JP5948765B2 - Ink composition for electronic device using π-electron conjugated compound precursor, method for producing organic film, and method for producing field effect transistor - Google Patents

Description

The present invention relates to an ink composition for an electronic device using a π-electron conjugated compound precursor having a detachable soluble group, an application thereof, and a production method thereof.
The ink composition for electronic devices of the present invention is useful as a material for various organic electronics such as a photoelectric conversion element, a thin film transistor element, and a light emitting element.

In recent years, research and development of organic thin film transistors using organic semiconductor materials has been active.
Organic semiconductor materials can be easily formed into thin films by a simple process using a wet process such as a printing method, spin coating method, etc., and the manufacturing process temperature can be lowered as compared with a thin film transistor using a conventional inorganic semiconductor material. There are advantages. As a result, semiconductor thin films can be formed on plastic substrates with low heat resistance in general, making it possible to reduce the weight and cost of electronic devices such as displays, as well as various applications such as applications that take advantage of the flexibility of plastic substrates. Can be expected.

  So far, acene-based materials such as pentacene have been reported as low-molecular organic semiconductor materials. Organic thin-film transistors using pentacene as an organic semiconductor layer have been reported to have a relatively high mobility, but these acene-based materials have extremely low solubility in general-purpose solvents. When thinning as a layer, a vacuum deposition process is generally performed. In addition, since the atmospheric stability is poor, it does not meet the expectation for an organic semiconductor material that a device can be manufactured by a simple process such as coating and printing as described above.

Recently, 2,7-dialkyl [1] benzothieno [3,2-b] [1] benzothiophene, which is one of acene-based condensed polycyclic materials, has high solubility, such as spin coating and casting. It is reported that a mobility comparable to that of pentacene (about 2.0 cm ² / V · s) is exhibited by heat treatment at a relatively low temperature.
However, since the above compound has a liquid crystal phase, the transition temperature to the liquid crystal phase is relatively low at about 100 ° C., and the film structure can be changed by the heat treatment after film formation. There's a problem.
Moreover, when the solubility of an organic-semiconductor layer is high, it has the subject that solvent resistance becomes low in a subsequent device manufacturing process.

Under these circumstances, a low molecular weight compound having high solvent solubility is used as a semiconductor precursor (hereinafter referred to as a precursor), which is dissolved in a solvent and formed into a film by a coating process, and then converted into a semiconductor to obtain an organic semiconductor film. A method of manufacturing a field effect transistor has been reported.
For example, there is an example using pentacene or a similar aromatic hydrocarbon (Non-Patent Document 1), porphyrin (Non-Patent Document 2), oligothiophene (Non-Patent Document 3), and the like.
The above pentacene and porphyrins are difficult to handle in the atmosphere because the semiconductor molecules after conversion are not stable to oxygen and water, but there is a problem of film formation by wet processes such as printing and spin coating. It has the advantages that it is possible, exhibits relatively high mobility, and has high solvent resistance and heat resistance.

  The present inventors have shown that the organic semiconductor film can be formed by a simple method using a wet process such as a printing method or a spin coating method. After the film formation, the organic semiconductor film is insolubilized by a simple insolubilization process, and then the device is manufactured. Attempts have been made to develop organic semiconductor precursor materials that reduce damage in the post-process and that exhibit good semiconductor properties after insolubilization. As a result of intensive studies, we reported the development of condensed polycyclic organic semiconductor materials with good mobility (Patent Document 1) and the development of precursors with high solvent solubility (Patent Documents 2, 3, and 4). ing. As a method for converting from a precursor to a semiconductor, for example, there is a method of applying thermal energy.

  As a guideline for manufacturing a high-performance transistor using a low-molecular crystalline organic semiconductor material as described above, the crystal grains of the organic semiconductor layer in the channel region are grown to be trapped by the crystal grain boundaries. It is known to reduce the influence of scattering and to reduce the influence of carrier traps at the interface between the gate insulating layer serving as the channel region and the organic semiconductor layer.

In addition, in an organic thin film transistor, it is known that contact resistance between an electrode and an organic semiconductor becomes a problem when a low voltage region or a channel length is shortened. The contact resistance here means the resistance between the source / drain electrodes and the organic semiconductor layer in the channel region, and it is necessary to reduce this to reduce the threshold voltage and stabilize the device performance. It becomes.
As a cause of the large contact resistance, it is mentioned that an ohmic junction is hardly formed at the junction interface between the electrode which is an inorganic material and the organic semiconductor, and a Schottky junction is easily formed.

Here, the ohmic junction surface and the Schottky junction surface are surfaces formed between the organic semiconductor layer and the source / drain electrodes, and form the Fermi level of the material forming the organic semiconductor layer and the electrode. It is determined by the relationship with the Fermi level of the material.
Specifically, when the organic semiconductor is a p-type semiconductor, when the Fermi level of the organic semiconductor material is higher than the Fermi level of the electrode material, the bonding surface between the organic semiconductor layer and the electrode is an ohmic bonding surface, On the contrary, when the Fermi level of the organic semiconductor material is lower than the Fermi level of the electrode material, it is explained that the interface between the organic semiconductor layer and the electrode is a Schottky interface.
However, the state of the interface between the organic substance and the metal is still in the research stage, and details are not clear. It is also known that the contact resistance is caused not by the characteristics of the bonding interface itself between the electrode and the organic semiconductor but by the low electrical conductivity of the organic semiconductor region adjacent to the bonding interface. This is because the organic material itself has a lower electrical conductivity than the inorganic material.
Further, in the device manufacturing process, the carrier mobility of the semiconductor layer in the region adjacent to the bonding interface may be smaller than that of the channel region. For example, a bottom contact type device includes a step of forming an organic semiconductor layer after forming source / drain electrodes during device fabrication, so that many small grains of organic semiconductor are formed on different surfaces of the insulating film and the electrode. As a result, the organic semiconductor crystal grains cannot be made large and the electrical conductivity may be lowered. It has also been reported that in the top contact type element, the organic semiconductor layer is damaged during the electrode material forming process.

In order to reduce the contact resistance as described above, it is necessary to reduce the resistance at the junction interface between the source / drain electrode and the organic semiconductor layer and to improve the electrical conductivity of the organic semiconductor material adjacent to the junction. is there.
In response to such a problem of contact resistance, it is known that applying doping such as that performed with an inorganic material contributes to a reduction in contact resistance.
For example, during the manufacture of a field effect transistor using an amorphous silicon layer or a polycrystalline silicon layer, the contact region is doped by implanting phosphorus or boron into the silicon layer located near the source and drain contacts. . The silicon network incorporates phosphorus or boron atoms that function as donors (electron-donating materials) or acceptors (electron-accepting materials), resulting in increased carrier density contributing to conduction and in the doped region. The electrical conductivity of silicon increases.

  Similarly, it is known that electrical conductivity can be improved for many organic semiconductor materials by implanting (doping) appropriate impurities. Here, doping means introducing into an organic semiconductor an accelerator or a donor as a dopant. When a small amount of acceptor material (donor material) is introduced into the organic semiconductor, the added dopant undergoes a chemical reaction, generating a positive (negative) charge, ie, a hole (electron). The acceptor-doped transport layer is p-type doping, and the donor-doped layer is n-type doping (both terms are used in the same manner as inorganic semiconductor doping). It can be said that the acceptor is a compound having a high electron affinity and the donor is a compound having a low ionization potential.

