TW201528573A - Gate insulator film, organic thin film transistor, and method of manufacturing organic thin film transistor - Google Patents

Abstract

The present invention provides a gate insulating film, which has no change in film quality due to heating or chemical treatment in forming an electrode or the like, and which is capable of maintaining high flatness in forming an organic semiconductor layer. By using such a gate insulating film, the present invention also provides an organic thin film transistor, which has a larger carrier mobility and may express stable transistor properties, and a manufacturing method thereof. The gate insulating film is made up of a cured article obtained by curing a composition, the composition comprising, as essential components, (A) a compound obtained by reacting a bisphenol type epoxy compound with an ethylenically unsaturated coupler-containing mono-carboxylic acid; and (B) a photopolymerization initiator or a thermal polymerization initiator, wherein the cured article contains 40-90 wt% of the component (A), and 0.1-30 wt% of the component (B). The organic thin film transistor is manufactured by applying the composition onto a gate electrode and hardening the composition.

Description

Gate insulating film, organic thin film transistor and method for manufacturing organic thin film transistor

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

The organic thin film electro-crystal system is lightweight and flexible, and is expected to be used in applications of next-generation displays excellent in impact resistance and portability. The organic thin film transistor can be used as a semiconductor by coating a soluble low molecular organic semiconductor and a high molecular organic semiconductor. By using the printing method, it can be applied to a large-area process, and it is expected to greatly reduce the cost. Organic semiconductors also have the advantage of being able to utilize a flexible substrate such as a plastic substrate because they can be formed at a low temperature.

The application fields of organic thin film transistors include organic EL displays, liquid crystals, electronic paper and other display devices, RFID tags or sensors, etc., and research is quite active and diverse. However, the current organic thin film transistor has not reached a practical level in terms of mobility, operating voltage, and drive stability, and is not only an organic semiconductor, but also an improvement in various aspects such as component formation and manufacturing processes.

An organic thin film transistor using an organic semiconductor as illustrated in FIGS. 1 and 3 is generally formed by connecting an organic semiconductor layer and a gate insulating film. Therefore, it is known that the semiconductor characteristics of the organic semiconductor layer are affected by the material constituting the gate insulating film, and the transistor performance is lowered. For example, Patent Document 1 discloses a transistor using a gate insulating layer made of polyimide, but using an organic thin film transistor formed of a gate insulating layer of such a material, there is still a threshold voltage of a gate voltage. Unstable problem point. In addition, polyimine must be heated above 250 °C for hardening, and PEN (polyethylene naphthalate, heat resistance 150 ° C) or PET (polyethylene terephthalate, heat resistant) cannot be used. Highly versatile plastic substrate such as 100 ° C).

In the solution strategy of the above problem, the gate insulating film formed by the cardo-type resins described in Patent Document 2 is used, and the insulation withstand voltage is increased upward, and the threshold voltage is stabilized. However, the carrier mobility of the organic semiconductor layer as an important element of the performance of the organic thin film transistor has not been mentioned. It is known that the carrier mobility of the organic semiconductor layer is affected by the characteristics of the gate insulating film. Therefore, the carrier mobility cannot be sufficiently improved because the characteristics of the gate insulating film are insufficient.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-304014

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-166537

Since the carrier moves at the interface between the organic semiconductor layer and the gate insulating film, it is necessary to improve the flatness of the gate insulating film. However, the gate insulating film formed of an organic compound causes a change in film quality due to heating after film formation, heating in a step such as formation of an electrode, chemical treatment, and the like, and the surface roughness becomes large and flat. Will be significantly reduced.

Therefore, in the case of a preferred gate insulating film used in the organic thin film transistor, a thin film can be formed, and it is necessary to be highly flat even after the formation of the thin film and after the formation of the electrode or the like and the formation of the organic semiconductor layer. However, there has been no gate insulating film that satisfies these characteristics.

In view of the above problems, the present invention can provide a curing temperature which can be formed at a curing temperature of 100 to 150 ° C without causing a change in film quality due to heating or chemical treatment such as formation of an electrode or the like, and can be applied to an organic semiconductor layer. For the purpose of maintaining a high level of gate insulating film during formation. Further, an object of the present invention is to provide an organic thin film transistor which exhibits a large mobility and stable crystal characteristics of a carrier by using a gate insulating film which can maintain high flatness when formed in an organic semiconductor layer, and a method for producing the same . Further, the material for the highly flat insulating film can be applied to the flattened film when it is necessary to planarize the film in the organic transistor structure.

As a result of reviewing the above-mentioned means for solving the problem, the present inventors have found that the use of a predetermined composition can produce The present invention is completed by sufficiently maintaining a flat gate insulating film at the time of formation of the organic semiconductor layer.

That is, the gist of the present invention is as follows.

(1) The present invention is a gate insulating film which is obtained by reacting (A) a compound obtained by reacting a bisphenol type epoxy compound with a monocarboxylic acid having an ethylenically unsaturated bond, and (B) photopolymerization. a gate insulating film obtained by curing a cured product obtained by using a starting agent or a thermal polymerization initiator as a component of an essential component, wherein the cured component (A) contains 40 to 90% by mass, and (B) contains 0.1. ~30% by mass.

