JP2008244363A - Thin film transistor, electronic circuit, display device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor that prevents not only the metal ion diffusion from a gate insulating layer to an organic semiconductor layer but also the deterioration of the characteristics, a high-reliability electronic circuit, a display device and electronic device. <P>SOLUTION: The thin film transistor 1 mounted on a substrate 10 includes a source electrode 20a and drain electrode 20b separately disposed each other, an organic semiconductor layer 30 disposed between the source electrode 20a and drain electrode 20b, a gate insulating layer 40 disposed between the organic semiconductor layer 30 and gate electrode 50. Furthermore, the gate insulating layer 40 includes an ion trapping substance 41 to trap a metal ion, and this ion trapping substance 41 is, preferably, diffused in a matrix 42 constituted of an insulating material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film transistor, an electronic circuit, a display device, and an electronic apparatus.

In recent years, development of a thin film transistor using an organic material (organic semiconductor material) that exhibits semiconducting electrical conduction has been promoted. This thin film transistor has advantages such as being suitable for reduction in thickness and weight, flexibility, and low material cost, and is expected as a switching element for flexible displays and the like.
As this thin film transistor, a source electrode and a drain electrode are formed on a substrate, and an organic semiconductor layer, a gate insulating layer, and a gate electrode are laminated on the electrodes in this order.

  Incidentally, an off-current is one of the indexes for evaluating the characteristics of a thin film transistor. In the thin film transistor, the smaller the off current, the better the switching characteristics and the lower the power consumption. Therefore, the off current should be as small as possible. However, it has been the actual situation that the thin film transistor having the conventional configuration cannot be said to have a sufficiently small off-state current.

  Here, as one of the causes for increasing the off-state current of the thin film transistor, metal ions existing in the gate insulating layer diffuse into the organic semiconductor layer, and the metal ions cause a gap between the source electrode and the drain electrode or the gate electrode and the source. A leakage current is generated between the electrodes. That is, the gate insulating layer is mixed with alkali metal ions or the like contained in the catalyst or solvent used when synthesizing the organic insulating material that is the constituent material, and the alkali metal ions or the like mixed as impurities are included. Diffusion into the organic semiconductor layer results in an increase in the off current of the thin film transistor.

For example, as shown in Patent Document 1, when the gate electrode is made of a conductive material containing a metal such as Ag, the metal contained in the gate electrode is ionized to generate metal ions. Ions diffuse into the gate insulating layer. Further, the metal ions further diffuse into the organic semiconductor layer, which also increases the off current of the thin film transistor.
Thus, the metal ions diffused from the gate insulating layer to the organic semiconductor layer are the main factors that cause an increase in off current of the thin film transistor, that is, a decrease in characteristics of the thin film transistor.

JP 2005-150640 A

  An object of the present invention is to provide a thin film transistor, a highly reliable electronic circuit, a display device, and an electronic device that can prevent metal ions from diffusing from a gate insulating layer to an organic semiconductor layer and suppress deterioration in characteristics. It is in.

Such an object is achieved by the present invention described below.
The thin film transistor according to the present invention includes a gate electrode,
An organic semiconductor layer;
A gate insulating layer located between the gate electrode and the organic semiconductor layer;
A source electrode and a drain electrode that move carriers through the organic semiconductor layer, and
The gate insulating layer includes an ion trapping material capable of trapping metal ions.
Accordingly, diffusion of metal ions from the gate insulating layer to the organic semiconductor layer can be prevented, and the off current of the thin film transistor can be reduced, that is, the deterioration of the characteristics of the thin film transistor can be suppressed.

In the thin film transistor of the present invention, it is preferable that the ion trapping substance is capable of trapping alkali metal ions contained in the gate insulating layer.
Thereby, alkali metal ions mixed as impurities in the gate insulating layer can be reliably trapped by the ion trapping substance, and diffusion of the alkali metal ions to the organic semiconductor layer can be reliably prevented.

In the thin film transistor of the present invention, the gate electrode contains a metal element,
It is preferable that the ion trapping substance is capable of trapping metal ions derived from the metal element.
Thereby, the metal ion derived from the gate electrode diffused in the gate insulating layer can be reliably trapped by the ion trapping substance, and the diffusion of the metal ion to the organic semiconductor layer can be surely prevented.

In the thin film transistor of the present invention, it is preferable that the ion trapping substance has a ring structure, and the type and size of the ring of the ring structure are selected according to the type of metal ion and / or the difference in ion diameter. .
Thus, the metal ion to be captured can be reliably captured by adopting a configuration in which the type of ring and the size of the ring are selected according to the type and / or ion diameter of the metal ion.

In the thin film transistor of the present invention, it is preferable that the cyclic structure includes at least one heteroatom selected from an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.
Such a cyclic structure is preferable because it has a very high ion trapping ability. Further, there is an advantage that the size of the ring (inner space) and the flexibility of the ring can be easily adjusted, and the synthesis of such a cyclic structure can be performed relatively easily.

In the thin film transistor of the present invention, it is preferable that the ring structure has 6 or more carbon atoms and two or more at least one hetero atom in the ring.
Such a cyclic structure is preferable because it has a very high ion trapping ability. Further, there is an advantage that the size of the ring (inner space) and the flexibility of the ring can be easily adjusted, and the synthesis of such a cyclic structure can be performed relatively easily.

In the thin film transistor of the present invention, it is preferable that the gate insulating layer is formed by dispersing the ion trapping substance in a base material made of an insulating material.
As a result, the metal ions can be captured by the ion trapping substance, and since the base material is interposed between the adjacent ion trapping parts, the delivery of the metal ions between the adjacent ion trapping substances is surely prevented. be able to.

In the thin film transistor of the present invention, the insulating material is preferably an insulating polymer.
A gate insulating layer made of an insulating polymer is preferable because it is easy to form and can improve adhesion to the organic semiconductor layer.
In the thin film transistor of the present invention, the insulating polymer preferably contains a monomer having 1 or less lone pair.
Thereby, transmission (diffusion) of metal ions by the insulating polymer can be suitably prevented or suppressed. Therefore, it is possible to reliably prevent the transfer of metal ions via the base material between adjacent ion trapping substances. That is, the trapped metal ions can be reliably kept in the ion trapping substance.

In the thin film transistor of the present invention, it is preferable that the ion trapping substance is unevenly distributed in the vicinity of an interface between the base material and the organic semiconductor layer.
Thus, both the metal ions diffused from the gate electrode and the alkali metal ions mixed as impurities in the gate insulating layer can be captured by the gate insulating layer without reaching the organic semiconductor layer.

In the thin film transistor of the present invention, it is preferable that the ion trapping substance is unevenly distributed in the vicinity of the interface between the base material and the gate electrode.
Thereby, the metal ion diffused from the gate electrode can be captured by the ion trapping material contained in the gate insulating layer.
In the thin film transistor of the present invention, the content of the ion trapping substance in the gate insulating layer is preferably 1 to 40 wt%.
Thereby, since it can prevent reliably that a metal ion will be delivered between adjacent ion trapping substances, a metal ion can be reliably trapped with an ion trapping substance. As a result, diffusion of metal ions from the gate insulating layer to the organic semiconductor layer can be more reliably prevented.

An electronic circuit according to the present invention includes the thin film transistor of the present invention.
Thereby, a highly reliable electronic circuit is obtained.
A display device according to the present invention includes the electronic circuit according to the present invention.
Thereby, a highly reliable display device is obtained.
An electronic apparatus according to the present invention includes the display device of the present invention.
As a result, a highly reliable electronic device can be obtained.

Hereinafter, a thin film transistor, an electronic circuit, a display device, and an electronic apparatus of the present invention will be described in detail based on the preferred embodiments shown in the drawings.
<Thin film transistor>
<< First Embodiment >>
First, a first embodiment of the thin film transistor of the present invention will be described.

