JP2003154598A - Electrode plate and liquid crystal display using the plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate having a conductive film which is thin, shows good conductivity, controls deterioration with the passage of time, and is excellent in preservation stability. SOLUTION: A thin silver film (11) is used as a base, and transparent, thin oxide films (12 and 13) made of a mixed oxide comprising indium oxide and an oxide of a metal element which forms substantially no solid solution with silver are formed on both sides of the film (11). The films (11, 12, and 13) are patterned into an electrode pattern in which their positions conform to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode plate and a liquid crystal display device using the same, and more particularly to an electrode plate provided with a multi-layer conductive film having excellent storage stability and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art An electrode plate having a transparent electrode film or a reflective electrode film provided on a substrate such as glass or plastic film is used for display electrodes of various display devices such as liquid crystal displays and display screens of display devices. Widely used as input / output electrodes for direct input.

For example, a transparent electrode plate used in a liquid crystal display device is provided on a glass substrate and a pixel portion on the glass substrate, and a color filter for coloring the transmitted light into red, green and blue for each pixel. A layer, a light-shielding film that is provided between the pixels on the glass substrate and between the pixels (inter-pixel portion) and prevents light transmission from the inter-pixel portion, and is provided on the entire surface of the color filter layer. The protective layer, the transparent electrode formed on the protective layer, and the alignment film formed on the transparent electrode form a main part. The transparent electrode is formed of a transparent conductive film which is formed by sputtering and etched into a predetermined pattern.

The transparent conductive film has high conductivity.
Therefore, ITO thin film in which tin oxide is added to indium oxide is used.
The membrane is widely used and its specific resistance is about 2.4 ×
10 ^-FourΩ · cm, which is usually applied as a transparent electrode
If the film thickness is 240 nm, the sheet resistance is about 10Ω
/ □.

Other than ITO, there are known tin oxide thin films, thin films in which antimony oxide is added to tin oxide (nesa films), thin films in which aluminum oxide is added to zinc oxide, and the like. Its conductivity is inferior to that of an ITO thin film, and its chemical resistance to water, acid, alkali, etc., or its water resistance is insufficient, so that it is not widely used.

By the way, in recent years, in the display device and the input / output device, it is required to increase the pixel density to display a fine screen, and accordingly, the transparent electrode pattern is required to be made fine. Is used, for example, 100μ
It is required to form the terminal portion of the transparent electrode with a pitch of about m. Further, in a liquid crystal display device, a method in which a liquid crystal driving IC is directly connected to a substrate (CO
In G), the wiring may have a narrow width portion of 20 to 50 μm, and it is required to have a high degree of suitability for etching processing and a high conductivity (low resistivity) which have not been heretofore available. The ITO material cannot meet such demands.

On the other hand, there is also a demand for a larger display screen. For such a large screen, a transparent electrode having a dense pattern as described above is formed so that a sufficient driving voltage can be applied to the liquid crystal. In order to do so, it is necessary to use a transparent conductive film having a high conductivity of 5Ω / □ or less as the transparent electrode. In addition to this, ST
In the case of performing a multi-gradation display of 16 gradations or more in a simple matrix drive type liquid crystal display device using N liquid crystal or the like, a lower sheet resistance of 3Ω / □ or less is required. The ITO material cannot meet such demands.

By the way, silver is the metal having the highest conductivity among metals, and it is possible to secure sufficient transparency and conductivity even when formed into a thin film. For example, at a thickness of 5 to 30 nm, silver has a transparency sufficient to transmit visible light and a thickness of about 2 to 5 nm.
The area resistivity of Ω / □ is shown. Therefore, silver is promising as a conductive material satisfying the above low resistivity requirement.

However, silver is damaged in about one week when left at room temperature in air. More specifically, silver reacts with a sulfur compound or water present in the air to form sulfides or oxides on the surface thereof, and deteriorates. Therefore, silver has a higher reflectance and a higher contrast than aluminum and can be displayed on a screen, but as a light-reflecting metal electrode or a light-reflecting plate of a reflective liquid crystal display device. Not commonly used.

On the other hand, Japanese Unexamined Patent Publication No. 63-173395.
Japanese Patent Laid-Open No. 1-126363 and Japanese Patent Laid-Open No. 2-37326.
Issue and 7th ICVM held in Japan in 1982
In JP-A No. 2004-242242, a transparent multilayer conductive film having a three-layer structure in which an ITO thin film or an indium oxide thin film (IO thin film) is formed on the front and back surfaces of a silver thin film is proposed. The transparent multilayer conductive film having the three-layer structure has a low area resistivity of about 5Ω / □,
Utilizing its high conductivity, application to the transparent electrode was expected.

However, even in the above-described conventional three-layered conductive film, the silver thin film is combined with moisture in the air invading from the lamination interface or the like after 2 weeks at room temperature in the air, and the surface thereof. However, there is a problem in that oxide defects are generated to cause spot-like defects, and when applied to a transparent electrode of a liquid crystal display device, for example, display defects are likely to occur on the display screen.

[0012]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrode plate provided with a conductive film which is a thin film and has good conductivity and which is less deteriorated with time and is excellent in storage stability. . Moreover, the further subject of this invention is providing the liquid crystal display device provided with such an electrode plate.

[0013]

According to the present invention, the above object is to provide a silver-based thin film made of a silver-based metal material having a first surface and a second surface facing the first surface, and the silver. A first transparent oxide thin film formed on a first surface of the silver-based thin film, and a second transparent oxide thin film formed on a second surface of the silver-based thin film. The second transparent oxide thin film independently includes a first metal oxide material made of indium oxide and a second metal made of an oxide of a metal element having substantially no solid solution region with silver. A multilayer conductive film formed of a mixed oxide containing an oxide material, wherein the silver-based thin film, the first transparent oxide thin film, and the second transparent oxide thin film have an electrode pattern aligned with each other. This is achieved by an electrode plate having a patterned multi-layer conductive film on a substrate.

Further, according to the present invention, the observer side electrode plate, the back side electrode plate arranged so as to face the observer side electrode plate, and the liquid crystal substance enclosed between these electrode plates are provided. There is provided a liquid crystal display device in which at least one of the plate and the back side electrode plate is composed of the electrode plate of the present invention.

Further, according to the present invention, an observer-side electrode plate provided with a transparent electrode, a back electrode plate provided opposite to the observer-side electrode plate and provided with a light-reflecting electrode, and a liquid crystal substance enclosed between these electrode plates. And a liquid crystal display device in which the back electrode plate is the multilayer conductive film of the present invention and is constituted by an electrode plate having a light-reflective conductive film.

The inventors of the present invention have conducted extensive studies to develop a multi-layer conductive film that exhibits good conductivity as a thin film and is excellent in storage stability without deterioration over time. As a transparent oxide thin film to be used, ITO thin film or I
It has been found that when a mixed oxide of indium oxide and a predetermined metal oxide such as cerium oxide or titanium oxide is used instead of the O thin film, the obtained multilayer conductive film has extremely high stability and moisture resistance. As a result of further research on the basis of this finding, the inventors of the present invention, as a transparent oxide thin film formed on both sides of the silver-based thin film, indium oxide,
It has been found that the intended purpose can be achieved by using a mixed oxide with an oxide of a metal element having substantially no solid solution region with silver. The electrode plate of the present invention is provided with the multilayer conductive film on a substrate in a state in which each thin film is patterned into an electrode pattern in which each thin film is aligned with each other.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a cross section of a multilayer conductive film 10 of a three-layer structure of the present invention provided on a substrate.

This multi-layer conductive film 10 includes a silver-based thin film 11 formed of a silver-based metal material, a first transparent oxide thin film 12 and a silver-based thin film 12 formed on a first surface (rear surface) of the silver-based thin film 11. The second transparent oxide thin film 13 is formed on the second surface (front surface) of the thin film 11. The multilayer conductive film 10 is formed on the substrate SUB.

