JPH0795169B2 - Optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a drive section comprising a field effect transistor (hereinafter abbreviated as FET element) having a first π-conjugated polymer as a semiconductor layer, The present invention relates to an optical device, in particular, a display device and an optical shutter, which is configured by a display unit including an electrochemical cell having a drain electrode coated with a second π-conjugated polymer as a working electrode.

[Conventional technology]

As a conventional optical device similar to the present invention, there is an electrochromic display (hereinafter abbreviated as ECD element) in addition to a liquid crystal display device having a built-in FET element. First, F
In a liquid crystal display device with a built-in ET element, the FET element of the drive section and the liquid crystal of the display section were composed of different materials, inorganic and organic. For example, the semiconductor device of the FET element is made of inorganic single crystal silicon, polycrystalline silicon, or amorphous silicon, and the display unit is made of organic nematic liquid crystal to form an optical device. That is, as shown in the cross-sectional side view of FIG. 2, an electric field is applied through the insulating film 3 by the voltage applied to the gate electrode 2 on the substrate 1 to form the inorganic semiconductor layer 6 between the source electrode 4 and the drain electrode 5. The display is performed by changing the orientation of the liquid crystal 15 by changing the resistance, causing the pair of transparent electrodes 11 facing each other and subjected to the orientation treatment to accumulate or release charges. At this time, the display was made depending on whether the polarized light transmitted through the glass plate 16 with the polarizing plate can pass through the liquid crystal 15 depending on the orientation of the liquid crystal molecules. 17
Is a wiring for electrically connecting the drain electrode 5 and one of the transparent electrodes 11. In the case of a liquid crystal display device incorporating this FET element, since the charge accumulation and discharge of the transparent electrode 11 of the liquid crystal display unit 14 can be controlled by the gate voltage and the voltage of the transparent electrode 11 which is not connected to the drain electrode 5, Compared to a liquid crystal display device driven by a simple matrix, it has the advantages of reducing crosstalk and enabling multiple elements ("Liquid Crystal-Application", Koji Okano / Shunsuke Kobayashi, Baifukan). In FIG. 2, 7 is a protective film, and 13 and 14 are a FET element part and a display part, respectively.

Next, the ECD element will be described. As shown in the sectional side view of FIG. 3, the ECD element includes a working electrode 8 covered with a chemical substance 18 that undergoes a color change reaction by an electrochemical redox reaction, a transparent electrode 11 facing the working electrode 8, and a supporting electrolyte. It is composed of an electrolytic solution 10 containing a redox agent. Further, in FIG. 3, 1 is a substrate and 12 is a glass plate. this
In the ECD element, a voltage is applied between the working electrode 8 and the counter electrode 11 to cause an electric current to flow, and thereby the chemical substance 18 is caused to undergo a redox reaction accompanied by discoloration for display (“electrochromic device”, Kenji Nomura, Industrial) Material, Vol. 35, No. 3, 63
page). Since this ECD element has a simple structure, it is easy to increase the area.

[Problems to be solved by the invention]

In the conventional liquid crystal display device with built-in FET element, the FET element part and the display part are composed of different inorganic and organic materials, which complicates the manufacturing process and also the device structure itself. Therefore, there is a problem that the manufacturing cost becomes high. Further, when a single crystal plate or a polycrystalline plate of an inorganic semiconductor is used for the FET element portion, it is difficult to increase the number of elements and the area of the optical device because the size of the substrate is restricted. Even if amorphous silicon formed by a plasma CVD (Chemical Vapor D-eposition) method is used as a semiconductor layer, it is difficult to form amorphous silicon uniformly, and thus it is difficult to increase the number of elements and increase the area.
Further, since the liquid crystal display section uses a polarizing plate, there is a problem that the viewing angle is narrow and it is difficult to see.

On the other hand, although the conventional ECD element has a wide viewing angle and is easy to see,
It was difficult to make multiple elements because it had no built-in ET element.

The present invention has been made to solve the above-mentioned problems, and has a simple basic structure, can simplify the manufacturing process of the device, can reduce the manufacturing cost, and at the same time can increase the number of elements of the device. The purpose of the present invention is to obtain an optical device capable of increasing the area.

