JP4444694B2 - Liquid crystal display element - Google Patents

Description

The present invention relates to a liquid crystal display device of Akuteibu drive system.

A liquid crystal display element that displays white light by using light scattering and displays a light transmission image by applying a voltage can be displayed in the same way as paper. Development is underway.
Examples of such a liquid crystal display element include a dynamic scattering mode method, a polymer dispersion type liquid crystal method, a smectic liquid crystal method using a focal conic phase, or a cholesteric-nematic phase transition method. In these systems, the liquid crystal can be driven to control the light scattering state and the transmission state. Since the light scattering state appears white, by disposing the light absorption layer on the back side of the liquid crystal layer, for example, two-color display of white and black can be performed.
Since these liquid crystal display elements do not necessarily have to be formed on a crystal substrate, a light and flexible display element can be produced. Further, since it is not necessary to use a polarizing plate or a backlight, a display element with low power consumption and low cost can be realized.

  In the active drive type liquid crystal display element, a semiconductor device including a thin film transistor (TFT) made of an inorganic material such as amorphous silicon or polysilicon has been used as a drive circuit. However, since a thin film transistor for a drive circuit using an inorganic material is formed on a crystal substrate, it is difficult to increase the size, and the thin film transistor is manufactured through heat treatment, lithography, etching, or the like reaching nearly 1000 degrees. The manufacturing process is complicated and it is difficult to reduce the cost. For this reason, an attempt has been made to configure a drive circuit for a liquid crystal display element with a semiconductor device made of an organic transistor that does not need to be formed on a crystal substrate and has a simple manufacturing process.

  For example, an example in which a polymer dispersed liquid crystal display element is driven by an organic transistor using pentacene as a semiconductor material to perform display of 2 × 3 pixels (see Non-Patent Document 1), a polymer dispersed liquid crystal display element Have been reported to display 64 × 64 pixels by driving an organic transistor using polychenylene vinylene as a semiconductor material (see Non-Patent Document 2).

  In addition, high molecular weight materials have lower carrier mobility than low molecular weight materials, but have high solvent solubility. Therefore, taking advantage of the fact that they can be produced by a printing process, condensed ring organic materials can be used as semiconductor materials. (See Patent Document 1).

  On the other hand, for example, since the present reflectance in the light scattering state of the polymer dispersion type liquid crystal display element is low, there is a problem that the contrast is poor when white display and black display are performed.

Therefore, a reflective layer having a refractive index smaller by 0.2 or more than that of the substrate is laminated on the back side of the substrate (see Patent Document 2), and a plurality of reflective layers having different refractive indexes are sequentially arranged toward the back side. Some layers are laminated so that the refractive index becomes small, and a part of light transmitted through the liquid crystal layer in a light scattering state is reflected to make white display brighter (see Patent Document 3).
In addition, there is a liquid crystal display layer in which a transflective layer and a light absorption layer are provided on the back side, and a low refractive layer is provided on the back side of the back side substrate (see Patent Document 4).
JP-A-11-195790 Japanese Patent No. 2842172 JP 7-104286 A JP-A-7-56157 APPLIED PHYSICS LETTERS, VOL.78, P3592 (2001) (P.MACH, SJRODRIGUEZ, R.NORTRUP, P.WILTZIUS, JAROGERS) NATURE, VOL.414, P599 (2001) (HEHUITEMA, GHGELINCK, JBPHVAN DER PUTTEN, KEKUIJK, CMHART, E.CANTATORE, PTHERWIG, AJJMVAN BREEMEN, DMDE LEEUW)

  However, the method disclosed in the patent document forms a low refractive index gas layer in which air or inert gas is inserted using a spacer, and the refractive index of the relatively high refractive index substrate and the low refractive index gas layer. The light transmitted through the liquid crystal layer due to the difference is reflected at the interface between them to obtain a predetermined brightness. Therefore, there is a problem that a process for forming a low refractive index gas layer or the like is newly increased, resulting in an increase in cost. Conventionally, there is a demand for development relating to a method for forming a low-cost liquid crystal display element by integrating a liquid crystal element and its drive circuit using a simple process.

In view of the above circumstances, in the present invention, a polymer liquid crystal layer capable of high-contrast display without adding a special process and an organic transistor constituting a driving circuit for the liquid crystal layer are formed on the same substrate. A liquid crystal display device is provided.

In the liquid crystal display element of the present invention that achieves the above object, a liquid crystal layer and a drive circuit are stacked between opposing substrates, and the liquid crystal layer transmits light according to the presence or absence of an electric field applied from the drive circuit. A liquid crystal display element exhibiting a state or a scattering state,
The drive circuit state, and are not constructed by an organic transistor having a gate insulating layer having a smaller refractive index than the liquid crystal layer in the transmission state of light,
The gate insulating layer is at least micropores, mesopores, and wherein Rukoto such a porous body that contains any one size pores of the macropores.

  Thus, the refractive index of the gate insulating layer is configured to be smaller than that of the liquid crystal layer, and the gate insulating layer also functions as a low refractive index layer of the liquid crystal display element, so that the light scattering state liquid crystal layer is transmitted. Some light is reflected at the interface of the gate insulating layer, enabling a brighter white display.

Further, by constituting the gate insulating layer by the porous body, there is little leakage current, it is possible to obtain an insulating film, even subjected to any stress due to bending and twisting, hardly peeled stress is absorbed from the substrate crystal A display element can be formed.

According to the liquid crystal display element of the present invention, a thin film transistor and a liquid crystal layer made of an organic semiconductor are formed on a common substrate, and the gate insulating layer of the thin film transistor also functions as a low refractive index layer of the liquid crystal display element. Simplification and cost reduction. In addition, by using a porous material for the gate insulating layer, an insulating film with almost no leakage current can be obtained, and even when stress due to bending or twisting is applied, peeling of the liquid crystal display element from the substrate is prevented. The

As a result of intensive studies to solve the above problems, the present inventors have made it possible to display a high contrast on the same substrate by utilizing the gate insulating layer of the organic transistor as a low refractive index layer of the liquid crystal display element. The present inventors have obtained the knowledge that the liquid crystal layer to be formed and the organic transistor array constituting the drive circuit can be integrally formed by a simple process, and the present invention has been completed.
Hereinafter, embodiments of the liquid crystal display element of the present invention, the organic semiconductor device of the present invention constituting the drive circuit thereof, and the method of manufacturing the organic semiconductor device will be described.
(First embodiment)
FIG. 1 is a schematic cross-sectional view of a liquid crystal display element showing a first embodiment of a liquid crystal display element, an organic semiconductor device, and a method for manufacturing the organic semiconductor device of the present invention.

