JPWO2016143451A1 - Organic semiconductor film manufacturing method, organic transistor - Google Patents

Abstract

The present invention provides a method for producing an organic semiconductor film and an organic transistor, which are highly versatile and can produce an organic semiconductor film over substantially the entire desired region. The organic semiconductor film manufacturing method of the present invention includes a first ink containing an organic semiconductor and a first organic solvent having a high affinity for the organic semiconductor, a lower affinity for the organic semiconductor than the first organic solvent, An organic semiconductor film manufacturing method for manufacturing an organic semiconductor film by mixing a second ink composed of a second organic solvent to be mixed, the step of supplying a second ink onto a substrate, and a step of supplying the second ink onto the substrate The first ink is supplied onto the second ink before the volume reduction due to evaporation of the second ink exceeds 10% by volume with respect to the supply amount of the second ink, and the first ink and the second ink are supplied. And then, removing the first organic solvent and the second organic solvent to produce an organic semiconductor film, the surface tensions of the first ink and the second ink satisfy a predetermined relationship.

Description

  The present invention relates to an organic semiconductor film manufacturing method and an organic transistor.

Organic thin film transistors (organic TFTs) are used for liquid crystal displays, organic EL (electroluminescence) displays, RFID (radio frequency identification), and the like because they can be reduced in weight, cost, and flexibility. .
In the production of organic thin-film transistors, there is a possibility that a large-area organic semiconductor film can be produced at low energy and cost by printing technology using a solution (ink) in which an organic semiconductor is dissolved in an organic solvent or the like at a high concentration. is there.

  As a method for manufacturing such an organic semiconductor film, various methods have been proposed. For example, in Patent Document 1, as a method for producing a single-crystal organic semiconductor thin film in which almost the entire region of the thin film is a single single crystal, the organic semiconductor is dissolved at a high concentration in an organic solvent having a high affinity for the organic semiconductor. A method of mixing the first ink obtained in this way with a second ink made of an organic solvent having a low affinity for organic semiconductors is disclosed.

JP 2012-49291 A

On the other hand, in Patent Document 1, in order to obtain a desired effect, it is necessary to give a shape in which a seed crystal is generated with high efficiency to a part of a region where ink is stored. More specifically, in Patent Document 1, a seed crystal is generated with high efficiency by providing a small liquid reservoir part, a large liquid reservoir part, and a constricted part for suppressing convection therebetween. I am letting. However, the method as described above limits the shape of the region where the organic semiconductor film is formed, and is not necessarily sufficient in terms of versatility.
In addition, the present inventor uses a substrate having a pattern of a lyophilic region and a liquid repellent region, which is not provided with a shape in which a seed crystal is generated with high efficiency, in accordance with the procedure described in Patent Document 1 on the substrate. After the second ink was applied to the lyophilic region, the organic semiconductor film was produced by applying the first ink to the lyophilic region. It was found that it was not produced.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing an organic semiconductor film that is highly versatile and can manufacture an organic semiconductor film over substantially the entire desired region.
Moreover, this invention also makes it a subject to provide the organic transistor containing the organic-semiconductor film manufactured by the said manufacturing method.

As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by controlling the relationship of the surface tension between the two types of ink, the timing of supplying the ink, the characteristics of the organic solvent used, and the like. I found it.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) A first ink containing an organic semiconductor and a first organic solvent having a high affinity for the organic semiconductor, and a second organic solvent having a lower affinity for the organic semiconductor than the first organic solvent and miscible with the first organic solvent. An organic semiconductor film manufacturing method for manufacturing an organic semiconductor film by mixing a second ink,
Supplying a second ink on the substrate;
The first ink is supplied onto the second ink before the volume reduction due to the evaporation of the second ink supplied onto the substrate exceeds 10% by volume with respect to the supply amount of the second ink. Mixing the ink and the second ink, and then removing the first organic solvent and the second organic solvent to produce an organic semiconductor film,
When the saturated vapor pressure at 25 ° C. of the first organic solvent is p and the molecular weight is M, Z obtained by the following formula (X) is smaller than 10,
A method for producing an organic semiconductor film, wherein the surface tension γ1 of the first organic solvent and the surface tension γ2 of the second organic solvent satisfy the relationship of the formula (Y) at the same temperature. The unit of saturated vapor pressure is kPa, and the unit of molecular weight is g / mol.
Formula (Y) 0 <γ2-γ1 <5
(2) The concentration of the organic semiconductor in the first ink is greater than the solubility of the organic semiconductor in the mixed solvent in which the volume ratio of the first organic solvent to the second organic solvent is 3: 1. Manufacturing method of the organic semiconductor film. Each unit of concentration and solubility is g / L.
(3) The method for producing an organic semiconductor film according to (1) or (2), wherein the volume ratio of the first ink supply amount to the second ink supply amount is 0.3 or less.
(4) The method for producing an organic semiconductor film according to any one of (1) to (3), wherein the supply of the first ink and the supply of the second ink are performed by an inkjet method.
(5) An organic transistor including an organic semiconductor film manufactured by the manufacturing method according to any one of (1) to (4).

ADVANTAGE OF THE INVENTION According to this invention, versatility is high and can provide the manufacturing method of the organic-semiconductor film which can manufacture an organic-semiconductor film over the substantially whole region of a desired area | region.
Moreover, according to this invention, the organic transistor containing the organic-semiconductor film manufactured by the said manufacturing method can also be provided.

