JP2017226922A - Production method of transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a transparent conductive film capable of depositing at higher speed a transparent conductive layer having a lowered resistance.SOLUTION: In a production method of a transparent conductive film including a step for forming a transparent conductive layer by a sputtering method from a target containing an indium-tin complex oxide on a substrate film, the sputtering method is a DC dual target sputtering method performed by connecting a DC power source respectively to two targets provided per sputtering chamber in a sputtering film deposition apparatus.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a transparent conductive film.

  In recent years, a projected capacitive touch panel and a matrix resistive touch panel are capable of multi-point input (multi-touch), and thus have excellent operability, and their demand is rapidly increasing. As an electrode member of such a touch panel, a transparent conductive film in which a transparent conductive thin film is formed on a base film has been proposed. The application of the transparent conductive thin film is generally performed by forming an indium-tin composite oxide film by sputtering in a vacuum environment (Patent Document 1).

JP 2009-076432 A

  In particular, while the market for display products with touch panels is expanding, there is an increasing demand for transparent conductive films having a transparent conductive layer with low resistance (high conductivity) for the purpose of low power consumption. Further, in order to cope with such an increase in demand, film formation at a higher speed is required.

  An object of this invention is to provide the manufacturing method of the transparent conductive film which can form the transparent conductive layer by which resistance was reduced at higher speed.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by the following constitution, and have arrived at the present invention.

That is, the present invention is a method for producing a transparent conductive film comprising a step of forming a transparent conductive layer by sputtering from a target containing indium-tin composite oxide on a base film,
The sputtering method is a DC dual target sputtering method performed by connecting a DC power source to each of the two targets provided per sputtering chamber in the sputtering film forming apparatus.

  In the manufacturing method, a DC dual target sputtering method in which a DC power source is connected to each of the two targets provided per sputtering chamber is employed as a sputtering method when forming the transparent conductive layer. The sputtering speed can be doubled as compared with the single target sputtering method, and the film forming process can be accelerated. Moreover, the plasma density in the sputtering chamber can be increased by installing two targets in one sputtering chamber. As a result, a denser sputtered film can be formed, and the specific resistance of the obtained transparent conductive layer can be reduced. Note that in a conventional sputter deposition apparatus having one target in one sputtering chamber, the plasma density can be increased by increasing the output of the DC power source. However, if the output is increased too much, the load on the target will increase, causing cracks and nodules (a state of being burnt due to foreign matter), so the output that can be loaded on the target will be limited. Therefore, it is not possible to reduce the resistance as much as the DC dual target sputtering method and increase the speed of sputtering film formation.

  The shortest distance between the two targets is preferably 10 mm or more and 150 mm or less. By setting the shortest distance between the targets to be equal to or more than the above lower limit, it is possible to prevent interference between magnetic fields when a magnetic field is applied together with DC power to form a transparent conductive layer having good film quality. On the other hand, by setting the shortest distance to be equal to or less than the upper limit, the plasma density in the sputtering chamber can be efficiently increased.

  The sputter deposition apparatus may be provided with two or more sputter chambers, and the transparent conductive layer may be formed independently by DC dual target sputtering in each sputter chamber. When forming a transparent conductive layer having a laminated structure of two or more layers, the transparent conductive layer having a laminated structure can be efficiently obtained by changing the conditions of the DC dual target sputtering method in each sputtering chamber according to the properties of each layer. Can be formed.

It is a conceptual diagram which shows the structure of the sputter film deposition apparatus which concerns on one Embodiment of this invention. It is typical sectional drawing of the transparent conductive film which concerns on one Embodiment of this invention. It is a conceptual diagram which shows the structure of the sputter film deposition apparatus which concerns on another embodiment of this invention. It is typical sectional drawing of the transparent conductive film which concerns on another embodiment of this invention.