Examples of the doping method as described above and methods for reducing the contact resistance between an electrode and an organic semiconductor layer using a doped organic material are disclosed in Non-Patent Document 4, Patent Documents 5 and 6, for example. The thing that is.
Non-Patent Document 4 reports that contact resistance can be reduced by introducing an acceptor dopant between an electrode and an organic semiconductor layer.
Patent Document 5 discloses a method of introducing a doped organic material layer (intermediate layer) between an organic semiconductor layer and an electrode made of an inorganic material. Since the doped intermediate layer greatly improves the electron concentration or hole concentration at the interface with the electrode, it can be in ohmic contact with the electrode. It has also been reported that when the main component of the intermediate layer and the main component of the organic semiconductor layer are the same, the bonding strength between the intermediate layer and the organic semiconductor layer is also improved.
Patent Document 6 discloses a method of forming a precursor layer of an organic semiconductor and / or an organic conductor and forming a semiconductor layer and / or a conductive layer. It is said that the dopant can be mixed with the precursor itself as desired to convert the precursor into a semiconductor material, and at the same time, the dopant acts to develop conductivity.

However, it cannot be said that Patent Document 5 sufficiently clarifies a method for forming an organic film having a higher conductivity by doping a crystalline organic material.
As described above, in order to produce an organic film with high electrical conductivity using a crystalline organic material, it is necessary to control the crystal grains to improve mobility. In addition, the conductivity of the doped organic film is improved by increasing the electron / hole concentration by doping. Therefore, when a doped organic film is formed after mixing a doping material and an organic material to be doped in advance, there is a problem that both the growth of large crystal grains and the improvement of the carrier density by doping are achieved. This is true even when the crystalline organic film is formed by converting the precursor, and the conversion of the precursor and the control of the crystal growth are important (Non-patent Document 5).
The conversion from precursor to semiconductor is a desorption reaction involving a change in weight or volume, and the cohesive force between molecules after conversion becomes the driving force for structure formation, and is characterized by crystal growth accompanying the desorption reaction. is there.
In general, the solubility of the semiconductor layer forming material in the ink liquid tends to depend on the bulky molecular structure. On the contrary, the conductivity of the ink layer after application is easily agglomerated due to the grouped molecular structure. However, the solubility in the ink and the conductivity of the semiconductor layer formed using this ink are usually incompatible with each other, but this point can be determined only by the heat conversion of the precursor material and the dopant alone. Even when trying to solve it, it is often difficult to obtain satisfactory results if the use of the dopant is not appropriate.
Even if the dopant is mixed in the precursor film by the method described in Patent Document 6, there is a concern that the dopant becomes a source of crystal nuclei and forms a film with many crystal grain boundaries when the semiconductor is crystal-grown. . Therefore, even if the carrier density in the semiconductor film is increased by the dopant, the influence of carrier scattering at the crystal grain boundary becomes large, and as a result, there is a possibility that sufficient electrical conductivity cannot be obtained. As a method for avoiding such a problem, it is conceivable to dope after forming a semiconductor layer with few crystal grain boundaries.
In the method described in Non-Patent Document 6, doping is performed in the vicinity of the surface of the semiconductor film by forming a semiconductor layer and then depositing an acceptor material serving as a dopant by mask deposition by vacuum deposition. However, since this method is performed by a vacuum process, it cannot be said to be a simple and low-cost process. In addition, by laminating the electrode after doping, doping at the junction interface between the electrode and the semiconductor is possible, but it is not clear whether the doping can be performed uniformly over the depth direction of the semiconductor film. As a performance index of the organic thin film transistor, it is important to pass a high current, but it is important to uniformly control the conductivity of the doped organic film introduced in order to reduce the contact resistance. Needless to say, the junction between the doped organic film and the semiconductor layer in the channel region must have a sufficiently low resistance.

  As described above, it is difficult to say that there is sufficient knowledge about a method for producing a homogeneously doped organic film with respect to a crystalline organic semiconductor material. Similarly, there is no sufficient knowledge about a method for uniformly doping a crystalline organic film formed from a precursor. In addition, a method for realizing such an organic film with controlled electrical conductivity by a simple process and a cost-effective method has not yet been clarified.

Therefore, an object of the present invention is to improve the conductivity of a semiconductor film obtained by converting a precursor film.
As a result of that, the contact resistance can be obtained electrical characteristics of the improved high-performance electronic devices for ink compositions and electronic devices using the same, and aims to provide a field effect transistor, and a manufacturing method thereof To do.

  In order to achieve such an object, the ink composition for an electronic device of the present invention dissolves at least a dopant that can be doped into a π-electron conjugated compound, the π-electron conjugated compound precursor, the dopant, and a precursor material. It is characterized by containing a solvent. The electronic device and the field effect transistor using the ink composition, after applying the ink composition and drying the solvent, to convert the precursor into a semiconductor by thermal energy, to form a crystalline organic film, It can be produced by a simple process. Since the amount of the dopant contained in the ink composition is appropriately controlled, the mobility of the semiconductor film can be increased without inhibiting crystal growth during the formation of the semiconductor film. In addition, it is doped with the dopant contained in the ink simultaneously with the formation of the semiconductor film, and the carrier density can be improved.

That is, the said subject is solved by this invention containing the ink composition as described in the following (1)-(9), an organic film, and FET (field effect transistor).
(1) “Ink composition for electronic device, comprising at least a π-electron conjugated compound precursor, a dopant for the π-electron conjugated compound, and a solvent for dissolving the π-electron conjugated compound precursor and the dopant. An ink composition characterized by that. "
(2) “The π-electron conjugated compound precursor is composed of a dithienobenzothiophene derivative represented by the following general formula (I), and by applying an external stimulus thereto, the π-electron conjugated compound precursor is The ink composition as described in the above item (1), wherein a dithienobenzothiophene derivative represented by the following general formula (II) is obtained by the elimination of X—Y:

[In the above formula, X and Y represent a group in which X and Y are bonded to each other by an external stimulus to leave from the compound of general formula (I) as XY, and R ¹ and R ² are each independently substituted. Or an unsubstituted alkyl group or a substituted or unsubstituted aryl group, wherein R ³ to R ¹⁰ are each independently hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted group Represents an alkylthio group, or a substituted or unsubstituted aryl group. ]
(3) The item (1) or (1), wherein one of X and Y of the π-electron conjugated compound precursor is hydrogen and the other is a hydroxyl group or a group having an ester structure or a thioester structure. The ink composition according to item 2). "
(4) The above-mentioned (3), wherein the ester structure or thioester structure of the π-electron conjugated compound precursor is any one of the following general formulas (III), (IV), and (V): The ink composition according to item;

[In the above formula, R ¹¹ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. ]. "
(5) In any one of (1) to (4), wherein the molar concentration of the dopant is 5% or less with respect to the molar concentration of the π-electron conjugated compound precursor. Ink composition. "
(6) Any one of the items (1) to (5), wherein the dopant is any one of an acid, a Lewis acid, a halogen, an organic acid, a transition metal compound, and an electron-accepting molecule. Ink composition as described in the above. "
(7) “After the ink composition according to any one of the above items (1) to (6) is adhered on a support, an external stimulus is applied to the diion represented by the general formula (II). Organic film composed of thienobenzothiophene derivatives. "
(8) The organic film as described in (7) above, wherein the external stimulus is light or thermal energy.
(9) “A field effect transistor using the organic film according to the item (7) or (8)”.

