Method for producing vertical organic light emitting transistor device and display

Abstract

The method for producing the vertical organic light emitting transistor device comprises: a step (A) in which a substrate having a main surface on which the vertical organic light emitting transistor device is to be formed is prepared; a step (B) in which an organic material containing a polymer having a hydrocarbon group is applied onto the main surface of the substrate; a step (C) in which a dispersion liquid containing a dispersant and a carbon material is applied to the organic material layer formed in the step (B); a step (D) in which the coating film formed in the step (C) is dried; and a step (E) in which, after performing step (D), a cleaning fluid is applied to remove the dispersant.

Description

Technical Field

[0001] The present invention relates to a method for producing a light emitting device, and in particular to a method for producing a vertical organic light emitting transistor device. The present invention also relates to a display. Background Art

[0002] A light-emitting transistor using nanocarbon materials for electrodes is known. For example, Patent Document 1 mentioned below discloses a vertical organic light-emitting transistor device using nanocarbon materials for source electrodes. Unlike conventional light-emitting diodes, this technology makes it possible to eliminate the need for an additional driving horizontal transistor, and since the channel is formed in the thickness direction of the semiconductor layer, the channel length can be significantly reduced compared to a lateral transistor having a channel formed parallel to the surface of the semiconductor layer. This makes it possible to efficiently pass a current of a desired magnitude through the light-emitting transistor.

[0003] Patent Document 1: Japanese Patent No. 6272030

[0004] Patent document 2: WO2021 / 033482

[0005] Patent Document 3: JP-A-2016-118763 Summary of the invention

[0006] When a conductive layer is unevenly formed on a substrate in a semiconductor light-emitting device (such as a light-emitting diode or a light-emitting transistor), the current density is unevenly distributed in the semiconductor light-emitting device, thereby forming a high-brightness area and a low-brightness area in each pixel. In addition, there is a possibility that the brightness varies from pixel to pixel throughout the display area. In particular, the brightness unevenness that can be recognized by a person is related to the quality of the display, and it is therefore desirable to form a conductive layer formed as a part of the semiconductor light-emitting device uniformly on the substrate. In addition, the conductive layer formed in particular in a vertical organic light-emitting transistor device needs to be thin, and the area of ​​the conductive layer needs to be mostly void, because the transistor operation is performed by the electric field generated by the gate electrode of the light-emitting transistor.

[0007] A conductive layer made of a nanocarbon material used in a semiconductor device is formed by applying a dispersion liquid prepared by mixing the nanocarbon material with a predetermined dispersant onto a substrate; and performing a drying process, a baking process, and then a cleaning process to remove the dispersant.

[0008] However, when the conductive layer is formed only by applying a dispersant mixed with a nanocarbon material to a substrate and performing a predetermined treatment, in most cases, the conductive layer formed on the substrate may be unevenly distributed rather than uniformly spread. In particular, in the process of forming a conductive layer required for a vertical organic light-emitting transistor device (which is thin and most of its area is a void), uneven distribution of the conductive material may occur, and thus the probability of problems is high. For this reason, a semiconductor light-emitting device having a conductive layer made of a nanocarbon material may cause brightness unevenness, and therefore has not been actively used for displays from the perspective of quality and reliability.

[0009] In view of the above problems, an object of the present invention is to provide a method for producing a vertical organic light emitting transistor device, which makes it possible to uniformly fix a nanocarbon material to the entire area on which a dispersant is applied.

[0010] In order to achieve the above object, the present invention relates to a method for producing a vertical organic light emitting transistor device, the method comprising:

[0011] Step (A), in which a substrate having a major surface on which a vertical organic light emitting transistor device is to be formed is prepared;

[0012] step (B), in which an organic material including a polymer having a hydrocarbon group is applied onto a major surface of a substrate;

[0013] step (C), in which a dispersion liquid containing a dispersant and a carbon material is applied to the organic material layer formed in step (B);

[0014] step (D), in which the coating film formed in step (C) is dried; and

[0015] Step (E), in which, after performing step (D), a cleaning fluid is applied to remove the dispersant.

[0016] In the production method, the dispersion liquid may contain the dispersant in an amount of 1,000% by mass to 100,000% by mass based on the amount of the carbon material.

[0017] In the production method, the carbon material may be at least one selected from carbon nanotubes (CNT), graphene, and fullerene. It should be noted that the nanocarbon material is preferably carbon nanotubes.

[0018] In the production method, the dispersant may be a polymer having a moiety represented by the following chemical formula (1), and the dispersion liquid may be an organic solvent.

[0019] (Chemical formula 1)

[0020]

[0021] (where R 1 is a tetravalent organic group constituting a tetracarboxylic acid, R 2 is a divalent organic group constituting a diamine, and n is a positive integer. )

[0022] In the production method, R in the part represented by the above chemical formula (1) of the dispersant 1 It may be a cyclobutane ring.

[0023] In the production method, the dispersant may have an acid-dissociable group.

[0024] In the production method, the organic material including the polymer having a hydrocarbon group may have an oxygen content of 1% by mass or less.

[0025] In the above production method, step (C) can be carried out by applying the dispersion onto the organic material layer through any one of application methods including spin coating, slit coating, bar coating, spray coating and ink-jet coating.

[0026] In the above production method, the cleaning fluid may be an alkaline aqueous solution.

[0027] The present invention also relates to a display comprising a vertical organic light emitting transistor device produced by the above production method.

[0028] It should be noted that other aspects of the present invention will become apparent by reading the following description and accompanying drawings.

[0029] According to the present invention, a method for producing a vertical organic light emitting transistor device can be realized, which method enables a nano-carbon material to be uniformly fixed to the entire region on which a dispersant is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [Fig. 1] Fig. 1 is a schematic diagram showing the overall structure of a display according to an embodiment.

[0031] [ Figure 2 ] Figure 2 It is a diagram showing a circuit structure of a pixel of the display according to the embodiment.

[0032] [ Figure 3 ] Figure 3 is a top view of one of the pixels of the display of the embodiment.

[0033] [ Figure 4 ] Figure 4 is the pixel along Figure 3 A cross-sectional view taken along the line AA' shown in FIG.

[0034] [ Figure 5 ] Figure 5 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0035] [ Figure 6 ] Figure 6 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0036] [ Figure 7 ] Figure 7 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0037] [ Figure 8 ] Figure 8 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0038] [ Fig. 9 ] Fig. 9 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0039] [ Fig.10 ] Fig.10 is a top view showing a process of producing the light emitting transistor of the embodiment.

[0040] [ Fig.11 ] Fig.11 This is an AFM photograph of the surface of the substrate.

