JPS6285224A - Liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Industrial application field]

The present invention relates to a liquid crystal display device in which a μ-conjugated polymer having a five-membered ring is used as a semiconductor layer and a field effect transistor (hereinafter abbreviated as FET element) is used for liquid crystal drive control. [Prior art] When increasing the number of pixels in conventional liquid crystal display devices, a simple matrix consisting of strip-shaped transparent electrode arrays orthogonally opposed is used.
I have been using night panels. In this case, the maximum number of scanning electrodes is approximately determined by the lowest permissible co', I-last ratio of the desired image, and is approximately 60 to 1 (about 10).
Divide the signal electrode into two, or divide the matrix liquid crystal panel into two.
Layer stacking t: Attempts have been made to equivalently increase the number of scanning electrodes incorporated within one screen by layer stacking. However, both had technical limitations and were not very effective methods. Figure 3 is a diagram showing the configuration of a conventional liquid crystal display device, but as a drastic method to eliminate crosses between pixels, each pixel electrode (13) is connected to an FET element as shown in Figure 3. It may be possible to separate pixel selection switches such as
X and + are scanning electrodes, and YI-Y and a are signal electrodes. As a method for realizing this, as shown in "Liquid Crystal □ Application Edition", co-edited by Mitsuharu Okano and Yosuke Kobayashi, Baifukan, FET elements and liquid crystal displays are mounted on a single liquid crystal liquid crystal board, a polycrystalline liquid crystal board, or an amorphous silicon thin film. Attempts have been made to create a section and use it as a liquid crystal display device. That is, by using either single-crystal silicon, polycrystalline silicon, or amorphous silicon to make each pixel electrode (i3) a f-nee FET element, and using this FET element as a switch (14) for driving the liquid crystal, large LCD display area? , Y into many individual small liquid crystal display devices and operate them separately. FIG. 4 is a cross-sectional view of a conventional liquid crystal display device, and its basic operation will be explained next. That is, the FET element (11
) and the liquid crystal display section (L2) are connected in series by an aluminum film (1G), and a voltage sufficient to drive the liquid crystal is applied between both ends. At this time, when a gate voltage is applied to the gate electrode (2) of the FET element to open the gate, an amorphous silicon film ( The resistance of 6) decreases, voltage is applied to the liquid crystal display section, and the liquid crystal (8) is driven. Conversely, if the gate is closed, the liquid crystal will not be driven, and the driving of the liquid crystal can be controlled by the gate voltage t6 of the attached FET element. For this reason, even if individual liquid crystal display devices are assembled to create a large area, the F.
By simply scanning the gate I-voltage of the ET element, each l can control the drive of a high display device, allowing a large screen display. Note that (8) (yo liquid crystal 5) and (1?) are protective films. [Problems to be solved by the invention] However, liquid crystal display devices using single crystal silicon plates or polycrystalline silicon plates have material limitations. It is difficult to enlarge the area,
It is also very expensive. Although a liquid crystal display device using an amorphous silicon thin film as shown in FIG. 4 is relatively easy to increase in area and inexpensive, it has the disadvantage that it is difficult to obtain a film with uniformity and excellent characteristics. Furthermore, there is a problem in that the manufacturing process is very complicated and it is difficult to create a liquid crystal display device, regardless of whether the above-mentioned single crystal silicon, polycrystal silicon, or amorphous silicon is used. The present invention was made to solve the above-mentioned problems, and an object of the present invention is to easily increase the area of a liquid crystal display device and to obtain a liquid crystal display device having uniform and excellent performance. In addition, it is possible to form a semiconductor layer by both electrolytic polymerization method and chemical polymerization method, and FET elements can be easily manufactured.