  In the liquid crystal display element of the first embodiment shown in FIG. 1, in addition to the liquid crystal layer, one field effect organic transistor which is a driving circuit for the liquid crystal layer and is a component of the semiconductor device of the present invention is shown. Yes.

    The liquid crystal display element 30 according to the first embodiment includes a film substrate 1 and a substrate 2 that are opposed to each other, and a light transmission state and a light scattering state that are stacked between the opposing substrates 1 and 2 by applying an electric field. The liquid crystal layer 3, the organic transistor 10 constituting the drive circuit for driving the liquid crystal layer, and the light absorption layer 4 are configured.

  The organic transistor 10 is a field effect transistor using a semiconductor made of an organic compound, and includes a gate electrode 11, a source electrode 12, a drain electrode 13, an organic semiconductor layer 14, and a gate insulating layer 15 that forms a channel. It is configured.

  An upper electrode (scanning electrode) 5 that applies an electric field to the liquid crystal layer 3 on the viewing side A on which an image is displayed on the liquid crystal display element 30 is laminated on the inner surface of the film substrate 1. In addition, the lower electrode (signal electrode) on the back side B also serves as the drain electrodes 13 of the plurality of organic transistors 10 formed on the substrate 2.

  The liquid crystal layer 3 is made of polymer-dispersed liquid crystal. When an electric field is applied, the liquid crystal layer 3 is in a light transmission state. When the electric field is not applied, the liquid crystal layer 3 is in a light scattering state. . Details will be described later.

  The scanning electrode 5 sandwiching the liquid crystal layer 3 is preferably made of a transparent material, and a plurality of scanning electrodes 5 are formed on the inner surface of the film substrate 1. In addition, the signal electrode 13 which is also used as the drain electrode 13 is disposed so as to be orthogonal to the scanning electrode 5. These upper electrode 5 and lower electrode 13 form a 64 × 64 matrix, for example.

  The drive circuit constituted by the organic transistor 10 corresponds to the embodiment of the semiconductor device of the present invention, and corresponds to the matrix formed by the scanning electrode 5 and the signal electrode 13 sandwiching the liquid crystal layer 3, and the organic transistor 10. And a capacitor connected in series to the organic transistor 10, and the scanning electrode 5 is connected to the gate electrode 11 of the organic transistor 10, and the drain electrode 13 is connected to each signal electrode. Is also used.

  As described above, the drain electrode 13 of the organic transistor 10 also serves as a signal electrode that forms a matrix with the scanning electrode 5, and the drain electrodes 13 of the organic transistor 10 that are connected to each other are integrally formed. Can be reduced.

  An insulating material having a refractive index smaller than that of the liquid crystal layer 3 in a light transmission state is used for the gate insulating layer 15 of the present embodiment.

  The light absorption layer 4 absorbs, for example, color light in a specific wavelength region of natural light and reflects color light in the remaining wavelength region. For example, when a light absorption layer that absorbs yellow is used, the liquid crystal display element displays blue, and natural light is displayed. When a light absorption layer that absorbs all is used, the liquid crystal display element displays black.

  Therefore, when a charge is accumulated in the capacitor of each memory cell of the drive circuit, a voltage is applied to the pixel of the liquid crystal layer corresponding to each memory cell, and the pixel is in a light transmission state, the pixel is set to “black”. When “display” is desired, a voltage is applied to the scanning electrode 5 and a voltage is applied to the signal electrode 13 in a state where the voltage is applied to the gate electrode 11. Then, a current flows from the drain electrode 13 of the organic transistor 10 to the source electrode 12 and the capacitor is charged, so that the corresponding pixel of the liquid crystal layer 3 enters a light transmission state, and the transmitted light is absorbed by the light absorption layer 4. Is black.

  Further, if the voltage applied to the scanning electrode 5 is removed and the voltage applied to the signal electrode 13 is removed, the charge of the capacitor is discharged, so that the corresponding pixel of the liquid crystal layer 3 is in a light scattering state and white display is performed. .

  Since the liquid crystal display element 30 of the present embodiment is configured such that the refractive index of the gate insulating layer 15 is smaller than that of the liquid crystal layer 3, a part of the light transmitted through the liquid crystal layer 3 in the light scattering state. Since light is reflected by the gate insulating layer 15, a brighter white display can be achieved. In the light transmission state, part of the light is reflected, but in the case of black display, most of the light is absorbed by the light absorption layer 4. Therefore, the contrast when displaying in black and white can be improved.

  2A and 2B are diagrams showing a liquid crystal layer used in the liquid crystal display element of this embodiment, and FIGS. 2C and 2D are diagrams showing states of liquid crystal droplets in the liquid crystal layer. It is.

  As shown in FIG. 2, a polymer dispersed liquid crystal (hereinafter abbreviated as PDLC “Polymer Dispersed Liquid Crystal”) is used for the liquid crystal layer 3 of the present embodiment.

  PDLC is generally in a state in which liquid crystals are dispersed in a matrix polymer. Then, the structure of the polymer changes depending on the concentration of the liquid crystal, the liquid crystal becomes droplet-like liquid crystal droplets, or the polymer becomes a network, and regions having different refractive indexes are formed. In the present embodiment, as shown in the figure, the liquid crystal 3b is a liquid crystal droplet 3a.

  The liquid crystal 3b is a rod-like molecule having refractive index anisotropy, and the refractive index changes depending on the alignment state.

  Now, as shown in FIG. 2D, if the refractive index in the minor axis direction of the liquid crystal 3b is the ordinary refractive index no and the refractive index in the major axis direction is the extraordinary refractive index ne, the liquid crystal 3b has no <ne. When a positive liquid crystal having a relationship is used, the refractive index np of the polymer material becomes substantially equal to no.

  When no electric field is applied to the liquid crystal layer 3, as shown in FIGS. 2A and 2C, the liquid crystal 3b is randomly oriented, the liquid crystal layer 3 is in a light scattering state, and an average refractive index ( ne to no) is different from the refractive index np of the polymer 8. For this reason, the average refractive index of the liquid crystal takes a value between np and no, and the difference from np becomes large, so that the light incident on the liquid crystal layer is repeatedly refracted at the interface between the liquid crystal droplet and the polymer material and scattered. And since it becomes an opaque white turbid state, a liquid crystal display element becomes white display.

  On the other hand, when an electric field is applied to the liquid crystal layer 3, the orientation direction of the liquid crystal 3b in the liquid crystal droplet 3a changes as shown in FIGS. In the case of vertical alignment, no and np are substantially equal, so that the light incident on the liquid crystal layer 3 is in a transmission state. When this transmitted light is absorbed by the absorption layer 4 on the bottom surface, the liquid crystal display element 30 displays black. Further, by repeating (switching) this light scattering and transmission state, it is possible to perform color display by controlling the transmission amount of each color light.