  Embodiments of the method for producing a transparent conductive film of the present invention will be described below with reference to the drawings. However, in some or all of the drawings, parts unnecessary for the description are omitted, and there are parts shown enlarged or reduced for easy explanation. The terms indicating the positional relationship such as up and down are merely used for ease of explanation, and are not intended to limit the configuration of the present invention.

<< First Embodiment >>
Hereinafter, a first embodiment which is an embodiment of the present invention will be described. First, after explaining the manufacturing method of a transparent conductive film, the transparent conductive film which is a result is demonstrated.

[Method for producing transparent conductive film]
FIG. 1 is a conceptual diagram showing a configuration of a sputter deposition apparatus according to an embodiment of the present invention. In the sputter deposition apparatus 100, the roll film to which the base film 1 is fed from the feed roll 53, is conveyed by the temperature control roll 52 through the guide roll 55, and is taken up by the take-up roll 54 through the guide roll 56.・ The roll method is adopted. The inside of the sputter deposition apparatus 100 is evacuated to a predetermined pressure or less (exhaust means is not shown). The temperature adjustment roll 52 is controlled to reach a predetermined temperature.

  The sputter deposition apparatus 100 of this embodiment includes one sputter chamber 11. The sputter chamber 11 is a region surrounded by the casing 101 of the sputter deposition apparatus 100, the partition wall 12, and the temperature control roll 52, and can be set to an independent sputter atmosphere during sputter deposition. The sputtering chamber 11 includes two indium-tin composite oxide (ITO) targets 13A and 13B. The ITO targets 13 </ b> A and 13 </ b> B are each connected to a DC power source 16, and are discharged from the DC power source, so that a transparent conductive layer is formed on the base film 1. In the sputtering chamber 11, plasma control of the DC power source 16 is performed, and argon gas and oxygen gas are introduced into the sputtering chamber 11 at a predetermined volume ratio (for example, argon gas: oxygen gas = 98: 2). Thus, in the sputter deposition apparatus 100, since the sputtering chamber 11 includes two ITO targets, the sputtering rate can be doubled as compared with the single target sputtering method, and the deposition process can be speeded up. The plasma density in the sputtering chamber can be increased, and as a result, a denser sputtered film can be formed and the specific resistance of the obtained transparent conductive layer can be reduced.

  The shape of the ITO targets 13A and 13B may be a flat plate type (planar) as shown in FIG. 1 or a cylindrical type (rotary).

  The shortest distance between the two ITO targets 13A and 13B is preferably 10 mm or more and 150 mm or less, and more preferably 20 mm or more and 140 mm or less. If the shortest distance between the ITO targets is too small, the magnetic fields may interfere with each other when the magnetic field is applied together with the DC power to form a desired film. By adopting the lower limit of the shortest distance, it is possible to prevent such magnetic field interference and form a transparent conductive layer having good film quality. On the other hand, if the shortest distance is too large, the plasma density will not increase sufficiently in the same state as when two single ITO targets are arranged, and two ITO targets are placed in one sputter chamber 11. In some cases, the advantages of provisioning cannot be fully obtained. By setting the shortest distance to a predetermined value or less, the plasma density in the sputtering chamber 11 can be efficiently increased.

As the ITO targets 13A and 13B, a target containing an indium-tin composite oxide (In ₂ O ₃ —SnO ₂ target) is preferably used. When an In ₂ O ₃ —SnO ₂ metal oxide target is used, the amount of SnO ₂ in the metal oxide target is 0.5 weight relative to the weight of In ₂ O ₃ and SnO ₂ added. % To 15% by weight is preferable, 1 to 12% by weight is more preferable, and 2 to 12% by weight is even more preferable. If the amount of SnO _{2 in} the target is too small, the durability of the ITO film may be inferior. If the amount of SnO ₂ is too large, it ITO film is hardly crystallized, there is a case stability transparency and resistance is not sufficient.

