Conductive ink and method for producing the same, conductive printed matter, conductor and method for producing the same, and electronic device

Abstract

To provide a conductive ink capable of obtaining good conductive stability even when expanded and contracted.SOLUTION: A conductive ink of the present invention includes silver particles and a resin, and is used for printing on a substrate having at least one of flexibility and stretchability, wherein the silver particles are chain-like, and a crystallite size obtained from powder X-ray diffractometry is 25 nm or more and 37 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conductive ink and a method for producing the same, a conductive printed matter, a conductor and a method for producing the same, and an electronic device. [Background technology]

[0002] Conventionally, conductive inks have been known that are made into a paste by kneading conductive particles such as silver particles or carbon particles with a binder resin and a solvent, etc. By printing such conductive ink on a substrate or the like, desired circuits can be created easily and with high precision. Conventional conductive inks, such as those disclosed in Patent Document 1 (JP 2022-99275 A), are printed on a substrate and then sintered to evaporate and dry the medium (ink solvent) in the ink coating and solidify the conductive particles.

[0003] On the other hand, attention is being paid to the development of conductive inks that can be used in combination with stretchable substrates. In this case, the conductive ink is required to be able to follow the expansion and contraction of the substrate and to provide good conductivity both during expansion and contraction.

[0004] For example, Patent Document 2 (JP 2023-93906 A) describes a conductive composition containing a block copolymer (E) having a weight average molecular weight of 20,000 or more and 500,000 or less, mainly composed of structural units derived from an ethylenically unsaturated monomer, and conductive fine particles (F), in order to obtain resistance to repeated stretching by suppressing the occurrence of cracks in the resin during stretching, wherein the content of the conductive fine particles (F) is 60 to 95 mass% with respect to the total solid content contained in the conductive composition, the content of chain-like silver powder (f1) among the conductive fine particles (F) is 20 mass% or more and less than 70 mass% with respect to the total solid content of the conductive composition, and the tap density of the chain-like silver powder (f1) is 2.0 g / cm 3 The following conductive compositions are disclosed: [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-99275 [Patent Document 2] Japanese Patent Application Publication No. 2023-93906 Summary of the Invention [Problem to be solved by the invention]

[0006] The conductive ink disclosed in Patent Document 1 involves a sintering process, so even if it is applied to a stretchable substrate, the conductive ink cannot follow the expansion and contraction and cannot maintain good conductivity.

[0007] The present inventors have focused on the development of conductive inks that can be used for printing on substrates that are flexible or stretchable. Here, the conductive ink is configured so that its conductivity is maintained by the deformation of the binder resin due to expansion and contraction, etc., within a range that does not interrupt the electrical chain of the conductive particles. However, it is known that the conductivity of conductive ink fluctuates (resistance value changes) when it is stretched and contracted, and that its conductivity also decreases when it is stretched and contracted repeatedly. Therefore, the technology disclosed in Patent Document 2 focuses on obtaining a conductive ink with excellent resistance to repeated stretching by comparing the initial resistance value of a test piece (stretchable conductive material) using a conductive composition with the resistance value measured in a non-stretched state after 1,000 repeated stretching cycles.

[0008] However, although there is a set range of allowable conductivity (resistance value) in actual electronic components in which conductive ink is used, with conventional conductive inks, sufficient consideration has not been given to the change in the difference between the resistance value when stretched and the resistance value when contracted. Therefore, the present inventors focused on a new problem of achieving good conductive stability by preventing the difference between the resistance value of the conductive ink when it is stretched and the resistance value when it is contracted from increasing due to repeated stretching. [Means for solving the problem]

[0009] The inventors have conducted extensive research to obtain good conductive stability by minimizing the change in the resistance value of the conductive ink and the difference in the resistance value between expansion and contraction during repeated stretching. As a result, they have discovered that it is effective to use chain-like silver particles and control the crystallite size obtained from powder X-ray diffraction measurements of silver microparticles, and have completed the present invention.

[0010] According to the present invention, the following conductive ink and related techniques are provided.

[0011] [1] A conductive ink containing silver particles and a resin, which is used for printing on a substrate having at least one of flexibility and stretchability, The conductive ink, wherein the silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement. [2] The conductive ink according to [1], The tap density of the silver particles is 1.3 g / cm 3 More than 1.6g / cm 3 The following is a conductive ink. [3] The conductive ink according to [1] or [2], The specific surface area of ​​the silver particles (BET method) is 3.5 m 2 / g or more, 5.5m 2 / g or less. [4] The conductive ink according to any one of [1] to [3], The conductive ink has a particle size (average particle size D50) corresponding to a cumulative 50% of the volume-based integrated fraction of the silver particles as determined by a laser diffraction method of 4.5 μm or more and 6.5 μm or less. [5] The conductive ink according to any one of [1] to [4], A conductive ink in which the ratio of the particle size (average particle size D50; μm) corresponding to a cumulative 50% of the volume-based cumulative fraction of the silver particles measured by a laser diffraction method to the crystallite size (nm) of the silver particles is 0.12 or more and 0.30 or less. [6] The conductive ink according to any one of [1] to [5], The resin is a conductive ink containing one or more resins selected from the group consisting of polyurethane resin, polystyrene resin, acrylic resin, polycarbonate resin, polyamide resin, polyamideimide resin, and thermoplastic elastomer. [7] The conductive ink according to any one of [1] to [6], The conductive ink, wherein the silver particles are a mixture containing silver particles (A1) having a crystallite size of 25 nm or more and 30 nm or less, and silver particles (A2) having a crystallite size of more than 30 nm and 50 nm or less. [8] The conductive ink according to any one of [1] to [7], The silver particles have a specific surface area (BET method) of 4 m 2 / g, 6m 2 / g or less silver particles (B1) and a specific surface area (BET method) of 2m 2 / g or more, 4m 2 and silver particles (B2) in an amount of 1000 to 10 ... [9] The conductive ink according to any one of [1] to [8], A conductive ink, wherein the content of the silver particles is 70% by mass or more and 90% by mass or less with respect to the total amount (solid content) of the conductive ink.