  3A and 3B are diagrams illustrating the refractive indexes of various liquid crystal materials.

  In FIGS. 3A and 3B, no is an ordinary refractive index in the uniaxial direction, ne is an extraordinary refractive index in the major axis direction, and Δn is a refractive index difference, and there is no description of the measurement wavelength. All were measured at 633 nm.

  Here, the refractive index was measured by entering light having a wavelength of 633 or 589 nm using an Abbe refractometer. Abbe's refractometer can measure a refractive index in the range of 1.3300 to 1.700 with an accuracy of 0.0002 (at 589 nm). By using a refractometer, it is possible to measure from 1.116 to 2.350.

  As is apparent from the figure, the ordinary refractive index no of most liquid crystal materials is around 1.5, the extraordinary refractive index ne is around 1.7, and the refractive index np of the polymer material that becomes the matrix of the liquid crystal material. Is approximately 1.5.

  On the other hand, since the fluorine insulating polymer having a refractive index of about 1.2 to 1.4, methyl-containing polysiloxane, or the like is used for the gate insulating layer of the organic transistor of the present embodiment, the liquid crystal layer of the present embodiment. The refractive index in the light transmission state of the liquid crystal material used for (approximately 1.5) can be made. Therefore, in the light scattering state, part of the light transmitted through the liquid crystal layer and reaching the gate insulating layer is reflected at the interface to become backscattered light, and is transmitted through the substrate on the display surface side. Can be brightened.

As described above, in the liquid crystal display element of this embodiment, the gate insulating layer of the organic transistor is configured as a low refractive index layer with respect to the liquid crystal layer, and the low refractive index layer is formed simultaneously with the fabrication of the semiconductor device. A liquid crystal display element can be manufactured at low cost. In addition, as shown in FIG. 1, the connecting drain electrode of the organic transistor is integrally formed and also used as a common signal electrode constituting the pixel of the liquid crystal display element, thereby further reducing the manufacturing process. It becomes possible.
[Materials used for semiconductor devices]
Next, materials used for the semiconductor device of this embodiment will be described.

  It is desirable to use a transparent material for the drain electrode. Specifically, indium oxide / tin oxide (ITO), indium oxide / zinc oxide (IZO), a known conductive polymer whose conductivity is improved by doping, etc. For example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylenedioxythiophene and polystyrene sulfonic acid, or the like can be used. When these materials are not used, it is possible to produce a translucent electrode, for example, by producing a thin film of aluminum or gold.

  As the gate insulating layer constituting the low refractive index layer, a layer having a refractive index smaller than that of the polymer liquid crystal layer having a refractive index of about 1.5 to 1.7 is used. Specifically, a fluorine-based polymer or a methyl-containing polysiloxane material can be used.

  Incidentally, the refractive index of the fluorine-based polymer is 1.36 to 1.42, the refractive index of the methyl-containing polysiloxane is 1.38, and the refractive index of the metal oxide porous body is small. The refractive index of the polyimide porous body is about 1.32, both of which are lower than the refractive index of the light-transmitting liquid crystal layer.

  Here, the gate insulating film in the organic transistor has an original role of forming a channel of the field effect transistor in addition to the role as a low refractive index layer of the liquid crystal display element, and increases the size of the liquid crystal display element. At the same time, in order to improve the switching speed as the drive circuit, it is important how to reduce the dielectric constant by reducing the thickness of the insulating film in the absence of leakage current.

  The material of the gate electrode is not particularly limited as long as it is a conductive material. Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum , Ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium / tin oxide (ITO), indium / zinc oxide (IZO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste , Lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixed Things, magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, can be used lithium / aluminum mixtures. Alternatively, a known conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylenedioxythiophene and polystyrene sulfonic acid, or the like can be suitably used. However, the present invention is not limited to these materials, and two or more of these materials may be used in combination.

  Next, the materials used for the source electrode and the drain electrode may be different from each other or the same. However, a transparent material is used for the drain electrode which also serves as an electrode for driving the liquid crystal layer in order to transmit light to the underlying absorption layer. Specifically, as described above, indium tin oxide (ITO), indium oxide zinc oxide (IZO), known conductive polymers whose conductivity is improved by doping, such as conductive polyaniline, conductive polypyrrole. In addition, a conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, or the like can be used. For the source electrode, it is desirable to use a material capable of ohmic contact in order to reduce an energy barrier at the interface with the organic semiconductor layer. In order to obtain ohmic contact, when a P-type semiconductor having holes as carriers is used as the organic semiconductor material, it is desirable that the work function of the source and drain electrodes is larger than that of the organic semiconductor. When an N-type semiconductor whose carriers are electrons is used as the organic semiconductor material, it is desirable that the work function is smaller than the work function of the organic semiconductor. Specifically, whether or not the electrical resistance is smaller at the contact surface with the organic semiconductor layer can be determined by examining the current-voltage characteristics. In general, the following materials can be used.

  Platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), indium oxide / zinc oxide (IZO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese , Zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture , Magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture, etc. are used, in particular, platinum, gold, silver, copper, aluminum, indium, ITO, IZO and carbon are preferable. Alternatively, a known conductive polymer whose conductivity has been improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylene dioxythiophene and polystyrene sulfonic acid, or the like can be suitably used. However, the present invention is not limited to these materials, and two or more of these materials may be used in combination. It is also possible to use carbon materials such as carbon black, C60, and carbon nanotubes.