[0041] [ Fig.12 ] Fig.12 This is an AFM photograph of the surface of the substrate. DETAILED DESCRIPTION

[0042] Hereinafter, the structure of a display 1 having a vertical organic light emitting transistor device as an embodiment will be first described, and then an embodiment of a method according to the present invention for producing the display 1 will be described in detail. Then, finally, a verification and evaluation experiment will be described in detail, which is carried out by an example of the method for producing a vertical organic light emitting transistor device according to the present invention to verify the effect of the present invention.

[0043] In the following description, the following description will be given: it is assumed that the wiring direction of the data line 35 and the current supply line 36 is the X direction, the wiring direction of the gate line 34 is the Y direction, the direction orthogonal thereto is the Z direction, and the side away from the substrate 2 (+Z direction) is the upper side.

[0044] (Overall structure)

[0045] The overall structure of the display 1 of the present embodiment will be explained. Figure 1 1 is a schematic diagram showing the overall structure of a display 1 of the present embodiment. The display 1 includes a substrate 2. On one surface of the substrate 2, a display area 2a and a peripheral area 2b are provided.

[0046] The substrate 2 is a material having translucency. Examples of such materials include glass substrates, quartz substrates, and organic resin substrates. Examples of materials for organic resin substrates include polyimide and similar materials. The organic resin substrate may have a thickness of several micrometers to tens of micrometers, which enables a flexible sheet display to be realized.

[0047] The display area 2a is an area for displaying images. In this embodiment, a plurality of pixels 3 are arranged in a matrix in the display area 2a. In addition, in the display area 2a, a scanning signal line 34 is provided for each pixel row, and a video signal line 35 and a power supply potential line 36 are provided for each pixel column. Figure 1 , however, a common potential line 37 to be described later is provided across the pixels 3.

[0048] The peripheral area 2b is an area outside the display area 2a. In the peripheral area 2b, a driving circuit 4, a large-scale integration (LSI) chip 5 and a terminal part 6 are provided. The driving circuit 4 is a circuit for driving the pixels 3 arranged in the display area 2a. The driving circuit 4 includes a scanning line driving circuit and a video line driving circuit not shown in the drawings. The LSI chip 5 controls the driving circuit 4. The terminal part 6 is provided to connect the display 1 to an external terminal such as a flexible printed circuit (FPC).

[0049] (Pixel Circuit)

[0050] Figure 2 3 is a diagram for explaining the circuit structure of each of the pixels 3 of this embodiment. Each of the pixels 3 has a selection transistor 30 and a light emitting transistor 31.

[0051] The selection transistor 30 controls the conduction between the video signal line 35 and the gate electrode 311 of the light emitting transistor 31 by a switching operation (on-off operation). The source electrode 301 of the selection transistor 30 is connected to the video signal line 35. The drain electrode 302 of the selection transistor 30 is connected to the gate electrode 311 of the light emitting transistor 31 (see Figure 3 ). The gate electrode 300 of the selection transistor 30 is connected to the scanning signal line 34 .

[0052] The light emitting transistor 31 emits light whose brightness depends on the voltage applied to the gate electrode 311. The source electrode 314 of the light emitting transistor 31 is connected to the power supply potential line 36. The drain electrode 316 of the light emitting transistor 31 is connected to the common potential line 37. The gate electrode 311 of the light emitting transistor 31 is connected to the drain electrode 302 of the selection transistor 30.

[0053] (Drive control)

[0054] A predetermined power supply potential is applied to the source electrode 314 of the light emitting transistor 31 via the power supply potential line 36. In addition, a predetermined common potential is applied to the drain electrode 316 of the light emitting transistor 31 via the common potential line 37. That is, a predetermined constant voltage is applied between the source electrode and the drain electrode (314, 316) of the light emitting transistor 31. When the voltage is applied to the gate electrode 311 of the light emitting transistor 31, the electric field from the gate electrode 311 is controlled, and the current between the source electrode and the drain electrode (314, 316) is controlled.

[0055] The scan line drive circuit sequentially selects each of the rows of pixels 3 based on a timing signal input from the LSI chip 5. At this time, the scan line drive circuit applies a voltage to the scan signal line 34 connected to the pixels 3 of the pixel row to turn on the selection transistor 30.

[0056] The video line driving circuit receives the video signal from the LSI chip 5, and applies a voltage depending on the video signal of the selected column of the pixel 3 to each of the video signal lines 35 based on the selection of the scanning signal line 34 by the scanning line driving circuit. The voltage is applied to the gate electrode 311 of the light emitting transistor 31 at the selected pixel column. In this way, a current depending on the voltage applied to the gate electrode 311 is supplied to the light emitting layer 315 between the source electrode and the drain electrode (314, 316) of the light emitting transistor 31. In this way, the light emitting transistor 31 connected to the selected scanning signal line 34 emits light with a brightness depending on the current.

[0057] (Pixel structure)

[0058] Figure 3It is a top view of one of the pixels 3 of the display 1 according to the present embodiment. Figure 4 is the pixel along Figure 3 The display 1 of the present embodiment is a so-called bottom emission type display 1 in which light emitted from the light emitting transistor 31 is extracted from the substrate 2 side. Each of the pixels 3 of the present embodiment includes a selection transistor 30, a light emitting transistor 31, a protective layer 32, and a bank 33.

[0059] The selection transistor 30 includes a gate electrode 300, a source electrode 301, a drain electrode 302, a gate insulating layer 303, and a semiconductor layer 304. The selection transistor 30 of the present embodiment has a so-called bottom gate top contact (BGTC) structure in which the gate electrode 300, the gate insulating layer 303, the semiconductor layer 304, and the source and drain electrodes (301, 302) are arranged in this order from the substrate 2 side.

[0060] It should be noted that the structure of the selection transistor 30 is not limited to the BGTC structure, and may be a bottom gate bottom contact (BGBC) structure, a top gate bottom contact (TGBC) structure, or a top gate top contact (TGTC) structure.

[0061] As the material of the semiconductor layer 304 of the selection transistor 30 , a silicon-based semiconductor, an oxide-based semiconductor, an organic semiconductor, or the like can be used.

[0062] The protective layer 32 is provided to cover and protect the selection transistor 30, and to electrically insulate the source electrode 301 and the drain electrode 302 from the electrodes provided as the upper layer. An inorganic insulating material can be used as the material of the protective layer 32. Examples of inorganic insulating materials include silicon nitride, silicon oxide, aluminum nitride, and aluminum oxide. The protective layer 32 is provided over the entire surface of the substrate 2. By providing the protective layer 32, the selection transistor 30 and the power supply potential line 36 are covered by the protective layer 32.