In sputter deposition using such an ITO target, the degree of vacuum (degree of ultimate vacuum) in the sputter deposition apparatus 100 is preferably 1 × 10 ⁻³ Pa or less, more preferably 1 × 10 ⁻⁴ Pa or less. It is preferable to evacuate to an atmosphere in which impurities such as moisture in the sputter deposition apparatus 100 and organic gas generated from the base film 1 are removed. This is because the presence of moisture or organic gas terminates dangling bonds generated during sputtering film formation and hinders the crystal growth of a conductive oxide such as ITO.

  Into the sputter chamber 11 evacuated in this manner, an oxygen gas, which is a reactive gas, is introduced as necessary together with an inert gas such as Ar, and sputter deposition is performed under a reduced pressure of 1 Pa or less. The pressure in the sputtering chamber 11 during film formation is preferably 0.05 Pa to 1 Pa, and more preferably 0.1 Pa to 0.7 Pa. If the film formation pressure is too high, the film formation rate tends to decrease. Conversely, if the pressure is too low, the discharge tends to become unstable.

The power density of the DC power source 16 for each ITO target 13A, 13B can be set as appropriate in consideration of the thickness, specific resistance, production efficiency, etc. of the target transparent conductive layer. Power density of DC power source 16 is preferably 0.6 W / cm ² or more 9.0W / cm ² or less, 0.9 W / cm ² or more 8.0 W / cm ² or less being more preferred.

[Transparent conductive film]
A transparent conductive film obtained by the above-described DC dual target sputtering method will be described. As shown in FIG. 2, in the transparent conductive film 10, the transparent conductive layer 2 containing indium-tin composite oxide is formed on the base film 1.

<Base film>
The base film 1 is not particularly limited as long as it is flexible and transparent in the visible light region, and a plastic film having transparency and a polyester resin as a constituent material is used. Polyester resins are preferably used because of their excellent transparency, heat resistance, and mechanical properties. As the polyester resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and the like are particularly suitable. The plastic film is preferably stretched from the viewpoint of strength, and more preferably biaxially stretched. It does not specifically limit as a extending | stretching process, A well-known extending | stretching process is employable.

  The thickness of the base film is preferably in the range of 2 to 200 μm, more preferably in the range of 2 to 130 μm, and still more preferably in the range of 2 to 110 μm. When the thickness of the film is less than 2 μm, the mechanical strength is insufficient, and the operation of continuously forming the transparent conductive layer 2 and the conductive metal layer 3 in a roll shape may be difficult. On the other hand, if the thickness of the film exceeds 200 μm, the scratch resistance of the transparent conductive layer 2 and the dot characteristics when a touch panel is formed may not be achieved.

  The base film is preliminarily subjected to etching treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation and undercoating treatment on the surface, and the transparent conductive layer 2 formed on the film base You may make it improve the adhesiveness of. Moreover, before forming a transparent conductive layer, you may remove and clean the film base-material surface by solvent cleaning, ultrasonic cleaning, etc. as needed.

  Such a base film 1 is provided as a roll of a long film, and the transparent conductive layer 2 is continuously formed thereon to obtain a long transparent conductive film.

<Transparent conductive layer>
The composition of the transparent conductive layer 2 can be the same composition as the ITO targets 13A and 13B described above.

The thickness of the transparent conductive layer is not particularly limited, but the thickness is preferably 10 nm or more in order to obtain a continuous film having good conductivity with a surface resistance of 1 × 10 ³ Ω / □ or less. If the film thickness becomes too thick, the transparency is lowered, and therefore the thickness is preferably 15 to 35 nm, more preferably in the range of 20 to 30 nm. When the thickness of the transparent conductive layer is less than 15 nm, the electrical resistance of the film surface increases and it becomes difficult to form a continuous film. Further, when the thickness of the transparent conductive layer exceeds 35 nm, the transparency may be lowered.

