JP4608030B2 - Method for producing transparent conductive material - Google Patents

Description

  The present invention relates to a method for producing a transparent conductive material in which a highly transparent highly conductive film is laminated on a transparent substrate. More specifically, the present invention relates to a novel transparent conductive material production method capable of forming a highly transparent highly conductive oxide film on a low heat resistant substrate such as a transparent resin film.

The transparent conductive film is a thin film having conductivity despite being transparent. Transparent conductive films can be used for transparent electrodes for display panels such as liquid crystal displays (LCD), electroluminescence (EL) displays, plasma displays (PDP), field emission displays (FED), and solar cell panels. An electrode etc. are mentioned. It is also applied to electromagnetic shielding plates.
A typical example of the transparent conductive film is a thin film made of an oxide of indium and tin (ITO). Since this ITO film has high transparency and high conductivity, it is widely used now. However, indium is a rare metal element, and the cost of raw materials may increase with increasing demand and resource depletion.

Titanium oxide-based transparent conductive films are attracting attention from the viewpoints of cost reduction, low environmental load, low toxicity, low resistivity / high light transmittance comparable to or higher than ITO films, and diversity of physical properties control ( Non-patent document 1).
As a titanium oxide-based transparent conductive film, for example, Non-Patent Document 1 discloses an Nb-doped TiO ₂ epitaxial thin film (TNO) having an anatase-type crystal structure, an oxygen deficient or Sb-doped SrTiO ₃ film having a perovskite-type crystal structure, etc. Has been introduced.

Patent Document 1 discloses a transparent conductor made of M: TiO ₂ having an anatase type crystal structure. As M, Nb, Ta or the like is shown. This conductor seems to be manufactured by depositing M: TiO ₂ on the SrTiO ₃ substrate by the pulse laser deposition (PLD) method. In the PLD method, for example, a sintered body of niobium oxide and titanium oxide is used as a target, and film formation is performed by irradiating a pulse laser in an oxygen atmosphere under reduced pressure. Patent Document 1 does not show a specific example in which a film is formed by a method other than the PLD method, but molecular beam epitaxy (MBE) method, sputtering method, other physical vapor deposition (PVD) method, and MOCVD method are used. There is only a description that a chemical vapor deposition (CVD) method, a sol-gel method, a chemical solution method, or the like can be used. However, the production method of Patent Document 1 has low production efficiency of M: TiO ₂ having an anatase type crystal structure, and industrial feasibility is low.

  Patent Document 2 describes a high refractive index transparent thin film layer containing hydrogen atoms in a specific ratio. The transparent thin film layer can be formed by sputtering in a hydrogen gas atmosphere using a metal oxide such as tin oxide, indium oxide, zinc oxide, niobium oxide, and titanium oxide as a target material. However, if hydrogen is included in the film, the transparency of the film is lowered, making it unsuitable for applications such as transparent electrodes.

  Further, Patent Document 3 discloses Nb, Ta, and Pt as methods for overcoming the drawbacks of the conductors obtained by the methods described in Patent Document 1 and Patent Document 2 (low productivity of PLD method, reduced transparency due to use of hydrogen). One or more selected from the group consisting of Mo, As, Sb, Al, Hf, Si, Ge, Zr, W, Co, Fe, Cr, Sn, Ni, V, Mn, Tc, Re, P and Bi A method for producing a conductor, comprising: forming a precursor layer made of titanium oxide to which a dopant is added on a substrate surface; and annealing the precursor layer in a reducing atmosphere to form a metal oxide layer Has proposed. The annealing requires that the substrate temperature be 300 ° C. or higher.

WO2006 / 016608 JP 2004-95240 A JP 2008-84824 A

"Technology of transparent conductive film" pp. 173-184, Japan Society for the Promotion of Science Transparent Oxide Optical / Electronic Materials, 166th edition, revised 2nd edition, Ohmsha (issued on December 20, 2006)

The method for producing a conductive film described in the above prior art documents has problems such as low productivity, low transparency, and inability to use a low heat resistant substrate such as a resin film.
Accordingly, an object of the present invention is to provide a novel method for producing a transparent conductive material capable of forming a highly transparent and highly conductive oxide film on a low heat resistant substrate such as a transparent resin film. To do.

  The present inventors diligently studied to solve the above problems. As a result, a titanium metal film containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W is formed on the substrate, and the metal film is anodized to form an oxide film. It has been found that a highly transparent and highly conductive oxide film can be easily formed on a low heat resistant substrate such as a transparent resin film upon chemical conversion. The present invention has been further studied and completed based on this finding.

