JP3054038B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device such as a liquid crystal display device having a nonlinear resistance element.

[0002]

2. Description of the Related Art In recent years, personal computers and other O
With the downsizing of the A-device, the demand for a high-performance flat display is increasing. A flat display has a configuration in which display is performed by applying a voltage between a pair of electrodes sandwiching a display medium having electro-optical characteristics. As the display medium, liquid crystal, electroluminescence, plasma, electrochromic, or the like is used. In particular, a liquid crystal display device using a liquid crystal as a display medium has been commercialized as a display device for a wide range of uses such as watches, calculators, personal computers, and televisions. With the progress of multimedia, these display devices are required to have high functions such as high resolution, high contrast, high contrast, full color, and power saving drive. As a display device satisfying these requirements, there is an active matrix type liquid crystal display device in which an active element is provided in each picture element. As the active element, two types of thin film transistors (hereinafter, referred to as TFTs) and thin film diodes (hereinafter, referred to as TFDs) are being vigorously developed. In particular, the TFD has a simpler structure than a TFT and requires a smaller number of masks in a manufacturing process, so that a reduction in cost can be expected. At present, as a TFD, MIM (Me
A tal insulator metal) element is disclosed in Japanese Patent Publication No. 61-32767, and a liquid crystal display device including the element has been commercialized.

Here, a conventional liquid crystal display device provided with a tantalum oxide MIM element will be described. FIG. 8 (a)
Of the device side substrate and the substrate on the opposite side, the MIM
FIG. 8B is a plan view showing one pixel of an element-side substrate provided with an element as an active element, and FIG.
It is D 'sectional drawing.

In FIGS. 8A and 8B, a glass substrate 1 is shown.
A scanning wiring made of tantalum and a lower electrode (scanning electrode) 102 branched from the scanning wiring are formed on the non-linear resistance layer 10 made of tantalum oxide.
3 are formed. An upper electrode 104 made of chromium or the like is formed on the non-linear resistance layer 103, and the lower electrode 102, the non-linear resistance layer 103 and the upper electrode 104 are formed.
Constitute an MIM element. In addition, ITO (I
A pixel electrode 105 made of a transparent conductive film such as ndium-tin-oxide is partially connected to both ends of the upper electrode 104 to be electrically connected to the MIM element. This nonlinear resistance layer 103 is formed by anodizing the lower electrode 102.

[0005]

In a liquid crystal display device using the above-mentioned conventional MIM element as an active element, the capacitance ratio of the MIM element to the liquid crystal is sufficiently small in order to realize high image quality. It is necessary that the current-voltage characteristics of the element be steep and the current on / off ratio be high. A conventional MIM element using tantalum oxide for a nonlinear resistance layer can form a very uniform film because the nonlinear resistance layer is formed by anodic oxidation, but has a problem that the current on / off ratio is not so high. . It is considered that the electrical conductivity of the tantalum oxide MIM follows the Pool-Frenkel equation shown in the following equation (Equation 1).

[0006]

(Equation 1)

N: carrier density, μ: mobility, q: carrier charge, s: element area, d: film thickness, φ: trap depth, ε: relative permittivity of insulating film, ε ₀ : vacuum Dielectric constant Since tantalum oxide has a high relative dielectric constant ε of 23 to 25, β is an important parameter that determines the on / off ratio.
Is smaller than that of a film having a low dielectric constant. In the case of a general tantalum oxide MIM element, the value of β is about 3. When the ratio between the current value when 20 V is applied and the current value when 5 V is applied as an on / off ratio is I _{20 V} / I _{5 V} (I _{2 0V} is the current when 20V is applied, and _I5V is the current when _5V is applied) is only about 10 ³ ), and a high on / off ratio cannot be obtained. Further, the capacitance ratio of the nonlinear resistance element to the liquid crystal increases due to the high relative dielectric constant, which hinders efficient voltage application to the element.