(2) The gate insulating film according to the above aspect, wherein the composition further contains (C) a polymerizable monomer having one or more ethylenically unsaturated bonds, and in the cured product, (C) The composition contains 5 to 60% by mass.

(3) The present invention is an organic thin film transistor characterized by comprising at least one gate electrode, at least one source electrode, at least one germanium electrode, at least one organic semiconductor layer, and a gate as recited in (1) or (2) Very insulating film.

(4) The organic thin film transistor according to (3), wherein the gate insulating film has a film thickness of 0.05 to 1.0 μm.

(5) The present invention is a method for producing an organic thin film transistor, which comprises an organic thin film transistor including at least one gate electrode, at least one source electrode, at least one germanium electrode, at least one organic semiconductor layer and a gate insulating film. The manufacturing method is characterized in that the composition described in (1) or (2) is applied to the gate electrode, and is cured by a temperature of 100 to 150 ° C. On the other hand, a gate insulating film is formed with a film thickness of 0.05 to 1.0 μm.

According to the present invention, a gate insulating film capable of maintaining high flatness can be formed at the time of formation of the organic semiconductor layer, the carrier mobility of the organic thin film transistor can be increased upward, and stable crystal characteristics can be exhibited.

10‧‧‧Insert substrate

20‧‧‧gate electrode

30‧‧‧gate insulating film

40, 42‧‧‧ source electrode

41, 43‧‧‧汲 electrode

50, 51‧‧‧ organic semiconductor layer

Fig. 1 is a cross-sectional structural view showing an example of an organic thin film transistor of the first embodiment.

Fig. 2 is an explanatory view showing a method of producing an organic thin film transistor of the first embodiment. Fig. 2(i) is a view showing an example of a step of forming a gate electrode. Fig. 2 (ii) is a view showing an example of a step of forming a gate insulating film. Fig. 2 (iii) is a view showing an example of a source/germanium electrode forming step. Fig. 2(iv) is a view showing an example of an organic semiconductor layer forming step.

Fig. 3 is a cross-sectional structural view showing an example of an organic thin film transistor of the second embodiment.

4 is a graph showing changes in the square root of the gate voltage and the gate current of the organic thin film transistor of Examples 1, 2 and Comparative Example 1.

Fig. 5 is a graph showing the results of measurement of flatness in a gate insulating film of an organic thin film transistor of Example 5 and Comparative Example 4.

Hereinafter, the form for carrying out the invention will be described with reference to the drawings.

[Embodiment 1]

Fig. 1 is a cross-sectional structural view showing an example of an organic thin film transistor according to a first embodiment of the present invention. In FIG. 1, the organic thin film transistor of the first embodiment includes an insulating substrate 10, a gate electrode 20, a gate insulating film 30, a source electrode 40, a germanium 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. Further, the source electrode 40 and the ytterbium 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 plan view. Further, an organic semiconductor layer 50 is formed on the gate insulating film 30 between the source electrode 40 and the germanium electrode 41, and the organic semiconductor layer 50 covers the inner end portions of the source electrode 40 and the germanium electrode 41. The configuration shown in Figure 1 can be referred to as a bottom gate, bottom contact configuration.

The insulating substrate 10 may be composed of various substrates made of an insulating material, but a glass substrate such as quartz glass or cerium oxide glass, polyethylene terephthalate (PET), polyether enamel (PES), or the like may be used. Polyethylene naphthalate (PEN), polyimine (PI), polyether phthalimide (PEI), polystyrene (PS), polyvinyl chloride (PVC), polyethylene (PE), poly Plastic film such as propylene (PP), nylon, polycarbonate, etc. Moreover, if the surface can be subjected to an insulating treatment, a metal foil or the like can be used as the insulating substrate 10.

If the gate electrode 20 can flow current efficiently, it is not necessary to define a material. For example, it can be made of aluminum. Although the gate insulating film 30 can be formed on the surface of the gate electrode 20, the surface of the gate electrode 20 is preferably laminated to form the gate insulating film 30, and it is preferable that the surface smoothness is as high as possible.

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 of the present embodiment is a compound obtained by reacting (A) a bisphenol epoxy compound with a monocarboxylic acid having an ethylenically unsaturated bond, and (B) photopolymerization. A gate insulating film obtained by curing a composition obtained by using a starter or a thermal polymerization initiator as an essential component.

In the organic thin film transistor, when a voltage is applied to the gate electrode 20, a channel can be formed in the organic semiconductor layer 50, and the generated carrier moves between the source electrode 40 and the germanium electrode 41 to conduct electricity, thereby performing a transistor operation. The carrier generated when a voltage is applied to the gate electrode 20 is moved to 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 is slowed, and the carrier mobility is lowered. Therefore, the gate insulating film 30 is required to have flatness.

The gate insulating film 30 of the present invention can be photoprocessed by exposure or organic solvent development after forming a coating film for a composition for a gate insulating film (limited to the use of a photopolymerization initiator as (B)) Or a photoresist is deposited on the coating film of the gate insulating film composition, and the insulating film composition from which the photoresist has been removed by exposure, development, reactive ion etching, or the like is removed by a resist. Stripping and photoprocessing. The gate insulating film of the present invention can have less surface unevenness and flatness even after such light processing steps. Very high film. Further, in the gate insulating film 30 of the present invention, after the source electrode 40 and the ytterbium electrode 41 are formed on the surface thereof, the change in flatness is small. Therefore, an organic semiconductor layer having a good carrier mobility can be formed. That is, according to the present invention, the organic thin film transistor can be improved in carrier mobility and can exhibit stable crystal characteristics. Here, in the reason why the carrier mobility is improved, it is presumed that a highly flat gate insulating film can be obtained by using a predetermined composition for a gate insulating film, and it is presumed that there is a defect in the insulating film that traps the carrier. One of the main reasons is the small amount of functional groups such as carboxyl groups.