  Next, as the organic semiconductor material, a π-electron conjugated aromatic compound, a chain compound, an organic pigment, an organic silicon compound, or the like can be used. Specifically, polypyrroles such as polypyrrole, poly (N-substituted pyrrole), poly (3-substituted pyrrole), poly (3,4-disubstituted pyrrole), polythiophene, poly (3-substituted thiophene), poly ( 3,4-disubstituted thiophene), polythiophenes such as polybenzothiophene, polyisothianaphthenes such as polyisothianaphthene, polychenylene vinylenes such as polychenylene vinylene, poly (p-phenylene vinylene), etc. Poly (p-phenylene vinylene) s, polyaniline, poly (N-substituted aniline), poly (3-substituted aniline), poly (aniline) such as poly (2,3-substituted aniline), polyacetylenes such as polyacetylene, polydiacetylene, etc. Of polydiacetylenes, polyazulenes such as polyazulene, polypyrene Which polypyrenes, polycarbazoles such as polycarbazole and poly (N-substituted carbazole), polyselenophenes such as polyselenophene, polyfurans such as polyfuran and polybenzofuran, poly (p-phenylene) such as poly (p-phenylene) -Phenylene), polyindoles such as polyindole, polypyridazines such as polypyridazine, naphthacene, pentacene, hexacene, heptacene, dibenzopentacene, tetrabenzopentacene, pyrene, dibenzopyrene, chrysene, perylene, coronene, terylene, ovalene , Derivatives of polyacenes such as quaterylene and circumanthracene, and polyacenes substituted with a functional group such as an atom such as N, S or O, or a carbonyl group (triphenodioxazine, triphenodithia Emissions, hexacene-6,15-quinone, etc.), polyvinylcarbazole, polyphenylene sulfide, and polymers such as polyethylene vinyl sulfide, and the like can be used polycyclic condensate described in Patent Document 1. Further, for example, α-sexual thiophene α, ω-dihexyl-α-sexual thiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (α, which is a thiophene hexamer having the same repeating unit as those polymers. Oligomers such as 3-butoxypropyl) -α-sexithiophene and styrylbenzene derivatives can also be preferably used. Furthermore, metal phthalocyanines such as copper phthalocyanine and fluorine-substituted copper phthalocyanine described in Patent Document 3, naphthalene 1,4,5,8-tetracarboxylic acid diimide, N, N′-bis (4-trifluoromethylbenzyl) naphthalene 1 , 4,5,8-tetracarboxylic acid diimide, N, N′-bis (1H, 1H-perfluorooctyl), N, N′-bis (1H, 1H-perfluorobutyl) and N, N′-dioctylnaphthalene 1,4,5,8-tetracarboxylic acid diimide derivatives, naphthalene 2,3,6,7 tetracarboxylic acid diimides and other naphthalene tetracarboxylic acid diimides, anthracene 2,3,6,7-tetracarboxylic acid diimide, etc. Anthracene tetracarboxylic acid diimides such as fused ring tetracarboxylic acid diimides , C60, C70, C76, C78, C84, such as fullerenes, carbon nanotubes, merocyanine dyes, such as SWNT, such as dyes such as hemicyanine dyes, and the like.

Other organic semiconductor materials include tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTTF-iodine complex, TCNQ-iodine complex. Organic molecular complexes such as can also be used. Furthermore, σ conjugated polymers such as polysilane and polygerman, and organic / inorganic hybrid materials can also be used.
At least one organic semiconductor material may be selected from these, or a plurality of materials may be used. Moreover, it is not necessary to be limited to these materials.

  Furthermore, the organic semiconductor layer of the present invention includes, for example, a material having a functional group such as acrylic acid, acetamide, dimethylamino group, cyano group, carboxyl group, nitro group, benzoquinone derivative, tetracyanoethylene and tetracyanoquinodi. Materials that can accept electrons, such as methane and their derivatives, materials that have functional groups such as amino, triphenyl, alkyl, hydroxyl, alkoxy, and phenyl groups, substitutions such as phenylenediamine It contains a donor which is an electron donor such as amines, anthracene, benzoanthracene, substituted benzoanthracenes, pyrene, substituted pyrene, carbazole and its derivatives, tetrathiafulvalene and its derivatives, and so-called doping treatment. Also good.

  Here, doping means introducing an electron-donating molecule (acceptor) or an electron-donating molecule (donor) into the thin film as a dopant. Therefore, the doped thin film is a thin film containing a condensed polycyclic aromatic compound and a dopant.

As the dopant, either an acceptor or a donor can be used. As this acceptor, halogens such as Cl ₂ , Br ₂ , I ₂ , ICl, ICl ₃ , IBr and IF, Lewis acids such as PF ₅ , AsF ₅ , SbF ₅ , BF ₃ , BCl ₃ , BBr ₃ and SO ₃ , HF , HCl, HNO ₃ , H ₂ SO ₄ , HClO ₄ , FSO ₃ H, ClSO ₃ H, CF ₃ SO ₃ H and other proton acids, acetic acid, formic acid, organic acids such as amino acids, FeCl ₃ , FeOCl, TiCl ₄ , Transition metal compounds such as ZrCl ₄ , HfCl ₄ , NbF ₅ , NbCl ₅ , TaCl ₅ , MoCl ₅ , WF ₅ , WCl ₆ , UF ₆ , LnCl ₃ (lanthanoids such as Ln = La, Ce, Nd, Pr, etc.) ^{_{Cl -, Br -, I -}} , ClO 4 -, PF 6 -, AsF 5 -, SbF 6 -, BF 4 -, a sulfonate anion such as And the like can be mentioned electrolyte anions. As donors, alkali metals such as Li, Na, K, Rb, and Cs, alkaline earth metals such as Ca, Sr, and Ba, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy , Ho, Er, Yb and other rare earth metals, ammonium ions, R ₄ P ⁺ , R ₄ As ⁺ , R ₃ S ⁺ , acetylcholine, and the like.

  In addition, as a doping method of these dopants, either a method of preparing an organic semiconductor thin film in advance and then introducing the dopant later, or a method of introducing the dopant when forming the organic semiconductor thin film can be used.

  As doping of the former method, gas phase doping using a dopant in a gas state, liquid phase doping in which a solution or a liquid dopant is brought into contact with the thin film, and diffusion doping in which a solid state dopant is brought into contact with the thin film Examples of such methods include solid phase doping. In liquid phase doping, the efficiency of doping can be adjusted by applying electrolysis.

  In the latter method, a mixed solution or dispersion of an organic semiconductor compound and a dopant may be simultaneously applied and dried. For example, when using a vacuum evaporation method, a dopant can be introduce | transduced by co-evaporating a dopant with an organic-semiconductor compound. When a thin film is formed by a sputtering method, a dopant can be introduced into the thin film by sputtering using a binary target of an organic semiconductor compound and a dopant. As other methods, any of chemical doping such as electrochemical doping, photoinitiation doping, and physical doping such as ion implantation can be used.

  In addition, as a resin constituting the substrate, styrene polymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, Polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester alkyd resin, polyamide, polyimide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, Thermoplastic resins such as ketone resins, polyvinyl butyral resins, polyether resins, polyester resins, silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, other crosslinkable thermosetting resins, and epoxy resins Relate, urethane - photocurable resin such as acrylate. In addition, about polyimide, commercial items, such as brand name SE-1180 (made by Nissan Chemical) and brand name AL3046 (made by JSR), can be used.

Next, a method for manufacturing a semiconductor device according to the present embodiment will be described [Method for manufacturing a semiconductor device].
The semiconductor device of this embodiment includes a step of forming a gate electrode on a substrate, a step of forming a gate insulating layer having a refractive index smaller than that of the liquid crystal layer on the gate electrode, and a source electrode on the gate insulating layer. And forming a drain electrode, and forming a semiconductor thin film made of an organic compound on the source electrode and the drain electrode.