That is, the present invention is as follows.
<1> A titanium metal film containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W is formed on a substrate, and all or part of the metal film is formed at 0 ° C. The manufacturing method of the transparent conductive material which has the process formed into a conductive oxide film by anodizing below.
<2> The method for producing a transparent conductive material according to <1>, wherein the substrate is made of at least one material selected from the group consisting of glass, resin, and semiconductor material.
<3> The method for producing a transparent conductive material according to <1> or <2>, wherein the substrate is a flat plate, a sheet, or a film.
<4> The metal film is formed by at least one method selected from the group consisting of a physical vapor deposition method, a chemical vapor deposition method, a sol-gel method, and a synthesis method from a solution. <1> to <3 The manufacturing method of the transparent conductive material of any one of>.
<5> Any of the above <1> to <4>, wherein the total sum of at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W in the metal film is 2 to 15 atomic% The manufacturing method of the transparent conductive material of 1 item | term.
<6> The method for producing a transparent conductive material according to any one of <1> to <5>, wherein the metal film is an alloy having titanium as a base metal.

<7> The method for producing a transparent conductive material according to any one of <1> to <6>, wherein the thickness of the metal film is 20 to 200 nm.
<8> On the substrate, a titanium metal film (I) containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W, and Zr, Hf, Nb, Ta, Mo and Patterning a titanium metal film (II) containing no element of the group consisting of W,
A transparent conductive material having a step of forming a conductive oxide film (I) and an insulating oxide film (II) by anodizing the metal film (I) and the metal film (II) at 0 ° C. or less. Production method.
<9> The method for producing a transparent conductive material according to any one of <1> to <8>, wherein the anodic oxidation is performed in an aqueous solution containing an acid or a salt thereof, hydrogen peroxide, and an antifreezing agent.
<10> The method for producing a transparent conductive material according to any one of <1> to <9>, wherein the anodic oxidation is performed at −30 to −3 ° C.
<11> The method for producing a transparent conductive material according to any one of <1> to <10>, wherein the anodic oxidation voltage is 0.75 V to 1.25 V per 1 nm of the thickness of the metal film.
<12> Any one of <1> to <11>, wherein the anodization is stopped from when the applied voltage reaches a specified anodizing voltage until the current density becomes 1 μA / cm ² or less. The manufacturing method of the transparent conductive material of item.
<13> Any one of <1> to <11>, wherein the anodization is stopped after the applied voltage reaches a specified anodic oxidation voltage until 400 minutes have elapsed since the application voltage reached. Manufacturing method of transparent conductive material.
<14> The transparent conductive material according to any one of <1> to <13>, wherein the current density until the applied voltage reaches a specified anodic oxidation voltage is 0.1 to 1000 mA / cm ^2. Manufacturing method.

<15> A transparent conductive material having a transparent conductive oxide film obtained by the production method according to <1> to <14>.
<16> The transparent conductive material according to <15>, wherein the oxide film is amorphous.
<17> The oxide film has a thickness of 20 to 250 nm, a resistivity of 10 ⁻² to 10 ⁻⁴ Ω · cm, and a light transmittance of 50% or more in a wavelength range of 360 nm to 2.4 μm. The transparent conductive material according to <15> or <16>.
<18> A transparent electrode comprising the transparent conductive material according to <15> to <17>.
<19> An electronic device comprising the transparent conductive material according to <15> to <17>.
<20> A solar cell comprising the transparent conductive material according to <15> to <17>.
<21> A method for producing a transparent conductive film, comprising the steps of obtaining a transparent conductive material by the production method according to <1> to <14> and then removing the substrate.
<22> A transparent conductive film obtained by the production method according to <21>.
<23> A transparent electrode comprising the transparent conductive film according to <22>.
<24> An electronic device comprising the transparent conductive film according to <22>.
<25> A solar cell comprising the transparent conductive film according to <22>.

  According to the production method of the present invention, a transparent conductive material having both good transparency and conductivity can be produced with high productivity. Further, according to the production method of the present invention, even if the base of the transparent conductive material is a material that does not have heat resistance, the transparent conductive film can be easily manufactured on the base.

It is a conceptual sectional view showing an example of the transparent conductive material of the present invention. It is a figure which shows the relationship between an anodic oxidation voltage and the X-ray diffraction intensity of an oxide film. It is a figure which shows the relationship between Nb addition amount and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between Ta addition amount and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the thickness of a Nb addition oxide film, and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the thickness of Ta addition oxide film, and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between an anodic oxidation voltage and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the electrolyte solution at the time of anodizing, and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the stop time of anodization, and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the kind of base | substrate, and the light transmittance of a transparent conductive material. It is a figure which shows the relationship between the temperature at the time of anodization, and the light transmittance of a transparent conductive material. It is a conceptual sectional view showing an example of a multilayer electric circuit using the transparent conductive material of the present invention and its equivalent circuit diagram. It is a top view which shows the film | membrane pattern of A layer of the multilayer electric circuit shown in FIG. 12, B layer, and C layer.

  Embodiments of the present invention will be described below. Note that the present invention is not limited to this embodiment.

  FIG. 1 is a conceptual cross-sectional view showing an embodiment of the transparent conductive material of the present invention. In this embodiment, a titanium metal film 2 containing at least one element selected from Zr, Hf, Nb, Ta, Mo and W (hereinafter sometimes referred to as a different metal element) on the surface of the substrate 1. Then, the metal film is anodized at 0 ° C. or less to form an oxide film 3. In this way, the transparent conductive material 10 is obtained.