FIG. 1A is a cross-sectional view of a substrate used in an embodiment of a method for producing an organic semiconductor film. FIG. 1B is a top view of the substrate shown in FIG. 1A. FIG. 1C is a cross-sectional view when the second ink is supplied onto a lyophilic region of a substrate used in an embodiment of the method for producing an organic semiconductor film. FIG. 1D is a top view of the substrate shown in FIG. 1C. FIG. 1E is a cross-sectional view when the second ink and the first ink are supplied onto the lyophilic region of the substrate used in the embodiment of the method for manufacturing the organic semiconductor film. FIG. 1F is a top view of the substrate shown in FIG. 1E. FIG. 1G is a cross-sectional view when an organic semiconductor film is formed on a lyophilic region of a substrate used in one embodiment of a method for manufacturing an organic semiconductor film. FIG. 1H is a top view of the substrate shown in FIG. 1G. It is sectional drawing of the board | substrate which has an organic-semiconductor film obtained when the ink specifically disclosed by patent document 1 is used. FIG. 2B is a top view of the substrate shown in FIG. 2A.

Below, the manufacturing method (deposition method) of the organic-semiconductor film of this invention is demonstrated.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Features of the present invention are mainly that the difference in surface tension between the first ink and the second ink is adjusted, the evaporation rate of the first organic solvent is adjusted, and the first ink is There are three points that adjust the supply timing. Hereinafter, the feature points will be described in detail with reference to FIG.
1A to 1H are views showing an embodiment of the method for producing an organic semiconductor film of the present invention in the order of steps. 1A is a cross-sectional view taken along line AA in FIG. 1B, FIG. 1C is a cross-sectional view taken along line BB in FIG. 1D, and FIG. 1E is cut along line CC in FIG. 1F. 1G is a cross-sectional view taken along the line DD of FIG. 1H.
First, as shown in FIGS. 1A and 1B, a substrate 10 having a lyophilic region 12 and a lyophobic region 14 on the surface is prepared, and then, as shown in FIG. 1C and FIG. Ink 16 is supplied (applied).
Next, as shown in FIGS. 1E and 1F, when the first ink 18 is supplied (applied) onto the second ink 16, the first ink 18 wets and spreads on the second ink 16 in a laminar flow. In order for the first ink 18 to spread on the second ink 16 in this way, the difference in surface tension between the first ink 18 and the second ink 16 only needs to be within a predetermined range. By forming the layered first ink 18 on the second ink 16 in this manner, an organic semiconductor film is easily formed over the entire lyophilic region 12.
Note that, at the interface between the second ink 16 and the first ink 18, the second organic solvent in the second ink 16 and the first organic solvent in the first ink 18 mutually diffuse, so that the first ink 18 In the region on the second ink 16 side, the solubility of the organic semiconductor is lowered, and crystals of the organic semiconductor begin to precipitate. At this time, since crystals begin to precipitate almost simultaneously over the entire interface between the second ink 16 and the first ink 18, defects such as regions without crystals are less likely to occur.
Further, when the first ink 18 is supplied onto the second ink 16, the volume reduction amount due to the evaporation of the second ink 16 on the substrate 10 is more than 10 volume% with respect to the supply amount of the second ink 16. Before the first ink 18 is supplied. If the amount of decrease of the second ink 16 exceeds 10% by volume, the amount of evaporation of the second ink 16 increases and the convection at the liquid surface of the second ink 16 increases, and the first ink 18 is changed to the second ink. When supplied onto 16, the laminar flow diffusion of the first ink 18 is disturbed. In addition, when the convection of the liquid surface of the second ink 16 is large, the interface between the second ink 16 and the first ink 18 is disturbed, and organic semiconductor crystals are liable to be generated locally. It becomes difficult to obtain an organic semiconductor film over the entire liquid region.
Furthermore, as described above, the first ink 18 spreads over the second ink 16, but at this time, if the evaporation rate of the first organic solvent in the first ink 18 is too high, the first ink 18 may interact with the second ink 16. Before the diffusion, the organic semiconductor crystal is likely to be locally generated by evaporation of the first organic solvent, and as a result, it becomes difficult to obtain the organic semiconductor film over the entire lyophilic region. Therefore, in the present invention, the evaporation rate of the first organic solvent is controlled. It is known as a Langmuir-Knudsen relational expression that the amount of evaporation of a substance at a specific temperature is proportional to the product of the saturated vapor pressure of the substance and the square root of the molecular weight. The relationship of formula (X), which will be described later, is created in consideration of the Langmuir-Knudsen relationship.
By satisfying the above requirements, as shown in FIGS. 1G and 1H, the organic semiconductor film 20 can be manufactured over substantially the entire region on the predetermined lyophilic region 12. Note that “substantially the entire area” is intended to mean an area of more than about 70% of the lyophilic area 12.

  On the other hand, when the first ink containing orthodichlorobenzene and the second ink containing dimethylformamide (DMF), which are specifically disclosed in Patent Document 1, are used, as shown in FIG. 2A and FIG. The organic semiconductor film 20 can be manufactured only in about 50% of the region 12.

Hereinafter, the details of the procedure of the method for producing an organic semiconductor film of the present invention (hereinafter also simply referred to as “the production method of the present invention”) will be described in detail.
In the following, first, the components of the first ink and the second ink used in the production method of the present invention will be described in detail.

<First ink>
The first ink is an ink that contains an organic semiconductor and a first organic solvent having high affinity for the organic semiconductor. In other words, the first ink is an ink obtained by dissolving an organic semiconductor in a first organic solvent having high affinity for the organic semiconductor.

