JP2020098701A - Conductive film and method for producing conductive film - Google Patents

Abstract

To provide a conductive film that prevents the occurrence of wrinkles in a resin film when conductive layers are formed on both sides of a resin film by sputtering, and a method of producing the same.SOLUTION: A conductive film comprises a first conductive layer, a resin film, and a second conductive layer in the stated order. When measured along a direction perpendicular to the longitudinal direction of the resin film, a difference between a maximum and a minimum of thermal expansion coefficients of the resin film at 20°C-140°C is 25 ppm/K or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a conductive film and a method for manufacturing a conductive film using the same.

BACKGROUND ART Conventionally, a conductive film having a conductive layer formed on the surface of a resin film has been used for flexible circuit boards, electromagnetic wave shielding films, flat panel displays, touch sensors, non-contact type IC cards, solar cells and the like. The main function of the conductive film is electric conduction, and the composition and thickness of the conductive layer provided on the surface of the polymer film are appropriately selected so as to obtain electric conductivity suitable for the purpose of use.

Wrinkles may occur on the resin film when the conductive layer is formed by the sputtering method. On the other hand, measures have been taken to prevent the generation of wrinkles by applying tension to the resin film (for example, Patent Documents 1 and 2).

JP-A-62-247073 JP, 2009-249688, A

However, even if the above measures are taken, wrinkles may occur when the conductive layers are formed on both sides of the resin film, which is one of the causes for lowering productivity and reliability.

An object of the present invention is to provide a conductive film capable of suppressing the generation of wrinkles in the resin film when the conductive layers are formed on both sides of the resin film by a sputtering method, and a method for producing the conductive film.

The inventors of the present invention have made extensive studies to solve the above problems, and have found that the above object can be achieved by adopting the following constitution, and have completed the present invention.

The present invention provides, in one embodiment,
A conductive film comprising a first conductive layer, a resin film, and a second conductive layer in this order,
The present invention relates to a conductive film in which the difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along the direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less.

In the conductive film, since the variation in the coefficient of thermal expansion in the direction perpendicular to the longitudinal direction of the resin film (hereinafter, also referred to as “width direction”) is small, wrinkles during the formation of the conductive layer by the sputtering method are reduced. Occurrence can be suppressed. The reason for this is not clear, but it is presumed as follows. When the conductive layer is formed by sputtering while transporting the film by the roll-to-roll method, some tensile stress is applied in the transport direction (that is, the longitudinal direction) of the resin film. Thereby, the generation of wrinkles in the longitudinal direction of the resin film is suppressed to some extent. The present inventors have achieved wrinkle suppression at a higher level by paying attention to the occurrence of wrinkles in the width direction as well as in the longitudinal direction of the resin film. As described above, the wrinkle suppression in the longitudinal direction of the resin film can be relatively easily achieved by the tensile stress, but it is difficult to apply the tensile stress in the width direction. In particular, when the sputter film formation is performed while heating from several tens of degrees to several hundreds of degrees, wrinkles in the width direction of the resin film become remarkable. Therefore, the present inventors considered that the thermal expansion or contraction of the resin film in the width direction may be the cause of wrinkles. As a result, by minimizing the variation in the coefficient of thermal expansion that occurs in the width direction of the resin film, the occurrence of wrinkles is suppressed not only in the longitudinal direction but also in the width direction, and the occurrence of wrinkles is suppressed as a whole. This makes it possible to provide high quality conductive films. When the difference between the maximum value and the minimum value of the thermal expansion coefficient exceeds 25 ppm/K, local thermal expansion or thermal contraction in the width direction of the resin film becomes excessive, which may cause wrinkles in the resin film. ..

The first conductive layer and the second conductive layer may each independently have a thickness of 10 nm or more and 300 nm or less. Since the conductive film suppresses the variation in the coefficient of thermal expansion in the width direction of the resin film, it can be widely applied from the formation of a thin conductive layer to the formation of a thick conductive layer.

Both the first conductive layer and the second conductive layer may be sputtered films. It is possible to suppress the generation of wrinkles even if the step of placing a large load on the resin film, that is, sputtering under vacuum heating conditions is repeated on both sides.

In another embodiment, the invention provides
Including a step of preparing a resin film, and a step of sequentially forming conductive layers on both surfaces of the resin film by a sputtering method,
A method for producing a conductive film, wherein the difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along a direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less. Regarding

In the manufacturing method, since the resin film that suppresses the variation in the coefficient of thermal expansion in the width direction is used, it is possible to suppress the occurrence of wrinkles in the resin film even if the conductive layers are formed by sputtering on both surfaces of the resin film. You can

It is a typical sectional view of a conductive film concerning one embodiment of the present invention. It is a schematic diagram which shows the sample manufacturing method for thermal expansion coefficient measurement in the width direction of a resin film.

Embodiments of the 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 description are omitted, and there are parts illustrated in an enlarged or reduced form for ease of description. The terms indicating the positional relationship such as the upper and lower sides are used merely for facilitating the description, and are not intended to limit the configuration of the present invention at all.

