JP3095860B2 - Method for manufacturing bidirectional nonlinear resistance element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching nonlinear resistance element used for a liquid crystal display device or the like.

[0002]

2. Description of the Related Art At present, image display methods of a liquid crystal television are roughly classified into a simple matrix system and an active matrix system. In the simple matrix system, a liquid crystal is sandwiched between two sets of strip electrodes provided so that their directions are at right angles to each other, and a drive circuit is connected to each of these strip electrodes. This method can realize a low-cost system because of its simple structure, but has a problem that the contrast is low due to crosstalk. In contrast, the active matrix method has a switch provided for each pixel to hold the voltage, and the voltage at the time of selection can be maintained even when driving in a time-division manner. The disadvantage is that the structure is complicated and the manufacturing cost is high. We use conductors / insulators / conductors (Metal / Insulator) as switching elements.
An active matrix type liquid crystal display panel is manufactured using a bidirectional nonlinear resistance element having a structure of / Metal). Conventionally, TaO _x obtained by anodizing Ta as the lower electrode has been used as the insulator. However, its relative dielectric constant is about 26, the general element shape is 5 μm × 4 μm, and the anodic oxide film thickness is 0.06 μm.
Under the micrometer condition, the element capacitance is 0.
It was 1 pF, which was as large as about 液晶 of the liquid crystal capacitance of a general pixel portion (200 μm × 200 μm). When a voltage is applied to the liquid crystal display panel, the voltage is divided in proportion to the reciprocal of the capacitance ratio between the liquid crystal and the device.However, with the conventional capacitance ratio, sufficient voltage is not applied to the bidirectional nonlinear resistance element, and the switching characteristics are poor. As a result, there is a problem that the display quality is inferior to that of a liquid crystal display panel using a TFT (thin film transistor) as a switching element. In order to solve this problem, an organic insulating film formed by an electrolytic polymerization method was used for the insulator portion to improve the switching characteristics (Japanese Patent Application No. 1-85374). In general, the relative dielectric constant of the organic insulating film was 10 or less, and the element capacitance was sufficiently smaller than the liquid crystal capacitance, and the switching characteristics were sufficiently improved. Preparation of the organic insulating film includes a monomer or dimer as a starting material for polymerization, oligomers and, NaCl0 _4, LiBF ₄ or the like of the inorganic salt or CF ₃ SO ₃ Na as a supporting salt, a salt of an organic acid such as CF ₃ COONa After an organic film is formed on a conductor by electrolytic polymerization in an aqueous solution or a solution using an organic solvent, a dedoping process is performed electrochemically to completely form an insulator. Further, by using an alkali hydroxide such as NaOH as a supporting salt, an insulating film is obtained in a film-formed state, and an improvement has been made such that an organic insulating film is formed without performing the undoping treatment. 1-85 Ganping
372).

[0003]

The switching property of a bidirectional nonlinear resistance element using an organic electrolytic polymer film could be greatly improved by improving the capacitance ratio with the liquid crystal.
In addition, by using an alkali hydroxide such as NaOH as a supporting salt, an insulating film was obtained in a film-formed state, and an insulating film could be easily obtained. However, the bidirectional nonlinear resistance element using the organic electropolymerized film we invented has a small resistance, which is 1/10 to 1/100 of the resistance of the element having the same area using the conventional TaO _x as an insulator. Had the disadvantage that That is, since the element resistance is low, crosstalk occurs, and the electric charge once written in the liquid crystal is not easily retained, so that a sufficient contrast as a display panel cannot be secured. If the element size is reduced, the resistance value increases. On the other hand, if a small-sized element portion is manufactured by using photolithography, an expensive manufacturing apparatus is required, which has a problem that the cost is increased. Was. Therefore, an object of the present invention is to solve this problem, and to provide a method of manufacturing a bidirectional nonlinear resistance element using an organic electrolytic polymer film having a high resistance value as an insulator.

[0004]

According to the method of manufacturing a bidirectional nonlinear resistance element of the present invention, a highly insulating organic electrolytic polymer film 2 is formed on an electrode 1 having a predetermined pattern by an electrolytic polymerization method. A conductor / insulator (organic electrolytic polymer film 2) / conductor 3 having an electrode 3 in which a conductor which is the same as or different from the material of the electrode 1 is formed on the organic electrolytic polymer film 2 in a predetermined pattern. In the method of manufacturing a bidirectional nonlinear resistance element for switching of a structure, a carbonate or a hydrogen carbonate is used as a supporting salt at the time of electrolytic polymerization to form the insulator. 0.0
It is characterized in that it is used at a concentration of more than 5M and less than 0.5M, and in the case of bicarbonate, it is used at a concentration of more than 0.1M.