(Organic semiconductor)
The kind in particular of organic semiconductor used is not restrict | limited, A well-known organic semiconductor can be used. Specifically, pentacenes such as 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS pentacene), tetramethylpentacene, and perfluoropentacene, TES-ADT (5,11-bis (triethylsilylethynyl) Anthradithiophenes), and diF-TES-ADT (2,8-difluoro-5,11-bis (triethylsilylethynyl) anthradithiophene), DPh-BTBT (2,7-diphenyl [ 1] benzothieno [3,2-b] [1] benzothiophene) and benzothienobenzothiophenes such as Cn-BTBT (benzothienobenzothiophene), Cn-DNTT (dinaphtho [2,3-b: 2 ' , 3'-f] thieno [3,2-b] thiophene) and other dinaphthothienothiophenes, perixane Dioxaanthanthrenes such as tenoxanthene, rubrenes, C60, and fullerenes such as PCBM ([6,6] -Phenyl-C61-Butyric Acid Methyl Ester), copper phthalocyanines, and phthalocyanines such as fluorinated copper phthalocyanines , P3RT (poly (3-alkylthiophene)), PQT (poly [5,5′-bis (3-dodecyl-2-thienyl1) -2,2′-bithiophene]), and P3HT (poly (3 And polythiophenes such as poly [2,5-bis (3-dodecylthiophen-2-yl) thieno [3,2-b] thiophene] (PBTTT) and the like. Illustrated.

As described below, the organic semiconductor SP (Solubility Parameter) value ^{(MPa) 1/2} is, the SP value of the first organic solvent ^{(MPa) 1/2} and a second organic SP value of the solvent ^{(MPa) 1} It is preferable to satisfy a predetermined relationship with ^{/ 2} .
In addition, as a measuring method of SP value (MPa) ^1/2 of an organic semiconductor, the Fedors calculation method (RF Fedors, Polymer Engineering Science, 14, p147-154 (1974)) is used.

(First organic solvent)
The first organic solvent is an organic solvent having high affinity for the organic semiconductor. High affinity means that the solubility of the organic semiconductor is high and corresponds to a so-called good solvent for the organic semiconductor.
When the saturated vapor pressure at 25 ° C. of the first organic solvent is p (kPa) and the molecular weight is M (g / mol), Z obtained by the following formula (X) is smaller than 10. Among these, Z is preferably 8 or less, and preferably 7 or less in that the area of the organic semiconductor film to be formed is larger (hereinafter also referred to simply as “the effect of the present invention is more excellent”). More preferred. The lower limit is not particularly limited, but is often 0.1 or more, and is preferably 0.5 or more from the viewpoint of handleability.

  As described above, the above formula (X) represents the product of the saturated vapor pressure of the substance and the square root of the molecular weight, as with the Langmuir-Knudsen relational expression, and Z is related to the evaporation rate of the substance. . It is intended that the greater the Z, the greater the evaporation rate.

  The type of the first organic solvent is not particularly limited, and an optimal organic solvent is appropriately selected according to the type of the organic semiconductor. Examples of the organic solvent include methanol, ethanol, isopropanol, normal-butanol, secondary butanol, normal-hexanol, 1,3-butanediol, 1,2-propanediol, and alcohol solvents such as cyclohexanol; anisole, And ether solvents such as methylanisole; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, cyclopentanone, and benzaldehyde; ethyl acetate, butyl acetate, acetic acid-normal-amyl, methyl sulfate Ester solvents such as ethyl propionate, dimethyl phthalate, ethyl benzoate, propylene glycol monomethyl ether acetate, and methoxypropyl acetate; Hydrocarbon solvents such as ethylene, xylene, benzene, ethylbenzene, tetralin, and hexadecane; halogenated carbon tetrachloride, trichloroethylene, chloroform, 1,1,1-trichloroethane, methylene chloride, monochlorobenzene, and dichlorobenzene Hydrocarbon solvents; ether solvents such as tetrahydrofuran, diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 1-methoxy-2-propanol, and propylene glycol monomethyl ether; dimethylformamide, dimethylacetamide, etc. Amide solvents; dimethyl sulfoxide and sulfonic acid solvents such as sulfolane.

A preferred embodiment of the first organic solvent is an organic solvent X that exhibits an SP value of S1 that satisfies the relationship of the following formula (1) when the SP value (MPa) ^1/2 of the organic semiconductor is A.
Formula (1) A-1.5 <S1 <A + 1.5
That is, the SP value (S1) (MPa) ^1/2 of the organic solvent X is in the range of more than (A-1.5) and less than (A + 1.5), based on A which is the SP value of the organic semiconductor. Is preferred. If the SP value of the first organic solvent is within the above range, the affinity of the first organic solvent to the organic semiconductor is higher, and the solubility of the organic semiconductor in the first organic solvent is higher. Especially, it is preferable that the range of SP value (S1) of the organic solvent X satisfy | fills the relationship of Formula (2) from the point that affinity with an organic semiconductor is higher and a high concentration ink can be prepared.
Formula (2) A-1.0 <S1 <A + 1.0
For example, the SP value of TIPS pentacene, which is an organic semiconductor, is calculated as 19.4 (MPa) ^1/2 . Therefore, as the first organic solvent suitable for this organic semiconductor, an organic solvent having an SP value (MPa) ^1/2 of more than 17.9 and less than 20.9 is used with reference to the above formula (1). preferable. Examples of the organic solvent having an SP value (MPa) ^1/2 in the above range include toluene (18.2), tetralin (19.9), chloroform (19.0), chlorobenzene (19.4), o- Examples include dichlorobenzene (20.5) and anisole (19.5). In addition, the parenthesis column of the said solvent description intends SP value (MPa) ^1/2 of each solvent.
The SP value of the first organic solvent is described in Polymer HandBook (Second Edition), Chapter IV, Solubility Parameter Values, and this value is the SP value in the present invention. Moreover, a unit is (MPa) ^1/2 and points out the value in 25 degreeC. In addition, R.D. F. The value calculated by the method described in Fedors, Polymer Engineering Science, 14, p147-154 (1974) is used as the SP value in the present invention.
Further, the SP value of the second organic solvent described later is the same definition as above.

The boiling point of the first organic solvent is not particularly limited, but is preferably 100 to 250 ° C, more preferably 150 to 210 ° C, from the viewpoint that the effect of the present invention is more excellent.
The boiling point (° C.) is intended at 1 atm.