<Conductive film>
The conductive film of the present embodiment,
A conductive film comprising a first conductive layer, a resin film, and a second conductive layer in this order,
The difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along the direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less.

<Method for producing conductive film>
The manufacturing method of the conductive film of the present embodiment,
Including a step of preparing a resin film, and a step of sequentially forming conductive layers on both surfaces of the resin film by a sputtering method,
The difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along the direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less.

FIG. 1 is a schematic sectional view of a conductive film according to an embodiment of the present invention. The conductive film 100 shown in FIG. 1 includes a first conductive layer 21, a resin film 1, and a second conductive layer 22 in this order (hereinafter, when the first conductive layer and the second conductive layer are not distinguished from each other). May be simply referred to as "conductive layer".). In this embodiment, base layers 41 and 42 are provided between the resin film 1 and the first conductive layer 21, and between the resin film 1 and the second conductive layer 22, respectively. Although each of the first conductive layer 21, the second conductive layer 22, and the base layer 41 is shown as having a single layer, it may have a multilayer structure of two or more layers. Further, in the present embodiment, the first protective film 31 is arranged on the side of the first conductive layer 21 opposite to the resin film 1, and the second protective film 32 is arranged on the side of the second conductive layer 22 opposite to the resin film 1. It is arranged (hereinafter, when the first protective film and the second protective film are not distinguished from each other, they may be simply referred to as “protective film”).

(Resin film)
The resin film 1 is not particularly limited as long as it can ensure the insulating property, and various plastic films are used. Examples of the material for the resin film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyethylene naphthalate (PEN), polyimide resins such as polyimide (PI), polyethylene (PE), polypropylene (PP). ) Etc. polyolefin resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, cycloolefin resin, (meth)acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene Examples of the resin include polyvinyl resins, polyvinyl alcohol resins, polyarylate resins, and polyphenylene sulfide resins. Among them, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) and polyimide resins such as polyimide (PI) are preferable from the viewpoints of heat resistance, durability, flexibility, production efficiency, cost and the like. preferable. Particularly, polyethylene terephthalate (PET) is preferable from the viewpoint of cost performance.

The surface of the resin film 1 is previously subjected to etching treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation, etc. or an undercoating treatment so as to have good adhesion to the conductive layer formed on the resin film. May be secured. In addition, before forming the conductive layer, the surface of the resin film may be removed and cleaned by solvent cleaning, ultrasonic cleaning, or the like, if necessary.

The thickness of the resin film 1 is preferably in the range of 2 to 300 μm, more preferably in the range of 10 to 250 μm, and even more preferably in the range of 20 to 200 μm. In general, a thicker resin film is desirable because it is less likely to be affected by heat shrinkage during heating. However, it is desirable to reduce the thickness of the resin film to some extent as electronic parts are made more compact. On the other hand, when the thickness of the resin film is too thin, the moisture permeability and the permeability of the resin film increase, and moisture, gas, etc. are transmitted, and the conductive layer is easily oxidized. Therefore, in the present embodiment, the conductive film itself can be thinned by reducing the thickness of the resin film while having a certain thickness, and it is possible to suppress the thickness when used for an electromagnetic wave shielding sheet, a sensor, or the like. Becomes Therefore, it is possible to reduce the thickness of the electromagnetic wave shield sheet and the sensor. Further, when the thickness of the resin film is within the above range, mechanical strength is sufficient while ensuring flexibility of the resin film, and an operation of continuously forming a base layer or a conductive layer by rolling the film. Is possible.

The difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film 1 measured at 20° C. to 140° C. along the direction perpendicular to the longitudinal direction of the resin film 1 is 25 ppm/K or less. The difference between the maximum value and the minimum value of the thermal expansion coefficient is preferably 20 ppm/K or less, more preferably 10 ppm/K or less. By reducing the variation in the coefficient of thermal expansion in the width direction of the resin film 1 as described above, it is possible to efficiently suppress the generation of wrinkles when forming the conductive layer. In order to make the difference between the maximum value and the minimum value of the coefficient of thermal expansion in the width direction of the resin film 1 within the above range, for example, adjustment of the resin film stretching method, use of an unstretched resin film, annealing process of the resin film Can be adopted, and it is preferable to carry out the annealing process of the resin film.

The step of annealing the resin film can be suitably performed using a continuous oven. The continuous oven has one or more chambers, and the temperature of each chamber can be controlled independently. The conditions of the annealing process may be appropriately set according to the total amount of heat applied to the resin film when passing through the oven. For example, the total length of the continuous oven is preferably 10 to 80 m, more preferably 20 to 60 m. The temperature of each chamber of the oven is preferably 50 to 200°C, more preferably 60 to 190°C, though it depends on the material of the resin film used. The line speed at which the resin film is conveyed is preferably 10 to 50 m/min, more preferably 15 to 40 m/min.

