JP2015065415A - Gate insulation film, organic thin film transistor, and method for manufacturing organic thin film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gate insulation film in which film quality is not changed by heating, chemical treatment and the like for forming electrodes and the like, and which can maintain high flatness when an organic semiconductor layer is formed, and to provide an organic thin film transistor using the gate insulation film, and a method for manufacturing the same.SOLUTION: A gate insulation film is formed by curing: (A) a compound obtained by reacting (a) a dicarboxylate, or a tricarboxylic acid or an acid anhydride thereof and (b) a tetracarboxylic acid or an acid dianhydride thereof, where a molar ratio of a/b is 0.1 to 10, with a compound obtained by reacting a bisphenol type epoxy compound with an ethylenic unsaturated bond group-containing monocarboxylic acid ; (B) a polymerizable monomer having at least one ethylenic unsaturated bond; and (C) a composition containing an epoxy compound. Also provided are An organic transistor in which the composition is applied on a gate electrode and is cured, and a method for manufacturing the same.

Description

  The present invention relates to a gate insulating film, an organic thin film transistor including the same, and a method for manufacturing the organic thin film transistor.

  Organic thin-film transistors can be made lightweight and flexible, and are expected to be applied to next-generation displays with excellent impact resistance and portability. The organic thin film transistor can be used as a semiconductor by applying a soluble low molecular organic semiconductor and a high molecular organic semiconductor. By using the printing method, a large area process can be applied and a significant cost reduction can be expected. Since an organic semiconductor can be formed at a low temperature, there is an advantage that a flexible substrate such as a plastic substrate can be used.

  The field of application of organic thin-film transistors is envisioned for display devices such as organic EL displays, liquid crystals, and electronic paper, RFID tags, sensors, and the like, and research is actively conducted. However, the current organic thin film transistors have not reached a practical level in terms of mobility, operating voltage, and driving stability, and it is urgent to improve from various angles such as not only organic semiconductors but also element configurations and manufacturing processes. It has become.

  As shown in FIGS. 1 and 3, an organic thin film transistor using an organic semiconductor is generally formed so that an organic semiconductor layer and a gate insulating film are in contact with each other. Therefore, it is known that depending on the material constituting the gate insulating film, the semiconductor characteristics of the organic semiconductor layer are affected and the transistor performance is degraded. For example, Patent Document 1 discloses a transistor using a gate insulating layer made of polyimide. However, an organic thin film transistor using a gate insulating layer made of such a material does not stabilize the threshold voltage of the gate voltage. There was a problem.

  As a solution to the above problem, by using a gate insulating film made of cardo type resin described in Patent Document 2, the withstand voltage is improved and the threshold voltage is stabilized. However, the carrier mobility of the organic semiconductor layer, which is an important element of the performance of the organic thin film transistor, is not mentioned. It is known that the carrier mobility of the organic semiconductor layer is affected by the characteristics of the gate insulating film, and there is a concern that the carrier mobility does not become sufficiently high because the characteristics of the gate insulating film are not sufficient.

JP 2003-304014 A JP 2008-166537 A

  Since carriers move at the interface between the organic semiconductor layer and the gate insulating film, the flatness of the gate insulating film needs to be increased. However, the film quality of the gate insulating film formed of an organic compound changes due to heating, chemical treatment, etc. in the process of forming the electrode and the like after the film formation, so that the surface roughness is increased and the flatness is significantly reduced. .

  For this reason, as a preferable gate insulating film used for the organic thin film transistor, a thin film can be formed, and it is necessary to have a high flatness even when the organic semiconductor layer is formed after the thin film is formed and after the electrodes are formed. However, there has been no gate insulating film satisfying these characteristics.

  The present invention has been made in view of such problems, and the film quality does not change due to heating, chemical treatment or the like when forming an electrode or the like, and high flatness when forming an organic semiconductor layer. An object is to provide a gate insulating film capable of maintaining the above. In addition, by using a gate insulating film that can maintain high flatness when forming an organic semiconductor layer, an organic thin film transistor that has high carrier mobility and can exhibit stable transistor characteristics, and a method for manufacturing the same are disclosed. The purpose is to provide. Note that the material for the highly flat insulating film can also be applied to the flattening film when a flattening film is required in the structure of the organic transistor.

As a result of intensive studies on means for solving the above problems, the present inventors have been able to produce a gate insulating film capable of sufficiently maintaining flatness when forming an organic semiconductor layer by using a predetermined composition. The present invention was completed.
That is, the gist of the present invention is as follows.

  (1) The present invention relates to (A) a compound obtained by reacting a bisphenol type epoxy compound with an ethylenically unsaturated bond group-containing monocarboxylic acid, a) dicarboxylic acid or tricarboxylic acid or acid anhydride thereof, and b ) A compound obtained by reacting tetracarboxylic acid or its acid dianhydride in a range where the molar ratio of a / b is 0.1 to 10, and (B) having at least one ethylenically unsaturated bond. A gate insulating film obtained by curing a composition containing a polymerizable monomer and (C) an epoxy compound.

  (2) The present invention also provides the gate insulating film according to (1), wherein the composition further contains (D) a photopolymerization initiator.

  (3) The present invention also provides at least one gate electrode, at least one source electrode, at least one drain electrode, at least one organic semiconductor layer, and the gate insulating film according to (1) or (2) It is an organic thin-film transistor characterized by including these.

  (4) The present invention is also the organic thin film transistor according to (3), wherein the thickness of the gate insulating film is 0.05 to 1.0 μm.

(5) The present invention is also a method for manufacturing an organic thin film transistor including at least one gate electrode, at least one source electrode, at least one drain electrode, at least one organic semiconductor layer, and a gate insulating film. And
A film of 0.05 to 1.0 μm is formed by applying the composition described in (1) or (2) on the gate electrode and performing UV exposure and subsequent heat curing at a temperature of 150 to 200 ° C. A method of manufacturing an organic thin film transistor, wherein a gate insulating film is formed with a thickness.