(Method for producing first ink)
The first ink is obtained by dissolving the organic semiconductor in the first organic solvent described above.
The method for producing the first ink is not particularly limited. For example, the organic semiconductor is added to a predetermined amount of the first organic solvent, and, if necessary, the first organic solvent to which the organic semiconductor is added is stirred and And / or a sonication method.
The concentration (g / L) of the organic semiconductor in the first ink is not particularly limited, but the volume ratio of the first organic solvent to the second organic solvent described later (first organic solvent) is more effective in the present invention. The volume of the second organic solvent) is preferably larger than the solubility (g / L) of the organic semiconductor in the mixed solvent having a ratio of 3: 1. As described above, when the first ink is supplied onto the second ink, the first organic solvent in the first ink and the second organic solvent in the second ink start to diffuse each other. At that time, the concentration of the second organic solvent gradually increases in the region on the second ink side in the first ink, and a so-called mixed solution state is formed. When the concentration of the organic semiconductor in the first ink is larger than the solubility of the organic semiconductor in the mixed solvent in which the volume ratio of the first organic solvent to the second organic solvent is 3: 1 as described above, the first ink is used. The organic semiconductor is likely to be precipitated due to the influence of the second organic solvent diffused therein, and a desired effect is easily obtained.
The specific range of the concentration (g / L) of the organic semiconductor in the first ink varies depending on the type of organic semiconductor used, but is often 5.0 to 50 g / L. Is more preferably 7.0 to 30 g / L.

<Second ink>
The second ink is an ink made of a second organic solvent that has a lower affinity for an organic semiconductor than the first organic solvent and is miscible with the first organic solvent.
The second organic solvent is an organic solvent having a low affinity for the organic semiconductor. The low affinity means that the solubility of the organic semiconductor is low, and corresponds to a so-called poor solvent for the organic semiconductor.
The type of the second organic solvent is not particularly limited, and an optimal organic solvent is appropriately selected according to the type of the organic semiconductor. As an organic solvent, the solvent enumerated by the 1st organic solvent mentioned above is mentioned, for example.

As a preferred embodiment of the second organic solvent, when the SP value (MPa) ^1/2 of the organic semiconductor is A, the organic solvent showing the SP value of S2 that satisfies the relationship of the following formula (3) or formula (4) Y is mentioned.
Formula (3) A-10.0 <S2 <A-4.0
Formula (4) A + 4.0 <S2 <A + 10.0
That is, based on A which is the SP value of the organic semiconductor, the SP value (S2) (MPa) ^1/2 of the organic solvent Y is in a range exceeding (A-10.0) and less than (A-4.0). Preferably, it is in the range of more than (A + 4.0) and less than (A + 10.0). If the SP value of the second organic solvent is within the above range, better compatibility between the low affinity of the second organic solvent for the organic semiconductor and the miscibility of the first organic solvent and the second organic solvent is possible. It becomes. Especially, it is preferable that the range of SP value (S2) of the organic solvent Y satisfy | fills the relationship of Formula (5) or Formula (6) by the point which the effect of this invention is more excellent.
Formula (5) A-7.5 <S2 <A-4.3
Formula (6) A + 4.3 <S2 <A + 7.5

The boiling point of the second organic solvent is not particularly limited, but is preferably 120 to 300 ° C and more preferably 150 to 290 ° C in that the effect of the present invention is more excellent.
The boiling point (° C.) is intended at 1 atm.

The first organic solvent and the second organic solvent described above are miscible. The term “mixing” is intended to mean that the first organic solvent and the second organic solvent are uniformly mixed in any ratio in a normal temperature and normal pressure environment.
The absolute value of the difference (MPa) ^1/2 between the SP value of the first organic solvent and the SP value of the second organic solvent is not particularly limited, but both are more uniformly mixed and the effect of the present invention is more excellent. And is preferably less than 10, more preferably 7.0 or less. The lower limit is not particularly limited, but is often 2.5 or more.

<Procedure of manufacturing method>
According to the manufacturing method of the present invention, the step of supplying the second ink onto the substrate (second ink supply step), and the volume reduction amount due to evaporation of the second ink supplied onto the substrate becomes the supply amount of the second ink. On the other hand, before the amount exceeds 10% by volume, the first ink is supplied onto the second ink, the first ink and the second ink are mixed, and then the first organic solvent and the second organic solvent are removed. And a step of manufacturing an organic semiconductor film (first ink supply step).
Below, the procedure of each process is explained in full detail.

(Second ink supply step)
This step is a step of supplying the second ink onto the substrate. More specifically, for example, first, as shown in FIGS. 1A and 1B, a substrate 10 having a lyophilic region 12 and a lyophobic region 14 is prepared, and then, as shown in FIGS. 1C and 1D. Then, the second ink 16 is supplied onto the lyophilic region 12.
The aspect of the second ink used in this step is as described above.

The type of the substrate is not particularly limited, and a known substrate (such as a resin substrate, a glass substrate, a metal substrate, or a silicon substrate) can be used as appropriate. For example, when a bottom gate / bottom contact type organic TFT is manufactured, a first ink and a second ink are interposed between a source electrode and a drain electrode on a substrate in which a source electrode and a drain electrode are formed on an insulating layer. It is also possible to deposit organic semiconductor crystals by discharging.
Among them, it is preferable to use a substrate having a lyophilic region (parent ink region) and a lyophobic region (ink repellent region) on the surface in that an organic semiconductor film can be deposited at a predetermined position. That is, a substrate having a so-called lyophilic pattern and lyophobic pattern is preferable. When such a substrate is used, droplets deposited by an ink jet method can be defined in a certain region.
Here, the lyophilic region is a region where the solution tends to wet and spread, and the liquid repellent region is a region where the solution is difficult to spread. Therefore, when ink is applied on the substrate, the ink is likely to be repelled in the liquid repellent area, and the ink tends to stay in the lyophilic area.
Note that the presence of the lyophilic region and the liquid repellent region on the substrate surface means that there are two regions on the substrate surface having different contact angles with respect to the ink. The absolute value of the difference in contact angle between the lyophilic region and the liquid repellent region with respect to the ink is not particularly limited, but is preferably 20 ° or more, and more preferably 25 ° or more in that the ink tends to stay in one region. The upper limit is not particularly limited, but is often 90 ° or less.
The lyophilic region is preferably a region having a contact angle with respect to ink of 15 ° or less, and the lyophobic region is preferably a region having a contact angle with respect to ink of 40 ° or more.
As a method for measuring the contact angle, ink is dropped on the lyophilic region (or lyophobic region) at 25 ° C., and the contact angle at 1 second after the dropping is measured.

