JP2006024790A - Organic thin film transistor, its manufacturing method, active matrix type display using the same and radio identification tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film transistor and its manufacturing method in which a reliability for heat and a mechanical stress can be enhanced, and provide an active matrix type display using the same and a radio identification tag. <P>SOLUTION: The organic thin film transistor (10) contains a semiconductor layer (5) composed of an organic semiconductor material, and an insulating layer (3) composed of an organic insulating material. The organic thin film transistor (10) further comprises a first mixture layer (4) composed of the organic semiconductor material constituting the semiconductor layer (5) and the organic insulating material constituting the insulating layer (3), between the semiconductor layer (5) and the insulating layer (3). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic thin film transistor using an organic material for a semiconductor layer and an insulating layer, a manufacturing method thereof, an active matrix display using the organic thin film transistor, and a wireless identification tag.

  Currently, thin film transistors (hereinafter referred to as “TFTs”) are used as drive elements for active matrix liquid crystal displays and the like. In general, a TFT is configured such that a current flowing between a source electrode and a drain electrode provided in contact with a semiconductor layer is applied to the semiconductor layer from a gate electrode provided via an insulating layer. It can be controlled by an electric field.

  As a constituent material of a semiconductor layer of a TFT that is currently in practical use, amorphous silicon, low-temperature polysilicon, or the like, which is inexpensive, is used although it is inferior to crystalline silicon in terms of characteristics. Moreover, silicon oxide, silicon nitride, or the like is used as a constituent material of an insulating layer of a TFT that is currently in practical use. The manufacturing process of TFTs using these constituent materials is a high-cost process because it requires a large-scale apparatus used for plasma CVD and the like, and a thin film control apparatus for precision processing. There is a limit to the materials that can be used because it includes processes with processing temperatures in excess of 350 ° C.

On the other hand, in recent years, organic semiconductors have attracted attention as a semiconductor material for TFTs, and TFTs (organic TFTs) using various organic semiconductors have been proposed (see, for example, Patent Document 1). An organic semiconductor can be formed by a low-cost process such as a spin coating method, an ink-jet printing method, a dip coating method, and the like, and can be expected to be formed by a low-temperature process as compared with the inorganic semiconductor described above. In addition, since the low-cost process and the low-temperature process described above are applicable, it is possible to form TFTs on a flexible substrate or a large-area substrate, thereby enabling a sheet-like or paper-like display, Applications are expected to expand to large screen displays. Furthermore, since the organic TFT is thin and lightweight, application to a radio identification tag such as a radio frequency identification (RFID) tag is also expected.
JP-A-9-232589

  However, the material constituting the organic TFT often deteriorates due to delamination that occurs between the semiconductor layer and the insulating layer, between the semiconductor layer and the substrate, etc., when heat or mechanical stress is repeatedly applied. There was still a problem with reliability. The present invention has been made in order to solve the above-described conventional problems. An organic TFT capable of improving reliability against heat and mechanical stress, a manufacturing method thereof, and an active matrix display using the same. And providing a wireless identification tag.

  The first organic TFT of the present invention is an organic TFT including a semiconductor layer made of an organic semiconductor material and an insulating layer made of an organic insulating material, and is a first mixed material made of the organic semiconductor material and the organic insulating material. The semiconductor layer and the insulating layer are further laminated via the first mixed layer.

  The second organic TFT of the present invention is an organic TFT including a plastic substrate, a semiconductor layer made of an organic semiconductor material, and an insulating layer made of an organic insulating material, wherein the material constituting the plastic substrate and the organic semiconductor A second mixed layer made of a material or the organic insulating material is further provided, and the plastic substrate and the semiconductor layer or the insulating layer are laminated via the second mixed layer.

In the organic TFT manufacturing method of the present invention, an organic semiconductor material and an organic insulating material are dissolved in a solvent for forming a semiconductor layer and a solvent for forming an insulating layer, respectively. A method for producing an organic TFT, comprising: preparing a solution, applying the semiconductor layer film forming solution and the insulating layer film forming solution on a substrate, and laminating the semiconductor layer and the insulating layer; The inorganic / organic ratio in the organic conceptual diagram of the solvent for the solvent is the (I / O) _{semiconductor layer,} and the inorganic / organic ratio in the organic conceptual diagram of the solvent for forming the insulating layer is the (I / O) _{insulating layer} . In this case, the value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} is 0.1 to 0.3.