Each of the first and second transparent oxide thin films 12 and 13 is composed of a first metal oxide material made of indium oxide and a metal element having substantially no solid solution region with silver. It is formed of a mixed oxide containing a second metal oxide material made of an oxide. The first and second
It is not necessary for the transparent oxide thin films 12 and 13 to be formed of the same material, but it is convenient to manufacture the multilayer conductive film 10 that they are formed of the same material.

In the present invention, the metal element having substantially no solid solution region with silver means a metal element having a solid solution amount with silver of 10 atom% or less at room temperature (25 ° C.). Examples of such metal elements include high melting point transition metals such as titanium (Ti), zirconium (Zr), tantalum (Ta) and niobium (Nb), lanthanide elements such as cerium (Ce),
Bismuth (Bi), Germanium (Ge), Silicon (S
Examples thereof include semimetals such as i), chromium (Cr), and the like. These metal elements can be used alone or in a combination of two or more.

Although the present invention is not bound by any theory, an indium oxide is mixed with an oxide of a metal element having substantially no solid solution region with silver on both surfaces of the silver-based thin film 11. By applying a mixed oxide, a silver-based thin film 1
It is believed that the solid solution of the silver element and the indium element in 1 and the migration of the silver element into the both transparent oxide thin films are prevented, thereby improving the temporal stability and moisture resistance of the multilayer conductive film.

The amount of the second metal oxide material is such that the metal element portion, that is, the metal element having substantially no solid solution region with silver, is the sum of the indium element portion of the first metal oxide material. The amount is preferably such that it accounts for 5% or more of the atomic weight. If the amount of the metal element that does not substantially have a solid solution region with silver is less than 5 atomic%, the effect of adding the second metal oxide material tends to be insufficient. It is further preferable that the amount of the metal element that does not substantially have a solid solution region with silver is 10 atomic% or more of the total atomic weight with indium.

On the other hand, the amount of the second metal oxide is such that the metal element portion, that is, the metal element having substantially no solid solution region with silver, is the atomic weight with the indium element portion of the first metal oxide. The amount is preferably 50% or less of the total of the above. When the amount of the metal element that does not substantially have a solid solution area with silver exceeds 50 atomic%, the resulting oxide thin film tends to have poor adhesion to the silver-based thin film. Also,
If such a large amount of element is present, it will be difficult to process the target used for film formation, which will be described in detail later, and the target will be easily cracked, and the film formation rate tends to decrease. The amount of the metal element having substantially no solid solution area with silver is more preferably 40 atom% or less, and most preferably 30 atom% or less of the total atomic weight of indium.

Both the first and second transparent oxide thin films 12 and 13 preferably have a thickness of 30 to 100 nm. When the thickness exceeds 100 nm, the reflected light on the surface of the oxide thin film and the reflected light on the surface of the silver-based thin film 11 interfere with each other to generate a color.

The silver-based thin film 11 may be formed of silver alone, but in order to prevent migration of silver, it is preferable to contain a different element other than silver that prevents migration of silver. Examples of such different elements include aluminum (Al), copper (Cu), nickel (N
i), cadmium (Cd), gold (Au), zinc (Z
n), magnesium (Mg), tin (Sn), indium (In), titanium (Ti), zirconium (Zr),
Cerium (Ce), silicon (Si), lead (Pb), and palladium (Pd). Of these elements, aluminum, copper, nickel, cadmium, gold, zinc and magnesium also have the effect of improving conductivity,
Tin, indium, titanium, zirconium, cerium and silicon also have the effect of improving the adhesion with the oxide thin films 12 and 13. Gold is particularly preferable because it contributes to the stabilization of the silver-based thin film 11.

Such a different element is preferably contained in the silver-based thin film 11 in a ratio of 0.1 to 3 atomic%. When the amount is less than 0.1 atom%, the migration preventing effect of silver is not sufficiently exerted, while on the other hand, 3 atom%
If it exceeds, the conductivity of the silver-based thin film 11 tends to decrease. In particular, when gold exceeds 3 atomic%, there is a tendency for etching residues to remain during etching. Gold is preferably contained in a ratio of 2.5 atomic% or less.

The silver-based thin film 11 preferably has a thickness of 2 nm or more in order to secure a satisfactory conductivity. In addition, the thickness of the silver-based thin film 11 depends on the multilayer conductive film 1
0 also depends on whether it is used as a transparent electrode or a light-reflecting electrode.

In FIGS. 5 and 6, a glass substrate (refractive index n = 1.5) is used as the substrate SUB, and a first and a second film having a refractive index n = 2.3 and a film thickness of 40 nm are formed on the glass substrate. A multilayer conductive film 10 having a structure in which a silver thin film 11 is sandwiched between transparent oxide thin films 12 and 13 is formed, and changes in reflectance R and transmittance T of the multilayer conductive film when the thickness of the silver thin film 11 is changed. In FIG. 5, the thickness of the silver thin film 12 is 10 nm (curve a), 15 nm (curve b), and 20 nm.
(Curve c) and 50 nm (curve d), the results are shown in FIG. 6, where the thickness of the silver thin film 11 is 50 nm (curve d),
75 nm (curve e), 100 nm (curve f) and 20
The result when 0 nm (curve g) is shown. Figure 5
In FIG. 6 and FIG. 6, the symbol T in parentheses next to the symbol indicating each curve indicates the transmittance, and the symbol R indicates the reflectance.

As can be seen from FIG. 5, when the thickness of the silver thin film 11 is up to 20 nm, the multi-layer conductive film has a transmittance of about 80.
The spectral characteristics of the transmission main body exhibiting at least%. Further, as can be seen from FIG. 6, when the thickness of the silver thin film 11 is 50 nm or more, the multilayer conductive film exhibits a reflection-based spectral characteristic showing a reflectance of about 80% or more. Especially the thickness of the silver thin film is 7
When the thickness is 5 nm or more, the reflectance of the multilayer conductive film is almost saturated and the transmittance is almost 0. At 200 nm, the reflectance is completely saturated.

Returning to FIG. 1, the multilayer conductive film 10 of the present invention.
Can be formed on a suitable substrate SUB using a deposition technique such as vacuum deposition, sputtering, or ion plating.

In particular, the transparent oxide thin films 12 and 13 are preferably produced by a sputtering technique. In particular, when the silver-based thin film 11 is present when the transparent oxide thin films are formed, DC sputtering is performed. More preferably, it is formed by a DC sputtering technique such as an RF-DC sputtering technique. When the high frequency sputtering is used, the substrate SUB is heated to cause migration of silver in the silver-based thin film 11 and not only the silver-based thin film 11 is spherically deformed but also oxygen plasma is generated. And the resulting spherical deformation of the silver-based thin film.

When the silver-based thin film 11 is present, the temperature of the substrate SUB is as low as possible, preferably 180 ° C. or less, more preferably in order to prevent migration of silver in the silver-based thin film. The temperature is set to around 120 ° C. This temperature may be room temperature.

In order to prevent the migration of silver in the silver-based thin film 11, it is preferable that water is not present in the sputtering apparatus.

Now, before forming the multi-layer conductive film 10 on the substrate SUB, the substrate SUB is cleaned. This purification can be performed by ion bombardment, reverse sputtering, ashing, ultraviolet cleaning, glow discharge treatment, or the like, depending on the type of material of the substrate SUB.