(Underlayer)
The conductive film of the present embodiment further includes underlying layers 41 and 42 arranged between the resin film 1 and the first conductive layer 21 and between the resin film 1 and the second conductive layer 22. The underlayer may be formed on one or both of the resin film 1 and the first conductive layer 21 and between the resin film 1 and the second conductive layer 22, or may not be formed. Good. The underlayers 41, 42 can be made highly functional by providing an underlayer according to the purpose such as adhesion of the conductive layer to the resin film, imparting strength to the conductive film, and control of electrical characteristics. Can be planned. The base layer is not particularly limited, and examples thereof include an easy-adhesion layer, a hard coat layer (including those functioning as an anti-blocking layer, etc.), a dielectric layer, and the like.

(Easy adhesion layer)
The easy-adhesion layer is a cured film of the adhesive resin composition. The easy-adhesion layer has good adhesion to the conductive layer.

As the adhesive resin composition, one having sufficient adhesiveness and strength as a cured film after formation of the easy-adhesion layer can be used without particular limitation. Examples of the resin used include thermosetting resin, thermoplastic resin, ultraviolet curable resin, electron beam curable resin, two-component mixed resin, and mixtures thereof. Among these, curing treatment by ultraviolet irradiation is also included. Therefore, an ultraviolet curable resin that can efficiently form an easy-adhesion layer by a simple processing operation is preferable. By containing the ultraviolet curable resin, an adhesive resin composition having ultraviolet curability can be easily obtained.

As the adhesive resin composition, a material that forms a crosslinked structure upon curing is preferable. When the cross-linking structure in the easy-adhesion layer is promoted, the inner structure of the film, which was gradual until then, is strengthened and the film strength is improved. It is presumed that such improvement in film strength contributes to improvement in adhesion.

The adhesive resin composition preferably contains at least one of a (meth)acrylate monomer and a (meth)acrylate oligomer. This facilitates the formation of a crosslinked structure due to the C═C double bond contained in the acryloyl group, and can efficiently improve the film strength. In addition, in this specification, (meth)acrylate means an acrylate or a methacrylate.

The (meth)acrylate monomer and/or acrylate oligomer having a (meth)acryloyl group as a main component used in the present embodiment has a role of forming a coating film, and specifically, trimethylolpropane tri(meth)acrylate. , Ethylene oxide modified trimethylolpropane tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tetra(meth)acrylate, tris(acryloxyethyl) isocyanurate, caprolactone modified tris(acryloxyethyl) ) Isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, alkyl-modified dipentaerythritol tri(meth)acrylate, alkyl Examples thereof include modified dipentaerythritol tetra(meth)acrylate, alkyl modified dipentaerythritol penta(meth)acrylate, caprolactone modified dipentaerythritol hexa(meth)acrylate, and a mixture of two or more thereof.

Among the above-mentioned (meth)acrylates, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, or a mixture thereof is used in terms of abrasion resistance and curability. Especially preferred.

A urethane acrylate oligomer can also be used. The urethane (meth)acrylate oligomer is obtained by reacting a polyol with a polyisocyanate and then reacting with a (meth)acrylate having a hydroxyl group, or after reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group. Examples thereof include, but are not limited to, a method of reacting a polyol, a method of reacting a polyisocyanate, a polyol, and a (meth)acrylate having a hydroxyl group.

Examples of the polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and copolymers thereof, ethylene glycol, propylene glycol, 1,4-butanediol, and 2,2'-thiodiethanol.

Examples of the polyisocyanate include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4′- Examples thereof include diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate.

If the crosslink density is too high, the performance as a primer decreases and the adhesiveness of the conductive layer is likely to decrease, so a low-functional (meth)acrylate having a hydroxyl group (hereinafter referred to as a hydroxyl group-containing (meth)acrylate) may be used. Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. , 4-hydroxybutyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, 2-hydroxy-3-acryloyloxypropyl(meth)acrylate, pentaerythritol tri(meth)acrylate and the like. The above-mentioned (meth)acrylate monomer component and/or (meth)acrylate oligomer component may be used alone or in combination of two or more kinds.

The UV-curable adhesive resin composition of the present embodiment has improved anti-blocking properties by blending a (meth)acrylic group-containing silane coupling agent. Examples of the (meth)acrylic group-containing silane coupling agent include 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, Examples thereof include 3-methacryloxypropyltriethoxysilane, and examples of commercially available products include KR-513 and KBM-5103 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.).

The amount of the silane coupling agent is 0.1 to 50 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the (meth)acrylate monomer and/or (meth)acrylate oligomer. .. Within this range, the adhesiveness with the conductive layer is improved and the physical properties of the coating film can be maintained.

The easy-adhesion layer of the present embodiment may contain nano silica fine particles. As the nano silica fine particles, an organo silica sol synthesized from alkylsilane or nano silica synthesized by plasma arc can be used. Examples of commercially available products include PL-7-PGME (manufactured by Fuso Kagaku, trade name) for the former, and SIRMIBK15WT%-M36 (manufactured by CIK Nanotech, trade name) for the latter. The compounding ratio of the nano silica fine particles is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the total weight of the (meth)acrylate monomer and/or acrylate oligomer having a (meth)acryloyl group and the silane coupling agent, and preferably 5 to 10 parts by weight. More preferably parts by weight. When the content is at least the lower limit, surface irregularities are formed and anti-blocking properties can be imparted, and roll-to-roll production becomes possible. When the content is at most the upper limit, it is possible to prevent the decrease in the adhesion to the conductive layer.