In order to solve such a problem, the present inventors have studied that an MIM element using a material having a small relative dielectric constant for a nonlinear resistance layer may be manufactured. As a material having a small relative dielectric constant, for example, zinc sulfide (hereinafter ZnS)
Etc.). The relative dielectric constant of this ZnS is 7
9 is smaller than that of tantalum oxide, so that the value of β becomes larger. Therefore, the on / off ratio I _20V / I _5V of the MIM element using ZnS is about 10 ⁵ , and the tantalum oxide MI
Since it is about two orders of magnitude higher than the M element, higher quality display can be obtained.

However, as a method of forming this ZnS film,
A method of forming on the lower electrode by sputtering or vapor deposition,
There is a method of anodizing this by using Zn as the lower electrode. In the former method by sputtering or vapor deposition, Zn is used.
It is easy to mix impurities into the S film, and the IV characteristics of the device can be controlled by the type and amount of the impurities. However, in this method, it is difficult to form a ZnS film having a uniform thickness and film quality, and such a variation in the film thickness and film quality directly affects the IV characteristics of the device, so that display unevenness occurs. Cause it to occur.

In the latter method using anodic sulfurization, a film having a large area can be formed uniformly, but in this method, the IV characteristics of the element are basically controlled by changing the film thickness. Therefore, the range of control of the IV characteristics is narrower than the former method by sputtering or vapor deposition. Therefore, the range of applicable display media is narrowed.

The present invention solves the above-mentioned conventional problems. A high-resolution and high-contrast display can be obtained by increasing the current on / off ratio and reducing the capacitance ratio of the nonlinear resistance element to the liquid crystal. It is an object of the present invention to provide a display device that can form a non-linear resistance layer to eliminate display unevenness, and that can change an IV characteristic to design an element according to characteristics of a display medium.

[0012]

According to a display device of the present invention, a display medium having electro-optical characteristics is sandwiched between a pair of substrates, and a voltage is applied to one of the pair of substrates to the display medium. A pixel electrode for applying voltage is provided, at least one non-linear resistance element is connected to the pixel electrode, and at least one non-linear resistance element is provided for one pixel. A scanning electrode for applying a selection signal to the non-linear resistance element is connected to the non-linear resistance element. The nonlinear resistance element has at least a nonlinear resistance layer, the nonlinear resistance layer,
It is formed by applying a voltage in an electrolytic solution in which sulfur ions or ions containing sulfur atoms are present, using a conductive film into which impurities are mixed as an anode, thereby achieving the above object.

Preferably, the conductive film in the display device of the present invention uses zinc, copper, tantalum or cadmium. Further preferably, as the impurity in the display device of the present invention, a material such as aluminum, iron, nickel, chromium, copper, silver, manganese, or indium can be used, and a material containing at least one of these materials is used. You may. Further, preferably, the display medium in the display device of the present invention is made of liquid crystal.

[0014]

According to the present invention, a sulfide film is formed by applying a voltage (hereinafter referred to as anodic sulfide) to a conductive film in which impurities are mixed as an anode in an electrolytic solution containing sulfur ions or ions containing sulfur atoms. Is formed. Since this sulfide has a lower dielectric constant than an oxide, it can have a larger on / off ratio than a tantalum oxide MIM element, and can have a smaller capacitance ratio of the nonlinear resistance element to the liquid crystal. Becomes Further, a dense and uniform sulfide film having a small pinhole and a uniform film thickness and quality can be formed by the anodic sulfide method, and the IV characteristics of the element can be changed depending on the type and amount of impurities.

[0015]

Embodiments of the present invention will be described below.

In the present invention, the conductive film containing impurities is anodized.

As the conductive film, a conductive material such as zinc, copper, tantalum or cadmium can be used. In addition, as the impurity, a material such as aluminum, iron, nickel, chromium, copper, silver, manganese, or indium can be used, and two or more of these materials may be used in combination. The conductive film into which impurities are mixed can be formed by a thin film formation method such as a sputtering method, a vacuum evaporation method, or a CVD (chemical vapor deposition) method.

