JPH06160876A - Transparent electrode plate and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a transparent electrode plate having sufficiently high conductivity as a transparent electrode plate used for a display of high quality and wide screen, and a method for manufacturing the same. [Structure] On a transparent substrate 1 having color filter layers 2R, 2G and 2B, a thin film 3 of indium oxide doped with zirconium oxide as a dopant is formed by a sputtering method. The carrier density increases as the amount of zirconium oxide added increases, while the carrier mobility is maintained substantially constant, and a transparent electrode plate having high conductivity can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent electrode plate and a method for manufacturing the same, and more particularly to a transparent electrode plate which has high conductivity and can be formed even under a low substrate temperature condition, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Transparent and highly conductive transparent electrode plates are widely used in various displays and display input devices using liquid crystals.

For example, as shown in FIG. 2, a transparent electrode a of a display using a liquid crystal has a glass substrate a and transmitted light of red, green, and red for each pixel provided at a pixel portion on the glass substrate a. A color filter layer b colored in blue respectively,
A light-shielding film c provided on the glass substrate a between pixels to prevent light transmission from this region, a protective layer d provided on the entire surface of the color filter layer b, and a film formed on the protective layer d. The transparent electrode e thus formed and the orientation film f formed on the transparent electrode e constitute a main part of the transparent electrode e, and the transparent electrode e is formed by sputtering and etched into a predetermined pattern. After that, the transparent conductive film is formed by heat treatment.

As the transparent conductive film, in consideration of its high conductivity, indium oxide to which tin oxide is added as a dopant (ITO thin film) is widely used, and its volume resistivity is about 2. It was 4 × 10 ⁻⁴ Ω · cm.

In addition to the above-mentioned ITO thin film, as the transparent conductive film e, a thin film called tin oxide or a thin film of tin oxide to which antimony oxide is added, or a thin film of zinc oxide to which aluminum oxide is added is known. However, all of them have inferior conductivity as compared with the above ITO thin film, and have insufficient resistance to acid, alkali, humidity and the like, so that the above ITO thin film is widely used.

[0006]

By the way, in recent years, in the above-mentioned displays and display input devices, it is required to increase the pixel density to display a fine screen,
Along with this, it is required to make the transparent electrode pattern denser, and for example, it is required to form the terminal portions of the transparent electrode at a pitch of about 100 μm.

On the other hand, there is a demand for a larger display screen. For such a large screen, it is possible to form the above-mentioned dense pattern of transparent electrodes and to apply a sufficient driving voltage to the liquid crystal. In order to do so, it is necessary to use a transparent electrode having high conductivity as the transparent electrode.

The required conductivity is generally expressed by area resistance (Ω / □) (area resistance is the reciprocal of area conductivity), for example, a low area resistance of 5Ω / □ or less. Is required. The area resistivity is represented by the quotient obtained by dividing the above volume resistivity by the thickness of the transparent conductive film. The volume resistivity of the ITO is about 2.4.
Since it is × 10 ^-4 Ω · cm, the film thickness is 30 in order to obtain a transparent conductive film having an area resistivity of about 5 Ω / □.
It is necessary to form an ITO film having a thickness of 0 nm or more. However, S
In a liquid crystal display using TN (Super Twisted Display) liquid crystal, it is necessary to provide an alignment film f for orienting the liquid crystal on the transparent electrode e as shown in FIG. 2, and the ITO film thickness is 300 nm. When it is large, when the transparent electrode e is formed by patterning this ITO, the ITO thin film is present at a part where it does not exist and a part where it does not exist.
A step of 00 nm is generated, which causes 300 on the surface of the alignment film f.
Since irregularities of about nm are formed, there is a drawback that misalignment of liquid crystals called domains easily occurs.

The present invention has been made on the basis of such a technical background, that is, a transparent electrode plate having sufficiently high conductivity as a transparent electrode plate used for the display of the above-mentioned high quality and wide screen, and its transparent electrode plate. It is intended to provide a manufacturing method.

[0010]

Here, the area conductivity of the transparent conductive film is expressed by the product of volume conductivity and film thickness, and this volume conductivity σ (Ω ^-1 cm ^-1 ) is Is represented by the product of the electric charge e (coulomb) of the carrier (electron or hole) contained in the carrier, the mobility μ (cm ² / V · S) of this carrier, and the carrier density n (cm ^-3 ). . σ (Ω ^-1・ cm ^-1 ) = e ・ μ ・ n (1)

