Flexible substrate with conductive layer and capacitive sensor

Abstract

To provide a flexible substrate with a conductive layer containing silver-based conductive particles that have good adhesion to the flexible substrate, and a capacitive sensor equipped with the same.SOLUTION: A flexible substrate with a conductive layer (10) includes a flexible substrate (1), a first conductive layer (2) formed in an arbitrary arrangement on the surface of the flexible substrate, and a second conductive layer (3) formed in an arbitrary arrangement on the surface of the flexible substrate, and the first conductive layer is formed of a cured product of a silver nanoparticle ink composition, and the second conductive layer is formed of a cured product of a silver compound ink composition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flexible substrate with a conductive layer and a capacitance sensor.

Background Art

[0002] Conventionally, a capacitance-type touch sensor (capacitance sensor) in which a plurality of electrodes are provided on a dielectric layer has been developed. In Patent Document 1, a plurality of electrodes are formed in the XY directions of a dielectric layer, a capacitor is formed between these electrodes and a conductor such as a finger approaching them, and which of the plurality of electrodes the conductor has approached is detected as a change in capacitance. A capacitance sensor is disclosed. The plurality of electrodes and the conductive wiring connected to them are formed by a conductive layer formed in a desired pattern on the surface of the dielectric layer, and the electrodes for detecting the X direction and the electrodes for detecting the Y direction are separated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The capacitance sensor may be required to have flexibility according to the movement or deformation of the installation location. When providing conductive wiring on a flexible substrate, the conductive wiring formed by coating a conductive paste containing carbon-based conductive particles has a problem that it is difficult to perform plating.

[0005] The present invention provides a flexible substrate with a conductive layer containing silver-based conductive particles having good adhesion to the flexible substrate, and a capacitance sensor provided with the same.

Means for Solving the Problems

[0006] [1] A flexible substrate with a conductive layer, comprising a flexible substrate, a first conductive layer formed in any arrangement on the surface of the flexible substrate, and a second conductive layer formed in any arrangement on the surface of the flexible substrate, wherein the first conductive layer is formed of a cured product of the silver nanoparticle ink composition described below, and the second conductive layer is formed of a cured product of the silver compound ink composition described below. <Silver nanoparticle ink composition> The silver nanoparticle ink composition is a paint comprising silver nanoparticles and a solvent, wherein the surface of the silver nanoparticles is coated with an amine. <Silver compound ink composition> Silver compound ink composition is a paint containing a silver compound, an amine, and a solvent. [2] A flexible substrate with a conductive layer according to [1], wherein a plating layer is provided on at least a portion of the surface of the first conductive layer. [3] A flexible substrate with a conductive layer according to [2], wherein any electronic component is connected to the surface of the plated layer via solder. [4] A flexible substrate with a conductive layer according to any one of [1] to [3], wherein the second conductive layer forms a conductive pattern constituting a capacitance sensor and a conductive line extending from the conductive pattern and constituting a lead wire. [5] A capacitive sensor comprising a flexible substrate with a conductive layer as described in any one of items [1] to [4]. [Effects of the Invention]

[0007] In the flexible substrate of the present invention, conductive wiring is formed by a conductive layer containing silver-based conductive particles, resulting in good adhesion of the conductive layer to the flexible substrate and enabling the conductive wiring to follow the movement of the flexible substrate. Capacitive sensors equipped with such excellent conductivity offer improved reliability and sensor sensitivity. Furthermore, because the conductive layer contains silver-based conductive particles, plating is easily performed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a capacitance sensor 10, which is an example of the present invention. [Figure 2] This is a perspective view showing a portion of the first conductive layer 2 that constitutes the component mounting area 11 in the capacitance sensor 10. [Figure 3] This is a perspective view showing how an electronic component 30 is mounted on a plating layer 4 provided on the surface of a first conductive layer 2 that constitutes a component mounting area 11, with a solder layer 5 in between. [Modes for carrying out the invention]

[0009] Capacitive Sensor A first aspect of the present invention is a capacitance sensor equipped with a flexible substrate. In the capacitance sensor of the present invention, the configuration can be the same as that of a known capacitance sensor, except that it has a flexible substrate, a first conductive layer and a second conductive layer, as described below.