  Here, the “inorganic / organic ratio (I / O) in the organic conceptual diagram” is a parameter that represents a measure of the hydrophilicity / lipophilicity of the solvent, and the larger the value of the inorganic / organic ratio, the more the polarity. Highly hydrophilic. The inorganic / organic ratio is described in detail in “Organic Conceptual Diagram” (Yoshio Koda, Sankyo Publishing, 1984).

  The active matrix display of the present invention includes a plurality of the organic TFTs of the present invention as pixel switching elements. The wireless identification tag of the present invention is a wireless identification tag including an integrated circuit portion, and the integrated circuit portion is provided with the organic TFT of the present invention.

  According to the organic TFT of the present invention, since the first or second mixed layer is provided, the adhesion between the layers is increased, and the reliability against heat and mechanical stress can be improved. Moreover, according to the manufacturing method of the organic TFT of this invention, the organic TFT of this invention can be manufactured easily. In addition, since the active matrix display and the wireless identification tag of the present invention each include the organic TFT of the present invention, reliability against heat and mechanical stress can be improved.

  The first organic TFT of the present invention includes a semiconductor layer made of an organic semiconductor material and an insulating layer made of an organic insulating material. As the organic semiconductor material, for example, a low molecular organic semiconductor material such as linear acene or π conjugated oligomer, or a high molecular organic semiconductor material such as π conjugated polymer can be preferably used. As the organic insulating material, for example, a polymer organic insulating material such as polyvinylphenol or cyanoethyl pullulan can be preferably used. In addition, the suitable thickness of the said semiconductor layer and the said insulating layer is 10 nm-300 nm and 50 nm-3 micrometers, respectively.

  The first organic TFT of the present invention further includes a first mixed layer made of the organic semiconductor material and the organic insulating material, and the semiconductor layer and the insulating layer are interposed via the first mixed layer. Are stacked. Thereby, the adhesiveness between the said semiconductor layer and the said insulating layer becomes high, and the reliability with respect to a heat | fever and mechanical stress can be improved. A suitable thickness of the first mixed layer is 10 to 100 nm. When the thickness is less than 10 nm, the adhesion between the semiconductor layer and the insulating layer is low. On the other hand, when it exceeds 100 nm, carrier mobility becomes low. The thickness of the first mixed layer can be confirmed by an Ar sputtering method using an X-ray photoelectron spectrometer (for example, JPS-90MX MICRO manufactured by JEOL Ltd.).

  The second organic TFT of the present invention includes a plastic substrate, a semiconductor layer made of an organic semiconductor material, and an insulating layer made of an organic insulating material. The plastic substrate is not particularly limited. For example, a flexible substrate such as polyethylene terephthalate (PET) having a thickness of 0.1 to 10 mm is preferable. Suitable materials of the organic semiconductor material and the organic insulating material and suitable thicknesses of the semiconductor layer and the insulating layer are the same as those of the first organic TFT of the present invention described above.

  The second organic TFT of the present invention further includes a second mixed layer composed of the material constituting the plastic substrate and the organic semiconductor material or the organic insulating material, and the plastic substrate and the semiconductor layer or the insulating material. The layers are stacked via the second mixed layer. Thereby, the adhesiveness between the said plastic substrate and the said semiconductor layer or the said insulating layer becomes high, and the reliability with respect to a heat | fever and mechanical stress can be improved. A suitable thickness of the second mixed layer is 10 nm or more. When the thickness is less than 10 nm, the adhesion between the plastic substrate and the semiconductor layer or the insulating layer is lowered. The thickness of the second mixed layer can be confirmed by observing a cross section using a scanning electron microscope (SEM).