The anodic sulfurization can be carried out, for example, as follows using an electrolytic apparatus as shown in FIG.
First, an electrolytic bath 11 is filled with an electrolytic solution 12 containing sulfur ions or ions containing sulfur atoms, and a substrate on which a conductor to be sulfurized is formed is immersed to form an anode 13.
By applying a voltage between the anode 13 and the cathode 14 made of platinum or the like, a film made of sulfide is formed on the surface of the conductor film. The film obtained by this anodic sulfurization can be a dense sulfide film having a small number of pinholes and a uniform film thickness and film quality. Therefore, when this film is used as a non-linear resistance layer, display unevenness due to variation in characteristics is reduced. It can be made hard to occur.

In the anodic sulfurization step, the electrolyte 12
The sulfur ions therein move to the anode 13 by electrolysis and react with the metal ions of the anode 13 to form insoluble sulfides. The reaction occurring at the anode 13 is represented by the following formula (2)
Can be expressed as

[0020] _{^{2M + mS 2- → M 2 S}} m + 2me - ··· (2) However, M represents an m-valent metal ion.

As described above, in anodic sulfurization, a thin film is formed by a reaction process similar to anodic oxidation. Also, as in the case of anodic oxidation, the film thickness of the sulfide film is generally proportional to the formation voltage, so that a constant voltage is applied between the two electrodes to control the film thickness by the voltage value (constant voltage formation), There are two types of methods (constant current formation) in which the applied voltage is increased so that the current density applied during the period is constant, and the film thickness is controlled by the formation time or the ultimate voltage. Constant voltage formation is
There is an advantage that the film thickness can be easily controlled by the applied voltage, and the constant current formation has an advantage that a sulfide film having a uniform film quality in the vertical direction can be formed.

The solvent and solute of the electrolytic solution 12 do not contain hydroxide ions such as water (non-aqueous electrolytic solution)
It is desirable to use If the electrolyte solution 12 contains ions containing oxygen atoms, the anodic oxidation reaction represented by the following formula (3) is more likely to occur than the anodic sulfidation reaction represented by the above formula (2), and oxidation is more likely than sulfide. This is because the object is preferentially formed. However, a small amount of water that does not cause an oxide forming reaction may be contained.

[0023] _{^{2M + mO 2- → M 2 O}} m + 2me - ··· (3) other polyhydric alcohols, such as such non as the solvent for the aqueous electrolyte solution of ethylene glycol and propylene glycol, the use of such as ethanol or methanol Can be. Further, as the solute, a sulfide soluble in the above-mentioned solvent, for example, ammonium sulfide, potassium sulfide, ammonium hydrogen sulfide, sodium sulfide, sodium hydrogen sulfide, or the like can be used, and these may be used in combination.

A report on a technique for forming an anodic sulfide film is described in Journal of Applied Physs.
ics 58 (1), 1985, p366. This report describes the MIS-FET (Metal-
Insulator-Semiconductor F
An anodic sulfide film is applied as a part of the gate insulating film in the field effect transistor, and is not applied to a drive device of a display device.

By forming the upper electrode on the non-linear resistance layer thus formed, the non-linear resistance element comprising the lower electrode, the non-linear resistance layer and the upper electrode is used as the lower electrode with the conductive film into which the impurities are mixed. Is completed.

Here, embodiments of the above embodiments will be described as Embodiments 1 to 4 as follows.

Example 1 In Example 1, a reflection type liquid crystal display device using a zinc anodic sulfide film containing iron as an impurity as a nonlinear resistance layer was manufactured.

FIG. 2 is a perspective view of several pixels of the display device of this embodiment. In FIG. 2, a pair of substrates 31 and 32 are opposed to each other with a display medium 34 made of liquid crystal interposed therebetween. The pixel electrode 25 is provided on one substrate (element side substrate) 31.
Are provided, the scanning wiring 22 is provided near the pixel electrode 25, and a non-linear resistance element for switching the pixel electrode 25 is formed. On the other substrate 32 (opposite substrate), data electrodes 35 are formed. Orientation films 33, 33 are formed on the display medium 34 side surfaces of both substrates 31, 32.