  Here, as a method of manufacturing the gate electrode, the source electrode, and the drain electrode, a method of forming an electrode by a photolithographic method or a lift-off method using a conductive thin film formed by using a method such as vapor deposition or sputtering with the above-described materials. Alternatively, a method of etching using a resist such as thermal transfer or ink jet on a metal foil such as aluminum or copper is used. Alternatively, a conductive polymer solution or dispersion, or a conductive fine particle dispersion may be directly patterned by ink jetting, or an electrode may be formed from the coating film by lithography or laser ablation. Furthermore, a method of forming an electrode by patterning an ink containing a conductive polymer or conductive fine particles, a conductive paste, or the like by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  Here, examples of the conductive fine particles include fine metal particles such as platinum, gold, silver, copper, cobalt, chromium, iridium, nickel, palladium, molybdenum, and tungsten having a particle diameter of 1 to 50 nm, preferably 1 to 10 nm. In this case, an electrode formed by heat fusing metal fine particles is used.

  As a method for manufacturing the gate insulating layer, the gate insulating layer can be formed by a method in which a fluorine-based polymer or a methyl-containing polysiloxane material as described above is spin-coated and baked.

In addition, organic semiconductor thin film fabrication methods include vacuum deposition, molecular beam epitaxial growth, ion cluster beam, low energy ion beam, ion plating, CVD, sputtering, plasma polymerization, and electropolymerization. , Chemical polymerization method, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, LB method and the like, and can be used depending on the material.
The thickness of the thin film made of these organic semiconductors is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the thickness of the active layer made of the organic semiconductor. Although it varies depending on the semiconductor, it is generally 1 μm or less, particularly preferably 5 to 300 nm.

  In the semiconductor device of this embodiment, when the gate insulating layer is formed at a temperature of about 200 ° C. or lower, the polymer substrate can be used as a common substrate for the thin film transistor and the liquid crystal display element.

In the liquid crystal display element of the present embodiment, a drive circuit for driving the liquid crystal layer is integrally formed. However, a semiconductor device constituting the drive circuit can be separately manufactured and combined with the liquid crystal layer. In that case, the drain electrode and the signal electrode of the liquid crystal layer may be formed separately and connected later.
(Second Embodiment)
The second embodiment is different from the first embodiment in that the gate insulating layer is made of a porous polymer material. However, since other points are common, different porous bodies will be described.
[About porous materials]
The “porous body” in the present invention is a solid substance having a large number of pores, and is characterized by the proportion of the pores in the substance, the pore size distribution, and the pore shape. The pore size is defined by IUPAK (The International Union of Pure and Applied Chemistry), classified into micropores with a diameter of 2 nm or less, mesopores with a diameter of 2 to 50 nm, and macropores with a diameter of 50 nm or more. Is done.

  In addition, the size of the pores of the porous body is average, and may be a columnar shape instead of a spherical shape. Moreover, it may be formed by spherical holes having different sizes, or a spherical shape may be included in the columnar shape.

  The refractive index of such a porous body is considered to be an average refractive index of pores having the same refractive index as that of air and substances having a refractive index higher than that of air. Therefore, for example, when 20% of the volume of the gate insulating layer made of a porous body is a hole and 80% is a substance having a refractive index of 1.6, it is 1.48. Refractive index is less than 1.5.

  Here, the pore diameter is defined as a triaxial average diameter. Specifically, it can be obtained from a cross-sectional scanning electron microscope image or a cross-sectional transmission electron microscope image. In the case of a sample for which it is difficult to measure an electron microscope image, the pore size distribution is measured by the X-ray small angle scattering method, and the diameter that maximizes the particle size distribution is taken as the average diameter. The volume density of the pores can be determined by measuring the pore size distribution by the X-ray small angle scattering method.

  In the semiconductor device of this embodiment, by using such a porous material having a large number of pores for the gate insulating layer, it is possible to obtain a thin and low dielectric constant insulating film with almost no leakage current.

  This is presumably because the surface of the porous body has a curved surface, so that the specific surface area increases, and as a result, the capacitance of the insulating layer increases. Moreover, since the charge in the memory cell can be increased by increasing the capacitance, it is suitable for forming the drive circuit for the liquid crystal display element of this embodiment.

  In addition, by using a porous body in which at least 20% of the total volume is occupied by pores, the contact area at the interface between the organic semiconductor layer and the porous body can be increased, and the on-current can be increased. On the other hand, since air having excellent insulating properties is contained in the porous body, it is preferable for further improving the electrical insulating properties of the gate insulating layer and suppressing the leakage current at the time of OFF.

  Furthermore, in order to increase the number of carriers accumulated near the interface between the organic semiconductor layer and the porous body, the thickness of the porous body is set to 1 nm or more, and the contact area at the interface between the organic semiconductor layer and the porous body is sufficient. It is preferable to enlarge it.

  Here, the thickness of the porous body is defined as the thickness at the interface between the organic semiconductor layer and the porous body, and the interface is defined as the average surface of the roughness curved surface of the porous body surface. Here, the roughness curved surface and the average surface are obtained by extending the roughness curve and average line of the cross section of the porous body layer to a two-dimensional plane.

  Therefore, the thickness of the porous body of this embodiment means that the thickness from the average surface of the roughness curved surface of the porous body surface is 1 nm or more. Specifically, the thickness can be obtained by measuring the cross-sectional shape with a scanning electron microscope (SEM), a transmission electron microscope (TEM), a scanning probe microscope (SPM), or the like. It can also be obtained from the element depth distribution by a secondary ion mass spectrometry system (SIMS).

Furthermore, if a porous body having an average pore radius of 100 nm or less is used, a gate insulating layer made of a porous body can be obtained by using a flexible substrate even if stress due to bending or twisting is applied to the semiconductor device. Since stress is absorbed, it is possible to prevent peeling from the substrate.
Further, if the average value of the pore radii is 100 nm or less, the mechanical strength of the porous body can be made higher than that of the macroporous porous body, and the organic semiconductor device (or the organic semiconductor device is driven by a driving circuit). Even if a flexible substrate is used as the substrate, the porous body will not be crushed and the porosity will not change even if the liquid crystal display element is bent, rolled or dropped. The electrical characteristics by using the body can be maintained.

  As the porous material of the present embodiment, a polymer material such as polyethylene or polyimide can be used. Polyethylene and polyimide can be made porous by performing plasma surface treatment under appropriate conditions.

Next, an example of a method for manufacturing the semiconductor device of this embodiment will be described.
[Method for Manufacturing Semiconductor Device]
In the present embodiment, an aluminum electrode is formed by vacuum deposition on a glass substrate provided with a black resin to produce a gate electrode.

