WO2009104695A1

WO2009104695A1 - Method for producing transparent conductive substrate

Info

Publication number: WO2009104695A1
Application number: PCT/JP2009/052927
Authority: WO
Inventors: 邦彦中田; 健一朗菅原
Original assignee: 住友化学株式会社
Priority date: 2008-02-22
Filing date: 2009-02-19
Publication date: 2009-08-27
Also published as: TW200943427A

Abstract

Disclosed is a method for producing a transparent conductive substrate, by which there can be easily produced a transparent conductive substrate having good conductivity and transparency and comprising a titanium oxide transparent conductive film which is patterned into a desired shape. In this method, a precursor liquid for forming a titanium oxide transparent conductive film is applied onto a transparent substrate and dried at a temperature not more than 350˚C, and the thus-obtained coating film is subjected to etching and then to annealing. The precursor liquid for forming a titanium oxide transparent conductive film preferably contains (A) a reaction product obtained by reacting a titanium compound with hydrogen peroxide and (B) a reaction product obtained by reacting a tantalum compound with hydrogen peroxide.

Description

Method for producing transparent conductive substrate

The present invention relates to a method for producing a transparent conductive substrate provided with a titanium oxide-based transparent conductive film patterned into a desired shape.

Conventionally, as a transparent conductive substrate used for solar cells, liquid crystal display devices, etc., a substrate in which a transparent conductive thin film made of a metal oxide such as indium tin oxide (ITO) is formed on a transparent substrate has been widely used. Yes.

In general, a method of forming a metal oxide thin film is roughly divided into a method of forming a film under vacuum conditions (vacuum method) such as a sputtering method or a PLD (pulse laser deposition) method, a method of forming metal oxide particles or There is a method (coating method) in which a slurry or a solution containing the precursor is applied to a substrate and then heated, but until now, a vacuum method has been usually employed in applications such as a transparent conductive film. This is because a film having higher conductivity than the coating method can be formed by the vacuum method. In other words, the film formed by the coating method is prone to cracking and it is difficult to produce a uniform film, and the film is less dense than the film formed by the vacuum method. It was thought that conductivity was likely to decrease because necking between grains was weakened. In addition, the coating method has a higher possibility that impurities are mixed from outside the system than the vacuum method, and the contamination of impurities into the formed film has been a concern as a cause of impairing the denseness of the film.

By the way, although In (indium) has been used as a main component of ITO, which is a material of a transparent conductive film, problems such as resource depletion and price increase have become serious. For this reason, a transparent conductive film using other metals has been demanded, and development of a transparent conductive substrate using titanium oxide as an alternative material is underway (see Patent Documents 1 and 2).

However, when a film is formed by the above-described vacuum method using a titanium oxide-based material, an oxide (titanium oxide) film is formed immediately after the film formation. Titanium oxide is known to be insoluble in acids and alkalis in the amorphous state as well as in the crystalline state (anatase type crystal phase, rutile type crystal phase). Etching cannot be performed. Therefore, until now, the titanium oxide-based transparent conductive film has a problem that a desired pattern is not provided, and its use is limited to a range that can be used as a so-called solid film.

Japanese Patent Laid-Open No. 10-226598 Japanese Patent Laid-Open No. 2005-11737

The present invention provides a method for producing a transparent conductive substrate, which can easily obtain a transparent conductive substrate having a titanium oxide-based transparent conductive film that has good conductivity and transparency and is patterned into a desired shape. The purpose is to provide.

The present inventor has intensively studied to solve the above problems. As a result, a method of heating after applying the titanium oxide-based transparent conductive film forming precursor liquid to the substrate is adopted as a film forming method until the precursor liquid is heated to change into a complete oxide. The idea was to perform patterning by performing an etching process using an appropriate etching solution in the intermediate state. If the film is in a stage where the film made of the precursor liquid after coating is kept at a specific temperature or lower and the film is dried to remove the solvent in the film, it can be dissolved and removed by the etching solution. Thereafter, it was found that a titanium oxide-based transparent conductive substrate having good conductivity and transparency can be produced by annealing, and the present invention was completed.

That is, it relates to the following description.
(1) Applying a titanium oxide-based transparent conductive film forming precursor liquid on a transparent substrate, drying at a temperature of 350 ° C. or lower, and subjecting the resulting coating to an etching treatment, followed by an annealing treatment. A method for producing a transparent conductive substrate.
(2) A precursor liquid for forming a titanium oxide transparent conductive film is obtained by reacting a reaction product obtained by reacting (A) a titanium compound with hydrogen peroxide and (B) a niobium compound or a tantalum compound with hydrogen peroxide. And the reaction product obtained by the method according to (1).
(3) The etching process is performed by forming a resist film having a predetermined pattern on the film obtained by drying, and removing a portion not covered with the resist film using an etching solution. The method according to (1) or (2).
(4) The method according to any one of (1) to (3), wherein the etching treatment is performed using an etching solution having a solution temperature of 10 to 150 ° C.
(5) The transparent conductive substrate obtained is
A transparent substrate;
The method according to any one of (2) to (4), comprising a patterned transparent conductive film made of titanium oxide doped with niobium or tantalum formed on the transparent substrate.