FIG. 1 is a schematic cross-sectional view showing a first embodiment of the thin film transistor of the present invention, and FIG. 2 is a view (longitudinal cross-sectional view) for explaining a manufacturing method of the thin film transistor shown in FIG.
The thin film transistor 1 shown in FIG. 1 includes a gate electrode 50, a source electrode 20a and a drain electrode 20b provided separately from each other, an organic semiconductor layer 30 provided in contact with the source electrode 20a and the drain electrode 20b, A structure having a gate insulating layer 40 that is located between the semiconductor layer 30 and the gate electrode 50 and insulates the source electrode 20 a and the drain electrode 20 b from the gate electrode 50 and is mounted on the substrate 10. ing.
Such a thin film transistor 1 is a thin film transistor having a structure in which the source electrode 20a and the drain electrode 20b are provided on the substrate 10 side of the gate electrode 50 via the gate insulating layer 40, that is, a thin film transistor having a top gate structure.

  Hereinafter, each part which comprises the thin-film transistor 1 is demonstrated sequentially.

The substrate 10 supports each layer (each part) constituting the thin film transistor 1.
Examples of the substrate 10 include a plastic substrate (resin) made of a glass substrate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), aromatic polyester (liquid crystal polymer) polyimide (PI), and the like. Substrate), quartz substrate, silicon substrate, metal substrate, gallium arsenide substrate, and the like.

In the case where flexibility is given to the thin film transistor 1, a plastic substrate or a thin (relatively small film thickness) metal substrate is selected as the substrate 10.
On the substrate 10, a source electrode 20a and a drain electrode 20b are provided.
Examples of the constituent material of the source electrode 20a and the drain electrode 20b include metal materials such as Pd, Pt, Au, W, Ta, Mo, Al, Cr, Ti, Cu, and alloys containing these, and the channel region It is preferable to select appropriately according to the carrier to move.

  For example, in the case of a p-channel thin film transistor in which holes move in the channel region, it is preferable to use Pd, Pt, Au, Ni, Cu, or an alloy containing these metals having a relatively large work function. Furthermore, a noble metal having a small ionization tendency is preferably used. Specifically, a metal material such as Au, Pd, Pt, or an alloy containing these, and oxides thereof can be used. By using such a metal material, diffusion of metal ions from the source electrode 20a and the drain electrode 20b to the organic semiconductor layer 30 can be reliably prevented.

Moreover, the source electrode 20a and the drain electrode 20b can also be comprised with an electroconductive organic material.
Examples of the conductive organic material include a thiophene skeleton such as an ethylenedioxythiophene skeleton such as poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS), a paraphenylene skeleton, and a paraphenylene vinylene skeleton. Examples thereof include polymer compounds having a skeleton such as a phenylene skeleton, a pyrrole skeleton, a styrene skeleton, and an acetylene skeleton, and one or more of them can be used in combination.

The average thickness of the source electrode 20a and the drain electrode 20b is not particularly limited, but is preferably about 10 to 2000 nm, and more preferably about 50 to 1000 nm.
An organic semiconductor layer 30 is provided on the substrate 10 so as to cover the source electrode 20a and the drain electrode 20b.

The organic semiconductor layer 30 is composed mainly of an organic semiconductor material (an organic material that exhibits semiconducting electrical conduction).
Examples of such organic semiconductor materials include fluorene-bithiophene copolymer (F8T2) or derivatives thereof, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polythiophene, poly (p-phenylenevinylene), and pyreneformaldehyde. Resin, high molecular organic semiconductor materials such as ethylcarbazole formaldehyde resin, naphthalene, anthracene, tetracene, pentacene, hexacene, phthalocyanine, perylene, hydrazone, triphenylmethane, diphenylmethane, stilbene, arylvinyl, pyrazoline, triphenylamine, Examples include low-molecular organic semiconductor materials such as triarylamine or derivatives thereof, and one or more of these can be used in combination. That is, in particular, to use an organic semiconductor material of a polymer as a main material preferable. The organic semiconductor layer 30 composed mainly of a polymer organic semiconductor material can be reduced in thickness and weight, and has excellent flexibility. Therefore, the organic semiconductor layer 30 is applied to a thin film transistor used as a switching element of a flexible display. Suitable for

The average thickness of the organic semiconductor layer 30 is preferably about 0.1 to 1000 nm, more preferably about 1 to 500 nm, and further preferably about 1 to 100 nm.
The organic semiconductor layer 30 may not be provided so as to cover the source electrode 20a and the drain electrode 20b, and is provided at least in a region (channel region 31) between the source electrode 20a and the drain electrode 20b. Just do it.

  In FIG. 1, the organic semiconductor layer 30 is provided in contact with the source electrode 20a and the drain electrode 20b. However, the thin film transistor of the present invention has a carrier between the source electrode 20a and the drain electrode 20b via the organic semiconductor layer. For example, a thin insulating film such as a SAM film may be formed between the organic semiconductor layer 30 and the source electrode 20a or between the organic semiconductor layer 30 and the drain electrode 20b.

On the organic semiconductor layer 30, a gate insulating layer 40 containing an ion trapping material is provided.
The gate insulating layer 40 of this embodiment is configured by dispersing an ion trapping substance 41 in a matrix (base material) 42 made of an insulating material. The gate insulating layer 40 only needs to contain the ion trapping material 41, but the ion trapping material 41 can be captured by the ion trapping material 41 by adopting a configuration in which the ion trapping material 41 is dispersed in the matrix 42. Since the matrix 42 is interposed between the ion trapping portions 41 to be performed, it is possible to reliably prevent the transfer of metal ions between the adjacent ion trapping materials 41.

The ion trapping substance 41 is a substance having a function of trapping metal ions.
Such an ion trapping material 41 is included in the gate insulating layer 40, whereby the metal ions mixed as impurities in the gate insulating layer 40 and the metal ions diffused from the gate electrode 50 are converted into the ion trapping material. 41 can be captured. Thereby, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 is prevented. As a result, migration occurs due to the diffusion of metal ions in the organic semiconductor layer 30, leakage current generated between the source electrode and the drain electrode caused by this migration, and the gate electrode and the drain electrode (or source electrode) Leak current generated between the two can be suppressed or prevented. Thus, the off-state current in the thin film transistor 1 can be suppressed, that is, the deterioration of the characteristics of the thin film transistor 1 can be suppressed.

  The gate insulating layer 40 in which the ion trapping substance 41 is dispersed in the matrix 42 is made of a liquid material containing the ion trapping substance 41 and an insulating material (for example, an insulating polymer) as will be described later. It can be formed by a liquid phase process in which a liquid film is formed and the liquid film is dried. Therefore, a large-scale device for high temperature and high vacuum is not required, and the thin film transistor 1 can be easily formed with a simple device.

The ion trapping agent 41, for example, those having a cyclic structure (ionophore) capable of capturing the metal ions in the interior space, SO ₃ is electrically coupled to the metal ion ^- group, CO ₂ ^- group, PO ₄ H ^- group And those having an ionic group such as an NH ₃ ⁺ group, and those having a cyclic structure are particularly preferred. By using a substance having a cyclic structure as the ion trapping substance, the metal ions can be trapped and held more reliably without releasing other ions such as hydrogen ions when trapping the metal ions.

  Moreover, as this cyclic structure (ionophore), for example, a structure containing at least one hetero atom (heteroatom) such as an oxygen atom, a nitrogen atom, a sulfur atom and a phosphorus atom (that is, a methylene group is bonded to an oxygen atom) Atoms, nitrogen atoms, sulfur atoms, phosphorus atoms and other heteroatoms), derivatives thereof, those composed only of methylene groups (hydrocarbon rings), and the like. Those bonded by an atom, nitrogen atom, sulfur atom and phosphorus atom and derivatives thereof are preferred. Such a cyclic structure is preferable because it has a very high ion trapping ability. Further, there is an advantage that the size of the ring (inner space) and the flexibility of the ring can be easily adjusted, and the synthesis of such a cyclic structure can be performed relatively easily.

In the present specification, a hetero atom refers to an atom constituting a ring of a cyclic structure (heterocyclic compound) excluding a carbon atom. For example, as described above, an oxygen atom, a nitrogen atom , Sulfur atom and phosphorus atom.
As such a cyclic structure (ionophore) containing a heteroatom, for example, it has 6 or more carbon atoms and 2 or more heteroatoms in the ring constituting the cyclic structure. Are listed.

  Specifically, a crown ether type represented by the following chemical formula 1, a propylene glycol type represented by the following chemical formula 2, an azacrown type represented by the following chemical formula 3, a thioether type represented by the chemical formula 4 below, And those derived from the nature represented by the following chemical formula 5 and those having a plurality of crown rings as represented by the chemical formula 6 below.