The dielectric withstand voltage of the gate insulating film 30 is lower than the withstand voltage required by the actual circuit, and the organic thin film transistor cannot be operated as a device in an actual circuit. For example, in the drive circuit of the display, since it is necessary to drive it at 20 V, the thin film formation and the withstand voltage of the operable gate insulating film 30 are required. The gate insulating film of the present invention can form a film of 1 μm or less, and can be driven by a voltage of 20 V or less because it can withstand a voltage of 20 V. On the other hand, the minimum film thickness of the gate insulating film is generally formed by a gate electrode number of 10 nm, and it is necessary to flatten the unevenness due to the formation of the gate electrode, and it is necessary to be 0.05 μm or more.

As described above, in the organic thin film transistor of the present embodiment, by applying the gate insulating film 30 of the present invention, desired flatness and dielectric withstand voltage can be obtained.

(A) in the composition for a gate insulating film of an organic thin film transistor of the present invention, an epoxy compound having two epoxidized ether groups derived from a bisphenol and a monocarboxylic acid having an unsaturated group The resulting reactant (hereinafter referred to as "bisphenol type epoxy (meth) acrylate compound").

Examples of the bisphenol which is a raw material of the bisphenol type epoxy (meth) acrylate compound (A) include bis(4-hydroxyphenyl) ketone and bis(4-hydroxy-3,5-dimethyl group. Phenyl) ketone, bis(4-hydroxy-3,5-dichlorophenyl) ketone, bis(4-hydroxyphenyl)anthracene, bis(4-hydroxy-3,5-dimethylphenyl)anthracene, Bis(4-hydroxy-3,5-dichlorophenyl)indole, bis(4-hydroxyphenyl)hexafluoropropane, bis(4-hydroxy-3,5-dimethylphenyl)hexafluoropropane, double (4-hydroxy-3,5-dichlorophenyl)hexafluoropropane, bis(4-hydroxyphenyl)dimethyloxane, bis(4-hydroxy-3,5-dimethylphenyl)dimethyl Decane, bis(4-hydroxy-3,5-dichlorophenyl)dimethyloxane, bis(4-hydroxyphenyl)methane, bis(4-hydroxy-3,5-dichlorophenyl)methane, double (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-dichloro Phenyl)ether, 9,9-bis(4-hydroxyphenyl)anthracene, 9,9-bis (4- Hydroxy-3-methylphenyl)anthracene, 9,9-bis(4-hydroxy-3-chlorophenyl)anthracene, 9,9-bis(4-hydroxy-3-bromophenyl)anthracene, 9,9 - bis(4-hydroxy-3-fluorophenyl)indole, 9,9-bis(4-hydroxy-3,5-dimethylphenyl)anthracene, 9,9-bis(4-hydroxy-3,5 -Dichlorophenyl)anthracene, 9,9-bis(4-hydroxy-3,5-dibromophenyl)anthracene, 4,4'-diphenol, 3,3'-diphenol, etc. and derivatives thereof Things. Among these, those having a 9,9-fluorene group are particularly suitable.

Next, the bisphenols are reacted with epichlorohydrin to obtain an epoxy compound having two glycidyl ether groups. On the occasion of this reaction, generally In other words, the epoxy compound of the following general formula (I) is obtained by oligomerization of the diglycidyl ether compound.

(wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent 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-, 9,9-fluorenyl or direct bonding. 1 is 0~10 The number.)

Desirable R ₁ , R ₂ , R ₃ and R ₄ are each a hydrogen atom, and preferably A is a 9,9-fluorenyl group. Further, 1 is usually mixed in a complex value and is an average value of 0 to 10 (not limited to an integer), but it is preferable that the average value of 1 is 0 to 3. When the value of 1 exceeds the upper limit, when the bisphenol epoxy (meth) acrylate compound synthesized from the epoxy compound is used as a composition for a gate insulating film, the viscosity of the composition is too large. The meeting will not go smoothly.

Next, acrylic acid or methacrylic acid as an unsaturated group-containing monocarboxylic acid or both of them are reacted with a compound of the general formula (I) to obtain a bisphenol type epoxy represented by the following general formula (II) ( Methyl) acrylate compound.

(wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a halogen atom or a phenyl group; R ₅ represents a hydrogen atom or a methyl group; and A represents -CO -, -SO ₂ -, -C(CF ₃ ) ₂ -, -Si(CH ₃ ) ₂ -, -CH ₂ -, -C(CH ₃ ) ₂ -, -O-, 9,9-fluorenyl or Direct bond; 1 means 1~10.)

The bisphenol type epoxy (meth) acrylate compound (II) is excellent in the (A) aspect of the composition for a gate insulating film of the present invention because it is a resin having an ethylenically unsaturated double bond. It is necessary for the cured film of the desired physical properties such as light, thermosetting or withstand voltage. Further, the composition using the photopolymerization initiator in the aspect (B) may have a pattern which is patterned by organic solvent development.

