JP5824920B2 - Transparent conductive film, conductive member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a transparent conductive film that can be used for various thin displays, touch panels, solar cells, biostimulation electrodes, and the like, a conductive member, and a method for manufacturing the same.

The transparent conductive film used for electronic devices such as liquid crystal displays is mainly made of ITO (Indium Tin Oxide), but In, which is the main material, is a rare metal and has a resource risk. Therefore, there is a transparent conductive film made of Al-doped ZnO (AZO) in which Al ³⁺ is added to resource-rich zinc oxide (ZnO), and a transparent conductive film made of Ga-doped ZnO (GZO) in which Ga ³⁺ is added to ZnO. Proposed.

Recently, a Ti-based transparent conductive film, which is abundant in resources and chemically stable, has been proposed. For example, a transparent conductive film made of TiN, a transparent conductive film made of Nb-doped TiO _{2 in} which Nb is added to TiO ₂ (Non-patent Document 1), a transparent conductive film made of TiON (Patent Document 1), and the like.

JP 2011-21237 A

Y. Furubayashi, et al., "A transparent metal: Nb-doped anatase TiO2", APPLIED PHYSICS LETTERS, Vol.86, 252101, 2005.

A ZnO-based transparent conductive film has a problem in terms of heat resistance and moisture resistance. A transparent conductive film made of TiN has a low resistivity and excellent conductivity, but has a brown or golden color and has a problem in transparency. A transparent conductive film made of Nb-doped TiO ₂ involves a resource risk because Nb is a rare metal.

  The present invention has been made in view of such circumstances, and is fundamentally different from such a conventional transparent conductive film, has a low resource risk, and exhibits a new conductivity and transparency. An object of the present invention is to provide a transparent conductive film. Moreover, it aims at providing the conductive member which formed the transparent conductive film into a film on a base material, and its manufacturing method collectively.

  As a result of intensive research and trial and error in order to solve this problem, the present inventor has a composition different from that of the conventional transparent conductive film. It has been newly found that a film made of a material exhibits very excellent transparency and conductivity. The present inventor has developed various innovative inventions described below by developing this epoch-making result.

<Transparent conductive film>
(1) That is, the transparent conductive film of the present invention contains Ti, P, O, and N as essential elements, and an N atomic ratio that is a ratio of the number of N atoms to the total number of Ti atoms and N atoms ( N / Ti + N) is 0.35-0.65, and wherein the Rukoto to have a transparent and conductive.

(2) The transparent conductive film of the present invention is composed of Ti, P, O and N, and does not require a rare element with a resource risk. Therefore, according to the present invention, a transparent conductive film having excellent characteristics can be stably supplied at a low cost. Moreover, since the transparent conductive film of the present invention is a Ti-based transparent conductive film, it is considered that at least a part thereof is excellent in corrosion resistance.

By the way, the reason why the transparent conductive film of the present invention exhibits excellent transparency and conductivity is not necessarily clear. The current situation is considered as follows. First, as described above, the TiO ₂ film has high transparency, but has high resistivity and low conductivity. Conversely, a TiN film has low resistivity and excellent conductivity, but is inferior in transparency.

In the transparent conductive film of the present invention, a part of Ti is replaced by P by adding P to such a Ti-based film, and the transparency of the TiO ₂ film and the conductivity of the TiN film are compatible at a high level. It is considered that a transparent conductive film has been formed. The transparent conductive film of the present invention may be specialized for only one of transparency and conductivity. That is, the transparent conductive film of the present invention may be one in which either transparency or conductivity is preferentially enhanced with respect to the other according to the required specifications.

(3) As a result of intensive studies by the inventors, it has been found that at least a part of the transparent conductive film according to the present invention has an amorphous structure. Of course, as long as transparency and the like are ensured, the transparent conductive film of the present invention may be an amorphous phase alone or a mixture of an amorphous phase and a crystalline phase.

《Conductive member》
(1) This invention is grasped | ascertained not only as a transparent conductive film but as a conductive member which provided the transparent conductive film on the surface of a base material. In other words, the present invention may be a conductive member comprising a base material and the transparent conductive film of the present invention formed on at least a part of the surface of the base material.

(2) The base material referred to in this specification may be any material, characteristic, shape, size, or the like. For example, the substrate may be a transparent body such as glass or an opaque body such as metal, resin, or ceramic.

<< Method for Producing Conductive Member >>
The method for forming the transparent conductive film and the method for manufacturing the conductive member of the present invention are not limited. For example, the conductive member described above can be easily performed by a film forming process in which a film made of Ti, P, O, and N is formed on a substrate by physical or chemical vapor deposition (PVD or CVD).