According to the present invention, there is an effect that it is possible to easily obtain a transparent conductive substrate having a titanium oxide-based transparent conductive film having good conductivity and transparency and patterned into a desired shape. . If this transparent conductive substrate is, for example, a liquid crystal display device, a transparent conductive film that is patterned in a complicated manner is used, such as an active matrix liquid crystal display device using MIM, diode, FET (back transistor), varistor, etc. It can be widely used in required applications.
Further, the present invention does not require a large-scale vacuum apparatus that increases the equipment cost as in the case of the conventional vacuum method. Therefore, the present invention can be implemented at low cost by a simple operation using existing equipment. The effect of being suitable for mass production is also obtained.

In the method for producing a transparent conductive substrate of the present invention, first, a titanium oxide-based transparent conductive film forming precursor solution is applied on a transparent substrate.
The titanium oxide-based transparent conductive film forming precursor liquid used in the present invention (hereinafter sometimes simply referred to as “precursor liquid”) is a material that can become a titanium oxide-based oxide that can exhibit transparent conductivity by heating. If there is no particular limitation, preferably, (A) a reaction product obtained by reacting a titanium compound with hydrogen peroxide and (B) a niobium compound or a tantalum compound (hereinafter referred to as “niobium compound or tantalum compound”) are combined. And a reaction product obtained by reacting “niobium or tantalum” (sometimes collectively referred to as “dopant”) with hydrogen peroxide. This precursor liquid contains a complex (peroxy complex) in which (A) a titanium compound and (B) a niobium compound or a tantalum compound are peroxylated, and the peroxy complex is doped with niobium or tantalum by heating. It is a metal oxide precursor that becomes titanium oxide. Thus, a film formed of a metal oxide obtained by doping titanium oxide with pentavalent niobium or tantalum belonging to group VA of the periodic table shows better conductivity.

The precursor liquid is obtained by reacting i) (A) a titanium peroxy complex, which is a reaction product obtained by reacting a titanium compound with hydrogen peroxide, and (B) reacting a dopant compound with hydrogen peroxide. The reaction product obtained may be obtained by mixing a peroxy complex of a dopant in a desired ratio, or ii) (A) a titanium compound and (B) a dopant compound in a desired ratio in advance. It may be obtained by reacting the mixture mixed with hydrogen peroxide with hydrogen peroxide.

In obtaining the precursor liquid, the mixing ratio of (A) the titanium compound or the peroxy complex derived from the titanium compound and (B) the dopant compound or the peroxy complex derived from the dopant compound is determined as the final formed titanium oxide film. The content ratio of the dopant (niobium or tantalum) may be 0.1 to 40 mol%, preferably 5 to 30 mol%. When the amount of (B) (dopant compound or peroxy complex derived from the dopant compound) is less than the above range, the doping effect may be insufficient and the conductivity may be lowered. On the other hand, the above (B) may be less than the above range. At most, the conductivity may be lowered, or the transparency of the film may be lowered.

In obtaining the precursor liquid, the reaction with hydrogen peroxide (that is, the peroxylation reaction) is carried out by dissolving, for example, a titanium compound, a dopant compound or a mixture thereof with an appropriate solvent, and stirring the mixture as necessary. It can be carried out by adding about 60% by weight of hydrogen peroxide solution. The amount of hydrogen peroxide to be reacted with the titanium compound or dopant compound is not particularly limited, but is usually 0.8 to 20 mol per 1 mol of titanium compound, and usually 0.8 to 20 mol per 1 mol of dopant compound. . The reaction time for the peroxylation reaction is usually about 1 second to 60 minutes, preferably about 5 minutes to 20 minutes. Since the peroxylation reaction with hydrogen peroxide usually involves intense heat generation, it is desirable to carry out the reaction while cooling (specifically, keeping the internal temperature at −10 ° C. or lower). After the reaction, the mixture may be further aged while being cooled to −10 ° C. or lower.
The solvent that can be used for the peroxygenation reaction with hydrogen peroxide is not particularly limited, and examples thereof include water, methanol, ethanol, propanol, butanol, diacetone alcohol, and ethylene glycol. However, from the viewpoint of storage stability (pot life) of the precursor liquid, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, diacetone alcohol (also known as 4-hydroxy-4-methylpentan-2-one), γ-butyrolactone, 4-hydroxy-2-butanone, 5-hydroxy-2-pentanone, δ-valerolactone, ε-caprolactone, tetrahydrofuran-2-carboxylic acid 2-methyl-1,3-propanediol and the like are particularly preferable.