[Means for solving problems]

The optical device according to the present invention uses a π-conjugated polymer for the semiconductor layer of the FET element part and the part that causes the color change reaction of the electrochemical cell part, and also the gate of the FET element part and the counter electrode of the electrochemical cell part. The color change reaction is controlled by the voltage applied to the.

[Action]

In the present invention, since the semiconductor layer of the FET element part and the coloring material of the display part are made of organic π-conjugated polymer, the π-conjugated polymer is generally an inorganic semiconductor single crystal plate or polycrystalline plate. , And unlike amorphous silicon, it is easy to obtain a uniform thin film, which facilitates the formation of the semiconductor layer of the FET element part, and also simplifies the basic element structure because the π-conjugated polymer is used in the display part. . Therefore, it becomes easy to increase the number of elements and the area of the device, and the device can be manufactured at low cost.

Further, in the present invention, without using a liquid crystal display element in the display unit, an electrochemical display element using a π-conjugated polymer, that is, an ECD element is used, and since an FET element is attached, It has a wide viewing angle, is easy to see, can be driven by a matrix, and can easily have multiple elements.

That is, in the present invention, the advantages of both the liquid crystal display device incorporating the FET element and the ECD element are incorporated, the basic element structure is simplified, and the manufacturing cost is reduced.

〔Example〕

FIG. 1 is a sectional view of an optical device according to an embodiment of the present invention, in which 1 is a substrate, 2 is a gate electrode provided on one surface of the substrate 1, and 3 is provided on the substrate 1 and the gate electrode 2. The insulating film 4 is a source electrode provided on the insulating film 3, 5 is a drain electrode provided on the insulating film 3 separately from the source electrode 4, and 6 is an insulating film 3, a source electrode 4 and a drain. It is a semiconductor layer made of π-conjugated polymer provided on the electrode 5. Of these, 2 to 6 are FE
A part 13 of the T element is formed, and 7 is a protective film which covers the part 13 of the FET element and separates it from the display part described later. Also, 8
Is a working electrode formed by extending the drain electrode 5 of the FET element 13, 9 is a π-conjugated polymer layer that undergoes an electrochemical color change reaction, 10 is an electrolyte solution containing an electrolyte, and 11 is facing the working electrode 8. The transparent electrode 12 is a glass plate. These 8 to 12 constitute the display unit 14 of the present optical device.

Here, as materials used for the device according to this embodiment, there are the following materials.

Although glass is generally used as the substrate 1, a polymer film such as a polyester film can also be used. FET
In the element portion 13, as the gate electrode 2, gold, platinum,
Metals such as chromium, palladium, aluminum and indium, tin oxide, indium oxide, indium tin oxide (ITO) and the like are generally used, but two or more of these materials may be used together. . Further, p-type silicon, n-type silicon, or an organic polymer having conductivity may be used, and when these are used, the substrate 1 can be omitted. As the insulating film 3 and the protective film 7, an inorganic insulating film of silicon oxide (SiO ₂ ), silicon nitride, aluminum oxide or the like, or an insulating polymer such as polyethylene, polyvinylcarbazole, polyphenylene sulfide or polyparaxylene is used. Of course, two or more of these materials may be used in combination.

Further, as the π-conjugated polymer forming the semiconductor layer 6 of the FET element part 13 and the π-conjugated polymer forming the color changing part 9 of the display part 14, polypyrrole, poly (N-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene), poly (3,4-disubstituted thiophene), polyaniline, polyazulene, polypyrene, polycarbazole, poly (N-substituted carbazole), polyseleno Any of phen, polyfuran, polybenzothiophene, poly (phenylene vinylene), polybenzofuran, poly (paraphenylene), polyindole, polyisothionaphthene, polypyridazine, and polydiacetylene can be used, but they are complex in characteristics. A π-conjugated polymer having a five-membered ring is preferable, and a general formula (However, X is one of S and O atoms, R ₁ and R ₂
Is -H, -COOH, -C _m H _{2m + 1} , -OC _m H _{2m + 1} , and -COOC _m H
_One selected from _{2m + 1} groups, m is an integer from 1 to 10,
n is an integer) and general formula (However, R ₁ and R ₂ are -H, -COOH, -C _m H _{2m + 1} , -OC _m H
_{2m + 1} , and _one selected from the group --COOC _m H _{2m + 1} , R ₃
It is _{-H, -CH 3, -C 2 H} 5, -C 3 H 7, and One selected from among these, m is an integer of 1 to 10 and n is an integer) is preferably used, and two or more of these may be used together.