The bisphenol type epoxy (meth) acrylate compound of the general formula (II) used in the present invention can be obtained by the above-mentioned steps by a known method such as Japanese Patent Application Laid-Open No. Hei 8-278629 or Japanese It is produced by the method described in the publication No. 2008-9401 or the like. That is, in the method of reacting the unsaturated compound-containing monocarboxylic acid of the epoxy compound of the general formula (I), for example, adding a monocarboxylic acid containing an unsaturated group such as an epoxy group of an epoxy compound to a solvent Medium, in the catalyst (triethylbenzyl ammonium chloride, In the presence of 2,6-diisobutylphenol or the like, a method of heating and stirring to 90 to 120 ° C while blowing air is used.

In the composition for a gate insulating film of the present invention, one or more of the components which are optically or thermally cured other than the bisphenol-type epoxy (meth) acrylate compound may be used in combination of at least one ethylenicity. A polymerizable monomer (C) having a saturated bond. For example, a (meth) acrylate having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate or 2-ethylhexyl (meth) acrylate or , ethylene glycol di(meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, four sub Methyl diol di(meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylol ethane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol III (Meth) acrylate, pentaerythritol tetra(meth) acrylate, dipentaerythritol tetra (meth) acrylate, glycerol (meth) acrylate, sorbitol penta (meth) acrylate, dipentaerythritol (Meth) acrylate, or dipentaerythritol hexa(meth) acrylate, sorbitol hexa(meth) acrylate, azo phosphate, alkylene oxide modified hexa(meth) acrylate, caprolactone (Meth) acrylates such as dipentaerythritol hexa(meth) acrylate. However, the polymerizable monomer having at least one ethylenically unsaturated bond used in combination does not have a free carboxyl group.

The cured product of the composition for a gate insulating film of the present invention contains 40 to 90% by mass, preferably 50 to 80% by mass, of the component (A). Further, the polymerizable monomer (C) is used in the cured product. The range of the amount % or less is preferably, and preferably 5 to 60% by mass.

Among the (B) photopolymerization initiators or thermal polymerization initiators in the composition for a gate insulating film of the present invention, examples of the photopolymerization initiator include acetophenone and 2,2-diethoxyl. Acetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, dichloroacetophenone, trichloroacetophenone, p-tert-butylacetophenone, etc. Benzophenones such as benzophenone, 2-chlorobenzophenone, p,p'-bisdimethylaminobenzophenone, benzyl, benzoin, benzoin methyl ether, benzoin Benzoin ethers such as propyl ether, benzoin isobutyl ether, 2-(o-chlorophenyl)-4,5-phenyldiimidazole, 2-(o-chlorophenyl)-4,5-di ( M-methoxyphenyl)diimidazole, 2-(o-fluorophenyl)-4,5-diphenyldiimidazole, 2-(o-methoxyphenyl)-4,5-diphenyl Diimidazole compounds such as diimidazole, 2,4,5-triaryldiimidazole, 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-oxa a halomethyldiazole compound such as oxadiazole, 2,4,6-paraxyl (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(trichloromethyl)-1,3,5-triazine, 2-(4-methoxy Styryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-(3,4,5-trimethoxystyryl)-4,6-bis (three Chloromethyl)-1,3,5-triazine, 2-(4-methylthiostyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine, etc. Halomethyl-S-triazine compounds, 1,2-octanedione, 1-[4- (phenylthio)phenyl]-,2-(o-benzhydrylhydrazine), 1-(4-phenyl-aminophenylsulfonylphenyl)butane-1,2-dione- 2-肟-o-benzoate, 1-(4-methyl-aminophenylsulfonylphenyl)butane-1,2-dione-2-indole-o-acetate, 1-(4- O-mercapto lanthanide compounds such as methyl p-aminophenylsulfonyl phenyl) butane-1-one oxime-o-acetate, benzyl dimethyl ketal, thioxanthone, 2-chlorothiazide Sulfur compounds such as ketone, 2,4-diethylthioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, 2-ethylhydrazine, octamethylguanidine, 1, Organic peroxides such as 2-benzopyrene, 2,3-diphenylfluorene, etc., azobisisobutylnitrile, benzammonium peroxide, cumene peroxide, etc. a thiol compound such as 2-mercaptobenzimidazole, 2-mercaptobenzoxazole or 2-mercaptobenzothiazole; a third-grade amine such as triethanolamine or triethylamine. Among them, from the viewpoint of easily obtaining a photosensitive composition for a high-sensitivity gate insulating film, it is preferred to use an o-fluorenyl compound. Further, two or more kinds of these photopolymerization initiators can be used. Further, the photopolymerization initiator in the present invention is used as a sensitizer.

Further, in the thermal polymerization initiator in (B), for example, benzammonium peroxide, lauroyl peroxide, di-t-butyl peroxyhexahydroterephthalate, t-butyl Oxy-2-ethylhexanoate, organic peroxide such as 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, azobisisobutyronitrile, azobis 4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, azodibenzoyl, 2,2-azobis(1-ethenyloxy) a redox catalyst such as -1-phenylethane), a water-soluble catalyst such as potassium persulfate or ammonium persulfate, and a redox catalyst such as a combination of a peroxide or a persulfate and a reducing agent. It can be used by users in free radical polymerization. Considering the invention The gate insulating film is selected for the preservation stability of the composition or the formation conditions of the cured product. The thermal polymerization initiator may be used alone or in combination of two or more kinds, and may be used in combination with a photopolymerization initiator or a sensitizer.