[0063] like Figure 3 As shown in FIG. 1 , the area constituting one pixel is mostly occupied by the light emitting transistor 31, and the selection transistor 30 is arranged as small as possible at the corner of the area constituting one pixel. Figure 4 In the cross-sectional view shown in , the light emitting transistor 31 is disposed on the protective layer 32 .

[0064] The light emitting transistor 31 includes a gate electrode 311 , a gate insulating layer 312 , a base layer 313 , a source electrode 314 , a light emitting layer 315 , and a drain electrode 316 .

[0065] The gate electrode 311 is provided on the protective layer 32. In one pixel, the gate electrode 311 is provided outside the region occupied by the selection transistor 30. In addition, the gate electrode 311 is connected to the drain electrode 302 of the selection transistor 30 via a contact hole 32a provided in the protective layer 32.

[0066] A material having translucency and conductivity is used as the material of the gate electrode 311 to transmit light emitted from the light emitting layer 315 to the substrate 2 side. Specifically, indium tin oxide (ITO), indium zinc oxide (IZO), or the like can be used as the material of the gate electrode 311. Alternatively, a metallic material having a thickness that can transmit light can be used as the material of the gate electrode 311.

[0067] The gate insulating layer 312 is provided on the upper side of the gate electrode 311. The gate insulating layer 312 is provided over the entire surface of the substrate 2. As a material of the gate insulating layer 312, the same material as the gate insulating layer 303 of the selection transistor 30 can be used.

[0068] The base layer 313 is disposed on the gate insulating layer 312. The base layer 313 has an opening 313a. The opening 313a is disposed on the power supply potential line 36. The base layer 313 is made of a dielectric material. Alternatively, the base layer 313 may be made of a material having radiation sensitivity and photosensitivity. The material of the base layer 313 is an organic material containing an aromatic compound, and examples of such organic materials that can be used include aromatic polymers, radiation-sensitive compositions containing polymers such as polyimides and photosensitizing agents, polymers containing cinnamic acid groups, and fluorine-based polymers having crosslinkable groups. It should be noted that the organic material used in this embodiment has an oxygen content of 1% by mass or less, but the oxygen content of the organic material may also be 1% by mass or greater than 1% by mass.

[0069] The source electrode 314 is provided on the foundation layer 313 and in contact with the foundation layer 313. The source electrode 314 is connected to the power supply potential line 36 provided below the foundation layer 313 via the opening 313a of the foundation layer 313.

[0070] The material of the source electrode 314 is a material containing a nanocarbon material. The nanocarbon material is graphene, fullerene or carbon nanotube, and the material of the source electrode 314 contains at least one of graphene, fullerene or carbon nanotube. The nanocarbon material is preferably a carbon nanotube. Single-wall carbon nanotubes (SWNT) or double-wall carbon nanotubes (double-wall carbon nanotubes) or multi-wall carbon nanotubes (multi-wall carbon nanotubes) can be used as the carbon nanotubes. The nanocarbon material is preferably a single-wall carbon nanotube. In the following, carbon nanotubes are sometimes abbreviated as "CNT".

[0071] The source electrode 314 is formed by applying a dispersion liquid containing a nanocarbon material (e.g., carbon nanotubes) and a dispersant. The dispersant is not particularly limited, but from the perspective of improving the dispersibility of the carbon nanotubes, a polyamic acid having a portion represented by the chemical formula (1) is preferably used. The chemical formula (1) is shown again for confirmation.

[0072] (Chemical formula 2)

[0073]

[0074] (where R 1 is a tetravalent organic group constituting a tetracarboxylic acid, R 2 is a divalent organic group constituting a diamine, and n is a positive integer. )

[0075] By R 1Specific examples of the tetravalent organic group representing and constituting the tetracarboxylic acid include: dianhydrides of aromatic tetracarboxylic acids, such as pyromellitic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6,7-anthracenetetracarboxylic acid, 1,2,5,6-anthracenetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3'4-biphenyltetracarboxylic acid, bis(3,4-dicarboxyphenyl) ether, 3,3'4,4'-benzophenonetetracarboxylic acid, 2,3,3'4,4'-diphenyl ... carboxylic acid, bis(3,4-dicarboxyphenyl)sulfone, bis(3,4-dicarboxyphenyl)methane, 2,2-bis(3,4-dicarboxyphenyl)propane, 1,1,1,3,3,3-hexafluoro-2,2-bis(3,4-dicarboxyphenyl)propane, bis(3,4-dicarboxyphenyl)dimethylsilane, bis(3,4-dicarboxyphenyl)diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid and 2,6-bis(3,4-dicarboxyphenyl)pyridine; The dianhydrides of tetracarboxylic acids having an alicyclic structure are, for example, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 2,3,5-tricarboxycyclopentylacetic acid and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid; and the dianhydrides of aliphatic tetracarboxylic acids, for example, 1,2,3,4-butanetetracarboxylic acid and similar materials. These acid dianhydrides as compounds can be used alone or in combination of two or more thereof.

[0076] By R 2Specific examples of the divalent organic group representing and constituting the diamine include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, diaminodiphenylmethane, diaminodiphenyl ether, 2,2'-diaminodiphenylpropane, bis(3,5-diethyl-4-aminophenyl)methane, diaminodiphenyl sulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)diphenylsulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane; alicyclic diamines such as bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane and 3,5-diaminobenzoic acid cholesteryl; aliphatic diamines such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane and 1,6-diaminohexane; and silicon diamines such as 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and the like. These diamines as compounds may be used alone or in combination of two or more thereof.

[0077] Furthermore, from the viewpoint that the ring structure of the cyclobutane ring is decomposed by light irradiation or heating to change the structure of the polyamic acid, thereby making it easy to remove the dispersant, R in the above chemical formula (1) 1 Preferably, it is a cyclobutane ring. In addition, the dispersant may contain an organic solvent as a dispersion medium.

[0078] The light-emitting layer 315 is a layer containing an organic electroluminescent (EL) (organic EL) material. The light-emitting layer 315 is disposed on the source electrode 314. The light-emitting layer 315 is disposed to cover the edge (rim) of the opening 33a of the dam 33 to be described later and the vicinity of the edge (vicinity). When electrons and holes are injected into the light-emitting layer 315 from the source electrode 314 and the drain electrode 316, respectively, the electrons and holes recombine. The excess energy thus released excites the light-emitting molecules in the light-emitting layer 315, and then light is emitted due to deexcitation. The light-emitting layer 315 may include a hole transport layer and an electron transport layer and similar layers so that the organic EL material layer is sandwiched between these layers.