<Others>
(1) In addition to the essential elements (Ti, P, O, and N) described above, the transparent conductive film of the present invention improves the characteristics of the transparent conductive film or does not adversely affect the characteristics. Inevitable impurities ". An arbitrary element is 1 or more types, such as vanadium (V), manganese (Mn), silicon (Si), iron (Fe), nickel (Ni), for example. Inevitable impurities are elements that are difficult to remove for cost or technical reasons.

(2) “Transparency” as used herein is indicated by, for example, transmittance. The degree is not limited, but it is 40% or more.

(3) “Conductivity” as used herein is indicated by, for example, (volume) resistivity. The degree is not limited, but dare to say, it is preferably 1 × 10 ⁻³ Ω · m or less, more preferably 1 × 10 ⁻⁴ Ω · m or less.

(4) The transparent conductive film of the present invention is preferably excellent in corrosion resistance (chemical stability) in addition to transparency and conductivity. “Corrosion resistance” in this case is indicated by, for example, a corrosion current density (exchange current density). The degree is not limited, but it is 100 μA / cm ² or less (in 5% sulfuric acid).

(5) Unless otherwise specified, “x to y” in this specification includes the lower limit value x and the upper limit value y. Furthermore, a new arbitrary numerical range “ab” can be configured by appropriately combining numerical values described in the present specification and arbitrary numerical values included in “x to y” thereof.

Sample No. 1 is a photograph showing transparency of a film according to 1. Sample No. 2 is a photograph showing transparency of a film according to 2; Sample No. It is a photograph which shows the transparency of the film | membrane which concerns on C1. Sample No. 2 is a graph showing an X-ray diffraction pattern according to 2;

  The present invention will be described in more detail with reference to embodiments of the invention. The contents described in this specification can be applied not only to the transparent conductive film according to the present invention but also to a conductive member and a manufacturing method (or a film forming method) thereof. One or two or more components arbitrarily selected from the present specification can be added to the above-described components of the present invention. If understood as a product-by-process, the content relating to the manufacturing method and the like can be a constituent element relating to the transparent conductive film and the conductive member. Note that which embodiment is the best depends on the target, required performance, and the like.

<Transparent conductive film>
(1) Composition At least a part of the transparent conductive film of the present invention is not crystalline as in the conventional transparent conductive film, but is amorphous. For this reason, the transparent conductive film of the present invention can have a relatively wide ratio of essential elements (Ti, P, O, and N) that exhibit transparency and conductivity.

  However, at present, when the entire transparent conductive film is 100 atomic% (simply referred to as “%”), P: 13 to 25%, further 15 to 20%, O: 7 to 40%, or 9 to 25%. N: 10 to 50%, further 30 to 47%, and it is considered that the balance is preferably composed of Ti and an optional modifying element (optional element) and / or inevitable impurities. Note that Ti is preferably 20 to 70%, more preferably 25 to 50%. When one or more of these essential elements are too small or excessive, the transparency or conductivity of the transparent conductive film may be lowered.

  The Ti atomic ratio (Ti / (Ti + P)), which is the ratio of the number of Ti atoms to the total number of Ti atoms and P atoms, is 0.5 to 0.8, and further 0.6 to 0.7. The transparent conductive film is particularly excellent in both transparency and conductivity.

  This means that the N atomic ratio (N / Ti + N), which is the ratio of the number of N atoms to the total number of Ti atoms and N atoms, is 0.35 to 0.7, and further 0.35 to 0.00. The same applies to 65.

  The transparent conductive film of the present invention may contain various optional elements as described above in addition to the essential elements described above. As long as the transparent conductive film is an amorphous material, the ratio of the arbitrary element is relatively wide. For example, V: 0.5 to 10%, further 3 to 7%, Ni: 0.5 to 10%, further 0.5 to 3%, Si: 0.5 to 10%, further 3 to 7%. And preferred. If it is such a range, the transparent conductive film excellent in transparency and electroconductivity will be obtained. In addition to these elements, for example, manganese (Mn), cobalt (Co), chromium (Cr), boron (B), and the like can be optional elements.

(2) Structure Since the amorphous body constituting the transparent conductive film of the present invention does not have a clear crystal structure, it is basically homogeneous or isotropic. For this reason, there are almost no crystal grain boundaries or lattice defects, which become the starting point of corrosion, and it can be excellent not only in transparency but also in corrosion resistance.