In addition, what connected the some crown ring represented by said Chemical formula 6 includes what connected the some crown ring directly, and what connected the some crown ring via the connection structure.
Here, for example, if the number of n and m in each general formula increases, the annular structure (size of the inner space) increases, and the diameter of metal ions that can be captured tends to increase. Moreover, when an aryl group or an unsaturated bond is included in the cyclic structure, the flexibility of the cyclic structure tends to decrease.

  Therefore, when the ion-trapping substance 41 having these cyclic structures is used, ions that are expected to be present in the gate insulating layer, that is, ions that are expected to be mixed into the gate insulating layer 40 as impurities, and the gate It is preferable to select the type of ring and the size of the ring (the number of n and m) according to the type and / or ion diameter of the metal ion expected to diffuse from the electrode 50 to the gate insulating layer 40. In this way, by selecting the type of ring and the size of the ring (the number of n and m) according to the type and / or ion diameter of the metal ion, the metal ion to be captured can be reliably captured. can do.

Specifically, it is preferable to select an ion trapping substance having a cyclic structure in consideration of the following points.
I: In the case where alkali metal ions such as Li ⁺ , Na ⁺ , K ^{+ and the} like are expected to be mixed into the gate insulating layer 40, the ion trapping material 41 having a cyclic structure capable of trapping alkali metal ions is selected.

Specifically, the ion diameters of alkali metal ions are larger in the order of Li ⁺ <Na ⁺ <K ⁺ , and are selectively captured by 12-membered, 15-membered, and 18-membered crown ether rings, respectively. . Therefore, when Li ⁺ , Na ⁺ and K ⁺ are expected to be mixed into the gate insulating layer 40, the above-described chemical formula 1 in which the number of n is 2, 3 and 4 respectively as an ion trapping material having a cyclic structure ( The one represented by a) is used.

  Further, the ion trapping substance represented by the chemical formula 1 (b), the ion trapping substance represented by the chemical formula 1 (c), the ion trapping substance represented by the chemical formula 2 and the ion trapping represented by the chemical formula 3 Each of the substance and the ion trapping substance represented by Chemical Formula 6 has a ring structure similar to a crown ether ring or a crown ether ring, and all of them can trap alkali metal ions. Among these, the ion-trapping substance represented by the chemical formula 6 (b) has a structure in which the crown ring is doubled (a structure in which two crown rings are directly connected), so that an alkali metal ion Can be confined by a double crown ring, and alkali metal ions can be firmly captured.

Further, the ion-trapping substances represented by the chemical formula 5 (naturally-occurring enniatin-B (the chemical formula 5 (a)) and nonactin (the chemical formula 5 (b))) are complexed with Na ⁺ and K ⁺ in the cell membrane. It is related to formation and traps these alkali metal ions efficiently.
Therefore, the ion trapping material having such a ring structure can be suitably used as the ion trapping material 41 when alkali metal ions are expected to be mixed into the gate insulating layer 40.
By using the ion trapping material having the ring structure as described above, alkali metal ions mixed as impurities in the gate insulating layer 40 can be reliably trapped by the ion trapping material 41, and the organic semiconductor of this alkali metal ion Diffusion to the layer 30 can be reliably prevented.

II: When the gate electrode 50 is composed of a conductive material containing a metal element, and this metal ion is expected to diffuse into the gate insulating layer 40, an annular structure that can capture the metal ion derived from this gate electrode Is selected.
Since the metal ion constituting the conductive material generally has a larger ion diameter than the alkali metal ion, a ring whose target is an ion having a larger diameter than an ion trapping substance having a cyclic structure capable of trapping the alkali metal ion. It is easy to be trapped by the ion trapping substance having a structure.

Specifically, since the ion trapping substance having a cyclic structure (of the azacrown type) represented by Chemical Formula 3 can capture a relatively large metal ion by selecting the number of n, The gate electrode 50 is suitably used as an ion trapping material having a cyclic structure used when a metal element is contained.
In addition, an ion trapping substance having a (sulfide-based) cyclic structure represented by the above chemical formula 4 in which the number of n is 4 selectively captures silver ions. Therefore, when the gate electrode 50 contains silver, it can be suitably used as an ion trapping substance having a ring structure.

  In addition, the ion trapping substance having a ring structure represented by the chemical formula 6 (a) is changed into a U-shape when irradiated with light, and two crown rings face each other. In this state, since ions can be sandwiched between two crown rings, ions larger than the ion diameter determined by the size of the crown ring can be captured. For this reason, the ion trapping substance provided with the cyclic structure represented by the chemical formula 6 (a) described above is an ion trapping substance when the gate electrode 50 contains a metal element by setting the two crown rings to face each other. 41 is preferably used.

By using the ion trapping material having the above-described ring structure, the metal ions derived from the gate electrode 50 diffused in the gate insulating layer 40 can be reliably trapped by the ion trapping material 41, and the organic ions of this metal ion Diffusion to the semiconductor layer 30 can be reliably prevented.
Moreover, when the ion capture | acquisition substance 41 is provided with a cyclic structure (ionophore), it is preferable to have a coordination structure coordinated to the metal ion further trapped in the cyclic structure. Coordination structure coordinates with metal ions trapped in the ring structure, so that the metal ions are capped and hold the metal ions trapped in the ring structure more reliably. Can do.

Moreover, a larger-sized space can be ensured by the annular structure and the coordination structure. For this reason, a larger size metal ion can be captured by the ion capturing material 41 without increasing the size of the annular structure.
Specific examples of the ion trapping substance having such a coordination structure include the following chemical formulas 7 and 8. This is an example, and the oxygen atom contained in the coordination structure portion may be changed to an atom having another unshared electron pair such as a nitrogen atom or a phosphorus atom.

Moreover, the side chain may be introduce | transduced as needed to the ion trapping substance provided with the above cyclic structures. Thereby, various characteristics can be imparted to the ion-trapping substance having a ring structure. For example, when an alkyl group is introduced as a side chain, the solubility of an ion-trapping substance having a cyclic structure in a solvent can be controlled by changing the number of carbon atoms. For example, in the case of an ion-trapping substance having a (crown ether type) cyclic structure represented by the above chemical formula 1 (a), such a side chain is converted into nitrogen by changing at least one of oxygen to nitrogen. It can introduce | transduce by making it connect with at least 1 of the carbon between oxygen, etc., etc.
Further, as an ion trapping substance having a cyclic structure, as represented by the following chemical formula 9, a polymer of a derivative of the compound represented by the chemical formula 1 (a) (crown ether derivative), that is, a heavy compound having a cyclic structure. A coalescence or the like can also be used. Thereby, the following effects are obtained.

That is, when a relatively low molecular weight ion-trapping substance is present in the vicinity of the interface with the organic semiconductor layer 30, there is a possibility that metal ions are captured and diffused into the organic semiconductor layer 30. Metal ions diffused into the organic semiconductor layer 30 while being captured by the ion trapping substance may cause a leakage current in the organic semiconductor layer 30. On the other hand, since the polymer having a cyclic structure has a high molecular weight, it is difficult to move in the gate insulating layer 40 and reliably prevents diffusion into the organic semiconductor layer 30 while capturing metal ions. be able to. In the case of such a polymer, the ionic species captured by each monomer is substantially the same as the corresponding cyclic structure.
Further, the polymer represented by the chemical formula 9 has one thiophene group for one crown ether, but a polymer having two thiophene groups for one crown ether may be used. it can.

Further, the ion trapping substance having a cyclic structure may be a copolymer of the polymer represented by the chemical formula 9 and an insulating polymer described later. Also in this case, since the copolymer is a polymer similar to the polymer represented by the chemical formula 9, it is difficult to move in the gate insulating layer and diffuses to the organic semiconductor layer in a state of capturing ions. Can be surely prevented.
Moreover, as an ion capture | acquisition substance provided with cyclic structure, in addition to what is equipped with the cyclic structure (crown ring) as shown in the said Chemical formula 1-Chemical formula 9, for example, the cyclic compound (calixarene) represented by following Chemical formula 10 is shown. Can be used.