[0079] The drain electrode 316 is disposed on the light emitting layer 315. The drain electrode 316 corresponds to Figure 2 0 shows a region of a portion of the common potential line 37. The pixels 3 have the common potential line 37 in common, and all the common potential lines 37 are electrically connected.

[0080] The material of the drain electrode 316 preferably includes a metallic material having high reflectance to reflect light emitted from the light emitting layer 315 toward the substrate 2. For example, aluminum, silver or the like can be used as such a metallic material having high reflectance.

[0081] The dam 33 is disposed on the base layer 313 and the source electrode 314. The dam 33 has an opening 33a, and when viewed from above, the dam 33 is disposed so that the edge 33b of the opening 33a covers the periphery of the source electrode 314 and the vicinity of the periphery. The material of the dam 33 is an insulating material. An inorganic insulating material, an organic insulating material or a combination thereof can be used as the insulating material. By providing the dam 33, a short circuit between the source electrode 314 and the drain electrode 316 can be prevented.

[0082] Although not shown, a protective layer may be provided over the drain electrode 316 to cover the entire surface of the substrate 2. The protective layer prevents the degradation of the properties of the light-emitting transistor 31 caused by the entry of moisture into the light-emitting layer 315. An inorganic insulating material may be used as the material of the protective layer. Examples of inorganic insulating materials include silicon nitride, silicon oxide, aluminum nitride, aluminum oxide, and a laminate of a combination of any two or more of these materials. It should be noted that a protective layer is not provided at the position of the LSI chip 5 and the terminal portion 6 in order to electrically connect to the external terminal.

[0083] (Production Method)

[0084] A method for producing the light emitting transistor 31 of the present embodiment, in particular, a method for producing the pixel 3 of the display 1 will be explained. Figures 5 to 12 Each is a top view showing a production process of the light emitting transistor 31 of the present embodiment.

[0085] First, if Figure 5 As shown in , a substrate 2 having a main surface on which a light-emitting transistor 31 is to be formed is prepared (corresponding to step (A)).

[0086] Then, if Figure 6As shown in , the selection transistor 30 is formed in a portion on one surface side of the substrate 2. The selection transistor 30 is formed by a process in which the gate electrode 300, the gate insulating layer 303, the semiconductor layer 304, and each of the source and drain electrodes (301, 302) are formed by film formation using materials of each of the gate electrode 300, the gate insulating layer 303, the semiconductor layer 304, and the source and drain electrodes (301, 302), resist application, exposure, development, and etching. The selection transistor 30 can be produced by a general method, and thus the method for producing the selection transistor 30 will not be described here in detail.

[0087] It should be noted that in this embodiment, Figure 6 As shown in , in the step of forming the selection transistor 30 , the power supply potential line 36 is formed simultaneously with the formation of the source electrode and the drain electrode ( 301 , 302 ).

[0088] Then, if Figure 7 As shown in , a protective layer 32 is formed. An inorganic insulating material is used as a material for the protective layer 32. Examples of the inorganic insulating material include silicon nitride, silicon oxide, aluminum nitride, and aluminum oxide. The protective layer 32 is formed using a film forming method such as chemical vapor deposition or sputtering. The protective layer 32 is formed over the entire surface of the substrate 2. By forming the protective layer 32, the selection transistor 30 and the power supply potential line 36 are covered by the protective layer 32.

[0089] After forming the protective layer 32, as Figure 8 As shown in FIG. 1 , a contact hole 32 a is formed in a region of the protective layer 32 located above the drain electrode 302 . The contact hole 32 a is formed to connect the gate electrode 311 of the light emitting transistor 31 and the drain electrode 302 of the selection transistor 30 .

[0090] Then, the light emitting transistor 31 is formed. First, Fig. 9 As shown in FIG. 1 , a gate electrode 311 is formed on the protective layer 32 . The gate electrode 311 is also formed on a contact hole 32 a formed by the protective layer 32 to be connected to the drain electrode 302 of the selection transistor 30 .

[0091] A material having translucency and conductivity is used as the material of the gate electrode 311. Specifically, ITO (indium tin oxide), IZO (indium zinc oxide), or the like can be used as the material of the gate electrode 311. Alternatively, a metallic material having a thickness that can transmit light can be used as the material of the gate electrode 311. The gate electrode 311 is formed by forming a film from the material of the gate electrode 311 through sputtering or the like and then removing unnecessary portions by etching.

[0092] After forming the gate electrode 311, as Figure 4 As shown in , a gate insulating layer 312 is formed. It should be noted that the gate insulating layer 312 is formed over the entire surface of the substrate 2, and therefore how the gate insulating layer 312 is formed is not schematically shown.

[0093] The same material as that of the gate insulating layer 303 of the selection transistor 30 can be used as the material of the gate insulating layer 312. The gate insulating layer 312 is formed using a film forming method such as chemical vapor deposition or sputtering.

[0094] After forming the gate insulating layer 312, as shown in FIG. Fig.10 As shown in FIG. 3 , a base layer 313 is formed. The base layer 313 is made of a dielectric material.

[0095] After forming the foundation layer 313, the opening 313a is formed by removing the foundation layer 313 in the region located above the power supply potential line 36. The opening 313a is formed by subjecting the foundation layer 313 to exposure and development.

[0096] Then, the contact hole 31a is formed in the region of the opening 313a. In this step, the contact hole 31a is formed by etching the one surface side of the substrate 2 using the base layer 313 having the opening 313a as a resist. At this time, the one surface side of the substrate 2 is etched until the power supply potential line 36 is exposed. In this way, the region of the gate insulating layer 312 and the protective layer 32 exposed by the opening 313a is removed, so that the contact hole 31a is formed.

[0097] The etching method is not particularly limited as long as an appropriate etching selectivity determined according to the etching rates of the base layer 313 and the gate insulating layer 312 and the protective layer 32 is achieved. As such an etching method, any one of plasma etching and wet etching can be used.

[0098] It should be noted that, as an alternative to the above-described method of patterning the base layer 313, the gate insulating layer 312, and the protective layer 32 by utilizing the photosensitivity of the base layer 313, a method in which the base layer 313 is completely cured by, for example, exposure or heating and then a photosensitive resist layer for patterning is separately formed on the base layer 313 may be used. In this case, when the photosensitive resist layer is a negative type, the solubility of the exposed area in the developer is reduced. Therefore, a photomask is formed to protect the area where the opening 313a is to be formed from light.

[0099] In the step of developing the photosensitive resist layer, the photosensitive resist layer is immersed in a developer. The exposed area does not dissolve in the developer, but the area protected from light in the exposure step dissolves. Thus, a resist opening is formed.