Therefore, in order to improve the volume conductivity of the ITO thin film and reduce its area resistivity, either one of the mobility μ and the carrier density n or both may be increased. In this ITO, tin oxide is a dopant of indium oxide and is involved in the formation of holes that are carriers, as described above. Therefore, if the amount of tin oxide is increased, the carrier density n will increase. It is expected that there will be an increase, and therefore an increase in volume and area conductivity, and a decrease in area resistivity. However, as shown in Table 1 below, when the mixing amount of tin oxide exceeds 5% by weight, IT
The area resistivity of the O thin film becomes a substantially constant value, and even if the tin oxide is further increased, the area resistivity does not decrease. The reason for this is unclear, but the ion radius of In (indium) is about 0.92 angstrom, whereas Sn (tin) is
Has an ionic radius of 0.74 angstroms, and the difference between the two is large. Therefore, as the amount of tin oxide increases, the strain of the indium oxide crystal increases, the defects in the crystal increase, and the mobility μ decreases. I can imagine that

[0012]

[Table 1]

On the other hand, the present inventors have found that the ionic radius of Zr (zirconium) is 0.87 angstrom, which is close to the ionic radius of In, and is the same as Sn.
Since Zr has a valency, by using Zr as a dopant instead of Sn, it becomes possible to increase the carrier density without causing the decrease in the mobility μ, thus decreasing the sheet resistivity and increasing the carrier resistivity. It was found that a transparent conductive film having conductivity can be formed.

The inventions according to claims 1 and 2 are based on such findings, that is, the invention according to claim 1 is an indium oxide in which zirconium oxide is added as a dopant on a transparent substrate. On the other hand, the invention according to claim 2 is the transparent electrode plate according to claim 1, wherein the transparent conductive film has a thickness of 300 nm or less. To do.

In such technical means, the zirconium oxide is present as a dopant in the indium oxide crystal, and the zirconium oxide has a Zr content of Zr.
Carriers composed of holes are generated based on the ions, and the conductivity is improved. In addition, since the ionic radii of Zr ions and In ions are close to each other as described above, the strain of the indium oxide crystal is small despite the doping of zirconium oxide, and even when a large amount of zirconium oxide is added, the carrier is large. Mobility μ does not decrease. Therefore, as the amount of zirconium oxide added increases, the carrier density increases and the conductivity of the transparent conductive film is improved, so that even a thin film of 300 nm or less can achieve high area conductivity and low area resistivity. Is possible. Since such a thin film can achieve a low area resistivity, it can be used as an electrode plate for the above-mentioned liquid crystal display or the like, and a sufficient driving voltage can be applied to the liquid crystal without causing alignment failure. Therefore, it is possible to satisfactorily display a precise and wide screen.

The zirconium oxide is, for example, 10% by weight.
Etc. may be added in a large amount, and the conductivity is improved as the added amount of zirconium oxide is increased. Therefore, the conductivity is dramatically improved (and therefore the area resistivity is decreased) as compared with the conventional ITO thin film. Can be planned. It is desirable that such a transparent conductive film does not contain impurities, but in order to improve the etching characteristics at the time of patterning the transparent conductive film and to improve various physical properties such as transparency, reflectivity, resistance to chemicals, etc. It may contain impurities such as tin oxide, antimony oxide, and titanium oxide.

Examples of the transparent substrate according to the present invention include:
A glass plate, a transparent organic plastic film or sheet can be applied, and when the transparent electrode plate is applied to a color liquid crystal display or the like, one having a color filter layer for coloring transmitted light for each pixel can be used.

The invention according to claim 3 is based on such a technical background. In the transparent electrode plate according to claim 1 or 2, the transparent substrate is a transparent base material and the transparent substrate. And a color filter layer of a plurality of colors arranged on the material for each color and coloring transmitted light.

As the transparent substrate according to claim 3, the glass plate or organic plastic film or sheet can be applied. The color filter layer may be any known one, for example, a photosensitive resin containing a colorant is applied onto the transparent substrate, exposed and developed to form a pixel pattern, or a color pigment is used. It is possible to apply the one formed by printing the containing printing ink in a pixel pattern. Also,
The color filter layer may be formed by electrodeposition of an electrodeposition coating material containing a coloring pigment in a pixel pattern.

Further, the transparent substrate is provided with the color filter layer at the pixel portion, and in order to improve the contrast of the display screen by blocking ambient light incident on the inter-pixel portion between the pixels. An opaque light-shielding layer may be provided between the pixels, and the light-shielding film is composed of a thin film of metal chromium or a resin film in which a light-shielding pigment such as carbon black is dispersed in a photosensitive resin. Things are available. Furthermore, a transparent protective layer may be provided on the color filter layer to smooth the surface on which the transparent conductive film is formed.

When this transparent electrode plate is used as a front plate disposed on the observer side of a liquid crystal display, a transparent conductive film of the transparent substrate is formed to prevent reflected light from the display surface. The transparent electrode plate may be provided with an antireflection film on the opposite surface, and when the transparent electrode plate is used as a back plate of a reflective liquid crystal display, a reflective film that efficiently reflects light rays from the viewer side. May be provided. A magnesium oxide thin film or a magnesium fluoride thin film can be used as the antireflection film, and a thin film of aluminum, magnesium, silicon oxide, magnesium fluoride or the like can be used as the reflective film.

Next, a method of manufacturing the transparent electrode plate according to the present invention will be described.

The transparent electrode plate according to the present invention can be manufactured by forming a transparent conductive film on the transparent substrate by a method such as vacuum deposition, ion plating and sputtering. The atomic weight of Zr is In. Since the atomic weight is close to the atomic weight, in the case of film formation by sputtering, a sputtering rate of ZrO ₂ almost similar to that of In ₂ O ₃ can be obtained. Therefore, by sputtering a mixture of the two as a target, it is possible to form a transparent conductive film having a composition substantially similar to that of the target.

The invention according to claim 4 is based on such a technical background, that is, in the method for producing a transparent electrode plate by forming a transparent conductive film on a transparent substrate by a sputtering method, It is characterized by using a mixture of indium oxide and zirconium oxide as a target.

According to the invention of claim 4, the composition of the target is directly reflected on the composition of the transparent conductive film. Therefore, the composition of the transparent conductive film can be easily controlled by controlling the composition of the target. Therefore, it is possible to stably manufacture a transparent electrode plate having a desired conductivity. The composition of such a target may contain about 10% by weight of zirconium oxide like the composition of the transparent conductive film described above.
It may contain a slight amount of impurities in order to improve the physical properties (transparency, reflectivity, resistance, etc.) of the transparent conductive film. During sputtering, it is desirable to use a high-density target in which the density of indium oxide and zirconium oxide is high with respect to the bulk as the target in order to reduce the amount of gas released into the sputtering atmosphere and reduce the impedance of discharge. Moreover, since the transparent conductive film is adversely affected by the presence of water, it is necessary to consider that the target does not absorb moisture during sputtering.

As the sputtering method, magnetron sputtering is desirable. In this case, the magnetic field of the magnetron cathode may be about 400 gauss, but a strong magnetic field of 800 gauss or more is required to reduce the area resistivity of the formed transparent conductive film. Is desirable.

Further, the sputtering apparatus preferably has a high vacuum, and particularly an ultrahigh vacuum, in order to prevent the moisture and nitrogen contained therein from affecting the transparent conductive film. It should be noted that a gas containing hydrogen or water can be used as an introduction gas at the time of sputtering as long as it is a small amount, and thus the transparent conductive film formed in the presence of a small amount of hydrogen or water has a fine crystal grain size. As a result, it is possible to improve the etching rate when etching and patterning this.

Further, it is desirable that the gas pressure when the gas is introduced and the sputtering is performed in a high vacuum (for example, 2.5 mTorr. Or less).

In the case of film formation by this sputtering method, the sheet resistance of the transparent conductive film can be further reduced by heating the transparent substrate to 200 to 400 ° C. When it is composed of a film or sheet, or when the transparent substrate has a color filter layer containing a resin as a main component, it is necessary that the temperature is not higher than the heat resistant temperature of the plastic film or sheet or the color filter layer. In particular, in the case of a transparent substrate provided with a color filter layer, when the sputtering is performed at a substrate temperature exceeding 150 ° C., the obtained transparent conductive film is crystallized, and strict etching conditions such as heating are required for etching during patterning. It may be necessary and may damage the color filter layer. On the other hand, when the sputtering film formation is performed at room temperature or at a substrate temperature of 140 ° C. or less, the obtained transparent conductive film becomes an amorphous-like (amorphous-like) thin film and does not require severe etching conditions such as heating. The color filter layer can be etched and patterned quickly, and its shape and spectral transmittance can be maintained as they are without damaging the color filter layer.

The invention according to claim 5 is based on such a technical reason, that is, in the method for producing a transparent electrode plate according to claim 4, the substrate temperature is set to 14
It is characterized in that the sputtering is performed while maintaining the temperature at 0 ° C. or lower.

According to the invention of claim 5, since an amorphous-like transparent conductive film that can be etched and patterned quickly without etching conditions can be formed, the color filter layer is not damaged and is originally intended to be formed. It is possible to easily pattern the transparent conductive film while maintaining the quality. Before or after this patterning, 2
It is desirable to anneal by heating to a temperature of 00 to 270 ° C. This annealing further improves conductivity and transparency.

[0032]

According to the inventions of claims 1 to 3, since the transparent conductive film composed of indium oxide doped with zirconium oxide as a dopant is provided on the transparent substrate, it is a thin film and has a low area resistivity. Can be achieved.