The target used for forming the transparent oxide thin films 12 and 13 by the sputtering technique is
A mixture of a powder of a first metal oxide material, namely indium oxide, and a powder of a second metal oxide material, ie powder of a metal element oxide, which has substantially no solid solution zone with silver, Add a binder such as paraffin, a dispersant, and a solvent (usually water) appropriately, and in a crushing / mixing device such as a ball mill, preferably until the oxide powder has an average particle size of 2 μm or less, that is, normally. Mix and grind for 10 to 40 hours. The fine powder mixture obtained is preferably press-formed under a pressure of 50 to 200 kg / cm @ 2 and fired in an oxygen atmosphere. By this firing, unnecessary components such as binder and dispersant are removed, and a dense sintered body is obtained. The firing temperature is 100 to obtain a dense sintered body.
Temperatures above 0 ° C are preferred. More preferably 1200 ° C
The temperature is 1800 ° C. or lower. The firing temperature is 180
If the temperature exceeds 0 ° C., the second metal oxide may be melted to cause an undesired reaction with the silver-based thin film 11 to reduce the conductivity of the multilayer conductive film or the light transmittance of the transparent oxide thin film. .

The target thus obtained can be shaped by grinding with a grinder or cutting with a diamond cutter or the like when the shape is inappropriate. The composition of the target is the desired transparent oxide thin film 12,
Same composition as 13. That is, a transparent oxide thin film having the same composition as the target is obtained. Note that a small amount of an oxide of an element such as tin, magnesium, zinc, gallium, aluminum, silicon, germanium, antimony, bismuth, or titanium may be added in order to adjust the conductivity, density, strength, or the like of the target. These additives may be introduced into the transparent oxide thin films 12 and 13 to be formed, but it is preferable to add them to the target in a small quantitative ratio that does not adversely affect them.

Since the silver-based thin film 11 has a high film formation rate and is the same as the transparent oxide thin films 12 and 13, it can be continuously formed with the transparent oxide thin films 12 and 13 by the same apparatus.
It is preferably manufactured by a DC sputtering technique.

The target used for producing the silver-based thin film 11 by sputtering is a target made of only silver or a target containing silver and a different element for preventing migration of silver. The target containing silver and a different element is preferably in the form of an alloy of silver and a different element, but may be in the form of embedding a chip of the different element in silver. The composition of the target is the same as that of the desired silver-based thin film 11.

Under the above-mentioned conditions, the first transparent oxide thin film 12, the silver-based thin film 11 and the second transparent oxide thin film 13 are sequentially formed on the substrate SUB, and then the multilayer film is heated to a temperature of 200 ° C. or higher. It is preferable to subject it to annealing treatment.
This annealing treatment further improves the conductivity of the multilayer film.

Transparent oxide thin films 12 and 13 and silver-based thin film 11
Any of the above can be preferably patterned by an etching treatment with a nitric acid-based etching solution. That is, after the multilayer conductive film 10 according to the present invention is formed on the substrate SUB, a commonly used resist is applied on the uppermost transparent oxide thin film 13, and the resist film is formed into a desired electrode pattern shape. To form. By etching the portion exposed from the resist pattern with a nitric acid-based etching solution, it is possible to pattern the three-layer thin films into a pattern shape in which they are aligned with each other.

As this etching solution, nitric acid can be used alone, but a mixed acid prepared by adding another acid such as hydrochloric acid, sulfuric acid or acetic acid to nitric acid may be used. The etching solution is preferably a mixed acid of sulfuric acid and nitric acid. Sulfuric acid preferentially dissolves the transparent oxide thin film, and nitric acid preferentially dissolves the silver-based thin film. In the case of this mixed acid of sulfuric acid and nitric acid, the sulfuric acid concentration is preferably higher than the nitric acid concentration. As a result, even though the transparent oxide thin film and the silver-based thin film have different side etching rates, the side etching amounts of these thin films can be matched and the pattern shapes of these thin films can be matched. Preferably, a mixed acid of sulfuric acid and nitric acid in a weight ratio of 100: 0.05 to 100: 50 can be used. The etching liquid includes ammonium sulfate, ammonium peroxysulfate, sulfates such as potassium sulfate, ammonium nitrate, nitrates such as cerium ammonium nitrate, chlorides such as sodium chloride and potassium chloride, oxidizers such as chromium oxide, cerium oxide and hydrogen peroxide, In addition, acetic acid, selenic acid, phosphoric acid, alcohol, surfactant and the like can be added as appropriate. Etching
It can be performed at a temperature of 30 ° C. for 40 to 60 seconds. By this etching process, an electrode pattern having a fine line portion with a minimum width of 20 to 50 μm can be formed with a side etching width of about 0 to 4 μm without disturbing the pattern shape.

When the multilayer conductive film is etched in this way, it is preferable to form a moisture-proof transparent thin film in order to protect the etched side end face from deterioration due to moisture. FIG. 2 shows the multilayer conductive film 10 of the present invention in a form protected by an electrically insulating moisture-proof transparent thin film 21.
In FIG. 2, each of the multilayer conductive films 10 formed on the substrate SUB is formed by the above-described etching, for example, in a stripe shape extending in a direction orthogonal to the plane of the drawing,
The entire surface including the etched side surface is covered with the moisture-proof transparent thin film 21.

The moisture-proof transparent thin film 21 is preferably formed of an oxide of a metal such as silicon, titanium, zirconium or tantalum because it has a high moisture-proof property. As such a metal oxide, a silicon oxide is particularly preferable.

The moisture-proof transparent thin film 21 is the transparent oxide thin film 1.
The total thickness of 3 and 3 is preferably 20 nm or more. In addition, the moisture-proof transparent thin film 21 is the transparent oxide thin film 1
The total thickness of 3 and 3 is preferably 100 nm or less. When the total thickness exceeds 100 nm, the reflected light on the surface of the protective film and the reflected light on the silver-based thin film 11 interfere with each other to be colored. The moisture-proof transparent thin film 21 is usually 20 nm to 70 nm.
Formed with a thickness of. The moisture-proof transparent thin film 21 can be formed by the same technique as that for forming the transparent oxide thin films 12 and 13. When the moisture-proof transparent thin film 21 is formed, the annealing treatment for improving the conductivity described above is
This is performed after forming the thin film 21.

The multilayer conductive film of the present invention can be used as a transparent electrode of various liquid crystal display devices or as a light-reflecting electrode. 1 shows the basic structure of the transparent electrode plate when the substrate SUB is transparent and the multi-layer conductive film 10 is transparent as will be described later with reference to FIGS. When the multilayer conductive film 10 is light-reflective as described above, it also indicates the basic structure of the light-reflective electrode plate.

FIG. 3 is a schematic sectional view showing an example of a transmissive liquid crystal display device. Transmission-type liquid crystal display device 30 shown in FIG.
Has a pair of transparent substrates 31 and 41 opposed to each other by a spacer SP at a predetermined interval. The transparent substrate 31 is located on the observer side, and the transparent substrate 41 is located on the back side thereof. A group of color filters C which are provided in pixel portions on the surface of the transparent substrate 31 of the observer side facing the transparent substrate 41 and which color the transmitted light into red, green and blue for each pixel.
A color filter layer 32 including F _{1 to} CF _n (hereinafter, these may be collectively referred to as a color filter CF)
Is formed, and the protective layer 33 is formed thereon. Usually, a light-shielding film (not shown) that prevents transmission of light from this portion is formed in the inter-pixel portion between pixels. On the protective layer 33, a plurality of stripe-shaped transparent electrodes (shown by 1 in FIG. 3) formed at predetermined intervals.
(Only one transparent electrode is visible) 34 is formed, and an alignment film 35 is formed thereon. A liquid crystal driving IC chip CP is provided in a portion of the transparent electrode 34 extending from the liquid crystal cell to the transparent substrate 31.

A polarizing film 36 is provided on the other surface of the transparent substrate 31.

On the surface of the back side transparent substrate 41 facing the transparent substrate 31, the transparent electrodes 42 extending in a direction orthogonal to the extending direction of the transparent electrode 34 are arranged at regular intervals.
_{1 to} 42 _n (hereinafter, these may be collectively referred to as a transparent electrode 42) are formed, and an alignment film 43 is formed thereon.