As will be understood from the following detailed and specific description, according to the present invention, a semiconductor film formed by applying a precursor using a wet process such as a printing method or a spin coating method, and then heat-converting, As will be described in the following examples, it was confirmed that the conductivity was improved as compared with that formed from a precursor film containing no dopant .
Since the electron conjugated compound used in the present invention has high solvent resistance and high heat resistance, a semiconductor film of the same material that is not doped can be easily connected to the doped semiconductor film. Since the same crystalline material is connected, the continuity of the film can be made uniform at the molecular level, and the resistance from the electrode to the channel region can be made sufficiently low.

It is a microscope observation photograph of the single crystal of the dithienobenzodithiophene derivative (VII) used by this invention. It is a SEM photograph of the organic film containing the dithienobenzodithiophene derivative (VII) which is a conversion film of the dithienobenzodithiophene derivative precursor (VI) used by this invention. It is a SEM photograph of the vacuum evaporation film of the dithieno benzodithiophene derivative (VII) used by this invention. It is a figure which shows schematic structure of the organic thin-film transistor concerning this invention. It is a photograph of the polarization microscope observation result of the ink samples 1-4 created in Example 1 of this invention. It is a graph of the current-voltage measurement result of the ink samples 1-4 created in Example 1 of this invention. It is a photograph of the polarization microscope observation result of the ink samples 5-7 created in Example 2 of the present invention. It is a graph of the current-voltage measurement result of the ink samples 5-7 created in Example 2 of the present invention.

Hereinafter, the present invention will be described with reference to embodiments. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the scope of the present invention.
Here, the π-electron conjugated compound precursor used in the present invention and the π-electron conjugated compound obtained from the compound precursor will be specifically described.

[Π-electron conjugated compound precursor and π-electron conjugated compound obtained from the precursor]
The π-electron conjugated compound precursor of the present invention is preferably a dithienobenzodithiophene derivative represented by the following general formula (I).

[In the above formula, X and Y represent a group in which X and Y are bonded by an external stimulus and leave from the compound of general formula (I) as XY, and R ¹ and R ² are each independently substituted. Or an unsubstituted alkyl group or a substituted or unsubstituted aryl group, wherein R ³ to R ¹⁰ are each independently hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted group Represents an alkylthio group, or a substituted or unsubstituted aryl group. ]

  X and Y are preferably a combination of hydrogen and a group having an ester structure. Among them, a combination of a carboxylic acid ester and hydrogen, a carbonate ester and hydrogen, and a xanthate ester and hydrogen is preferable, and a combination of any one of the following general formulas (III), (IV), and (V) with hydrogen is particularly preferable.

[In the above formula, R ¹¹ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. ]
In the dithienobenzodithiophene derivative represented by the general formula (I), as a result of X and Y binding to each other and elimination as XY by an external stimulus, a new alkane site is generated, which is represented by the general formula (II). Into dithienobenzodithiophene derivatives.

Examples of the substituted or unsubstituted alkyl group in R ^{1 to} R ¹¹ in the general formulas (I) to (V) include, for example, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, and t-butyl. Group, s-butyl group, n-butyl group, i-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, 3,7-dimethyloctyl group, 2 -Ethylhexyl group, trifluoromethyl group, 2,2,2-trifluoroethyl, 2-cyanoethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, cyclopentyl group, cyclohexyl group, etc. The substituted or unsubstituted alkoxy group and alkylthio group include, for example, an alkoxy group in which an oxygen atom or a sulfur atom is inserted at the bonding position of the alkyl group. Include those alkylthio groups.

Examples of the substituted or unsubstituted aryl group in R ^{1 to} R ¹¹ include benzene, naphthalene, biphenyl, terphenyl, quarterphenyl, pyrene, fluorene, 9,9-dimethylfluorene, azulene, anthracene, triphenylene, chrysene, 9 -Benzylidenefluorene, 5H-dibenzo [a, d] cycloheptene, [2,2] -paracyclophane, triphenylamine, thiophene, bithiophene, terthiophene, quarterthiophene, thienothiophene, benzothiophene, dithienylbenzene, furan, Examples include benzofuran, carbazole, and benzodithiazole. These may further have the above substituted or unsubstituted alkyl group, alkoxy group, thioalkoxy group, or halogen groups of fluorine, chlorine, iodine and bromine as substituents.

In particular, by introducing the alkyl group or aryl group into R ¹ and R ² , a rod-like molecular shape is obtained, and the crystal is likely to grow two-dimensionally, so that a crystalline continuous film is easily obtained. Further, when an aryl group is introduced, the ionization potential of the material becomes shallow due to the expansion of the conjugated system of molecules in the state of the general formula (II), and the hole transport property is improved.

  The synthesis method of the dithienobenzodithiophene derivative represented by the general formula (I) is not particularly limited, and various known methods can be employed. As a procedure, after a dithienobenzodithiophene skeleton is constructed, a desorption unit represented by X and Y may be introduced.

  For example, in the general formula (I), when X is a group having an ester structure and Y is hydrogen, a dithienobenzodithiophene skeleton is constructed, then derivatized to a carbonyl compound, and further a nucleophile such as a Grignard reagent The target carboxylic acid ester can be obtained by reacting with alcohol and reacting this alcohol with acid chloride or acid anhydride.

  Moreover, after making the said alcohol body react with carbon disulfide using a base, and making it react with alkylating reagents, such as alkyl halide, the target xanthogenic acid ester body can be obtained.

  Moreover, a carbonate ester body can be obtained by processing the alcohol body with a chloroformate.

In addition, the said carbonyl compound is compoundable by well-known various reaction, For example, reaction of following (a)-(d) is mentioned.
(A) Vilsmeier reaction represented by the following formula

(B) Reaction of aryllithium compound represented by the following formula with formylation or acylation reagents including DMF, N-formylmorpholine, N-formylpiperidine, various acid chlorides, various acid anhydrides, etc.

(C) Gatterman reaction represented by the following formula:

(D) Friedel-Crafts reaction represented by the following formula:

In the above formula, R represents an alkyl group, har represents a halogen, and R ^{1 to} R ¹¹ are the same as in the general formula (I). Further, when X is hydrogen and Y is a group having an ester structure, it can be easily synthesized by the same reaction.

  The π-electron conjugated compound precursor obtained as described above is used after removing impurities such as the catalyst, inorganic salt, unreacted raw materials, and by-products used in the reaction. For the purification operation, conventionally known methods such as recrystallization, various chromatographic methods, sublimation purification, reprecipitation, extraction, Soxhlet extraction, ultrafiltration, dialysis and the like can be used. Since contamination with impurities adversely affects the semiconductor characteristics, it is desirable to make the purity as high as possible. A material having excellent solubility has less restrictions on these purification methods, and as a result, has a positive effect on semiconductor characteristics.