  According to the present invention, it is possible to produce a gate insulating film that can maintain high flatness when forming an organic semiconductor layer, to improve the carrier mobility of the organic thin film transistor, and to exhibit stable transistor characteristics.

1 is a cross-sectional configuration diagram illustrating an example of an organic thin film transistor according to Embodiment 1. FIG. It is explanatory drawing of the manufacturing method of the organic thin-film transistor which concerns on Embodiment 1. FIG. FIG. 2I is a diagram showing an example of the gate electrode formation process. FIG. 2 (ii) is a diagram illustrating an example of a polymer gate insulating film forming process. FIG. 2 (iii) shows an example of the source / drain electrode formation step. FIG. 2 (iv) shows an example of the organic semiconductor layer forming step. 5 is a cross-sectional configuration diagram illustrating an example of an organic thin film transistor according to Embodiment 2. FIG. It is a change characteristic figure of the square root of drain current and drain current to gate voltage of an organic thin film transistor concerning Examples 1 and 2 and comparative example 1. It is the figure which showed the measurement result of the flatness in the gate insulating film of the organic thin-film transistor which concerns on Example 4, 5 and the comparative example 4. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

Embodiment 1
FIG. 1 is a cross-sectional configuration diagram illustrating an example of an organic thin film transistor according to Embodiment 1 of the present invention. In FIG. 1, the organic thin film transistor according to the first embodiment includes an insulating substrate 10, a gate electrode 20, a gate insulating film 30, a source electrode 40, a drain electrode 41, and an organic semiconductor layer 50.

  In FIG. 1, a gate electrode 20 is formed on an insulating substrate 10 and a gate insulating film 30 is formed on the gate electrode 20. The source electrode 40 and the drain electrode 41 are formed on the surface of the gate insulating film 30 so as to cover both ends of the gate electrode 20 in a top view. An organic semiconductor layer 50 is formed on the gate insulating film 30 between the source electrode 40 and the drain electrode 41, and the organic semiconductor layer 50 covers the inner ends of the source electrode 40 and the drain electrode 41. ing. The structure shown in FIG. 1 is a structure called a bottom gate / bottom contact structure.

  The insulating substrate 10 may be composed of various substrates made of an insulating material. For example, a glass substrate such as quartz glass or silica glass, polyethersulfone (PES), polyethylene naphthalate (PEN), polyimide (PI), A plastic film having a heat resistant temperature (glass transition temperature) of 150 ° C. or higher such as polyetherimide (PEI) can be used. Further, a metal foil or the like can be used as the insulating substrate 10 as long as the surface is treated with an insulating treatment.

  The material of the gate electrode 20 is not limited as long as current can flow efficiently. For example, it may be made of aluminum. Although the gate insulating film 30 is formed on the surface of the gate electrode 20, the surface of the gate electrode 20 is preferably as high in surface smoothness as possible in order to form the stacked gate insulating film 30.

  The gate insulating film 30 is a film that covers the periphery of the gate electrode 20 and insulates the gate electrode 20. The gate insulating film 30 of the organic thin film transistor according to the present embodiment includes (A) a compound obtained by reacting a bisphenol type epoxy compound and an ethylenically unsaturated bond group-containing monocarboxylic acid, a) dicarboxylic acid or tricarboxylic acid, or The acid anhydride, and b) a compound obtained by reacting a tetracarboxylic acid or an acid dianhydride in a range where the molar ratio of a / b is 0.1 to 10, (B) at least one compound A composition comprising a polymerizable monomer having an ethylenically unsaturated bond and (C) an epoxy compound is cured, and further (D) when photocuring and photoprocessing by photolithography. It is a gate insulating film formed by curing a composition containing a photopolymerization initiator.

  In the organic thin film transistor, when a voltage is applied to the gate electrode 20, a channel is formed in the organic semiconductor layer 50, and the generated carriers move between the source electrode 40 and the drain electrode 41, thereby conducting the transistor operation. Do. Carriers generated when a voltage is applied to the gate electrode 20 move on the interface between the gate insulating film 30 and the organic semiconductor layer 50. Therefore, if the gate insulating film 30 has irregularities, the moving speed becomes slow and the carrier mobility decreases. Therefore, the gate insulating film 30 is required to be flat.

  The gate insulating film 30 of the present invention can form a desired pattern by exposure and development, and can form a film having very high flatness with less unevenness by thermosetting. The gate insulating film 30 has little change in flatness even after the source electrode 40 and the drain electrode 41 are formed on the surface thereof. Therefore, an organic semiconductor layer with favorable carrier mobility can be formed. That is, according to the present invention, it is possible to improve the carrier mobility of the organic thin film transistor and to exhibit stable transistor characteristics. Here, the reason why the carrier mobility is improved is that a highly flat gate insulating film can be obtained by using a predetermined composition for a gate insulating film, and carriers may be trapped in the insulating film. This is probably due to the fact that the amount of functional groups such as carboxyl groups is small.

  If the withstand voltage of the gate insulating film 30 is lower than the withstand voltage required for the actual circuit, the organic thin film transistor cannot be operated as a device in the actual circuit. For example, since a display drive circuit needs to be driven at 20 V, it is required to reduce the thickness of the operable gate insulating film 30 and withstand voltage. Since the gate insulating film of the present invention can form a thin film of 1 μm or less and can withstand a voltage of 20 V, it can be driven at a voltage of 20 V or less. On the other hand, the minimum film thickness of the gate insulating film is generally several tens of nanometers, and it is necessary to flatten the unevenness caused by the formation of the gate electrode.

  Thus, in the organic thin film transistor according to the present embodiment, desired flatness and withstand voltage can be obtained by applying the gate insulating film 30 of the present invention.