  This amorphous body is sufficient if it does not allow strong diffraction to be detected by an X-ray diffractometer (XRD). In addition to an amorphous crystal that does not have a complete crystal structure, a latent crystal that can detect weak diffraction by XRD. Including quality.

  In addition, the composition range may change in the amorphous body in the thickness direction from the outermost layer to the substrate. Furthermore, the composition range may vary depending on the amorphous region.

  The transparent conductive film of the present invention can exhibit sufficient transparency as well as conductivity even when the film thickness is relatively small as well as when the film thickness is small. However, the film thickness of the transparent conductive film is preferably 10 to 1000 nm, more preferably 50 to 300 nm, from the viewpoint of achieving both transparency and durability.

《Conductive member》
The conductive member of the present invention may be any member as long as the above-described transparent conductive film is formed on at least a part of the surface of the substrate. This conductive member may be a laminate of transparent conductive films having different compositions. In addition, the intermediate layer used as the base layer or support layer of a transparent conductive film may be on the surface of a base material. The transparent conductive film may not only simply cover the surface of the substrate, but may be integrated with the substrate in the vicinity of the surface.

"Production method"
(1) Film-forming process The specific method of the film-forming process which forms a transparent conductive film on a base material does not ask | require. For example, a vapor deposition method including sputtering (PVD, CVD) or a vapor deposition method under a reactive atmosphere (reactive sputtering or the like) can be used. An appropriate method may be selected in consideration of the material / morphology / characteristics of the substrate, the composition and film thickness of the transparent conductive film, and the like. Among these, sputtering that can efficiently form a uniform transparent conductive film is preferable.

  In particular, when the film forming process is performed by magnetron sputtering, the film forming speed is relatively fast, which is preferable in terms of productivity.

N contained in the transparent conductive film of the present invention can be introduced into the film by adjusting the treatment atmosphere during sputtering. That is, the film forming process can be a reactive sputtering process in which sputtering is performed in a processing atmosphere composed of a mixed gas of an inert gas and nitrogen (N ₂ ) gas using a target containing at least Ti and P.

  When reactive sputtering is performed, sputtering can be performed without using a complicated system target, and an element of a gas component that easily causes a composition shift at the time of sputtering can be stably supplied. Therefore, a film having a desired composition can be formed. .

O constituting the transparent conductive film may use a target as a supply source, or may mix oxygen (O ₂ ) gas as a reactive gas in the reactive sputtering treatment atmosphere.

  The characteristics and composition of the transparent conductive film are influenced not only by the film forming method but also by the characteristics of the target. In the case of forming a transparent conductive film by vapor deposition (including sputtering), it is preferable to use a target obtained by a discharge plasma sintering method (SPS) or the like because a refractory compound target can be densely produced. Incidentally, SPS is a method in which a large amount of pulsed current is applied at a low voltage to the particle gap of the green compact of the raw material powder that is the target, and each particle is sintered by the discharge plasma energy generated instantaneously between the particles. It is.

  In addition, a transparent conductive film is formed by a pulsed laser deposition (PLD) method in which a target placed in a vacuum chamber is irradiated with laser light from outside the chamber and atoms of basic elements generated from the target are deposited on a substrate. May be formed. At this time, if the number of laser pulses for ablating the target (evaporation, sublimation, peeling, etc.) is adjusted, the film forming speed can be precisely controlled.

  Note that a part of the essential elements (particularly Ti) forming the transparent conductive film can be supplied from the substrate side depending on the film forming method. Further, N constituting the transparent conductive film may be introduced into the film by a nitriding method such as gas nitriding, ion nitriding, salt bath nitriding or the like.

<Application>
The use of the transparent conductive film of the present invention is not particularly limited, and it can be used for various things. For example, as described above, it is suitable for thin displays, touch panels, solar cells, biostimulation electrodes, and the like. The conductive member having the transparent conductive film on the substrate is not limited to the final product or a form close thereto, and may be an intermediate member or the like.

The present invention will be described more specifically with reference to examples.
<Production of sample>
(1) A transparent glass substrate (base material) made of alumina silica glass was prepared. A film was formed on this substrate by magnetron sputtering (film formation process). The target used at this time was obtained by spark plasma sintering (SPS) of a mixed powder in which TiP powder (10 to 100 μm) and Ti powder (10 to 100 μm) were uniformly mixed with a rocking mixer. The atomic ratio of Ti and P existing in the target (Ti atomic ratio: Ti / (Ti + P)) was 0.75 (Ti: P = 3: 1).