[0100] Then, the opening 313a and the contact hole 31a are formed in the region of the resist opening. In this step, the opening 313a and the contact hole 31a are formed by etching the one surface side of the substrate 2 using the photosensitive resist layer PR having the resist opening. At this time, the one surface side of the substrate 2 is etched until the power supply potential line 36 is exposed. In this way, the region of the base layer 313, the gate insulating layer 312, and the protective layer 32 exposed by the resist opening is removed so that the contact hole 31a is formed.

[0101] It should be noted that the etching method is not particularly limited, and any etching method may be used as long as an appropriate etching selectivity determined according to the etching rate of the photosensitive resist layer and the etching rates of the base layer 313, the gate insulating layer 312, and the protective layer 32 is achieved. As such an etching method, any of plasma etching and wet etching may be used.

[0102] After the contact hole 31a is formed, the remaining photosensitive resist layer (not shown) is removed. As described above, instead of utilizing the photosensitivity of the base layer 313, the contact hole 31a may be formed using a photosensitive resist layer formed separately for patterning.

[0103] After the contact hole 31a is formed in the etching step (or after the contact hole 31a is formed in the etching step and then the photosensitive resist layer is removed), a dispersion liquid containing a nanocarbon material (carbon material) is applied onto the base layer 313 formed on the main surface of the substrate 2, and thus, as Fig.10 As shown in , a pattern of source electrode 314 is formed on base layer 313 (corresponding to step (C)).

[0104] In this step, the pattern is formed on the base layer 313 by a coating film of a dispersion liquid containing a nanocarbon material using a printing technique such as casting, screen printing, or ink-jet printing. After the pattern is formed, the solvent is removed by drying, so that the source electrode 314 is formed (corresponding to step (D)).

[0105] When viewed from above, the pattern of the source electrode 314 is designed to overlap the opening 313a of the base layer 313. Fig.10 The contact hole 31 a shown in FIG. 1 is connected to the power supply potential line 36 .

[0106] After the solvent is removed by drying, a cleaning fluid is applied to the source electrode 314 formed on the main surface of the substrate 2 to remove the dispersant from the pattern formed by the coating film (corresponding to step (E)). In this step, instead of the above-mentioned method in which the pattern of the source electrode 314 is formed by printing, the following method can also be used: in the method, the dispersion liquid is applied to the entire surface of the base layer 313 formed on the main surface of the substrate 2 at one time, drying and cleaning are performed, and then a photosensitive resist layer for patterning is separately formed on the source electrode 314. In this case, after the photosensitive resist layer is formed, the conductive layer is removed by etching, and the remaining photosensitive resist layer (not shown) is removed.

[0107] It should be noted that the combination of the dispersant and the cleaning fluid is not particularly limited, but the dispersant is preferably an alkali-soluble polymer having a functional group to improve solubility in an alkaline aqueous solution, and the cleaning fluid is preferably an alkaline aqueous solution. Using an alkaline aqueous solution as the cleaning fluid allows the nano-carbon material that is unlikely to be dispersed in an alkaline aqueous solution to be selectively retained on the base layer 313. In addition, the step of using such an alkali-soluble polymer can share materials with the step of using another photosensitive resist layer developed using an alkaline aqueous solution, which significantly enhances productivity. For example, a potassium hydroxide (KOH) aqueous solution, a sodium hydroxide (NaOH) aqueous solution, a sodium carbonate aqueous solution, or a tetramethylammonium hydroxide (TMAH) aqueous solution can be suitably used as the alkaline aqueous solution.

[0108] The material of the dispersant may have a molecular structure that can improve the solubility in alkaline aqueous solution by causing decomposition or structural changes due to the reaction to light or heat. Using this dispersant makes it possible to further improve the efficiency of removing the dispersant from the pattern formed by the coating film by being exposed to light or applying heat to improve the solubility of the dispersant after forming the source electrode 314 and before applying the cleaning fluid. The molecular structure with this function may be, for example, a polyamic acid structure of a dispersant, the polyamic acid structure comprising a part (such as cyclobutane) decomposed by light or heat so that the entire structure of the polyamic acid can be changed. The dispersant may include an acid dissociable group. The acid dissociable group is a group that produces an acidic group (such as a carboxyl or phenolic hydroxyl group) due to the action of an acid. Examples of acid dissociable groups include a group with a tert-butoxy structure and a group with an acetal structure. The acid acting on the acid dissociable group is generated from an acid generator that produces an acid due to the action of light or heat. Therefore, in addition to the dispersant with an acid dissociable group, the dispersion also includes an acid generator.

[0109] Then, the bank 33 is formed. The material of the bank 33 is an insulating material. As the insulating material, an inorganic insulating material, an organic insulating material, or a combination thereof can be used. After a film is formed from the material of the bank 33, an unnecessary portion is removed to form the opening 33a.

[0110] Then, the light emitting layer 315 is formed on the source electrode 314. In this step, the light emitting layer 315 is formed at least in the opening 33a and the edge 33b of the dam 33 and the vicinity of the edge 33b in the pixel region by vapor deposition of an organic material in a state where a metallic mask is placed on the substrate 2.

[0111] Then, a drain electrode 316 is formed on the light emitting layer 315 to complete Figure 4 The light emitting transistor 31 of the present embodiment is shown in FIG. The material of the drain electrode 316 preferably includes a metallic material having a high reflectivity. For example, aluminum, silver or the like can be used as such a metallic material having a high reflectivity.

[0112] Although not shown, a protective layer may be formed on the drain electrode 316 to cover the entire surface of the substrate 2. An inorganic insulating material may be used as the material of the protective layer. Examples of inorganic insulating materials include silicon nitride, silicon oxide, aluminum nitride, aluminum oxide, and a laminate of any combination of two or more of these materials. It should be noted that in order to electrically connect to the external terminal, the protective layer is removed in the region where the LSI chip 5 and the terminal portion 6 are to be provided.

[0113] It will be obvious from reading the above description that the light-emitting transistor 31 of the present embodiment includes a gate electrode 311, a gate insulating layer 312 arranged on the gate electrode 311, a base layer 313 arranged on the gate insulating layer 312 and having dielectric properties, a source electrode 314 arranged to be in contact with the base layer 313 and containing a nanocarbon material, a light-emitting layer 315 arranged on the source electrode 314, and a drain electrode 316 arranged on the light-emitting layer 315.

[0114] In such a light emitting transistor 31, the base layer 313 has the ability to adsorb the nanocarbon material, which improves the adhesion between the base layer 313 and the source electrode 314. This enhances the processability of the source electrode 314 and the solvent resistance during the application of the photoresist layer or the developer resistance in the subsequent steps, and further makes it easy to control the voltage applied to the gate electrode 311 so that the current flows with the desired accuracy.