Among these, those in which n is 4, and R ¹ is a tert-butyl group have excellent scavenging ability for alkali metal ions, and ions when alkali metal ions are expected to be mixed into the gate insulating layer 40 It is suitably used as a capture substance.
In addition, as the ion trapping substance having a cyclic structure, a cyclam (1,4,8,11-tetrazacyclote-tradecane), cyclodextrin, or the like can be used.

  In addition, the ion capture | acquisition substance 41 can be used 1 type or in combination of 2 or more types. For example, when it is expected that alkali metal ions are mixed into the gate insulating layer 40 as impurities and metal ions are diffused from the gate electrode 50, an ion trapping substance capable of trapping alkali metal ions It is preferable to use in combination with an ion-trapping substance that can capture metal ions derived from the gate electrode. Thereby, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 can be prevented more reliably, and leakage current between the source electrode and the drain electrode and between the gate electrode and the drain electrode can be prevented. Can be more reliably suppressed.

In this case, the ratio of the ion trapping substance capable of trapping alkali metal ions and the ion trapping substance capable of trapping metal ions derived from the gate electrode is preferably about 10: 1 to 1:20. More preferably, it is about ˜1: 5. Thereby, both alkali metal ions and metal ions derived from the gate electrode can be efficiently captured.
Further, the content (content ratio) of the ion trapping substance 41 in the gate insulating layer 40 is preferably about 1 to 40 wt%, and more preferably about 20 to 30 wt%. By setting the content of the ion trapping material 41 within the above range, it is possible to reliably prevent the metal ions from being transferred between the adjacent ion trapping materials 41. It can be captured more reliably. As a result, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 can be more reliably prevented.

The insulating material constitutes the matrix 42 of the gate insulating layer 40.
The insulating material is not particularly limited as long as it has insulating properties, and may be either an inorganic insulating material or an organic insulating material. A system insulating material is preferably used.
The organic insulating material is not particularly limited, but is preferably a high molecular organic insulating material (insulating polymer). The gate insulating layer 40 made of such a material can be easily formed and can improve adhesion to the organic semiconductor layer 30.

  Examples of such insulating polymers include olefin resins such as polyethylene, polypropylene, polyisobutylene, and polybutene, polystyrene, polyimide, polyamideimide, polyvinylphenylene, polycarbonate (PC), and polymethyl methacrylate (PMMA). Examples include acrylic resins, fluorine resins such as polytetrafluoroethylene (PTFE), phenol resins such as polyvinylphenol (PVP) or novolac resin, and one or more of these are combined. Can be used.

  Among these insulating polymers, it is preferable to select a monomer component that constitutes the insulating polymer mainly having an unshared electron pair of 1 or less, and selecting a monomer component having no unshared electron pair. preferable. By selecting such an insulating polymer having a low polarity, transmission (diffusion) of metal ions by the insulating polymer can be suitably prevented or suppressed. Therefore, it is possible to reliably prevent the transfer of metal ions through the matrix 42 between the adjacent ion trapping substances 41. That is, the trapped metal ions can be reliably retained in the ion trapping material 41.

  Specifically, as an insulating polymer composed of a monomer component having a number of unshared electron pairs of 1 or less, that is, an insulating polymer containing a monomer having 1 or less unshared electron pairs, for example, polyethylene, polypropylene, poly Examples include polyolefins composed of chain aliphatic hydrocarbons such as isobutylene and polybutene, polystyrene, and the like, and polyolefins having cyclic aliphatic hydrocarbons (hereinafter abbreviated as “cycloolefin-containing polymer”). It is done.

  Among these, the cycloolefin-containing polymer is a polymer having excellent properties such as high pressure resistance, low hygroscopicity, high heat resistance, high density, and solvent selectivity, a rigid main chain, and a high glass transition temperature. Thus, the function of preventing diffusion of metal ions can be imparted to the matrix 42 itself composed of the cycloolefin-containing polymer. Therefore, when a cycloolefin-containing polymer is used, diffusion of metal ions can be reliably prevented by the matrix 42, and even if metal ions diffuse in the matrix 42, the metal ions diffused by the ion trapping substance 41 can be reliably prevented. Can be captured. As a result, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 can be more reliably prevented or suppressed.

  The cyclic aliphatic hydrocarbon contained in such a cycloolefin-containing polymer is preferably one having 3 to 20 carbon atoms, more preferably 4 to 15 carbon atoms. Specifically, for example, cyclopentane, cyclohexane, cycloheptane, cyclodecane, norbornene, dicyclopentadiene, tetracyclododecene, and the like can be used, and one or more of these can be used in combination. . Among these, those containing norbornene are preferable. Since norbornene has a bulky molecular structure, polyolefin can be easily converted into an amorphous structure due to steric hindrance. As a result, a uniform gate insulating layer 40 can be obtained.

When the molecular weight of the cycloolefin-containing polymer is measured by gel permeation chromatography (GPC), the weight average molecular weight (Mw) in terms of polyisoprene is preferably 1 × 10 ^{4 to} 5 × 10 ^6. It is more preferable that it is * 10 < ⁴ > -1 * 10 < ⁶ >. By setting the molecular weight within such a range, the high-density gate insulating layer 40 can be formed, and thus diffusion of metal ions from the gate insulating layer 40 can be prevented.
Examples of such cycloolefin-containing polymer include compounds represented by the following chemical formula 11.

  The average thickness of the gate insulating layer 40 is not particularly limited, but is preferably about 100 to 10000 nm, and more preferably about 200 to 1000 nm. By setting the thickness of the gate insulating layer 40 within the above range, the operating voltage of the thin film transistor 1 can be lowered while reliably insulating the source electrode 20a and the drain electrode 20b from the gate electrode 50.

A gate electrode 50 is provided at a predetermined position on the gate insulating layer 40, that is, a position corresponding to a region between the gate electrode 20a and the drain electrode 20b.
As a constituent material of the gate electrode 50, for example, a metal (inorganic) conductive material such as Cr, Al, Ta, Mo, Nb, Cu, Ag, In, Ni, Nd, Co or an alloy containing them. Can be used.

The average thickness of the gate electrode 50 is not particularly limited, but is preferably about 0.1 to 2000 nm, and more preferably about 1 to 1000 nm.
In such a thin film transistor 1, when a gate voltage is applied to the gate electrode 50 with a voltage applied between the source electrode 20a and the drain electrode 20b, a channel is formed near the interface between the organic semiconductor layer 30 and the gate insulating layer 40. As a result, carriers (holes) move through the channel region 31, whereby a current flows between the source electrode 20 a and the drain electrode 20 b through the organic semiconductor layer 30.

  That is, in the OFF state in which no voltage is applied to the gate electrode 50, even if a voltage is applied between the source electrode 20a and the drain electrode 20b, almost no carriers are present in the organic semiconductor layer 30; Only flows. On the other hand, in the ON state in which a voltage is applied to the gate electrode 50, charges are induced in the portion of the organic semiconductor layer 30 facing the gate insulating layer 40, and a channel (carrier flow path) is formed. When a voltage is applied between the source electrode 20 a and the drain electrode 20 b in this state, a current flows through the channel region 31.

In particular, in the thin film transistor 1, since the ion trapping material 41 is contained in the gate insulating layer 40, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 is prevented, so that the source electrode, the drain electrode, Current between the gate electrode and the source electrode is suppressed, and as a result, the off-current that is the current flowing between the source electrode and the drain electrode when the gate voltage is turned off becomes extremely small. . Therefore, good switching characteristics of the thin film transistor 1 can be obtained, and power consumption can be kept low.
In the present embodiment, the thin film transistor 1 has been described with a top gate structure as a representative, but the thin film transistor 1 of the present invention is not limited to such a case. It can also be applied to a bottom gate structure.

Such a thin film transistor 1 can be manufactured as follows, for example.
1 includes a step [A1] of forming a source electrode 20a and a drain electrode 20b on a substrate 10, and a step of forming an organic semiconductor layer 30 so as to cover the source electrode 20a and the drain electrode 20b. [A2], a step [A3] of forming the gate insulating layer 40 on the organic semiconductor layer 30, and a step [A4] of forming the gate electrode 50 on the gate insulating layer 40.