The (A) titanium compound is not particularly limited as long as it contains Ti atoms as a titanium source. For example, titanium chloride (titanium dichloride, titanium trichloride, titanium tetrachloride, etc.), titanium alkoxide (methoxide, ethoxide, Isopropoxide, etc.), titanyl sulfate, metallic titanium, titanium hydroxide (orthotitanic acid), titanium oxysulfate, and the like can be used.
Of the dopant compounds (B), the niobium compound is not particularly limited as long as it contains Nb atoms as a niobium source. For example, niobium chloride, niobium alkoxide (methoxide, ethoxide, etc.), metal niobium, niobium hydroxide, etc. Can be used. Further, the tantalum compound among the dopant compounds (B) is not particularly limited as long as it contains Ta atoms as a tantalum source. For example, tantalum chloride, tantalum alkoxide (methoxide, ethoxide, etc.), metal tantalum, tantalum hydroxide Etc. can be used.
Of the above, titanium alkoxide, niobium alkoxide, and tantalum alkoxide are unstable substances that react immediately upon contact with moisture, and thus are preferably handled in a dry (low humidity) atmosphere.

It is preferable to use hydroxides as the (A) titanium compound and the (B) niobium compound or tantalum compound. That is, titanium hydroxide is used as (A) and niobium hydroxide or tantalum hydroxide is used as (B), or a titanium compound and a dopant compound other than these hydroxides are used to react with hydrogen peroxide. Prior to the formation, hydroxylation may be performed by adding alkali or water in advance, and the resulting hydroxide precipitate may be collected and washed. Thus, if it is a peroxy complex obtained by reacting a hydroxide with hydrogen peroxide, there will be no organic site containing carbon atoms, and it will be decomposed and volatilized by heating to a high temperature. Since it is not necessary, it is preferable because the heating temperature during the annealing process when converting to an oxide can be set at a relatively low temperature.

The solid content concentration of the precursor liquid is usually preferably 10% by weight or less, and more preferably 2% by weight or less from the viewpoint of storage stability (pot life) of the precursor liquid. When the solid content concentration exceeds 10% by weight, the storage stability of the precursor liquid is lowered, and the viscosity is increased at the time of application, so that it may be difficult to apply uniformly on the transparent substrate.
In addition, solid content concentration here means the ratio (weight%) which the total weight of the titanium compound and dopant compound used when obtaining a precursor liquid accounts to the total weight of a precursor liquid.

As the transparent substrate to which the precursor liquid is applied, as long as the shape and transparency can be maintained at the time of heating in each step where heat is applied (for example, baking (prebaking) or annealing treatment described later), There is no particular limitation. For example, inorganic materials such as various glasses, thermoplastic resins and thermosetting resins (for example, epoxy resin, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose) Further, a plate-like material, a sheet-like material, a film-like material or the like formed of a polymer material such as plastics such as polyimide) can be used. The visible light transmittance of the transparent substrate is usually 90% or more, preferably 95% or more.

The coating method for coating the precursor liquid on the transparent substrate is not particularly limited as long as it can be uniformly coated, and a conventionally known method can be adopted. For example, wet coating methods such as a capillary coating method, a spin coating method, a slit die coating method, a spray coating method, a dip coating method, a roll coating method, a screen printing method, a flexographic printing method, and a bar coater method can be employed.

When applying the precursor liquid, the amount of application may be such that the final film thickness (dry film thickness) is 10 nm to 300 nm, for example. If the dry film thickness that is finally formed is smaller than the above range, there may be a place that is difficult to apply partially or a place that is not actually applied, such as when there is unevenness on the substrate, If it is larger than the above range, the transparency may be lowered. In addition, in order to apply the precursor liquid to such a thickness, the application may be performed once or may be performed in a plurality of times.

The film made of the precursor liquid coated on the transparent substrate in this way is dried at a temperature of 350 ° C. or lower, preferably 300 ° C. or lower, more preferably 200 ° C. or lower. That is, when the film made of the precursor liquid after coating is dried to remove the solvent and the like in the film, the temperature is maintained at 350 ° C. or lower (in other words, maintained at 350 ° C. or lower). It is important in the invention. This removes the solvent in the film and keeps the shape of the film, while suppressing the progress of crystallization in the process of changing the precursor liquid (peroxy complex) to metal oxide (Nb or Ta-doped titanium oxide). In addition, the crystalline state of the film can be kept in a state before the complete amorphous phase. Since such a film can be easily dissolved and removed by an etching solution, patterning by an etching process described later becomes possible.

The drying is not particularly limited as long as it is performed within the temperature range, and for example, natural drying (air drying), vacuum drying, reduced pressure drying and the like can be employed.