A polarizing film 44 is provided on the other surface of the transparent substrate 41.

The transparent substrates 31 and 41 are made of a light transmissive material. Examples of such a material include a glass plate, a plastic board, and a plastic film (including a polarizing film, a retardation film, a lens sheet, and also a material having a gas coat layer or a hard coat layer made of a hard synthetic resin). can do.

A liquid crystal material LC is enclosed in the space between the transparent substrates 31 and 41. Liquid crystal material LC
As a nematic liquid crystal, depending on its drive mode,
Ferroelectric liquid crystals, semi-ferromagnetic liquid crystals, cholesteric liquid crystals, smectic liquid crystals, homeotropic liquid crystals, etc., or any of those in which these liquid crystals are dispersed in a polymer substance can be used. The driving modes of the liquid crystal display device are twisted nematic (TN) mode, super twisted nematic (STN) mode, electric field control birefringence (ECB) mode, birefringence twisted nematic (BTN) mode, and optical compensation bend (OCB). ) Mode, guest-host mode, etc. When transmitting light (in the case of normally white TN and STN,
When the voltage is off, the liquid crystal has a refractive index (usually
Refractive index close to about 1.5 (eg, 1.5 to 1.
It is preferable to have 6). This is because when the liquid crystal material has such a refractive index, light that has entered it can be transmitted through the liquid crystal layer LC without being refracted or reflected.

FIG. 4 is a schematic sectional view showing an example of a reflective liquid crystal display device. The transmissive liquid crystal display device 50 shown in FIG.
Has a pair of substrates 51 and 61 that are opposed to each other by a spacer SP at a predetermined interval. The substrate 51 is
It is located on the observer side and is transparent. The substrate 51 is located on the back side and may be transparent or opaque.

On the surface of the observer-side transparent substrate 51 facing the substrate 61, stripe-shaped transparent electrodes 53 _{1 to} 53 _n are formed at predetermined intervals with a light-scattering film 52 interposed (hereinafter, these are collectively referred to as "collective"). And sometimes referred to as the transparent electrode 53)
Are formed, and the alignment film 54 is formed thereon.

A polarizing film 55 is provided on the other surface of the transparent substrate 51, and a light scattering film 56 is formed on the polarizing film 55.

The transparent substrate 51 can be formed of the same material as the transparent substrates 31 and 41 in the liquid crystal display device shown in FIG.

On the surface of the back side substrate 61 facing the transparent substrate 51, a plurality of stripe-shaped light-reflecting electrodes extending in a direction orthogonal to the extending direction of the transparent electrode 53 at predetermined intervals (see FIG. 4). So only one reflective electrode is visible) 62
Are formed, and the alignment film 63 is formed thereon.
A liquid crystal driving IC chip CP is provided in a portion of the light reflective electrode 62 extending from the liquid crystal cell onto the substrate 61.

When the rear substrate 61 is transparent,
It can be formed of the same material as the transparent substrates 31 and 41 in the liquid crystal display device 30 shown in FIG. 1, but in order to reduce specular reflection light, the surface of the material is subjected to an uneven treatment or a light scattering layer is formed. It is preferably opaque. The light scattering layer can be formed of a material in which a transparent powder having a refractive index different from this is dispersed in a synthetic resin (which usually has a refractive index of 1.3 to 1.7). The transparent powder has an average particle diameter of not more than the wavelength of light, and for example, in addition to granular resin powder (for example, fluororesin microcapsules), titanium oxide, zirconium oxide, lead oxide, aluminum oxide, silicon oxide. Examples thereof include inorganic powders such as magnesium oxide, zinc oxide, thorium oxide, cerium oxide, calcium fluoride, and magnesium fluoride. Cerium oxide, calcium fluoride, and magnesium fluoride are preferable as the transparent powder.

In the space between the substrates 51 and 61, a liquid crystal material LC similar to that described for the transmissive liquid crystal display device 30 is sealed. The driving mode of the liquid crystal display device can be each mode such as TN, STN, BTN, OCB, and guest host. Similarly, when light is transmitted (when the voltage is off in the case of normally white TN and STN liquid crystals)
In particular, the liquid crystal preferably has a refractive index (eg, 1.5 to 1.6) close to that of the transparent substrate (typically about 1.5). This is because when the liquid crystal material has such a refractive index, light that has entered it can be transmitted through the liquid crystal layer LC without being refracted or reflected.

Now, the multi-layered conductive film 10 of the present invention, whether it is protected by the protective film 21 shown in FIG. 2 or not, is used in the liquid crystal display device shown in FIGS. 3 and 4. In any case, it can be used as the transparent electrodes 34, 42, and / or 53. In that case, since the multilayer conductive film 10 needs to be transparent, as described above, the silver-based thin film 11 has a thickness of 20 nm.
It preferably has the following thickness.

In general, the color filters CF and the transparent substrates 31, 41, 51 have a refractive index of about 1.5, and the liquid crystal material LC has a refractive index of 1.5 to 1.6.
The thickness of the silver-based thin film 11 is 17 nm or less, particularly 4 to 1 in order to reduce the reflectance and increase the transmittance by setting the refractive index of the multilayer conductive film 10 close to those.
It is even more preferable that the thickness is 7 nm.

FIG. 7 shows a structure similar to that of the multilayer conductive film described with reference to FIG. 5, except that the transparent oxide thin films 12 and 13 have a refractive index of 2.3 and the thickness of the first transparent oxide thin film 12 is set. Is 35 nm, and the thickness of the second transparent oxide thin film 13 is 37 n.
m, and the thickness of the polyimide alignment film formed thereon is 40
nm and the refractive index of the liquid crystal is 1.5, the silver-based thin film 11
Thickness of 9 nm (curve a), 11 nm (curve b), 13
nm (curve c), 15 nm (curve d) and 17 nm
The results of simulating the transmittance (T) and the reflectance (R) of the multi-layer conductive film in the case where the curve (e) is changed are shown. In the figure, the symbol T in parentheses attached to the symbol for displaying a curve represents the transmittance, and the symbol R represents the reflectance. As can be seen from FIG. 7, when the thickness of the silver-based thin film is 17 nm or less, the transmittance is 90% or more and the reflectance is correspondingly low, but when the thickness of the silver-based thin film exceeds 17 nm, The transmittance of light at a wavelength of 550 nm tends to be less than 90%. In addition, if the thickness of the silver-based thin film is less than 4 nm, it is not preferable because it becomes island-shaped when the film is formed.

In addition, the silver-based thin film 11 is preferably formed of an alloy of silver and 0.1 to 3 atom% of copper or gold. Addition of copper or gold in such a proportion increases the transmittance of short wavelength light.

FIG. 8 shows a 0.1 nm copper-added silver thin film (AgC) having a thickness of 40 nm on a quartz substrate having a thickness of 1 mm.
u0.1 ) The results of measuring the spectral transmittance (T) of a thin film of silver (AgCu3) containing 3 atomic% of copper and a thin silver film are shown. As can be seen from this figure, when 0.1 to 3 atomic% of copper is added to silver, the transmittance of light having a short wavelength of less than 400 nm is significantly increased as compared with the case of only silver.

FIG. 9 shows the areal resistivity of silver-based thin films prepared by adding copper to silver at various ratios (atomic%). As shown in this figure, the area resistance increases as the amount of copper added increases, but when the amount of copper added is 3 atomic%, the film thickness 1
The area resistance of a silver-copper alloy of 0 nm is about 5 Ω / □, and the area resistance of a silver-copper alloy of 15 nm thickness is about 3 Ω / □, and the conductivity of copper is about this value. It is enough.

When gold is used instead of copper, the same results as those shown in FIGS. 8 and 9 are obtained.