[0010] An example of a capacitance sensor according to this embodiment is shown in Figure 1. In the capacitance sensor 10, at least two types of conductive layers, a first conductive layer 2 and a second conductive layer 3, are formed on at least one surface of a flexible substrate 1 made of a flexible and pliable base material such as a resin film. Each conductive layer constitutes any conductive pattern (e.g., conductive wiring, electrodes, capacitors, etc.) necessary to constitute the capacitance sensor.

[0011] The material of the flexible substrate 1 is not particularly limited, and any known material for a flexible substrate can be used, although a resin film is generally preferred. Glass and metal films with a passivated (insulated) surface can also be used. The thickness of the flexible substrate 1 is set appropriately depending on the application, but from the viewpoint of obtaining flexibility and pliability while maintaining structural strength, a thickness of about 0.01 mm to 2.0 mm is preferred.

[0012] In this example, a case is illustrated in which a first conductive layer 2 and a second conductive layer 3 are formed on one surface of the flexible substrate 1. However, this embodiment also includes a case in which only the first conductive layer 2 is formed on one surface of the flexible substrate 1 and only the second conductive layer 3 is formed on the other surface.

[0013] The first conductive layer 2 of the capacitive sensor 10 is formed from a silver nanoparticle ink composition, as described later, and constitutes a conductive pattern in the component mounting area 11 where relative flexibility is not required. On the other hand, the second conductive layer 3 is formed from a silver compound ink composition, as described later, and constitutes a conductive pattern in the touch sensor area 12 and the flexible wiring area 13 where relative flexibility is required.

[0014] Flexible substrate with conductive layer A second aspect of the present invention is a flexible substrate with conductive layers, comprising a flexible substrate, a first conductive layer formed in any arrangement on the surface of the flexible substrate, and a second conductive layer formed in any arrangement on the surface of the flexible substrate. The first conductive layer has an arbitrary conductive pattern and is formed from a cured product of the silver nanoparticle ink composition described below. The second conductive layer has an arbitrary conductive pattern and is formed from a cured product of the following silver compound ink composition. In this embodiment, it is preferable that the first conductive layer and the second conductive layer are formed independently on the same plane of the flexible substrate.

[0015] One example of this embodiment may be the capacitance sensor 10 shown in Figure 1. A portion of the first conductive layer 2 constituting the component mounting area 10 is cut out and shown in Figure 2. Three conductive wires are arranged in parallel on one surface of the flexible substrate 1. Each first conductive layer 2, which is placed in close contact with the surface of the flexible substrate 1, is formed from a cured product of a silver nanoparticle ink composition.

[0016] Furthermore, a plating layer 4 is formed on the surface of each first conductive layer 2. In other words, the plating layer 4 covers at least a part of the surface of each first conductive layer 2. The metal constituting the plating layer 4 is not particularly limited, and for example, known plating-forming metals such as gold, silver, copper, nickel, etc. can be applied. The plating layer 4 may be a single layer or a plurality of layers. The thickness of the plating layer 4 can be, for example, 0.1 to 3 μm.

[0017] The thickness of the first conductive layer 2 in this embodiment is not particularly limited and can be, for example, 0.5 to 10 μm. When the thickness is within this range, the adhesion of the first conductive layer 2 to the flexible substrate 1 is enhanced. In addition, in order to make the thickness within this range, it is preferable that the first conductive layer 2 does not contain carbon particles. Usually, carbon particles are often 1 μm or more in size, and when such large-diameter carbon particles are included, it becomes difficult to form the first conductive layer 2 with a thickness within the above range. Note that the thickness of each conductive layer in this embodiment is a value obtained by cutting out a cross-section in the thickness direction, observing the cross-section of each conductive layer with an electron microscope, measuring the thickness at any five locations, and averaging them.

[0018] When the first conductive layer 2 in this embodiment forms a conductive wiring, the width of the conductive wiring is not particularly limited and can be, for example, 10 μm to 500 μm. Note that the width of each conductive layer in this embodiment is a value obtained by observing the width of each conductive layer with an electron microscope, measuring the width at any five locations, and averaging them.