In the manufacturing method of the present invention, the coating film dried as described above is etched. In the etching process, for example, a resist film having a predetermined pattern is formed on the dried film, and a portion not covered with the resist film, that is, a portion exposed from the resist film is etched using an etching solution. This can be done by removing. After patterning in this way, the resist film may be peeled off and removed using an appropriate solvent (for example, methyl cellosolve acetate). There are no particular restrictions on the specific method and conditions for forming and removing the resist film and removing the exposed portion with an etching solution. For example, a wet etching process applied to a conventional transparent conductive film such as an ITO film It may be performed appropriately according to the method and conditions in.

There is no restriction | limiting in particular as said etching liquid, For example, the etching liquid used for conventional transparent conductive films, such as an ITO film | membrane, can be used. Specifically, examples of the inorganic acid include sulfuric acid, nitric acid, hydroiodic acid such as hydroiodic acid, hydrobromic acid, and hydrochloric acid, mixtures thereof (for example, aqua regia), and various salts thereof (for example, , Ammonium sulfate, ferric chloride, etc.) and other (aqueous) solutions, and examples of the organic acid include oxalic acid, acetic acid, formic acid and the like. Each of them may be used alone or in combination with another one or more.
The concentration of the etching solution is not particularly limited, and may be set as appropriate according to the temperature of the etching solution. For example, the concentration of the etching solution can be adjusted so as to freely control the etching rate in accordance with the curing level of the transparent conductive film.

The etching treatment is preferably performed using an etching solution having a solution temperature of 10 to 150 ° C. More preferably, the temperature of the etching solution used for the etching treatment is 20 to 100 ° C. If the etchant temperature is less than 10 ° C., etching may not be possible, while if it exceeds 150 ° C., it may be difficult to manage the concentration of the etchant.

In the production method of the present invention, the substrate subjected to the etching treatment as described above can be baked (pre-baked) as necessary. As a result, the precursor liquid (peroxy complex) is changed to a metal oxide (Nb or Ta-doped titanium oxide). The crystal state at this time is preferably an amorphous phase.
The heating temperature at the time of firing is, for example, 500 ° C. or less, preferably 50 to 400 ° C. If the heating temperature at the time of firing is too high, a stable crystal phase is precipitated, and there is a possibility that the effect of improving the conductivity by the annealing treatment cannot be seen. The firing time may be appropriately set according to the heating temperature or the like, but is usually about 1 minute to 1 hour, preferably about 3 minutes to 30 minutes. Firing is usually performed in the air.

In the manufacturing method of the present invention, the substrate after the etching treatment as described above is annealed. As a result, the metal oxide (Nb or Ta-doped titanium oxide) forming the film undergoes a crystal transition from the amorphous phase to the anatase phase, and oxygen deficiency is generated in the crystal phase, thereby improving the conductivity. Moreover, when oxygen deficiency is introduced, it tends to change to a highly resistant rutile crystal phase. However, by using the precursor liquid containing the above-described peroxy complex, niobium or tantalum doped in titanium oxide has oxygen deficiency. Even if it is introduced, it acts to stabilize the anatase crystal phase, so that a crystalline state capable of expressing high conductivity is maintained in the obtained film.

In the present invention, the annealing treatment means a treatment in which a substrate obtained by etching is heated to a predetermined temperature in a reducing atmosphere, maintained at the temperature for a predetermined time, and then cooled. As a reducing atmosphere in the annealing treatment, for example, nitrogen, carbon monoxide, argon plasma, hydrogen plasma, hydrogen, vacuum, ammonia, inert gas (such as argon), or an atmosphere of a mixed gas thereof is generally used. A reducing atmosphere. It is preferable to adopt a hydrogen atmosphere (hydrogen gas 100% atmosphere) which is a strong reducing atmosphere.

The heating temperature in the annealing treatment may be a temperature at which the crystal phase of the metal oxide (Nb or Ta-doped titanium oxide) can be changed to an anatase type that expresses high conductivity, and is appropriately determined according to the content ratio of the dopant. You only have to set it. The temperature required for changing to the anatase crystal phase increases as the amount of doping into titanium oxide increases, and the lower limit of the heating temperature of the annealing treatment is usually 450 ° C. or higher, preferably 500 ° C. or higher. On the other hand, if the heating temperature is too high, the anatase crystal phase starts to change to a highly resistant rutile crystal phase, and the conductivity tends to decrease and the transparency of the film also tends to decrease. Usually, it is desirable to set the temperature within a range of 700 ° C. or lower, preferably 600 ° C. or lower, more preferably 550 ° C. or lower. However, the temperature when starting to change to the rutile crystal phase varies depending on the content ratio of the dopant, and when the content ratio of the dopant is relatively high, the crystal phase Does not change and the conductivity is not lowered. Specifically, when a precursor solution containing a peroxy complex as described above is used, if the niobium or tantalum content ratio is more than 10 mol%, the annealing temperature may be higher than 550 ° C. The crystal phase does not change to the rutile type, and good conductivity is obtained. In addition to the above, the heat resistance temperature of the transparent substrate to be used is also taken into consideration when setting the heating temperature for the annealing treatment. For example, when alkali-free glass is used as the transparent substrate, it is usually 700 ° C. or lower, preferably 600 ° C. or lower, more preferably 550 ° C. or lower. The annealing treatment time (heating time) may be appropriately set according to the heating temperature and the like, and is usually about 1 minute to 1 hour, preferably about 3 minutes to 30 minutes.