  (A) in the composition for a gate insulating film of the organic thin film transistor of the present invention is a reaction product of an epoxy compound having two glycidyl ether groups derived from bisphenols and an unsaturated group-containing monocarboxylic acid. , (A) dicarboxylic acid or tricarboxylic acid or acid anhydride thereof, and (b) tetracarboxylic acid or acid dianhydride in a range where the molar ratio of (a) / (b) is 0.1-10. This is an alkali-soluble resin obtained by reaction.

  Examples of bisphenols used as a raw material for (A) include bis (4-hydroxyphenyl) ketone, bis (4-hydroxy-3,5-dimethylphenyl) ketone, bis (4-hydroxy-3,5-dichlorophenyl) ketone, Bis (4-hydroxyphenyl) sulfone, bis (4-hydroxy-3,5-dimethylphenyl) sulfone, bis (4-hydroxy-3,5-dichlorophenyl) sulfone, bis (4-hydroxyphenyl) hexafluoropropane, bis (4-hydroxy-3,5-dimethylphenyl) hexafluoropropane, bis (4-hydroxy-3,5-dichlorophenyl) hexafluoropropane, bis (4-hydroxyphenyl) dimethylsilane, bis (4-hydroxy-3, 5-dimethylphenyl) dimethylsilane, bis (4 Hydroxy-3,5-dichlorophenyl) dimethylsilane, bis (4-hydroxyphenyl) methane, bis (4-hydroxy-3,5-dichlorophenyl) methane, bis (4-hydroxy-3,5-dibromophenyl) methane, 2 , 2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2, , 2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, bis (4-hydroxyphenyl) ether, bis (4-hydroxy-3,5 -Dimethylphenyl) ether, bis (4-hydroxy-3,5-dichlorophenyl) ether, 9, -Bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxy-3-chlorophenyl) fluorene, 9,9-bis (4 -Hydroxy-3-bromophenyl) fluorene, 9,9-bis (4-hydroxy-3-fluorophenyl) fluorene, 9,9-bis (4-hydroxy-3,5-dimethylphenyl) fluorene, 9,9- Bis (4-hydroxy-3,5-dichlorophenyl) fluorene, 9,9-bis (4-hydroxy-3,5-dibromophenyl) fluorene, 4,4′-biphenol, 3,3′-biphenol and the like Derivatives. Among these, those having a 9,9-fluorenyl group are particularly preferably used.

Next, the bisphenols and epichlorohydrin are reacted to obtain an epoxy compound having two glycidyl ether groups. Since this reaction generally involves oligomerization of a diglycidyl ether compound, an epoxy compound of the following general formula (I) is obtained.
(Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a halogen atom or a phenyl group, and A represents —CO—, —SO _2- , -C (CF ₃ ) _2- , -Si (CH ₃ ) _2- , -CH _2- , -C (CH ₃ ) _2- , -O-, a 9,9-fluorenyl group or a direct bond. L is a number from 0 to 10.)

Preferred R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms, and preferred A is a 9,9-fluorenyl group. In addition, since l generally has a plurality of values, the average value is 0 to 10 (not necessarily an integer), but the preferable average value of l is 0 to 3. When the value of l exceeds the upper limit, when the composition for a gate insulating film using an alkali-soluble resin synthesized using the epoxy compound is used, the viscosity of the composition becomes too high and the coating cannot be performed successfully. Or sufficient alkali solubility cannot be imparted, and alkali developability becomes very poor.

Next, the compound of general formula (I) is reacted with acrylic acid or methacrylic acid as an unsaturated group-containing monocarboxylic acid, or both, and the resulting reaction product having a hydroxy group is subjected to (a) dicarboxylic acid or Tricarboxylic acid or its acid anhydride and (b) tetracarboxylic acid or its acid dianhydride are reacted in a range where the molar ratio of (a) / (b) is 0.1 to 10, and the following general formula An alkali-soluble resin having the structure of an epoxy (meth) acrylate acid adduct represented by (II) is obtained.
Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a halogen atom or a phenyl group, and R ₅ represents a hydrogen atom or a methyl group. A represents —CO—, —SO ₂ —, —C (CF ₃ ) ₂ —, —Si (CH ₃ ) ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —, —O—. , 9,9-fluorenyl group or a direct bond, X represents a tetravalent carboxylic acid residue, Y ₁ and Y ₂ each independently represents a hydrogen atom or —OC—Z— (COOH) _m (wherein Z represents a divalent or trivalent carboxylic acid residue, m represents a number of 1 to 2, and n represents a number of 1 to 20.)

  Since this epoxy (meth) acrylate acid adduct (II) is an alkali-soluble resin having both an ethylenically unsaturated double bond and a carboxyl group, it is excellent as (A) of the composition for a gate insulating film of the present invention. Further, it is necessary for providing a cured film having desired physical properties such as withstand voltage and the like, which imparts photocurability, good developability and patterning characteristics.

  (A) Dicarboxylic acid or tricarboxylic acid or acid anhydride thereof used in the epoxy (meth) acrylate acid adduct of general formula (II) which is (A) of the present invention includes a chain hydrocarbon dicarboxylic acid or tricarboxylic acid. An acid or an acid anhydride thereof, an alicyclic dicarboxylic acid or tricarboxylic acid or an acid anhydride thereof, an aromatic dicarboxylic acid or a tricarboxylic acid or an acid anhydride thereof is used. Here, as the chain hydrocarbon dicarboxylic acid or tricarboxylic acid or an acid anhydride thereof, for example, succinic acid, acetyl succinic acid, maleic acid, adipic acid, itaconic acid, azelaic acid, citrate malic acid, malonic acid, glutaric acid, There are compounds such as citric acid, tartaric acid, oxoglutaric acid, pimelic acid, sebacic acid, suberic acid, diglycolic acid and the like, and further, dicarboxylic acid or tricarboxylic acid having an arbitrary substituent introduced therein or an acid anhydride thereof may be used. Examples of the alicyclic dicarboxylic acid or tricarboxylic acid or acid anhydrides thereof include compounds such as cyclobutane dicarboxylic acid, cyclopentane dicarboxylic acid, hexahydrophthalic acid, tetrahydrophthalic acid, norbornane dicarboxylic acid, and more It may be a dicarboxylic acid or a tricarboxylic acid or an acid anhydride having a substituent introduced therein. Furthermore, examples of the aromatic dicarboxylic acid or tricarboxylic acid or acid anhydride thereof include compounds such as phthalic acid, isophthalic acid, trimellitic acid, and the like. An acid anhydride may be used.