In the organic TFT manufacturing method of the present invention, an organic semiconductor material and an organic insulating material are dissolved in a solvent for forming a semiconductor layer and a solvent for forming an insulating layer, respectively. A solution is prepared, and the semiconductor layer film forming solution and the insulating layer film forming solution are applied onto a substrate to laminate the semiconductor layer and the insulating layer. At this time, the method for producing the organic TFT of the present invention is such that the inorganic / organic ratio in the organic conceptual diagram of the solvent for forming a semiconductor layer is an (I / O) _{semiconductor layer,} and the organic solvent for forming the insulating layer is organic. the inorganic / organic ratio in conceptual diagram when the (I / O) _{insulating layer,} (I / O) the value of the _{semiconductor layer} / (I / O) _{insulating layer} is 0.1 to 0.3 A solvent for forming a semiconductor layer and the solvent for forming an insulating layer are used. Thereby, the first organic TFT of the present invention described above can be easily manufactured. That is, when the value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} is 0.1 to 0.3, the semiconductor layer forming solvent and the insulating layer forming solvent are Therefore, when the semiconductor layer and the insulating layer are stacked, the respective solvents are mixed at the interface, and the first layer made of the organic semiconductor material and the organic insulating material is interposed between the layers. A mixed layer can be formed easily. Moreover, when manufacturing by this manufacturing method, the thickness of the said 1st mixed layer can be easily controlled by adjusting the value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} suitably.

  When manufacturing the above-described second organic TFT of the present invention, the solubility of the material for forming the plastic substrate to be used in the solvent for forming the semiconductor layer or the solvent for forming the insulating layer is taken into consideration. By selecting as appropriate, the thickness of the second mixed layer can be easily controlled.

  Further, the organic TFT manufacturing method of the present invention includes a spin coating method, an ink jet printing method, a dip coating method, and a casting method when the semiconductor layer film forming solution and the insulating layer film forming solution are applied onto the substrate. It is preferable to use at least one of them because the manufacturing cost can be reduced.

  In the organic TFT manufacturing method of the present invention, it is preferable that the semiconductor layer film forming solution and the insulating layer film forming solution are applied on the substrate after passing through a filter for removing impurities. According to this method, it is possible to prevent variations in electrical characteristics and a decrease in yield due to contamination of impurities such as dust.

  In the method for producing an organic TFT of the present invention, it is preferable that the semiconductor layer film forming solution and the insulating layer film forming solution are defoamed and then applied onto the substrate. According to this method, variations in electrical characteristics due to pinholes, a decrease in yield, and the like can be prevented.

  The organic TFT manufacturing method of the present invention is preferably performed in a dry inert gas atmosphere when forming the semiconductor layer and the insulating layer. According to this method, since water and oxygen that cause deterioration of the organic material can be eliminated, an organic TFT having good electrical characteristics can be provided stably.

  Further, in the organic TFT manufacturing method of the present invention, when the semiconductor layer film forming solution and the insulating layer film forming solution are applied onto the substrate by spin coating, the respective solvents (the semiconductor layer film forming) are used. The solvent is preferably used in an atmosphere of the solvent for forming the insulating layer or the solvent for forming the insulating layer. According to this method, since the evaporation of the solvent can be prevented, the film thicknesses of the semiconductor layer and the insulating layer can be easily controlled. In this case, it is preferable to use a solvent having a boiling point of 100 ° C. or less as the solvent for forming the semiconductor layer and the solvent for forming the insulating layer.

  The active matrix display of the present invention includes a plurality of the organic TFTs of the present invention as pixel switching elements. Thereby, the reliability with respect to a heat | fever and mechanical stress can be improved. In addition, when the active matrix display of the present invention is used in portable electronic devices such as notebook computers, mobile phones, digital cameras, and digital video cameras, the impact resistance of the portable electronic devices can be improved.

  The wireless identification tag of the present invention includes an integrated circuit portion, and the integrated circuit portion is provided with the organic TFT of the present invention. Thereby, the reliability with respect to a heat | fever and mechanical stress can be improved. In addition, since the wireless identification tag of the present invention has high reliability against mechanical stress, it can be attached to various shapes and materials. Hereinafter, embodiments of the present invention will be described in detail.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 to be referred to is a cross-sectional view of the organic TFT according to the first embodiment. The organic TFT according to the first embodiment is an embodiment of the first organic TFT of the present invention described above.