FIG. 3A shows one of the element-side substrates 31 of FIG.
FIG. 3B is a plan view showing a pixel portion, and FIG.
3 is a sectional view taken along line AA ′ of FIG. 3A and 3B,
Scanning wiring on an insulating substrate 21 made of glass or the like;
A scanning electrode 22 branched from the scanning wiring is formed, and a non-linear resistance layer 23 made of an anodic sulfide film is formed thereon.
Are formed. The scanning electrode 22 is formed of a zinc film containing iron as an impurity, and the non-linear resistance layer 23 is formed of the scanning electrode 2.
2 was anodized. An insulating film 24 having irregularities is formed on the non-linear resistance layer 23, and a reflective pixel electrode 25 is formed thereon. The pixel electrode 25 is electrically connected to the nonlinear resistance layer 23 at a contact hole formed in the insulating film 24. In this way, the non-linear resistance element is formed on the overlapping portion of the scanning electrode (lower electrode) 22, the non-linear resistance layer 23, and the pixel electrode (upper electrode) 25.

Hereinafter, a manufacturing process of the display device will be described. First, a procedure for manufacturing the element-side substrate 31 will be described.

First, a conductive thin film containing impurities is formed on a substrate 21 and is patterned into a predetermined shape to form a scanning wiring and a scanning electrode 22 branched from the scanning wiring. In this embodiment, an iron chip is placed on a zinc target, and sputtering is performed using argon gas, so that 50% of iron is deposited on a substrate 21 made of glass or the like.
A zinc film mixed with 0 ppm was formed to a thickness of about 300 nm. After a photoresist was applied thereon, the film was exposed and developed (photo step), and then etched by RIE (reactive ion etching) using a mixed gas plasma of carbon tetrafluoride and oxygen. Thereafter, the photoresist was peeled off, and the pattern formation of the scanning wiring and the scanning electrode 22 was completed.

Next, an anodic sulfide film serving as the non-linear resistance layer 23 is formed by using the electrolytic apparatus shown in FIG. At this time, it is necessary to form a cover such as by applying a plastic coat in advance so that anodic sulfide is not applied to the connection terminal portion with the drive driver extending from the scan electrode 22. In this embodiment, about 0.1 m
The substrate is immersed in an ethylene glycol solution containing an ol / l concentration to form an anode 13 and a platinum electrode is used as a cathode 14 to apply a voltage to the surface of the zinc film mixed with iron exposed on the substrate to form zinc sulfide. Was formed. As a method of applying a voltage, a constant voltage formation and a constant current formation can be mainly considered. In the present embodiment, the former method was used. An anodic sulfide film 23 made of zinc sulfide mixed with iron and having a thickness of about 100 nm was obtained by setting an appropriate voltage and energizing for about 3 hours.

Subsequently, the insulating film 24 is formed on the substrate in this state.
Is formed, and a non-linear resistance layer 23 and a pixel electrode 25 described later are formed.
A contact hole for making a connection with is provided. In this example, an insulating film was formed using an organic photosensitive resin. An organic photosensitive resin is applied to a thickness of about 400 nm on a substrate by spin coating, and then exposed and developed to form a contact hole.
Was formed. Thereafter, the surface of the insulating film 24 was lightly treated by RIE to form irregularities on the surface of the insulating film 24. Next, a conductive thin film made of a material having reflectivity is formed, and this is patterned to form the pixel electrode 25. In this embodiment, aluminum is sputtered to a thickness of about 200 n.
After the photo process, wet etching was performed using phosphoric acid or a mixed acid of phosphoric acid, nitric acid, and acetic acid. Thereafter, by removing the photoresist, a pixel electrode 25 connected to the upper portion of the nonlinear resistance layer 23 at the contact hole was formed. Since the unevenness is formed on the surface of the insulating film 24 provided below the pixel electrode 25, the unevenness is also formed on the surface of the pixel electrode 25, and the scattering effect of the reflective liquid crystal display device can be generated.

As described above, the superposed portion of the scanning electrode 22, the non-linear resistance layer 23 and the pixel electrode 25 becomes a non-linear resistance element, and the element in which an anodic sulfide film of zinc mixed with iron as an impurity is formed as the non-linear resistance layer 23. The side substrate 31 is manufactured.