(Substrate)
The substrate 1 is not particularly limited depending on the material, shape, etc. as long as the metal film 2 can be formed. Therefore, it may be a substrate made of an inorganic material or a substrate made of an organic material. Further, it may be a base made of a single crystalline or polycrystalline crystalline material, a base made of an amorphous material, or a material in which these crystalline states are mixed. It may be a substrate.

Specific examples of materials used for the substrate include glass, quartz, resin, semiconductor materials such as silicon and GaN, single crystal or polycrystalline material of strontium titanate (SrTiO ₃ ), perovskite crystal structure or a similar structure. Examples thereof include single crystal or polycrystal materials made of rock salt type crystals. These may contain dopants, impurities and the like as long as the effects of the present invention are not impaired.

  Examples of the resin include polystyrene, polycarbonate, polyethylene, polypropylene, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyarylate (PAR), triacetyl cellulose (TAC), polyether ether ketone (PEEK), and polysulfone (PSF). ), Polyethersulfone (PES), polyamide, polyimide, epoxy resin, (meth) acrylic resin, and the like. A transparent resin is preferable.

The substrate is preferably a flat plate, a sheet, or a film as a shape. The thickness of the substrate of these shapes is not particularly limited, but is preferably 1 mm or less when the substrate is required to have high transparency, and the substrate is required to have high mechanical strength and the light transmittance may be somewhat sacrificed. May be thicker than 1 mm. Therefore, the thickness of the substrate may be, for example, 0.02 to 10 mm.
When the substrate is a sheet or a film, it is preferable to have flexibility. By using a flexible resin sheet or resin film as the substrate, an organic EL display or a solar cell that can be bent or rolled can be manufactured. Further, a hard coat layer may be provided to increase the hardness of the resin film surface. In addition, a gas barrier layer may be provided on the resin film in order to improve the moisture resistance of the organic EL display.

When a glass plate is used as the substrate, the glass substrate with ITO of the liquid crystal display element or the glass substrate with SnO _{2 of the} solar cell can be replaced with the transparent conductive material of the present invention. As the glass plate, those having almost no warping or scratches on the surface and excellent thermal stability are preferable. In the active matrix driving system of the display, alkali elution from the glass plate may greatly affect the performance of the active element, so it is preferable to use non-alkali glass (white plate glass). In the simple matrix driving method, inexpensive soda lime glass (blue plate glass) can be used. The glass plate manufacturing method includes a float method, a download method, a fusion method, and the like. The alkali-free glass is usually produced using a download method or a fusion method, and the soda lime glass is usually produced using a float method.

Further, an antireflection layer, an antiglare layer, an antifouling layer, or the like may be formed on the substrate.
When a soluble substrate is used, the substrate can be dissolved and removed after anodization to obtain the oxide film 3 as a single film (transparent conductive film). When using a substrate that is soluble in the electrolytic solution used for anodization, it is possible to devise measures such as protecting the substrate with a masking material or the like so that the substrate is not eroded by the electrolytic solution.
The transparent conductive film as a single film can be used for applications such as attaching to a part of a liquid crystal display element to give a touch panel function.

  The substrate preferably has a flat surface so as not to impair the optical properties of the transparent conductive material. As a flat substrate, a polished substrate can be used. The polishing method is not particularly limited, and for example, it can be polished using diamond slurry or colloidal silica as an abrasive. By polishing, the surface roughness may be flattened until the root mean square roughness (rms) is 1 nm or less.

  Before forming the metal film 2, it is preferable to clean the surface of the substrate 1. For example, when using a glass plate or silicon substrate, perform ultrasonic cleaning using acetone, ethanol, etc. or cleaning using an acid such as hydrochloric acid, rinse with pure water as necessary, and then apply nitrogen gas to the substrate surface. The moisture can be removed from the substrate surface by spraying on the substrate. It is considered that the cleaning removes oxides, organic substances, and the like from the surface of the substrate, and improves the flatness of the oxide film 3 and the adhesion to the substrate.

(Metal film)
The metal film 2 contains titanium metal as a main component and contains at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo, and W.
The metal film 2 may contain a dopant, an inevitable impurity, or an impurity other than the inevitable impurity in addition to the above elements as long as the effects of the present invention are not impaired. In order to obtain high transparency and conductivity, the sum of at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W in the metal film is preferably 2 to 15 atomic%. -12 atomic% is more preferable, and 4-8 atomic% is more preferable.
The metal film 2 may be an alloy with a dissimilar metal element having titanium as a base metal. The metal film 2 preferably contains a heterogeneous metal element without being unevenly distributed.

  The thickness of the metal film 2 is not particularly limited, but is preferably in the range of 20 to 200 nm. As will be described later, when the metal film is anodized, it is formed into an oxide film. The oxide film obtained by the method of the present invention is transparent. To make a thick metal film transparent, it must be anodized at a higher voltage than in the case of a thin metal film. In general, a thin metal film tends to be less conductive than a thick metal film. However, as shown in the examples described later, even if the film is not so thick, according to the method of the present invention, a material having sufficient conductivity can be manufactured.