Liquid crystal display devices can also be manufactured inexpensively and easily. [Means for Solving the Problems] The liquid crystal display device of the present invention includes a field effect transistor in which the conductivity of the semiconductor layer, which is a current path between a source electrode and a drain electrode, is controlled by a gate electrode. A driving section provided with a field effect transistor made of a π-conjugated polymer having a five-membered ring, and a liquid crystal display section connected in series with either one of the source electrode and the drain electrode, and the gate voltage The liquid crystal display section is controlled by changing the . [Function] μ- having a complex five-membered ring of the FET element in this invention
Conjugated polymer membranes can be easily produced by electrolytic polymerization or chemical oxidative polymerization. Therefore, a homogeneous semiconductor layer (polymer film) can be easily manufactured, and a liquid crystal display device can easily be made larger in area. In addition, single-crystal Noricon uses inexpensive organic compounds. A liquid crystal display device can be made cheaper than when polycrystalline silicon or amorphous silicon is used. Furthermore, it is possible to provide excellent performance equivalent to or better than that using an amorphous silicon thin film. [Embodiment] FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention, in which (1) is a substrate, (2) is a gate electrode provided on one side of the substrate (1), and ( 3) is an insulating film provided on the substrate (1) and gate electrode (2), (4) is a source electrode provided on the insulating film (3), and (5) is also provided on the insulating film (3). The drain electrode (6) is provided separately from the source electrode (4), and the insulating film (3) and the source electrode (
4) and the drain electrode (5), and is a semiconductor layer made of a π-conjugated polymer having a five-membered hetero ring that is in ohmic contact with the source electrode (4) and the drain electrode (5), respectively. (2) to 6) above are FETs in liquid crystal display devices.
This is the element part (■). In the figure, (7) is the electrode connected to the drain electrode (5) of the FET element (++), (8) is the liquid crystal display layer, and (9) is the electrode connected to the drain electrode (5) of the FET element (++).
) is a transparent electrode, and (10) is a glass plate with a polarizing plate. The electrode (7) and the electrode (9) are subjected to alignment treatment. This is the liquid crystal display section (+2) of the above (7) to C0) (Yo liquid crystal display device). Here, the following materials are used as the materials used in this invention. Glass is used as the substrate (1). Although generally used, a polymer film such as a polyester film can also be used.In the FET element part C11) of the liquid crystal display device, the gate electrode (2) can be made of gold, platinum, chromium, palladium, aluminum, etc. , gold E such as indium, tin oxide, indium oxide, indium/tin oxide (TO) 3
Although it is common to use these materials, two or more of these materials may be used in combination. Furthermore, p-type silicon, n-type silicon, or an organic polymer having conductivity may be used. When using these, the substrate (11) can be omitted. As the insulating film (3), silicon oxide (SiO2) is generally used, but silicon nitride or aluminum oxide may also be used. Insulating polymers such as polyvinylcarbubble, polyphenylene sulfide, and polyparaxylene may also be used.Of course, two or more of these materials may be used in combination.A complex five-membered material forming a semiconductor layer As a π-military service polymer having a ring, -i formula \・ and -〇C, H, one type of group, ・(, 1? number
Horn M4 and general formula only 1. ? 1 \ ,・' )・-Slim Ha/,・ (2) −′・ ′°″l′u, 8juR, 1, f・-1・-01゛・
The one shown as \ is used, and two or more of these can also be used together. π-conjugated polymer with a five-membered heterocyclic ring

[i itself usually from an insulator, but with a suitable electron acceptor, e.g.
f over Pg X fi! It can be made into a p-type semiconductor by doping with 4-on, tetrafluoroborate inine, sulfonate ion, etc., and its conductivity can be controlled over a wide range from the insulator region to the gold region.
Toga Te, %, :, ,,,”, Nomi, jjft Example I
C), 5 L) A small amount of doping is applied to the π-conjugated polymer that FKs the pentacyclic ring.
'! A 4° north lightning pole +41 which imparts semiconducting properties to I, l', and m is preferably used. 3 and F L/in electrode (5
) has a complex five-membered ring forming a semiconductor layer.