The (B) photopolymerization initiator or the thermal polymerization initiator in the composition for a gate insulating film of the present invention is used in the obtained cured product, and the component (B) is 0.1 to 30% by mass, preferably 1 to 20% by mass. When the amount of the component (B) is less than 0.1% by mass, the rate of photopolymerization or thermal polymerization is slow, and in the photopolymerization, the sensitivity is lowered, and if it exceeds 30% by mass, the sensitivity is too strong in photopolymerization. The pattern line width is too thick for the pattern mask, which is not good because it is difficult to reproduce the faithful line width. Further, if the amount of the light or thermal polymerization initiator is too large, it tends to cause gas generation when heated in the subsequent step.

In the composition for a gate insulating film of the present invention, in addition to the above (A) to (B) (other than (A) to (C) as the case may be), it is preferred to adjust the viscosity by using a solvent. Examples of the solvent include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, and propylene glycol, and terpenes such as α- or β-terpineol, and acetone and methyl ethyl. Ketones such as ketone, cyclohexanone and N-methyl-2-pyrrolidone, aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene, 赛路苏, methyl 赛苏苏, ethyl race Lusu, carbitol, methyl carbitol, ethyl carbitol, butyl carbitol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether , glycol ethers such as triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethyl acetate, butyl acetate, 赛路苏 acetate, ethyl 赛苏苏 acetate , butyl succinate acetate, carbitol acetate, ethyl card Acetate such as phenolic acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, etc., and is dissolved by using the same, Mixing can be a homogeneous solution-like composition.

The composition of the gate insulating film of the present invention contains a bisphenol type epoxy (meth) acrylate compound (A) having an ethylenically unsaturated bond as an essential component, but for photohardening property or thermosetting property. The desired properties of the first design may contain other resin components. For example, in order to impart alkali solubility, an alkali-soluble resin containing an ethylenically unsaturated bond group obtained by further reacting an acid dianhydride and an acid monoanhydride in a bisphenol type epoxy (meth) acrylate compound (A) may be used. (D) Coexistence. The ratio (A)/(D) of the component (A) in which the component (D) is allowed to coexist is in the range of 70/30 to 40/60, and if the component (D) is less than 70/30, it is difficult to impart a base to the composition. Soluble. In addition, when the component (D) is more than 40/60, when a composition is used as the gate insulating film, the carboxyl group may be left to have an adverse effect on the transistor characteristics. In order to reduce the amount of the remaining carboxyl group, the (E) epoxy resin may be further coexisted, but if the component (D) is more than (A)/(D)=40/60, it is carried out at a temperature of 150 ° C or lower. At the time of post-baking, it is difficult to sufficiently reduce the residual carboxyl group.

Examples of the acid dianhydride used when the component (A) is derived into the component (D) include pentane tetracarboxylic acid, cyclohexanetetracarboxylic acid, benzophenonetetracarboxylic acid, and biphenyltetracarboxylic acid. An acid dianhydride such as an acid or a biphenyl ether tetracarboxylic acid, and examples of the acid monoanhydride include adipic acid, hexahydrophthalic acid, tetrahydrophthalic acid, phthalic acid, and trimellitic acid. Wait for the acid anhydride.

(D) Molecular weight of alkali-soluble resin containing ethylenically unsaturated bond groups In terms of range, the weight average molecular weight (Mw) is preferably between 2,000 and 10,000, and between 3,000 and 7,000 is particularly good. Further, (D) is preferably in the range of an acid value of 30 to 200 KOHmg/g.

(E) The epoxy resin may, for example, be a phenol novolac type epoxy resin, a bisphenol A type epoxy resin, a biphenyl type epoxy resin or an alicyclic epoxy resin, and may have two or more rings. Oxygen epoxy or epoxy compound.

The source electrode 40 and the ytterbium electrode 41 can be made of various materials. The material of the source electrode 40 and the ytterbium electrode 41 is, for example, a solution in which a metal colloidal particle such as gold, silver or nickel is dispersed, or a metal particle such as silver is used as a paste of a conductive material. Further, for example, a metal, an alloy, or a transparent conductive film material is formed by a sputtering method, a vapor deposition method, or the like, and a desired material is formed by a photolithography method or a screen printing method using a resist material. After the pattern is formed, the desired pattern is formed by etching with an etching solution such as an acid. Further, a metal or an alloy or a transparent conductive film material can be directly formed into a desired pattern by a sputtering method or a vapor deposition method using a mask. Examples of the metal material which can be used in the sputtering method or the vapor deposition method include aluminum, molybdenum, chromium, titanium, rhodium, nickel, copper, silver, gold, platinum, palladium, etc., and examples thereof include ITO. Transparent conductive film material.