  In the dithienobenzodithiophene derivative represented by the general formula (I), as shown by the following formula, an alkane moiety is formed by elimination of XY in the general formula (I), and the general formula (II) To the dithienobenzodithiophene derivative represented.

  At this time, when the combination of XY is hydrogen and a carboxylic acid ester, the carboxylic acid molecule is desorbed, and when the combination of XY is hydrogen and a xanthate, the xanthogenic acid site is desorbed. Thereafter, it is further decomposed and removed as carbonyl sulfide and a thiol compound. When the combination of XY is hydrogen and carbonate, decarboxylation still occurs.

In the dithienobenzodithiophene derivative represented by the general formula (II) generated by the above XY elimination, the conjugated system is expanded as compared with the structure represented by the general formula (I) before the elimination. Since flatness is obtained, crystallinity is improved, and good charge transporting characteristics that can be used as a semiconductor member are exhibited.
At the same time, the solubility in the solvent changes dramatically before and after XY desorption. In the general formula (I), the side chain of the dithienobenzodithiophene unit (R ¹ , R ³ , R ⁵ , X, Y and the site containing R ² , R ⁴ , R ⁶ , X, Y) is good for the molecule. In general formula (II), such an effect is reduced and the solubility is greatly lowered.

  Examples of the energy applied to perform the elimination reaction include heat, light, and electromagnetic waves. From the viewpoints of reactivity, yield, and post-treatment, thermal energy or light energy is desirable, and thermal energy is particularly preferable. Moreover, you may apply the said energy in presence of an acid or a base.

Usually, the elimination reaction depends on the structure of the functional group, but often requires heating.
The heating method for carrying out the elimination reaction includes a method of heating on a support, a method of heating in an oven, a method of irradiation with microwaves, a method of heating by converting light into heat using a laser, Although various methods, such as using a photothermal conversion layer, can be used, it is not limited to these.

The heating temperature for carrying out the elimination reaction can be in the range of room temperature (approximately 25 ° C.) to 500 ° C., and the lower limit temperature is the upper limit temperature in consideration of the thermal stability of the material and the boiling point of the elimination component. In view of energy efficiency, the abundance of unconverted molecules, decomposition of the compound after conversion, sublimation, and the like, the range of 40 to 500 ° C. is preferable, and more preferably 60 in consideration of the thermal stability of the synthesis of the precursor. It is in the range of from ° C to 500 ° C, particularly preferably from 80 ° C to 400 ° C.
Regarding the heating time, the higher the temperature, the shorter the reaction time, and the lower the temperature, the longer the time required for the elimination reaction. Further, although depending on the reactivity and amount of the precursor, it is usually 0.5 to 120 minutes, preferably 1 to 60 minutes, particularly preferably 1 minute to 30 minutes.

  When light is used as an external stimulus, an infrared lamp, irradiation with light having a wavelength absorbed by the compound (for example, exposure to a wavelength of 405 nm or less), and the like may be used. At that time, a semiconductor laser may be used. For example, near-infrared laser light (usually laser light having a wavelength of around 780 nm), visible laser light (usually laser light having a wavelength in the range of 630 nm to 680 nm), and laser light having a wavelength of 390 to 440 nm can be mentioned. Laser light having a wavelength of 390 to 440 nm is particularly preferable, and semiconductor laser light having an oscillation wavelength in the range of 440 nm or less is preferably used. Among them, as a preferable light source, a blue-violet semiconductor laser light having an oscillation wavelength in the range of 390 to 440 (more preferably 390 to 415 nm) and an infrared semiconductor laser light having a central oscillation wavelength of 850 nm are half wavelength using an optical waveguide device. And blue-violet SHG laser light having a central oscillation wavelength of 425 nm.

  The above acid or base acts as a catalyst for elimination reaction, and conversion at a lower temperature is possible. Although there is no particular limitation on the method of using these, they may be added as they are, or they may be dissolved in an arbitrary solvent and added as a solution, or they may be vaporized and subjected to heat treatment in the atmosphere. Alternatively, a photoacid generator, a photobase generator, or the like may be added, and an acid and a base may be obtained in the system by light irradiation.

As the acid, 2-butyloctanoic acid such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, formic acid, phosphoric acid and the like can be used.
Examples of the base include hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium hydrogen carbonate, sodium carbonate and potassium carbonate, amines such as triethylamine and pyridine, diazabicycloundecene, diazabicyclononene. Amidines such as can be used.

  Examples of the photoacid generator include ionic generators such as sulfonium salts and iodonium salts and nonionic generators such as ionic photoacid generator imide sulfonate, oxime sulfonate, disulfonyldiazomethane, and nitrobenzyl sulfonate. .

  The π-electron conjugated compound precursor of the present invention is highly soluble in general-purpose solvents such as dichloromethane, tetrahydrofuran, chloroform, toluene, mesitylene, ethyl benzoate, dichlorobenzene, and xylene. Can be converted into ink. Further, after the ink is deposited on the support, the structure that becomes the insulating member can be formed by volatilizing the solvent.

  Examples of the adhesion method to the support include stencil printing method such as screen printing method, intaglio printing method such as gravure printing method, ink jet method, planographic printing method, spin coating method, casting method, dip method, doctor blade method, dispensing method, etc. Known printing methods. In addition, a patterned film or a large-area film can be manufactured by these methods, and the film thickness can be appropriately adjusted by changing the ink concentration or the adhesion amount. An optimal printing method and solvent combination may be selected depending on the device to be manufactured.

  The member using the π-electron conjugated compound precursor of the present invention thus obtained is converted into an organic semiconductor material represented by the general formula (II) by an external stimulus including heat treatment, and converted into an electronic device. Use. It is also possible to pattern the semiconductor region and the insulator region by locally applying energy and partially converting from general formula (I) to general formula (II).

Furthermore, the fact that the highly soluble π-electron conjugated compound precursor of the present invention can be converted to a π-electron conjugated compound represented by the general formula (II) with low solubility is very advantageous in the device manufacturing process. After conversion to the organic semiconductor material represented by the general formula (II), it becomes easier to further form an insulating material, an electrode material, etc. on it using a wet process, thereby suppressing process damage due to subsequent processes. Is possible.
Since these thin films, thick films, or crystals function as charge transporting members for various functional elements such as photoelectric conversion elements, thin film transistors (TFT) elements, and light emitting elements, the π electron conjugated compound precursor of the present invention is used. A variety of organic electronic devices can be fabricated.

  Here, specific examples will be disclosed and described for easy understanding of the conversion from the dithienobenzothiophene derivative precursor used in the present invention. However, although a specific example is shown below, it is not limited to this.

  About the conversion process from the dithienobenzothiophene derivative precursor used by this invention, a conversion process can be monitored from a weight change and an exothermic / endothermic peak by TG-DTA measurement (SII company make: TG / DTA200), for example.