The average particle size of the nano silica fine particles is preferably 100 to 500 nm. If the average particle size is less than 100 nm, the amount of addition necessary to form irregularities on the surface is large, and thus adhesion to the conductive layer cannot be obtained, whereas if it exceeds 500 nm, the irregularities on the surface become large and pinholes are formed. The problem occurs.

The adhesive resin composition preferably contains a photopolymerization initiator in order to impart ultraviolet curability. Examples of the photopolymerization initiator include benzoin ethers such as benzoin normal butyl ether and benzoin isobutyl ether, benzyl ketals such as benzyl dimethyl ketal and benzyl diethyl ketal, and acetophenone such as 2,2-dimethoxyacetophenone and 2,2-diethoxyacetophenone. , 1-hydroxycyclohexyl phenyl ketone, [2-hydroxy-2-methyl-1-(4-ethylenephenyl)propan-1-one], 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-(4-isopropylphenyl)propan-1- Α-hydroxyalkylphenones such as on, 2-methyl-1-[4-(methylthio)phenyl]-1-morpholinopropane, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)- Α-aminoalkylphenones such as 1-butanone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, monoacylphosphine oxides such as 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis(2,6- Examples thereof include monoacylphosphine oxides such as dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

From the viewpoints of curability of the resin, light stability, compatibility with the resin, low volatility, and low odor, an alkylphenone-based photopolymerization initiator is preferable, and 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1 -Phenyl-propan-1-one, (2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 1 -[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is more preferable, and as commercially available products, Irgacure 127, 184, 369, 651, 500, 891, 907. , 2959, Darocure 1173, TPO (manufactured by BASF Japan Ltd., trade name), etc. The photopolymerization initiator is a (meth)acryloyl group-containing (meth)acrylate monomer and/or acrylate oligomer with respect to 100 parts by weight. The solid content is 3 to 10 parts by weight.

At the time of forming the easy-adhesion layer, an adhesive resin composition containing (meth)acrylate and/or (meth)acrylate oligomer having a (meth)acryloyl group in the molecule as a main component is mixed with toluene, butyl acetate, and Prepared as a varnish with a solid content of 30 to 50% by diluting it with a solvent such as butanol, ethyl acetate, cyclohexane, cyclohexanone, methylcyclohexanone, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, diethyl ether, ethylene glycol. To do.

The easy-adhesion layer is formed by applying the varnish on the cycloolefin resin film 1. The method of applying the varnish can be appropriately selected depending on the situation of the varnish and the coating process, and examples thereof include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, and a die coating method. Can be applied by a coating method or an extrusion coating method.

The easy adhesion layer can be formed by curing the coating film after applying the varnish. As the curing treatment of the adhesive resin composition having ultraviolet curability, when the varnish contains a solvent, the solvent is removed by drying (for example, at 80° C. for 1 minute), and then 500 mW/cm ^{2 to} 3000 mW/using an ultraviolet irradiator. in the irradiation intensity of cm ^2, the amount of work steps and the like that are cured with ultraviolet processing 50~400mJ / cm ^2. An ultraviolet lamp is generally used as an ultraviolet ray source, and specifically, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a metal halide lamp and the like can be mentioned. It may be in an inert gas such as nitrogen or argon.

It is preferable to perform heating during the ultraviolet curing treatment. The ultraviolet light irradiation advances the curing reaction of the adhesive resin composition and simultaneously forms a crosslinked structure. By heating at this time, the formation of the crosslinked structure can be sufficiently promoted even with a low ultraviolet ray amount. The heating temperature can be set according to the degree of crosslinking, and is preferably 50°C to 80°C. The heating means is not particularly limited, and a warm air dryer, a radiant heat dryer, heating of a film transport roll, or the like can be appropriately adopted.

The thickness of the easy-adhesion layer is not particularly limited, but is preferably 0.2 μm to 2 μm, more preferably 0.5 μm to 1.5 μm, and further preferably 0.8 μm to 1.2 μm. .. By setting the thickness of the easy-adhesion layer within the above range, the adhesion of the conductive layer and the flexibility of the film can be improved.

(Hard coat layer)
A hard coat layer may be provided as the underlayer. Further, particles may be added to the hard coat layer in order to prevent blocking between the conductive films and enable production by the roll-to-roll method.

For forming the hard coat layer, the same adhesive composition as that for the easy adhesion layer can be preferably used. In order to impart anti-blocking property, it is preferable to add particles to the adhesive composition. As a result, irregularities can be formed on the surface of the hard coat layer, and the anti-blocking property can be suitably imparted to the conductive film 100.

As the above-mentioned particles, those having transparency such as various metal oxides, glass and plastics can be used without particular limitation. For example, silica, alumina, titania, zirconia, inorganic particles such as calcium oxide, polymethylmethacrylate, polystyrene, polyurethane, acrylic resin, acrylic-styrene copolymer, benzoguanamine, melamine, crosslinked or not composed of various polymers such as polycarbonate. Examples include crosslinked organic particles and silicone particles. One kind or two or more kinds of particles can be appropriately selected and used.