  The transparent conductive layer 2 may be crystalline or amorphous. In the present embodiment, when the ITO film is formed as the transparent conductive layer by the sputtering method, there is a restriction due to the heat resistance of the base film 1, so that the sputtering film formation cannot be performed at a high temperature. For this reason, the ITO immediately after film formation is an amorphous film (some of which may be crystallized). Such an amorphous ITO film has a lower transmittance than a crystalline ITO film, and may cause problems such as a large resistance change after a humidification heat test. From such a viewpoint, after forming an amorphous transparent conductive layer, the transparent conductive layer may be converted into a crystalline film by annealing in the presence of oxygen in the atmosphere. By crystallizing the transparent conductive layer, the transparency is improved, the resistance change after the humidification heat test is small, and the humidification heat reliability is improved.

In the DC dual target sputtering method, since a dense ITO film can be formed, the specific resistance of the transparent conductive layer can be reduced. The transparent conductive layer 2 after crystallization preferably has a low value of 1.2 × 10 ⁻⁴ Ω · cm or more and 6.0 × 10 ⁻⁴ Ω · cm or less as a specific resistance value. The specific resistance value is more preferably 1.2 × 10 ⁻⁴ Ω · cm or more and 4.0 × 10 ⁻⁴ Ω · cm or less, and further 1.2 × 10 ⁻⁴ Ω · cm or more and 3. It is preferably 5 × 10 ⁻⁴ Ω · cm or less.

  The transparent conductive layer 2 may be patterned by etching or the like. For example, in a transparent conductive film used for a capacitive touch panel or a matrix resistive touch panel, the transparent conductive layer 2 is preferably patterned in a stripe shape. When the transparent conductive layer 2 is patterned by etching, if the transparent conductive layer 2 is first crystallized, patterning by etching may be difficult. Therefore, it is preferable to perform the annealing treatment of the transparent conductive layer 2 after patterning the transparent conductive layer 3.

<Undercoat layer>
Moreover, undercoat layers, such as a dielectric material layer and a hard-coat layer, may be formed between the base film 1 and the transparent conductive layer 2. Among these, the dielectric layer formed on the surface of the base film 1 on the surface side where the transparent conductive layer is formed does not have a function as a conductive layer, and the surface resistance is, for example, 1 × 10 ⁶ Ω / □ or more. It is preferably 1 × 10 ⁷ Ω / □ or more, more preferably 1 × 10 ⁸ Ω / □ or more. There is no particular upper limit on the surface resistance of the dielectric layer. Generally, the upper limit of the surface resistance of the dielectric layer is about 1 × 10 ¹³ Ω / □, which is a measurement limit, but may exceed 1 × 10 ¹³ Ω / □.

As a material of the dielectric layer, NaF (1.3), Na ₃ AlF ₆ (1.35), LiF (1.36), MgF ₂ (1.38), CaF ₂ (1.4), BaF ₂ (1.3), BaF ₂ (1.3), SiO ₂ (1.46), LaF ₃ (1.55), CeF (1.63), Al ₂ O ₃ (1.63) and other inorganic substances [ The numerical value in parentheses indicates the refractive index], or an organic material such as acrylic resin, urethane resin, melamine resin, alkyd resin, siloxane polymer, organosilane condensate having a refractive index of about 1.4 to 1.6, or the above A mixture of an inorganic substance and the organic substance can be given.

  Thus, by forming a dielectric layer on the transparent conductive layer forming surface side of the base film, for example, even when the transparent conductive layer 2 is patterned into a plurality of transparent electrodes, the transparent conductive layer forming region and the transparent film are transparent. It is possible to reduce the difference in visibility between the conductive layer non-formation region. Moreover, when using a film base material as a transparent base material, a dielectric material layer can act also as a sealing layer which suppresses precipitation of low molecular weight components, such as an oligomer from a plastic film.