  The (b) tetracarboxylic acid or acid dianhydride used in the epoxy (meth) acrylate acid adduct of the general formula (II) which is (A) of the present invention includes a chain hydrocarbon tetracarboxylic acid. Or its acid dianhydride, alicyclic tetracarboxylic acid or its acid dianhydride, or aromatic polyhydric carboxylic acid or its acid dianhydride is used. Here, examples of the chain hydrocarbon tetracarboxylic acid or its acid dianhydride include butanetetracarboxylic acid, pentanetetracarboxylic acid, hexanetetracarboxylic acid, and the like, and further, a tetracarboxylic acid into which a substituent is introduced. Or its acid dianhydride may be sufficient. Examples of the alicyclic tetracarboxylic acid or its acid dianhydride include cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic acid, cyclohexanetetracarboxylic acid, cycloheptanetetracarboxylic acid, norbornanetetracarboxylic acid, Furthermore, a tetracarboxylic acid or an acid dianhydride having a substituent introduced therein may be used. Furthermore, examples of the aromatic tetracarboxylic acid and its acid dianhydride include pyromellitic acid, benzophenone tetracarboxylic acid, biphenyl tetracarboxylic acid, biphenyl ether tetracarboxylic acid, and acid dianhydrides thereof, and further substitution It may be a tetracarboxylic acid having an introduced group or an acid dianhydride thereof.

  (A) dicarboxylic acid or tricarboxylic acid or acid anhydride and (b) tetracarboxylic acid or acid diacid used in the epoxy (meth) acrylate acid adduct of general formula (II) which is (A) of the present invention. The molar ratio (a) / (b) with the anhydride is in the range of 0.1 to 10, preferably 0.2 to 3.0. When the molar ratio (a) / (b) deviates from the above range, the optimum molecular weight cannot be obtained, and in the gate insulating film composition using (A), alkali developability, heat resistance, solvent resistance, pattern shape, etc. Is not preferable because it deteriorates. In addition, there exists a tendency for alkali solubility to become large and molecular weight to become large, so that molar ratio (a) / (b) is small.

  Moreover, it is preferable that the weight average molecular weight (Mw) is between 2000-10000, and the epoxy (meth) acrylate acid adduct of general formula (II) which is (A) of this invention is between 3000-7000. It is particularly preferred. If the weight average molecular weight (Mw) is less than 2000, the adhesion of the pattern during development of the composition for a gate insulating film using (A) cannot be maintained, pattern peeling occurs, and the weight average molecular weight (Mw) If it exceeds 10,000, a development residue and a residual film of an unexposed part are likely to remain. Further, (A) desirably has an acid value in the range of 30 to 200 KOHmg / g. If this value is less than 30 KOHmg / g, alkali development of the gate insulating film composition using (A) cannot be performed well, or special development conditions such as strong alkali are required, and conversely if it exceeds 200 KOHmg / g ( Since the penetration of the alkali developer into the gate insulating film composition using A) becomes too fast and peeling development occurs, neither is preferable.

  The epoxy (meth) acrylate acid adduct of the general formula (II) used in the present invention is described in known methods, for example, JP-A-8-278629 and JP-A-2008-9401, by the above-described steps. It can manufacture by the method of. First, as a method for reacting an unsaturated group-containing monocarboxylic acid with an epoxy compound of the general formula (I), for example, an epoxy group of an epoxy compound and an equimolar amount of an unsaturated group-containing monocarboxylic acid are added to a solvent, In the presence of a catalyst (triethylbenzylammonium chloride, 2,6-diisobutylphenol, etc.), there is a method of reacting by heating and stirring at 90 to 120 ° C. while blowing air. Next, as a method of reacting an acid anhydride with a hydroxyl group of an epoxy acrylate compound as a reaction product, a predetermined amount of an epoxy acrylate compound, an acid dianhydride, and an acid monoanhydride is added to a solvent, and a catalyst (odor In the presence of tetraethylammonium bromide, triphenylphosphine, etc.), the reaction is carried out by heating and stirring at 90 to 130 ° C.

  Examples of the polymerizable monomer (B) having at least one ethylenically unsaturated bond in the composition for a gate insulating film of the present invention include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (Meth) acrylic acid esters having a hydroxyl group such as 2-ethylhexyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di ( (Meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentae Thritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, glycerol (meth) acrylate, sorbitol penta (meth) acrylate, dipentaerythritol penta (meth) acrylate, or dipentaerythritol hexa (Meth) acrylates, sorbitol hexa (meth) acrylates, phosphazene alkylene oxide modified hexa (meth) acrylates, caprolactone modified dipentaerythritol hexa (meth) acrylates and other (meth) acrylic acid esters can be mentioned. 1 type (s) or 2 or more types can be used. Further, the polymerizable monomer having at least one ethylenically unsaturated bond may be one having three or more polymerizable groups and capable of crosslinking molecules of the unsaturated group-containing alkali-soluble resin. preferable. Note that (B) the polymerizable monomer having at least one ethylenically unsaturated bond does not have a free carboxy group.