The average particle size and blending amount of the above particles can be appropriately set while considering the degree of surface irregularities. The average particle diameter is preferably 0.5 μm to 2.0 μm, and the blending amount is preferably 0.2 to 5.0 parts by weight with respect to 100 parts by weight of the resin solid content of the composition.

(Dielectric layer)
As the underlayer, one or more dielectric layers may be provided. The dielectric layer is formed of an inorganic material, an organic material, or a mixture of an inorganic material and an organic material. Materials for forming the dielectric layer include NaF, Na ₃ AlF ₆ , LiF, MgF ₂ , CaF ₂ , SiO ₂ , LaF ₃ , CeF ₃ , Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , Examples thereof include inorganic substances such as ZnO, ZnS, and SiO _x (x is 1.5 or more and less than 2), and organic substances such as acrylic resin, urethane resin, melamine resin, alkyd resin, and siloxane polymer. In particular, it is preferable to use a thermosetting resin made of a mixture of a melamine resin, an alkyd resin, and an organic silane condensate as the organic material. The dielectric layer can be formed using the above materials by a coating method such as a gravure coating method or a bar coating method, a vacuum vapor deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the dielectric layer is preferably 10 nm to 250 nm, more preferably 20 nm to 200 nm, and further preferably 20 nm to 170 nm. If the thickness of the dielectric layer is too small, it is difficult to form a continuous film. If the thickness of the dielectric layer is excessively large, cracks are likely to occur in the dielectric layer.

The dielectric layer may have nanoparticles having an average particle size of 1 nm to 500 nm. The content of nanoparticles in the dielectric layer is preferably 0.1% by weight to 90% by weight. The average particle size of the nanoparticles used in the dielectric layer is preferably in the range of 1 nm to 500 nm, and more preferably 5 nm to 300 nm, as described above. Further, the content of nanoparticles in the dielectric layer is more preferably 10% by weight to 80% by weight, and further preferably 20% by weight to 70% by weight.

Examples of the inorganic oxide forming the nanoparticles include particles of silicon oxide (silica), hollow nanosilica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, zirconium oxide, niobium oxide and the like. Among these, fine particles of silicon oxide (silica), titanium oxide, aluminum oxide, zinc oxide, tin oxide, zirconium oxide, and niobium oxide are preferable. These may be used alone or in combination of two or more.

(Conductive layer: first conductive layer and second conductive layer)
The first conductive layer 21 provided on one surface side of the resin film 1 and the second conductive layer provided on the other surface have an electric resistivity of 50 μΩcm or less in order to sufficiently obtain an electromagnetic wave shielding effect, a sensor function, and the like. It is preferable to have. The constituent material of the conductive layers 21 and 22 is not particularly limited as long as it satisfies such an electrical resistivity and has conductivity, but for example, Cu, Al, Fe, Cr, Ti, Si, Nb, In. , Zn, Sn, Au, Ag, Co, Cr, Ni, Pb, Pd, Pt, W, Zr, Ta, Hf, Mo, Mn, Mg and V are preferably used. Further, those containing two or more kinds of these metals, and alloys and oxides containing these metals as main components can also be used. Among these conductive compounds, it is preferable to contain Cu and Al from the viewpoints of high conductivity that contributes to electromagnetic wave shielding properties and sensor functions and relatively low price. In particular, from the viewpoint of cost performance and production efficiency, it is preferable that Cu is contained, but elements other than Cu may be contained as much as impurities. As a result, the electrical resistivity is sufficiently small and the electrical conductivity is high, so that the electromagnetic wave shielding property and the sensor function can be improved.

The conductive layers 21 and 22 each independently have a thickness of 10 nm or more and 300 nm or less. The lower limit values of the thicknesses of the conductive layers 21 and 22 are each independently preferably 20 nm, and more preferably 50 nm. On the other hand, the upper limit values of the thicknesses of the conductive layers 21 and 22 are each independently preferably 250 nm, more preferably 220 nm. When the thickness of the conductive layers 21 and 22 exceeds the above upper limit, curling of the conductive film after heating is likely to occur, and it is difficult to reduce the device thickness. If the thickness is smaller than the above lower limit value, the surface resistance value of the conductive film tends to be high under the humidification heat condition and the target humidification heat reliability cannot be obtained, or the strength of the conductive layer is reduced, resulting in a pattern wiring Peeling may occur.

The method for forming the conductive layers 21 and 22 is not particularly limited, and a conventionally known method can be adopted. Specifically, for example, from the viewpoint of film thickness uniformity and film formation efficiency, a vacuum film formation method such as a sputtering method, a chemical vapor deposition method (CVD) or a physical vapor deposition method (PVD), or an ion plating method. The film is preferably formed by a coating method, a plating method (electrolytic plating, electroless plating), a hot stamping method, a coating method, or the like. Further, a plurality of these film forming methods may be combined, and an appropriate method may be adopted depending on the required film thickness. Among them, the sputtering method and the vacuum film forming method are preferable, and the sputtering method is particularly preferable. As a result, continuous production can be performed by the roll-to-roll manufacturing method, production efficiency can be improved, and the film thickness at the time of film formation can be controlled, so that an increase in the surface resistance value of the conductive film can be suppressed. Further, a dense conductive layer which is thin and has a uniform film thickness can be formed.