The organic semiconductor layer 50 is in the field of an active semiconductor in which a channel is formed during operation of a transistor, and is composed of an organic semiconductor film. Although the organic semiconductor layer 50 may be composed of various materials, for example, a polycyclic aromatic hydrocarbon such as pentacene or anthracene or erythritol, or a low molecular compound such as tetracyanoquinodimethane (TCNQ) may be used. Polyacetylene or poly-3-hexylthiophene (P3HT), a polymer such as polyparaphenylene vinylene (PPV), or the like.

Further, although not shown in Fig. 1, the organic thin film transistor of the present embodiment may be provided with a sealing layer, a light shielding layer, or the like as needed.

Next, a method of producing an organic thin film transistor according to Embodiment 1 of the present invention will be described with reference to Fig. 2 . Fig. 2 is a view for explaining a method of producing an organic thin film transistor of the first embodiment. In addition, in FIG. 2, the example using the gate insulating film mentioned above is demonstrated.

Fig. 2(i) is a view showing an example of a step of forming a gate electrode. In the gate electrode forming step, the gate electrode 20 is formed on the insulating substrate 10.

Fig. 2 (ii) is a view showing an example of a step of forming a gate insulating film. In the gate insulating film forming step, a composition for a gate insulating film is applied on the gate electrode 20, and a photoresist is coated on the coating film, and is formed by exposure and development. After the pattern, the gate insulating film from which the photoresist has been removed is removed by reactive ion etching, and after the photoresist is removed, the film is thermally cured to form a film. (In the component (B) of the gate insulating film composition, a photopolymerization initiator is used, and a pattern of a gate insulating film can be formed by exposure and organic solvent development) thereby completing gate insulation. Membrane 30.

Fig. 2 (iii) is a view showing an example of a source/germanium electrode forming step. In the source/germanium electrode forming step, the source electrode 40 and the germanium electrode 41 can be formed on the gate insulating film 30. The source electrode 40 and the ytterbium 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 portion, and may be formed at both ends of the gate electrode 20 The overlapping positions. Further, the source electrode 40 and the ytterbium electrode 41 are formed of the same material, and the source electrode 40 and the ytterbium electrode 41 may be exchanged, and the method of forming the source electrode 40 and the ytterbium electrode 41 is not required. For example, in addition to the photolithography method or the modulation method, it may be formed by a printing method such as a screen printing method, an inkjet method, a flexographic printing method, or a reverse lithography method. As described above, the film is formed by a sputtering method or a vapor deposition method, and thereafter, a predetermined pattern can be formed by photolithography or screen printing, or a mask or a sputtering method or a vapor deposition method can be used. The membrane is composed of a predetermined pattern. The materials used are as illustrated in Figure 1, and various materials can be used. Further, it is necessary to maintain the smoothness of the surface of the gate insulating film 30 after the source electrode 40 and the germanium electrode 41 are formed.

Fig. 2(iv) is a view showing an example of an organic semiconductor layer forming step. In the organic semiconductor layer forming step, an organic semiconductor film can be formed in a portion where the gate electrode insulating film 30 is exposed at the opening of the source electrode 40 and the germanium electrode 41. The method of forming the organic semiconductor layer 50 can be formed by various methods. The organic semiconductor layer 50 can be formed on the gate insulating film 30 while covering the end portions on the respective opening sides of the source electrode 40 and the ytterbium electrode 41. The organic semiconductor layer 50 is also composed of various materials as described in FIG.

[Embodiment 2]

Fig. 3 is a cross-sectional structural view showing an example of an organic thin film transistor according to a second embodiment of the present invention. The organic thin film transistor of the second embodiment includes an insulating substrate 10, a gate electrode 20, and a gate insulating film 30, which are sequentially arranged The layered structure is the same as that of the organic thin film transistor of the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

In the organic thin film transistor of the second embodiment, the organic semiconductor layer 51 is entirely formed on the gate insulating film 30, and the active electrode 42 and the germanium electrode 43 are formed on the organic semiconductor layer 51, and the embodiment The organic thin film transistor of 1 is different.

The organic thin film transistor of the second embodiment has a structure called a bottom gate and a top contact structure. As described above, the organic thin film transistor of the present invention may have a structure in which the gate insulating film 30 is formed on the gate electrode 20, and may be formed in a top contact structure.

Further, the source electrode 42 and the ytterbium electrode 43 are formed on the organic semiconductor layer 50 in the thickness direction. Although different from the first embodiment, the position in the plan view is at a position covering the both end portions of the gate electrode 20. The same as the organic thin film transistor of the first embodiment.

The method for producing an organic thin film transistor according to the second embodiment is such that the source/germanium electrode forming step illustrated in Fig. 2 (iii) can be interchanged with the organic semiconductor layer forming step described in Fig. 2 (iv), and the organic semiconductor layer can be replaced. In the formation step, the organic semiconductor layer 51 can be formed entirely in the gate insulating film 30. The other steps are the same as those in the method of manufacturing the organic thin film transistor of the first embodiment, and thus the description thereof will be omitted.

As described in the first to second embodiments, the organic thin film transistor of the present invention has a bottom gate structure in which the gate insulating film 30 is formed on the gate electrode 20, and is applicable to various organic structures. Thin film transistor.