  (B) Bisphenol obtained by reacting a compound of general formula (I) with acrylic acid or methacrylic acid as an unsaturated group-containing monocarboxylic acid or both as a polymerizable monomer having at least one ethylenically unsaturated bond A type epoxy (meth) acrylate compound can also be used. In that case, A in the general formula (I) is preferably a 9,9-fluorenyl group. When heat curing after exposure and development is performed at a relatively low temperature such as 150 ° C., the ratio of the component (A) to the component (B) is reduced in order to reduce the amount of carboxyl groups remaining after the heat curing. However, in this case, it is effective to use this bisphenol type epoxy (meth) acrylate compound as a part of the component (B). .

  Examples of the (C) epoxy compound in the gate insulating film composition of the present invention include a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a bisphenol S type epoxy resin. At least one epoxy group such as biphenyl type epoxy resin, alicyclic epoxy resin, etc., phenyl glycidyl ether, p-butylphenol glycidyl ether, triglycidyl isocyanurate, diglycidyl isocyanurate, allyl glycidyl ether, glycidyl methacrylate, etc. And the like. When there is a need to increase the crosslinking density of the alkali-soluble resin, a compound having at least two epoxy groups is preferred. In addition, (C) may use only 1 type of compound, and may use it in combination of multiple.

  In the composition for a gate insulating film of the present invention, 20-80% by mass, preferably 30-70% by mass of the alkali-soluble resin (A) is contained in the solid content (including the polymerizable monomer) to be a cured product. . The polymerizable monomer (B) is contained so that the mass ratio (A) / (B) to the alkali-soluble resin (A) is 20/80 to 90/10, preferably 40/60 to 80/20. Is good. However, when bisphenol type epoxy (meth) acrylate is used as a part of the component (B) in order to carry out thermosetting after exposure / development at a lower temperature such as 150 ° C., (A) / (B) It is good to include so that it may become 20 / 80-60 / 40. Moreover, the epoxy compound (C) should contain 5 to 50% by mass, preferably 10 to 40% by mass, in the solid content of the composition. When the alkali-soluble resin is 20% by mass or less as described above, the cured product after photocuring becomes brittle, and the acid value of the coating film is low in the unexposed area, so that the solubility in an alkali developer is lowered. The problem that the pattern edge does not rattle and become sharp is not preferable. On the other hand, when the amount exceeds 80% by mass, the ratio of the photoreactive functional group in the photocuring component ((A) + (B)) is small, and the formation of the crosslinked structure by the photocuring reaction is not sufficient. Even when the acid value of the film is too high, the solubility of the exposed portion in the alkaline developer is increased, so that the formed pattern becomes thinner than the target line width or the pattern is easily lost. This is not preferable because there is a risk of occurrence. Furthermore, when the epoxy compound (C) is less than 5% by mass, the amount of carboxyl groups remaining when a cured film after patterning is formed increases, which may affect the carrier mobility of the gate insulating film. In addition, there is a concern that the moisture resistance reliability of the insulating film cannot be secured, which is not preferable. On the other hand, when the amount is more than 50% by mass, the amount of the photosensitive group in the coating film in the composition for a gate insulating film is decreased, and the sensitivity for patterning may not be sufficiently obtained.

  Examples of the photopolymerization initiator (D) in the gate insulating film composition of the present invention include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, dichloroacetophenone, and trichloroacetophenone. Acetophenones such as p-tert-butylacetophenone, benzophenone, 2-chlorobenzophenone, benzophenones such as p, p'-bisdimethylaminobenzophenone, benzyl, benzoin, benzoin methyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc. Benzoin ethers, 2- (o-chlorophenyl) -4,5-phenylbiimidazole, 2- (o-chlorophenyl) -4,5-di (m-methoxyphenyl) biimidazole, 2- (o-fluorophenyl) -4,5-diphenylbi Biazole compounds such as dazole, 2- (o-methoxyphenyl) -4,5-diphenylbiimidazole, 2,4,5-triarylbiimidazole, 2-trichloromethyl-5-styryl-1,3, 4-oxadiazole, 2-trichloromethyl-5- (p-cyanostyryl) -1,3,4-oxadiazole, 2-trichloromethyl-5- (p-methoxystyryl) -1,3,4- Halomethylthiazole compounds such as oxadiazole, 2,4,6-tris (trichloromethyl) -1,3,5-triazine, 2-methyl-4,6-bis (trichloromethyl) -1,3,5 -Triazine, 2-phenyl-4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (4-chlorophenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine 2- (4-methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (4-methoxynaphthyl) -4,6-bis (trichloroRmethyl) -1, 3,5-tri Azine, 2- (4-methoxystyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (3,4,5-trimethoxystyryl) -4,6-bis (trichloro Halomethyl-S-triazine compounds such as methyl) -1,3,5-triazine, 2- (4-methylthiostyryl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2-octanedione, 1- [4- (phenylthio) phenyl]-, 2- (o-benzoyloxime), 1- (4-phenylsulfanylphenyl) butane-1,2-dione-2-oxime-o-benzo Art, o-acyloxy such as 1- (4-methylsulfanylphenyl) butane-1,2-dione-2-oxime-o-acetate, 1- (4-methylsulfanylphenyl) butan-1-oneoxime-o-acetate Compounds, benzyldimethyl ketal, thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-methylthio Sulfur compounds such as xanthone and 2-isopropylthioxanthone, anthraquinones such as 2-ethylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone and 2,3-diphenylanthraquinone, azobisisobutylnitrile, benzoyl peroxide, cumene Examples thereof include organic peroxides such as peroxides, thiol compounds such as 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, and 2-mercaptobenzothiazole, and tertiary amines such as triethanolamine and triethylamine. Among these, it is preferable to use o-acyloxime compounds from the viewpoint of easily obtaining a highly sensitive photosensitive composition for a gate insulating film. Two or more of these photopolymerization initiators can also be used. In addition, the photoinitiator as used in the field of this invention is used by the meaning containing a sensitizer.