[0115] In addition, the base layer 313 of the light emitting transistor 31 has an opening 313a, and the source electrode 314 is connected to the power supply potential line 36 provided below the base layer 313 through the opening 313a. In such a light emitting transistor 31, a desired voltage can be applied to the source electrode 314 through the power supply potential line 36.

[0116] In addition, in the light emitting transistor 31, the base layer 313 has photosensitivity. In such a light emitting transistor 31, the opening 313a can be formed by subjecting the base layer 313 to exposure and development. That is, the production process of the light emitting transistor 31 can be simplified.

[0117] In addition, in the light emitting transistor 31, the nanocarbon material includes at least one of graphene and carbon nanotubes. In such a light emitting transistor 31, the adhesion between the base layer 313 and the source electrode 314 is further improved.

[0118] In addition, in the light emitting transistor 31, the nano carbon material is a carbon nano tube, and the carbon nano tube is a single-walled carbon nano tube. In such a light emitting transistor 31, the adhesion between the base layer 313 and the source electrode 314 is further improved.

[0119] In addition, in the light emitting transistor 31, the base layer 313 can be formed from the radiation-sensitive composition for forming the base layer by the steps to be described below. The base layer 313 formed by such a formation method has unique electrical properties, excellent adhesion to carbon nanotubes, excellent chemical resistance, and excellent flatness. In addition, in such a formation method, heating is performed at a temperature of 140° C. or lower, which prevents thermal degradation of the substrate and the device disposed on the substrate. Hereinafter, each of the steps will be described in detail.

[0120] (Step (1))

[0121] In this step, a coating film is formed on the gate insulating layer 312 using a radiation-sensitive composition. Specifically, the coating film of the radiation-sensitive composition is formed by applying the radiation-sensitive composition onto the surface of the gate insulating layer 312. It should be noted that in this step, a prebaking treatment is preferably performed to remove the solvent contained in the coating film.

[0122] Devices such as a selection transistor are provided below the gate insulating layer 312. As described above, this formation method makes it possible to prevent these devices from being degraded by heat.

[0123] For example, a suitable method such as spray coating, roller coating, spin coating, slit die coating, rod coating or inkjet coating can be used as an application method. Among these methods, inkjet coating is preferably used as an application method. The conditions of prebaking depend on, for example, the type and ratio of each component used, but can be, for example, 60° C. to 130° C. and about 30 seconds to 10 minutes. The thickness of the coating film formed after prebaking is preferably 0.1 μm to 5 μm, more preferably 0.1 μm to 1 μm, and even more preferably 0.2 μm to 0.4 μm.

[0124] (Step (2))

[0125] In this step, part of the coating film is subjected to radiation irradiation (exposure). Specifically, the coating film formed in step (1) is irradiated with radiation through a mask having a predetermined pattern. Depending on the pattern of the mask used, a pattern for forming contact holes, a pattern for forming lines and spaces, or the like can be formed. Examples of the radiation used at this time include ultraviolet (UV), far ultraviolet, X-rays, and charged particle radiation. The mask used may be a multi tone mask such as a half tone mask or a gray tone mask.

[0126] Examples of ultraviolet rays include g-rays (wavelength: 436 nanometers), i-rays (wavelength: 365 nanometers), and KrF excimer laser light (wavelength: 248 nanometers). Examples of X-rays include synchrotron radiation and the like. Examples of charged particle radiation include electron beams and the like. Among these radiations, ultraviolet rays are preferred, and ultraviolet rays having a wavelength of 200 nanometers or more and 380 nanometers or less are more preferred. The exposure amount of the radiation is preferably 1,000 joules / square meter (J / m 2 ) to 20,000 J / m².

[0127] In some cases, post exposure baking (PEB) may be performed after exposure.

[0128] (Step (3))

[0129] In this step, the coating film irradiated with radiation is developed. Specifically, the coating film irradiated with radiation in step (2) is developed with a developer to remove the portion irradiated with radiation. For example, an alkaline aqueous solution obtained by dissolving potassium hydroxide, sodium carbonate, triethanolamine, tetramethylammonium hydroxide (TMAH) or tetraethylammonium hydroxide or an organic solvent (e.g., ethanol, isopropyl alcohol, acetone, ethyl acetate, or butyl acetate) in water can be used as a developer.

[0130] For example, a proper method such as a puddle method, a dipping method, a shake dipping method or a showering method can be used as a developing method. The developing time depends on the composition of the radiation-sensitive composition, but can be, for example, 30 to 120 seconds.

[0131] (Step (4))

[0132] In this step, the coating film after step (3) may be heated. The coating film is cured by heat treatment (post-baking) using a heating device such as a hot plate or an oven.

[0133] The upper limit of the heating temperature in this step is 140° C., and the heating temperature may be 130° C., 125° C., or 115° C. This forming method allows the coating film to have an excellent shape even when heated at such a relatively low temperature.

[0134] Furthermore, in the light emitting transistor 31 , the source electrode 314 formed on the organic material layer may be formed from a composition including a nano-carbon material through the following steps.

[0135] For example, suitable methods such as spray coating, roller coating, spin coating, slit die coating (slit coating), rod coating, solution dipping or inkjet coating can be used as a method for applying a composition comprising nano-carbon material. The nano-carbon material layer is formed to have a specific thickness by a predetermined method. It should be noted that, in order to improve purity, the nano-carbon material layer is preferably subjected to a baking step to remove the solvent, or subjected to a solution dipping step to remove the dispersant. Among the above-mentioned application methods, from the perspective of the thickness uniformity of the coating film and the saving of liquid, slit die coating or inkjet coating are preferred. From the perspective that electrode patterning can only be implemented by applying, inkjet coating is more preferred.

[0136] Forming the base layer 313 using this method may allow the source electrode 314 formed on the upper side of the base layer 313 to have unique electrical properties, excellent adhesion to the base layer 313, excellent chemical resistance, and excellent flatness.

[0137] The display 1 of the present embodiment includes a substrate 2 and pixels 3 arranged on one surface of the substrate 2 , and each of the pixels 3 has any one of the above-mentioned light emitting transistors 31 .

[0138] In such a display 1, the base layer 313 of the light emitting transistor 31 has a dielectric property that improves adhesion between the base layer 313 and the source electrode 314. This makes it easy to pass a current through the light emitting transistor 31 with desired accuracy when a voltage depending on a video signal is applied to the gate electrode 311. Therefore, it is not necessary to provide a compensation circuit or to provide a transistor or a capacitor separately for each pixel 3 in order to pass a current through the light emitting transistor 31 with desired accuracy.