[A1] Source and Drain Electrode Formation Step First, the source electrode 20a and the drain electrode 20b are formed on the substrate 10 (see FIG. 2A).
The source electrode 20a and the drain electrode 20b can be formed on the substrate 10 by using, for example, an etching method, a lift-off method, or the like.

  When the source electrode 20a and the drain electrode 20b are formed on the substrate 10 by etching, I: First, a metal film (metal layer) is formed on the entire surface of the substrate 10. This includes, for example, chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, and laser CVD, vacuum deposition, sputtering (low temperature sputtering), dry plating methods such as ion plating, electrolytic plating, immersion plating, and electroless plating. It can be formed by a wet plating method such as a thermal spraying method, a sol-gel method, a MOD method, or a metal foil bonding.

II: Next, a resist layer is formed on the metal film (surface) by using, for example, a photolithography method, a microcontact printing method, or the like.
III: Next, by using this resist layer as a mask, the metal film is etched to remove unnecessary portions of the metal film, and the source electrode 20a and the drain electrode 20b having a predetermined shape are obtained on the substrate 10. . For the removal of the metal film, for example, one or more of physical etching methods such as plasma etching, reactive ion etching, beam etching, and optical assist etching, and chemical etching methods such as wet etching are used. They can be used in combination.

  Further, when the source electrode 20a and the drain electrode 20b are formed on the substrate 10 by the lift-off method, I: First, in the region other than the region where the source electrode 20a and the drain electrode 20b are formed on the substrate 10, A resist layer is formed using a method similar to that described in the etching method. II: Next, a metal film (metal layer) is formed on the entire surface of the substrate 10 on the resist layer side by using the same method as described in the etching method. III: Next, by removing the resist layer, the source electrode 20a and the drain electrode 20b having a predetermined shape are obtained on the substrate 10. For the removal of the resist layer, the same method as described in the removal of the metal film can be used in the etching method.

[A2] Organic Semiconductor Layer Formation Step Next, the organic semiconductor layer 30 is formed so as to cover the source electrode 20a and the drain electrode 20b (see FIG. 2B). At this time, a channel region 31 is formed between the source electrode 20a and the drain electrode 20b.
When the organic semiconductor layer 30 is made of a polymer organic semiconductor material (polymeric organic semiconductor material), a coating method using a spin coater method, a dip method, or a printing method using an ink jet method or a screen printing method is used. Can be formed.

  Further, when the organic semiconductor layer 30 is composed of a low molecular organic semiconductor material, it is made soluble by using a vapor deposition method or a precursor, so that a coating method using a spin coater method, a dip method or the like, an ink jet method, After a coating film is formed using a printing method using a screen printing method or the like, the coating film can be formed into a desired one by annealing the coating film.

  Note that the formation region of the organic semiconductor layer 30 is not limited to the illustrated configuration, and the organic semiconductor layer 30 may be formed only in a region (channel region 31) between the source electrode 20a and the drain electrode 20b. Thereby, when a plurality of thin film transistors (elements) 1 are arranged on the same substrate, the leakage current and crosstalk between the elements are suppressed by independently forming the organic semiconductor layer 30 of each element. Can do. Moreover, the usage-amount of organic-semiconductor material can be reduced and manufacturing cost can also be reduced.

[A3] Gate Insulating Layer Forming Step Next, the gate insulating layer 40 is formed on the organic semiconductor layer 30 (see FIG. 2C).
First, after mixing the ion-trapping substance 41 with a solution containing an insulating material or a precursor thereof, a liquid material is prepared by, for example, stirring and dispersing treatment with ultrasonic waves.
This liquid material is applied (supplied) so as to cover the organic semiconductor layer 30 and then subjected to post-treatment (for example, heating, infrared irradiation, application of ultrasonic waves, etc.) to the coating film as necessary. Thus, the gate insulating layer 40 can be formed.

[A4] Gate Electrode Formation Step Next, the gate electrode 50 is formed on the gate insulating layer 40 (see FIG. 2D).
The gate electrode 50 can be formed in the same manner as the source electrode 20a and the drain electrode 20b. In addition, for example, a conductive material containing conductive particles is applied (supplied) onto the gate insulating layer 40 to form a coating film. After forming the film, it can be formed by subjecting this coating film to post-treatment (for example, heating, irradiation with infrared rays, application of ultrasonic waves, etc.) as necessary.

Examples of the conductive material containing conductive particles include a dispersion in which metal fine particles such as silver colloid and copper colloid are dispersed, a polymer mixture containing metal fine particles, and the like.
The supply of the conductive material onto the gate insulating layer 40 is preferably performed using an inkjet method. According to the ink jet method, the conductive material can be supplied with high accuracy corresponding to the shape of the gate electrode 50 to be formed. Thereby, the gate electrode 50 can be formed with high dimensional accuracy.

Through the steps as described above, the thin film transistor 1 of the first embodiment is obtained.
In the thin film transistor of this embodiment, between the source electrode 20a and the drain electrode 20b and the organic semiconductor layer 30, between the organic semiconductor layer 30 and the gate insulating layer 40, and between the gate insulating layer 40 and the gate electrode 50. Each can be added one or more layers for any purpose.

<< Second Embodiment >>
Next, a second embodiment of the thin film transistor of the present invention will be described.
FIG. 3 is a schematic sectional view showing a second embodiment of the thin film transistor of the present invention, and FIG. 4 is a view (longitudinal sectional view) for explaining a manufacturing method of the thin film transistor shown in FIG.
Hereinafter, the thin film transistor of the second embodiment will be described with a focus on differences from the first embodiment, and description of similar matters will be omitted.

The thin film transistor 1 according to the second embodiment is different from the thin film transistor 1 according to the first embodiment except that the configuration of the gate insulating layer 40 is different.
That is, in the thin film transistor 1 shown in FIG. 3, the gate insulating layer 40 is disposed in the vicinity of the interface between the gate electrode 50 and the first ion-trapping substance-containing layer 43 disposed in the vicinity of the interface with the organic semiconductor layer 30. The second ion-trapping substance-containing layer 45 is formed, and the other part, that is, the part between the layers 43 and 45 is constituted by the insulating layer 44 substantially not containing the ion-trapping substance 41. .

The first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45 are insulating layers containing the ion trapping substance 41, respectively.
In this embodiment, the first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45 are obtained by dispersing the ion trapping substance 41 in a matrix (base material) 42 made of an insulating material. It is configured.

The ion trapping substance 41 has a function of trapping ions as described in the first embodiment.
Therefore, when the vicinity of the interface between the gate insulating layer 40 and the gate electrode 50 is configured by the second ion trapping substance-containing layer 45, the metal ions diffused from the gate electrode 50 are contained in the second ion trapping substance-containing layer 45. Therefore, it is possible to prevent the metal ions from diffusing into the insulating layer 44. As a result, the function of the gate insulating layer 40 as the insulating layer can be reliably prevented or suppressed.

  Furthermore, when the vicinity of the interface between the gate insulating layer 40 and the organic semiconductor layer 30 is configured by the first ion trapping substance-containing layer 43, metal ions are transmitted from the gate electrode 50 through the second ion trapping substance-containing layer 45. Even if it has diffused, metal ions can be reliably trapped by the first ion trapping substance-containing layer 43 without reaching the organic semiconductor layer 30. In addition, alkali metal ions mixed as impurities in the gate insulating layer 40 can be trapped by the first ion trapping substance-containing layer 43 without reaching the organic semiconductor layer 30.

That is, the first ion trapping substance-containing layer 43 causes both the metal ions diffused from the gate electrode 50 and the alkali metal ions mixed as impurities in the gate insulating layer 40 to reach the organic semiconductor layer 30. Can be captured without.
As described above, the diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 is also prevented by the gate insulating layer 40 configured as in this embodiment, so that the metal ions diffuse into the organic semiconductor layer 30. Therefore, the generation of leakage current between the source electrode and the drain electrode and between the gate electrode and the drain electrode can be reliably suppressed. As a result, the off-state current in the thin film transistor 1 can be kept low.