  The content of the photopolymerization initiator (D) in the composition for a gate insulating film of the present invention is 1 to 30% by mass, preferably 4 to 20% by mass. If the component (D) is less than 1% by mass, the photopolymerization rate tends to be slow and the sensitivity tends to decrease, and if it exceeds 30% by mass, the sensitivity is too strong and the pattern line width is smaller than that of the pattern mask. This is not preferable because the line width becomes thicker and the line width faithful to the mask tends to be difficult to reproduce.

  In the composition for a gate insulating film of the present invention, it is preferable to adjust the viscosity by using a solvent in addition to the above (A) to (D). Examples of the solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol and propylene glycol, terpenes such as α- or β-terpineol, acetone, methyl ethyl ketone, cyclohexanone, N-methyl-2- Ketones such as pyrrolidone, aromatic hydrocarbons such as toluene, xylene, tetramethylbenzene, cellosolve, methyl cellosolve, ethyl cellosolve, carbitol, methyl carbitol, ethyl carbitol, butyl carbitol, propylene glycol monomethyl ether, propylene Glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monomethyl ether, Glycol ethers such as reethylene glycol monoethyl ether, ethyl acetate, butyl acetate, cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, carbitol acetate, ethyl carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, propylene glycol mono Examples include acetic acid esters such as ethyl ether acetate, and the like, and these can be dissolved and mixed to form a uniform solution-like composition.

  The source electrode 40 and the drain electrode 41 can be composed of various materials. Examples of the material of the source electrode 40 and the drain electrode 41 include a solution in which metal colloidal particles such as gold, silver, and nickel are dispersed or a paste that uses metal particles such as silver as a conductive material. Also, for example, a metal, an alloy, or a transparent conductive film material is formed on the entire surface by sputtering or vapor deposition, and a resist pattern is used to form a desired resist pattern by photolithography or screen printing. A desired pattern can be formed by etching with an etching solution such as the above. In addition, a desired pattern can be directly formed from a metal, an alloy, or a transparent conductive film material by a sputtering method or a vapor deposition method using a mask. Examples of metal materials that can be used for these sputtering and vapor deposition methods include aluminum, molybdenum, chromium, titanium, tantalum, nickel, copper, silver, gold, platinum, and palladium, and examples of the transparent conductive film material include ITO.

  The organic semiconductor layer 50 is an active semiconductor region that forms a channel during transistor operation, and is composed of an organic semiconductor film. The organic semiconductor layer 50 may be composed of various materials, for example, polycyclic aromatic hydrocarbons such as pentacene, anthracene and rubrene, low molecular compounds such as tetracyanoquinodimethane (TCNQ), polyacetylene and poly- Polymers such as 3-hexylthiophene (P3HT) and polyparaphenylene vinylene (PPV) may be used.

  Although not shown in FIG. 1, the organic thin film transistor according to this embodiment may be provided with a sealing layer, a light shielding layer, and the like as necessary.

  Next, the manufacturing method of the organic thin-film transistor which concerns on Embodiment 1 of this invention is demonstrated using FIG. FIG. 2 is a view for explaining the method of manufacturing the organic thin film transistor according to the first embodiment. Note that FIG. 2 will be described using an example in which the above-described gate insulating film is used.

  FIG. 2I is a diagram showing an example of the gate electrode formation process. In the gate electrode formation step, the gate electrode 20 is formed on the insulating substrate 10.

  FIG. 2 (ii) is a diagram illustrating an example of a gate insulating film forming process. In the gate insulating film forming step, the composition for a gate insulating film is applied onto the gate electrode 20, formed into a desired pattern by exposure and development, and then formed by thermal curing. Thereby, the gate insulating film 30 is completed.

  FIG. 2 (iii) shows an example of the source / drain electrode formation step. In the source / drain electrode formation step, the source electrode 40 and the drain electrode 41 are formed on the gate insulating film 30. The source electrode 40 and the drain electrode 41 are formed above the both end portions of the gate electrode 20 so that the central region of the gate electrode 20 is an opening, and are formed so as to partially overlap the both end portions of the gate electrode 20. Is done. Since the source electrode 40 and the drain electrode 41 are made of the same material, the source electrode 40 and the drain electrode 41 may be interchanged. The formation method of the source electrode 40 and the drain electrode 41 does not matter. For example, it may be formed by a printing method such as a screen printing method, an ink jet method, a flexographic printing method, and a reverse offset printing method in addition to a photolithography method and a dispenser method. As described above, a film may be formed using a sputtering method or a vapor deposition method, and then a predetermined pattern may be formed by photolithography or screen printing, or a predetermined pattern may be formed by a sputtering method or a vapor deposition method using a mask. A film may be formed. Various materials can be used as described with reference to FIG. It is necessary that the smoothness of the surface of the gate insulating film 30 after the formation of the source electrode 40 and the drain electrode 41 is maintained.

  FIG. 2 (iv) shows an example of the organic semiconductor layer forming step. In the organic semiconductor layer formation step, the organic semiconductor film is formed in the opening of the source electrode 40 and the drain region 41 and the portion where the gate insulating film 30 is exposed. The formation method of the organic semiconductor layer 50 is not limited and may be formed by various methods. The organic semiconductor layer 50 is formed on the gate insulating film 30 and covers the opening side end portions of the source electrode 40 and the drain strength 41. The organic semiconductor layer 50 may also be composed of various materials as described in FIG.