Next, the procedure for manufacturing the opposing substrate 32 will be described. The opposing substrate 32 has a stripe-shaped data electrode 35 formed on the substrate. In this example, ITO having a thickness of about 200 nm was formed on a glass substrate by a sputtering method. After the photo step, the ITO film was etched with hydrobromic acid, and the photoresist was stripped to pattern the stripe-shaped data electrodes 35.

Thereafter, an alignment film 33 is applied to each of the side surfaces of the device-side substrate 31 and the counter-side substrate 32 formed as described above, on which elements and electrodes are to be formed, to perform an alignment process, whereby the alignment film 33 is formed. Both substrates 3 so that the surface faces inward
1 and 32 were bonded together. Thereafter, a liquid crystal 34 was injected into the gap between the two substrates, and the injection port was sealed to complete a reflective liquid crystal display device. In this example, a vertical alignment film was formed as the alignment film 33, and a nematic-cholesteric phase transition type guest-host liquid crystal was used as the liquid crystal.

FIG. 4 shows the IV characteristics of the device when the amount of iron as an impurity was changed. As can be understood from FIG. 4, the IV characteristics of the nonlinear resistance element can be changed by changing the amount of impurities mixed.

Therefore, in the display device of this embodiment, since a non-linear resistance element having a high on / off ratio using an anodic sulfide film is formed, a display device having a high contrast can be obtained. In addition, since the IV characteristics of the device can be changed by changing the amount of impurities mixed, the device can be easily driven even by using a nematic-cholesteric phase transition type guest-host liquid crystal having a high driving voltage. . Further, since the dielectric constant of the anodic sulfide film is low, voltage can be efficiently applied to the non-linear resistance element, and a high-definition display can be realized. Since this anodic sulfide film is a sulfide film having a dense and uniform film thickness and film quality with few pinholes, display unevenness due to variations in the characteristics of the nonlinear resistance element was small. Further, since the number of masks in the photo step is as small as about 3 and the non-linear resistance element can be manufactured in a step similar to the conventional anodic oxidation, the cost of the display device can be reduced.

In this embodiment, zinc is used as the material of the scanning wiring and the scanning electrode 22. However, any conductive material such as copper, cadmium, tantalum or the like that can be anodized can be used. . Further, in the present embodiment, iron was used as an impurity mixed into the conductive film. However, nickel, chromium, copper, silver, aluminum, indium or manganese may be used in addition to iron. They may be used in combination. Furthermore, a configuration may be adopted in which a part of the scanning wiring is used as a scanning electrode without separately forming the scanning electrode 22 (lower electrode), and the non-linear resistance layer 23 is formed thereon. Although the formation of the insulating film 24 can be omitted, when the insulating film 24 is formed, current leakage at the bent portion of the nonlinear resistance layer 23 and dielectric breakdown of the nonlinear resistance element can be prevented. As the material of the insulating film 24, a material other than the organic photosensitive resin may be used.
An inorganic film such as silicon nitride or silicon oxide may be formed. When a photosensitive resin is used, there is an advantage that the patterning process can be simplified. In addition, a configuration in which unevenness is not formed on the surface of the insulating film 24 is also conceivable, but when formed, the pixel electrode 25 of the reflection type liquid crystal display device can have a function of a scattering plate, and the reflection plate is externally attached to the substrate. Since there is no need to perform this operation, it is possible to reduce costs and obtain a bright display.

As the display medium 34, instead of using a nematic-cholesteric phase transition type guest-host liquid crystal, a display mode using a combination of a twisted or homogeneously oriented nematic liquid crystal and a polarizing plate may be used. In addition to the liquid crystal, a display medium such as electroluminescence, plasma, and electrochromic may be used. By changing the type and amount of impurities mixed in the conductive film and performing anodic sulfurization, it is possible to change the IV characteristics and drive a display device using various display media.

Example 2 In Example 2, a reflection type display device was constructed in which two non-linear resistance elements using an anodic sulfide film of zinc mixed with nickel as an impurity were connected in series with opposite polarities. .