[0019] The second conductive layer 3 constituting the touch sensor portion 12 and the flexible wiring portion 13 is not shown enlarged as in FIG. 2, but can be in a form in which a plurality of conductive wirings are arranged in parallel on one surface of the flexible substrate 1 as in FIG. 2. Each second conductive layer 3 disposed in close contact with the surface of the flexible substrate 1 is formed of a cured product of a silver compound ink composition. Since it is not assumed to mount other electronic components on the surface of the second conductive layer 3, it is not necessary to provide a plating layer on the surface of the second conductive layer 3 in this embodiment. From the viewpoint of improving the flexibility of the conductive wiring formed of the second conductive layer 3, it is preferable that no plating layer is provided on the surface of the second conductive layer 3.

[0020] The thickness of the second conductive layer 3 in this embodiment is not particularly limited and may be, for example, 5.0 to 20 μm. A thickness within this range improves the adhesion of the second conductive layer 3 to the flexible substrate 1. In order to achieve a thickness within this range, it is preferable that the second conductive layer 3 does not contain carbon particles. Typically, carbon particles are often 1 μm or larger, and the inclusion of such large-diameter carbon particles makes it difficult to form the second conductive layer 3 within the above-mentioned thickness range. On the other hand, it is preferable that the second conductive layer 3 contains a binder resin, as this makes it easier for it to follow the bending of the flexible substrate.

[0021] When the second conductive layer 3 in this embodiment forms a conductive wiring, the width of the conductive wiring is not particularly limited, but it may be, for example, 1.0 μm to 500 μm.

[0022] In this embodiment, as shown in Figure 3, by providing a plating layer 4 on the surface of the first conductive layer 2, any electronic component 30 (e.g., a chip capacitor) can be mounted on the component mounting area 11 formed by the first conductive layer 2. When mounting, it is preferable to interpose solder 5 between the electrode terminals of the electronic component 30 and the plating layer 4. Since the plating layer 4 covers the surface of the first conductive layer 2 and structurally strengthens the first conductive layer 2, the electronic component 30 can be mounted.

[0023] <Silver compound ink composition> Silver compound ink composition is a paint containing a silver compound, an amine, and a solvent. The silver compound is preferably silver carboxylate. If the silver compound is not silver carboxylate, it is preferable that it further contains a carboxylic acid or a carboxylate salt. The paint is preferably contained a solvent for dilution. When a silver compound ink composition is printed on the surface of a substrate in a desired pattern, and this is heated, for example, at a temperature below 200°C for 0.5 to 3 hours, at least a portion of the amine volatilizes, silver is generated in the pattern, and a conductive layer containing silver in the desired pattern is formed. Examples of such silver compound ink compositions include known silver compound ink compositions described in Japanese Patent No. 6557317, Japanese Patent No. 6599891, WO2013 / 096664, and others. The silver compound ink composition may contain known binder resins, to the extent that they do not inhibit the formation of silver.

[0024] Examples of silver compound ink compositions include those comprising a silver complex formed by mixing silver carboxylate, at least one solvent for dissolving the silver carboxylate, and a catalyst, wherein the solvent contains an aromatic hydrocarbon and the catalyst contains an amine that decarboxylates the silver carboxylate. Another example of a silver compound ink composition is one comprising a silver complex formed by mixing silver carboxylate, at least one solvent for dissolving the silver carboxylate, and a catalyst for reducing the silver in the silver carboxylate, wherein the solvent contains an aromatic hydrocarbon and the catalyst contains an amine.

[0025] The silver carboxylate is preferably one or more selected from the group consisting of silver propionate, silver butyrate, silver pentanoate, silver hexanoate, silver heptanoate, silver ethylhexanoate, silver behenate, silver oleate, silver octanoate, silver nonanoate, silver decanoate, silver neodecanoate, and silver hexafluoroacetylacetoneate.

[0026] The catalyst is preferably one or more selected from the group consisting of primary amines, secondary amines, tertiary amines, polyamines, and combinations thereof.