The π-conjugated polymer is usually an insulator by itself,
A p-type semiconductor can be obtained by doping an appropriate electron acceptor such as perchlorate ion, tetrafluoroborate ion, sulfonate ion, etc., and its conductivity can be controlled widely from the insulator region to the metal region. (Industrial materials, Volume 34, No. 4, p. 55, 1986
Year). In the FET element portion 13 of this embodiment, it is preferable to use a π-conjugated polymer which is doped with an extremely small amount to impart p-type semiconductor properties.

As the source electrode 4 and the drain electrode 5, gold, platinum, chromium, palladium, etc. are generally used, but of course, the material is not limited to these, and tin oxide, indium oxide, indium tin oxide may be used in some cases. (IT
O) or an organic polymer having conductivity may be used.

As a method of forming the π-conjugated polymer thin film 6 of the FET element portion 13 on the intermediate member composed of the gate electrode 2, the insulating film 3, the source electrode 4, and the drain electrode 5, an electrochemical weight is used. A synthetic method (electrolytic polymerization method), a chemical polymerization method (chemical oxidative polymerization method), a spin coating method, a vapor deposition method, or a gas phase polymerization method using a catalyst is used.

For example, in order to form a π-conjugated polymer film having a five-membered heterocyclic ring by an electrolytic polymerization method, a monomer corresponding to the π-conjugated polymer having a five-membered heterocyclic ring and a supporting electrolyte are mixed with an organic solvent or water. The above-mentioned source electrode 4
At least one of the drain electrode 5 (working electrode 8) is used as a working electrode, and a desired hetero five-membered ring is present in the vicinity of the working electrode by causing a polymerization reaction by passing an electric current between the working electrode and a counter electrode such as platinum. -A method is used in which a conjugated polymer is deposited, the deposited? -Conjugated polymer film having a hetero five-membered ring is thoroughly washed, and then dried in a nitrogen atmosphere.
In this case, the precipitated π-conjugated polymer film 6 having a hetero five-membered ring is doped with anions of the supporting electrolyte during the reaction to become a p-type organic semiconductor, and the distance between the source electrode 4 and the drain electrode 5 is sufficiently short. Therefore, the insulating film 3 between both electrodes is also covered with the π-conjugated polymer film 6 having a five-membered heterocyclic ring, and both electrodes are electrically connected by the p-type organic semiconductor film 6. In addition, this p-type organic semiconductor film 6 is formed by controlling the doping amount electrochemically after electrolytic polymerization.
The conductivity can be changed to be suitable for the T element. Here, as the organic solvent, any solvent capable of dissolving the supporting electrolyte and the above-mentioned monomer may be used, for example, acetonitrile, nitrobenzene, benzonitrile, nitromethane, N, N-
Polar solvents such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), dichloromethane, tetrahydrofuran, ethyl alcohol, and methyl alcohol are preferably used alone or as a mixed solvent of two or more kinds. Also, a mixed solvent of the above solvent and water can be used. The supporting electrolyte is a substance that itself does not undergo an oxidation or reduction reaction during electrolytic polymerization, and can impart conductivity to a solution by being dissolved in a solvent,
For example, tetraalkylammonium perchlorate salt, tetraalkylammonium tetrafluoroborate salt, tetraalkylammonium hexafluorophosphate salt, tetraalkylammonium paratoluenesulfonate salt, sodium hydroxide and the like are used, but of course two or more kinds are used together. It doesn't matter.