- Conjugated polymers (metals with a large work function due to ohmic contact with (h) are preferred, such as gold and platinum. Chromium, palladium, etc. are generally used, but of course they are not limited to these. (Yonai 2. Or as the case may be)
For this reason, tin oxide, indium oxide, indium oxide, tin oxide (ITO), or an organic molecule having conductivity may be used. , the thin film of the above key conjugated polymer is applied to the gate electrode (rule (2)). (7) The intermediate member constructed by 4 is formed by an electrochemical polymerization method (electrolytic polymerization method) or a chemical oxidation polymerization method (chemical oxidation polymerization method) by a method C1. . For example, in order to form a π-conjugated polymer film having 11 replicating rings using the electrolytic polymerization method, monomers and supporting electrolytes corresponding to π-conjugated polymers having 11 complex rings and supporting electrolytes are used. is dissolved in an organic solvent or water to form a reaction solution, at least one of the bipedal source electrode (4) and the drain electrode (5) is used as a working electrode, and a current is applied between it and a counter electrode such as platinum. to cause a polymerization reaction to precipitate a π-conjugated polymer having a desired replication source near the working electrode, and thoroughly wash the deposited π-conjugated polymer film having a five-membered heterocyclic ring. After that, use a method of drying in a nitrogen atmosphere.In this case, the precipitation (the π-conjugated polymer membrane in which the replication source is a ring is the supporting electrolyte during the reaction)-
It is doped with ions to become a p-type organic semiconductor, and since the distance between the source electrode (4) and drain electrode (5) is sufficiently short, the insulating film between the two electrodes is also a π-conjugated polymer having boron atoms. Covered by a molecular film, both electrodes are electrically connected by a p-type organic semiconductor film. Further, after electrolytic polymerization, the p-type organic semiconductor film can control the doping structure to change the conductivity to a value suitable for an FET element. Here, the organic solvent (i.e., a supporting electrolyte and a solvent capable of dissolving the monomers mentioned above), such as acetate, tolyl, nitrobegonocene, bensonitol, dichloromethane, etc. N, N-Didadi 4 formamide (1) MF)
DMSO+3. :; Nochloromeke 2, Tetrahuman L-
Polar solvents such as ethanol, ethyl alcohol, and ethyl alcohol are preferably used as a medium or as a mixed solvent of two or more of them. It is possible to use 7iI. Supporting electrolyte 1
Electrolysis is a substance that does not undergo oxidation or reduction reactions itself and can impart conductivity to a solution by dissolving it in a solvent. Chloric acid-tetraalkyluane kL * '7' tria/1. Killasimonium Engineering) Rahul I Robo p,
, ) salt, tetraalkylammonium hexafluorophos 7er r-1f=, t+・raalkylammonium rose 1-luenosul 4, nate salt, J=S and hydroxide I・Liu, etc. are used, but of course In order to form a π-conjugated polymer film having a bipedal complex five-shell ring by a tertiary chemical oxidation polymerization method, it is possible to use two types of J-S in combination with deionized water or an organic solvent. A predetermined amount of an oxidizing agent is dissolved as an initiator in a mixed solvent or an organic solvent, and a solution is sufficiently deoxidized, and then a monomer corresponding to the π-conjugated polymer having the above five-membered heterocyclic ring is added to the solution. A predetermined amount of is added to polymerize the monomer. At this time, the gate electrode (2), the insulating film (3), the source electrode (4)
), the drain electrode (5), and the substrate (1) on which the electrode (7) has been provided, that is, the intermediate member, is immersed in the FET element portion (or in some cases, the entire part) in this solution for at least 5 minutes, A polymer film (6) of a π-conjugated polymer having a five-membered hetero ring is formed on the FET element portion (11). At this time, a small amount of oxidizing agent or anion The p-type π is doped into the polymer film (6) and then has a desired conductivity by using a suitable doping agent or electrochemical doping if necessary.