FIG. 5A is a plan view showing one pixel portion of the element-side substrate, and FIG. 5B is BB ′ of FIG. 5A.
It is sectional drawing. 5A and 5B, an electrode (hereinafter, referred to as an anodized electrode) 42 to be subjected to anodizing treatment is formed in an island shape on an insulating substrate 41 made of glass or the like. A nonlinear resistance layer 43 made of a film is formed. The anodized electrode 42 is made of a zinc film mixed with nickel as an impurity, and the nonlinear resistance layer 43 is formed by anodizing the anodized electrode 42. An island-shaped insulating film 44 is formed on the non-linear resistance layer 43, and the scan electrode 45 and the pixel electrode 46
Are formed. Scan electrode 45 and pixel electrode 46
Is electrically connected to the nonlinear resistance layer 43 at a contact hole formed in the insulating film 44. One non-linear resistance element is formed on a superposed portion of an anodic sulfide electrode (lower electrode) 42, a non-linear resistance layer 43, and a scanning electrode (upper electrode) 45, and the other non-linear resistance element is an anodic sulfide electrode (lower electrode) 42 , The non-linear resistance layer 43 and the pixel electrode (upper electrode) 46.

The procedure for manufacturing the element-side substrate of this display device will be described below.

First, a conductive thin film containing impurities is formed on a substrate 41, and is patterned into a predetermined shape to form an anodic sulfide electrode 42. In this embodiment, a zinc film containing 100 ppm of nickel as an impurity is sputtered on a glass substrate 41 to a thickness of about 300 nm.
And a photo process and etching by RIE were performed. Thereafter, the photoresist was stripped to obtain a striped anodic sulfide electrode 42.

Next, an anodic sulfide film serving as the non-linear resistance layer 43 is formed by using the electrolytic apparatus as shown in FIG. In this embodiment, about 0.1 mol / l of sodium sulfide or the like is used.
The substrate is immersed in an ethylene glycol solution containing the concentration to form an anode 13, and a platinum electrode is used as a cathode 14 to apply a voltage, thereby forming a layer of zinc sulfide on the surface of the zinc film mixed with nickel exposed on the substrate. Formed. As a method of applying a voltage, constant current formation is used, and a current is applied for a suitable formation time at a constant current density of about 1 A / m ² to form an anode sulfide made of zinc sulfide mixed with nickel having a thickness of about 70 nm. The film 43 was obtained.

Thereafter, the striped anodic sulfide electrode 42
Is patterned in an island shape. In this embodiment, an island-shaped anodic sulfide electrode 42 having an anodic sulfide film 43 formed on the surface by a photo process, RIE, etching, and resist stripping is used.
Was patterned.

Subsequently, an insulating film 44 is formed so as to cover the anodic sulfide film 43, and a contact hole for connecting the anodic sulfide film 43 to a scanning electrode 45 and a pixel electrode 46 described later is provided. In this example, an organic photosensitive resin was applied to a thickness of about 300 nm by a spin coating method, and then exposed and developed to form an island-shaped insulating film 44 having a contact hole.

Next, a conductive thin film is formed so as to partially overlap the insulating film 44, and this is patterned to form a scanning electrode 4.
5 and the pixel electrode 46 are formed. In this example, aluminum was formed to a thickness of about 300 nm by a sputtering method, and after the photo process, wet etching was performed using hydrobromic acid. Thereafter, the photoresist was peeled off to form the scanning electrode 45 and the pixel electrode 46 connected to the upper part of the nonlinear resistance layer 43 in the contact hole.

As described above, the superposed portion of the anodized electrode 42, the non-linear resistance layer 43 and the scanning electrode 45 and the superposed portion of the anodized electrode 42, the non-linear resistance layer 43 and the pixel electrode 46 become a non-linear resistance element, An element-side substrate in which two non-linear resistance elements formed of an anodic sulfide film of nickel mixed with nickel as the non-linear resistance layer 43 were connected in series with opposite polarities, that is, in a back-to-back structure was manufactured.

The display device can be manufactured in the same manner as in Example 1 in the steps after the manufacture of the opposing substrate.

As described above, in the display device of this embodiment, since two non-linear resistance elements are connected in a back-to-back configuration between the scanning electrode 45 and the pixel electrode 47, the I-element of the element is connected. The asymmetry of the V characteristic was able to be improved.