Next, in order to form a π-conjugated polymer film having a five-membered heterocyclic ring by the chemical oxidative polymerization method, deionized water or a mixed solvent of deionized water and an organic solvent or an organic solvent in a predetermined amount as an initiator is used. Of the oxidizer, and after preparing a solution sufficiently deoxygenated, a predetermined amount of a monomer corresponding to the π-conjugated polymer having a hetero five-membered ring is added to the solution,
Polymerize the monomers. At this time, the substrate 1 on which the gate electrode 2, the insulating film 3, the source electrode 4, the drain electrode 5, and the working electrode 8 are provided in advance, that is, the intermediate member is immersed in this solution for at least 5 minutes or more to form a complex five-membered ring. Has π
-Polymerized films 6 and 9 of conjugated polymer are formed on the FET element part 13 and the display part 14. At this time, a small amount of an oxidizing agent or anion is doped into the π-conjugated polymer films 6 and 9 having a five-membered heterocyclic ring, and then a desired conductivity is obtained by a suitable doping method or electrochemical doping if necessary. It is also possible to use a p-type π-conjugated polymer film having The intermediate member may be immersed in the solution immediately after or simultaneously with the addition of the monomer to the solution. This method is excellent in film thickness controllability and film uniformity, and it is easy to obtain conductivity suitable for FET simultaneously with film formation. Here, ferric chloride, potassium ferricyanide, or the like is used as the initiator, but the initiator is not limited to these. It is possible to use all oxidizing agents whose redox potential of the initiator is higher than the polymerization initiation potential of the monomer.

Besides, in the spin coating method, the uniform π-conjugated polymer films 6 and 9 can be prepared only by dissolving a soluble π-conjugated polymer in a solvent and spin-coating it on the intermediate member. Further, in the vapor deposition method, a vaporizable π-conjugated polymer is used as a vapor deposition source to deposit a uniform π-conjugate polymer on the intermediate member.
The conjugated polymer films 6 and 9 can be produced. Furthermore, a gas phase polymerization method in which a monomer gas is introduced onto the above-mentioned intermediate member coated with a catalyst in advance to carry out polymerization is also used.

Further, in the display portion 14, the electrode 8 obtained by extending the drain electrode 5 of the FET element may be any one as long as it has sufficient electric conductivity and is insoluble in the electrolyte solution 10, such as a metal such as gold, platinum, chromium or aluminum. , A transparent electrode such as tin oxide, indium oxide, indium tin oxide (ITO), p-type silicon or n-type silicon, or an organic polymer having conductivity is used. Of course, two or more of these materials may be used in combination. As the electrode 11 on the glass plate 12, tin oxide, indium oxide, indium tin oxide (IT
It is common to use transparent electrodes such as O). Also,
A conductive organic polymer having an appropriate transparency may be used. Alternatively, two or more of these materials may be used together. As the electrolyte solution 10, the π-conjugated polymer 9 of the display unit 14 is used.
May be any that can cause an electrochemical color change reaction, for example, a solution that can be used for the electrolytic polymerization of the π-conjugated polymers 6 and 9 and does not contain a monomer, or an ion exchange membrane such as Nafion. It is possible to use, for example, a solid electrolyte composed of (1) containing an ionic species that functions as a dopant.

Although the case where the same π-conjugated polymer is used for the FET element section 13 and the display section 14 has been described above, the π-conjugated system polymer used in the FET element section 13 and the π-conjugated system used in the display section 14 are described. The polymers may be different and can be appropriately selected from various π-conjugated polymers from the viewpoint of FET device characteristics and display characteristics. Even when different π-conjugated polymer (A) and (B) are used for the FET element portion 13 and the display portion 14, the above-mentioned π-conjugated polymer film is produced by the electrolytic polymerization method, the chemical oxidation polymerization method, Spin coating, vapor deposition, vapor phase polymerization, etc. are used. When the same π-conjugated polymer is used for the FET element portion 13 and the display portion 14, it is necessary to use a π-conjugated polymer that causes a color change reaction electrochemically. On the other hand, when different π-conjugated polymers are used for the FET element unit 13 and the display unit 14, the π-conjugated polymer used for the display unit 14 needs to electrochemically cause a color change reaction. This characteristic is not particularly required for the π-conjugated polymer used in the FET element unit 13.