[0005]

When a carbonate or a bicarbonate is used as a supporting salt at the time of electrolytic polymerization, the supporting salt does not dope the organic electropolymerized film, so that an insulating film is formed. A film having higher resistance than alkali hydroxide can be obtained. In addition, since the pH is low, even when electrolysis is performed at a high potential, anodic decomposition of the solvent hardly occurs, and the polymerized polymer is hardly decomposed. When the supporting salt concentration is below the range shown in claims 2 and 3, the electrolytic current is small, the film thickness is thin, the resistance value is low, and the withstand voltage is low. The bidirectional nonlinear resistance element does not exhibit stable electric characteristics. Further, a carbonate is used, and a supporting salt concentration is set to claim 2.
It has been experimentally confirmed that the resistance value decreases when it is higher than the range indicated by.

[0006]

【Example】

Example 1 An ITO film having a thickness of 0.15 μm was formed on a glass substrate by sputtering, and an ITO lower electrode having a predetermined pattern was obtained by photolithography (FIG. 1A). This electrode material is not particularly limited to ITO, but may be any material having a sufficiently high conductivity. An organic insulating film 2 was formed on the ITO pattern by electrolytic polymerization. In the electrolytic polymerization, a solution obtained by adding 0.2 M sodium hydrogen carbonate as a supporting salt to an aqueous solution containing 0.25 M pyrrole as a monomer was used. A platinum plate was used as a counter electrode of the electrolytic cell, and a silver / silver chloride electrode was used as a reference electrode. The glass substrate with ITO was immersed in the electrolytic solution and subjected to electrolytic polymerization at a constant potential of +1.5 V for 60 minutes to form a polypyrrole electrolytic polymerized film (FIG. 1).
(B)). The thickness of the electropolymerized film was 0.14 micrometers. After washing the electrolytic polymer film with pure water and gently drying it with Ar gas, an ITO upper electrode 3 was formed to a thickness of 0.15 μm by sputtering film formation and patterning by photolithography to produce a device. (FIG. 1 (c)). The resistance value per area of the bidirectional nonlinear resistance element was 10 ^7.2 ohm cm ² , which was about five times higher than that of a conventional bidirectional nonlinear resistance element using an electropolymerized organic film as an insulator. In addition, stable switching characteristics were exhibited. The active matrix type liquid crystal display device incorporating the bidirectional nonlinear resistance element has a higher crosstalk and contrast than a conventional bidirectional nonlinear resistance element using an electrolytic polymerized film (Comparative Example 1) as an insulator. There was an improvement in the ratio.

Example 2 Same as Example 1, except that a polypyrrole electrolytic polymerized film was formed using a pyrrole aqueous solution containing 0.5 M sodium bicarbonate as a supporting salt at the time of electrolytic polymerization. A non-linear resistance element was manufactured. The thickness of the electropolymerized film was 0.18 micrometers. Resistance per area of the bidirectional non-linear resistance element is 10 ^{7. 3} ohm cm ^2, obtained the same effects as in Example 1.

Example 3 Same as Example 1, except that a polypyrrole electropolymerized film is formed by performing electropolymerization at a constant potential of silver-silver chloride reference potential +1.9 V for 60 minutes.
A bidirectional nonlinear resistance element was fabricated. The thickness of the electrolytic polymerized film was 0.14 micrometers. The resistance value per area of the bidirectional nonlinear resistance element is 10 ^7.5 ohm c.
m ^2, which is about 10 times higher than that of a conventional bidirectional nonlinear resistance element using an electropolymerized organic film as an insulator. In addition, stable switching characteristics were exhibited. The active matrix type liquid crystal display device incorporating the bidirectional nonlinear resistance element is compared with the conventional one (Comparative Example 1) or the case where the bidirectional nonlinear resistance element using the electrolytically polymerized film as an insulator in Example 1 is used. Crosstalk and contrast ratio were improved.