[Embodiment 2]
FIG. 3 is a cross-sectional configuration diagram illustrating an example of an organic thin film transistor according to Embodiment 2 of the present invention. The organic thin film transistor according to the second embodiment includes an insulating substrate 10, a gate electrode 20, and a gate insulating film 30, and is configured by sequentially laminating these from the bottom. It is the same. Therefore, these components are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted.

  In the organic thin film transistor according to the second embodiment, the organic semiconductor layer 51 is formed on the entire surface of the gate insulating film 30, and the source electrode 42 and the drain electrode 43 are formed on the organic semiconductor layer 51. It differs from the organic thin-film transistor which concerns on.

  The organic thin film transistor according to the second embodiment has a structure called a bottom gate / top contact structure. Thus, the organic thin film transistor according to the present invention may have a top contact structure as long as the gate insulating film 30 is formed on the gate electrode 20.

  The source electrode 42 and the drain electrode strength 43 are formed in the thickness direction on the organic semiconductor layer 50 and are different from the first embodiment, but the top view positions cover both ends of the gate electrode 20. It is the same as that of the organic thin-film transistor which concerns on Embodiment 1 by the point which is such a position.

  With respect to the method of manufacturing the organic thin film transistor according to the second embodiment, the order of the source / drain electrode forming step described with reference to FIG. 2 (iii) and the organic semiconductor layer forming step described with reference to FIG. In the formation step, the organic semiconductor layer 51 may be formed on the entire surface of the gate insulating film 30. The other steps are the same as those in the method for manufacturing the organic thin film transistor according to the first embodiment, and thus the description thereof is omitted.

  Thus, as described in the first and second embodiments, the organic thin film transistor according to the present invention has various structures as long as it has a bottom gate structure in which the gate insulating film 30 is formed on the gate electrode 20. Can be applied to.

  Next, the organic thin-film transistor which concerns on the Example of this invention is demonstrated. In the organic thin film transistor according to the present example, the organic thin film transistor having the bottom contact structure according to the first embodiment shown in FIG. The characteristics were compared with those of the thin film transistor. In addition, in each following example, about the component similar to the organic thin-film transistor which concerns on Embodiment 1, the same referential mark is attached | subjected and the description is abbreviate | omitted.

[Example 1]
The organic thin film transistor according to Example 1 of the present invention was manufactured as follows. First, a glass substrate (20 mm □) was used as the insulating substrate 10, and Al serving as the gate electrode 20 was formed on the insulating substrate 10 so as to have a film thickness of 50 nm by vacuum deposition. The film thickness was measured by using a stylus type surface shape measuring instrument (Dektak 3030, manufactured by ULVAC) to measure the level difference between the film forming part and the non-film forming part. The film thickness formed in each of the following steps was measured by the same method.

  Next, after applying the composition 1 for gate insulating films (a composition is described in Table 1) by the spin coat method, it prebaked at 90 degreeC on the hotplate for 90 seconds. After that, the photocuring reaction of the exposed portion was performed by irradiating ultraviolet light having a wavelength of 365 nm with a 4.5 mW / cm 2 ultrahigh pressure mercury lamp through a photomask for pattern formation with 800 mJ / cm 2. Next, this exposed coated plate is developed with a 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution by dip development for 20 seconds, followed by dip water washing for 60 seconds to remove unexposed portions of the coating film. did. Thereafter, a heat curing process was performed at 200 ° C. for 60 minutes using a hot plate as a post-bake to form a gate insulating film 30 having a thickness of 380 nm.

Next, Au is deposited on the entire surface of the gate insulating film 30 by vacuum deposition so as to have a film thickness of 50 nm, and then a positive photoresist (OFPR800, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied by spin coating. After pre-baking at 90 ° C. for 90 seconds, ultraviolet light having a wavelength of 365 nm was irradiated at 75 mJ / cm ² with a 4.5 mW / cm ² ultrahigh pressure mercury lamp through a photomask for pattern formation. Thereafter, development was performed by dip development of 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution for 25 seconds, followed by dip washing for 60 seconds to remove the exposed portion of the photoresist. Next, this sample was dipped in an etching solution of Au (AURUM-302 Kanto Chemical Co., Inc.) for 60 seconds to perform patterning. Thereafter, it was washed with ultrapure water for 60 seconds and dried by N2 blow to form a source electrode 40 and a drain electrode 41.

  Next, 50 nm of pentacene was formed on the gate insulating film 30 in the openings of the source electrode 40 and the drain electrode 41 by using a vacuum vapor deposition apparatus to form the organic semiconductor layer 50.

  Thus, the organic transistor 1 was formed. The transistor characteristics of this organic transistor 1 were measured.

[Example 2]
Each layer was formed in the same manner as in Example 1 except that the gate insulating film composition 2 (the composition is described in Table 1) was used, and an organic transistor 2 was formed. The film thickness of the gate insulating film 30 was 360 nm. The transistor characteristics of this organic transistor 2 were measured.

Example 3
Example 1 except that the gate insulating film composition 3 (the composition is described in Table 1) was used, and the gate insulating film 30 was formed by heat curing at 150 ° C. for 60 minutes using a hot plate as a post-bake. Each layer was formed in the same manner as described above to form the organic transistor 3. The film thickness of the gate insulating film 30 was 430 nm. The transistor characteristics of this organic transistor 3 were measured.

[Comparative Example 1]
Each layer was formed in the same manner as in Example 1 except that the gate insulating film forming step was performed as described below, and the organic transistor 4 was formed. In the gate insulating film forming step, polyimide varnish (CT4112, manufactured by Kyocera Chemical Co., Ltd.) was applied by spin coating, dried by heating at 100 ° C. for 10 minutes in a nitrogen atmosphere, and further heated at 180 ° C. for 1 hour. As a result, a gate insulating film having a thickness of 680 nm was formed. The transistor characteristics of this organic transistor 4 were measured.