  In particular, in this embodiment, the ion trapping substance 41 is contained in the first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45, and the other part (insulating layer 44) is the ion trapping substance. In other words, the ion trapping substance 41 is unevenly distributed in the vicinity of the interface between the gate insulating layer 40 (matrix 42) and the organic semiconductor layer 30 and in the vicinity of the interface with the gate electrode 50. In such a configuration, the metal ions diffused from the gate electrode 50 to the gate insulating layer 40 by the ion trapping substances 41 unevenly distributed at these interfaces, and the metal ions to be transferred from the gate insulating layer 40 to the organic semiconductor layer 30. Is efficiently captured before reaching the organic semiconductor layer 30. Therefore, compared with the case where the ion trapping material 41 is dispersed throughout the gate insulating layer 40, the amount of the ion trapping material 41 that does not participate in ion trapping can be reduced. Thereby, the usage-amount of the ion trap substance 41 can be reduced, and the manufacturing cost of the thin-film transistor 1 can be restrained low. In addition, by having the insulating layer 44 that does not substantially contain the ion trapping substance 41, the function of the gate insulating layer 40 as the insulating layer can be further improved.

As a specific example of the ion trapping substance 41 to be contained in the first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45, the same ones as in the case of the first embodiment can be used.
The ion trapping substances 41 contained in the first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45 may be the same or different. It is preferable to select one corresponding to the metal ion expected to diffuse. Thereby, the capture rate of the metal ions diffusing into the layers 43 and 45 can be improved.

  Specifically, since the layer 45 is disposed in the vicinity of the interface with the gate electrode 50 in the second ion trapping substance-containing layer 45, metal ions derived from the gate electrode 50 mainly diffuse. Come. Therefore, as the ion trapping substance 41 to be contained in the second ion trapping substance-containing layer 45, the one having a cyclic structure capable of trapping metal ions derived from the gate electrode among those exemplified in the first embodiment is a main component. Is preferable. Thereby, the capture rate of the metal ions derived from the gate electrode 50 can be further improved.

  On the other hand, the first ion-trapping substance-containing layer 43 includes a second of metal ions (mainly alkali metal ions) mixed as impurities in the gate insulating layer 40 and metal ions diffused from the gate electrode 50. The metal ions that have passed (permeated) through the ion trapping substance-containing layer 45 are diffused. Therefore, as the ion trapping material 41 to be contained in the first ion trapping material-containing layer 43, among those exemplified in the first embodiment, those having a cyclic structure capable of trapping alkali metal ions, and those derived from the gate electrode It is preferable that both have a cyclic structure capable of capturing metal ions. Thereby, the alkali metal ion mixed in the gate insulating layer 40 in the manufacturing process and the metal ion derived from the gate electrode can be efficiently captured.

  In the present embodiment, the case where the gate insulating layer 40 includes both the first ion trapping substance-containing layer 43 and the second ion trapping substance-containing layer 45 has been described. However, the present embodiment is not limited to such a case. The gate insulating layer 40 may be provided with either the first ion trapping substance-containing layer 43 or the second ion trapping substance-containing layer 45. Also with this configuration, diffusion of metal ions from the gate insulating layer 40 to the organic semiconductor layer 30 can be suitably prevented or suppressed. In addition, it is preferable that the first ion-trapping substance-containing layer 43 is provided for diffusing alkali metal ions contained in the gate insulating layer 40. Thereby, the alkali ion metal diffused from the insulating layer 44 can be reliably trapped by the first ion trapping substance-containing layer 43.

  Further, in the present embodiment, the second ion trapping substance-containing layer 45 is provided generally near the upper surface of the gate insulating layer 40, but the second ion trapping substance-containing layer 45 is at least the gate electrode 50. It suffices if it is provided near the interface. That is, the second ion-trapping substance-containing layer 45 is provided only near the interface of the gate electrode 50 in the vicinity of the upper surface of the gate insulating layer 40, and the other part is formed by the insulating layer 44 that does not substantially contain the ion-trapping substance. You may make it comprise.

As the insulating material used in the first ion trapping substance-containing layer 43, the second ion trapping substance-containing layer 45, and the insulating layer 44, the same materials as those in the first embodiment can be used.
Such a thin film transistor 1 can be manufactured as follows, for example.
The thin film transistor 1 shown in FIG. 3 is manufactured in the same manner as in the first embodiment except that the gate insulating layer forming step [B3] is used instead of the gate insulating layer forming step [A3] described in the first embodiment. be able to.

[B3] Gate Insulating Layer Formation Step In this step, the gate insulating layer 40 is formed on the organic semiconductor layer 30 formed in the step [A2].
[B3-1] First, the first ion-trapping substance-containing layer 43 is formed on the organic semiconductor layer 30 (see FIG. 4A).

First, after the ion-trapping substance 41 is mixed with a solution containing an insulating material or a precursor thereof, a liquid material is prepared by, for example, stirring and dispersing treatment with ultrasonic waves.
Next, this liquid material is applied (supplied) so as to cover the organic semiconductor layer 30 and then subjected to post-treatment (for example, heating, irradiation with infrared rays, application of ultrasonic waves, etc.) to the coating film as necessary. Apply. Thereby, the first ion trapping substance-containing layer 43 can be formed on the organic semiconductor layer 30.

[B3-2] Next, the insulating layer 44 is formed on the first ion-trapping substance-containing layer 43 (see FIG. 4B).
First, a liquid material is prepared by subjecting an insulating material or a precursor thereof to dispersion treatment using, for example, stirring and ultrasonic waves.
Next, this liquid material is applied (supplied) so as to cover the first ion-trapping substance-containing layer 43, and then post-treatment (for example, heating, infrared irradiation, super Application of sound waves). Thereby, the insulating layer 44 can be formed on the first ion trapping substance-containing layer 43.

[B3-3] Next, a second ion-trapping substance-containing layer 45 is formed on the insulating layer 44 (see FIG. 4C).
First, after the ion-trapping substance 41 is mixed with a solution containing an insulating material or a precursor thereof, a liquid material is prepared by, for example, stirring and dispersing treatment with ultrasonic waves.
Next, this liquid material is applied (supplied) so as to cover the insulating layer 44, and then post-treatment (for example, heating, infrared irradiation, application of ultrasonic waves, etc.) is applied to the coating film as necessary. Apply. Thereby, the second ion trapping substance-containing layer 45 can be formed on the insulating layer 44.

Through the above steps, the gate insulating layer 40 in which the first ion trapping substance-containing layer 43, the insulating layer 44, and the second ion trapping substance-containing layer 45 are stacked in this order from the organic semiconductor layer 30 side is obtained.
Also by the thin film transistor 1 of the second embodiment, the same operation and effect as the thin film transistor 1 of the first embodiment can be obtained.
Furthermore, in the thin film transistor 1 of the second embodiment, the ion trapping material 41 is unevenly distributed near the interface between the gate insulating layer 40 and the organic semiconductor layer 30 and near the interface with the gate electrode 50, so that it diffuses from the gate electrode. Thus, it is possible to effectively capture the metal ions and the ions to be transferred from the gate insulating layer to the organic semiconductor layer.

<Display device>
Next, an electrophoretic display device will be described as an example of a display device incorporating an active matrix device including the thin film transistor 1 as described above.
FIG. 5 is a longitudinal sectional view showing an embodiment when the display device of the present invention is applied to an electrophoretic display device, and FIG. 6 is a block diagram showing a configuration of an active matrix device included in the electrophoretic display device shown in FIG. It is.

An electrophoretic display device 200 shown in FIG. 5 includes an active matrix device (an electronic circuit of the present invention) 300 provided on a substrate 500 and an electrophoretic display unit 400 electrically connected to the active matrix device 300. It is configured.
As shown in FIG. 6, the active matrix device 300 includes a plurality of data lines 301 orthogonal to each other, a plurality of scanning lines 302, and a thin film transistor 1 provided near each intersection of the data lines 301 and the scanning lines 302. And have.

The gate electrode 50 of the thin film transistor 1 is connected to the scanning line 302, the source electrode 20a is connected to the data line 301, and the drain electrode 20b is connected to a pixel electrode (individual electrode) 401 described later.
As shown in FIG. 5, the electrophoretic display unit 400 includes a pixel electrode 401, a microcapsule 402, a transparent electrode (common electrode) 403, and a transparent substrate 404 that are sequentially stacked on a substrate 500. Yes.