  As shown in FIG. 1, the organic TFT 10 according to the first embodiment includes a plastic substrate 1, a gate electrode 2 provided on the plastic substrate 1, and organic insulation sequentially stacked on the plastic substrate 1 and the gate electrode 2. A gate insulating layer 3 made of a material, a first mixed layer 4 and a semiconductor layer 5 made of an organic semiconductor material, and a source electrode 6 and a drain electrode 7 provided on the semiconductor layer 5 separately from each other are provided. The first mixed layer 4 is formed by mixing an organic semiconductor material constituting the semiconductor layer 5 and an organic insulating material constituting the gate insulating layer 3. As a result, the organic TFT 10 has higher adhesion between the semiconductor layer 5 and the gate insulating layer 3 than the conventional organic TFT, and can improve the reliability with respect to heat and mechanical stress. The gate insulating layer 3 corresponds to an “insulating layer” in the claims.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 to be referred to is a cross-sectional view of the organic TFT according to the second embodiment. The organic TFT according to the second embodiment is an embodiment of the first organic TFT of the present invention described above. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 2, the organic TFT 20 according to the second embodiment includes a plastic substrate 1, a source electrode 6 and a drain electrode 7 provided on the plastic substrate 1 separately from each other, a plastic substrate 1, and a source electrode 6. And the semiconductor layer 5, the first mixed layer 4 and the gate insulating layer 3 sequentially stacked on the drain electrode 7, and the gate electrode 2 provided on the gate insulating layer 3. Thereby, since the organic TFT 20 includes the first mixed layer 4 as compared with the conventional organic TFT, the adhesion between the semiconductor layer 5 and the gate insulating layer 3 is increased, and reliability with respect to heat and mechanical stress is increased. Can be improved.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 to be referred to is a cross-sectional view of the organic TFT according to the third embodiment. The organic TFT according to the third embodiment is an embodiment of the second organic TFT of the present invention described above. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3, the organic TFT 30 according to the third embodiment has the same structure as that of the organic TFT 10 (see FIG. 1) according to the first embodiment, but does not include the first mixed layer 4 and is insulated from the plastic substrate 1. Between the layer 3, a second mixed layer 31 made of a material constituting the plastic substrate 1 and an organic insulating material constituting the gate insulating layer 3 is provided. Other configurations are the same as those of the organic TFT 10 according to the first embodiment. Thereby, compared with the conventional organic TFT, the organic TFT 30 has higher adhesion between the plastic substrate 1 and the gate insulating layer 3, and can improve the reliability with respect to heat and mechanical stress.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 4 to be referred to is a cross-sectional view of the organic TFT according to the fourth embodiment. The organic TFT according to the fourth embodiment is an embodiment of the second organic TFT of the present invention described above. The same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, the organic TFT 40 according to the fourth embodiment includes the plastic substrate 1 and the semiconductor layer without the first mixed layer 4 in the configuration of the organic TFT 20 (see FIG. 2) according to the second embodiment. 5 is provided with a second mixed layer 41 made of a material constituting the plastic substrate 1 and an organic semiconductor material constituting the semiconductor layer 5. Other configurations are the same as those of the organic TFT 20 according to the second embodiment. Thereby, compared with the conventional organic TFT, the organic TFT 40 has higher adhesion between the plastic substrate 1 and the semiconductor layer 5 and can improve the reliability against heat and mechanical stress.

  The organic TFT according to one embodiment of the present invention has been described above, but the present invention is not limited to this. For example, in the above-described embodiment, only one of the first mixed layer and the second mixed layer is provided, but both the first mixed layer and the second mixed layer may be provided. Thereby, the reliability with respect to a heat | fever and mechanical stress can further be improved.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 5 to be referred to is a partially broken perspective view of an active matrix display (organic EL display) according to the fifth embodiment.

  As shown in FIG. 5, an active matrix display (hereinafter simply referred to as “display”) 50 includes a plastic substrate 51, a plurality of pixel electrodes 58 arranged in a matrix on the plastic substrate 51, and pixel electrodes 58. A plurality of organic TFT driving circuits 52 connected in a array on a plastic substrate 51, an organic EL layer 53, a transparent electrode 54, and a protective film 55 sequentially stacked on the pixel electrode 58 and the organic TFT driving circuit 52, A plurality of source electrode lines 56 and gate electrode lines 57 that connect each organic TFT drive circuit 52 and a control circuit (not shown) are provided. Here, the organic EL layer 53 is configured by laminating layers such as an electron transport layer, a light emitting layer, and a hole transport layer. In the display 50, each organic TFT drive circuit 52 is provided with the organic TFT according to any of the first to fourth embodiments described above as a pixel switching element. Thus, since the display 50 includes a plurality of organic TFTs according to any of the first to fourth embodiments described above as pixel switching elements, the reliability with respect to heat and mechanical stress can be improved. Can do.