[0139] The method for producing the light-emitting transistor 31 of this embodiment includes: forming a gate electrode 311 on one surface side of the substrate 2; after forming the gate electrode 311, forming a gate insulating layer 312 on the one surface side; after forming the gate insulating layer 312, forming a base layer 313 with dielectric properties on the one surface side; forming a source electrode 314 containing nanocarbon material on the base layer 313; forming a light-emitting layer 315 on the source electrode 314; and forming a drain electrode 316 on the light-emitting layer 315.

[0140] Such a method for producing the light emitting transistor 31 makes it possible to produce the light emitting transistor 31 in which the base layer 313 has dielectric properties and thus achieves excellent adhesion with the source electrode 314. This improves the production yield.

[0141] In the above-mentioned production method, the base layer 313 is photosensitivity, and before forming the gate insulating layer 312, a power supply potential line 36 is formed on the one surface side; after the base layer 313 is formed, the base layer 313 is subjected to exposure and development to remove the area of ​​the base layer 313 located above the power supply potential line 36; a contact hole 31a is formed by etching the one surface side using the base layer 313 as an anti-etching agent until the power supply potential line 36 is exposed; and a source electrode 314 connected to the power supply potential line 36 via the contact hole 31a is formed.

[0142] In this method for producing the light emitting transistor 31, the base layer 313 has photosensitivity and thus serves as a resist. Therefore, the contact hole 31a can be formed without performing complicated steps such as applying a resist onto the base layer 313, exposure, development, etching, and resist removal. This simplifies the production process.

[0143] In addition, in the above production method, the nanocarbon material includes at least one of graphene and carbon nanotubes. This method for producing the light-emitting transistor 31 makes it possible to produce a light-emitting transistor 31 in which the bonding between the base layer 313 and the source electrode 314 is more excellent. This will further improve the production yield.

[0144] In addition, in the above production method, the nanocarbon material is a carbon nanotube, and the carbon nanotube is a single-walled carbon nanotube. This method for producing the light-emitting transistor 31 makes it possible to produce a light-emitting transistor 31 in which the bonding between the base layer 313 and the source electrode 314 is more excellent. This will further improve the production yield.

[0145] The method for producing the light emitting transistor 31 of the present embodiment includes forming a plurality of pixels 3 on one surface of a substrate 2 , each of the plurality of pixels 3 including the light emitting transistor 31 formed by the above method.

[0146] Since the base layer 313 constituting the light emitting transistor 31 of the pixel 3 has a dielectric property, this method for producing the light emitting transistor 31 makes it possible to produce the light emitting transistor 31 in which the adhesion between the base layer 313 and the source electrode 314 is excellent. This improves the production yield.

[0147] In addition, in this method for producing the light emitting transistor 31, the base layer 313 has photosensitivity and can therefore be used as a resist. Therefore, the contact hole 31a can be formed without performing complicated steps such as applying a resist to the base layer 313, exposing, developing, etching, and removing the resist. This simplifies the production process.

[0148] (Verification and evaluation experiment)

[0149] Finally, verification and evaluation experiments will be described, which were carried out to determine how much the production method according to the present invention affects the dispersibility of carbon nanotubes as nanocarbon material applied to a substrate.

[0150] 1. Polymer Synthesis

[0151] (Synthesis Example 1: Synthesis of polyamic acid)

[0152] A polyamic acid having a hydrocarbon group on a side chain (hereinafter referred to as "polymer (paa-1)") is obtained by the synthesis method described in Patent Document 2 mentioned above.

[0153] (Synthesis Example 2: Synthesis of polyamic acid)

[0154] A photodegradable polyamic acid having a hydrocarbon group on a side chain (hereinafter referred to as "polymer (paa-2)") is obtained by the synthesis method described in Patent Document 3 mentioned above.

[0155] (Comparative Synthesis Example 1: Synthesis of Polyimide)

[0156] N-methyl-2-pyrrolidone (NMP) was added to the polyamic acid solution obtained in the same manner as in Synthesis Example 1 above. A predetermined imidization agent was added to the solution, and the mixture was subjected to a reaction for a predetermined time by heating at 110° C. to obtain a polyimide (hereinafter referred to as “polymer (PI-1)”). The obtained polymer (PI-1) had an imidization ratio of 50%.

[0157] 2. Preparation and evaluation of dispersed compositions containing CNTs

[0158] (1) Preparation of dispersion composition

[0159] First, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 50 parts by mass of the polymer (paa-1) obtained as a dispersant in Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S1).

[0160] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 100 parts by mass of the polymer (paa-1) obtained as a dispersant in Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S-2).

[0161] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 500 parts by mass of the polymer (paa-1) obtained as a dispersant in Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S-3).

[0162] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 1,000 parts by mass of the polymer (paa-1) obtained as a dispersant in Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S-4).

[0163] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 5,000 parts by mass of the polymer (paa-1) obtained as a dispersant in Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S-5).

[0164] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 500 parts by mass of the polymer (paa-2) obtained as a dispersant in Synthesis Example 2. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (S-6).

[0165] Then, 100,000 parts by mass of NMP as a solvent was added to a container containing 10 parts by mass of single-walled carbon nanotubes (SWNT) and 500 parts by mass of the polymer (PI-1) obtained as a dispersant in Comparative Synthesis Example 1. Then, the mixture was subjected to ultrasonic dispersion for 60 minutes to prepare a dispersion composition (Cl).

[0166] (2) Evaluation of CNT dispersion

[0167] The dispersion compositions (S-1) to (C-1) obtained in (1) above were allowed to stand on a flat surface in an environment at 25° C. The CNT dispersibility of the dispersion compositions was evaluated according to the following criteria.

[0168] Most Excellent (A): Even after 1 week, the dispersion composition maintained its original dispersion state, and CNTs did not precipitate.

[0169] Excellent (B): The dispersion composition maintains its original dispersion state without sedimentation of CNTs for up to 3 days.

[0170] Good (C): The dispersion composition maintains its original dispersion state for up to 1 day without sedimentation of CNTs.

[0171] Fair (D): The dispersion composition maintains its original dispersion state for up to 3 hours without sedimentation of the CNTs.

[0172] Bad (E): CNTs settle or flocculate within 3 hours.

[0173] As a result, the CNT dispersibility of the dispersion compositions (S-1) to (S-6) and (C-1) was evaluated as "most excellent (A)".

[0174] (3) Evaluation of CNT dispersion stability (durability)

[0175] A dispersion composition was prepared in the same manner as in (1) above. The obtained dispersion composition was allowed to stand on a flat surface in a 40° C. environment to observe its dispersion state over time. The CNT dispersion stability of the dispersion composition was evaluated according to the following criteria.