[0027] The catalyst is methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, allylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, isopentylamine, 2-ethylhexylamine, Preferably, it is one or more selected from the group consisting of tert-hexylamine, phenylamine, cyclopentylamine, tert-octylamine, tert-decylamine, tert-dodecylamine, tert-octadecylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, diphenylamine, dicyclopentylamine, methylbutylamine, trimethylamine, triethylamine, tripropylamine, triphenylamine, ethylenediamine, 1,3-diaminopropane, and hexamethylenediamine.

[0028] Furthermore, examples of silver compound ink compositions include those containing a silver salt, (a) a complex of a complexing agent and formic acid, or (b) a complex of a complexing agent and a salt of formic acid, and ethylenediamine, wherein the complexing agent is an alkylamine. The alkylamine is preferably one or more selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, and amylamine. The silver salt is preferably one or more selected from the group consisting of silver acetate, silver formate, silver carbonate, silver fluoride, silver nitrate, silver nitrite, silver chloride, silver bromide, silver iodide, silver phosphate, and silver oxide. The silver compound ink composition preferably further contains one or more solvents selected from the group consisting of ethanol, butanol, propylene glycol, and water. The ratio of the alkylamine to the ethylenediamine is preferably 4:1 to 1:4 by volume. The ratio of the alkylamine to the formic acid or the salt of the formic acid is preferably at least 2:1 on a molar basis. By heating the coating film of the silver compound ink composition containing the aforementioned silver salt at, for example, 120°C or below, silver can be generated in the coating film to form a conductive layer.

[0029] <Silver nanoparticle ink composition> The silver nanoparticle ink composition is a paint comprising silver nanoparticles and a solvent, wherein the surface of the silver nanoparticles is coated with an amine. When a silver nanoparticle ink composition is printed on the surface of a substrate in a desired pattern, and this is heated, for example, at 130°C or below for 0.5 to 3 hours, at least a portion of the amine volatilizes, silver is generated in the pattern, and a conductive layer containing silver in the desired pattern is formed. Examples of such silver nanoparticle ink compositions include known silver nanoparticle ink compositions described in WO2017 / 175661, etc. It is preferable that the silver nanoparticle ink composition does not contain a binder resin. By not including a binder resin, it becomes easier to apply a plating process to the surface of the first conductive layer formed by the silver nanoparticle ink composition and to laminate the plated layer.

[0030] Silver nanoparticles are silver particles with a primary particle size (average primary particle diameter) of less than 1000 nm. Here, the particle diameter is the average of the diameters (maximum diameters) of 10 primary particles observed with a scanning electron microscope. In silver nanoparticles whose surface is coated with the protective agent, the average primary particle diameter of the silver nanoparticle portion is, for example, 0.5 to 100 nm, preferably 0.5 to 80 nm, more preferably 1 to 70 nm, and even more preferably 1 to 60 nm.

[0031] The viscosity of the silver nanoparticle ink composition (at 25°C and a shear rate of 10¹ / s) is preferably 60 Pa·s or higher. This viscosity can be measured, for example, using a rheometer (product name "PhysicaMCR301", manufactured by Anton Paar) or a higher-end compatible instrument.

[0032] The amine modifies the surface of the silver nanoparticles. Preferably, the amine includes, for example, an aliphatic monoamine (1) with a total of 6 or more carbon atoms, an aliphatic monoamine (2) with a total of 5 or fewer carbon atoms, and / or an aliphatic diamine (3) with a total of 8 or fewer carbon atoms.

[0033] The aliphatic monoamine (1) may include, for example, primary amines having a linear alkyl group such as hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, and octadecylamine; primary amines having a branched alkyl group such as isohexylamine, 2-ethylhexylamine, and tert-octylamine; and primary amines having a cycloalkyl group such as cyclohexylamine. Examples include primary amines having alkenyl groups such as oleylamine; secondary amines having linear alkyl groups such as N,N-dipropylamine, N,N-dibutylamine, N,N-dipentylamine, N,N-dihexylamine, N,N-dipeptylamine, N,N-dioctylamine, N,N-dinonylamine, N,N-didecylamine, N,N-diundecylamine, N,N-didodecylamine, and N-propyl-N-butylamine; secondary amines having branched alkyl groups such as N,N-diisohexylamine and N,N-di(2-ethylhexyl)amine; tertiary amines having linear alkyl groups such as tributylamine and trihexylamine; and tertiary amines having branched alkyl groups such as triisohexylamine and tri(2-ethylhexyl)amine.