  The display according to the embodiment of the present invention has been described above, but the present invention is not limited to this. For example, in the above-described embodiment, the display using the organic EL has been described. However, the display may include another display element such as a liquid crystal display element.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 6 to be referred to is a perspective view of the wireless identification tag according to the sixth embodiment.

  As shown in FIG. 6, the wireless identification tag 60 includes a film-like plastic substrate 61, an antenna unit 62 and an integrated circuit unit 63 provided on the plastic substrate 61. The integrated circuit unit 63 is provided with the organic TFT according to any of the first to fourth embodiments described above. Thereby, the reliability with respect to a heat | fever and mechanical stress can be improved. The wireless identification tag 60 may further include a protective film on the surface. Further, the wireless identification tag 60 can be attached to a confectionery bag or a product having a curved surface shape such as a drink can by giving an adhesive effect to the back surface.

  The wireless identification tag according to the embodiment of the present invention has been described above, but the present invention is not limited to this. For example, the arrangement and configuration of the antenna unit and the integrated circuit unit can be arbitrarily set. It is also possible to incorporate an ethics circuit section.

  Examples of the present invention will be described below. In addition, this invention is not limited to this Example.

(Examples 1-3)
First, Examples 1 to 3, which are examples of the first embodiment described above, will be described with reference to FIG. The materials used are a plastic substrate 1 as a plastic substrate having a thickness of 1.0 mm, an organic semiconductor material constituting the semiconductor layer 5, poly-3-hexylthiophene, and an organic insulating material constituting the gate insulating layer 3. In the case of Example 1, polyvinylphenol, in the case of Example 2, cyanoethyl pullulan, in the case of Example 3, polyvinyl alcohol, chloroform (I / O = 0.21) as a solvent for forming a semiconductor layer, insulating layer formation As the solvent for the film (solvent for forming the gate insulating layer), in the case of Example 1, 2-acetoxy-1-methoxypropane (I / O = 0.67), and in the case of Example 2, N-methyl-2- Pyrrolidinone (I / O = 1.45) was used, and in the case of Example 3, ethanol (I / O = 2.5) was used.

  Next, the manufacturing method of organic TFT of Examples 1-3 is demonstrated. First, an organic material constituting each of the semiconductor layer and the insulating layer is dissolved in the solvent for forming the semiconductor layer and the solvent for forming the insulating layer, and a solution for forming the semiconductor layer and a solution for forming the insulating layer are obtained. Prepared. Then, the solution for forming the semiconductor layer and the solution for forming the insulating layer are passed through a filter for removing impurities (SWINNEX manufactured by MILLIPORE), and then the solution using a defoamer (VMX-250SWINNEX manufactured by EME) The foam inside was removed. In addition, the density | concentration of the organic-semiconductor material in the solution for semiconductor layer film-forming was 1 wt% in any case of Examples 1-3. Moreover, the density | concentration of the organic insulating material in the solution for insulating layer film-forming was 15 wt% in any case of Examples 1-3.

Next, an Au paste was printed on a plastic substrate 1 using a screen plate patterned so as to obtain a desired shape, and then dried to form a gate electrode 2 made of Au having a thickness of 100 nm. Then, each of the insulating layer forming solutions is applied onto the plastic substrate 1 and the gate electrode 2 by a spin coating method, heated at 100 ° C. for 120 minutes, and dried to have a thickness of 1 μm. 3 was formed. Subsequently, the coating amount of each semiconductor layer deposition solution on the gate insulating layer 3 is adjusted so that the total thickness of the gate insulating layer 3, the first mixed layer 4 and the semiconductor layer 5 is 1.5 μm. Then, the first mixed layer 4 and the semiconductor layer 5 were formed by applying by a spin coating method, heating at 100 ° C. for 120 minutes, and drying. The thicknesses of the gate insulating layer 3 / first mixed layer 4 / semiconductor layer 5 are as follows: Example 1: 950 nm / 100 nm / 450 nm, Example 2: 975 nm / 50 nm / 475 nm, Example 3: 995 nm / 10 nm / It was 495 nm. Thereafter, a source electrode 6 and a drain electrode 7 made of Au having a thickness of 100 nm were formed on the semiconductor layer 5 by a method similar to the method for forming the gate electrode 2. Table 1 shows values of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} of Examples 1 to 3 and the thickness of the first mixed layer.