In order to increase the transmittance of short wavelength light and long wavelength light, the transparent oxide thin films 12 and 13 are made of 2.1.
It is preferable to have the above refractive index. In order to have such a high refractive index, it is necessary to form a second transparent oxide thin film.
It is preferable to use an oxide of cerium, titanium, zirconium, hafnium and / or tantalum as the metal oxide material. As such a second metal oxide material, oxides of cerium and titanium are particularly preferable. As an example, the transparent oxide thin films containing cerium in the proportions of 20 atom%, 30 atom% and 40 atom% respectively have refractive indices of 2.17, 2.24 and 2.30, respectively. When the metal atom of the second metal oxide material is contained at 10 atom% or more, the transparent oxide thin film becomes amorphous or amorphous-like morphology, which enables patterning with good accuracy and isotropically optically. Therefore, the polarization plane can be maintained.

FIG. 10 shows that the multilayer conductive film of the present invention has a film thickness of 40.
liquid crystal material (refractive index 1.
FIG. 5 shows the calculated relationship between the refractive index, the light transmittance and the reflectance of the transparent oxide thin film of the multilayer conductive film of the present invention when it is assumed to be in contact with (5). In this case, the thickness of the transparent oxide thin film was optimized. In FIG. 10, a curve a shows a case where the refractive index is 2.0, and a curve b shows a case where the refractive index is 2.1.
The curve c shows the case where the refractive index is 2.2, the curve d shows the case where the refractive index is 2.3, and the curve e shows the case where the refractive index is 2.4. In FIG. 10, the symbol T in parentheses next to the symbol indicating each curve indicates the transmittance, and the symbol R indicates the reflectance. As can be seen from FIG. 10, when the refractive index of the transparent oxide thin film is 2.1 or more, the transmittance is improved and the reflectance is also decreased.

When the multilayer conductive film 10 of the present invention is used as the reflective electrode 62 of the reflective liquid crystal display device shown in FIG.
The multilayer conductive film 10 preferably includes the silver-based thin film 11 having a thickness of 50 nm or more, as described above, in order to exhibit good light reflectivity. Then, as described with reference to FIG. 6, the silver-based thin film 11 preferably has a thickness of 200 nm or less. Other matters are shown in Figs.
And as described with reference to FIG.

[0070]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 In this example, a transparent electrode plate having the multilayer conductive film of the present invention was produced.

This transparent electrode plate has the structure shown in FIG. 1, and has a transparent oxide thin film 12 having a thickness of 35 nm sequentially laminated on a glass substrate SUB having a thickness of 0.7 mm and a thickness of 14 n.
The transparent multilayer conductive film 10 was composed of a silver thin film 11 of m and a transparent oxide thin film 13 having a thickness of 35 nm.

The transparent oxide thin films 12 and 13 are both
Titanium oxide (TiO ₂ ) and indium oxide (In
It is formed of a mixed oxide with ₂ O ₃ ), and the content of titanium oxide is such that the titanium atom becomes 20 atom% of the indium atom in terms of metal element (oxygen atom is not counted).

This transparent multilayer conductive film was formed by the following method.

<Preparation of Target for Forming Transparent Oxide Thin Film> A small amount of paraffin was added as a binder to a mixture of indium oxide powder and titanium oxide powder each having an average particle diameter of about 2 μm in a predetermined ratio, and the mixture was mixed with a wet ball mill to obtain 24. Milled and mixed for hours.

Next, this mixed powder was filled in a predetermined mold, molded into a predetermined shape, and dried to remove water. This molded body was placed in an electric furnace and placed in an oxygen atmosphere at 155
It was baked at 0 ° C. for 10 hours to remove paraffin and sinter the molded body. This sintered body was ground with a surface grinder and shaped with a diamond cutter to obtain a desired target.

<Preparation of Target for Forming Silver Thin Film> Silver was melted under vacuum in a melting furnace, cast in a water-cooled mold, and cooled for 3 hours. The surface of the obtained cast body was ground by a surface grinder to shape the end faces to obtain a desired target.

<Washing of Glass Substrate> The surface of the glass substrate was sequentially washed with an alkaline surfactant and water. This was housed in a vacuum chamber of a DC magnetron sputtering device, subjected to a plasma treatment called reverse sputtering, and further washed.

<Preparation of Multilayer Conductive Film> Without removing the glass substrate from the vacuum chamber, the transparent oxide thin film 12 was first formed by the sputtering method with the glass substrate kept at room temperature. By the way,
A silver thin film 11 was sequentially formed using the silver target, and then a transparent oxide thin film 13 was sequentially formed using the transparent oxide target again.

Next, an electrode-shaped resist film is formed on the transparent oxide thin film 13, and the portion exposed from the resist film is treated at 30 ° C. with a mixed acid etching solution containing 60.4% by weight of sulfuric acid and 3% by weight of nitric acid. Then, the thin films of the above three layers were patterned into electrode shapes while being aligned with each other by etching for about 40 seconds. Then, this was annealed at 220 ° C. for 1 hour to form a transparent multilayer conductive film.

The sheet resistance of the transparent multi-layer conductive film thus obtained was about 2.7 Ω / □. The visible light transmittance is shown in Table 1 below.

For comparison, the above-mentioned transparent oxide thin films 12, 1
Table 1 also shows the visible light transmittance of a transparent multilayer conductive film having a three-layer structure in which an IO thin film is applied instead of No. 3.

When the transparent electrode plate of Example 1 was allowed to stand in the air for 8 weeks and observed, no change in appearance was observed on the surface of the transparent multilayer conductive film 10. On the other hand, in the transparent multi-layered conductive film having a three-layer structure in which IO was applied instead of the above-mentioned transparent oxide thin film, many spots were generated within 2 weeks after storage.

As described above, the transparent multilayer conductive film according to this example has a higher visible light transmittance on the long wavelength side as compared with the conventional example, has a uniform and high light transmittance in the entire visible region and is extremely high. It was confirmed that it has a high electric conductivity and is excellent in moisture resistance.

Example 2 In this example, the transparent oxide thin films 12 and 13 were formed in the same manner as in Example 1 except that the transparent oxide thin films 12 and 13 were formed of a mixed oxide of titanium oxide (TiO 2), cerium oxide (CeO 2), and indium oxide. An electrode plate was produced. In terms of metal elements (oxygen atoms are not counted), the content of titanium oxide is such that titanium atoms are 16 atom% of indium atoms, and the content of cerium oxide is 4% of cerium atoms are indium atoms.
The amount is atomic%.

The sheet resistance of the obtained transparent multilayer conductive film 10 was about 2.7 Ω / □. The visible light transmittance is also shown in Table 1.

When this transparent electrode plate was allowed to stand in the air for 8 weeks and observed, no change in appearance was observed on the surface of the transparent multi-layer conductive film as in Example 1.

[0088]

[Table 1]

Example 3 The thickness of both transparent oxide thin films 12 and 13 was set to 39 nm without changing the composition, and the silver-based thin film 11 was formed to a thickness of 14 nm from a silver-copper alloy containing 0.4 atom% of copper. A transparent multilayer conductive film was formed on the substrate in the same manner as in Example 1 except that
Annealing treatment was performed at 0 ° C. for 1 hour.

The sheet resistance of the transparent multilayer conductive film thus obtained was about 2.8 Ω / □. The visible light transmittance is shown in Table 2 below.

[0091]

[Table 2]

As described above, the transparent multilayer conductive film according to Example 3 has a high visible light transmittance on the short wavelength side, a uniform light transmittance in the entire visible region, and an extremely high conductivity. Moreover, it was confirmed that it has excellent moisture resistance.

Example 4 In this example, a transparent electrode plate having the multilayer conductive film of the present invention was produced.

This transparent electrode plate has the structure shown in FIG. 1, and has a transparent oxide thin film 12 of 39 nm in thickness sequentially laminated on a glass substrate SUB of 0.7 mm in thickness and a thickness of 10 n.
m silver alloy thin film 11 and 39 nm thick transparent oxide thin film 1
And a transparent multi-layer conductive film 10 composed of 3 and 3.