  A hard coat layer, an easy adhesion layer, an antiblocking layer, and the like may be provided on the surface of the base film 1 opposite to the surface on which the transparent conductive layer 2 is formed, as necessary. In addition, those with other substrates bonded using appropriate adhesive means such as pressure-sensitive adhesives, or those in which a protective layer such as a separator is temporarily attached to a pressure-sensitive adhesive layer for bonding with other substrates It may be.

<< Second Embodiment >>
In the first embodiment, the sputter deposition apparatus 100 includes one sputter chamber 11, but the number of sputter chambers in the sputter deposition apparatus is not limited to one, and may be two or three or more. . What is necessary is just to change the number of the sputtering chambers to operate according to the layer structure of a transparent conductive layer. That is, when the transparent conductive layer is made of a single layer of ITO film, the number of sputtering chambers is one. From this point onward, in the case of two layers of ITO film, two sputtering chambers are used. Three chambers may be provided. In the present embodiment, an aspect in which three sputtering chambers are provided will be described.

  FIG. 3 is a conceptual diagram showing a configuration of a sputter deposition apparatus according to another embodiment of the present invention. The basic configuration of the sputter deposition apparatus 110 is the same as that of the sputter deposition apparatus 100 in the first embodiment. In addition to the sputter chamber 11, a sputter chamber 21 is provided on the upstream side of the sputter chamber 11. A sputtering chamber 31 is provided on the downstream side. Therefore, the sputter deposition apparatus 110 has a total of three sputter chambers. Like the sputtering chamber 11, the sputtering chambers 21 and 31 are provided with ITO targets 23A and 23B and ITO targets 33A and 33B, respectively, and DC power sources 26 and 36 are connected to the targets. Thus, the DC dual target sputtering method can be performed under independent conditions in each sputtering chamber.

  Since the base film 1 is sequentially conveyed from the feed roll 53 through the temperature control roll 52 to the take-up roll 54, when performing sputter film formation in each sputtering chamber, the sputter chamber 21 starts from the base film 1. The first ITO film is formed, and then the second ITO film is formed in the sputtering chamber 11 and the third ITO film is formed in the sputtering chamber 31. The conditions of each sputtering chamber may be the same or different. The sputtering conditions in each sputtering chamber may be set in consideration of the thickness, specific resistance, optical characteristics, etching properties, etc. of the transparent conductive layer 2 to be formed.

  Specifically, an example in which a transparent conductive layer having a three-layer structure is formed using the sputter deposition apparatus 110 will be described below. FIG. 4 is a schematic cross-sectional view of a transparent conductive film according to another embodiment of the present invention. The transparent conductive film 10 ′ includes transparent conductive layers 2 a, 2 b, and 2 c in order on the base film 1. Each transparent conductive layer has a different composition of indium-tin composite oxide, and the weight ratio of tin oxide to the total weight of indium oxide and tin oxide is 0.5% by weight to 5.0% by weight in the transparent conductive layer 2a. The transparent conductive layer 2b has a content of 5.0 wt% to 15.0 wt%, and the transparent conductive layer 2 c has a content of 0.5 wt% to 5.0 wt%. In order to form each of such transparent conductive layers, the composition of the ITO targets 23A and 23B attached to the sputter chamber 21 is 0.5% by weight to 5.0% by weight, and the ITO target 13A attached to the sputter chamber 11 is formed. The composition of 13B may be 5.0 wt% to 15.0 wt%, and the composition of the ITO targets 33 </ b> A and 33 </ b> B mounted in the sputtering chamber 31 may be 0.5 wt% to 15.0 wt%.

<< Other embodiments >>
In the sputter deposition apparatus, a sputter deposition may be performed while a magnet electrode (not shown) is installed together with a DC power source and a magnetic field is applied. The magnetic field to be applied may be set in consideration of the film forming speed and the like, for example, 20 to 150 mT, and preferably 30 to 140 mT.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to a following example, unless the summary is exceeded. In the examples, unless otherwise indicated, “parts” means “parts by weight”.