A preferred embodiment of the transparent conductive substrate obtained by the present invention as described above is a transparent conductive substrate in which a patterned transparent conductive film made of titanium oxide doped with niobium or tantalum is formed on a transparent substrate. is there. Such a transparent conductive film is a thin film made of a polycrystal of Nb or Ta-doped titanium oxide having an anatase type crystal phase, and exhibits good conductivity while having good transparency. is there. Specifically, the transmittance of the preferred transparent conductive substrate obtained by the present invention is usually 70% or more, preferably 75% or more, more preferably 80% or more in the visible light region, and in the infrared region, Usually, it is 70% or more, preferably 75% or more, more preferably 80% or more. The specific resistance of the preferred transparent conductive substrate obtained by the present invention is usually 9 × 10 ⁻³ Ω · cm or less, preferably 8 × 10 ⁻³ Ω · cm or less. In addition, these transmittance | permeability and specific resistance can be measured by the method mentioned later in an Example, for example.

The transparent conductive substrate obtained by the production method of the present invention is, for example, a display device such as a touch panel, LED (light emitting element), liquid crystal display device, organic EL display device, flexible display device, plasma display device, or other information processing. It is used for applications such as device electrodes and wiring materials, solar cell electrodes, heat ray reflective films for window glass, and antistatic films. In particular, since the transparent conductive substrate obtained by the manufacturing method of the present invention includes a transparent conductive film having a desired pattern formed according to the application, for example, a liquid crystal display device is a simple matrix type liquid crystal display device. In addition to active matrix liquid crystal display devices using TFTs and TFTs, transparent conductive substrates with complex patterns such as active matrix liquid crystal display devices using MIMs, diodes, FETs (back transistors), varistors, etc. It can be widely used in required applications. Furthermore, the transparent conductive substrate obtained by the production method of the present invention is effective as an antistatic plate having an antireflection function, taking advantage of its high refractive index.

In the above-described production method of the present invention, the precursor liquid is directly applied on the transparent substrate. However, for use in transparent electrodes such as a device such as a liquid crystal display device, a colored film (color An intermediate film such as a filter) may be interposed, and the precursor liquid may be applied directly on the intermediate film, and the embodiment in which the intermediate film is interposed between the transparent substrate and the transparent conductive film is also the present invention. It is included in the range.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to such examples, and it is needless to say that arbitrary modifications can be made within the scope of the present invention.

The physical properties of the transparent conductive substrate were measured by the following method.
<Specific Resistance> The specific resistance was measured by a four-terminal four-probe method using a resistivity meter (“LORESTA-GP, MCP-T610” manufactured by Mitsubishi Chemical Corporation). Specifically, four needle-shaped electrodes are placed on a straight line on the sample, a constant current is passed between the outer two probes, a constant current is passed between the inner two probes, and the inner two probes are The resulting potential difference was measured to determine the resistance.
<Transmissivity> The transmittance was measured in the range of 190 nm to 2700 nm using an ultraviolet-visible near-infrared spectrophotometer (“V-670” manufactured by JASCO Corporation).
<Crystallinity> Crystallinity was evaluated using an attachment for thin film measurement using an X-ray diffractometer (“RINT2000” manufactured by Rigaku Corporation).
<Crystal structure> The state of niobium doped into titanium was examined using an energy dispersive X-ray microanalyzer (TEM-EDX), and the crystal structure was examined using a field emission electron microscope (FE-SEM).
In the following Examples and Comparative Examples, when a precursor liquid is obtained by mixing a titanium peroxy complex and a niobium peroxy complex, dehydrated ethanol is used to obtain a desired solid content concentration unless otherwise specified. It was adjusted.