[Comparative Examples 2 and 3]
Each layer was formed in the same manner as in Example 1 except that the gate insulating film compositions 4 and 5 (compositions are listed in Table 1) were used, and organic transistors 5 (Comparative Example 2) and 6 (Comparative Example 3) were formed. Formed. The film thickness of the gate insulating film 30 was 400 nm. The transistor characteristics of these organic transistors 5 and 6 were measured.

* All numbers in the table are parts by mass.
* 1 Propylene glycol monomethyl ether acetate solution of an epoxy acrylate adduct having a fluorene skeleton (resin solids concentration 56.5%, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
* 2 Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (manufactured by Nippon Kayaku Co., Ltd.)
* 3 Aronix M-360 (manufactured by Toa Gosei Co., Ltd.)
* 4 PGMEA solution (ASF) of epoxy acrylate compound obtained by reacting acrylic acid with bisphenol type epoxy resin in which A is 9,9-fluorenyl group in general formula (I) (equivalent to epoxy group) -400 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., resin solid content concentration 50% by mass)
* 5 jER YX4000HK (Mitsubishi Chemical Corporation)

Example 4
An organic transistor was formed by the same method as in Example 1, and the surface roughness of the gate insulating film before and after the formation of the source electrode 40 and the drain electrode 41 was measured. The surface roughness was calculated in a 5 μm square area using an atomic force microscope system (Bruker AXS, Nano Scope Dimension Icon).

Example 5
An organic transistor was formed by the same method as in Example 2, and the surface roughness of the gate insulating film before and after the formation of the source electrode 40 and the drain electrode 41 was measured by the same method as in Example 4.

[Comparative Example 4]
An organic transistor was formed by the same method as in Comparative Example 1, and the surface roughness of the gate insulating film before and after the formation of the source electrode 40 and the drain electrode 41 was measured by the same method as in Example 4.

FIG. 4 is a diagram illustrating one of the transistor characteristics of the organic thin film transistors according to Examples 1 and 2 and Comparative Example 1, and is a diagram illustrating a change characteristic of the drain current with respect to the gate voltage of the organic thin film transistor. In FIG. 4, the characteristic curves of the organic thin film transistors according to Examples 1 and 2 and Comparative Example 1 are shown. In both cases, typical p-type characteristics are obtained. In Examples 1 and 2, there is no current hysteresis, carrier mobility is 0.1 cm ² or more, current on / off ratio is 10 ⁶ or more, and threshold voltage is around 0V. Good switching performance was shown. On the other hand, in Comparative Example 1, a slight current hysteresis was confirmed. Further, from the transistor characteristic curve, a current on / off ratio comparable to that in Examples 1 and 2 was obtained, but the carrier mobility decreased by an order of magnitude and the threshold voltage was significantly shifted to the plus side.

  FIG. 5 is a diagram showing the measurement results of the flatness in the gate insulating film of the organic thin film transistors according to Examples 4 and 5 and Comparative Example 4. In Examples 4 and 5, the surface roughness of the gate insulating film is 0.3 nm or less, and the surface roughness before and after the formation of the Au electrode is hardly observed, so that extremely high flatness is maintained. It was shown that. On the other hand, in Comparative Example 4, the surface roughness after forming the Au electrode increased to 0.9 nm, and a clear variation was observed in the surface roughness.

The above evaluation results are summarized in Table 2.
The transistor characteristics of Example 3 and Comparative Examples 2 and 3 are shown in Table 2 with respective characteristic values read from the characteristic diagram as shown in FIG. 4 for Examples 1, 2 and Comparative Example 1. The figure itself is omitted. In addition, the flatness of the gate insulating film of the organic thin film transistor according to Example 3 and Comparative Examples 2 and 3 was also measured in the same manner as in Examples 4 and 5 and Comparative Example 4, but these figures are also omitted. Only the measured values of the surface roughness after forming the Au electrode are shown in Table 2.

  As described above, the gate insulating film 30 according to the present invention has high flatness after a thin film is formed and after an electrode or the like is formed by photolithography (when an organic semiconductor layer is formed). In addition, since the organic thin film transistor using the same has high carrier mobility and no threshold voltage shift or current hysteresis, the driving stability and responsiveness of the transistor can be improved.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  The present invention can be used in various electronic circuits using organic transistors and organic transistors.

DESCRIPTION OF SYMBOLS 10 Insulating substrate 20 Gate electrode 30 Gate insulating film 40, 42 Source electrode 41, 43 Drain electrode 50, 51 Organic-semiconductor layer

Claims (5)

  (A) For a compound obtained by reacting a bisphenol type epoxy compound with an ethylenically unsaturated bond group-containing monocarboxylic acid, a) a dicarboxylic acid or tricarboxylic acid or acid anhydride thereof, and b) a tetracarboxylic acid or acid thereof A compound obtained by reacting a dianhydride in a range where the molar ratio of a / b is 0.1 to 10, (B) a polymerizable monomer having at least one ethylenically unsaturated bond, and (C ) A gate insulating film obtained by curing a composition containing an epoxy compound.   The gate insulating film according to claim 1, wherein the composition further contains (D) a photopolymerization initiator.   It includes at least one gate electrode, at least one source electrode, at least one drain electrode, at least one organic semiconductor layer, and the gate insulating film according to claim 1 or 2. Organic thin film transistor.   4. The organic thin film transistor according to claim 3, wherein the gate insulating film has a thickness of 0.05 to 1.0 [mu] m. A method of manufacturing an organic thin film transistor comprising at least one gate electrode, at least one source electrode, at least one drain electrode, at least one organic semiconductor layer, and a gate insulating film,
By applying the composition according to claim 1 or 2 on the gate electrode and performing UV exposure and subsequent heat curing at a temperature of 150 to 200 ° C., a film thickness of 0.05 to 1.0 μm is obtained. A method for producing an organic thin film transistor, comprising forming a gate insulating film.