(Protective layer)
The protective layer may be formed, for example, on the outermost surface side of the conductive layers 21 and 22 in order to prevent the conductive layers 21 and 22 from being naturally oxidized under the influence of oxygen in the atmosphere (not shown). ). The protective layer is not particularly limited as long as it exhibits the rust preventing effect of the conductive layers 21 and 22, but a metal that can be sputtered is preferable, and Ni, Cu, Ti, Si, Zn, Sn, Cr, Fe, indium, gallium, At least one metal selected from the group consisting of antimony, zirconium, magnesium, aluminum, gold, silver, palladium and tungsten, or an oxide thereof is used. Ni, Cu, and Ti are less likely to be corroded because they form a passivation layer, Si is less likely to be corroded due to improved corrosion resistance, and Zn and Cr are metals that are less susceptible to corrosion because they form a dense oxide film on the surface. preferable.

As a material of the protective layer, an alloy composed of two kinds of metals can be used from the viewpoint of ensuring adhesion with the conductive layers 21 and 22 and reliably preventing rust of the conductive layers 21 and 22, but 3 Alloys of one or more metals are preferred. Examples of alloys composed of three or more kinds of metals include Ni-Cu-Ti, Ni-Cu-Fe, and Ni-Cu-Cr. Ni-Cu-Ti is Ni-Cu-Ti from the viewpoint of rust prevention function and production efficiency. preferable. From the viewpoint of ensuring adhesiveness with the conductive layers 21 and 22, an alloy containing a material for forming the conductive layers 21 and 22 is preferable. Accordingly, it is possible to reliably prevent the conductive layers 21 and 22 from being oxidized.

Examples of the material of the protective layer include indium-doped tin oxide (ITO), antimony-containing tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and indium-doped zinc oxide ( IZO) may be included. It is preferable because not only the initial increase in the surface resistance value of the conductive film can be suppressed, but also the increase in the surface resistance value under the humidified heat condition can be suppressed and the stabilization of the surface resistance value can be optimized.

The metal oxide is preferably an oxide such as SiOx (x=1.0 to 2.0), copper oxide, silver oxide, or titanium oxide. It is also possible to provide a rustproof effect by forming a resin layer such as an acrylic resin or an epoxy resin on the conductive layers 21 and 22 instead of the above-mentioned metal, alloy, oxide or the like.

The thickness of the protective layer is preferably 1 to 60 nm, more preferably 2 to 50 nm, and preferably 3 to 40 nm. As a result, durability is improved and oxidation can be prevented from the surface layer, so that the increase in surface resistance value under humidified heat conditions can be suppressed.

(Protective film: first protective film and second protective film)
The surface of the first protective film 31 on the side in contact with the first conductive layer 21 has adhesiveness. Similarly, the surface of the second protective film 32 on the side in contact with the second conductive layer 22 also has adhesiveness. In the present embodiment, the protective film is provided on both sides of the resin film, but is not limited to this, may be provided only on one side of the resin film, the protective film at all It need not be provided.

The material and structure of the protective films 31 and 32 are not particularly limited, but it is desirable to have a base material layer containing a polyolefin resin and an adhesive layer containing a thermoplastic elastomer. As a material for forming the pressure-sensitive adhesive layer, a known pressure-sensitive adhesive such as a removable acrylic pressure-sensitive adhesive can be used.

The polyolefin resin forming the base material layer is not particularly limited, and examples thereof include propylene-based polymers such as polypropylene or block-based or random-based propylene components and ethylene components; low density, high density, linear low density polyethylene and the like. Ethylene-based polymer; olefin-based polymers such as ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, and other olefin-based polymers of ethylene components and other monomers. These polyolefin resins may be used alone or in combination of two or more.

The base material layer contains an olefin resin as a main component, but for the purpose of preventing deterioration, for example, an antioxidant, an ultraviolet absorber, a light stabilizer such as a hindered amine light stabilizer, an antistatic agent, and the like. For example, fillers such as calcium oxide, magnesium oxide, silica, zinc oxide and titanium oxide, additives such as pigments, anti-corrosion agents, lubricants, anti-blocking agents and the like can be appropriately blended.

The thickness of the base material layer is not particularly limited, but is usually about 10 to 300 μm, preferably 15 to 250 μm, and more preferably 20 to 200 μm. Further, the base material layer may be a single layer or may be composed of two or more layers.