The transparent oxide thin films 12 and 13 are both
It is formed of a mixed oxide of titanium oxide (TiO2), cerium oxide (CeO2), and indium oxide. The content of titanium oxide is 19 indium atoms when the titanium atoms are indium atoms in terms of metal elements (oxygen atoms are not counted). The amount of cerium oxide is 1 atomic% of indium atoms. Also,
The silver alloy silver-based thin film 11 was formed of a silver-copper alloy containing 0.3 atom% of copper.

This transparent multilayer conductive film 10 was formed by a method similar to that of Example 1, and the sheet resistance after annealing for 1 hour at 270 ° C. was about 4.6 Ω / □. . In addition, when the visible light transmittance was measured, it was 90% over the entire visible region of wavelength 400 to 700 nm.
The above high light transmittance is exhibited, and in particular, as compared with the case of using a thin film of silver alone, the short wavelength side of 500 nm or less and 550 n
It was confirmed that the light transmittance was remarkably increased on both the long wavelength side of m or more.

Example 5 In this example, a transparent electrode plate having the multilayer conductive film of the present invention was produced.

This transparent electrode plate has the structure shown in FIG. 1, and a transparent oxide thin film 12 having a thickness of 33 nm and a thickness of 15 are sequentially stacked on a glass grave plate SUB having a thickness of 0.7 mm.
The transparent multi-layer conductive film 10 includes a silver-based thin film 11 having a thickness of nm and a transparent oxide thin film 13 having a thickness of 34 nm.

The transparent oxide thin films 12 and 13 are both
A mixed oxide in which cerium oxide was added to indium oxide at a ratio of cerium atoms to 30 atom% of indium atoms in terms of metal elements (oxygen atoms were not counted) was obtained.
The silver-based thin film 11 is a silver-containing thin film containing 1.0 atomic% of
Made of gold alloy.

This transparent multilayer conductive film was prepared by a method similar to that of Example 1, and was annealed at 220 ° C. for 1 hour.

The sheet resistance of the transparent multi-layer conductive film 10 thus obtained was about 2.9 Ω / □. The visible light transmittance is shown in FIG.

This pattern-formed transparent multilayer conductive film 10
After maintaining for 5 hours under conditions of 60 ° C. and 95% relative humidity, the surface was observed, but no change in appearance was observed. The refractive index of the transparent multilayer conductive film formed of this mixed oxide was 2.24.

Example 6 The transparent multilayer conductive film 10 having the structure shown in FIG. 1 was formed on the glass substrate SUB by the same structure and manufacturing method as in Example 5. However, the thickness of the silver-based thin film 11 is the same as 15 nm, but the ratio of gold in the silver-gold alloy forming the silver-based thin film 11 is 0.1.
To 4 atom%. Table 3 shows the sheet resistance and the light transmittance at 610 nm of each transparent multilayer conductive film. The sheet resistance and light transmittance are values measured after annealing at 220 ° C. for 1 hour.

[0104]

[Table 3]

As shown in Table 3, the transparent multi-layer conductive film having the silver-based thin film 11 formed of the silver alloy containing 4 atomic% of gold also shows an extremely low area resistance value of 4.9 Ω / □. The light transmittance of each transparent multilayer conductive film after the annealing treatment at 220 ° C. for 1 hour was 90% or more at a wavelength of 545 nm (green). At a wavelength of 610 nm (red), 89% with 4 atomic% of gold added
And the light transmittance is a little lower. In terms of light transmittance,
Addition of gold in excess of 4 atom% is less preferred.

Further, each transparent multilayer conductive film was stored in a high temperature and high humidity atmosphere of 60 ° C. and a relative humidity of 95%, and the change in appearance after 200 hours was observed. In addition, when the appearance of each transparent multilayer conductive film stored under the same conditions for 500 hours was examined, there was no change in the appearance in the case where gold was added at a ratio of 0.4 atom% or more.
Minute stains were generated in the samples to which 0.1 atom% and 0.2 atom% of gold were added. All were better than the multilayer conductive film having a silver-copper alloy containing copper as a silver-based thin film.

Example 7 In this example, a transparent electrode plate having the multilayer conductive film of the present invention was produced. This transparent electrode plate has the structure shown in FIG. 1, a 39 nm thick transparent oxide thin film 12 sequentially laminated on a 0.7 mm thick glass substrate SUB, and a 15 nm thick transparent oxide thin film 12.
The transparent multilayer conductive film 10 including the silver thin film 11 and the transparent oxide thin film 13 having a thickness of 40 nm was provided, and the transparent multi-layer conductive film 10 was manufactured by a method similar to that of Example 1.

The transparent oxide thin films 12 and 13 are both
It was formed of a mixed oxide containing 66 atomic% of indium, 32.5 atomic% of cerium, 1.0 atomic% of tin, and 0.5 atomic% of titanium in terms of metal element (not counting oxygen atoms). The silver-based thin film 11 was formed of a silver-gold-copper ternary alloy consisting of 98.4 atomic% silver, 0.8 atomic% gold and 0.8 atomic% copper.

This transparent multilayer conductive film shows a sheet resistance of 2.8 Ω / □ after annealing at 220 ° C. for 1 hour.
The light transmittance at 50 nm was about 97%.

When this transparent multilayer conductive film was stored for 200 hours under the conditions of high temperature and high humidity of 60 ° C. and relative humidity of 95%, no stain was generated and a good appearance was exhibited.

The multilayer conductive film in which the silver-based thin film is formed of a silver-gold-copper ternary alloy in this way is a silver-gold binary alloy containing gold in an amount corresponding to the total amount of gold and copper. Compared with the multilayer conductive film formed with a silver-based thin film, it tends to have a lower sheet resistance and also tends to have improved moisture resistance. Also,
Since gold is about 100 times more expensive than silver, it is possible to reduce the amount of gold added and reduce the cost.

Example 8 In this example, a transparent electrode plate having the multilayer conductive film of the present invention was produced.

This transparent electrode plate has the structure shown in FIG. 2 and is laminated on the glass substrate SUB having a thickness of 0.77 mm so as to be aligned with each other in the shape of an electrode and the transparent oxide thin film 12 having a thickness of 40 nm. And a silver thin film 11 having a thickness of 14 nm and a thickness of 4
A plurality of transparent multi-layered conductive films 10 each composed of a 0 nm transparent oxide thin film 13 are provided, and all of these transparent multi-layered conductive films 10 are uniformly covered to protect the surface and side end faces thereof.
It has a 0 nm electrically insulating moisture-proof transparent thin film 21.

The transparent oxide thin films 12 and 13 are both
A mixed oxide in which zirconium oxide was added to indium oxide at a ratio of 10 at% zirconium element in terms of metal element (not counting oxygen atoms) was obtained. The moisture-proof transparent thin film 21 is made of silicon oxide (SiO2). Each transparent multilayer conductive film (transparent electrode) 10 has a stripe shape having a width of 200 μm and has a pitch of 21.
It is formed with 0 μm and an interval of 10 μm.

In this transparent electrode plate, the transparent oxide thin film 12, the silver-based thin film 11 and the transparent oxide thin film 13 were formed on the substrate SUB according to the method of Example 1, and after being etched into a stripe pattern, moisture resistance was obtained. After forming the transparent thin film 21 by film formation, an annealing treatment was performed at 200 ° C. for 30 minutes. Each transparent electrode had a fine width portion having a width of 20 nm or less.

The area resistance of the obtained transparent electrode is about 2.8Ω.
It was / □.

When this transparent electrode plate was observed by leaving it in the air for one month, no change in appearance was observed on the surface of the transparent electrode.

For comparison, a silver thin film was formed on a glass substrate and left for one month in the air. The surface was discolored and many spots were observed.