  When the dithienobenzothiophene derivative precursor (VI) was heated at a rate of 5 ° C./min, the weight loss corresponding to 2 molecules of pentanoic acid was reduced at 190 to 250 ° C. (theoretical reduction amount 31.5%, actual reduction amount). Amount 31.4%) was observed. Further, when the temperature was further increased, an endothermic peak was observed at 363 ° C. This coincided with the melting point of the dithienobenzothiophene derivative compound (VII) synthesized separately.

[Conversion film from dithienobenzodithiophene derivative precursor]
An example of a method for manufacturing a conversion film from a dithienobenzothiophene derivative is shown below.
Using a silicon wafer (N-doped) with a thermal oxide film with a thickness of 300 nm as a substrate, cleaning the surface of the oxide film with oxygen plasma, and then spin-coating an N-methylpyrrolidone solution of polyimide resin to a thickness of about 500 nm A polyimide film was formed.
Thereafter, a dithienobenzodithiophene derivative precursor (VI) chloroform solution ink (1 wt%) was spin-coated to obtain a dithienobenzodithiophene derivative precursor film having a thickness of about 100 nm. Thereafter, heating is performed at 230 ° C. for 5 minutes in an inert atmosphere to give external energy, and the dithienobenzodithiophene derivative precursor (VI) and dithienobenzodithiophene derivative (VII) and the elimination component (VIII) ) Was obtained.

Here, the microscope observation photograph of the single crystal of the dithienobenzodithiophene derivative (VII) is shown in FIG. Further, FIG. 2 shows an SEM photograph of an organic film containing a dithienobenzodithiophene derivative (VII) which is a conversion film of the dithienobenzodithiophene derivative precursor (VI) produced by the above production method. For comparison, FIG. 3 shows a SEM photograph of a vacuum deposited film of a dithienobenzodithiophene derivative (VII) as another organic film manufacturing method.
It is clear from out-of-plane / in-plane X-ray diffraction that the thin films of FIGS. 2 and 3 have matching diffraction peaks (not shown). Therefore, it is clear that the conversion film is a film mainly containing the dithienobenzodithiophene derivative (VII).

  As shown in FIG. 1, a single crystal of a dithienobenzodithiophene derivative obtained by solution growth or vapor phase growth has a crystal habit in its production method. For example, dithienobenzodithiophene derivative (VII) is a plate-like crystal and has an angle of θ1 = about 130 degrees. This is an angle that can be estimated from the crystal lattice of a single crystal of the dithienobenzodithiophene derivative (VII).

In the conversion film from the dithienobenzodithiophene derivative precursor used in the present invention in FIG. 2, domains in the same direction are formed, and cracks or crystal habits due to precursor conversion are visible.
It has an angle of θ2 = about 130 degrees, which means that it is a conversion film from the dithienobenzodithiophene derivative precursor used in the present invention. It is clear that the vacuum-deposited film of the dithienobenzodithiophene derivative (VII) shown in FIG. 3 is different, and there are differences in the size of the domain, the shape of the domain, and the angle formed by the domain. Moreover, the organic film manufactured by this invention has a different characteristic (for example, transistor characteristic) from a vacuum evaporation film.

  As described above, the organic film converted from the dithienobenzodithiophene derivative precursor used in the present invention to the dithienobenzodithiophene derivative may be different from the film manufactured by another method such as vacuum deposition. It can be easily determined from the shape of the membrane and various analysis methods whether it is a conversion membrane used in the present invention.

Examples of the energy applied to perform the elimination reaction include heat, light, and electromagnetic waves. From the viewpoints of reactivity, yield, and post-treatment, thermal energy or light energy is desirable, and thermal energy is particularly preferable. Moreover, you may apply the said energy in presence of an acid or a base.
Usually, the elimination reaction depends on the structure of the functional group, but often requires heating.
The heating method for carrying out the elimination reaction includes a method of heating on a support, a method of heating in an oven, a method of irradiation with microwaves, a method of heating by converting light into heat using a laser, Although various methods, such as using a photothermal conversion layer, can be used, it is not limited to these.
The heating temperature for carrying out the elimination reaction can be in the range of room temperature (approximately 25 ° C.) to 500 ° C., and the lower limit temperature is the upper limit temperature in consideration of the thermal stability of the material and the boiling point of the elimination component. In view of energy efficiency, the abundance of unconverted molecules, decomposition of the compound after conversion, sublimation, and the like, the range of 40 to 500 ° C. is preferable, and more preferably 60 in consideration of the thermal stability of the synthesis of the precursor. It is in the range of from ° C to 500 ° C, particularly preferably from 80 ° C to 400 ° C.
Regarding the heating time, the higher the temperature, the shorter the reaction time, and the lower the temperature, the longer the time required for the elimination reaction. Further, although depending on the reactivity and amount of the precursor, it is usually 0.5 to 120 minutes, preferably 1 to 60 minutes, particularly preferably 1 minute to 30 minutes.
When light is used as an external stimulus, an infrared lamp, irradiation with light having a wavelength absorbed by the compound (for example, exposure to a wavelength of 405 nm or less), and the like may be used. At that time, a semiconductor laser may be used. For example, near-infrared laser light (usually laser light having a wavelength of around 780 nm), visible laser light (usually laser light having a wavelength in the range of 630 nm to 680 nm), and laser light having a wavelength of 390 to 440 nm can be mentioned. Laser light having a wavelength of 390 to 440 nm is particularly preferable, and semiconductor laser light having an oscillation wavelength in the range of 440 nm or less is preferably used. Among them, as a preferable light source, a blue-violet semiconductor laser light having an oscillation wavelength in the range of 390 to 440 (more preferably 390 to 415 nm) and an infrared semiconductor laser light having a central oscillation wavelength of 850 nm are half wavelength using an optical waveguide device. And blue-violet SHG laser light having a central oscillation wavelength of 425 nm.

As described above, the above acid or base acts as a catalyst for elimination reaction, and conversion at a lower temperature is possible. Although there is no particular limitation on the method of using these, they may be added as they are, or they may be dissolved in an arbitrary solvent and added as a solution, or they may be vaporized and subjected to heat treatment in the atmosphere. Alternatively, a photoacid generator, a photobase generator, or the like may be added, and an acid and a base may be obtained in the system by light irradiation.
As the acid, 2-butyloctanoic acid such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, formic acid, phosphoric acid and the like can be used.
Examples of the base include hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium hydrogen carbonate, sodium carbonate and potassium carbonate, amines such as triethylamine and pyridine, diazabicycloundecene, diazabicyclononene. Amidines such as can be used.
Examples of the photoacid generator include ionic generators such as sulfonium salts and iodonium salts and nonionic generators such as ionic photoacid generator imide sulfonate, oxime sulfonate, disulfonyldiazomethane, and nitrobenzyl sulfonate. .