Example 4 The same as Example 1, but using a pyrrole aqueous solution containing 0.2 M sodium carbonate as a supporting salt at the time of electrolytic polymerization and forming a polypyrrole electrolytic polymerized film, A resistance element was manufactured.
The film thickness of the electrolytic polymerization film was 0.28 micrometers. The resistance value per area of the bidirectional nonlinear resistance element was 10 ^7.2 ohm cm ² , and the same effect as in Example 1 was obtained.

Comparative Example 1 A method for manufacturing a bidirectional nonlinear resistance element using a conventional organic electrolytic polymer film as an insulator will be described. Same as Example 1, except that a pyrrole aqueous solution containing 0.01 M sodium hydroxide was used as a supporting salt at the time of electrolytic polymerization. This concentration is the optimum concentration at which the highest resistance and stable electrical characteristics are obtained when sodium hydroxide is used as the supporting salt. By forming a polypyrrole electrolytic polymerized film in the polymerization solution, a bidirectional nonlinear resistance element was produced. The film thickness of the electrolytic polymerization film was 0.20 micrometers. The resistance value per area of the bidirectional nonlinear resistance element was 10 ^6.5 ohm cm ² .

Comparative Example 2 The same as Example 1, except that a polypyrrole electrolytically polymerized film was formed using a pyrrole aqueous solution containing 0.1 M sodium hydrogencarbonate as a supporting salt during electrolytic polymerization, whereby bidirectional non-linearity was obtained. A resistance element was manufactured. The thickness of the electropolymerized film was 0.10 micrometers. Resistance per area of the bidirectional non-linear resistance element showed 10 ^5.9 ohm cm ^2.

Comparative Example 3 The same as Example 1, except that a polypyrrole electrolytically polymerized film was formed using a pyrrole aqueous solution containing 0.5 M sodium carbonate as a supporting salt at the time of electrolytic polymerization. An element was manufactured.
The thickness of the electrolytic polymerized film was 0.29 micrometers. Resistance per area of the bidirectional non-linear resistance element showed 10 ^6.2 ohm cm ^2.

Comparative Example 4 The same as in Example 1, except that a pyrrole aqueous solution containing 0.05 M sodium carbonate was used as a supporting salt at the time of electrolytic polymerization to form a polypyrrole electrolytically polymerized film, thereby obtaining a bidirectional nonlinear resistance. An element was manufactured. The thickness of the electrolytic polymerized film was 0.14 micrometers. The resistance value per area of the bidirectional nonlinear resistance element was 10 ^6.6 ohm cm ² .

[0014]

[Table 1]

[0015]

According to the present invention, a maximum of 1
A method for manufacturing a bidirectional nonlinear resistance element using an organic electrolytic polymer film having a resistance value of 0 as an insulator can be provided. The active matrix liquid crystal display device incorporating the bidirectional nonlinear resistance element exhibited improved crosstalk and contrast ratio as compared with the case where a conventional organic electrolytic polymer film was used as an insulator.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in each manufacturing process of a switching nonlinear resistance element of the present invention.

[Explanation of symbols]

 Reference Signs List 1 lower electrode 2 organic electropolymerized film 3 upper electrode 4 substrate

Continuation of the front page (56) References JP-A-3-237435 (JP, A) JP-A-64-55540 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1 / 1362 G02F 1/13 101 H01L 49/02 H01L 21/312

Claims (4)

(57) [Claims] An organic electropolymerized film having a high insulating property is formed on an electrode having a predetermined pattern by an electropolymerization method, and then a conductive material which is the same as or different from the material of the electrode is used. Conductor 1 / Insulator (organic electrolytic polymer film 2) having electrode 3 formed on organic electrolytic polymer film 2 with
In a method for manufacturing a bidirectional nonlinear resistance element for switching having a structure of / conductor, a carbonate or bicarbonate is used as a supporting salt during electrolytic polymerization, and the insulator is formed. Device manufacturing method. 2. The method for producing a bidirectional nonlinear resistance element according to claim 1, wherein a carbonate having a concentration of more than 0.05 M and less than 0.5 M is used as a supporting salt at the time of electrolytic polymerization. 3. The method for producing a bidirectional nonlinear resistance element according to claim 1, wherein a bicarbonate having a concentration of more than 0.1 M and less than a solubility limit concentration is used as a supporting salt at the time of electrolytic polymerization. 4. The method according to claim 2, wherein pyrrole or a derivative thereof is used as a monomer of the organic electropolymerized film.