[0034] Examples of the aliphatic monoamine (2) include primary amines with a total of 2 to 5 carbon atoms having linear or branched alkyl groups, such as ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, and tert-pentylamine; and secondary amines with a total of 2 to 5 carbon atoms having linear or branched alkyl groups, such as N,N-dimethylamine, N,N-diethylamine, N-methyl-N-propylamine, and N-ethyl-N-propylamine.

[0035] Examples of the aliphatic diamine (3) include ethylenediamine, 1,3-propanediamine, 2,2-dimethyl-1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,5-diamino-2-methylpentane, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyl-1,3-propanediamine, and N,N'-diethyl-1,3-propanediamine. Examples include pandiamine, N,N'-dimethyl-1,4-butanediamine, N,N'-diethyl-1,4-butanediamine, N,N'-dimethyl-1,6-hexanediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethyl-1,4-butanediamine, N,N-diethyl-1,4-butanediamine, and N,N-dimethyl-1,6-hexanediamine.

[0036] The combined content of aliphatic monoamine (1) and aliphatic monoamine (2) and / or aliphatic diamine (3) is preferably such that, based on the total amount of amines [monoamine (1) + monoamine (2) + diamine (3); 100 mol%], the content of monoamine (1) is 5 to 65 mol%, and the total content of monoamine (2) and diamine (3) is 35 to 95 mol%.

[0037] The solvent preferably contains at least a terpene-based solvent. The content of solvents with a boiling point below 130°C in the total mass of the solvent is preferably 20% by mass or less. The solvent preferably contains one or more selected from ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monopentyl ether, diethylene glycol monoisopentyl ether, diethylene glycol monohexyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and 3-methoxy-1-butanol.

[0038] The silver nanoparticle composition may further contain one or more aliphatic monocarboxylic acids. Examples of aliphatic monocarboxylic acids include saturated aliphatic monocarboxylic acids having 4 or more carbon atoms, such as butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, and eicosanoic acid; and unsaturated aliphatic monocarboxylic acids having 8 or more carbon atoms, such as oleic acid, elaidic acid, linoleic acid, palmitoleic acid, and eicosenoic acid. [Explanation of symbols]

[0039] 1... Flexible substrate, 2... First conductive layer, 3... Second conductive layer, 4... Plating layer, 5... Solder, 10... Capacitive sensor, 11... Component mounting area, 12... Touch sensor area, 13... Flexible wiring area, 30... Electronic component.

Claims

1. Flexible circuit board and A first conductive layer formed in an arbitrary arrangement on the surface of the flexible substrate, A second conductive layer formed in an arbitrary arrangement on the surface of the flexible substrate, A flexible substrate with a conductive layer, The first conductive layer is formed by a cured product of the following silver nanoparticle ink composition, The second conductive layer is formed by a cured product of the following silver compound ink composition. Flexible substrate with a conductive layer. <Silver nanoparticle ink composition> The silver nanoparticle ink composition is a paint comprising silver nanoparticles and a solvent, wherein the surface of the silver nanoparticles is coated with an amine. <Silver compound ink composition> Silver compound ink composition is a paint containing a silver compound, an amine, and a solvent.

2. The conductive layer-equipped flexible substrate according to claim 1, wherein a plating layer is provided on at least a portion of the surface of the first conductive layer.

3. The conductive layer-equipped flexible substrate according to claim 2, wherein any electronic component is connected to the surface of the plating layer via solder.

4. The flexible substrate with a conductive layer according to claim 1 or 2, wherein the second conductive layer forms a conductive pattern constituting a capacitance sensor and a conductive line extending from the conductive pattern and constituting a lead wire.

5. A capacitive sensor comprising a flexible substrate with a conductive layer as described in claim 4.

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