The surface of the base material layer opposite to the surface on which the adhesive layer is provided may be subjected to surface treatment, such as corona discharge treatment, flame treatment, plasma treatment, sputter etching treatment, and primer coating for primer, if necessary. You can also

As the thermoplastic elastomer forming the adhesive layer, those used as the base polymer of the adhesive such as styrene elastomer, urethane elastomer, ester elastomer and olefin elastomer can be used without particular limitation. More specifically, styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS), styrene/ethylene-butylene copolymer/styrene (SEBS), styrene/ethylene/propylene copolymer/styrene (SEPS) ) Etc. ABA type block polymers; styrene/butadiene (SB), styrene/isoprene (SI), styrene/ethylene/butylene copolymer (SEB), styrene/ethylene/propylene copolymer (SEP), etc. AB block polymer of styrene; Random styrene copolymer such as styrene/butadiene rubber (SBR); ABC/styrene olefin such as styrene/ethylene/butylene copolymer/olefin crystal (SEBC) Crystalline block polymer; CBC type olefin crystalline block polymer such as olefin crystal/ethylene-butylene copolymer/olefin crystal (CEBC); ethylene-α olefin, ethylene-propylene-α olefin, propylene-α Examples thereof include olefin elastomers such as olefins, and hydrogenated products thereof. These thermoplastic elastomers may be used alone or in combination of two or more.

In forming the adhesive layer, the thermoplastic elastomer may be added to the thermoplastic elastomer, if necessary, for the purpose of controlling adhesive properties, for example, a softening agent, an olefin resin, a silicone polymer, a liquid acrylic copolymer, a phosphoric ester. Compounds, tackifiers, anti-aging agents, hindered amine light stabilizers, UV absorbers, and other additives such as fillers and pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, titanium oxide, etc. It can be blended appropriately.

The thickness of the pressure-sensitive adhesive layer is not particularly limited and may be appropriately determined according to the required adhesion, etc., but is usually about 0.1 to 50 μm, preferably 0.2 to 40 μm, and more preferably It is 0.3 to 20 μm.

The surface of the adhesive layer may be subjected to surface treatment such as corona discharge treatment, ultraviolet ray irradiation treatment, flame treatment, plasma treatment or sputter etching treatment for the purpose of controlling the adhesiveness or the workability of sticking, if necessary. Can also be applied. Further, if necessary, a separator or the like can be temporarily attached and protected on the adhesive layer until it is put into practical use.

Further, a release layer for imparting releasability can be formed on the surface of the base material layer opposite to the surface on which the adhesive layer is attached, if necessary. The release layer may be formed together with the base material layer and the adhesive layer by co-extrusion or may be formed by coating.

When the release layer is formed by co-extrusion, it is preferable to use a mixture of two or more kinds of polyolefin resins. By using a mixture of two or more types of polyolefin-based resins, the compatibility of the two types of polyolefin-based resins can be controlled, so that an appropriate surface roughness can be formed and appropriate release properties can be imparted. is there. When the release layer is formed by coextrusion, its thickness is usually about 1 to 50 μm, preferably 2 to 40 μm, and more preferably 3 to 20 μm.

As the release agent used for forming the release layer by coating, a release agent that can impart releasability can be used without particular limitation. For example, the release agent may be a silicone-based polymer or a long-chain alkyl-based polymer. The release agent may be a solvent-free type, a solvent type dissolved in an organic solvent, or an emulsion type emulsified in water, but the solvent type or emulsion type release agent stably forms the release layer 3 It can be attached to the base material layer 1. Besides, examples of the releasing agent include ultraviolet curable ones. Specific examples of the release agent include Pyroil (manufactured by Yatsusha Oil and Fat Co., Ltd.) and Shin-Etsu Silicone (manufactured by Shin-Etsu Chemical Co., Ltd.).

The thickness of the release layer is not particularly limited, but as described above, it is usually about 1 to 1000 nm, more preferably 5 to 500 nm, and particularly 10 to 100 nm because it has a large contamination reducing effect when formed into a thin film. Is preferred.

(Characteristics of conductive film)
The initial surface resistance value R1 of the conductive film 100 is preferably 0.001 Ω/□ to 10.0 Ω/□, more preferably 0.01 Ω/□ to 7.5 Ω/□, and more preferably 0.1. More preferably, it is 1Ω/□ to 5.0Ω/□. This makes it possible to provide a practical conductive film with excellent production efficiency.

The thickness of the conductive film 100 is preferably in the range of 2 to 300 μm, more preferably in the range of 10 to 250 μm, and even more preferably in the range of 20 to 200 μm. As a result, the conductive film itself can be made thin, and the thickness when used for an electromagnetic wave shielding sheet, a sensor, etc. can be suppressed. Therefore, it is possible to reduce the thickness of the electromagnetic wave shield sheet and the sensor. Furthermore, when the thickness of the conductive film is within the above range, mechanical strength can be sufficient while ensuring flexibility, and the film is rolled to continuously form the Si-containing layer and the conductive layer. The forming operation becomes easy and the production efficiency is improved.

The conductive film may be wound in a roll shape from the viewpoint of transportability and handling. By continuously forming the base layer and the conductive layer on the resin film by the roll-to-roll method, the conductive film can be efficiently manufactured.

(Use of conductive film)
The conductive film can be applied to various uses, and can be applied to, for example, an electromagnetic wave shield sheet, a planar sensor, and the like. The electromagnetic wave shield sheet uses a conductive film and can be suitably used in the form of a touch panel or the like. The thickness of the electromagnetic wave shield sheet is preferably 20 μm to 300 μm.