In FIG. 1, only the titanium metal film 2 containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W is formed on the substrate. A metal film other than 2 may be formed.
For example, as shown in FIG. 13, a titanium metal film (I) containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W, and Zr, Hf, Nb, Ta, A titanium metal film (II) containing no element of the group consisting of Mo and W can be patterned. When the metal film (I) and the metal film (II) thus patterned are anodized by the method described later, the metal film (I) is formed into a conductive oxide film (I), and the metal film (II) Is formed into an insulating oxide film (II). In this way, an electric circuit can be formed on the substrate.
The patterned metal film (I) and metal film (II) can be laminated on the substrate in layers (see FIG. 12). When anodization is performed after forming a metal film having such a laminated structure, a multilayer electric circuit having a three-dimensional structure can be obtained. A multilayer electric circuit having a three-dimensional structure can also be obtained by repeating metal film formation and anodization for each layer.
The pattern formation method is not particularly limited. For example, a method of forming a metal film using a circuit pattern mask or a resist can be used.

(Metal film formation method)
The metal film can be formed by appropriately using a known film forming method. Specific examples include physical vapor deposition (PVD) methods such as vapor deposition and sputtering, chemical vapor deposition (CVD) methods such as MOCVD, synthesis methods from solutions such as sol-gel methods and chemical solution methods. . In a synthesis method from a solution such as a sol-gel method or a chemical solution method, a pattern can be formed using ink jet printing.

Among these, the vapor deposition method is preferable in that the film forming speed is high. Further, the sputtering method is particularly preferable in that a large-area film can be formed as used in the production of a large liquid crystal display.
Therefore, the metal film forming method in the present invention will be described by taking a sputtering method as an example.

  A well-known thing etc. can be used suitably for a sputtering device. For example, a DC magnetron sputtering apparatus can be used.

  For example, metal titanium and a dissimilar metal material are used as targets in order to form a metal film mainly composed of titanium. A titanium metal target in which different metals are uniformly added at an arbitrary composition ratio may be produced and used. As a method of easily changing the composition ratio, a method of disposing a chip or the like of a different metal material on a metal titanium target can be used. Since the composition of the metal film is determined by the area ratio of the metal titanium target and the dissimilar metal material chip, the size of the dissimilar metal material chip is adjusted so that the obtained metal film has a desired composition ratio. In order to obtain a uniform film quality, it is preferable to dispose a plurality of small dissimilar metal material chips evenly on the metal titanium target, rather than disposing dissimilar metal material chips in one place.

Next, the pressure in the vacuum chamber is reduced to about 5 × 10 ⁻⁵ Pa or less by a pump, an inert gas is introduced as a sputtering gas, and the pressure is adjusted to a predetermined sputtering pressure. The sputtering pressure is preferably about 0.1 to 5 Pa. As the inert gas, one or more selected from the group consisting of Ar, He, Ne, Kr and Xe can be used. Further, a reducing gas such as H ₂ may be introduced so as not to lower the sputtering rate.

  Subsequently, a predetermined voltage is applied to the target while maintaining the sputtering pressure. The substrate may be heated or not heated when the voltage is applied. Considering the heat resistance of the substrate, if necessary, the substrate may be cooled so that the temperature of the substrate is kept at about room temperature.

  The metal film 2 formed as described above preferably prevents the growth of a crystalline natural oxide film on the surface thereof. For example, after forming the titanium metal film 2 as described above, anodic oxidation is performed promptly (within 1 hour as the time of exposure to air). Further, the formed metal film can be stored by being submerged in ethanol. By doing in this way, the oxide film 3 is substantially comprised only by the anodic oxide film.

(anodization)
In the present invention, the metal film 2 is anodized at 0 ° C. or less to form the conductive oxide film 3. Anodization is usually performed by immersing a metal film in an electrolytic solution and applying a voltage using the metal film as an anode. In order to limit the range to be anodized, the surface of the metal film may be covered with a masking material and then anodized.
The electrolytic solution used for anodization is a solution containing an acid and / or a salt thereof. For example, examples of the acid and / or salt thereof include phosphoric acid, sulfuric acid, nitric acid, succinic acid, boric acid, adipic acid, and salts thereof. Of these, phosphoric acid and its salts are preferred.
The pH of the electrolyte is preferably 0-11. If it is this range, it will be easy to handle industrially and anodization can be performed stably.

  It is preferable to use an electrolytic solution containing at least one of phosphoric acid and a salt thereof because the light transmittance of the resulting oxide film 3 is increased. This is presumably because a part of phosphorus is taken into the anodic oxide film and crystallization of the anodic oxide film is hindered. In order to effectively obtain such an action, the concentration of phosphoric acid or a salt thereof in the electrolytic solution is preferably 1 mM to 1M, and more preferably 0.2M to 1M.