[Electronic device]
The specific compound of this invention can be used for an electronic device, for example. An example of an electronic device is a device that has two or more electrodes, the current flowing between the electrodes and the voltage generated are controlled by electricity, light, magnetism, chemical substances, etc., or the applied voltage or current Thus, a device that generates light, an electric field, or a magnetic field can be used. In addition, for example, an element that controls current or voltage by application of voltage or current, an element that controls voltage or current by application of a magnetic field, an element that controls voltage or current by the action of a chemical substance, or the like can be given. Examples of this control include rectification, switching, amplification, and oscillation.
Corresponding devices currently implemented with inorganic semiconductors such as silicon include resistors, rectifiers (diodes), switching elements (transistors, thyristors), amplifier elements (transistors), memory elements, chemical sensors, etc., or these elements Combinations and integrated devices. In addition, a solar cell that generates an electromotive force by light, or an optical element such as a photodiode or a phototransistor that generates a photocurrent can be used.
An example of an electronic device suitable for applying the specific compound of the present invention is a field effect transistor (FET). Hereinafter, this FET will be described in detail.

"Transistor structure"
4A to 4D are schematic structures of the organic thin film transistor according to the present invention.
The organic semiconductor layer (1) of the organic thin film transistor according to the present invention contains the specific compound of the present invention. In the organic thin film transistor of the present invention, a gate electrode (4) is provided on a spatially separated source electrode (2), drain electrode (3) and a support (substrate) (not shown). ) And an organic semiconductor layer (1), an insulating film (5) may be provided. In the organic thin film transistor, the current flowing in the organic semiconductor layer (1) between the source electrode (2) and the drain electrode (3) is controlled by applying a voltage to the gate electrode (4).
The organic thin film transistor of the present invention can be provided on a support, and for example, a commonly used substrate such as glass, silicon, or plastic can be used. In addition, by using a conductive substrate, it can also be used as a gate electrode, and a structure in which a gate electrode and a conductive substrate are stacked can be used. However, the flexibility of a device to which the organic thin film transistor of the present invention is applied. When characteristics such as light weight, low cost, and impact resistance are desired, a plastic sheet is preferably used as the support.
Examples of the plastic sheet include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate, cellulose triacetate, and cellulose acetate propionate. Is mentioned.

“Film Formation Method: Organic Semiconductor Layer”
(Ink composition, solvent)
The solvent used in the ink composition of the present invention can be determined as follows.
For example, a thin film can be formed by dissolving in a solvent such as dichloromethane, tetrahydrofuran, chloroform, toluene, chlorobenzene, dichlorobenzene, and xylene and coating on a support. That is, the solvent for the coating solution containing the precursor can be appropriately selected according to the purpose, but it is preferable that the boiling point is 500 ° C. or less because it is easy to remove. However, the higher the volatility, the better. Those having a boiling point of 50 ° C. or higher are preferred. Although not fully confirmed, it may be because conductivity is not only the detachment of the leaving group of the precursor, but also the change of the arrangement state for contact between molecules. In other words, the precursor present in the coating film is removed from the random state and then adjoined, contacted, or regenerated between the molecules by at least a partial change in the direction or position of the molecule from the random state. This may be because it takes time for the arrangement, aggregation, crystallization, and the like to occur.
In any case, specific examples of the solvent include alcohols such as methanol, ethanol, isopropanol, etc., ethylene glycol, diethylene glycol, propylene glycol, which have affinity for the polar carboester group as the leaving group, for example. Such as glycol, tetrahydrofuran (THF), ether such as dioxane, ketones such as methyl ethyl ketone and methyl isobutyl ketone, phenols such as phenol and cresol, nitrogen-containing organic solvents such as dimethylformamide (DMF), pyridine, dimethylamine and triethylamine In addition to polar (water-miscible) solvents such as Cellosolve (registered trademark) such as methyl cellosolve and ethyl cellosolve, hydrocarbons such as toluene, xylene, benzene, etc., which are relatively compatible with the main body structure, Halogenated hydrocarbon solvents such as carbon fluoride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, ester solvents such as methyl acetate and ethyl acetate, nitromethane And nitrogen-containing organic solvents such as nitroethane. These may be used alone or in combination of two or more.
Among them, polar (water-miscible) solvents such as tetrahydrofuran (THF) and halogenated hydrocarbons such as toluene, xylene, benzene, methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride, and ester systems such as ethyl acetate A combination with a non-water miscible solvent such as a solvent is particularly preferred.
Further, the ink liquid (coating liquid) may further contain a volatile or self-decomposable acid or base material for accelerating the decomposition of the carboester group without impairing the achievement of the object of the present invention. Good. Further, a strongly acidic solvent such as trichloroacetic acid (decomposed into chloroform and carbon dioxide by heating) and trifluoroacetic acid (volatile) is preferably used because it has an effect of expelling a carboester group which is a weak Lewis acid.

[Dopant]
The dopant that can be used in the present invention may be either an oxidized or reduced conductivity imparting agent, or both. When using both, it is preferable that the source electrode and the drain electrode are formed of the same type of conductivity-imparting agent.
Here, the oxidation-type conductivity imparting agent has an effect of improving electrical conductivity by oxidizing the organic semiconductor film by acting on the organic semiconductor film, and is a p-type conductivity imparting agent. There is also. On the other hand, the reduced-type conductivity imparting agent is an agent that reduces the organic semiconductor film to improve electrical conductivity, and is sometimes referred to as an n-type conductivity imparting agent.
Examples of the oxidized conductivity imparting agent used in the present invention include acids such as oxygen, hydrochloric acid, sulfuric acid, and sulfonic acid, Lewis acids such as PF6, AsF5, FeCl3, and SbF5, iodine, chlorine, bromine, ICl, ICl3, and IBr. , Halogens such as IF3, HF, HC1, HNO3, H2SO4, HClO4, FSO3H, ClSO3H, CF3SO3H and other protic acids, acetic acid, formic acid, organic acids such as amino acids, FeCl3, FeOCl, TiCl4, ZrCl4, HfCl4, NbF5, NbCl5, Transition metal compounds such as TaCl5, MoCl5, WF5, WCl6, UF6, LnCl3 (Ln = La, Ce, Nd, Pr, and other lanthanoids and Y), Cl-, Br-, I-, ClO4-, PF6-, AsF5 -, SbF6-, BF4-, sulfonate anion, etc. Or the like can be mentioned the quality anion.
On the other hand, examples of the reduction-type conductivity imparting agent include hydrogen, lithium, sodium, potassium, rubidium, cesium and other alkali metals, barium, calcium, magnesium, silver, europium, beryllium and other metal atoms, atomic groups, and the like. .
In addition, electrons such as materials with functional groups such as acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, benzoquinone derivatives, tetracyanoethylene and tetracyanoquinodimethane and their derivatives Acceptable acceptor materials, materials having functional groups such as amino group, triphenyl group, alkyl group, hydroxyl group, alkoxy group, phenyl group, substituted amines such as phenylenediamine, anthracene, benzoanthracene, substituted benzoanthracene A material that serves as a donor which is an electron donor, such as a group, pyrene, substituted pyrene, carbazole and derivatives thereof, and tetrathiafulvalene and derivatives thereof may be used as a dopant.

  As long as the effects obtained by the composition of the present invention are not impaired, other additives as appropriate, for example, carrier generating agents, conductive materials, viscosity modifiers, surface tension modifiers, leveling agents, penetrating agents, wetting preparation agents, rheology A regulator or the like may be added.