[Examples]

Next, an organic thin film transistor of an embodiment of the present invention will be described. In the organic thin film transistor of the present embodiment, an organic thin film transistor having a bottom contact structure of the first embodiment shown in FIG. 1 was produced by using pentacene as a low molecular semiconductor in the organic semiconductor layer 50, and a comparative example was used. The organic thin film transistor is compared for characteristics. In the following embodiments, the same components as those of the organic thin film transistor of the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[Example 1]

The organic thin film electrocrystallization system of Example 1 of the present invention was produced as follows. First, a glass substrate (20 mm□) was used for the insulating substrate 10, and Al which became the gate electrode 20 on the insulating substrate 10 was formed into a film by a vacuum evaporation method at a film thickness of 50 nm. The film thickness was measured by using a stylus type surface shape measuring device (Dektak 3030, manufactured by ULVAC Co., Ltd.) to measure the difference between the film forming portion and the non-film forming portion. The measurement of the film thickness of the film formation in the following steps was carried out in the same manner.

Next, the composition 1 for the gate insulating film (the composition is shown in Table 1) was applied by a spin coating method, and then prebaked on a hot plate at 90 ° C for 90 seconds. Thereafter, the coating film was subjected to a photohardening reaction by irradiating ultraviolet rays having a wavelength of 365 nm at 800 mJ/cm ^{2 with an} ultrahigh pressure mercury lamp of 4.5 mW/cm ^{2 in} total. Then, using a hot plate, a heat hardening treatment was performed at 150 ° C for 60 minutes to form a gate insulating film 30 having a film thickness of 480 nm.

Then, on the gate insulating film 30, Au is formed into a film by a vacuum evaporation method so as to have a film thickness of 50 nm, and then a positive photoresist is applied by a spin coating method (OFPR800, Tokyo Yinghua) Industrial Co., Ltd.), after prebaking at 90 ° C for 90 seconds, irradiated ultraviolet rays having a wavelength of 365 nm of 75 mJ/cm ² with a 4.5 mW/cm ² ultrahigh pressure mercury lamp through a mask for pattern formation. Thereafter, development was carried out by dip-dyaging with a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (TMAH) for 25 seconds, followed by immersion washing for 60 seconds to remove the exposed portion of the photoresist. Then, the sample was immersed in an etching solution of Au (AURUM-302 Kanto Chemical Co., Ltd.) for 60 seconds to form a pattern. Thereafter, it was washed with ultrapure water for 60 seconds, dried by N ₂ blowing, and the source electrode 40 and the ruthenium electrode 41 were formed.

Next, on the gate insulating film 30 of the source electrode 40 and the opening of the germanium electrode 41, pentacene was formed into a film of 50 nm by a vacuum evaporation apparatus to form an organic semiconductor layer 50.

By the above, the organic transistor 1 is formed. The crystal characteristics of the organic transistor 1 were measured in this manner.

[Embodiment 2]

In the case of the insulating substrate 10, a fluoropolymer (product name) as a planarizing film is laminated on a thickness of 600 nm on a PEN film (product name: Teonex (registered trademark) Q65FA, manufactured by Teijin DuPont Film Co., Ltd.) having a thickness of 125 μm. :EPRIMA (registered trademark) AL-X6, Other than the one formed by Asahi Glass Co., Ltd., the other layers were formed in the same manner as in Example 1, and the organic transistor 2 was formed. With this organic transistor 2, the transistor characteristics were measured.

[Example 3]

Except for the formation of the gate insulating film 30, the layers were formed in the same manner as in Example 1 to form an organic transistor 3.

The gate insulating film 30 is formed as will be described later. After the gate insulating film composition 2 (the composition is described in Table 1) was applied by a spin coating method, it was prebaked on a hot plate at 90 ° C for 90 seconds. Thereafter, the photo-shield for pattern formation was irradiated with ultraviolet rays having a wavelength of 365 nm at 800 mJ/cm ^{2 with an} ultrahigh pressure mercury lamp of 4.5 mW/cm ^{2 to} carry out a photohardening reaction of the exposed portion. Next, the exposed coated plate was subjected to dip development for 20 seconds using an aqueous solution of 2.38 wt% tetramethylammonium hydroxide (TMAH), followed by immersion washing for 60 seconds to remove the unexposed film. unit. Thereafter, a gate insulating film 30 was formed by heat-hardening treatment at 150 ° C for 60 minutes on a post-baking using a hot plate.

The transistor characteristics were measured in the above-described organic transistor 3.

[Example 4]

In the same manner as in Example 3, except that a PEN film having a thickness of 125 μm in which the fluoropolymer layer used in Example 2 was 600 nm was used for the insulating substrate 10, each layer was formed to form an organic transistor 4. This organic transistor 4 was measured for transistor characteristics.

[Comparative Example 1]

Except that the gate insulating film forming step was carried out as described below, the same procedure as in Example 1 was carried out to form each layer, and the organic transistor 3 was formed. The gate insulating film forming step was carried out by spin coating method by coating a polyimide coating (CT 4112, manufactured by KYOCERA Chemical Co., Ltd.), and drying at 100 ° C for 10 minutes under nitrogen atmosphere, followed by heating at 180 ° C for 1 hour. . Thereby, a gate insulating film having a film thickness of 680 nm was formed. With this organic transistor 5, the transistor characteristics were measured.