In this embodiment, the IV characteristics of the device can be changed by changing the amount of nickel as an impurity. Further, although the two nonlinear resistance elements are connected in a back-to-back structure, the two nonlinear resistance elements may be connected in parallel with opposite polarities, that is, in a ring structure.

Example 3 In Example 3, a reflection type liquid crystal display device similar to that of Example 1 was produced except that an anodic sulfide film of zinc mixed with a plurality of impurities was used as a nonlinear resistance layer.

First, an iron chip and a chromium chip are placed on a zinc target, and sputtering is performed so that about 0.3% of iron and about 0.
A zinc film mixed with 1% was formed to a thickness of about 300 nm. Subsequent scan electrode patterning step, anodic sulfurizing step,
An element-side substrate was manufactured in the same manner as in Example 1 in the insulating film forming step and the pixel electrode forming step.

The IV characteristics of the obtained device are shown in FIG. At the same time, about 300 ppm of iron and about 100
62 shows the IV characteristics of a device produced by anodizing a zinc film containing about 100 ppm of copper and about 100 ppm of copper. As can be understood from FIG. 6, the IV characteristics of the nonlinear resistance element can be changed depending on the type and amount of impurities mixed in the conductive film.

The display device can be manufactured in the same manner as in Example 1 in the steps after the manufacture of the opposing substrate.

Example 4 In Example 4, a transmission type liquid crystal display device using an anodic sulfide film of zinc mixed with chromium as an impurity as a nonlinear resistance layer was manufactured.

FIG. 7A is a plan view showing one pixel portion of the element-side substrate 31, and FIG.
It is C 'sectional drawing. 7A and 7B, a scanning wiring and a scanning electrode 22 branched from the scanning wiring are formed on an insulating substrate 21 made of glass or the like, and a non-linear film made of an anodic sulfide film is formed thereon. The resistance layer 23 is formed. The scanning electrode 22 is made of a zinc film mixed with chromium as an impurity.
Is anodized. An insulating film 24 is formed on the non-linear resistance layer 23, on which an upper electrode 71 and a pixel electrode 72 connected to the non-linear resistance layer 23 via the upper electrode 71 are formed. The upper electrode 71 is made of the insulating film 2
4 is electrically connected to the non-linear resistance layer 23 in the contact hole. The non-linear resistance element is formed at a portion where the scanning electrode (lower electrode) 22, the non-linear resistance layer 23 and the upper electrode 71 overlap.

Hereinafter, a manufacturing process of the display device will be described.

First, a chromium chip was placed on a zinc target, and sputtering was performed using an argon gas to form a zinc film containing 300 ppm of chromium on the glass substrate 21 to a thickness of about 300 nm. Next, a patterning step of the scanning electrode 22 and an anodic sulfurizing step were performed in the same manner as in Example 1.

Subsequently, an organic photosensitive resin was applied on this substrate to a thickness of about 400 nm by spin coating, and then subjected to a photo process to form an insulating film 24 provided with a contact hole.

Next, a film of aluminum is formed to a thickness of about 300 nm by a sputtering method, and after the photo step, wet etching is performed using phosphoric acid or a mixed acid of phosphoric acid, nitric acid and acetic acid, and the photoresist is peeled off to remove the contact. The upper electrode 71 connected to the upper part of the nonlinear resistance layer 23 in the hole was formed.

Further, an ITO film having a thickness of about 200 nm is formed by a sputtering method, and is patterned so as to be in partial contact with the upper electrode 71, thereby forming a pixel connected to the upper part of the nonlinear resistance layer 43 via the upper electrode 71. The electrode 72 was formed.

As described above, the superposed portion of the scanning electrode 22, the non-linear resistance layer 23 and the upper electrode 71 becomes a non-linear resistance element, and an element in which an anodic sulfide film of zinc mixed with iron as an impurity is formed as the non-linear resistance layer 23. The side substrate 31 was produced.

The display device can be manufactured in the same manner as in Example 1 in the steps after the manufacturing of the opposing substrate.