  Moreover, it is preferable to contain hydrogen peroxide in the electrolytic solution from the viewpoint that anodic oxidation can be performed stably. The concentration of hydrogen peroxide in the electrolytic solution is preferably maintained to be 0.1 to 50% by mass, more preferably maintained to be 0.1 to 40% by mass, More preferably, it is maintained at 20% by mass. Although the detailed mechanism of action of hydrogen peroxide is unknown, hydrogen peroxide functions as a depolarizer to prevent hydrogen gas bubbles, which are said to be generated on the anode, or as an oxidizer that helps anodize. It is estimated that

  The temperature during anodization is 0 ° C. or lower, preferably −30 to −3 ° C., more preferably −13 to −7 ° C. When the anodic oxidation temperature exceeds 0 ° C., crystallization of the anodic oxide film proceeds. On the other hand, if the temperature is too low, the amount of the antifreezing agent described later must be increased. Since the addition of the antifreezing agent increases the resistance value of the electrolytic solution, the amount of heat generated during anodization increases, and a device for maintaining a low temperature is required.

  In order to prevent the electrolytic solution from freezing at a temperature of 0 ° C. or lower, an appropriate amount of an antifreezing agent can be added to the electrolytic solution according to a desired anodizing temperature. Examples of the antifreezing agent include methanol, ethanol, diethylene glycol, ethylene glycol, glycerin, 1-propanol, 2-propanol, and butanol. If too much anti-freezing agent is added, the resistance of the electrolyte increases and the amount of heat generation increases. Therefore, it is most preferred to add the antifreeze agent in the minimum amount that can prevent freezing at the anodization temperature.

  The temperature may increase partially due to the anodic oxidation current and the heat generated by the oxidation reaction. Even if such a partial temperature rise occurs, it is necessary to actively keep the metal film 2 in an environment where the temperature is 0 ° C. or lower. For example, it may be maintained at 0 ° C. or lower while circulating the electrolyte using a circulation cooler or the like. Furthermore, it is preferable to keep the environment around the anodizing device at a low temperature using a thermostatic bath or a thermostatic chamber from the viewpoint of suppressing temperature changes.

Anodization is performed, for example, with the following voltage-current. In the initial stage of anodization, the applied voltage is gradually increased so as to have a constant current density (constant current anodization process), and after reaching a specified voltage (anodization voltage), it is maintained at a constant voltage. (Constant voltage anodizing process).
The anodizing voltage is defined according to the thickness of the metal film. The anodic oxidation voltage is preferably 0.75 to 1.25 V per 1 nm thickness of the metal film. By selecting the anodic oxidation voltage, all of the metal film can be formed into an oxide film, or only a part of the metal film (only the surface layer) can be formed into an oxide film.
The current density until the applied voltage reaches a specified anodizing voltage (constant current anodizing process) is preferably 0.1 to 1000 mA / cm ^2, and preferably 0.1 to 100 mA / cm ^2. More preferred. If the current density is too low, the time required for anodic oxidation becomes longer. On the other hand, if the current density is too high, the amount of heat generation increases, so the cooling device becomes large.

The timing for stopping the anodization is appropriately selected. The preferred stop time is from the time when the applied voltage reaches the specified anodic oxidation voltage to the time when the current density becomes 1 μA / cm ² or less.
The time from when the anodic oxidation voltage is reached until the anodic oxidation is stopped is preferably 0 to 400 minutes. If it is this range, possibility that crystal growth will arise in an oxide film is low.

  When the metal film 2 is anodized by the method as described above, the transparent conductive oxide film 3 can be obtained.

(Transparent conductive film)
The oxide film 3 obtained in this way has good conductivity. The resistivity of the oxide film 3 is usually 10 ⁻² to 10 ⁻⁴ Ω · cm. In general, a conductor refers to one having a resistivity at room temperature of 10 ⁰ Ωcm or less. When the resistivity at room temperature is 10 ⁻³ Ωcm or less, the application is further expanded. From such points, the transparent conductive film of the present invention is excellent as a conductor.

  The oxide film 3 is preferably amorphous. Even if a few crystal grains are present in the oxide film 3, there is no problem, but when this crystal grows, the light transmittance tends to decrease. Since the oxide film is amorphous, even when the film is bent or rolled, the conductivity and transparency are hardly lowered. Since amorphous titanium oxide has a refractive index (wavelength 632.8 nm) of about 1.90 to about 2.35, an oxide film can be obtained by using a substrate made of a material having a higher refractive index. 3 can function as an antireflection film.

  The transparent conductive material or transparent conductive film obtained by the production method of the present invention has good transparency. Specifically, a light transmittance of 50% or more is obtained in a wide range including visible light having a wavelength of 360 nm to 2.4 μm. Therefore, it is suitable as a conductor that requires transparency in a wide wavelength range. The thickness of the oxide film is preferably 20 to 250 nm from the viewpoint of achieving both transparency and conductivity.

  A titanium metal film (I) containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W, and a group consisting of Zr, Hf, Nb, Ta, Mo and W When the titanium metal film (II) containing no element is patterned, the conductive oxide film (I) and the insulating oxide film (II) are obtained by anodic oxidation. The conductive oxide film (I) has the same resistivity as that of the oxide film 3. On the other hand, the insulating oxide film (II) usually has a relative dielectric constant of 30 to 50. The insulating oxide film (II) is preferably amorphous. The insulating oxide film (II) preferably has the same light transmittance as that of the oxide film 3.