[0176] Most Excellent (A): Even after 1 week, the dispersion composition maintained its original dispersion state, and CNTs did not precipitate.

[0177] Excellent (B): The dispersion composition maintains its original dispersion state without sedimentation of CNTs for up to 3 days.

[0178] Good (C): The dispersion composition maintains its original dispersion state for up to 1 day without sedimentation of CNTs.

[0179] Fair (D): The dispersion composition maintains its original dispersion state for up to 3 hours without sedimentation of the CNTs.

[0180] Bad (E): CNTs settle or flocculate within 3 hours.

[0181] As a result, the CNT dispersion stability of the dispersion compositions (S-1) to (S-6) and (C-1) was evaluated as "most excellent (A)".

[0182] (4) Evaluation of CNT (carbon nanotube) application properties

[0183] Each of the dispersion compositions (S-1) to (C-1) obtained in (1) above was applied to a base layer 313 formed on a glass substrate by spin coating and dried on a hot plate at 80° C. for 10 minutes to form a coating film having a thickness of 0.1 μm as measured at the center of the substrate. This coating film was observed under a microscope with a magnification of 50 times to determine whether the coating film had thickness unevenness and pinholes. The application properties were evaluated according to the following criteria.

[0184] Most Excellent (A): Neither thickness unevenness nor pinholes were observed.

[0185] Good (B): At least one of thickness unevenness and pinholes is slightly observed.

[0186] Bad (C): At least one of thickness unevenness and pinholes was clearly observed.

[0187] As a result, since neither thickness unevenness nor pinholes were observed, the application properties of the dispersion compositions (S-3) to (S-5) and (C-1) were evaluated as "most excellent (A)". Since thickness unevenness was slightly observed, the application properties of the dispersion compositions (S-1) and (S-2) were evaluated as "good (B)".

[0188] (5) Evaluation of dispersant removability

[0189] Each of the dispersion compositions (S-1) to (C-1) obtained in (1) above was applied to a base layer 313 formed on a glass substrate by spin coating and dried on a hot plate at 80° C. for 10 minutes to form a coating film having a thickness of 0.1 μm as measured at the center of the substrate. In addition, in the case of (S-6), the coating film was irradiated with 1 joule of ultraviolet light having a wavelength of 260 nanometers using a UV lamp. The coating film was immersed in an aqueous sodium hydroxide solution for 1 minute and the surface of the coating film was observed using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Corporation).

[0190] Fig.11 and Fig.12 Each is an AFM photograph of the surface of a substrate. Fig.11 is an example of a photograph of a surface of a substrate having irregularities caused by CNTs, and Fig.12 is an example of a photograph of the surface of a substrate in which irregularities caused by CNTs (ie, CNTs are covered with a resin, a dispersant) were not observed using AFM. The dispersant removability was evaluated according to the following criteria.

[0191] Good (A): Fig.11 As shown in , CNTs (carbon nanotubes) are exposed by removing the dispersant from the surface.

[0192] General (B): Fig.12 As shown in , some CNTs are exposed.

[0193] Bad (C): The surface was covered with resin, and thus CNTs were not exposed, or evaluation could not be performed due to poor film formation.

[0194] As a result, since the dispersant was removed from the surface and the CNT (carbon nanotube) was exposed, the dispersion compositions (S-2) to (S-4) and (S-6) were evaluated as "good (A)". Since the CNT was exposed, but flocculation of the CNT was observed, the dispersion composition (S1) was evaluated as "general (B)". Since the CNT was exposed, but the surface of some CNTs was covered with resin, the dispersion composition (S-5) was evaluated as "general (B)". Since the surface was covered with the dispersant and the CNT was not exposed, the dispersion composition (C1) was evaluated as "poor (C)".

[0195] The above results are summarized in Table 1 below.

[0196] [Table 1]

[0197]

Claims

1. A method for producing a vertical organic light emitting transistor device, comprising: Step (A), in which a substrate is prepared, the substrate having a major surface on which the vertical organic light emitting transistor device is to be formed; step (B) in which an organic material including a polymer having a hydrocarbon group is applied onto the main surface of the substrate; step (C), in which a dispersion liquid containing a dispersant and a carbon material is applied onto the organic material layer formed in step (B); Step (D), in which the coating film formed in step (C) is dried; as well as Step (E), in which, after performing step (D), a cleaning fluid is applied to remove the dispersant. 2 . The method for producing a vertical organic light emitting transistor device according to claim 1 , wherein the dispersion liquid contains the dispersant in an amount of 1,000% by mass to 100,000% by mass based on the amount of the carbon material. 3 . The method for producing a vertical organic light emitting transistor device according to claim 1 , wherein the carbon material is at least one selected from carbon nanotubes, graphene, and fullerene.

4. The method for producing a vertical organic light emitting transistor device according to claim 3, wherein the carbon material is a carbon nanotube.

5. The method for producing a vertical organic light emitting transistor device according to claim 1, wherein the dispersant is a polymer having a moiety represented by the following chemical formula (1), and the dispersion liquid is an organic solvent: (Chemical formula 1) (where R 1 is a tetravalent organic group constituting a tetracarboxylic acid, R 2 is a divalent organic group constituting a diamine, and n is a positive integer).

6. The method for producing a vertical organic light emitting transistor device according to claim 5, wherein in the portion of the dispersant represented by the above chemical formula (1), R 1 It is a cyclobutane ring. 7 . The method for producing a vertical organic light emitting transistor device according to claim 5 , wherein the dispersant comprises an acid dissociable group. 8 . The method for producing a vertical organic light emitting transistor device according to claim 1 , wherein the organic material including the polymer having a hydrocarbon group has an oxygen content of 1% by mass or less.

9. The method for producing a vertical organic light-emitting transistor device according to claim 1, wherein in the step (C), the dispersion is applied to the organic material layer by any one of application methods including spin coating, slit coating, rod coating, spray coating and inkjet coating.

10. The method for producing a vertical organic light emitting transistor device according to claim 1, wherein the cleaning fluid is an alkaline aqueous solution.

11. A display comprising a vertical organic light emitting transistor device produced by the production method according to claim 1. 12 . The method for producing a vertical organic light emitting transistor device according to claim 2 , wherein the carbon material is at least one selected from carbon nanotubes, graphene, and fullerene.

13. The method for producing a vertical organic light emitting transistor device according to claim 12, wherein the carbon material is a carbon nanotube. 14 . The method for producing a vertical organic light emitting transistor device according to claim 6 , wherein the dispersant comprises an acid dissociable group.

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