(Comparative example)
As a comparative example, polyvinyl alcohol is used as the organic insulating material constituting the gate insulating layer 3, and water (I / O = ∞) is used as the solvent for forming the insulating layer. Other conditions are the same as in Examples 1 to 3. A TFT was manufactured.

(Carrier mobility)
For Examples 1-3 and Comparative Examples were measured V _gs -I _ds curve was calculated carrier mobility. V _gs is a voltage value between the gate electrode and the source electrode, and I _ds is a current value flowing between the drain electrode and the source electrode. The results are shown in Table 1. As shown in Table 1, Examples 1 and 2 showed higher carrier mobility than the comparative example. This is because the semiconductor layer film forming solvent and the insulating layer film forming solvent used in the manufacture of Examples 1 and 2 have some solubility with respect to each other. It is considered that the carrier mobility was improved by removing the solvent while dissolving impurities such as oxygen and water at the interface when forming the film 5.

(Reliability against bending stress)
About Examples 1-3 and the comparative example, the reliability with respect to a bending stress was evaluated. The sample used for the evaluation was a polyethylene plastic substrate (70 mm × 70 mm) having a thickness of 1.0 mm, and each of the organic TFTs of Examples 1 to 3 and Comparative Example was formed into an 8 × 8 matrix by the manufacturing method described above. An organic TFT sheet arranged in a shape was used. This sample was provided with a probing pad portion so that each organic TFT could contact each electrode from the upper surface of the plastic substrate. In each organic TFT, the distance (channel length) between the source electrode and the drain electrode was set to 100 μm.

  In the evaluation method, as shown in FIG. 7, first, the operation of displacing the central portion of the organic TFT sheet 70 up and down by 5 mm was repeated 10 cycles as one cycle (FIGS. 7A to 7D). Thereafter, the operation of each organic TFT was confirmed, and a case where any one of a total of 64 organic TFTs did not operate was regarded as defective. This evaluation test was conducted for 20 samples for each of Examples 1 to 3 and Comparative Example, and the defect rate was calculated. Then, the case where the defect rate became 5% or less was judged as ◯, and the case where it exceeded 5% was judged as x. The results are shown in Table 1.

  As shown in Table 1, in the comparative example, the defect rate was 40% (“×”). In Examples 1 to 3, the first mixed layer 4 adhered the gate insulating layer 3 and the semiconductor layer 5 together. As a result, the defect rate was 5% or less (“◯”), and the reliability against bending stress was improved.

  In addition, about the Example of 2nd Embodiment mentioned above, since the arrangement | positioning of each layer differs only from the Example of 1st Embodiment, it can manufacture by the method similar to the manufacturing method of the said Examples 1-3. Therefore, the description is omitted.

Example 4
Next, Example 4 which is an example of the above-described third embodiment will be described with reference to FIG. The organic TFT of Example 4 was manufactured using the same manufacturing method and the same constituent materials as those of Example 2 except that PET having a thickness of 1.0 mm was used as the plastic substrate 1. In the organic TFT of Example 4, a part of PET that is a constituent material of the plastic substrate 1 is formed at the stage of applying the insulating layer film forming solution on the plastic substrate 1 and the gate electrode 2 by the spin coating method. A second mixed layer 31 (thickness: 0.1 μm) is formed between the plastic substrate 1 and the gate insulating layer 3 by being dissolved in N-methyl-2-pyrrolidinone, which is a solvent for forming the insulating layer. Moreover, since the organic TFT of Example 4 uses a solvent having a value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} of 0.1 to 0.3, the organic TFT of Example 2 is used. Like the TFT, it has a first mixed layer 4 (see FIG. 1). Thereby, since the organic TFT of Example 4 has the 1st mixed layer 4 and the 2nd mixed layer 31, it can further improve the reliability with respect to a heat | fever and mechanical stress.

In the method of manufacturing the organic TFT of Example 4, a solvent having a value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} of 0.1 to 0.3 was used. The manufacturing method of the organic TFT according to the third embodiment is not limited to this, and a solvent in which the value of (I / O) _{semiconductor layer} / (I / O) _{insulating layer} is less than 0.1 may be selected. A solvent having the above value exceeding 0.3 may be selected. In addition, since the example of the fourth embodiment described above is different from the example of the third embodiment only in the arrangement of each layer, it can be manufactured by the same method as the manufacturing method of Example 4, Description is omitted.