Since the manufacturing method of the present invention does not require an annealing treatment at a high temperature as described in Patent Document 3, not only on a substrate made of a high heat-resistant material such as a glass substrate and a silicon substrate, but also polyethylene, polypropylene, and polyethylene terephthalate. A conductive film can also be formed on a substrate made of a low heat resistant material such as a resin. Therefore, the range of substrate selection is wide and manufacturing is easy. If the substrate is a thin resin sheet, it can be rolled by hand and has a wide range of applicable applications.
As described above, by using the method of the present invention, it is possible to obtain the transparent conductive material 10 in which the oxide film 3 having transparent conductivity is formed on various substrates 1.

(Use)
The transparent conductive material and the transparent conductive film obtained by the production method of the present invention have a wide range of applications and can be used for various electronic devices. For example, application to transparent electrodes such as flat panel displays, solar cells, and touch panels is conceivable. In addition, it can be applied to shielding of electromagnetic waves used for the antireflection film, a film that prevents dust from being attached by static electricity, an antistatic film, and ultraviolet reflection glass. If only a surface layer of the film is anodized while a metal film having a sufficient thickness is applied in sputtering, a layer made of a metal film not anodized and a layer made of an oxide film obtained by anodization It can also be applied as a multilayer antireflection film.

  Examples of applications as transparent electrodes include dye-sensitized solar cells, display panels, organic EL panels, light-emitting elements, light-emitting diodes (LEDs), white LEDs and laser transparent electrodes, surface-emitting laser transparent electrodes, illumination devices, and optical communications Examples thereof include devices.

  Further specific applications include a transparent conductive film in a liquid crystal display (LCD), a transparent conductive film in a color filter portion of the LCD, a transparent conductive film in an EL (Electro Luminescence) display, a plasma display panel (PDP) ) Transparent conductive film, PDP optical filter, transparent conductive film for shielding electromagnetic waves, transparent conductive film for surface reflection prevention, transparent conductive film for improving color reproducibility, for damage prevention Transparent conductive film, optical filter, touch panel (resistive touch panel, electromagnetic induction touch panel, ultrasonic touch panel, optical touch panel, capacitive touch panel, resistive touch panel for portable information terminals, inner integrated with display Touch panels, etc.), solar cells (amorphous silicon (a- i) system solar cells, microcrystalline Si thin film solar cells, CIGS solar cells, dye-sensitized solar cells (DSC), etc.), transparent conductive materials for static electricity prevention of electronic parts, transparent conductive material light control materials for antistatic, Examples thereof include an optical mirror, a heating element (surface heater, electrothermal glass, etc.), electromagnetic wave shielding glass, thermophotovoltaic cell and the like.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the present invention.

(Examples 1-3)
<Metal film formation>
Metallic titanium (purity 99.995%, 75 mmφ) manufactured by Nikko Metal Co., Ltd. was installed as a target in a DC sputtering apparatus (SPF-332H manufactured by Nidec Anelva). Further, metallic niobium (additive element) chips were evenly arranged on the metallic titanium. The area ratio of metal titanium and metal niobium is almost the same as the atomic ratio in the resulting metal film. The number of metal niobium chips arranged was adjusted so that the area of metal niobium was 4%, 8%, and 12%.

  The substrate was set on a sample stage that also served as an anode at a position facing the target. The sample stage is rotated four times per minute so that a uniform film can be formed. A slide glass (76 mm × 26 mm × 1 mm) was used as the substrate.

The inside of the chamber of the sputtering apparatus was depressurized to 5 × 10 ⁻⁴ Pa or less with a vacuum pump, and then Ar gas was introduced to reach about 1 Pa.
Subsequently, sputtering was performed for 50 seconds with an output of 0.5 kW using Ar as a sputtering gas without heating the substrate. A 20 nm thick Ti—Nb metal film was obtained on the substrate.

The proportions of niobium element in the metal film were 4 atom%, 8 atom%, and 12 atom% in Examples 1, 2, and 3, respectively.
In addition, Nb content in a metal film was quantified by EDS in JSM-7000F made by JEOL. The thickness of the metal film was determined by Dektak 8 manufactured by ULVAC.
In order to prevent oxidation of the obtained metal film as much as possible, the substrate on which the metal film was formed was stored in ethanol.

<anodization>
The substrate on which the metal film was formed was immersed in an electrolytic solution maintained at −10 ° C., and anodization was performed with the metal film as the anode side. As the electrolytic solution, an aqueous solution of 22.4% by mass of ethanol, 7.5% by mass of phosphoric acid and 3.7% by mass of hydrogen peroxide was used. Anodization was started at a constant current of 0.055 mA / cm ² , and when the voltage reached 25 V (anodization voltage), the anodization was stopped. The metal film was formed into an oxide film by this anodic oxidation. The substrate was taken out of the electrolytic solution, washed with water, and dried to obtain a transparent conductive material. Transparency and conductivity were measured by the following methods. The results are shown in Table 1 and FIG.