[Example 1]
On a polyethylene terephthalate having a thickness of 50 μm, a layer made of a thermosetting resin having a weight ratio of 2: 2: 1, which is a condensate of melamine resin: alkyd resin: organosilane, is formed as an undercoat layer to a thickness of 35 nm. Formed. Two sintered bodies of indium oxide 90% by weight-tin oxide 10% by weight are prepared as targets 13A and 13B, and the targets 13A and 13B are placed in one sputter chamber 11 of the sputter deposition apparatus 100 as shown in FIG. Two DC power supplies 16 were connected to each. Next, while reducing the pressure inside the sputter deposition apparatus 100 by vacuum evacuation to 1 × 10 ⁻⁴ Pa, the base film 1 was sufficiently degassed. Using the sputtering film forming apparatus 100 set in this manner, the target 13A and 13B have a DC dual target sputtering method in which the power density is 2.1 W / cm ^2, and argon gas is 98 vol% on the undercoat layer. A transparent conductive layer made of an indium-tin composite oxide with an amorphous thickness of 25 nm was formed in a 0.4 Pa sputtering chamber atmosphere composed of 2% by volume of oxygen gas. Then, the transparent conductive layer was crystallized by performing an annealing treatment at 150 ° C. for 1 hour in an air atmosphere to produce a transparent conductive film.

[Comparative Example 1]
A transparent conductive film was produced in the same manner as in Example 1 except that one ITO target was mounted in the sputter chamber 11 in the sputter deposition apparatus 100 shown in FIG.

[Comparative Example 2]
A transparent conductive film was produced in the same manner as in Example 1 except that an MF-AC power source (40 kHz) was connected to the ITO target instead of the DC power source.

<Evaluation>
(Measurement of resistivity value)
Using the four-terminal method, the surface resistance (Ω / □) of the transparent conductive layer of each transparent conductive film was measured. Next, the film thickness of the transparent conductive layer was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Corporation), and the specific resistance was calculated from the measured surface resistance and film thickness. The results are shown in Table 1.

  Table 1 also shows the sputtering rate. This is the relative ratio of Example 1 and Comparative Example 2 when the sputtering rate of Comparative Example 1 employing the conventional DC single target sputtering method is 100%.

(Results and discussion)
In Example 1, the specific resistance of the transparent conductive layer after crystallization was reduced by about 14% compared to Comparative Example 1 by the conventional sputtering method. This is considered to be caused by the fact that the plasma density is increased by adopting the DC dual target sputtering method and a dense ITO film is formed. In addition, since the DC power source is connected to each of the two ITO targets, the sputtering rate can be doubled as compared with Comparative Example 1, and the speed of ITO film formation can be increased. In Comparative Example 2, although two targets were used, plasma discharge was alternately performed by the MF-AC power source, and on the contrary, both the sputtering rate and the specific resistance were inferior.

DESCRIPTION OF SYMBOLS 1 Base film 2, 2a, 2b, 2c Transparent conductive layer 10, 10 'Transparent conductive film 11, 21, 31 Sputtering chamber 13A, 13B, 23A, 23B, 33A, 33C Target 16, 26, 36 DC power supply 100, 110 Sputter deposition system

Claims (3)

A method for producing a transparent conductive film comprising a step of forming a transparent conductive layer from a target containing an indium-tin composite oxide on a base film by a sputtering method,
The sputtering method is a method for producing a transparent conductive film, which is a DC dual target sputtering method in which a DC power source is connected to each of two targets provided per sputtering chamber in a sputtering film forming apparatus.   The method for producing a transparent conductive film according to claim 1, wherein the shortest distance between the two targets is 10 mm or more and 150 mm or less. The sputter deposition apparatus is provided with two or more sputter chambers,
The manufacturing method of the transparent conductive film of Claim 1 or 2 which forms the said transparent conductive layer by DC dual target sputtering method independently in each sputtering chamber.

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