As described above, since deterioration of the silver-based thin film over time is prevented and its storage stability is improved, it is possible to stably manufacture a liquid crystal display device or the like having no display defect caused by a sulfur compound or moisture in the air. Have an effect.

Example 9 In this example, the transmissive liquid crystal display device shown in FIG. 3 was produced. Each of the transparent electrodes 42 ₁ to 42 _n has a width of 10
It has a stripe shape of 0 μm and is provided with a pitch of 110 μm. The transparent electrode 34 has a stripe shape with a width of 320 μm, and extends at a pitch of 330 μm on the color filter CF in a direction orthogonal to the extending direction of the transparent electrode 42. Each transparent electrode had a fine width portion having a width of 20 nm or less.

Each of the transparent electrodes 34 and 42 comprises a transparent oxide thin film 12 having a film thickness of 38 nm, a silver-based thin film 11 having a film thickness of 14 nm, and a transparent oxide thin film 13 having a film thickness of 41 nm.

The transparent oxide thin films 12 and 13 have a refractive index of 2.
2 and both are composed of a mixed oxide of indium oxide and cerium oxide, and the composition thereof is 25 atom% of cerium in terms of metal atoms of indium and cerium. The silver-based thin film 11 is formed of a silver-copper alloy containing 0.8 atomic% of copper.

These transparent electrodes 34 and 42 are formed by the same method as in Example 1 and are formed by etching, and are annealed at 220 ° C. for 1 hour before being assembled in a liquid crystal cell. , Then the sheet resistivity is about 3Ω
It was / □.

As a comparative example, with the same film thickness as this example,
Comparing the brightness with a liquid crystal display device using a three-layer transparent electrode made of a transparent oxide thin film of ITO (refractive index of about 2), it is found that this embodiment is approximately 10% brighter and has a higher display quality. there were.

Further, the transparent electrode of the present example does not change with time, and in terms of liquid crystal driving, there is no crosstalk as compared with the conventional transparent electrode of ITO single layer (8Ω / □).
The display quality was extremely high.

Example 10 In this example, a light-reflective electrode plate was prepared.

This light-reflective electrode plate has the structure shown in FIG. 1, and is formed by sequentially laminating a transparent oxide thin film 12 having a thickness of 10 nm and a thickness of 120 on a glass substrate SUB having a thickness of 0.7 mm.
A light-reflective conductive film (electrode) 10 including a silver-based thin film 11 having a thickness of 70 nm and a transparent oxide thin film 13 having a thickness of 70 nm is provided.

The transparent oxide thin films 12 and 13 are both
It is formed of a thin film of indium oxide containing zirconium oxide, and the content of zirconium oxide is such that zirconium atoms become 20 atom% with respect to indium atoms in terms of metal element (oxygen atoms are not counted). The silver-based thin film 11 is formed of a silver-copper alloy containing 1 atomic% of copper.

Transparent oxide thin film 1 according to the method of Example 1
2. Form a silver-based thin film 11 and a transparent oxide thin film 13,
After etching, annealing treatment was performed at 220 ° C. for 1 hour.

The spectral reflectance of the light-reflecting conductive film thus obtained was compared with that of aluminum as 100%, and the results are shown in FIG.

For comparison, a light-reflecting conductive film was prepared using a silver-only thin film containing no copper as the silver-based thin film. This light-reflective conductive film exhibited a higher light reflectance than aluminum over almost the entire visible region, but exhibited a low light reflectance of about 86% in the visible region on the short wavelength side of about 450 nm.

On the other hand, the light-reflective conductive film of this embodiment using the silver alloy thin film containing copper is higher than aluminum even in the visible region on the low wavelength side of about 450 nm as shown in FIG. The light reflectance is shown, and it can be confirmed that the light reflectance is uniform and high in the entire visible region.

The light-reflective conductive film according to this example was allowed to stand in the air for 2 months, and the change in its light-reflecting property was inspected. As a result, no change in appearance was observed on the surface of the silver-based thin film, and there was no change in light reflectance.

Example 11 Except that indium oxide thin films containing titanium oxide were used as the transparent oxide thin films 12 and 13 and silver-copper alloy thin films containing various amounts of copper were used as the silver-based thin films. ,
In the same manner as in Example 10, a light-reflecting conductive film was produced on a glass substrate. The content of titanium oxide in the transparent oxide thin films 12 and 13 is such that titanium atom is 20 atom% with respect to indium atom.
Is the amount.

The light reflectance of 450 nm visible light was measured for each of the various light-reflective conductive films thus obtained. The result is shown in FIG.

From FIG. 13, the visible light reflectance on the short wavelength side of about 450 nm fluctuates depending on the copper content, and when the light reflectance of aluminum is set to 100%, a copper content of 0% corresponds to that of aluminum. About 86% of light reflectance, about 97% at 0.1 atom% copper content, 1 to 3 copper content
It was confirmed that the maximum value reached about 102 to 104% in atomic%, and decreased to about 97% when the copper content was 7 atomic%.

Example 12 In this example, a light reflecting electrode plate was prepared in the same manner as in Example 10. This light-reflective electrode plate has a structure shown in FIG. 2 and a 10-nm-thick transparent oxide thin film 12 that is laminated in the shape of an electrode on each 0.7-mm-thick glass substrate SUB. A plurality of multilayer light-reflective conductive films 10 each including a light-reflective silver-based thin film 11 made of silver having a thickness of 120 nm and a transparent oxide thin film 13 having a thickness of 70 nm; A 35 nm thick moisture-proof transparent thin film that covers and protects the surface and side end faces.
Equipped with.

The transparent oxide thin films 12 and 13 are both
It is formed of a mixed oxide in which zirconium oxide is added to indium oxide at a ratio of 3 atom% of zirconium atom in terms of metal element (not counting oxygen atoms). The moisture-proof transparent thin film 12 is made of silicon oxide. Each light-reflecting electrode has a stripe shape with a width of 200 μm, and is arranged with a pitch of 210 μm and an interval of 10 μm. Each light-reflective electrode had a fine width portion having a width of 20 nm or less, which was a wiring pattern for mounting the liquid crystal driving IC.

This light-reflecting electrode was formed by forming the transparent oxide thin film 12, the silver-based thin film 11 and the transparent oxide thin film 13 according to the method of Example 1, patterning by etching, and then forming a moisture-proof transparent film. A thin film 21 is formed, and subsequently,
It was formed by annealing at 220 ° C. for 30 minutes.

The light-reflecting electrode plate thus obtained was allowed to stand in the air for one month and the change in its light-reflecting characteristics was examined.
As a result, no change in appearance was observed on the surface of the light-reflective silver thin film 11, and there was no change in light reflectance.

Example 13 In this example, a reflective liquid crystal display device having the structure shown in FIG. 4 was produced.

In this liquid crystal display device, the transparent electrode 53
₁ to 53 _n each have a stripe shape with a width of 100 μm, and are arranged on the light scattering film 52 at a pitch of 110 μm. In addition, each light reflective electrode 62 has a width 320
It has a stripe shape of μm and has a pitch of 330 μm and extends in a direction orthogonal to the extending direction of the transparent electrode 53. The transparent electrode 53 and the light reflective electrode 62 each had a fine width portion having a width of 20 nm or less.

The transparent electrode 53 includes a transparent oxide thin film 12 having a thickness of 40 nm, a silver-based thin film 11 having a thickness of 15 nm, and a thickness of 40 n.
m transparent oxide thin film 13.

The light-reflective electrode 62 is in contact with the rear substrate 61, which is a glass substrate, and has a thickness of 10 nm.
And a silver-based thin film 11 having a thickness of 150 nm and a transparent oxide thin film 13 having a thickness of 40 nm.