Example 1
(Preparation of precursor liquid)
First, 4.0 g of titanium tetraisopropoxide was dissolved in 28.5 g of dehydrated ethanol in an argon gas atmosphere, and 8.0 g of hydrogen peroxide solution having a concentration of 30% by weight was gradually added to the resulting solution with stirring. Then, after completion of the addition, the mixture was stirred for 5 minutes to allow peroxylation reaction. The reaction was performed while cooling the periphery of the flask containing the solution with dry ice, and was controlled so that the internal temperature of the solution did not exceed −10 ° C. when heat was generated by the addition of hydrogen peroxide. The reaction product thus obtained was designated as titanium peroxy complex (a1).
On the other hand, 1.5 g of niobium pentaethoxide was dissolved in 19.2 g of dehydrated ethanol in an argon gas atmosphere, and 1.6 g of hydrogen peroxide solution having a concentration of 30% by weight was gradually added to the resulting solution with stirring. After completion of the addition, the mixture was stirred for 5 minutes to cause a peroxylation reaction. As in the above, the reaction is performed while cooling the periphery of the flask containing the solution with dry ice so that the internal temperature of the solution does not exceed −10 ° C. when heat is generated by the addition of hydrogen peroxide. Controlled. The reaction product thus obtained was designated as niobium peroxy complex (b1).
Next, the titanium peroxy complex (a1) and the niobium peroxy complex (b1) are mixed at a ratio of titanium: niobium = 93: 7 (molar ratio), and a precursor having a solid content concentration of 7% by weight is mixed. Body fluid.

[Film formation and etching treatment]
The obtained precursor liquid was applied once on a transparent substrate (non-alkali glass “Corning Corporation 1737”, thickness 0.7 mm) with a capillary coater to a dry film thickness of 35.7 nm, and then at room temperature. By allowing to stand, the film was air-dried to form a film made of the precursor liquid.
Next, a resist film having a predetermined pattern was formed on the film by photolithography. Specifically, a positive photoresist (“OFPR-800” manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied on the coating, and then heated at 80 ° C. for 5 minutes to form a 1.1 μm-thick resist film. Subsequently, the film was exposed to ultraviolet rays (intensity 50 mJ / cm ^{2 at a} wavelength of 365 nm) through a chrome photomask using an ultraviolet exposure machine (“PLA-501F” manufactured by Canon Inc.), and then a developer ( A resist pattern was formed by developing the photoresist by dipping in a 2.38 wt% aqueous solution of tetramethylammonium hydroxide). Then, an etching process was performed by a wet etching method using the resist film having a predetermined pattern as a mask. Specifically, a mixed solution of sulfuric acid and ammonium sulfate (liquid temperature: 50 ° C.) is used as an etching solution, and a base material (a base material provided with the coating film and a resist film having a predetermined pattern) is immersed therein. After selective etching, the resist layer that was no longer needed was stripped using methyl cellosolve acetate.

[Annealing treatment]
The film thus etched is baked (prebaked) at 400 ° C. for 10 minutes, and then annealed at 500 ° C. for 60 minutes in a reducing atmosphere of 100% hydrogen. A substrate (transparent conductive substrate) provided with a patterned transparent conductive film was obtained.
The specific resistance of the obtained transparent conductive substrate was 5.2 × 10 ⁻³ Ω · cm, and the transmittance was about 80% in the visible region and about 80% in the infrared region. When the crystal phase of the transparent conductive film on this substrate was examined by X-ray diffraction, it was an anatase type. Further, when the crystal structure was observed by TEM-EDX and FE-SEM, it was a polycrystal of titanium oxide doped with Nb.

(Example 2)
(Preparation of precursor liquid)
First, 20.0 g of distilled water was added to 3.0 g of titanium tetraisopropoxide in an argon gas atmosphere and stirred, and the resulting precipitate (titanium hydroxide) was collected from the mother liquor. 1.2 g of this precipitate was dissolved in 2.0 g of ethanol, and 17 g of hydrogen peroxide solution having a concentration of 30% by weight was gradually added to the resulting solution with stirring. It was made to react. The reaction was performed while cooling the periphery of the flask containing the solution with dry ice, and was controlled so that the internal temperature of the solution did not exceed −10 ° C. when heat was generated by the addition of hydrogen peroxide. The reaction product thus obtained was designated as titanium peroxy complex (a2).
On the other hand, 40.0 g of distilled water was added to 5.0 g of niobium pentaethoxide in an argon gas atmosphere and stirred, and the resulting precipitate (niobium hydroxide) was collected from the mother liquor. 2.8 g of this precipitate was dissolved in 2.0 g of ethanol, and 20 g of hydrogen peroxide solution having a concentration of 30% by weight was gradually added to the resulting solution with stirring. It was made to react. As in the above, the reaction is performed while cooling the periphery of the flask containing the solution with dry ice so that the internal temperature of the solution does not exceed −10 ° C. when heat is generated by the addition of hydrogen peroxide. Controlled. The reaction product thus obtained was designated as niobium peroxy complex (b2).
Next, the titanium peroxy complex (a2) and the niobium peroxy complex (b2) are mixed at a ratio of titanium: niobium = 94: 6 (molar ratio), and the solid content concentration is 6.5% by weight. The precursor liquid was used.