(Concentration, ratio)
The addition amount of the precursor in the ink composition of the present invention is usually 0.01 wt% to 50 wt%, preferably 0.05 wt% to 10 wt%, more preferably 0.1 wt% to 5 wt%. It is good to use in the range.
The addition amount of the dopant in the ink composition of the present invention is usually 10 mol% or less, preferably 5 mol% or less, more preferably 0.1 mol% in terms of a molar ratio with respect to the π-electron conjugated compound precursor. It is good. The ink composition of the present invention may contain other additives, but the effects of the present invention can be obtained even if the additive is not contained.
The composition of the present invention can be prepared by, for example, dissolving or dispersing an organic semiconductor material and a dopant in a solvent so as to have the above content, and performing heat treatment and stirring according to the solubility of each material. The preparation method is not limited to this. Further, as described above, other additives may or may not be used. When the other additives are added, they may be added as appropriate so as not to leave undissolved components, or undissolved components may be removed by a treatment such as filtration.

(Film thickness etc.)
The organic semiconductor film of the present invention is a thin film formed from the ink composition of the present invention, and is one component of the semiconductor element. The thickness of the semiconductor thin film is preferably as thin as possible without impairing necessary functions, and is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, and more preferably 1 nm to 1 μm.

[Conversion process]
The organic semiconductor film can be formed by applying external energy to a film made of a precursor and converting the precursor into a semiconductor. The preparation of the precursor film and the organic semiconductor thin film can be appropriately selected depending on the purpose, such as in an air atmosphere, water vapor, reduced pressure, vacuum, an inert gas atmosphere such as nitrogen or argon, or an active gas atmosphere such as hydrogen. However, a simple atmospheric atmosphere is preferable. After the preparation of the precursor film and the organic semiconductor film, a step of removing the solvent may be performed. The solvent removal step can be appropriately selected depending on the purpose, such as heat treatment by heating, natural drying in a dry gas atmosphere or air atmosphere, but simple natural drying is preferable.

[Printing method, wet process]
As described above, these organic semiconductor thin film production methods include screen printing, spray coating, spin coating, blade coating, dip coating, casting, roll coating, bar coating, die coating, and inkjet. And a suitable solvent is selected from the above-mentioned film forming method and the above solvent according to the material.

  In the organic thin film transistor of the present invention, the organic semiconductor layer formed using the above compound as a component is formed in contact with the source electrode, the drain electrode, and the insulating film.

〔electrode〕
The gate electrode, source electrode, and gate electrode used in the organic thin film transistor of the present invention are not particularly limited as long as they are conductive materials, such as platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony, lead, Tantalum, indium, aluminum, zinc, magnesium, etc., and their alloys and conductive metal oxides such as indium / tin oxide, or inorganic and organic semiconductors whose conductivity has been improved by doping, such as silicon single crystals, Examples thereof include polysilicon, amorphous silicon, germanium, graphite, polyacetylene, polyparaphenylene, polythiophene, polypyrrole, polyaniline, polythienylene vinylene, polyparaphenylene vinylene, a complex of polyethylenedioxythiophene and polystyrene sulfonic acid.

The source electrode and the drain electrode are preferably those having low electrical resistance at the contact surface with the semiconductor layer among the above-described conductivity.
As a method for forming an electrode, a method of forming an electrode using a known photolithographic method or a lift-off method, using a conductive thin film formed by a method such as vapor deposition or sputtering using the above materials as a raw material, a metal such as aluminum or copper There is a method of etching using a resist by thermal transfer, ink jet or the like on a foil. Alternatively, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by inkjet, or may be formed from the coating film by lithography, laser ablation, or the like. Furthermore, a method of patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as a relief printing plate, an intaglio printing plate, a planographic printing plate or a screen printing method can also be used.
Moreover, the organic thin-film transistor of this invention can provide the extraction electrode from each electrode as needed.

[Insulating film]
Various insulating film materials can be used for the insulating film used in the organic thin film transistor of the present invention. For example, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, tantalum oxide, tin oxide, vanadium oxide, barium strontium titanate, zirconium barium titanate, lead zirconate titanate, lead lanthanum titanate, titanate Examples thereof include inorganic insulating materials such as strontium, barium titanate, barium magnesium fluoride, bismuth tantalate niobate, and yttrium trioxide.
Further, for example, polymer compounds such as polyimide, polyvinyl alcohol, polyvinylphenol, polyester, polyethylene, polyphenylene sulfide, unsubstituted or halogen atom-substituted polyparaxylylene, polyacrylonitrile, cyanoethyl pullulan, and the like can be used.
Further, two or more of the above insulating materials may be used in combination. The material is not particularly limited, but a material having a high dielectric constant and a low electrical conductivity is preferable.
Examples of the method for producing the insulating film layer using the above materials include a CVD method, a plasma CVD method, a plasma polymerization method, a dry process such as a vapor deposition method, a spray coating method, a spin coating method, a dip coating method, an ink jet method, and a cast method. Examples thereof include wet processes such as coating, blade coating, and bar coating.

[Modification of organic semiconductor / insulating film interface such as HMDS]
In the organic thin film transistor of the present invention, an organic thin film may be provided between these layers for the purpose of improving the adhesion between the insulating film and the organic semiconductor layer, reducing the gate voltage, and reducing the leakage current. The organic thin film is not particularly limited as long as it does not chemically affect the organic semiconductor layer. For example, an organic molecular film or a polymer thin film can be used.

  Examples of the organic molecular film include a coupling agent using octyltrichlorosilane, octadecyltrichlorosilane, hexamethylenedisilazane, phenyltrichlorosilane and the like as specific examples. As the polymer thin film, the above-described polymer insulating film materials can be used, and these may function as a kind of insulating film. The organic thin film may be subjected to an anisotropic treatment by rubbing or the like.

[Modification of organic semiconductor / electrode interface, such as thiol]
For the purpose of controlling the wettability of the electrode surface and improving the electrical contact with the organic semiconductor layer, a surface treatment of the electrode may be performed in advance. Examples of the surface treatment material include thiol compounds, and specific examples include saturated or unsaturated alkyl thiols, perfluoroalkyl thiols, and substituted or unsubstituted benzene thiols. In addition, a charge injection layer may be provided as appropriate.

[Protective layer]
The organic transistor of the present invention is stably driven even in the atmosphere, but a protective layer is used as necessary for protection from mechanical destruction, protection from moisture and gas, or protection for device integration. Can also be provided.

[Applied devices]
The organic thin film transistor of the present invention described above can be suitably used as an element for driving various conventionally known display image elements such as liquid crystal, electroluminescence, electrochromic, electrophoresis, and so on. It is possible to produce a display called “paper”.

  The display device of the present invention includes, for example, a liquid crystal display element in a liquid crystal display device, an organic or inorganic electroluminescence display element in an EL display device, and a display element such as an electrophoretic display element in an electrophoretic display device as one display pixel. A plurality of display elements are arranged in a matrix in the X and Y directions. The display element includes the organic thin film transistor of the present invention as a switching element for applying a voltage or supplying a current to the display element. The display device of the present invention includes a plurality of the switching elements corresponding to the number of the display elements, that is, the number of display pixels.