The microcapsule 402 is fixed between the pixel electrode 401 and the transparent electrode 403 by a binder material 405.
The pixel electrodes 401 are divided so as to be regularly arranged in a matrix, that is, vertically and horizontally.
In each capsule 402, an electrophoretic dispersion liquid 420 including a plurality of types of electrophoretic particles having different characteristics, and in this embodiment, two types of electrophoretic particles 421 and 422 having different charges and colors (hues) are encapsulated. Has been.

In such an electrophoretic display device 200, when a selection signal (selection voltage) is supplied to one or a plurality of scanning lines 302, a thin film transistor connected to the scanning line 302 to which the selection signal (selection voltage) is supplied. 1 is turned on.
Thereby, the data line 301 connected to the thin film transistor 1 and the pixel electrode 401 are substantially conducted. At this time, if desired data (voltage) is supplied to the data line 301, this data (voltage) is supplied to the pixel electrode 401.
As a result, an electric field is generated between the pixel electrode 401 and the transparent electrode 403, and the electrophoretic particles 421 and 422 are either one of the electrophoretic particles 421 and 422 depending on the direction and strength of the electric field and the characteristics of the electrophoretic particles 421 and 422 Electrophoresis in the direction of the electrode.

On the other hand, when supply of the selection signal (selection voltage) to the scanning line 302 is stopped from this state, the thin film transistor 1 is turned off, and the data line 301 and the pixel electrode 401 connected to the thin film transistor 1 are in a non-conductive state. Become.
Therefore, by appropriately combining the supply and stop of the selection signal to the scanning line 302 or the supply and stop of the data to the data line 301, the display surface side (transparent substrate 404 side) of the electrophoretic display device 200 is provided. A desired image (information) can be displayed.

In particular, in the electrophoretic display device 200 of the present embodiment, it is possible to display a multi-tone image by making the colors of the electrophoretic particles 421 and 422 different.
In addition, since the electrophoretic display device 200 of the present embodiment includes the active matrix device 300, the thin film transistor 1 connected to the specific scanning line 302 can be selectively turned on / off. And the circuit operation can be speeded up, so that a high quality image (information) can be obtained.
In addition, since the electrophoretic display device 200 according to the present embodiment operates with a low driving voltage, power saving can be achieved.
Note that the display device of the present invention is not limited to application to such an electrophoretic display device 200, but can also be applied to a liquid crystal display device, an organic or inorganic EL display device, and the like.

<Electronic equipment>
Such an electrophoretic display device 200 can be incorporated into various electronic devices. Hereinafter, an electronic apparatus of the present invention including the electrophoretic display device 200 will be described.
<< Electronic Paper >>
First, an embodiment when the electronic apparatus of the present invention is applied to electronic paper will be described.

FIG. 7 is a perspective view showing an embodiment when the electronic apparatus of the present invention is applied to electronic paper.
An electronic paper 600 shown in this figure includes a main body 601 composed of a rewritable sheet having the same texture and flexibility as paper, and a display unit 602.
In such electronic paper 600, the display unit 602 includes the electrophoretic display device 200 as described above.

<< Display >>
Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.
8A and 8B are diagrams showing an embodiment in which the electronic apparatus of the present invention is applied to a display. FIG. 8A is a cross-sectional view, and FIG. 8B is a plan view.
A display 800 shown in this figure includes a main body 801 and an electronic paper 600 that is detachably provided to the main body 801. The electronic paper 600 has the same configuration as described above, that is, the configuration shown in FIG.

  The main body 801 has an insertion port 805 into which the electronic paper 600 can be inserted on the side (right side in the drawing), and two pairs of conveying rollers 802a and 802b are provided inside. When the electronic paper 600 is inserted into the main body 801 through the insertion port 805, the electronic paper 600 is installed in the main body 801 in a state of being sandwiched between the pair of conveyance rollers 802a and 802b.

  Further, a rectangular hole 803 is formed on the display surface side of the main body 801 (the front side in the drawing (b) below), and a transparent glass plate 804 is fitted into the hole 803. Thereby, the electronic paper 600 installed in the main body 801 can be viewed from the outside of the main body 801. That is, in the display 800, the display surface is configured by visually recognizing the electronic paper 600 installed in the main body 801 on the transparent glass plate 804.

In addition, a terminal portion 806 is provided at the leading end portion (left side in the drawing) of the electronic paper 600, and the terminal portion with the electronic paper 600 installed on the main body portion 801 is provided inside the main body portion 801. A socket 807 to which 806 is connected is provided. A controller 808 and an operation unit 809 are electrically connected to the socket 807.
In such a display 800, the electronic paper 600 is detachably installed on the main body 801, and can be carried and used while being detached from the main body 801.

Further, in such a display 800, the electronic paper 600 is configured by the electrophoretic display device 200 as described above.
Note that the electronic apparatus of the present invention is not limited to the application to the above, and for example, a television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, an electronic Examples include newspapers, word processors, personal computers, workstations, videophones, POS terminals, and devices equipped with touch panels. The electrophoretic display device 200 can be applied to the display units of these various electronic devices. is there.

Although the thin film transistor, the electronic circuit, the display device, and the electronic device of the present invention have been described above, the present invention is not limited to these.
For example, in the third embodiment and the fourth embodiment, the gate insulating layer 40 is replaced with the first ion-trapping substance-containing layer 43, the insulating layer 44, and the second ion-trapping substance-containing layer 45 as in the second embodiment. It is good also as a 3 layer structure which consists of.
In addition, the configuration of each part of the thin film transistor, electronic circuit, display device, and electronic device of the present invention can be replaced with any one that can exhibit the same function, or can be added with any configuration. it can.

Next, specific examples of the present invention will be described.
In Table 1 shown below, specific ion-trapping substances, types and contents of insulating materials used in each example described below are listed and displayed.
1. Production of Thin Film Transistor In each of the following Examples and Comparative Examples, 5 thin film transistors were produced.

Example 1
-1- First, a glass substrate was prepared, and the surface was degreased by washing with ethanol.
-2- Next, a source electrode and a drain electrode made of Au were formed on a glass substrate.
First, an Au vapor deposition film was formed on this glass substrate by vapor deposition of Au.
Subsequently, this Au vapor deposition film was patterned using the photolithographic method, and the source electrode and the drain electrode were formed.

-3- Next, after the oxygen plasma treatment on the source electrode and the drain electrode, a toluene solution of a fluorene-bithiophene copolymer (F8T2) was applied on the substrate by a spin coating method, and then 60 ° C. × 10 Dry in minutes.
Thereby, an organic semiconductor layer having an average thickness of 30 nm was formed.
-4- Next, in Example 1, 12-crown-4 in which n is 2 in the above chemical formula 1 (a) as an ion trapping substance, and polyvinylphenol (PVP) as an insulating material (insulating polymer). ) Were used to form a gate insulating layer containing these materials on the organic semiconductor layer.

First, a butyl acetate solution was prepared as a solvent, and PVP and 12-crown-4 were mixed with this solvent at a weight ratio of 5: 1 and stirred to prepare a gate insulating layer forming material (liquid material). .
Next, a gate insulating layer forming material was applied on the organic semiconductor layer by a spin coating method, and then dried at 60 ° C. for 10 minutes.
Thereby, a gate insulating layer having an average thickness of 200 nm was formed.

-5- Next, an Ag fine particle aqueous dispersion was applied to the portion of the gate insulating layer corresponding to the region between the source electrode and the drain electrode by an inkjet method, and then dried at 80 ° C for 10 minutes. .
Thereby, a gate electrode having an average thickness of 100 nm was formed.
Through the above process, a thin film transistor was obtained.

(Example 2)
A thin film transistor was obtained in the same manner as in Example 1 except that the mixing ratio of PVP and 12-crown-4 was 3: 1 (weight ratio).
(Example 3)
A thin film transistor is manufactured in the same manner as in Example 1 except that 18-crown-6 in which n is 4 in the above chemical formula 1 (a) is used as the ion trapping substance instead of 12-crown-4. Obtained.

Example 4
A thin film transistor was obtained in the same manner as in Example 1 except that, instead of 12-crown-4, cryptate-211 of the above chemical formula 6 (b) was used as the ion trapping substance.
(Example 5)
The same as Example 1 except that instead of 12-crown-4, a thiacrown ether having n of 4 in the above chemical formula 4 (an ion trapping substance that selectively traps Ag ions) was used as the ion trapping substance. Thus, a thin film transistor was obtained.

