6 °, γ = It is determined to be 85.8 °. This is different from the organic alignment film of Example 1 and does not fall within the lattice constant range defined in the present invention.

[Comparative Example 2]
A known pentacene vapor-deposited film was used as the organic alignment film of Comparative Example 2.

・ Characteristics of known pentacene deposited films:
The mobility of a known pentacene vapor-deposited film is described in Non-Patent Document 2 described above. According to this document, the mobility of the known pentacene vapor deposition film is 0.7 cm ² / Vs.

・ Absorption spectrum measurement:
As for the absorption spectrum measurement result of the pentacene vapor deposition film, the description of R. Hesse et al., Chemical Physics, Vol. 49, p. 201-211, 1980 was referred to. According to this document, very weak absorption is reported in the vicinity of 1.72 eV, which is a lower energy side than the main absorption of 1.90 eV. However, this absorption originates from defects in the thin film, and is not due to the ordered orientation in the thin film that appeared as a unique polarized light absorption spectrum in Example 1.

[Comparative Example 3]
-Angle between two molecules and effective carrier mass:
In the structure of the organic alignment film of Example 1 (at this time, the molecular plane between the two molecules is on the diagonal of the unit cell, respectively), [I-2. In accordance with the description in “Definition of angle between two molecules and rotation angle” in the column of “Characteristics related to orientation structure”, the molecule having the center of gravity at the origin is rotated 20 ° counterclockwise about the rotation axis (θ = 7. 3 °), that is, φ = 82.7 ° (the organic alignment film in this state is referred to as “organic alignment film of Comparative Example 3”). From the obtained band diagram, it is stably present when carriers are injected. The two points, the Γ point and the Z point, were selected for both holes and electrons. The carrier effective mass was calculated for the Γ point and the Z point by the same calculation method as in Example 1.

The obtained value of effective carrier mass is shown in Table 1 described later. The hole obtained a value of 1.7 m _e in Γ point and point Z, the electronic 4.6 m _e, a value of 5.8 m _e in Z points obtained in Γ point. Therefore, the above [I-1. As is clear from the description of “range of effective carrier mass” and “relationship between effective carrier mass and mobility” in the column “Characteristics related to effective carrier mass”, the organic mobility of Comparative Example 3 is high. I can't expect it.

[Calculation result of effective carrier mass]

  Although the use of the organic alignment film of this invention is not specifically limited, Since it is excellent in orientation as mentioned above and shows high carrier mobility, it is preferably used as an organic semiconductor layer in various organic semiconductor devices. Among them, it is particularly suitably used as a semiconductor layer (charge transport layer) such as an organic TFT that requires high mobility.

It is a figure for demonstrating "the angle | corner between two molecules." (A), (b) is a figure for demonstrating the relationship between "the angle | corner between two molecules" and carrier mobility. (A)-(c) is sectional drawing which shows the structural example of the field effect transistor which is a kind of organic-semiconductor device of this invention. FIG. 3 is a cross-sectional view schematically showing a configuration of an FET manufactured for measuring the carrier mobility of the organic alignment film (pentacene thin film) of Example 1. It is the diffraction pattern obtained by the parallel optical system X-ray diffraction out-of-plane measurement about the organic alignment film (pentacene thin film) of Example 1. It is the diffraction pattern obtained by the parallel optical system X-ray diffraction in-plane measurement about the organic alignment film (pentacene thin film) of Example 1. It is the absorption spectrum obtained by the microspectroscopy method about the organic alignment film (pentacene thin film) of Example 1.

Explanation of symbols

1 Substrate 2 Gate electrode 3 Insulator layer 4 Charge transport layer (semiconductor layer)
5 Source electrode 6 Drain electrode 11 Substrate (single crystal silicon wafer)
11a Silicon oxide layer 12 Charge transport layer (organic alignment film)
13 Source electrode 14 Drain electrode

Claims (7)

Carrier effective mass (m ^*) satisfies the 0 <m ^* ≦ 0.8m _e (where, m _e represents the electronic original mass.)
An organic alignment film characterized by that. 2. The organic material according to claim 1, wherein an angle (φ) formed between the least square planes of each molecule between two closest molecules in the unit cell constituting the thin film structure satisfies 0 ≦ φ ≦ 80 °. Alignment film. The organic alignment film according to claim 1, comprising an acene-based compound. The organic alignment film according to claim 3, comprising a pentacene compound. The lattice constant is
a = 7.5 ± 1Å, b = 6.0 ± 1Å, c = 15.4 ± 1Å,
α = 90.0 ± 10 °, β = 90.0 ± 10 °, γ = 91.0 ± 10 °
5. The organic alignment film according to claim 4, wherein the organic alignment film falls within each of the ranges. In parallel optical system X-ray diffraction out-of-plane measurement (thin film measurement),
Bragg angle 2θ = 5.8 ± 0.5 °, and
Bragg angle 2θ = 11.5 ± 0.5 °
Having a peak within each range of
In parallel optical system X-ray diffraction in-plane measurement (thin film measurement),
Bragg angle 2θ = 19.1 ± 0.5 °,
Bragg angle 2θ = 23.7 ± 0.5 °, and
Bragg angle 2θ = 28.1 ± 0.5 °
The organic alignment film according to claim 4, wherein the organic alignment film has a peak in each of the ranges. An organic semiconductor device using the organic alignment film according to claim 1.

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