〔transparency〕
The light transmittance of the transparent conductive material was measured in a wavelength range of 340 to 1100 nm using UV-3100S manufactured by Shimadzu Corporation.

〔Conductivity〕
The resistivity of the oxide film was measured by a four-probe method using a Loresta ip manufactured by Mitsubishi Oil Corporation.

(Comparative Example 1)
An oxide film was obtained on the substrate in the same manner as in Example 1 except that only metal titanium was used as a target (indicated in the table as Nb content or Ta content 0 atomic%). . Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 1 and FIG.

  From Table 1, it can be seen that when a titanium metal film containing Ti (Ti-Nb metal film) is anodized, an oxide film having good conductivity can be obtained. 3 that the transparent conductive material of the present invention (Examples 1 to 3) has a higher light transmittance in the visible light region than that of Comparative Example 1.

(Examples 4 and 5)
An oxide film and a transparent conductive material were obtained in the same manner as in Examples 1 and 2 except that a metal tantalum chip was used instead of the metal niobium chip. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 2 and FIG.
The Ta content in the metal film was quantified by EDS in JSM-7000F manufactured by JEOL Ltd. Further, the thickness of the metal film was determined using Dektak 8 manufactured by ULVAC, and all of Examples 4 and 5 were 20 nm.

  From Table 2, it can be seen that when a titanium metal film containing Ta (Ti-Ta metal film) is anodized, an oxide film having good conductivity can be obtained. Further, FIG. 4 shows that the transparent conductive material of the present invention (Examples 4 and 5) has a higher light transmittance in the blue to ultraviolet region than Comparative Example 1. In addition, absorption near 340 nm is absorption by the slide glass used for the base | substrate.

(Example 6)
An oxide film and a transparent conductive material were obtained in the same manner as in Example 1 except that the sputtering time was changed from 50 seconds to 140 seconds and the anodic oxidation voltage was changed from 25 V to 60 V. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 3 and FIG. In addition, the thickness of the metal film was calculated | required using Dektak8 by ULVAC.

  From Table 3, the thickness of the Ti—Nb metal film or oxide film can be controlled by changing the sputtering conditions and the anodic oxidation conditions, and the obtained oxide film is transparent and has good conductivity. It can be seen that it is.

(Example 7)
An oxide film and a transparent conductive material were obtained in the same manner as in Example 4 except that the sputtering time was changed from 50 seconds to 140 seconds and the anodic oxidation voltage was changed from 25 V to 80 V. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 4 and FIG. In addition, the thickness of the metal film was calculated | required using Dektak8 by ULVAC.

  From Table 4, the thickness of the Ti-Ta metal film or oxide film can be controlled by changing the sputtering conditions and the anodic oxidation conditions, and the obtained oxide film is transparent and has good conductivity. It can be seen that it is.

(Examples 8 and 9)
An oxide film and a transparent conductive material were obtained in the same manner as in Example 1 except that the anodic oxidation voltage was changed from 25 V to 5 V and 15 V, respectively. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 5, FIG. 2 and FIG. Note that the X-ray diffraction pattern of FIG. 2 was measured using X'pert PRO MPD manufactured by Panalical.

(Comparative Example 2)
A metal film was obtained in the same manner as in Example 1 except that the anodic oxidation was not performed (in the table, the anodic oxidation voltage was expressed as 0 V). Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 5, FIG. 2 and FIG.

  From Table 5, it can be seen that the light transmittance increases as the anodic oxidation voltage increases. In particular, it can be seen that the light transmittance is remarkably increased by an anodic oxidation voltage of 15 V or more.

  As shown in FIG. 2, in the metal film not subjected to anodic oxidation (Comparative Example 2), in addition to the broad structure derived from the slide glass used for the substrate, a peak derived from metal titanium is seen at around 38 °. As the anodic oxidation voltage increases, the intensity of the peak near 38 ° decreases, and the peak derived from metallic titanium disappears in the film having the anodic oxidation voltage of 25V. This shows that the Ti—Nb metal film is completely anodized. It can be seen that the anodized film has no other X-ray diffraction peaks and is amorphous.

(Example 10)
An electrolytic solution used for anodization was obtained by mixing 350 ml of pure water, 150 ml of ethanol, 40 g of triammonium phosphate and 20 g of 30% hydrogen peroxide at room temperature, cooling this to −10 ° C., and removing the precipitate. An oxide film and a transparent conductive material were obtained in the same manner as in Example 3 except that the solution was changed to a solution (pH: about 9). Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 6 and FIG.

  As shown in Table 6 and FIG. 8, it can be seen that good transparency and conductivity can be obtained even with an alkaline electrolyte.

(Example 11)
The same method as in Example 1 except that when the voltage reaches 25 V, the anodization is not stopped, the voltage 25 V is maintained as it is, and the anodization is stopped when the current density becomes 1 μA / cm ² or less. Thus, an oxide film and a transparent conductive material were obtained. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 7 and FIG.

From the above results, it can be seen that good conductivity and transparency can be obtained even when anodic oxidation is continued until the current density falls below 1 μA / cm ² . That is, since the characteristics such as resistivity and light transmittance are not sensitive to the anodic oxidation stop timing, the method of the present invention is industrially easy to handle.