  Next, a mixed solution of tetraethoxysilane (TEOS), water, ethanol, and concentrated hydrochloric acid in a molar ratio of 1: 5: 5: 0.03 is heated to 70 ° C. and stirred for 4 hours. To the heated solution was added a surfactant, for example, an ethanol solution of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer (EO-b-PO-b-EO), stirred and allowed to stand for 5 hours. A silicon alkoxide is hydrolyzed under acidic conditions in the presence of a surfactant to obtain a sol solution. This sol solution is spin-cast so as to cover the gate electrode, and dried in an oven at 110 ° C. to produce a surfactant-dispersed silica film.

  Next, after removing the surfactant by heating the produced silica film at 300 ° C. in air, it is immersed in hexamethyldisilazane (HMDS) and vacuum-dried at 110 ° C.

  Thereby, a gate insulating film made of a porous body having a film thickness of about 0.5 μm can be formed.

  Next, after disposing a metal mask on the porous body, indium tin oxide (ITO) is formed by sputtering to produce source and drain electrodes.

  Next, a xylene solution of regioregular poly (3-hexylthiophene) is applied and formed on the source and drain electrodes by an inkjet method to form an organic semiconductor layer having a thickness of 50 nm, and ITO is sputtered again thereon. Thus, an organic semiconductor device having the same cross-sectional configuration as that of the first embodiment shown in FIG. 1 can be manufactured.

  According to the liquid crystal display element of this embodiment, since the gate insulating layer also serves as the low refractive index layer of the liquid crystal display element, the manufacturing process can be simplified and the organic semiconductor device can be manufactured at low cost. In addition, since the organic semiconductor layer is stacked after the source and drain electrodes are formed, the semiconductor material does not dissolve in the solvent even when a solvent is used for patterning the source and drain electrodes, and the characteristics of the liquid crystal display element are improved. There is no impact.

  FIG. 4 shows the result of observation of the surface of the porous body manufactured by the method for manufacturing a semiconductor device of this embodiment with a transmission electron microscope (TEM).

  As can be seen from FIG. 4, it can be seen that innumerable pores of almost uniform size are formed in the porous body.

  Next, the electrical characteristics of the organic transistor having the gate insulating layer made of such a porous body and the reflectance were measured. The reflectance was 30%. The current-voltage characteristics were measured with a semiconductor parameter analyzer 4145B (manufactured by Hewlett-Packard) in a nitrogen atmosphere.

  FIG. 5 is a diagram showing current-voltage characteristics of the organic transistor of this embodiment.

  In FIG. 5, the vertical axis indicates the current (Ids) A flowing between the source and the drain, and the horizontal axis indicates the source-drain voltage (Vds) V.

  The graph in the figure shows the relationship between the source-drain voltage and the source-drain current when the gate voltage Vg is changed from 0V to -30V.

  For example, when the source-drain voltage is −30 V, when the gate voltage changes, the source-drain current also changes, and modulation by the gate voltage is performed. Further, at that time, a maximum ON current of about 0.1 mA is obtained between the source and the drain, so that the on / off ratio at a source-drain voltage of −30 V is about 300.

  Next, in order to confirm the effect of the porous gate insulating layer in the semiconductor device of the present embodiment, the surfactant is removed at 300 ° C. in the air with respect to the surfactant-dispersed silica film in the manufacturing method described above. The current-voltage characteristics of the organic transistor formed without treatment, immersion in hexamethyldisilazane (HMDS), and vacuum drying at 110 ° C. were similarly measured in a nitrogen atmosphere.

  As a result of the measurement, the on / off ratio at a source-drain voltage of −30 V was about 4, and the reflectance was 2%.

As a result, it has been found that the semiconductor device of this embodiment can sufficiently withstand the practical use as a drive circuit for a liquid crystal display element, and can sufficiently ensure brightness in white display.
(Third embodiment)
The third embodiment is different from the second embodiment in that the gate insulating layer is made of a metal oxide porous body. However, since other points are common, a method for manufacturing a different semiconductor device will be described.
[Method for Manufacturing Semiconductor Device]
The semiconductor manufacturing method of this embodiment is different from the second embodiment in the formation process of the gate insulating layer, but the other processes are common. Therefore, a different gate insulating layer forming step will be described.

A metal alkoxide is used for the porous body of this embodiment. There are many types of metal alkoxides depending on the combination of metal and alkoxy group. Examples of metals include lithium, sodium, potassium, magnesium, calcium, strontium, barium, aluminum, indium, germanium, bismuth, iron, copper, Examples thereof include yttrium, zirconium, tantalum, and silicon. In particular, silicon, titanium, aluminum, zirconium and the like are suitable.
Silicon alkoxides include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetrapropoxysilane, tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxy. Silane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, Decyltrimethoxysilane, trifluoropropyltrimethoxysilane, heptadecatrifluorodecyltrimethoxysilane, etc. It is. Further, fumed silica, colloidal silica, water glass and the like can also be used.

  Since the porous body constituting the gate insulating layer in the semiconductor device of the present embodiment is a metal oxide, it has excellent chemical resistance, oxidation resistance, and mechanical strength compared to, for example, a polymer compound. Can be increased.

  The gate insulating layer of this embodiment can be formed as follows as an example.

  In the presence of a surfactant, a sol solution obtained by hydrolyzing a metal alkoxide under acidic conditions is applied and dried so as to cover the gate electrode. Then, the obtained surfactant-dispersed metal oxide is fired to decompose and remove the surfactant, thereby forming a gate insulating layer made of a metal oxide porous body.

  Here, the surfactant-dispersed metal oxide film refers to a state in which the surfactant is held at the last part in the porous body using the metal oxide as a base material, and the sol solution of this embodiment is applied and dried. This is the state of the film obtained. By removing the surfactant from the surfactant-dispersed metal oxide film, hollow pores are formed in the film to obtain a porous body layer. The firing temperature has an optimum temperature as appropriate depending on the surfactant to be used, but is preferably 400 ° C. or less.

  As a method for decomposing and removing the surfactant, in addition to firing, the surfactant-dispersed metal oxide film coated with sol solution and dried is washed with a solvent to elute and remove the surfactant. It is also possible to obtain a porous body layer. Further, a porous body is formed from a surfactant-dispersed metal oxide film without heating by a method of oxidizing and removing a surfactant in an ozone atmosphere and a method of oxidizing and removing a surfactant in an oxygen plasma atmosphere. It is also possible. If these methods other than firing are used, a metal oxide porous layer can be formed even if a material having low heat resistance exists in the element.

  The method of extracting and removing with the solvent of the present embodiment is not limited to the solvent to be used, but methanol, ethanol, water, tetrahydrofuran and the like are preferable because they have high polarity and easily elute the active agent. In addition, when the pores are hydrophobized by some method, solvents with low polarity are effective. Hydrocarbon solvents such as petroleum ether, hexane, and octane, and aromatic hydrocarbons such as benzene, toluene, and xylene The solvent of the system is effective. These heated polar and nonpolar solvents are more preferred solvents because of the increased solubility of the active agent.