A method for producing the lyophilic region and the lyophobic region is not particularly limited, and a known method can be adopted. For example, the lyophilic process includes a method of performing light irradiation (UV (ultraviolet) irradiation) on the substrate. Examples of the liquefaction treatment include a method of applying a known liquid repellent (water repellent) (for example, hexamethyldisilazane) onto the substrate.
When producing the lyophilic region and the lyophobic region, the lyophilic treatment and / or the lyophobic treatment may be performed on a part of the substrate surface. Good.

The shape of the lyophilic region on the substrate is not particularly limited, and examples thereof include a quadrangular shape, a rounded rectangular shape, a circular shape, an elliptical shape, and a triangular shape.
The number of lyophilic regions on the substrate is not particularly limited, and it may be at least one and may be plural. When there are a plurality of lyophilic regions, the size (area) and / or shape of each lyophilic region may be different.

The method for supplying (applying) the second ink onto the substrate is not particularly limited, and includes an inkjet method, a spin coating method, a kneader coating method, a bar coating method, a blade coating method, a dip coating method, a curtain coating method, a casting method, and A known method such as a screen transfer method can be employed. Among these, the ink jet method is preferable because the second ink can be easily applied to a predetermined position.
The volume per droplet when the second ink is ejected by the inkjet method is not particularly limited, but is preferably 1 to 1000 pL, and more preferably 10 to 100 pL in terms of more excellent effects of the present invention.
In addition, as an inkjet apparatus, the well-known apparatus provided with the inkjet head can be used.

(First ink supply step)
In this step, the first ink is supplied onto the second ink, the first ink and the second ink are mixed, and then the first organic solvent and the second organic solvent are removed to manufacture the organic semiconductor film. It is. More specifically, as shown in FIGS. 1E and 1F, the first ink 18 is supplied onto the second ink 16, and then, as shown in FIGS. 1G and 1H, the first ink 18 in the first ink 18 is supplied. The organic semiconductor film 20 is manufactured by removing the first organic solvent and the second organic solvent in the second ink 16.
The aspect of the second ink used in this step is as described above.
Note that the surface tension γ1 of the first organic solvent and the surface tension γ2 of the second organic solvent at the same temperature satisfy the relationship of the formula (Y). That is, the surface tension γ1 of the first organic solvent at the predetermined temperature T and the surface tension γ2 of the second organic solvent at the predetermined temperature T satisfy the relationship of the following formula (Y). The predetermined temperature T is preferably 25 ° C. In other words, the following relationship is preferably satisfied at 25 ° C.
Formula (Y) 0 <γ2-γ1 <5
As described above, when the relationship of the formula (Y) is satisfied, when the first ink is supplied onto the second ink, the first ink wets and spreads on the second ink in a laminar manner.
Especially, it is preferable to satisfy | fill the relationship of the following formula | equation (Z) at the point which the effect of this invention is more excellent.
Formula (Z) 0 <γ2-γ1 <3

The method of supplying the first ink onto the second ink is not particularly limited, and includes the method of supplying the second ink described in the above (Second ink supply step), and among these, the inkjet method is preferable.
In this step, the first ink is placed on the second ink before the volume reduction amount due to evaporation of the second ink supplied on the substrate exceeds 10% by volume with respect to the second ink supply amount. Supply. As described above, when the volume reduction due to the evaporation of the second ink exceeds 10% by volume, the convection on the liquid surface of the second ink increases, and the laminar flow diffusion (wetting spread) of the first ink is disturbed. In addition, since the mutual diffusion of the first organic solvent and the second organic solvent proceeds locally, a desired effect cannot be obtained.
It should be noted that the first ink is placed on the second ink before the volume reduction due to the evaporation of the second ink exceeds 8% by volume with respect to the supply amount of the second ink. It is preferable to supply. The lower limit of the amount of decrease is not particularly limited, but may be 0% by volume. The supply amount of the second ink is intended to be the amount of the second ink supplied onto the substrate in the second ink supply step.

The method for determining the supply timing of the first ink is not particularly limited, and a method (method 1) for determining the supply timing of the first ink while directly measuring the amount of the second ink on the substrate, There is a method (method 2) of calculating the evaporation amount per unit time and determining the supply timing of the first ink.
Incidentally, in advance as the method for calculating the evaporation amount per second ink unit of time, for example, calculates the time T _A to the second ink by supplying a predetermined amount of the second ink on the substrate is completely evaporated When the same amount of the second ink as described above is supplied onto the substrate, the time when the amount of decrease in volume due to evaporation of the second ink becomes 10% by volume with respect to the supply amount of the second ink is T _A / For example, a method in which 10 hours elapse is used. In this case, in the method 2 described above, the first ink may be supplied to the second ink before T _A / 10 hours have elapsed.