(Example 12)
An oxide film and a transparent conductive material were obtained in the same manner as in Example 1 except that the substrate was changed from a slide glass to a PET (polyethylene terephthalate) film. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 8 and FIG.

  From the above results, it can be seen that if this production method is used, an oxide film having good conductivity and transparency can be formed on a low heat resistant substrate such as a PET film.

  Moreover, the transparent conductive film obtained in Example 12 was wound around a 10 mmφ cylinder, and the resistivity was measured in that state. Moreover, the transparent conductive film obtained in Example 12 was bent 20 times, and then the resistivity was measured. There was no change in resistivity in the wound state or after 20 bends.

(Comparative Example 3)
An oxide film and a transparent conductive material were obtained in the same manner as in Example 1 except that the temperature of the electrolytic solution during anodization was changed to 20 ° C. Transparency and conductivity were measured by the same method as in Example 1. The results are shown in Table 9 and FIG.

  From the above results, it can be seen that when the temperature of the electrolyte during anodization exceeds 0 ° C., conductivity is hardly obtained and the light transmittance is low.

  The transparent conductive film and transparent conductive material of the present invention can be applied to uses such as a transparent electrode, a heating element, and an electromagnetic wave shielding film.

1: Substrate 2: Metal film 3: Oxide film (transparent conductive film)
10: Transparent conductive material.
(I): Conductive oxide film
(II): Insulating oxide film A: A layer B: B layer C: C layer

Claims (25)

  A titanium metal film containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo, and W is formed on a substrate, and all or part of the metal film is an anode at 0 ° C. or less. A method for producing a transparent conductive material comprising a step of forming a conductive oxide film by oxidation.   2. The method for producing a transparent conductive material according to claim 1, wherein the substrate is made of at least one material selected from the group consisting of glass, resin, and semiconductor material.   The method for producing a transparent conductive material according to claim 1, wherein the substrate is a flat plate, a sheet, or a film.   The metal film is formed by at least one method selected from the group consisting of a physical vapor deposition method, a chemical vapor deposition method, a sol-gel method, and a synthesis method from a solution. The manufacturing method of the transparent conductive material of description.   The transparent according to any one of claims 1 to 4, wherein the sum of at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W in the metal film is 2 to 15 atomic%. A method for producing a conductive material.   The method for producing a transparent conductive material according to claim 1, wherein the metal film is an alloy having titanium as a base metal.   The method for producing a transparent conductive material according to claim 1, wherein the metal film has a thickness of 20 to 200 nm. A titanium metal film (I) containing at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mo and W, and Zr, Hf, Nb, Ta, Mo and W on the substrate Patterning a titanium metal film (II) that does not contain elements of the group,
A transparent conductive material having a step of forming a conductive oxide film (I) and an insulating oxide film (II) by anodizing the metal film (I) and the metal film (II) at 0 ° C. or less. Production method.   The method for producing a transparent conductive material according to any one of claims 1 to 8, wherein the anodic oxidation is performed in an aqueous solution containing an acid or a salt thereof, hydrogen peroxide and an antifreezing agent.   The method for producing a transparent conductive material according to claim 1, wherein the anodization is performed at −30 to −3 ° C.   The method for producing a transparent conductive material according to any one of claims 1 to 10, wherein an anodic oxidation voltage is 0.75 V to 1.25 V per 1 nm of the thickness of the metal film. The transparent conductive material according to any one of claims 1 to 11, wherein the anodic oxidation is stopped from when the applied voltage reaches a specified anodic oxidation voltage until the current density becomes 1 µA / cm ² or less. Method for producing a functional material.   The transparent conductive material according to any one of claims 1 to 11, wherein the anodization is stopped during a period from when the applied voltage reaches a specified anodization voltage until 400 minutes have elapsed since the arrival. Production method. Current densities of up to the applied voltage reaches the anodic oxidation voltage paragraphs is the 0.1~1000mA / cm ^2, the production method of the transparent conductive material according to any one of claims 1 to 13.   The transparent conductive material which has a transparent conductive oxide film obtained by the manufacturing method of Claims 1-14.   The transparent conductive material according to claim 15, wherein the oxide film is amorphous. 16. The oxide film has a thickness of 20 to 250 nm, a resistivity of 10 ⁻² to 10 ⁻⁴ Ω · cm, and a light transmittance of 50% or more in a wavelength range of 360 nm to 2.4 μm. Or the transparent conductive material of 16.   A transparent electrode comprising the transparent conductive material according to claim 15.   An electronic device comprising the transparent conductive material according to claim 15.   A solar cell comprising the transparent conductive material according to claim 15.   The manufacturing method of a transparent conductive film which has the process of obtaining a transparent conductive material with the manufacturing method of Claims 1-14, and then removing a base | substrate.   The transparent conductive film obtained by the manufacturing method of Claim 21.   A transparent electrode comprising the transparent conductive film according to claim 22.   An electronic apparatus comprising the transparent conductive film according to claim 22.   A solar cell comprising the transparent conductive film according to claim 22.

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