- It can also be a conjugated polymer membrane. The substrate (1) may be immersed in the solution immediately or simultaneously after adding the monomer to the solution. This method has excellent film thickness controllability and film uniformity, and it is easy to obtain a conductivity suitable for an FET at the same time as film formation. Here, as the initiator, ferric chloride, potassium ferricyanide, etc. are used, but of course the initiator is not limited to these. Any oxidizing agent in which the redox potential of the initiator is greater than the polymerization initiation potential of the monomer may be used. FE in the liquid crystal display section (12) of the liquid crystal display device
The drain electrode (5) of the T element and the short-circuited electrode (7) can be made of any metal as long as it has sufficient conductivity and is insoluble in liquid crystal, or metals such as gold-platinum, chromium, aluminum, or tin oxide. metal, indium oxide, i'/rheum/tin oxide (
A transparent electrode such as ITO), p-type silicon or n-type silicon, or an organic polymer having a conductivity ratio may be used. Of course, two or more of these materials may be used in combination. As the electrode (9) on the glass plate α0), it is common to use a transparent electrode made of tin oxide, indium oxide, indium-tin oxide (ITO), or the like. Further, a conductive organic polymer having appropriate transparency may be used. Alternatively, two or more of these materials may be used in combination. However, these electrodes (7) and (9) have 51
It is necessary to perform orientation treatment such as oblique vapor deposition or rubbing of 02. A liquid crystal such as a guest-host type liquid crystal, a TN type liquid crystal, or a smectic C-phase liquid crystal is used for the liquid crystal layer (8), and the substrate (1) is made of glass and the electrodes (7)
When using transparent electrodes, the contrast ratio can be increased by attaching a polarizing plate to the substrate (1). The polarizing plate of the glass plate with polarizing plate (10) may be any type as long as it polarizes light. The FET element (U
), the operating mechanism is largely unknown, but at the interface between the π-conjugated polymer film (6) and the insulating film (3), The width of the depletion layer formed on the molecular film (6) side is controlled by the voltage applied between the gate electrode (2) and the source electrode (4), and the effective hole channel cross section changes. It is considered that the current flowing between (4) and the drain electrode (5) changes. At this time, if the π-conjugated polymer film (6) having a five-membered complex ring has only p-type semiconductivity with low conductivity, the electrode (2) may be other than a metal electrode. Even if materials with high conductivity such as p-type silicon, n-type silicon, or conductive organic polymers are used, it is difficult to obtain a π-conjugated polymer film with a five-membered heterocyclic ring (6
) is thought to form a depletion layer with a sufficiently large width to produce an electrolytic effect. In the liquid crystal display device of the present invention, the FET element (1
1) and the liquid crystal display section (I2) are connected in series. A negative voltage is applied to the transparent electrode (9) using the source electrode (4) as a reference, and when a negative voltage is applied to the data electrode (2), the liquid crystal is turned on. As mentioned earlier, this is because the resistance between the source and drain electrodes of the FET element is
This is thought to be due to the decrease due to the application of a negative voltage to the electrodes and the voltage applied to the liquid crystal display section. On the other hand, if the gate voltage is turned off while applying a negative voltage to the transparent electrode (9) with respect to the source electrode, the liquid crystal will not light up. It is thought that this is because the resistance between the source and drain electrodes of the LtFET element is: 1''≦Y, and no voltage is applied to the liquid crystal display depending on the voltage range. The liquid crystal display device of the invention is equipped with a 7iS/near FET element. By varying the gate voltage of the FET element, the driving of the liquid crystal display section can be controlled. In addition, in FIG. -electrode (2)
However, conversely, a π-conjugated polymer film having a >a-membered ring is provided on the substrate, and a source electrode and a train electrode separated from the source electrode are provided thereon. An insulating film may be interposed between the source electrode and the do-L-ino electrode to provide a de-L-electrode. Alternatively, a gate electrode (2) is provided on the substrate (1), an insulating film is interposed therebetween, a π-conjugated polymer film having complex redundancy ζ is provided on the substrate (1), and a source electrode and a A do/in electrode may be provided separately from this source electrode. Alternatively, a source electrode and a train electrode separated from the source electrode are provided on the substrate (1), a π-conjugated polymer film having a five-membered complex ring is provided on this, and an insulating film is interposed between the train electrode and the train electrode. 1- An electrode may be provided. Furthermore, in the above embodiment, the FET element and the liquid crystal display section were fabricated on the same substrate, but they were fabricated on separate substrates.