The operating mechanism of the FET element 13 of the optical device configured as described above is unclear in many cases, but the π-conjugated polymer 6
Is p-type, at the interface between the π-conjugated polymer film 6 and the insulating film 3, the width of the hole accumulation layer formed on the π-conjugated polymer film 6 side is between the gate electrode 2 and the source electrode 4. It is considered that the resistance between the source electrode 4 and the drain electrode 5 changes due to the change in the effective channel cross section of the hole controlled by the applied voltage. When the π-conjugated polymer film 6 is n-type, the width of the electron accumulation layer formed on the π-conjugated polymer film 6 side at the interface between the π-conjugated polymer film 6 and the insulating film 3 is small. It is considered that the resistance between the source electrode 4 and the drain electrode 5 changes because it is controlled by the voltage applied between the gate electrode 2 and the source electrode 4, and therefore the effective electron channel cross-sectional area changes. In addition, FET element 1
In the case where the π-conjugated polymer film 6 used in 3 has only semiconductivity with low electric conductivity, the gate electrode 2
In addition to metal electrodes, p-type silicon and n-type silicon,
Alternatively, it is considered that a channel is formed in the π-conjugated polymer film 6 and an electric field effect appears even when a material having a high conductivity such as an organic polymer having conductivity is used.

In this embodiment, the FET element 13 and the display section 14 are connected in series. The operation will be described below by taking as an example the case where the π-conjugated polymer 6 in the FET element unit 13 is p-type.
When a negative voltage is applied to the gate electrode 2 with reference to the source electrode 4 and a positive or negative voltage is applied to the transparent electrode 11, the π-conjugated polymer 9 in the display unit 14 causes a color change reaction. This is shown in FIG. 4 as one example of its characteristics (in the figure, the solid line shows the case where the gate voltage is negative, and the broken line shows the case where the gate voltage is positive).
The resistance between 5 decreases by applying a negative voltage to the gate electrode 2, and the working electrode 8 of the display unit 14 connected in series with the FET element 13
This is because the voltage is applied between the counter electrode 11 and the counter electrode 11 and the π-conjugated polymer 9 causes an electrochemical redox reaction. In general, π
-The conjugated polymer causes a color change reaction along with an electrochemical redox reaction. To restore the color, a negative voltage may be applied to the gate electrode 2 and a voltage opposite to that at the time of color change may be applied to the transparent electrode 11. On the other hand, while the positive voltage is applied to the gate electrode 2 with the source electrode 4 as a reference, the transparent electrode 11
Even if a positive or negative voltage is applied to, the color of the π-conjugated polymer 9 of the display unit 14 does not change. This is as shown in FIG.
The resistance between the source / drain electrodes 4 and 5 of the FET element 13 increases, and no voltage is applied between the working electrode 8 and the counter electrode 11 of the display unit 14 which is connected in series with the FET element 13 due to the voltage drop. It is considered that this is because no special redox reaction occurs.

As described above, the optical device according to this embodiment has the FET element unit 1
By changing the gate voltage of 3, it is possible to control whether or not the discoloration reaction of the display unit 14 is possible. Therefore, the present optical element can be so-called matrix driven, and can have multiple elements and a large area. Further, by using an electrochemical display element using a π-conjugated polymer, that is, an ECD element, in the display unit 14, the basic element structure is simplified, can be manufactured at low cost, and the viewing angle is wide and easy to see.

Although the gate electrode 2 is provided on the substrate 1 in the above embodiment, the π-conjugated polymer film is provided on the substrate, and the source electrode and the drain electrode separately from the source electrode are provided thereon. A gate electrode may be provided with an insulating film interposed between the source electrode and the drain electrode. Of course, the FET element part needs to be separated from the electrolytic solution by a protective film.

Alternatively, a gate electrode may be provided on a substrate, an insulating film may be interposed, a π-conjugated polymer film may be provided thereon, and a source electrode and a drain electrode separate from the source electrode may be provided thereon. Good. Alternatively, a source electrode and a drain electrode may be provided on the substrate separately from the source electrode, a π-conjugated polymer film may be provided thereon, and a gate electrode may be provided with an insulating film interposed. In either case, the FET element section must be separated from the electrolytic solution by a protective film.

Further, the optical device according to the above embodiment can be used as a display device by changing the color of the display unit 14, and when the color change of the display unit 14 is a color change between colorless and transparent and colored, the optical device is used. It can also be used as a shutter.