  Note that O introduced into the film was oxygen (oxide) attached to the particle surface of the mixed powder as a supply source. Of course, O may be mixed into the target via titanium oxide or the like, or oxygen as a reactive gas may be introduced into the sputtering atmosphere (processing atmosphere).

  Furthermore, when introducing the arbitrary elements shown in Table 1 into the film, pure powder of each element was mixed in the mixed powder serving as the target raw material.

Magnetron sputtering was performed in a mixed gas atmosphere (sputtering atmosphere) of Ar (discharge gas) and N ₂ (reactive gas) under conditions of 100 W, 1 hour, and 0.5 Pa (reactive sputtering step). Table 1 shows the ratio of Ar and N ₂ flow rates (unit: sccm) in the sputtering atmosphere. Note that the temperature of the substrate on which the film was formed (substrate temperature) was 25 ° C.

  In this way, each sample shown in Table 1 formed into a film on the glass substrate was obtained (sample No. 1-5).

(2) Instead of the above target, a sample using TiN as a target was similarly produced by the above-described sputtering. This sample is also shown in Table 1 (Sample No. C1).

<Observation of film>
(1) About each sample shown in Table 1, the composition analysis of the film | membrane was performed by Rutherford backscattering analysis (RBS). The measurement at this time was performed under the conditions of ion species: He, ion energy: 1.8 MeV, scattering angle: 160 °, and vacuum degree of scattering tank: 3 × 10 ⁻⁶ Torr. The results are shown in Table 1. The atomic ratios based on the analysis results are also shown in Table 1.

(2) The crystal structure of the film of each sample was analyzed with an X-ray diffractometer (XRD). In either case, a sharp peak did not appear, and it was confirmed that each film had an amorphous structure. As an example, sample no. The X-ray diffraction pattern for 2 is shown in FIG.

(3) As for all the samples, as shown in FIG. 1, the pattern arrange | positioned on the back side of the film-formed glass substrate was fully appreciable. However, sample no. The film thickness of C1 was about 1/3 of the film thickness of other samples. Incidentally, the film thickness of each sample was measured with a stylus type surface shape measuring instrument. The results are also shown in Table 1.

"Conductivity"
The volume resistivity, which is an index of the conductivity of the film of each sample, was measured by the four probe method.

<Evaluation>
(1) As is clear from Table 1 and FIG. 1, the transparent conductive film composed of Ti, P, O, and N (essential elements) has excellent transparency (high transmittance) even when the film thickness is considerably large. ), And the resistivity is sufficiently small to be highly conductive. This tendency was the same even when V, Mn, Si or Fe (arbitrary element) was included.

(2) Although the film made of TiN was also quite transparent, it is considered that the film thickness was considerably thin.

Claims (9)

Titanium (Ti), phosphorus (P), oxygen (O) and nitrogen (N) are essential elements ,
The N atomic ratio (N / Ti + N), which is the ratio of the number of N atoms to the total number of Ti atoms and N atoms, is 0.35 to 0.65,
The transparent conductive film according to claim Rukoto to have a transparent and conductive.   The transparent conductive film according to claim 1, comprising an amorphous body.   P: 13 to 25%, O: 7 to 40% and N: 10 to 50% when the whole is 100 atomic% (simply referred to as “%”), and the balance is made of Ti and inevitable impurities Item 3. The transparent conductive film according to Item 1 or 2.   The transparent conductive film according to claim 3, wherein a Ti atomic ratio (Ti / (Ti + P)), which is a ratio of the number of Ti atoms to the total number of Ti atoms and P atoms, is 0.5 to 0.8. .   Furthermore, the transparent conductive film in any one of Claims 1-4 containing the arbitrary elements which are 1 or more types of vanadium (V), manganese (Mn), silicon (Si), or iron (Fe). Having a film forming step of forming a film on a substrate by vapor deposition;
A method for producing a conductive member, comprising obtaining a conductive member comprising the base material coated with the transparent conductive film according to claim 1. The film-forming step, at least by using a target containing Ti and P, inert gas and nitrogen (N ₂₎ according to claim 6, wherein the reactive sputtering step of sputtering in the treatment atmosphere comprising a mixed gas of the gas A method for producing a conductive member. The method for manufacturing a conductive member according to claim 7, wherein the mixed gas further contains oxygen (O ₂ ) gas. A substrate;
The transparent conductive film according to any one of claims 1 to 5, formed on at least a part of the surface of the substrate,
A conductive member comprising: