JP2016212986A - Flexible conductive film and manufacturing method of flexible conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible conductive film excellent in adhesiveness of a conductive layer and a substrate and conductivity.SOLUTION: A flexible conductive film 10 has a substrate 20 and a conductive layer 30. The substrate 20 is a film-like member having light permeability, has elongation during cutting in at least one direction in a main surface of 150% or more and elongation recovery percentage when relaxed after elongating to a status with elongation of 150% of 50% or more. The conductive layer 30 is formed on one main surface of the substrate 20. The conductive layer 30 has a conductive path in any surface direction of the substrate 20 because it has a network structure formed by a nanowire 32 having conductivity. The substrate 20 fuses to at least a part of nanowire 32. Sheet resistance after 10 cycles for relaxation after elongation with 150% based on that before elongation at speed of 0.5 mm/min. is 5 or less, when the sheet resistance before initiation of an elongation test is 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive film that retains conductivity even when stretched.

  In recent years, wearable devices that are supposed to be worn on the body are attracting attention, and research on forming a transparent conductive film on a substrate having elasticity and flexibility is underway.

For example, Non-Patent Document 1 discloses that after a conductive layer is made of copper nanowires on a glass substrate at 300 ° C. in a reducing gas (5% H ₂ + 95% N ₂ ) atmosphere, a flexible film is placed on the conductive layer. Describes a technique in which the glass substrate is removed by synthesis and the conductive layer is transferred to the film.

J. et al. Mater. Chem. C, 2014, 2, 1298

  In the prior art, when the base material is stretched, there are problems relating to conductivity such that the resistance increases or the resistance varies. In addition, the adhesion between the base material and the conductive layer is insufficient, and the metal nanowire is damaged by the heating process when producing the conductive layer using the metal nanowire, leaving problems in reliability. ing.

  This invention is made | formed in view of such a subject, The objective is adhesion | attachment of a conductive layer and a base material in the elastic | stretch conductive film which has a base material which has a stretching property, and the conductive layer provided on the base material. It is in the provision of the technique which can make a maintenance of electroconductivity and electroconductivity compatible.

  One embodiment of the present invention is a stretchable conductive film. The stretchable conductive film has an elongation recovery rate of 50% or more when cut in at least one direction in the main surface and when the stretch is stretched to 150% and then relaxed. % Of a film-like substrate, and a conductive layer formed on one main surface of the substrate and having a network structure formed of conductive nanowires, and at least a part of the nanowires The sheet resistance is 10% before the start of the expansion / contraction test, after the base material has been fused to 150% at a rate of 0.5 mm / min and stretched to 150% and then relaxed 10 times. When sheet resistance is 1, it is 5 or less.

  In the stretchable conductive film of the above aspect, the substrate may be selected from the group consisting of polyurethane and dimethylpolysiloxane. The nanowire may be formed of one or more metals selected from the group consisting of copper or silver. The total light transmittance of the substrate may be 80% or more.

  Another aspect of the present invention is a method for producing a stretchable conductive film. The method for producing the stretchable conductive film is a film-like base material, wherein the elongation at the time of cutting in at least one direction in the main surface is 150% or more, and the elongation is 150% based on the pre-elongation. A step of applying an ink in which conductive nanowires are dispersed on one main surface of a film-like substrate having an elongation recovery rate of 50% or more after being stretched to a state; Irradiating the metal nanowires with electromagnetic waves, and fusing a substrate to at least a part of the metal nanowires.

  In the method for producing a stretchable conductive film of the above aspect, the base material may be formed of one or more materials selected from the group consisting of polyurethane and dimethylpolysiloxane. The nanowire may be formed of one or more metals selected from the group consisting of copper or silver.

  A combination of the above-described elements as appropriate can also be included in the scope of the invention for which patent protection is sought by this patent application.

  According to the present invention, in a stretchable conductive film having a stretchable base material and a conductive layer provided on the base material, good adhesion between the conductive layer and the base material and conductivity even when the stretch is repeated Holding can be made compatible.

It is a perspective view which shows the outline of the stretchable conductive film which concerns on embodiment. It is process sectional drawing which shows the manufacturing method of the stretchable conductive film which concerns on embodiment. It is a figure for demonstrating the definition of pulsed light. 4A and 4B are SEM images showing the state of the conductive layer before and after light irradiation in Example 1, respectively. 10 is a SEM image showing a state of a conductive layer after heat treatment of Comparative Example 2. It is a figure which shows schematic structure at the time of the electroconductivity evaluation of an elastic conductive film. It is a figure which shows the resistance at the time of expansion-contraction in the elastic conductive film of Example 1,2. It is a figure which shows the resistance at the time of the expansion / contraction in the elastic conductive film of Example 3. It is a figure which shows the resistance at the time of the expansion / contraction in the elastic conductive film of Example 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  FIG. 1 is a perspective view showing an outline of a stretchable conductive film 10 according to an embodiment. The stretchable conductive film 10 has a base material 20 and a conductive layer 30.

  The base material 20 is in the form of a film, and has an elongation at the time of cutting of 150% or more with respect to before stretching in at least one plane direction. Here, it is preferable to use a film-like base material having a total light transmittance (hereinafter referred to as light transmittance) of 80% or more from one main surface side to the other main surface side. When the film-like base material is colored black or the like, the film-like base material may be damaged by absorbing energy generated by electromagnetic waves described later and generating heat. Further, when the color is white or the like, for example, when the electromagnetic wave is light, a part of the light reflected from the irradiation light enters the light source, which may damage the light source. By using a material having high light transmittance, the above problem is solved, and a stretchable conductive film that can be applied to the field of wearable electronics, medical sensors, and optical applications is obtained. In the present specification, “stretchability” means a stretch recovery rate of 50% after stretching to a predetermined degree, for example, 150% (1.5 times the initial length) before stretching, and then relaxing. % Or more. To explain with an example, the length before stretching is 5 cm, and when stretched to 7 cm, the stretch is 140%. When the stretch is relaxed from this state and returned to 5.5 cm, the stretch recovery rate is 75%. Although the base material 20 should just have the elasticity in a specific surface direction, it is preferable to have a elasticity in arbitrary surface directions. The thickness of the base material 20 is not particularly limited as long as the above light transmittance and stretchability are not impaired, and is typically 10 to 200 μm although it depends on the material used. As the material of the base material 20, the elongation at break defined by JIS K6251 is 150% (1.5 times the initial length) or more, and when it is relaxed after being stretched to a state of 150%. The material is not particularly limited as long as the material has an elongation recovery rate of 50% or more, but polyurethane (PU), dimethylpolysiloxane (PDMS), polybutadiene, nitrile, chloroprene synthetic rubber and natural rubber are suitable. It is good also as a composite material which added additives, such as a filler and a pigment.

  The polyol and polyisocyanate structure constituting the polyurethane is not particularly limited, but a structure having a functional group in the side chain is more preferable in order to enhance the adhesion to the nanowire 32. Specific functional groups include a hydroxyl group, a carboxyl group, an acryloyl group, and a methacryloyl group.

  The conductive layer 30 is formed on one main surface of the substrate 20. The conductive layer 30 has a network structure formed of nanowires 32 having conductivity, and thus has a conductive path in an arbitrary plane direction of the substrate 20. The nanowire 32 has a thin wire shape and can take a hollow structure. The average diameter of the nanowire 32 is preferably 5 to 200 nm, more preferably 5 to 100 nm, and further preferably 5 to 70 nm. The average length of the nanowire 32 is preferably 3 to 200 μm, more preferably 5 to 150 μm, and still more preferably 15 to 100 μm. The average diameter and the average length of the nanowires 32 are arithmetic average values obtained by observing 100 nanowires 32 with an SEM.

  The material of the nanowire 32 is at least one selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, iridium, and aluminum, and / or a metal thereof. An alloy combined with these may be used. Among the materials described above, silver and copper are preferably used in terms of high conductivity.

  When the conductive layer 30 formed on one main surface of the substrate 20 is irradiated with an electromagnetic wave to be described later, the nanowire 32 constituting the conductive layer absorbs energy and generates heat, so that the substrate in the vicinity of the nanowire is melted or softened. The base material 20 is fused to at least a part of the nanowire 32, or at least a part of the nanowire 32 is submerged in the base material, whereby the adhesion between the conductive layer 30 and the base material 20 is ensured.

  The sheet resistance of the stretchable conductive film 10 is preferably 1 to 500Ω / □, and more preferably 1 to 200Ω / □. The light transmittance from one main surface of the stretchable conductive film 10 to the other main surface is preferably 20 to 95%, and more preferably 40 to 95%. More preferably, it is 50 to 95%.

  The sheet of the stretchable conductive film 10 after having been stretched 10 times at a rate of 0.5 mm / min to 150% (1.5 times the initial length) before stretching and then relaxed 10 times. The resistance is 5 or less, preferably 4 or less, more preferably 3 or less, when the sheet resistance before the start of the stretch test is 1. Details of the resistance test during expansion and contraction will be described later.

  The stretchable conductive film 10 described above has the characteristics that it has good light transmissivity and maintains good conductivity even when the film is stretched in the surface direction or the film is curved. Therefore, application to various wearable devices is expected.

(Production method)
Drawing 2 is a process sectional view showing the manufacturing method of the elastic conductive film concerning an embodiment.

  First, as shown in FIG. 2A, a base material 20 having the above-described characteristics and thickness is prepared and placed on a table.

  Subsequently, as illustrated in FIG. 2B, an ink (dispersion liquid) 34 in which the nanowires 32 are dispersed is applied on the main surface of the substrate 20. A method for applying the ink 34 is not particularly limited, but a bar coating method, a spin coating method, a spray coating method, a roll coating method may be used as a process for uniformly forming the ink 34 with a desired thickness on the main surface of the substrate 20. , Die coating method, dip coating method, drop coating method and the like. Examples of the process for patterning the ink 34 with a desired thickness on the main surface of the substrate 20 include screen printing, ink jet printing, letterpress printing, intaglio printing, and gravure printing. A method for producing the ink 34 will be described later.

  The nanowire 32 formed of metal can be manufactured by a known manufacturing method. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinylpyrrolidone using a polyol (Poly-ol) method.

  Subsequently, the ink 34 is dried. The drying conditions vary depending on the printing method, but as an example, in the spray coating method, drying is performed at room temperature in an air atmosphere for 5 to 10 minutes. After the ink 34 is dried, an electromagnetic wave having a predetermined energy is irradiated toward the nanowire 32 as shown in FIG. The manufacturing conditions at this time do not require treatment such as pressurization or heating, and may be in the air or at room temperature.

  When predetermined energy is given to the nanowire 32 by the irradiation of the electromagnetic wave, the temperature of the nanowire 32 rises as the nanowire 32 absorbs the electromagnetic wave as shown in FIG. The nanowires 32 are electrically and physically connected at the intersections, and the entire nanowires 32 have a network structure, and the conductive layer 30 is formed. Moreover, after at least a part of the nanowire 32 sinks into the melted or softened base material 20 due to the heat generated by the nanowire 32 under the irradiation of electromagnetic waves, the base material 20 is solidified so that at least a part of the nanowire 32 is obtained. The base material 20 is fused, and adhesion between the base material 20 and the conductive layer 30 is obtained. Further, since the nanowire 32 is protected by the base material 20, oxidation of the nanowire 32 is suppressed. In order to further suppress oxidation, after the conductive layer 30 is formed, an overcoat may be further performed using a material equivalent to the base material 20 or a raw material thereof.

  The electromagnetic wave to be irradiated is preferably pulsed light. More specifically, using a xenon-type pulse irradiation lamp, pulsed light having a pulse width of 20 to 50 milliseconds, more preferably 50 to 10 milliseconds, is irradiated between the nanowires 32. Intersection points can be joined. Here, the bonding means that at the intersection of the nanowires 32, the material of the nanowires 32 instantaneously absorbs the pulsed light irradiation, and more efficiently generates internal heat at the intersecting portion, so that the portion is welded. is there. By this bonding, the connection area between the nanowires 32 at the intersection can be increased and the surface resistance can be lowered. Thus, by irradiating pulsed light and joining the intersections of the nanowires 32, the conductive layer 30 in which the nanowires 32 are meshed, in other words, a conductive pattern is formed. The network formed by the nanowires 32 preferably has a sufficient gap (aperture ratio) so that a desired light transmittance can be obtained.

  In this specification, “pulsed light” is light in a short period of time of light irradiation (irradiation time) of several microseconds to several tens of milliseconds, and when light irradiation is repeated a plurality of times, as shown in FIG. It means light irradiation having a period (irradiation interval (off)) in which light is not irradiated between the first light irradiation period (on) and the second light irradiation period (on). Although FIG. 3 shows that the light intensity of the pulsed light is constant, the light intensity may change within one light irradiation period (on). Further, the irradiation conditions of each pulsed light (light intensity of the pulsed light, light irradiation period (on)) and irradiation interval (off) may be changed. The pulsed light can be emitted from a light source including a flash lamp such as a xenon flash lamp. Using such a light source, the conductive layer is irradiated with pulsed light. When irradiation is repeated n times, one cycle (on + off) in FIG. 3 is repeated n times. In the case of repeated irradiation, considering the productivity, it is preferable to cool from the substrate side so that the substrate can be cooled to near room temperature when the next pulse light irradiation is performed.

  The pulsed light may be an electromagnetic wave having a wavelength range of 1 pm to 1 m, preferably an electromagnetic wave having a wavelength range of 10 nm to 1000 μm (from far ultraviolet to far infrared), and more preferably 100 nm to 2000 nm. Electromagnetic waves in the wavelength range can be used. Examples of such electromagnetic waves include gamma rays, X-rays, ultraviolet rays, visible rays, infrared rays and the like. In consideration of conversion to thermal energy, if the wavelength is too short, damage to the substrate is not preferable because of its large damage. On the other hand, when the wavelength is too long, it is not preferable because it cannot efficiently absorb and generate heat. Accordingly, the wavelength range is preferably the ultraviolet to infrared range, more preferably the wavelength in the range of 100 to 3000 nm, among the wavelengths described above.

  The irradiation time (on) of the pulsed light is preferably in the range of about 20 microseconds to about 10 milliseconds. If it is shorter than 20 microseconds, sintering does not proceed and the effect of improving the performance of the conductive film is reduced. On the other hand, if the time is longer than 10 milliseconds, the adverse effects due to light degradation and thermal degradation of the substrate become larger. Irradiation with pulsed light is effective even if performed in a single shot, but can also be performed repeatedly as described above. In the case of repeating, considering the productivity, the irradiation interval (off) is preferably in the range of 20 microseconds to 30 seconds, more preferably 2000 microseconds to 5 seconds. If it is shorter than 20 microseconds, it becomes close to continuous light and is irradiated without being allowed to cool after one irradiation, so that the substrate may be heated and the temperature may be increased to deteriorate. Further, if productivity is not taken into consideration, it can be longer than 30 seconds. However, if it is longer than 30 seconds, it is not ineffective at all because it is allowed to cool, but the effect of repeated execution is reduced.

  A microwave can also be used as the electromagnetic wave. Microwaves are electromagnetic waves having a wavelength range of 1 m to 1 mm (frequency is 300 MHz to 300 GHz).

  The microwave irradiation is performed in a state where the surface of the base material on which the conductive layer is formed is maintained substantially parallel to the direction of the electric lines of force (the direction of the electric field). Here, “substantially parallel” refers to a state in which the surface of the substrate and the direction of the electric force lines of the microwave are parallel or maintain an angle of 30 degrees or less with respect to the direction of the electric force lines. The angle within 30 degrees refers to a state in which the normal line standing on the surface of the base material and the direction of the electric force lines form an angle of 60 degrees or more. Thereby, the number of lines of electric force passing through the film (printing pattern or solid pattern) of the conductive pattern forming composition formed on the substrate is limited, and the occurrence of sparks can be suppressed.

(Preparation of ink)
The ink 34 used in the process shown in FIG. 2B is obtained by dispersing the nanowire 32 described above in a predetermined dispersion medium. The said dispersion medium should just be a thing which does not produce malfunctions, such as a base material melt | dissolving mentioned above. Specifically, taking a spray coating method as an example, the dispersion medium is water; aliphatic alcohols such as methanol, ethanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, 1-octanol, 1-dodecanol and the like. Ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,8 -Aliphatic diols such as octanediol; Polyalkylene glycols such as diethylene glycol, dipropylene glycol and triethylene glycol; Aromatic hydrocarbons such as toluene and xylene; Fats such as tri-n-butylamine, dimethyloctylamine and methyldioctylamine A tertiary amine, and the like. Among these, water, ethanol, and isopropanol are preferable in terms of drying properties. The suitable dispersion medium may differ depending on the printing method. For example, when a screen printing method is used, a dispersion medium having a relatively high viscosity, such as diglycerin, 2,2,4-trimethyl-1.3-pentanediol monoisobutyrate, 2,2,4-trimethyl- 1.3-Pentanediol diisobutyrate, terpineol, bornylcyclohexanol, borneol, isobornylcyclohexanol, isoborneol and the like can be used.

  The content of the nanowire 32 in the ink 34 is appropriately adjusted depending on the coating method of the ink 34 and the dispersion medium used in consideration of the dispersibility of the nanowire 32, the pattern forming property of the obtained coating film, the conductivity, and the optical characteristics. . For example, when using isopropanol as a dispersion medium and applying by spray coating, the content of the nanowire 32 with respect to the entire ink 34 is preferably 0.0001 to 10% by mass, more preferably 0.002 to 5% by mass. Preferably, 0.003 to 2 mass% is more preferable, and 0.005 to 1 mass% is particularly preferable. When the content is less than 0.0001% by mass, the content of the nanowire 32 in the ink is too small, and the number of coatings required to develop necessary conductivity increases. When it exceeds 10 mass%, the dispersibility of the nanowire 32 in ink will fall.

  According to the manufacturing method of the stretchable conductive film described above, at least the following effects can be obtained in addition to the effects already described.

  Since the conductive layer 30 is formed by electromagnetic wave irradiation in a relatively mild environment such as the atmosphere and room temperature, the base material 20 is not required to have heat resistance, and damage to the nanowires 32 and the base material 20 is suppressed. be able to. If the conductive layer 30 is formed by pulsed light irradiation, the stretchable conductive film can be easily produced in a short time, and the production cost of the stretchable conductive film can be reduced.

  Examples of the present invention will be described below. However, these examples are merely examples for suitably explaining the present invention, and do not limit the present invention.

(Preparation of copper nanowires)
0.648 g (2.4 mmol) of octadecylamine, 0.007 g (0.04 mmol) of glucose and 0.054 g (0.4 mmol) of copper chloride are dissolved in 30 ml of water and reacted at an oil bath temperature of 120 ° C. for 24 hours. After that, the nanowires generated by the centrifuge were settled and washed sequentially with water, hexane and isopropanol to obtain copper nanowires. When the obtained copper nanowire was observed arbitrarily by 100 SEM (Hitachi High-Tech Co., Ltd. FE-SEM S-5200), the average diameter was 40 nm and the average length was 50 μm.

(Preparation of copper nanowire ink)
40 mg of the obtained copper nanowire was dispersed in 80 ml of isopropanol to obtain an ink having a copper concentration of 0.064% by mass.

Example 1
Based on a PU film having a thickness of 100 μm (Takeda Sangyo Co., Ltd., Tow Grace Film: TG88-I, light transmittance 88.4%, elongation at break ≧ 500%, elongation recovery rate 100% (catalog value)), The ink was spray-coated on the substrate, and then dried at room temperature for 10 minutes. Next, using Pulse Forge 3300 (manufactured by Novacentrix) as a light source, the ink application surface of the base material (PU film) is irradiated with light at room temperature in the air under the following conditions, so A stretchable conductive film of Example 1 that was 70% was produced. The stretchable conductive film of Example 1 having a light transmittance of 70% was prepared by adjusting the amount of copper nanowires deposited on the base material (PU film) by the number of times the nanowire ink was sprayed. The initial resistance value was 66.5Ω / □.
Light irradiation conditions: 500 V, 50 μs once, 600 V, 30 μs once, 750 V, 30 μs once, a total of three times of light irradiation.

  FIG. 4 shows the state (SEM photograph) of the conductive layer before (A) light irradiation and after (B) light irradiation. It can be seen that the conductive layer is embedded in the substrate after the light irradiation.

(Example 2)
A stretchable conductive film of Example 2 was produced in the same manner as in Example 1 except that the light transmittance was changed to 50% depending on the number of times the nanowire 32 was sprayed. The initial resistance value was 16.5Ω / □.

Example 3
Using SYLGARD (registered trademark) 184 SILICON ELASTOMER KIT manufactured by Dow Corning as a base material, the two liquids were mixed at a ratio of 10 (main agent): 1 (curing agent) and applied to a PET substrate at 120 ° C. in the atmosphere. Example 1 except that the ink was spray-coated on a PDMS film (light transmittance 92%, elongation at break 180%, thickness 100 μm) obtained by heating and curing in an intermediate atmosphere for 1 hour. A stretchable conductive film of Example 3 having a light transmittance of 60% was produced in the same procedure. The initial resistance value was 62.7Ω / □.