  The supply amount of the first ink supplied onto the second ink is not particularly limited, and an optimal amount is appropriately selected depending on the type of organic semiconductor used. Usually, the volume ratio of the first ink supply amount to the second ink supply amount (first ink supply amount / second ink supply amount) is often 0.05 to 1.0. It is preferable that it is 0.3 or less at the point which an effect is more excellent, and it is more preferable that it is 0.05-0.3.

After supplying the first ink onto the second ink, the organic semiconductor film is obtained by removing the first organic solvent and the second organic solvent from the mixed solution of both.
A method for removing the first organic solvent and the second organic solvent is not particularly limited, and a known method is adopted, and a method of removing the first organic solvent and the second organic solvent by evaporation (volatilization) is preferable. The method for evaporating the first organic solvent and the second organic solvent is not particularly limited, and examples thereof include a method of standing at room temperature, a method of standing under heating conditions, and a method of air drying.

  The organic semiconductor film produced by the above procedure can be suitably used for various applications. In particular, it can be suitably used for an organic semiconductor film of an organic transistor.

  Examples are shown below, but the present invention is not limited thereto.

(Production of substrate A having a lyophilic region and a liquid repellent region)
A 200 nm Si film-coated Si wafer was subjected to UV / O ₃ treatment, surface cleaning treatment, and lyophilic treatment. Thereafter, the Si wafer subjected to the lyophilic treatment was immersed in a 5% by mass octadecyltrimethoxysilane / toluene solution overnight to make the surface liquid repellent. On this liquid repellent surface, a metal mask having an opening of 600 μm × 100 μm is adsorbed by a magnet, and UV / O ₃ treatment is performed again in this state, so that a lyophilic region corresponding to the opening portion of the metal mask and the metal mask A liquid-repellent region corresponding to the portion shielded with was formed. Note that the contact angles of the inks (first ink and second ink) used in Examples and Comparative Examples described later were less than 15 ° in the lyophilic region and more than 50 ° in the liquid repellent region.

<Example 1>
A predetermined amount of 2,7-dioctyl [1] benzothieno [3,2-b] [1] benzothiophene (C8-BTBT) (SP value: 20.2 (MPa) ^1/2 ) is weighed and anisole (SP value) : 19.5 (MPa) ^1/2 ), and a first ink having a C8-BTBT concentration of 12 g / L was produced.
A second ink made of dimethylformamide (DMF) (SP value: 24.9 (MPa) ^1/2 ) was prepared.
The solubility of C8-BTBT in a mixed solution having a volume ratio of anisole to DMF (anisole: DMF) of 3: 1 is 9.8 g / L, and the concentration of C8-BTBT in the first ink (g / L ) Was bigger.
The saturated vapor pressure of anisole at 25 ° C. is 0.47 kPa, the molecular weight is 108.1 g / mol, and Z (= p × √M) obtained by the above formula (X) is 4.9. 10 or less.
Moreover, the surface tension (γ1) at 25 ° C. of anisole is 34.2 mN / m, the surface tension (γ2) of DMF at 25 ° C. is 35.8 mN / m, and the surface tension difference (γ2−γ1) between the two is 1 .6, and the relationship of the above-described formula (Y) was satisfied.

Separate ink jet heads were filled with the combination of the first ink and the second ink described above. The discharge volume of each of the first ink and the second ink (volume per droplet) was 90 pL and 120 pL.
First, as the order of ejection, after the second ink (30 drops) is ejected into the lyophilic area and the entire lyophilic area is filled with the second ink, the amount of decrease in the volume of the second ink is the second ink. The first ink (4 drops) on the second ink before the amount exceeds 10 vol% (the first ink supply amount is 1/10 (volume ratio) of the second ink supply amount). The first ink and the second ink were mixed. More specifically, the supply time of the first ink was 0.9 seconds after the second ink was supplied to the lyophilic region. After the second ink similar to the above was supplied onto the lyophilic area, the time until the entire amount of the ink was evaporated was 11.4 seconds. Therefore, when the first ink was supplied, the second ink was used. The amount of decrease in the ink volume is calculated to be about 7.9% by volume.
A few seconds after mixing the first ink and the second ink, an organic semiconductor crystal is deposited at the interface between the first ink and the second ink, and then the solvent is evaporated and dried within a few minutes, whereby an organic semiconductor film is obtained. It was. The following evaluation was implemented with respect to the obtained organic-semiconductor film. The results are shown in Table 1.

(Evaluation)
The deposited organic semiconductor film was observed with a crossed Nicol microscope, and the occupation ratio ((area of organic semiconductor film / area of lyophilic area) × 100} of the organic semiconductor film in the lyophilic area was evaluated. Evaluation criteria are as follows, and are preferably A to C.
"A": Occupancy rate is over 90% "B": Occupancy rate is over 80% and 90% or less "C": Occupancy rate is over 70% and 80% or less "D": Occupancy rate is 70% or less

<Example 2>
The first organic solvent is tetralin (SP value: 19.9 (MPa) ^1/2 ), the C8-BTBT concentration is 18.0 g / L, and the supply amount of the first ink is relative to the supply amount of the second ink. An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the droplet ejection number was adjusted to be 3/10. The results are shown in Table 1.
The solubility of C8-BTBT in a mixed solution of tetralin and DMF in a volume ratio (tetralin: DMF) of 3: 1 is 16.5 g / L, and the concentration of C8-BTBT in the first ink (g / L ) Was bigger.
Further, the saturated vapor pressure of tetralin at 25 ° C. is 0.050 kPa, the molecular weight is 132.2 g / mol, and Z (= p × √M) obtained by the above-described formula (X) is 0.6. 10 or less.
Further, the surface tension (γ1) of tetralin at 25 ° C. is 34.5 mN / m, and the surface tension difference (γ2−) between the surface tension (γ2) of DMF at 25 ° C. and the surface tension (γ1) of tetralin at 25 ° C. γ1) was 1.3, and the relationship of the above-described formula (Y) was satisfied.