[Film formation and etching treatment]
The obtained precursor liquid was applied once on the same transparent substrate as in Example 1 with a spin coater so as to have a dry film thickness of 26.0 nm, and then dried at 50 ° C. for 10 minutes to form a film made of the precursor liquid Formed.
Next, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1. Then, the etching treatment was performed in the same manner as in Example 1 except that a mixed solution of hydrochloric acid and nitric acid (liquid temperature: 100 ° C.) was used as the etching liquid.

[Annealing treatment]
The film thus etched is subjected to an annealing treatment at 500 ° C. for 60 minutes in a reducing atmosphere of 100% hydrogen to thereby provide a substrate (transparent conductive film) having a transparent conductive film having a predetermined pattern. Substrate).
The specific resistance of the obtained transparent conductive substrate was 7.3 × 10 ⁻³ Ω · cm, and the transmittance was about 80% in the visible region and about 80% in the infrared region. When the crystal phase of the transparent conductive film on this substrate was examined by X-ray diffraction, it was an anatase type. Further, when the crystal structure was observed by TEM-EDX and FE-SEM, it was a polycrystal of titanium oxide doped with Nb.

(Example 3)
(Preparation of precursor liquid)
The titanium peroxy complex (a2) obtained in Example 2 and the niobium peroxy complex (b2) were mixed at a ratio such that titanium: niobium = 92: 8 (molar ratio), and the solid content concentration was 6.5. A weight percent precursor solution was obtained.

[Film formation and etching treatment]
The obtained precursor liquid was applied on the same transparent substrate as in Example 1 once with a spin coater so as to have a dry film thickness of 55.0 nm, and then allowed to air-dry by allowing to stand at room temperature, thus consisting of the precursor liquid. A film was formed.
Next, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1. And the etching process was performed like Example 1 except having used sulfuric acid (liquid temperature: 50 degreeC) as an etching liquid.

[Annealing treatment]
The film thus etched is baked (pre-baked) at 80 ° C. for 10 minutes, and then annealed at 500 ° C. for 60 minutes in a reducing atmosphere of 100% hydrogen to obtain a predetermined value. A substrate (transparent conductive substrate) provided with a patterned transparent conductive film was obtained.
The specific resistance of the obtained transparent conductive substrate was 6.5 × 10 ⁻³ Ω · cm, and the transmittance was about 80% in the visible region and about 80% in the infrared region. When the crystal phase of the transparent conductive film on this substrate was examined by X-ray diffraction, it was an anatase type. Further, when the crystal structure was observed by TEM-EDX and FE-SEM, it was a polycrystal of titanium oxide doped with Nb.

Example 4
(Preparation of precursor liquid)
The titanium peroxy complex (a1) obtained in Example 1 and the niobium peroxy complex (b1) were mixed at a ratio of titanium: niobium = 92: 8 (molar ratio), and the solid content concentration was 9.16. A weight percent precursor solution was obtained.

[Film formation and etching treatment]
The obtained precursor liquid was applied once on the same transparent substrate as in Example 1 with a spin coater so as to have a dry film thickness of 71.0 nm, and then dried at 50 ° C. for 10 minutes to form a film made of the precursor liquid Formed.
Next, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1. Then, an etching process was performed in the same manner as in Example 1.

[Annealing treatment]
The film thus etched is subjected to an annealing treatment at 500 ° C. for 60 minutes in a reducing atmosphere of 100% hydrogen to thereby provide a substrate (transparent conductive film) having a transparent conductive film having a predetermined pattern. Substrate).
The specific resistance of the obtained transparent conductive substrate was 5.6 × 10 ⁻³ Ω · cm, and the transmittance was about 80% in the visible region and about 80% in the infrared region. When the crystal phase of the transparent conductive film on this substrate was examined by X-ray diffraction, it was an anatase type. Further, when the crystal structure was observed by TEM-EDX and FE-SEM, it was a polycrystal of titanium oxide doped with Nb.

(Example 5)
(Preparation of precursor liquid)
The titanium peroxy complex (a1) obtained in Example 1 and the niobium peroxy complex (b1) were mixed at a ratio of titanium: niobium = 93: 7 (molar ratio), and the solid content concentration was 7% by weight. The precursor liquid was used.

[Film formation and etching treatment]
The obtained precursor solution was applied once on the same transparent substrate as in Example 1 with a capillary coater so as to have a dry film thickness of 35.7 nm, and then dried at 300 ° C. for 10 minutes to form a coating comprising the precursor solution Formed.
Next, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1. Then, the etching treatment was performed in the same manner as in Example 1 except that a mixed solution of sulfuric acid and ammonium sulfate (liquid temperature: 150 ° C.) was used as the etching liquid.