  The display element includes, in addition to the switching element, for example, a substrate, an electrode such as a transparent electrode, a polarizing plate, a color filter, and the like. Can be appropriately selected, and conventionally known ones can be used.

When the display device forms a predetermined image, for example, the switching elements arbitrarily selected from the switching elements arranged in a matrix form apply voltage or current to the corresponding display elements. By configuring the switch to be turned on or off only when supplying, and to be turned off or on at other times, the display device can display at high speed and with high contrast. As an image display operation in the display device, an image or the like is displayed by a conventionally known display operation.
For example, in the case of the liquid crystal display element, an image or the like is displayed by applying a voltage to the liquid crystal to control the molecular arrangement of the liquid crystal. In the case of the organic or inorganic electroluminescence display element, an image or the like is displayed by supplying a current to a light emitting diode formed of an organic or inorganic film to cause the organic or inorganic film to emit light. In the case of the electrophoretic display element, for example, a voltage is applied to white and black colored particles charged to different polarities, and the particles are electrophoresed between electrodes in a predetermined direction to generate an image or the like. Is displayed.

  The display device can be manufactured by a simple process such as coating and printing of the switching element, and can use a substrate that cannot withstand high-temperature processing such as a plastic substrate or paper, and can be a large-area display. However, the switching element can be fabricated with energy saving and low cost.

  Further, an IC in which the organic thin film transistor of the present invention is integrated can be used as a device such as an IC tag.

  EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples, but these examples are for explaining the basics of the present invention and are not intended to limit the present invention. In the following examples, “parts” and “%” represent “parts by weight” and “% by weight” unless otherwise specified.

[Example 1]
The ink shown in Table 1 was prepared using the dithienobenzothiophene derivative precursor (VI). Toluene was used as the solvent, and acceptor organic material F4TCNQ (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the dopant.

  The ink was spread on the substrate by the following method to prepare a mixed film of precursor and dopant. A silicon wafer with a thermal oxide film having a thickness of 300 nm was used as the substrate. After cleaning the surface of the oxide film by UV ozone treatment, polyimide (CT4112) made by Kyocera Chemical was applied to form a polyimide film. Thereafter, the ink was spread on a substrate by a spin coating method to form a mixed film of a precursor and a dopant.

The film | membrane obtained above was heated with the hotplate in a glove box, the precursor was converted, and the organic-semiconductor film | membrane was obtained. FIG. 5 shows polarized micrographs of Samples 1 to 4.
Sample 1 is an organic film prepared from an ink of dithienobenzothiophene derivative precursor (VI) alone. The region where the brightness appears different is one crystal domain, and this compound is characterized by the formation of a relatively large crystal domain, which is one reason why the mobility is improved.
On the other hand, it can be confirmed that Sample 2 has a region having a different film quality from Sample 1.
This is probably because F4TCNQ used as a dopant aggregated, and as a result of F4TCNQ being a source of crystal nuclei, a microcrystalline aggregate film was formed. For Samples 3 and 4, it can be confirmed that the same film as Sample 1 can be formed.

A counter electrode having a gap of 200 μm was formed on the film obtained above using a vacuum deposition method. Ag was used as the electrode material, and a film thickness of 50 nm was formed. Thereafter, under a vacuum of 1E-2 Pa or less, a voltage was applied between the counter electrodes, the current was measured, and the conductivity was measured. B1500 made by Agilent Technologies was used as a measuring instrument. The measurement results are shown in FIG. 6 and the conductivity obtained by calculation is shown in Table 2.
From FIG. 6, it can be seen that the current value linearly changes with respect to the applied voltage, and that it behaves ohmic. It can be seen that the obtained conductivity tends to increase as the dopant concentration decreases. Compared to the undoped sample, the doped sample is presumed to have higher conductivity as a result of improved carrier density. However, the higher the doping concentration, the more dopants as impurities, so that the large crystal growth was inhibited in Sample 2, and the carrier movement was limited in Sample 3 due to the effect of impurity scattering. It is presumed that the effect of is reduced. As a result, it is considered that the sample 4 most effectively achieved both the improvement of the carrier density by doping and the mobility, and the highest conductivity.

[Example 2]
Inks shown in Table 3 were prepared in the same manner as in Example 1 except that FeCl ₃ (manufactured by Kanto Chemical Co., Inc.), which is a Lewis acid, was used as a dopant.

Thereafter, in the same manner as in Example 1, after forming the semiconductor film, the counter electrode was formed and the conductivity was measured. FIG. 7 shows the result of observation with a polarizing microscope, FIG. 8 shows the result of current / voltage measurement, and Table 4 shows the conductivity.
As a result of observation with a polarizing microscope, in Sample 5, the dithienobenzothiophene derivative precursor is not converted (it may be damaged because the dopant is an acid), or it is an aggregate film of microcrystals. I understand that. Therefore, the conductivity of sample 5 was lower than that of sample 1.
On the other hand, samples 6 and 7 show a significant improvement in conductivity, and sample 7 has a lower conductivity.
This is the reverse trend of Example 1, but the cause is that the dopant size is small, so the influence of impurity scattering is small, and the higher the doping concentration, the higher the conductivity. Guessed.

1 organic semiconductor layer 2 source electrode 3 drain electrode 4 gate electrode 5 insulating film 6 substrate

Japanese Patent Application No. 2009-171441 JP 2009-275032 A Japanese Patent Application No. 2010-061591 Japanese Patent Application No. 2010-135664 Specification JP 2007-266298 A JP 2006-032914 A

J. et al. Am. Chem. Soc. 124, p8812 (2002) Appl. Phys. Lett. 84, p2085 (2004) J. et al. Am. Chem. Soc. 126, p1596 (2004) Appl. Phys. Lett. 91, p053508 (2007) Supervised by Noboru Ono “High performance of low molecular organic semiconductors” p139 Science & Technology Co., Ltd.

Claims (5)

An ink composition for electronic devices, comprising at least a π-electron conjugated compound precursor, a dopant for the π-electron conjugated compound, and a solvent for dissolving the π-electron conjugated compound precursor and the dopant ,
The π-electron conjugated compound precursor consists dithienothiophene benzothiophene derivative represented by the following structural formula (VI), the hydrogen and -O-CO-C ₅ H ₁₁ from the π electron conjugated compound precursor The dithienobenzothiophene derivative represented by the following general formula (VII) is obtained by elimination,
The dopant is, 2,3,5,6-tetrafluoro -7,7,8,8- tetracyano - quinodimethane (F4TCNQ), and an ink composition characterized in that at least either of the FeCl _3.
The ink composition according to claim 1, wherein a molar concentration of the dopant is 5% or less with respect to a molar concentration of the π-electron conjugated compound precursor. An organic material composed of the dithienobenzothiophene derivative represented by the general formula (VII) by applying an external stimulus after the ink composition according to claim 1 is attached on a support. The manufacturing method of the organic film | membrane characterized by including the process of obtaining a film | membrane.
The method for producing an organic film according to claim 3, wherein the external stimulus is light or thermal energy. A method for producing a field effect transistor comprising the method for producing an organic film according to claim 3.