In both the transparent electrode 53 and the light-reflective electrode 62, the transparent oxide thin films 12 and 13 are mixed oxides of indium oxide containing 30 at% of cerium oxide in terms of metal element, and have a refractive index of 2. It was .24. In both the transparent electrode 53 and the light reflective electrode 62, the silver-based thin film 11 was formed of a silver-copper alloy containing 0.8 atomic% of copper.

As a comparative example, an area resistance of 8 Ω / □ and a film thickness of 2
Forming electrodes 53 and 62 with 40 nm ITO,
Further, a liquid crystal display device similar to that of this example was produced except that an aluminum reflector was provided on the back surface (outside) of the back substrate 61. When comparing the brightness of the liquid crystal display devices of the present example and the comparative example, it was found that the present example was brighter by about 10% and the display quality was higher. Also, in the display device of the comparative example, shadowing was observed in the displayed characters,
No shadowing was observed in the display device of this example. Further, in the display device of the comparative example, the displayed characters were reflected on the aluminum reflection plate and the characters appeared double, but in the display device of the present example, such a phenomenon did not occur.

[0147]

As described above, according to the present invention, an electrode plate provided with a conductive film which exhibits good conductivity in a thin film, has little deterioration over time, and is excellent in storage stability, and a liquid crystal using the same. A display device is provided. This electrode plate is useful not only as a transparent electrode plate of a liquid crystal display device but also as a light reflective electrode plate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer conductive film of the present invention formed on a substrate.

FIG. 2 is a cross-sectional view of a multilayer conductive film of the present invention in a form protected by a protective film.

FIG. 3 is a sectional view schematically showing a transmissive liquid crystal display device to which the multilayer conductive film of the present invention can be applied.

FIG. 4 is a sectional view schematically showing a reflective liquid crystal display device to which the multilayer conductive film of the present invention can be applied.

FIG. 5 is a graph showing the relationship between the thickness of the silver-based thin film in the multilayer conductive film of the present invention and the light transmittance and light reflectance of the multilayer conductive film.

FIG. 6 is another graph showing the relationship between the thickness of the silver-based thin film in the multilayer conductive film of the present invention and the light transmittance and light reflectance of the multilayer conductive film.

FIG. 7 is yet another graph showing the relationship between the thickness of the silver-based thin film in the multilayer conductive film of the present invention and the transmittance and reflectance of the multilayer conductive film.

FIG. 8 is a graph showing the relationship between the amount of copper added to the silver-based thin film and the light transmittance of the multilayer conductive film.

FIG. 9 is a graph showing the relationship between the amount of copper added to the silver-based thin film and the areal resistivity of the multilayer conductive film.

FIG. 10 is a graph showing the relationship between the refractive index of the transparent oxide thin film and the light transmittance and light reflectance of the multilayer conductive film.

FIG. 11 is a graph showing the light transmittance of the multilayer conductive film manufactured in the example of the present invention.

FIG. 12 is a graph showing the light transmittance of a multilayer conductive film manufactured according to another example of the present invention.

FIG. 13 is a graph showing the relationship between the amount of copper added to the base conductive film of the multilayer conductive film manufactured in still another example of the present invention and the light reflectance.

[Explanation of symbols]

11 ... silver-based thin film 12, 13 ... transparent oxide thin film 21 ... moisture-resistant transparent film 31, 41, 51, and 61, SUB ... substrate _{34,42 1 ~42 n, 53 1 ~53} n ... transparent electrode 36, 44, 55 ... Polarizing films 52, 56 ... Light scattering film 62 ... Light-reflecting electrodes CF _{1 to} CF _n ... Color filter LC ... Liquid crystal material

   ─────────────────────────────────────────────────── ─── Continued front page    (31) Priority claim number Japanese Patent Application No. 7-223403 (32) Priority date August 31, 1995 (August 31, 1995) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 7-223405 (32) Priority date August 31, 1995 (August 31, 1995) (33) Priority claiming country Japan (JP) (72) Inventor Osamu Koga             1-5-1 Taito, Taito-ku, Tokyo Toppan stamp             Imprint Co., Ltd. (72) Inventor Koji Imayoshi             1-5-1 Taito, Taito-ku, Tokyo Toppan stamp             Imprint Co., Ltd. (72) Inventor Katsutaka Dochi             1-5-1 Taito, Taito-ku, Tokyo Toppan stamp             Imprint Co., Ltd. F term (reference) 2H092 HA03 HA04 HA05 NA11 NA30                 4F100 AA17B AA17C AA20C AA21C                       AA22C AA26C AA27C AB09A                       AB10A AB11A AB12A AB16A                       AB17A AB18A AB21A AB24A                       AB31A AB33A AG00 BA03                       BA10B BA10C EH662 GB41                       JG01 JN01B JN01C JN18B                       JN18C YY00B YY00C

Claims (15)

[Claims] 1. A silver-based thin film made of a silver-based metal material having a first surface and a second surface opposite to the first surface, and a first surface formed on the first surface of the silver-based thin film. Transparent oxide thin film,
And a second transparent oxide thin film formed on the second surface of the silver-based thin film, wherein the first and second transparent oxide thin films each independently include a first indium oxide first film.
Which is a mixed oxide containing a metal oxide material of No. 2 and a second metal oxide material made of an oxide of a metal element having substantially no solid solution region with silver. An electrode plate having a multilayered conductive film, on which a silver-based thin film, a first transparent oxide thin film, and a second transparent oxide thin film are patterned in an electrode pattern aligned with each other, on a substrate. 2. A metal element having no solid solution zone with silver is titanium, zirconium, tantalum, niobium, hafnium,
Cerium, bismuth, germanium, silicon, chromium,
The electrode plate according to claim 1, which is selected from the group consisting of and a combination of two or more thereof. 3. The electrode plate according to claim 1, wherein the metal element having no solid solution area with silver occupies 5 to 50 atomic% of the total atomic weight of the indium element. 4. The electrode plate according to claim 1, wherein the silver-based metal material is an alloy of a silver element and a different element that prevents migration of the silver element. 5. The electrode plate according to claim 4, wherein the different element is selected from the group consisting of aluminum, copper, nickel, cadmium, gold, zinc, magnesium and combinations of two or more thereof. 6. The electrode plate according to claim 4, wherein the different element is selected from the group consisting of tin, indium, titanium, cerium, silicon and combinations of two or more thereof. 7. The electrode plate according to claim 1, wherein the silver-based thin film has a thickness of 2 to 20 nm. 8. The silver-based metal material is 0.1 to 3 atom%.
8. The electrode plate according to claim 7, which contains the copper or gold. 9. The electrode plate according to claim 8, wherein each of the first and second transparent oxide thin films has a high refractive index of 2.1 or more. 10. The metal element having substantially no solid solution zone with silver is selected from the group consisting of cerium, titanium, zirconium, hafnium, tantalum, and combinations of two or more thereof. 9. The electrode plate according to 9. 11. The electrode plate according to claim 10, wherein the metal element having substantially no solid solution area with silver includes cerium or titanium. 12. The electrode plate according to claim 1, wherein the multilayer conductive film has an electrode pattern having a fine line portion having a minimum width of 50 μm or less. 13. An observer-side electrode plate, a back-side electrode plate arranged to face the observer-side electrode plate, and a liquid crystal substance enclosed between the electrode plates, the observer-side electrode plate and the back-side electrode plate. 13. A liquid crystal display device, characterized in that at least one of them is constituted by the electrode plate according to any one of claims 1 to 12. 14. The electrode plate according to claim 1, wherein the silver-based thin film has a thickness of 50 nm or more. 15. An observer-side electrode plate provided with a transparent electrode,
15. A back electrode plate, which is arranged so as to face the back electrode and has a light-reflecting electrode, and a liquid crystal substance enclosed between the electrode plates. The back electrode plate is constituted by the electrode plate according to claim 14. A liquid crystal display device characterized by the above.