[Annealing treatment]
The film thus etched is subjected to an annealing treatment at 500 ° C. for 60 minutes in a reducing atmosphere of 100% hydrogen to thereby provide a substrate (transparent conductive film) having a transparent conductive film having a predetermined pattern. Substrate).
The specific resistance of the obtained transparent conductive substrate was 8.3 × 10 ⁻³ Ω · cm, and the transmittance was about 80% in the visible region and about 80% in the infrared region. When the crystal phase of the transparent conductive film on this substrate was examined by X-ray diffraction, it was an anatase type. Further, when the crystal structure was observed by TEM-EDX and FE-SEM, it was a polycrystal of titanium oxide doped with Nb.

(Comparative Example 1)
The same operation as in Example 1 was performed except that the etching process was changed to be performed after the annealing process in Example 1.
Specifically, a precursor solution prepared in the same manner as in Example 1 was applied on a transparent substrate in the same manner as in Example 1, and then fired under the same conditions as in Example 1 (firing temperature is 400 ° C.) ( Pre-baking) and annealing were performed to obtain a substrate (transparent conductive substrate) having a transparent conductive film on the entire surface. The specific resistance, transmittance, and crystal phase of this transparent conductive substrate were the same as in Example 1.
Next, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1 in order to form a predetermined pattern on the obtained transparent conductive film after the annealing treatment. And the etching process was performed like Example 1 except having raised the liquid temperature of the etching liquid from 50 degreeC to 150 degreeC. However, although the temperature of the etching solution was higher than that of Example 1, the etching solution could not dissolve the annealed film, and a pattern could not be formed on this film.

(Comparative Example 2)
The same operation as in Comparative Example 1 was performed except that the annealing treatment was not performed in Comparative Example 1 (that is, only baking (pre-baking) was performed after coating).
Specifically, a precursor solution prepared in the same manner as in Example 1 was applied on a transparent substrate in the same manner as in Example 1, and then fired under the same conditions as in Example 1 (firing temperature is 400 ° C.) ( By performing only the pre-bake, a substrate (transparent conductive substrate) provided with a transparent conductive film on the entire surface was obtained.
Next, in order to form a predetermined pattern on the obtained transparent conductive film, a resist film having a predetermined pattern was formed on this film in the same manner as in Example 1. Then, an etching process was performed in the same manner as in Comparative Example 1. However, in this case, although the annealing process is not performed before the etching process, the film is baked at 400 ° C., so the formed film cannot be dissolved and the pattern cannot be formed. It was.

(Comparative Example 3)
The same operation as in Example 3 was performed except that the etching process was changed to be performed after the annealing process in Example 3.
Specifically, after the precursor liquid prepared in the same manner as in Example 3 is applied on the transparent substrate in the same manner as in Example 3, baking (pre-baking) and annealing treatment are performed under the same conditions as in Example 3. Thus, a substrate (transparent conductive substrate) provided with a transparent conductive film on the entire surface was obtained. The specific resistance, transmittance, and crystal phase of this transparent conductive substrate were the same as those in Example 3.
Next, a resist film having a predetermined pattern was formed on the film in the same manner as in Example 3 in order to form a predetermined pattern on the obtained transparent conductive film after the annealing treatment. Etching was performed in the same manner as in Example 3 except that the etching solution used was changed from sulfuric acid (liquid temperature: 50 ° C.) to a mixed solution of sulfuric acid and ammonium sulfate (liquid temperature: 100 ° C.). However, although the temperature of the etching solution was higher than that in Example 3, the etching solution could not dissolve the annealed film, and a pattern could not be formed on this film.

As mentioned above, although the manufacturing method of the transparent conductive substrate concerning this invention was demonstrated in detail, the range of this invention is not restrained by these description and can be changed or improved suitably in the range which does not impair the meaning of this invention. Is.

Claims

A transparent conductive material comprising: applying a precursor liquid for forming a titanium oxide-based transparent conductive film on a transparent substrate; drying at a temperature of 350 ° C. or less; and subjecting the obtained coating to an etching treatment, followed by an annealing treatment. Of manufacturing a conductive substrate.
A precursor liquid for forming a titanium oxide-based transparent conductive film is obtained by reacting (A) a reaction product obtained by reacting a titanium compound with hydrogen peroxide and (B) reacting a niobium compound or a tantalum compound with hydrogen peroxide. The process of claim 1 comprising a reaction product.
The etching process is performed by forming a resist film having a predetermined pattern on a film obtained by drying, and removing a portion not covered with the resist film using an etching solution. The method described in 1.
The method according to claim 1, wherein the etching treatment is performed using an etching solution having a liquid temperature of 10 to 150 ° C.
The resulting transparent conductive substrate is
A transparent substrate;
The method according to claim 2, comprising a patterned transparent conductive film formed on the transparent substrate and made of titanium oxide doped with niobium or tantalum.