[Comparative Examples 2 and 3]

Except that the gate insulating film composition 3 (the composition is described in Table 1) was used instead of the gate insulating film composition 2, the layers were formed in the same manner as in Examples 3 and 4, and an organic transistor 6 was formed (Comparative) Examples 2) and 7 (Comparative Example 3). Further, the gate insulating film 30 has a film thickness of 400 nm. With respect to this organic transistors 5 and 6, the transistor characteristics were measured.

* The numbers in the table are all parts by mass.

*1 In the general formula (II), A is a 9,9-fluorenyl bisphenol type epoxy acrylate PGMEA solution (ASF-400 (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd., resin solid content concentration: 50% by mass)

*2 ARONIX M-360 (East Asian Synthetic Co., Ltd.)

*3 Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (manufactured by Nippon Kayaku Co., Ltd.)

*4 Propylene glycol monomethyl ether acetate solution with an epoxy acrylate acid adduct of an anthracene skeleton (resin solid concentration: 56.5%, manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.)

*5 jER YX4000HK (Mitsubishi Chemical Co., Ltd.)

[Example 5]

An organic transistor was formed in the same manner 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 ytterbium electrode 41 was measured. The surface roughness was calculated using an atomic force microscope system (Bruker AXS Co., Ltd., Nano Scope Dimension Icon) in a square area of 5 μm.

[Comparative Example 4]

The organic transistor was formed in the same manner 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 ytterbium electrode 41 was measured in the same manner as in Example 5.

4 is a view showing the transistor characteristics of the organic thin film transistors of Examples 1 and 2 and Comparative Example 1, and shows a graph showing changes in the gate voltage of the organic thin film transistor. In Fig. 4, characteristic curves of the organic thin film transistors of Examples 1, 2 and Comparative Example 1 are shown. Typical p-type characteristics were obtained, and in Examples 1 and 2, there was no current hysteresis, the carrier mobility was 0.1 cm ² or more, and the current switching ratio was 10 ⁶ or more. The threshold voltage showed good switching performance in the vicinity of 0 V. On the other hand, Comparative Example 1 was confirmed to have a number of current hysteresis phenomena. Further, as is clear from the transistor characteristic curve, the switching ratio was lower by one digit than in the first and second embodiments, the carrier mobility was lowered by one digit, and the threshold voltage was largely shifted to the positive side.

Fig. 5 is a graph showing the measurement results of the flatness in the gate insulating film of the organic thin film transistor of Example 5 and Comparative Example 4.

In the fifth embodiment, the surface roughness of the gate insulating film was 0.6 nm or less even after the formation of the Au electrode, and the surface roughness after the formation of the Au electrode in Comparative Example 4 was increased to 0.9 nm, and it was found that Example 5 was maintained. Good surface flatness.

The above evaluation results are organized and shown in Table 2.

Further, in the crystal characteristics of Examples 3 and 4 and Comparative Examples 2 and 3, the respective characteristic values read by the characteristic diagrams shown in Fig. 4 of Examples 1 and 2 and Comparative Example 1 are described in the table. 2, and omit the feature map itself. Further, the flatness of the gate insulating film of the organic thin film transistors of Examples 2, 3, and 4 and Comparative Examples 2 and 3 was measured in the same manner as in Example 5 and Comparative Example 4, but these records were described. The figure is omitted, and only the measured values of the surface roughness after the formation of the Au electrode are shown in Table 2.

Thus, the gate insulating film 30 of the present invention can be formed after the film is formed, and after the photolithography is used as an electrode or the like (organic semiconductor layer). When formed, high flatness is obtained. Further, the organic thin film transistor using the gate insulating film 30 of the present invention has high carrier mobility and has no threshold voltage displacement or current hysteresis, and can improve the driving stability or responsiveness of the transistor.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and modifications may be added to the above-described embodiments without departing from the scope of the invention. Replace.

[Industrial availability]

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

10‧‧‧Insert substrate

20‧‧‧gate electrode

30‧‧‧gate insulating film

40‧‧‧ source electrode

41‧‧‧汲 electrode

50‧‧‧Organic semiconductor layer

Claims (5)

A gate insulating film which is obtained by photopolymerizing a compound (B) obtained by reacting a bisphenol epoxy compound with a monocarboxylic acid having an ethylenically unsaturated bond by the following (A) and (B) (A) A gate insulating film obtained by curing a cured product obtained by using a starting agent or a thermal polymerization initiator as a component of an essential component, wherein the component (A) in the cured product contains 40 to 90% by mass, and the component (B) contains 0.1 to 30% by mass. The gate insulating film according to claim 1, wherein the composition further contains (C) a polymerizable monomer having one or more ethylenically unsaturated bonds, and the component (C) contained in the cured product is 5 ~60% by mass. An organic thin film transistor characterized by comprising at least one gate electrode, at least one source electrode, at least one germanium electrode, at least one organic semiconductor layer, and a gate insulating film as recited in claim 1 or 2. The organic thin film transistor according to claim 3, wherein the gate insulating film has a film thickness of 0.05 to 1.0 μm. A method for manufacturing an organic thin film transistor, which is a method for manufacturing an organic thin film transistor having at least one gate electrode, at least one source electrode, at least one germanium electrode, at least one organic semiconductor layer and a gate insulating film, characterized in that The gate electrode is coated with the composition described in claim 1 or 2, and is cured at a temperature of 100 to 150 ° C to form a gate insulating film with a film thickness of 0.05 to 1.0 μm.