(Example 6)
As the ion-trapping substance, except that a mixture of cryptate-211 and thiacrown ether having n of 4 in the above chemical formula 4 in a 1: 1 (weight ratio) instead of 12-crown-4 was used. A thin film transistor was obtained in the same manner as in Example 1.
(Example 7)
Example 1 except that the gate insulating layer was a three-layered structure composed of the following first ion-trapping substance-containing layer, insulating layer, and second ion-trapping substance-containing layer. Thus, a thin film transistor was obtained.

  First, PVP is used as an insulating material (insulating polymer) by mixing 1: 1 (weight ratio) of cryptate-211 and thiacrown ether having n of 4 in the above chemical formula 4 as an ion trapping substance. The first material for forming an ion trapping substance-containing layer was prepared by dissolving in a butyl acetate solution so that the weight ratio of these insulating materials to the ion trapping substance was 5: 1. Next, the first ion trapping substance-containing layer forming material was applied on the organic semiconductor layer by a spin coating method, and then dried at 60 ° C. for 10 minutes. As a result, a first ion-trapping substance-containing layer having an average thickness of 50 nm was formed.

Next, the insulating layer forming material was prepared by dissolving PVP in a butyl acetate solution. Next, an insulating layer forming material was applied on the first ion-trapping substance-containing layer by a spin coating method, and then dried at 60 ° C. for 10 minutes. Thereby, an insulating layer having an average thickness of 100 nm was formed.
Next, a thiacrown ether having the above formula 4 and n of 4 is used as the ion trapping substance and PVP is used as the insulating material (insulating polymer), and the weight ratio of these insulating material and ion trapping substance is 5: 1. Thus, the second ion-trapping substance-containing layer forming material was prepared by dissolving in a butyl acetate solution. Next, a second ion trapping substance-containing layer forming material was applied on the insulating layer by a spin coating method, and then dried at 60 ° C. for 10 minutes. As a result, a second ion-trapping substance-containing layer having an average thickness of 50 nm was formed.
Thereby, a gate insulating layer having an average thickness of 200 nm was formed.

(Example 8)
A thin film transistor was obtained in the same manner as in Example 1 except that polystyrene was used instead of PVP as the insulating material.
Example 9
In place of 12-crown-4, a cycloolefin-containing polymer having the above chemical formula 11 (e) (m is 200, n is 300, and R ¹ and R ² are methyl groups) is used as the ion trapping substance. A thin film transistor was obtained in the same manner as in Example 1 except that it was used.
(Comparative example)
A thin film transistor was obtained in the same manner as in Example 1 except that the addition of the ion trapping substance was omitted.

2. Evaluation of Thin Film Transistor First, for the thin film transistor manufactured in each Example and Comparative Example, the off-current was measured immediately after the manufacture.
Next, these thin film transistors were left in the atmosphere (25 ° C.) for 30 days, and then the off-current was measured again.

In addition, the measurement of the off-current was performed for five thin film transistors in each of the examples and the comparative examples.
Here, the off-current is a current that flows between the source electrode and the drain electrode when no voltage is applied to the gate electrode.
Therefore, the closer the off-state current is to 0, the thinner the thin film transistor has better characteristics.

Then, the off-current immediately after the production and 30 days after the measurement measured in the comparative example were used as reference values, and the off-current immediately after the production and after 30 days measured in each example were evaluated according to the following four criteria.
A: Less than 0.5 times the measured value of the comparative example. O: More than 0.5 times and less than 1.0 times the measured value of the comparative example. Δ: With respect to the measured value of the comparative example, It is 1.0 times or more and less than 1.2 times. X: It is 1.2 times or more with respect to the measured value of the comparative example.

As shown in Table 1, in each of the thin film transistors of each example, the off current immediately after manufacture was almost equal to or slightly superior to the thin film transistor of the comparative example, but the off current after 30 days was low. Suppressed results were obtained.
Thereby, in the thin-film transistor of this invention, it became clear that the diffusion of the metal ion from a gate insulating layer to an organic-semiconductor layer was prevented or suppressed suitably.
In particular, the thin film transistor of Example 6 using two types of ion trapping substances, Example 7 provided with a first ion trapping substance-containing layer and a second ion trapping substance-containing layer, and further, non-shared electrons in the monomer component In the thin film transistor of Example 9 using the insulating polymer having no pair, the off-current was more effectively suppressed to a low level.

It is a schematic sectional drawing which shows 1st Embodiment of the thin-film transistor of this invention. It is a figure (longitudinal sectional drawing) for demonstrating the manufacturing method of the thin-film transistor shown in FIG. It is a schematic sectional drawing which shows 2nd Embodiment of the thin-film transistor of this invention. FIG. 4 is a diagram (longitudinal sectional view) for explaining a manufacturing method of the thin film transistor shown in FIG. 3. It is a longitudinal cross-sectional view which shows embodiment of the electrophoretic display apparatus to which the display apparatus of this invention is applied. FIG. 6 is a block diagram illustrating a configuration of an active matrix device included in the electrophoretic display device illustrated in FIG. 5. It is a perspective view which shows embodiment of the electronic paper to which the electronic device of this invention is applied. It is a figure which shows embodiment of the display to which the electronic device of this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thin-film transistor 10 ... Substrate 20a ... Source electrode 20b ... Drain electrode 30 ... Organic-semiconductor layer 31 ... Channel region 40 ... Gate insulating layer 41 ... Ion trap material 42 ... Matrix 43 ... 1st Layer of ion trapping substance 44 ... Insulating layer 45 ... Second layer of ion trapping substance 50 ... Gate electrode 200 ... Electrophoretic display device 300 ... Active matrix device 301 ... Data line 302 ... Scanning line 400 …… Electrophoretic display portion 401 …… Pixel electrode 402 …… Microcapsule 420 …… Electrophoretic dispersion liquid 421, 422 …… Electrophoretic particles 403 …… Transparent electrode 404 …… Transparent substrate 405 …… Binder material 500 …… Substrate 600 ... Electronic paper 601 ... Main body 602 ... Display unit 800 ... ... Display 801 ... Main body 802a, 802b ... Conveying roller pair 803 ... Hole 804 ... Transparent glass plate 805 ... Insertion port 806 ... Terminal part 807 ... Socket 808 ... Controller 809 ... Operation part

Claims (15)

A gate electrode;
An organic semiconductor layer;
A gate insulating layer located between the gate electrode and the organic semiconductor layer;
A source electrode and a drain electrode that move carriers through the organic semiconductor layer, and
The thin film transistor according to claim 1, wherein the gate insulating layer contains an ion trapping material capable of trapping metal ions.   The thin film transistor according to claim 1, wherein the ion trapping material is capable of trapping alkali metal ions contained in the gate insulating layer. The gate electrode contains a metal element;
The thin film transistor according to claim 1, wherein the ion trapping substance is capable of trapping metal ions derived from the metal element.   The ion trapping substance has a ring structure, and the kind and size of the ring of the ring structure is selected according to the difference in the kind and / or ion diameter of the metal ion. The thin film transistor described.   5. The thin film transistor according to claim 4, wherein the cyclic structure includes at least one heteroatom selected from an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom.   The thin film transistor according to claim 5, wherein the ring structure includes six or more carbon atoms and two or more at least one kind of the heteroatoms in the ring.   The thin film transistor according to any one of claims 1 to 6, wherein the gate insulating layer is formed by dispersing the ion trapping substance in a base material made of an insulating material.   The thin film transistor according to claim 7, wherein the insulating material is an insulating polymer.   The thin film transistor according to claim 8, wherein the insulating polymer includes a monomer having an unshared electron pair of 1 or less.   The thin film transistor according to claim 7, wherein the ion trapping substance is unevenly distributed in the vicinity of an interface between the base material and the organic semiconductor layer.   The thin film transistor according to claim 7, wherein the ion trapping substance is unevenly distributed in the vicinity of an interface between the base material and the gate electrode.   The thin film transistor according to claim 7, wherein a content of the ion trapping material in the gate insulating layer is 1 to 40 wt%.   An electronic circuit comprising the thin film transistor according to claim 1.   A display device comprising the electronic circuit according to claim 13.   An electronic apparatus comprising the display device according to claim 14.

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