(Preparation of silver nanowire ink)
Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.049 g), AgNO ₃ (0.052 g) and FeCl ₃ (0.04 mg) were mixed with 2-methyl-1,3-propanediol (12. 5 ml), and reacted by heating at 150 ° C. for 1 hour. The obtained precipitate was isolated by centrifugation, and the precipitate was dried to obtain a target silver nanowire. 30 mg of the obtained silver nanowires (an average diameter of 90 nm and an average length of 40 μm obtained by observing arbitrary 100 silver nanowires with SEM (FE-SEM S-5200 manufactured by Hitachi High-Tech Co., Ltd.)) was dispersed in 12 g of ethanol. An ink having a silver concentration of 0.25% by mass was obtained.

Example 4
A PU film having a thickness of 100 μm (produced by Takeda Sangyo Co., Ltd., Tow Grace Film: TG88-I, light transmittance of 88.4%, elongation ≧ 500% (catalog value)) is used as a base material, and the silver ink is formed on the base material. After spray coating, it was dried at room temperature for 10 minutes. Next, using Pulse Forge 3300 (manufactured by Novacenttrix) as a light source, the sample was irradiated with light at room temperature in the atmosphere under the same conditions as in Example 1, and the light transmittance was 50%. A stretchable conductive film was prepared. The initial resistance value was 10.0Ω / □.

(Comparative Example 1)
(Preparation of copper particles)
Polyvinylpyrrolidone (1.5 g), Cu (NO ₃ ) ₂ (1.5 g), and 1,3-propanediol (125 g) were weighed and dissolved at room temperature, and then reacted at 200 ° C. for 2 hours. . The obtained precipitate was isolated by centrifugation, washed, and dispersed in ethanol to obtain spherical copper particles. The particle diameter of the obtained copper particles was measured by the Otsuka Electronics Co., Ltd. zeta potential / particle size measurement system ELS-Z2 (dynamic / electrophoretic light scattering method), and the median diameter D50 (average particle size) determined by sphere approximation. Was 300 nm.

(Preparation of copper particle ink)
The above copper particles (0.1 g) were dispersed in ethanol (3.92 g) to obtain an ink having a copper concentration of 2.55% by mass.

  A stretchable conductive film of Comparative Example 1 having a light transmittance of 70% was produced in the same manner as in Example 1 except that copper particle ink was used instead of the copper nano ink. The initial resistance value was not measurable.

(Comparative Example 2)
Instead of light irradiation, the same operation as in Example 1 was performed except that heating was performed in the atmosphere at 100 ° C. for 30 minutes using a small high temperature chamber manufactured by Espec Co., and Comparative Example 2 having a light transmittance of 70%. An elastic conductive film was produced. The initial resistance value was about 70000 Ω / □. FIG. 5 shows a state (SEM photograph) of the conductive layer after the heat treatment. Unlike FIG. 4B, the conductive layer remains exposed on the base material, and it can be seen that the base material is not fused to the copper nanowires.

(Elongation and elongation recovery rate evaluation)
Both ends of the base material having a planar size of 2 cm × 4 cm are fixed to a pair of chucks of a small tabletop testing machine (manufactured by Shimadzu Corporation, EZ Test) so that the distance between the chucks is 3 cm so that the base material does not loosen, One chuck is stretched in the longitudinal direction of the sample at a rate of 0.5 mm / min until the distance between chucks is 4.5 cm (150% of the initial length) (confirmed that the elongation at cutting is 150% or more) ), The distance between both ends when one of the chucks was released and relaxed was measured to obtain the elongation recovery rate. Five samples were measured for each of the PU films used in Examples 1, 2, and 4 and the PDMS film used in Example 3, and the average value was calculated. As a result, the extension recovery rate of the PU film was 98%, and the extension recovery rate of the PDMS film was 93%.

(Light transmittance evaluation)
Using the turbidimeter NDH2000 (JIS-K7136) manufactured by Nippon Denshoku Industries Co., Ltd., the PU film (Take Grace Film Co., Ltd., Tow Grace Film: TG88-I) Was measured. As a result, the transmittance | permeability of Examples 1-4 and the comparative example was 50-70%, respectively.

(Base material adhesion evaluation)
An adhesive tape (Scotch Mending Tape 810, 3 cm × 3 cm) manufactured by 3M was applied to the conductive layer forming surface of the stretchable conductive film of each Example and Comparative Example, and then a peeling test was performed. As a result, in Examples 1 to 4, the conductive layer remained on the substrate side, but in Comparative Examples 1 and 2, the conductive layer adhered to the adhesive tape side.