<Example 3>
The first organic solvent is cyclohexanone (SP value: 19.6 (MPa) ^1/2 ), the C8-BTBT concentration is 7.0 g / L, and the supply amount of the first ink is relative to the supply amount of the second ink. An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the droplet ejection number was adjusted to be 3/10. The results are shown in Table 1.
The solubility of C8-BTBT in a mixed solution of cyclohexanone and DMF (cyclohexanone: DMF) 3: 1 is 6.4 g / L, and the concentration of C8-BTBT in the first ink (g / L). ) Was bigger.
Further, cyclohexanone has a saturated vapor pressure at 25 ° C. of 0.670 kPa, a molecular weight of 98.2 g / mol, and Z (= p × √M) obtained by the above formula (X) is 6.6. 10 or less.
The surface tension (γ1) of cyclohexanone at 25 ° C. is 34.4 mN / m, and the difference in surface tension (γ2−) between the surface tension of DMF at 25 ° C. (γ2) and the surface tension of cyclohexanone at 25 ° C. (γ1). γ1) was 1.4, which satisfied the relationship of the above-described formula (Y).

<Example 4>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the concentration of C8-BTBT was changed to 6.3 g / L. The results are shown in Table 1.

<Example 5>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 2 except that the concentration of C8-BTBT was changed to 12.6 g / L. The results are shown in Table 1.

<Example 6>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 3 except that the concentration of C8-BTBT was changed to 4.7 g / L. The results are shown in Table 1.

<Example 7>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 5/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Example 8>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 2 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 5/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Example 9>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 3 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 4/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Example 10>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 4 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 5/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Example 11>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 5 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 5/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Example 12>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 6 except that the number of droplet ejections was adjusted so that the supply amount of the first ink was 4/10 with respect to the supply amount of the second ink. Carried out. The results are shown in Table 1.

<Comparative Example 1>
As an ink supply method, after the first ink (4 drops) is ejected into the lyophilic area and the entire lyophilic area is filled with the first ink, the second ink (20 drops) is ejected onto the first ink. Except for dropping, an organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1. The results are shown in Table 1.
The supply timing of the second ink is 0.9 seconds after the first ink is supplied to the lyophilic region, and the second ink is supplied in a state where the organic solvent in the first ink remains. did.

<Comparative example 2>
As an ink supply method, the first ink (12 drops) is ejected into the lyophilic area, the entire lyophilic area is filled with the first ink, and then the second ink (20 drops) is ejected onto the first ink. Except for dropping, an organic semiconductor film was prepared and evaluated according to the same procedure as in Example 2. The results are shown in Table 1.
The supply timing of the second ink is 0.9 seconds after the first ink is supplied to the lyophilic region, and the second ink is supplied in a state where the organic solvent in the first ink remains. did.

<Comparative Example 3>
As an ink supply method, the first ink (12 drops) is ejected into the lyophilic area, the entire lyophilic area is filled with the first ink, and then the second ink (20 drops) is ejected onto the first ink. Except for dropping, an organic semiconductor film was prepared and evaluated according to the same procedure as in Example 3. The results are shown in Table 1.
The supply timing of the second ink is 0.9 seconds after the first ink is supplied to the lyophilic region, and the second ink is supplied in a state where the organic solvent in the first ink remains. did.

<Comparative Example 4>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the supply timing of the first ink was changed 5 seconds after supplying the second ink to the lyophilic region. The results are shown in Table 1.

<Comparative Example 5>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 2 except that the supply time of the first ink was changed 5 seconds after supplying the second ink to the lyophilic region. The results are shown in Table 1.

<Comparative Example 6>
An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 3 except that the supply timing of the first ink was changed 5 seconds after supplying the second ink to the lyophilic region. The results are shown in Table 1.

<Comparative Example 7>
According to the same procedure as in Example 1, except that the first organic solvent was chlorobenzene (SP value: 19.6 (MPa) ^1/2 ) and the C8-BTBT concentration was 30.0 g / L. Were prepared and evaluated. The results are shown in Table 1.
The solubility of C8-BTBT in a mixed solution of chlorobenzene and DMF (volume ratio of chlorobenzene: DMF) of 3: 1 is 24.6 g / L, and the concentration of C8-BTBT in the first ink (g / L ) Was bigger.
Further, the saturated vapor pressure of chlorobenzene at 25 ° C. is 1.599 kPa, the molecular weight is 112.6 g / mol, Z (= p × √M) determined by the above-described formula (X) is 17, and 10 Was not less than.
The surface tension (γ1) of chlorobenzene at 25 ° C. is 33.0 mN / m, and the surface tension difference (γ2−) between the surface tension (γ2) of DMF at 25 ° C. and the surface tension (γ1) of chlorobenzene at 25 ° C. γ1) was 2.8, which satisfied the relationship of the above-described formula (Y).

<Comparative Example 8>
The first organic solvent is dichlorobenzene (SP value: 20.5 (MPa) ^1/2 ), the C8-BTBT concentration is 22.0 g / L, and the supply amount of the first ink is set to the supply amount of the second ink. On the other hand, an organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the number of droplet ejections was adjusted to be 3/10. The results are shown in Table 1.
The solubility of C8-BTBT in a mixed solution of dichlorobenzene and DMF (volume ratio of dichlorobenzene: DMF) 3: 1 is 20.6 g / L, and the concentration of C8-BTBT in the first ink (g / L) was larger.
Further, dichlorobenzene has a saturated vapor pressure at 25 ° C. of 0.20 kPa, a molecular weight of 147 g / mol, and Z (= p × √M) obtained by the above-described formula (X) is 2.4. It was less than 10.
The surface tension (γ1) of dichlorobenzene at 25 ° C. is 36.5 mN / m, and the surface tension difference between the surface tension (γ2) of DMF at 25 ° C. and the surface tension (γ1) of dichlorobenzene at 25 ° C. ( [gamma] 2- [gamma] 1) was -0.7 and did not satisfy the relationship of the above-described formula (Y).