Further, according to the invention of claim 4, in a method for producing a transparent electrode plate by forming a transparent conductive film on a transparent substrate by a sputtering method, a mixture of indium oxide and zirconium oxide is used as a sputtering target. Since it is used, it is possible to stably manufacture a transparent electrode plate having such a low sheet resistivity,

On the other hand, according to the invention of claim 5, the sputtering is carried out while maintaining the substrate temperature at 140 ° C. or lower, so that the transparent conductive film is maintained while maintaining its original quality without damaging the color filter layer. Can be easily patterned.

[0035]

【Example】

Example 1 A glass plate having a thickness of 0.7 mm (a float blue plate having an SiO ₂ undercoat layer) was used as a transparent substrate, and In ₂ O ₃ and ZrO ₂ were used as targets in a ratio of 9: 1.
A high density target mixed by (weight ratio) is used, both are placed in a sputtering device, and a mixed gas of a small amount of oxygen gas added to argon gas is introduced into the sputtering device to adjust the pressure to 1.8 mmTorr. ． The pressure was adjusted to 2, and a thin film was formed on the transparent substrate by sputtering. At this time, the temperature of the transparent substrate is about 250 ° C., and the thickness of the thin film formed on this transparent substrate is 2400 Å.

Area resistivity, volume resistivity of the obtained thin film,
The carrier mobility and carrier concentration are shown in Table 2.

Example 2 As shown in FIG. 1, the thickness 1.
Stripe color filter pattern (thickness about 2 μm) of three colors of red 2R, green 2G and blue 2B is made on a 1 mm glass plate 1 by a printing ink in which a colorant is mixed with a mixed resin of low molecular weight epoxy resin and melamine resin. It was printed to give a transparent substrate.

On the other hand, as targets, In ₂ O ₃ and Zr
A high density target in which O ₂ was mixed at a ratio of 9: 1 (weight ratio) was used, and both the target and the transparent substrate were placed in a sputtering apparatus, and a small amount of oxygen gas was added to argon gas in the apparatus. Was introduced into the mixed gas, and the pressure was increased to 1.8 mm Torr. The pressure was adjusted to 2, and the thin film 3 was formed on the transparent substrate by sputtering. At this time, the temperature of the transparent substrate is about room temperature, and the thin film 3 formed on this transparent substrate
Has a thickness of 2600 angstroms.

Next, the transparent substrate having the thin film 3 formed thereon was annealed by heating at 220 ° C. for 60 minutes. The area resistivity, volume resistivity, carrier mobility, and carrier concentration of the thin film 3 thus annealed are shown in Table 2.

[0040]

[Table 2]

[0041]

According to the inventions of claims 1 to 3, since it is a thin film and can achieve a low area resistivity, it can be used as an electrode plate of a liquid crystal display or the like to cause alignment failure. Moreover, there is an effect that a sufficient driving voltage can be applied to the liquid crystal and a fine and wide screen can be satisfactorily displayed.

Further, according to the invention of claim 4, it is possible to stably manufacture a transparent electrode plate having such a low area resistivity, while according to the invention of claim 5, the color electrode plate Since the transparent conductive film can be easily patterned while maintaining the original quality of the filter layer without damaging the filter layer, the reliability of the transparent electrode plate, the liquid crystal display or the like is significantly improved. .

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a transparent electrode plate according to a third embodiment.

FIG. 2 is a sectional view of a transparent electrode plate of a conventional liquid crystal display.

[Explanation of symbols]

 1 glass plate. 2R color filter layer. 2G color filter layer. 2B color filter layer. 3 Transparent conductive film.

Claims (6)

[Claims] 1. A transparent electrode plate comprising a transparent conductive film made of indium oxide doped with zirconium oxide as a dopant on a transparent substrate. 2. The transparent electrode plate according to claim 1, wherein the transparent conductive film has a thickness of 300 nm or less. 3. The transparent electrode plate according to claim 1, wherein the transparent substrate is a transparent base material, and a plurality of color filters are arranged on the transparent base material for each color to color transmitted light. A transparent electrode plate comprising: a layer. 4. A method for manufacturing a transparent electrode plate by forming a transparent conductive film on a transparent substrate by a sputtering method, wherein a mixture of indium oxide and zirconium oxide is used as a sputtering target. Manufacturing method. 5. The method for producing a transparent electrode plate according to claim 4, wherein sputtering is performed while maintaining the substrate temperature at 140 ° C. or lower. 6. The method for manufacturing a transparent electrode plate according to claim 4, wherein the transparent substrate is a transparent base material, and a plurality of transparent substrates are provided for each color to color transmitted light. A method of manufacturing a transparent electrode plate, comprising: a color filter layer for each color.