[You may also use it by connecting it after making it. Hereinafter, this invention will be explained in detail with reference to Examples, but of course, the invention is not limited to the Examples.
40 mm) was thermally oxidized to form an oxide film (S, 0° film) with a thickness of 3 (100 mm) on both sides.The source electrode (4) and drain electrode (5) in Fig. 1 were formed on this surface. And metal electrodes to become electrodes (7) (fully covered chromium electrodes; chromium 2 (10 people) and gold 3 (10 people) were provided by vacuum evaporation method. Here, both the source electrode and the drain electrode have an effective area of 2. The 4 seagulls are separated by 6pff1 width.Also, the electrode (7) has an effective area of 17mm.
+X 19+nm unit. Hereinafter, this substrate will be referred to as a liquid crystal display device substrate. Dissolve 0.55 g of tetraethylammonium perchlorate as an electrolyte and 0.27 g of monomer L42.2'-dithiophene in 75 ml of heptonitrile that has been distilled twice with the addition of niline pentoxide, and leave to maintain high purity for over 30 minutes. Deoxidize by venting gas:. This is the FET element part (the part corresponding to (11) in Figure 1) of the liquid crystal display device board.
of? 2 L, source 73 Using the electrode 1 and the drain electrode as working electrodes, a constant current electrolysis method is applied to the electrode, ]OOμA/cm'
Node current was applied for 8 minutes. This operation (from this
A thin film of polythiol is formed on the insulating film between the source electrode, the train electrode, and the source and drain. After this, the potential of the gold electrode is changed to a saturated calomel layer. 2 to -1-0,20V to the electrode
The polythiophene film was electrochemically doped for 70 minutes, and the conductivity of the polythiophene film was made suitable for an FET device. Next, assemble this 1 modified display neck board.
The sample was taken out from the -21-lyl solution, pre-cleaned twice with high-purity acetonitrile, and then blown with high-purity nitrogen gas, and then placed in a ten-footer and vacuum-dried. By the above operations, the back FET component part of the liquid crystal display device was completed. Next, the liquid crystal display board and the glass plate 1- facing it are
, O□ was vapor-deposited ↑1 and alignment treatment was performed to cause alignment of the liquid crystal.3, and a 10 μm thick triester film was placed between the liquid crystal display device substrate and the glass plate facing it, so that the liquid crystal display part had an opening. 1. Leave only a portion so that it forms a section, and sandwich it in, leaving only a portion of the area around it. and sealed with epoxy resin. Then, from this unsealed part, the guest/host liquid crystal (Me
Inject TK knee (product name: ZLi1841) manufactured by RCK Corporation and seal with epoxy resin.1. A polarizing plate was pasted onto the glass electrode to complete the liquid crystal display part of the liquid crystal display device. Finally, remove part of S and 02 on the back side of the liquid crystal display board (
1. Oc+a
1. Oc+n), a silver base and lead wires were attached to this to complete a liquid crystal display device according to an embodiment of the present invention.t:9. This was designated as tI1 product list non-display device sample). Example 2 Glass base 1i (25mm x 40M) with thickness 1, Om
) on a metal electrode (gold-coated chromium electrode; chromium 2 (10
Gold and gold 3 (10 people) were deposited by vacuum evaporation method and used as the gate electrode (rT effect gate electrode area is 2 m x 5 μm).