<Comparative Example 9>
The first organic solvent is mesitylene (SP value: 17.8 (MPa) ^1/2 ), the C8-BTBT concentration is 30.0 g / L, and the supply amount of the first ink is relative to the supply amount of the second ink. An organic semiconductor film was prepared and evaluated according to the same procedure as in Example 1 except that the droplet ejection number was adjusted to be 3/10. The results are shown in Table 1.
The solubility of C8-BTBT in a mixed solution of mesitylene and DMF at a volume ratio of 3: 1 (mesitylene: DMF) is 27.3 g / L, and the concentration of C8-BTBT in the first ink (g / L). ) Was bigger.
In addition, the saturated vapor pressure of mesitylene at 25 ° C. is 0.330 kPa, the molecular weight is 120.2 g / mol, and Z (= p × √M) obtained by the above formula (X) is 3.6. 10 or less.
The surface tension (γ1) of mesitylene at 25 ° C. is 27.6 mN / m, and the difference in surface tension (γ2−) between the surface tension (γ2) of DMF at 25 ° C. and the surface tension (γ1) of mesitylene at 25 ° C. γ1) was 8.2 and did not satisfy the relationship of the above-described formula (Y).

In Table 1, in the “surface tension difference” column, “A” is satisfied when the relationship of the above formula (Y) is satisfied, and “B” is satisfied when the relationship of the expression (Y) is not satisfied.
In Table 1, in the “evaporation rate” column, the case where Z (= p × √M) obtained from the above formula (X) is less than 10 is “A”, and the case where it is 10 or more is “B”.
In Table 1, in the “droplet order” column, “ink 2 → 1” indicates that ink 1 is further supplied after ink 2 is supplied onto the substrate, and “ink 1 → 2” indicates that ink 1 is supplied to the substrate. This indicates that the ink 2 is further supplied after being supplied upward.
In Table 1, in the “droplet ejection interval” column, the second ink is supplied before the volume reduction amount due to evaporation of the second ink supplied onto the substrate exceeds 10% by volume with respect to the supply amount of the second ink. The case where the first ink is supplied above is “A”, and the case where the first ink is supplied onto the second ink after exceeding 10 vol% is referred to as “B”.
In Table 1, in the “first ink concentration” column, the concentration of the organic semiconductor in the first ink is such that the volume ratio of the first organic solvent to the second organic solvent is 3: 1. The case where the solubility is greater than “A” is indicated as “A”, and the case where the solubility is less than “B”.

As shown in Table 1, according to the method for producing an organic semiconductor film of the present invention, it was confirmed that the organic semiconductor film can be produced over substantially the entire desired region.
In particular, the comparison between Examples 1 and 4 (or 2 and 5, or 3 and 6) indicates that the concentration of the organic semiconductor in the first ink is a volume ratio between the first organic solvent and the second organic solvent. When the solubility of the organic semiconductor in the mixed solvent having a ratio of 3: 1 is larger than that of the organic semiconductor, it was confirmed that a more excellent effect was obtained.
Further, when the volume ratio of the supply amount of the first ink to the supply amount of the second ink is 0.3 or less from the comparison between Examples 1 and 7 (or 2 and 8, or 3 and 9), It was confirmed that more excellent effects can be obtained.
On the other hand, as shown in Comparative Examples, Comparative Examples 1 to 3 in which the ink ejection order is not a predetermined order, Comparative Examples 4 to 6 in which the timing of supplying the first ink is not a predetermined time, and the first organic solvent are predetermined In Comparative Examples 7 to 9 that did not satisfy the above characteristics, the organic semiconductor film was formed only in about half of the lyophilic region, and the desired effect was not obtained.

DESCRIPTION OF SYMBOLS 10 Substrate 12 Lipophilic area 14 Liquid repellent area 16 Second ink 18 First ink 20 Organic semiconductor film

Claims (5)

A first ink comprising an organic semiconductor and a first organic solvent having a high affinity for the organic semiconductor; and a second organic solvent having a lower affinity for the organic semiconductor than the first organic solvent and miscible with the first organic solvent. A method for producing an organic semiconductor film by mixing the second ink and
Supplying the second ink onto a substrate;
The first ink is supplied onto the second ink before the volume reduction due to evaporation of the second ink supplied onto the substrate exceeds 10% by volume with respect to the supply amount of the second ink. Mixing the first ink and the second ink, and then removing the first organic solvent and the second organic solvent to produce the organic semiconductor film,
When the saturated vapor pressure at 25 ° C. of the first organic solvent is p and the molecular weight is M, Z obtained by the following formula (X) is smaller than 10,
A method for producing an organic semiconductor film, wherein the surface tension γ1 of the first organic solvent and the surface tension γ2 of the second organic solvent satisfy the relationship of formula (Y) at the same temperature. The unit of the saturated vapor pressure is kPa, and the unit of the molecular weight is g / mol.
Formula (Y) 0 <γ2-γ1 <5   The concentration of the organic semiconductor in the first ink is greater than the solubility of the organic semiconductor in a mixed solvent in which the volume ratio of the first organic solvent to the second organic solvent is 3: 1. The manufacturing method of the organic-semiconductor film of description. Each unit of the concentration and the solubility is g / L.   The method for producing an organic semiconductor film according to claim 1, wherein a volume ratio of the supply amount of the first ink to the supply amount of the second ink is 0.3 or less.   The method for producing an organic semiconductor film according to claim 1, wherein the supply of the first ink and the supply of the second ink are performed by an inkjet method.   The organic transistor containing the organic-semiconductor film manufactured from the manufacturing method of any one of Claims 1-4.