  The metal oxide porous body of the present embodiment is applicable to a manufacturing process having any coating process without requiring a special coating process, and is excellent in productivity. It is also possible to use a coating process such as a spin casting method, a dip coating method, a screen printing method, a casting method, etc., and particularly preferably, a spin casting method in which a film thickness can be easily controlled and a relatively large area can be applied. And dip coating.

  Examples of the surfactant used in the present embodiment include a cationic surfactant, an anionic surfactant, polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers and block copolymers thereof. Either a nonionic surfactant or a triblock copolymer may be used. In addition, a compound such as mesitylene may be added to increase the volume of the hollow pores.

  The cationic surfactant is not particularly limited, and examples thereof include a quaternary ammonium salt or an alkylamine salt. The quaternary ammonium salt is preferably a quaternary alkyltrimethylammonium halide or hydroxide represented by the formula (1).

In the formula (1), the linear alkyl group R ¹ preferably has 8 to 24 carbon atoms, particularly preferably 8 to 17 carbon atoms. When the number of carbon atoms is 25 or more, it is insoluble and difficult to handle. Moreover, as a halogen atom of X, a chlorine atom and a bromine atom are preferable. Specific examples of the quaternary alkyltrimethylammonium salt include octyltrimethylammonium chloride, octyltrimethylammonium bromide, octyltrimethylammonium hydroxide, decyltrimethylammonium chloride, decyltrimethylammonium bromide, decyltrimethylammonium hydroxide, Dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltrimethylammonium hydroxide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium hydroxide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, hydroxy acid Include octadecyl trimethylammonium etc., may be used in combination of one or more of these ammonium salts.

  Moreover, as an alkylamine salt, the alkylamine salt represented by Formula (2) is mentioned.

In the formula (2), the linear alkyl group R ¹ preferably has 8 to 24 carbon atoms, particularly preferably 8 to 17 carbon atoms. When the number of carbon atoms is 25 or more, it is insoluble and difficult to handle. Moreover, a chlorine atom and a bromine atom are mentioned as a halogen atom of X.

  The porous body of the metal oxide of the present invention can also be produced by an anodic oxidation method. In this case, aluminum, titanium, zirconia, niobium, hafnia, zinc, tantalum, or the like can be used for the gate electrode.

  Here, when the porous body is composed of silicon oxide, the process of removing the surfactant from the surfactant-dispersed silicon oxide film or the crack after the removal depends on the preparation conditions of the sol solution. In many cases, it is difficult to form a uniform and smooth porous body layer.

However, this can be solved by hydrophobizing the pore surface of the porous body.
Examples of the hydrophobizing method include a method of adding a silicon compound having a hydrophobizing portion to the sol solution, or a method of hydrophobizing the pore surface of the porous body layer after removing the surfactant.

  The former can be achieved by a method of adding an alkoxysilane having an alkyl group or a method of adding a chlorosilane having an alkyl group. Specific materials include monoalkyltrialkoxysilane, dialkyldialkoxysilane, and trialkylalkoxysilane. As alkyl groups, for example, methyl group, ethyl group, propyl group, butyl group, phenyl group, vinyl group and the like are added, and as alkoxy groups, for example, methoxy group, ethoxy group, propoxy group, butoxy group are added. A material to which a group or the like is added can be used.

In the latter case, the porous body layer is formed and then dried by immersing it in a solution of 1,1,1,3,3,3-hexamethylsilazane or a chlorosilane having an alkyl group, or by exposing it to these vapors. Can be achieved.
(Fourth embodiment)
The fourth embodiment is different from the first to third embodiments in that the gate insulating layer of the organic transistor has two layers. However, since other points are common, the same components are denoted by the same reference numerals, and differences will be described.

  FIG. 6 is a schematic cross-sectional view showing the liquid crystal display element of the fourth embodiment.

  As shown in FIG. 6, the gate insulating layer 15 of the organic transistor 10 constituting the driving circuit of the liquid crystal display element 30 of the present embodiment is a stacked layer in which a first insulating layer 15a and a second insulating layer 15b are stacked. It has a structure. Of the gate insulating layer 15, the second insulating layer 15 b close to the liquid crystal layer 3 is configured to have a refractive index smaller than that of the liquid crystal layer 3.

  Accordingly, in the liquid crystal display element 30 using the organic transistor 10 of the present embodiment as a drive circuit, a part of light transmitted through the liquid crystal layer 3 in the light scattering state is reflected by the second insulating layer 15b, so that white display is performed. It can be brighter.

  Here, although the gate insulating layer 15 of the present embodiment has a two-layer structure, the gate insulating layer 15 does not necessarily have to be two layers, and may have three or more layers.

  As the material used for the first insulating layer 15a which is the base layer in the laminated structure, any material can be used as long as it is insulative. In general, any material such as polychloropyrene, polyethylene terephthalate, Polyoxymethylene, polyvinyl chloride, polyvinylidene fluoride, cyanoethyl pullulan, polymethyl methacrylate, polysulfone, polycarbonate, polyimide, polyethylene, polyester, polyvinylphenol, melamine resin, phenol resin, fluororesin, polyphenylene sulfide, polyparaxylene, polyacrylonitrile, etc. Organic materials, inorganic materials such as silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, silicon nitride oxide, and various insulating Langmuir-Blodgett films It is needed. Of course, it is not necessarily limited to these materials, and two or more of these materials may be used in combination.

  In general, when the average pore size of the porous body is small, the electric field tends to concentrate on the interface between the porous bodies, and as a result, the dielectric breakdown strength may be small. However, since the gate insulating layer 15 of the present embodiment has a laminated structure of two or more layers, it is possible to increase the dielectric breakdown strength of the entire insulating layer by stacking materials having a high dielectric breakdown strength.

Next, an example of a method for manufacturing the semiconductor device of this embodiment will be described.
[Method for Manufacturing Semiconductor Device]
The semiconductor device of this embodiment includes a step of forming a gate electrode on a substrate, a step of forming a gate insulating layer having a refractive index smaller than that of the liquid crystal layer on the gate electrode, and a source electrode on the gate insulating layer. And forming a drain electrode, and forming a semiconductor thin film made of an organic compound on the source electrode and the drain electrode.

  First, an aluminum electrode is formed by vacuum deposition on a glass substrate provided with a black resin to produce a gate electrode.

  Next, polyvinylphenol and a cross-linking agent hexamethoxymethylmelamine are dissolved in an n-butanol solution, spin-coated, and baked at 200 ° C. to obtain a film having a thickness of 100 nm.