(Resistance evaluation)
About the elastic conductive film of each Example and a comparative example, the resistance at the time of expansion / contraction was evaluated using the small desktop testing machine (Shimadzu Corp. make, EZ Test).

<Extension condition>
In each Example and Comparative Example, the elongation at the maximum elongation was 110% to 160% based on the pre-extension, the elongation and contraction speed was set to 0.5 mm / min, and the cycle was expanded and contracted for 10 cycles, and the resistance per cycle was measured. did.

  The sample shape used for evaluation is shown in FIG. In the resistance measurement, a pair of platinum electrodes having a plane size of 2 cm × 0.5 cm were provided at intervals of 3 cm on the conductive layers at both ends in the longitudinal direction of the substrate having a plane size of 2 cm × 4 cm on which the conductive layer was formed. Went in state. Each platinum electrode part is fixed to a pair of chucks of a small tabletop testing machine so that the distance between chucks is 3 cm so that the base material does not loosen, and one chuck is set to a predetermined extension in the longitudinal direction of the sample. The operation of moving to a corresponding position (for example, the distance between chucks is 4.2 cm when the elongation is 140%) (extending the sample) and then returning to the original position was repeated 10 times. This series of operations was performed with both platinum electrode portions connected to resistance measuring terminals of Keithley 2110 digital multimeter, and the resistance value between the electrodes was measured.

  FIG. 7 shows the resistance at 120% and 140% elongation in the PU stretch conductive film of Example 1, the resistance at 120%, 140% and 150% elongation in the PU stretch conductive film of Example 2, and FIG. 3 shows the resistance at 110%, 120%, 140% and 150% elongation in the PDMS stretchable conductive film, and FIG. 9 shows the resistance at 160% elongation in the stretchable conductive film of Example 4, respectively.

  As shown in FIG. 7, in the PU film, the resistance value at 120% elongation is 1.5 or less, the resistance value at 140% elongation is 4 or less, and even if the elongation is 150%, 5 or less. It turns out that it is.

  As shown in FIG. 8, the PDMS film has a resistance value change of about 1.2 when the elongation is 110%, a resistance value change of about 1.5 when the elongation is 120%, and a resistance value change when the elongation is 140%. Is about 4, and it can be seen that even if the elongation is 150%, it is 5 or less. As shown in FIG. 9, it can be seen that when the silver nanowire ink is used, the resistance value change at an elongation of 160% is 1.5 or less. In Comparative Example 1, conductivity was not obtained with the prepared sample. In Comparative Example 2, although the resistance value change was small, the initial resistance value was 1000 times or more compared to the initial resistance values of Examples 1 to 4.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. Embodiments to which such modifications are added Can also be included in the scope of the present invention.

10 stretchable conductive film, 20 substrate, 30 conductive layer, 32 nanowire, 34 ink

Claims (7)

The film has an elongation at break in at least one direction in the main surface of 150% or more and an elongation recovery rate of 50% or more when relaxed after being stretched to a state where the elongation is 150%. A substrate;
A conductive layer formed on one main surface of the substrate and having a network structure formed of conductive nanowires;
With
The base material is fused to at least a part of the nanowire, and the sheet resistance after 10 cycles of relaxation after stretching to 150% at a rate of 0.5 mm / min. Is 5 or less when the sheet resistance before starting the stretch test is 1, a stretchable conductive film.   The stretchable conductive film according to claim 1, wherein the substrate is made of one or more materials selected from the group consisting of polyurethane and dimethylpolysiloxane.   The stretchable conductive film according to claim 1 or 2, wherein the nanowire is formed of one or more metals selected from the group consisting of copper or silver.   The stretchable conductive film according to any one of claims 1 to 3, wherein the substrate has a total light transmittance of 80% or more. The elongation at the time of cutting in at least one direction in the main surface is 150% or more, and the elongation recovery rate is 50% or more when the elongation is reduced to 150% based on the pre-elongation condition and then relaxed. A step of applying an ink in which nanowires having conductivity are dispersed on one main surface of the film-like substrate,
Irradiating the metal nanowires with electromagnetic waves, and fusing a substrate to at least a part of the metal nanowires;
A method for producing a stretchable conductive film, comprising:   The method for producing a stretchable conductive film according to claim 5, wherein the base material is made of one or more materials selected from the group consisting of polyurethane and dimethylpolysiloxane.   The method for producing a stretchable conductive film according to claim 5 or 6, wherein the nanowire is formed of one or more metals selected from the group consisting of copper or silver.