m). 3. Further, a silicon oxide film is formed on the substrate 1 and the electrode. (This was formed by the CVD method to a thickness of 100 mm and used as an insulating film.Furthermore, a metal electrode (gold coated chromium electrode; chromium 2 (10 mm)
Gold and gold 3 (10 people) were deposited at two locations across the gate electrode by vacuum evaporation, and these were used as the source and drain electrodes (the effective area for both was 2 mm x 4 m).
m). Furthermore, a metal electrode (gold coated chromium electrode; chromium 2 (10
Gold 3 (10 people, effective area 19 mm x 17 mm) was provided by vacuum evaporation. Hereinafter, this glass substrate will be referred to as a liquid crystal display device. 1 (10 mj of ferric chloride (Fee13-6) in pure water
High-purity nitrogen gas was bubbled through the solution for 30 minutes in which H, 0, 2, 7 g) was dissolved, and then two pairs of source electrodes, drain electrodes, insulating films, gate electrodes, and electrodes that would become the liquid crystal display section were installed. The liquid crystal display substrate was immersed. Then, 1 ml of N-methylpyrrole was added to this solution while continuing to supply high-purity nitrogen gas. As soon as N-methylpyrrole is added, a chemical oxidative polymerization reaction begins, and a Bo'J (N-methylpyrrole) film begins to form on the liquid crystal display substrate. After 60 minutes, the liquid crystal display device substrate was taken out of the solution, washed with water and ethanol, and then vacuum-dried for 3 hours. Through the above operations, a portion of the liquid crystal display device corresponding to the FET element was completed. Next, as shown in Example 1, a 310° diagonal vapor deposition was performed on the liquid crystal display substrate and the glass plate facing it so that alignment of the liquid crystal occurred. Then, a 10 μm thick Mylar film is sandwiched between the liquid crystal display device substrate and the glass plate facing it, leaving only a part of the film open so that the liquid crystal display part becomes an opening. It was sealed with. And from this unreached part TN
A mixture of 0.5% by weight of cholesteryl nonanoate was injected into a type liquid crystal (product name ZL11565 manufactured by Merck) and sealed with an epoxy resin. A polarizing plate was then attached to the glass plate to complete the liquid crystal display. This was designated as a liquid crystal display sample (Irl). Figure 2 shows the source-drain current (μA) when the voltage (V) of the FET element in the single crystal display sample (II) was changed. -A characteristic diagram showing source-drain voltage (V) characteristics, where the horizontal axis is the source-drain voltage (V)
, the vertical axis indicates the source-drain current (μA). or,
The FET element in the liquid crystal display sample (I) also exhibited characteristics similar to those shown in FIG. In other words, when the gate voltage of the FET element is set to Ov, even if a voltage is applied between the source electrode and the drain electrode,
Only a small drain current flows, but the more negative the gate voltage, the larger the source-drain current flows. Since this FET element and the liquid crystal display section are connected in series, a voltage sufficient to drive the liquid crystal is applied between the transparent electrode on the glass plate of the liquid crystal display section and the source electrode of the FET element. When a negative voltage was applied to the gate electrode, a voltage was applied to the liquid crystal display section, and the liquid crystal was aligned and driven. However, when the gate voltage was set to Ov, no voltage was applied to the liquid crystal display section, and the driving of the liquid crystal stopped. In other words, an F-type film whose semiconductor layer is a π-conjugated polymer film having a five-membered heterocyclic ring and which is attached to drive a liquid crystal.
It was possible to control it with an ET element. In addition, in terms of stability, the liquid crystal display device of the present invention remained stable even after one month or more, and three liquid crystal display devices were manufactured. In addition, in Examples 1 and 2, only one FET element and one liquid crystal display part were each produced to form a liquid crystal display device.