The shape of the electromagnetic wave shield sheet is not particularly limited, and the shape seen from the stacking direction (the same direction as the thickness direction of the sheet) is rectangular, circular, triangular, or polygonal depending on the shape of the object to be installed. A suitable shape such as a shape can be selected.

The planar sensor uses a conductive film and includes a sensor for sensing various physical quantities in addition to user interface applications such as a touch panel of a mobile device and a controller. The planar sensor preferably has a thickness of 20 μm to 300 μm.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

<Examples 1 and 2 and Comparative Example 1: Preparation of double-sided conductive film>
The long resin film made of the polyethylene terephthalate film (hereinafter, also referred to as PET film) shown in Table 1 was annealed in a continuous oven. The oven was equipped with the first to fifth chambers, and the temperature could be set independently of each other. Table 2 shows the oven conditions and annealing conditions (length [m] and temperature [°C] of each chamber, tension [N] applied to the film, and line speed [m/min]).

Next, the long resin film that had been annealed was wound around a delivery roll and placed in a sputtering apparatus. Thereafter, the inside of the sputtering apparatus was set to a high vacuum of 3.0×10 ⁻³ Torr (0.4 Pa), and in that state, the long resin film was sent out from the roll to the take-up roll to perform sputter film formation. .. In a 3.0×10 ⁻³ Torr atmosphere containing 100% by volume of Ar gas, a Cu target material was used, and a first conductive layer was sputter-deposited on one surface with a thickness of 170 nm by a sintered body DC magnetron sputtering method. Then, by winding the film on a delivery roll, a wound body of a single-sided conductive film having a conductive layer formed on one surface was produced.

By forming a second conductive layer with a thickness of 170 nm on the opposite side of the wound surface of the prepared single-sided conductive film opposite to the surface on which the conductive layer is provided, by sputtering to form a second conductive layer on both sides of the resin film. A wound body of a double-sided conductive film on which a conductive layer was formed was produced.

<Evaluation>
The following evaluations were performed on the resin film used and the conductive film produced. The respective results are shown in Table 1.

(1) Measurement of Thickness The thickness of the conductive layer was measured by observing the cross section of the conductive film using a transmission electron microscope (Hitachi, product name “H-7650”).

(2) Measurement of thermal expansion coefficient in the width direction of the resin film The film was unrolled from the roll of the PET film before forming the conductive layer, and the thermal expansion coefficient was measured along the width direction 5 m from the end of the winding start. Three points were measured. As shown in FIG. 2, the measurement sample is a strip-shaped sample (width direction 5 mm×longitudinal direction 10 mm), which is totaled from one center in the width direction of the resin film and two end portions 50 mm apart from both ends. Three samples were cut out.

Each sample was fixed to a chuck of "TMA/SS7100" manufactured by SII Nano Technology Co., Ltd., and then the thermal expansion coefficient of the sample was measured. The measurement conditions were as follows.
"Measurement condition"
Measurement mode: Tensile method Measurement load: 19.6mN
Distance between chucks: 10 mm
Temperature rising rate: 10°C/min
Temperature program: 10℃→210℃
Measurement atmosphere: N ₂ (flow rate 200 mL/min)

From the obtained results, the average coefficient of thermal expansion [ppm/K] at 20° C. to 140° C. of each sample was read. The maximum value and the minimum value were obtained from the average thermal expansion coefficient of the three samples, and the difference between them was calculated to be used as an index of the variation in the thermal expansion coefficient in the width direction of the resin film.

(3) Wrinkle Evaluation The produced conductive film was evaluated for wrinkles. As an evaluation method, about 10 m was drawn from the obtained wound body of the double-sided conductive film, the conductive film was irradiated with a fluorescent lamp, and the presence or absence of wrinkles was visually evaluated according to the following evaluation criteria.
<<Evaluation criteria>>
◯: No wrinkles were observed.
Δ: Slight wrinkles were observed.
X: Many wrinkles were observed.

(result)
From Table 1, in the conductive films of Examples 1 and 2, the variation in the coefficient of thermal expansion in the width direction of the resin film was reduced, and the occurrence of wrinkles during the formation of the conductive layer was suppressed. On the other hand, in Comparative Example 1, the coefficient of thermal expansion varied in the width direction of the resin film, and wrinkles occurred during the formation of the conductive layer.

1 Resin Film 21 1st Conductive Layer 22 2nd Conductive Layer 31 1st Protective Film 32 2nd Protective Film 41, 42 Underlayer 100 Conductive Film

Claims (4)

A conductive film comprising a first conductive layer, a resin film, and a second conductive layer in this order,
A conductive film in which the difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along the direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less. The conductive film according to claim 1, wherein the first conductive layer and the second conductive layer each independently have a thickness of 10 nm or more and 300 nm or less. The conductive film according to claim 1, wherein the first conductive layer and the second conductive layer are both sputtered films. Including a step of preparing a resin film, and a step of sequentially forming conductive layers on both surfaces of the resin film by a sputtering method,
A method for producing a conductive film, wherein the difference between the maximum value and the minimum value of the thermal expansion coefficient of the resin film at 20° C. to 140° C. measured along the direction perpendicular to the longitudinal direction of the resin film is 25 ppm/K or less. ..

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