  As mentioned above, although the Example of the organic TFT of this invention was described, this invention is not limited to the said Example. For example, in the above embodiment, the spin coating method is used when the semiconductor layer film forming solution and the insulating layer film forming solution are applied onto the substrate. However, other methods such as an ink jet printing method, a dip coating method, and a casting method are used. You may apply | coat by the apply | coating method. In the above embodiment, Au is used as a constituent material of the source electrode, the drain electrode, and the gate electrode. However, the electrode material is not limited to this, and the organic material depends on the relationship between the semiconductor layer and the insulating layer to be used. Various conductor materials can be selected regardless of inorganic.

1 is a cross-sectional view of an organic TFT according to a first embodiment of the present invention. It is sectional drawing of the organic TFT which concerns on 2nd Embodiment of this invention. It is sectional drawing of the organic TFT which concerns on 3rd Embodiment of this invention. It is sectional drawing of the organic TFT which concerns on 4th Embodiment of this invention. It is a partially broken perspective view of an active matrix type display concerning a 5th embodiment of the present invention. It is a perspective view of the radio | wireless identification tag which concerns on 6th Embodiment of this invention. It is sectional drawing explaining the evaluation method for evaluating the reliability with respect to a bending stress about the Example of this invention.

Explanation of symbols

1, 51, 61 Plastic substrate 2 Gate electrode 3 Gate insulating layer (insulating layer)
4 First mixed layer 5 Semiconductor layer 6 Source electrode 7 Drain electrode 10, 20, 30, 40 Organic TFT (organic thin film transistor)
31, 41 Second mixed layer 50 Active matrix type display 60 Wireless identification tag 63 Integrated circuit section

Claims (9)

An organic thin film transistor including a semiconductor layer made of an organic semiconductor material and an insulating layer made of an organic insulating material,
A first mixed layer comprising the organic semiconductor material and the organic insulating material;
The organic thin film transistor, wherein the semiconductor layer and the insulating layer are stacked via the first mixed layer.   The organic thin film transistor according to claim 1, wherein a thickness of the first mixed layer is 100 nm or less. An organic thin film transistor including a plastic substrate, a semiconductor layer made of an organic semiconductor material, and an insulating layer made of an organic insulating material,
A second mixed layer comprising the material constituting the plastic substrate and the organic semiconductor material or the organic insulating material;
The organic thin film transistor, wherein the plastic substrate and the semiconductor layer or the insulating layer are laminated via the second mixed layer.   The organic thin film transistor according to claim 3, wherein the thickness of the second mixed layer is 10 nm or more. An organic semiconductor material and an organic insulating material are respectively dissolved in a semiconductor layer film forming solvent and an insulating layer film forming solvent to prepare a semiconductor layer film forming solution and an insulating layer film forming solution. A method for producing an organic thin film transistor in which a solution for forming an insulating layer and a solution for forming an insulating layer are applied on a substrate and a semiconductor layer and an insulating layer are laminated,
The inorganic / organic ratio in the organic conceptual diagram of the solvent for forming a semiconductor layer is defined as (I / O) _{semiconductor layer,} and the inorganic / organic ratio in the organic conceptual diagram of the solvent for forming an insulating layer is defined as (I / O). O) in the case of the _{insulating layer,} (I / O) _{semiconductor layer} / (I / O) method for producing an organic thin film transistor which the value of _{the insulating layer} is characterized in that from 0.1 to 0.3.   The at least one of a spin coating method, an ink jet printing method, a dip coating method, and a casting method is used when the semiconductor layer film forming solution and the insulating layer film forming solution are applied onto the substrate. The manufacturing method of the organic thin-film transistor of description.   The method for producing an organic thin film transistor according to claim 5 or 6, wherein the solution for forming a semiconductor layer and the solution for forming an insulating layer are passed through a filter for removing impurities and then applied onto the substrate.   An active matrix display comprising a plurality of organic thin film transistors according to any one of claims 1 to 4 as pixel switching elements. A wireless identification tag including an integrated circuit unit,
A wireless identification tag, wherein the integrated circuit portion is provided with the organic thin film transistor according to any one of claims 1 to 4.

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