It is possible to use a similar method to fabricate a plurality of FET elements and a liquid crystal display section to form a liquid crystal display device. Tat
! In that case, in Embodiment 1, a method that combines photoresist Baku 2 fabrication and ion implantation is used on the S1 plate to provide appropriate conductivity only to the necessary portions and electrically connect each device. Possible methods include separation. Furthermore, it is also possible to fabricate the FET element section and the liquid crystal display section on separate substrates and then connect them to form a single device. Note that the patterning during manufacturing of the liquid crystal display device can be done by Tsuho's semiconductor manufacturing technology using photolithography technology. [Effects of the Invention] As explained above, the present invention improves the conductivity of the semiconductor layer, which is a current path between the source Ts 1% and the drain current.
, the electric field thin section controlled by the gate electrode I! 1-Ranojis! 2. A drive unit provided with a field effect transistor whose bipedal semiconductor layer is a π-conjugated polymer having a reproduced five-membered ring, and either a bipedal source electrode or a doji electrode. The liquid crystal display section L can be controlled by 1ν by changing the voltage of the gate 1. By using a liquid crystal display device, it is possible to easily increase the area and obtain a liquid crystal display device having homogeneous and excellent performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.
Figure 2 (source/drain electrodes (μm) □ source/drain electrodes (V) ffE diagram for each of the FF and T elements according to the present invention at -1-voltage; Figure 3 shows the ffE diagram of the conventional Figure 4 is a cross-sectional view of a conventional liquid crystal display device. In the figure, (2) is a gate electrode, (3) is an insulating film, and (4) is a gate electrode.
) is the source electrode, (5) is the drain electrode, (6) is the π-conjugated polymer film having a five-membered complex ring forming the semiconductor layer, (7) is the main character i of the one-night product display section, ( 9) is a counter transparent electrode, and (8) is a liquid crystal layer. In each figure, the same reference numerals represent the same or corresponding parts.

Claims (10)

[Claims] (1) An electric field in which the semiconductor layer of a field effect transistor is a π-conjugated polymer having a complex five-membered ring, in which the conductivity of the semiconductor layer, which is a current path between the source electrode and the drain electrode, is controlled by the gate electrode. comprising a driving section provided with an effect type transistor, and a liquid crystal display section connected in series with either one of the source electrode and the drain electrode,
A liquid crystal display device that controls the liquid crystal display section by changing the gate voltage. (2) A π-conjugated polymer having a five-membered heterocyclic ring has a general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, X is one of S and O atoms, R_1 and R_2 are -H, -CH_3, -OCH_3, -C_2
One of the groups H_5 and -OC_2H_5, n is an integer. ) The liquid crystal display device according to claim 1, which is represented by: (3) The liquid crystal display device according to claim 2, wherein the π-conjugated polymer having a five-membered hetero ring is one of polythiophene and poly(3-methylthiophene). (4) A π-conjugated polymer having a five-membered heterocyclic ring has a general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R_1 and R_2 are -H, -CH_3, O
One of the groups CH_3, -C_2H_5, and -OC_2H_5, R_3 is -CH_3, -C_2H_5, C
_3H_7, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ - One of NO_2, n is an integer. ) The liquid crystal display device according to claim 1, which is represented by: (5) A liquid crystal display device according to any one of claims 1 to 4, using a field effect transistor whose gate electrode is composed of either p-type silicon or n-type silicon. (6) A liquid crystal display device according to any one of claims 1 to 5, characterized in that a field effect transistor and a liquid crystal display section are provided on the same substrate. (7) A liquid crystal display device according to any one of claims 1 to 5, wherein the field effect transistor and the liquid crystal display section are provided on different substrates. (8) A liquid crystal display device according to any one of claims 1 to 7, characterized in that a nematic phase liquid crystal is used. (9) A liquid crystal display device according to any one of claims 1 to 7, characterized in that a smectic phase liquid crystal is used. (10) A liquid crystal display device according to any one of claims 1 to 7, which uses a guest-host type liquid crystal display element.