Next, a mixed solution of tetraethoxysilane (TEOS), water, ethanol, and concentrated hydrochloric acid in a molar ratio of 1: 5: 5: 0.03 is heated to 70 ° C. and stirred for 4 hours. For example, an ethanol solution of polyethylene oxide, which is a surfactant, is added to the heated solution, and the mixture is stirred and allowed to stand for 5 hours. In the presence of the surfactant, silicon alkoxide is hydrolyzed under acidic conditions to obtain a sol solution. . This sol solution is spin-cast on polyvinylphenol, dried at 110 ° C., and then exposed in an O ₂ plasma atmosphere for 3 minutes to produce a surfactant-dispersed silica film.

  Next, after removing the surfactant by heating the produced silica film at 300 ° C. in air, it is immersed in hexamethyldisilazane (HMDS) and vacuum-dried at 110 ° C.

  Next, after disposing a metal mask on the porous body, indium tin oxide (ITO) is formed by sputtering to produce source and drain electrodes.

  Next, a xylene solution of regioregular poly (3-hexylthiophene) is applied and formed on the source and drain electrodes by an inkjet method to form an organic semiconductor layer having a thickness of 50 nm, and ITO is sputtered again thereon. Thus, an organic semiconductor device having the same cross-sectional configuration as that of the fourth embodiment shown in FIG. 4 can be manufactured.

  According to the liquid crystal display element of this embodiment, since the gate insulating layer also serves as the low refractive index layer of the liquid crystal display element, the manufacturing process can be simplified and the organic semiconductor device can be manufactured at low cost. In addition, since the organic semiconductor layer is stacked after the source and drain electrodes are formed, the semiconductor material does not dissolve in the solvent even when a solvent is used for patterning the source and drain electrodes, and the characteristics of the liquid crystal display element are improved. There is no impact.

  Next, measurement of electrical characteristics and reflectance of an organic transistor having a gate insulating layer made of a porous body manufactured using the semiconductor manufacturing method of the present embodiment were measured.

  The current-voltage characteristics were measured with a semiconductor parameter analyzer 4145B (manufactured by Hewlett-Packard) under a nitrogen atmosphere.

  As a result of the measurement, the reflectance was about 37%, and the on / off ratio at a source-drain voltage of −20 V was about 200.

Next, in order to confirm the effect of the porous gate insulating layer in the semiconductor device of this embodiment, the subsequent exposure treatment in the O ₂ plasma atmosphere to the surfactant-dispersed silica film in the manufacturing method described above. The current-voltage characteristics of the organic transistor obtained by producing the surfactant-dispersed silica film were measured with a semiconductor parameter analyzer 4145B (manufactured by Hewlett-Packard) in a nitrogen atmosphere.

  As a result, the on / off ratio at a source-drain voltage of −20 V was about 6. Further, the reflectance was 5%.

  As a result, it has been found that the semiconductor device of this embodiment can sufficiently withstand the practical use as a drive circuit for a liquid crystal display element, and can sufficiently ensure brightness in white display.

In this embodiment, a predetermined polymer is spin-coated on the gate electrode and baked,
A porous body is formed by immersing in hexamethyldisilazane and then vacuum drying, but is not necessarily limited to this method, for example, CVD method, plasma CVD method, plasma polymerization method, vapor deposition method, A spin coating method, a dipping method, a cluster ion beam evaporation method, a Langmuir-Blodgett method, or the like may be used. In the present embodiment, a surfactant-dispersed silica film is made of a polymer material to form a porous body in the gate insulating layer, but the polymer material is not necessarily used. The metal oxide described in the embodiment can also be used.

  In the liquid crystal display element of the present embodiment, a drive circuit for driving the liquid crystal layer is integrally formed. However, a semiconductor device constituting the drive circuit can be separately manufactured and combined with the liquid crystal layer. In that case, the drain electrode and the signal electrode of the liquid crystal layer may be formed separately and connected later.

It is a schematic sectional drawing of the liquid crystal display element which shows 1st Embodiment of the liquid crystal display element of this invention, an organic semiconductor device, and the manufacturing method of an organic semiconductor device. It is a figure which shows the state of the liquid crystal layer used for the liquid crystal display element of this embodiment, and the liquid crystal droplet in a liquid crystal layer. It is a figure which shows the refractive index of various liquid crystal materials. It is a figure which shows the refractive index of various liquid crystal materials. The result of having observed the porous body surface manufactured with the manufacturing method of the semiconductor device of this embodiment with the transmission electron microscope (TEM) is shown. It is a figure which shows the current-voltage characteristic of the organic transistor of this embodiment. It is a schematic sectional drawing which shows the liquid crystal display element of 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film substrate 2 Substrate 3 Liquid crystal layer 3a Liquid crystal droplet 3b Liquid crystal 4 Light absorption layer 5 Scan electrode 8 Polymer 10 Organic transistor 11 Gate electrode 12 Source electrode 13 Drain electrode 14 Organic semiconductor layer 15 Gate insulating layer 15a First insulating layer 15b Second insulating layer 30 Liquid crystal display element

Claims (7)

A liquid crystal display element in which a liquid crystal layer and a driving circuit are stacked between opposing substrates, and the liquid crystal layer exhibits a light transmission state or a scattering state depending on the presence or absence of an electric field applied from the driving circuit,
The drive circuit is constituted by an organic transistor having a gate insulating layer having a refractive index smaller than that of the liquid crystal layer in a light transmission state,
The gate insulating layer is at least micropores, mesopores, and any one that made of a porous material that includes pores of size you wherein liquid crystal display device of the macropores. A liquid crystal display element in which a liquid crystal layer and a driving circuit are stacked between opposing substrates, and the liquid crystal layer exhibits a light transmission state or a scattering state depending on the presence or absence of an electric field applied from the driving circuit,
The drive circuit is constituted by an organic transistor having a gate insulating layer having a refractive index smaller than that of the liquid crystal layer in a light transmission state,
The gate insulating layer, a porous body liquid crystal display device you characterized in that it consists of metal oxides. A liquid crystal display element in which a liquid crystal layer and a driving circuit are stacked between opposing substrates, and the liquid crystal layer exhibits a light transmission state or a scattering state depending on the presence or absence of an electric field applied from the driving circuit,
The drive circuit is constituted by an organic transistor having a gate insulating layer having a refractive index smaller than that of the liquid crystal layer in a light transmission state,
The gate insulating layer is silicon oxide porous body liquid crystal display device you characterized in that it consists of. The porous body, any one liquid crystal display device according one of claims 1 to 3, characterized in that it has a 1 nm or more thickness. The porous body, of the total volume, any one liquid crystal display element according of the claims 1 to 3, the proportion of holes is equal to or less than 20%. The porous body, the liquid crystal display device of any one of claims 1 to 3, wherein the average pore radius of 100 nm or less. The gate insulating layer, the liquid crystal display device of any one of claims 1 to 6, wherein the plurality of layers in which are laminated.