〔The invention's effect〕

As described above, according to the optical device of the present invention, the FET
Since the semiconductor layer of the element section and the color-changing layer of the display section are made of π-conjugated polymer, and the FET element section and the display section are integrated,
The basic unit structure is simple and can be manufactured at low cost, and moreover, it is possible to increase the number of elements and the area.

[Brief description of drawings]

1 is a sectional side view showing an optical device according to an embodiment of the present invention, FIG. 2 is a sectional side view showing a liquid crystal display device incorporating a conventional FET element, and FIG. 3 is a sectional view showing a conventional ECD element. The side view and FIG. 4 use a p-type π-conjugated polymer film.
It is a current-voltage characteristic view of a FET element. 1 is a substrate, 2 is a gate electrode, 3 is a gate insulating film, 4 is a source electrode, 5 is a drain electrode, 6 is a semiconductor layer of an FET element, 7 is a protective film of an FET element, 8 is a working electrode of a display portion, 9 Is a color change layer made of a π-conjugated polymer, 10 is an electrolytic solution, 11 is a transparent electrode, 12 is a glass plate, 13 is a FET element part, 14 is a display part, 1
5 is a liquid crystal layer of the liquid crystal display device, 16 is a glass plate with a polarizing plate, 17
Is a wiring that electrically connects one of the drain electrode and the transparent electrode, and 18 is a chemical substance that causes a color change reaction of the ECD element. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (12)

[Claims] 1. A field effect transistor part which is a current path between a source electrode and a drain electrode, and which controls the conductivity of a semiconductor layer made of a first π-conjugated polymer by a gate voltage through an insulating thin film. A working electrode formed to extend from the drain electrode of the field effect transistor section, a counter electrode of the working electrode, an electrolyte layer between the two electrodes, and an electrochemical electrode formed by covering the working electrode. An optical device comprising two parts, an electrochemical cell part composed of a second π-conjugated polymer that undergoes a color change reaction, and a voltage applied to the gate of the field effect transistor part and An optical device characterized in that an electrochemical color change reaction of the second π-conjugated polymer is controlled by changing the voltage applied to the counter electrode of the electrochemical cell section. 2. The optical device according to claim 1, wherein the first .pi.-conjugated polymer is different from the second .pi.-conjugated polymer. 3. The optical device according to claim 1, wherein the first π-conjugated polymer is the same as the second π-conjugated polymer. 4. At least one of the first and second π-conjugated polymers is a π-conjugated polymer having a five-membered heterocyclic ring. Item 3. The optical device according to any one of items 3. 5. The π-conjugated polymer having the above-mentioned five-membered heterocyclic ring has the general formula (However, X is one of S and O atoms, R ₁ and R ₂
Is -H, -COOH, -C _m H _{2m + 1} , -OC _m H _{2m + 1} , and -COOC _m H
The optical device according to claim 4, wherein _one of _{2m + 1} , m is an integer of 1 to 10, and n is an integer. 6. The π-conjugated polymer having a five-membered heterocyclic ring has the general formula (However, R ₁ and R ₂ are -H, -COOH, -C _m H _{2m + 1} , -OC _m H
_{2m + 1} , and _one of --COOC _m H _{2m + 1} , R ₃ is --H, --C
_{H 3, -C 2 H 5,} -C 3 H 7, (M is an integer from 1 to 10 and n is an integer)
The optical device according to claim 4, characterized in that: 7. The optical device according to any one of claims 1 to 6, wherein the π-conjugated polymer is a soluble π-conjugated polymer. 8. The optical device according to any one of claims 1 to 6, wherein the π-conjugated polymer is a vapor-depositable π-conjugated polymer. 9. The optical system according to claim 1, wherein the π-conjugated polymer is a π-conjugated polymer formed by electric field polymerization. apparatus. 10. The optical device according to any one of claims 1 to 9, wherein the electrolytic solution layer of the electrochemical cell portion is made of an organic solvent containing an electrolyte. 11. The optical device according to any one of claims 1 to 9, wherein the electrolyte layer of the electrochemical cell portion is made of an aqueous solution containing an electrolyte. 12. The optical device according to claim 1, wherein the electrolytic solution layer of the electrochemical cell portion is made of a solid electrolyte.