Therefore, in the display device of this example, since a non-linear resistance element using the anodic sulfide film and having a high on / off ratio was formed, a display device with high resolution and high contrast could be obtained. Further, since the upper electrode 71 made of a material different from the pixel electrode is provided between the nonlinear resistance layer 43 and the pixel electrode 72, the pixel electrode material can be freely selected. In particular, in the case of a transmissive display device, a transparent conductive film (ITO) or the like is often used as the pixel electrode 72, which is advantageous in such a case.

In this embodiment, the IV characteristics of the device can be changed by changing the amount of chromium mixed as an impurity.

[0068]

As described above, according to the present invention, since the non-linear resistance layer of the non-linear resistance element is formed of an anodic sulfide film, the on / off ratio can be increased, and a display with high resolution and high contrast can be realized. . In addition, since the IV characteristics of the element can be easily changed by changing the type and amount of impurities mixed in the conductive thin film, a display device using various electro-optical display media is driven. be able to. Furthermore, since the dielectric constant of the non-linear resistance layer is low, the capacitance ratio of the non-linear resistance element to the liquid crystal is reduced, and a high-definition display can be obtained by efficiently applying a voltage to the element. In addition, since a sulfide film having a dense and uniform film thickness and quality with few pinholes can be formed by anodic sulfide, display unevenness due to variations in characteristics of the nonlinear resistance element can be suppressed. This non-linear resistance element can be manufactured by performing anodic sulphide in a process similar to anodic oxidation, and the number of masks in the photo process is smaller than that of the TFT, so that the cost of the display device can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of an electrolysis device used in an anodizing process of a display device according to an embodiment of the present invention.

FIG. 2 is a perspective view of several pixels of the display device according to the embodiment of the present invention.

FIG. 3A is a plan view of one pixel portion of an element-side substrate in the display device of Example 1, and FIG. 3B is a plan view of A in FIG.
It is -A 'sectional drawing.

FIG. 4 is a diagram showing IV characteristics of the device of Example 1.

5A is a plan view of one pixel portion of an element-side substrate in a display device according to a second embodiment, and FIG. 5B is a plan view of B in FIG.
FIG. 14 is a sectional view taken along the line B-B '.

FIG. 6 is a diagram showing IV characteristics of a device of Example 3.

FIG. 7A is a plan view of one pixel portion of an element-side substrate in a display device according to a third embodiment, and FIG. 7B is a plan view of C in FIG.
It is a -C 'sectional view.

8A is a plan view of one pixel portion of an element-side substrate in a conventional display device using a tantalum anodic oxide film, and FIG. 8B is a cross-sectional view taken along the line DD ′ of FIG. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Electrolyzer 12 Electrolyte 13 Anode 14 Cathode 21, 41 Glass substrate 22, 45 Scanning electrode 23, 43 Anodic sulfide film (non-linear resistance layer) 24, 44 Insulating film 25, 46, 72 Pixel electrode 31 Element side substrate 32 Opposite side Substrate 33 Alignment film 34 Liquid crystal (display medium) 35 Data electrode 42 Anodized electrode 71 Upper electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-250375 (JP, A) JP-A-7-325324 (JP, A) JP-A-62-224983 (JP, A) JP-A-3-324 35223 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1365

Claims (4)

(57) [Claims] A display medium having electro-optical characteristics is sandwiched between a pair of substrates, and one of the pair of substrates has
A pixel electrode for applying a voltage to the display medium is provided, at least one non-linear resistance element connected to the pixel electrode is provided for one pixel, and a scanning electrode for applying a selection signal to the non-linear resistance element is provided. The non-linear resistance element is connected to the non-linear resistance element, the non-linear resistance element has at least a non-linear resistance layer, and the non-linear resistance layer has a conductivity in which impurities are mixed in an electrolytic solution in which sulfur ions or ions containing sulfur atoms are present. A display device formed by applying a voltage using a film as an anode. 2. The display device according to claim 1, wherein the conductive film is made of zinc, copper, tantalum, or cadmium. 3. The display device according to claim 1, wherein the impurity is made of a material containing at least one of aluminum, iron, nickel, chromium, copper, silver, manganese, and indium. 4. The display device according to claim 1, wherein the display medium is made of a liquid crystal.