[10] The conductive ink according to any one of [1] to [9], Conductive ink used in screen printing.

[11] A conductive printed matter using the conductive ink described in any one of [1] to

[10] .

[12] A conductor comprising a substrate having at least one of flexibility and stretchability, and the conductive ink according to any one of [1] to

[10] printed on the substrate.

[13] An electronic device comprising the conductor according to

[12] .

[14] A method for producing a conductive ink containing silver particles and a resin, the conductive ink being used for printing on a substrate having at least one of flexibility and stretchability, comprising: mixing the silver particles with the resin, A method for producing a conductive ink, wherein the silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement.

[15] A method for producing the conductive ink according to

[14] , In the mixing step, A method for producing a conductive ink, comprising mixing the silver particles (A1) having a crystallite size of 25 nm or more and 30 nm or less, the silver particles (A2) having a crystallite size of more than 30 nm and 50 nm or less, and the resin.

[16] A method for manufacturing a conductor, comprising: A step of printing the conductive ink according to any one of [1] to

[10] on a substrate having at least one of flexibility and stretchability; a step of drying the printed film obtained by the printing to obtain a conductive film; A method for producing a conductor, comprising:

[17] A method for producing the conductor according to

[16] , A method for producing a conductor, wherein a screen printing method is used in the step of printing the conductive ink. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a conductive ink that exhibits good conductivity stability even when stretched or contracted. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a graph showing the resistance values ​​measured in the non-stretched and stretched states in the stretching cycle of the tensile test in the evaluation of the conductivity stability of Example 1. FIG. [Figure 2] 10 is a graph showing the resistance values ​​measured in the non-stretched and stretched states in the stretching cycle of the tensile test in the evaluation of the conductivity stability of Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this specification, the expression "a to b" in the description of a numerical range means from a to b, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% to 5 mass%." Furthermore, the lower limit and upper limit of a numerical range can be arbitrarily combined with the lower limit and upper limit of another numerical range.

[0015] Unless otherwise specified, each of the components and materials exemplified in this specification may be used alone or in combination of two or more.

[0016] In this specification, the term "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0017] In this specification, the crystallite size of silver particles is defined as a value calculated using the following Scherrer formula (1) from the half-width β (rad) of the peak of the plane with plane index (1,1,1) obtained by powder X-ray diffraction measurement using CuKα radiation as a radiation source. D = Kλ / (βcosθ) (1) (where K is the Scherrer constant and λ is the wavelength of the X-rays used) D: Crystallite size K: Scherrer constant = 0.94 λ: wavelength of X-ray used, CuKα ray 0.154nm θ: Bragg angle (rad)

[0018] In this specification, the specific surface area of ​​silver particles is a value measured by the BET method.

[0019] In this specification, the average particle size D50 of silver particles refers to the particle size corresponding to 50% of the cumulative volume-based integrated fraction determined by the particle laser diffraction scattering method in accordance with JIS R 1629: 1997. Distilled water is used as the solvent, and the powder is ultrasonically dispersed in a sample circulator that is a standard accessory to the instrument, after which the particle size is measured.

[0020] In this specification, the tap density of silver particles is defined as the tap density of a volume of 20 cm 3The value is measured from the bulk (volume) when 15 g of silver powder is placed in the cell container, and the tap stroke is 10 mm and the number of taps is 1,500. The device that can be used is the Multitester MT-1000 functional powder property measuring instrument (manufactured by Seishin Enterprise Co., Ltd.).

[0021] Hereinafter, embodiments of the present invention will be described in detail.

[0022] <Conductive ink> The conductive ink of this embodiment contains silver particles and a resin, and is used for printing on a substrate that is flexible or stretchable, and the silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement. This allows a conductive printed item using the conductive ink of this embodiment to have good conductivity both when stretched and when contracted.

[0023] The details of the reason for this are not clear, but it is speculated as follows. First, the conductive particles in the stretchable conductive ink are not sintered and are designed to be able to conform to the stretchable substrate together with the binder resin. However, when conductive printed materials using conventional conductive inks are repeatedly stretched and used over a long period of time, the stretching causes the conductive particles to peel off from the binder resin, resulting in the formation of voids (vacuum voids).Further repeated stretching also stretches these voids, causing the contact points between the conductive particles to separate and resulting in an increase in resistance. In response to this issue, the inventors conducted extensive research and found that the use of chain-like silver particles of a specific crystallite size effectively suppresses the occurrence of the above-mentioned voids and maintains stable conductivity both during contraction and extension. In other words, by forming silver particles into a chain of a specific crystallite size, cohesive forces act between the silver particles, making it easier to maintain contact between the silver particles during both contraction and expansion, thereby suppressing the occurrence of voids. As a result, it is possible to obtain a low volume resistivity while also achieving good conductive stability, thereby achieving a high level of balance between the two.

[0024] In this embodiment, the silver particles in the conductive ink are a particle group, and the physical properties of the silver particles described below are average values ​​of the particle group.

[0025] (chained) In this embodiment, the silver particles contained in the conductive ink are in a chain-like structure. A chain-like structure refers to a state in which particles are linked together and aggregate to a certain extent, and the direction, length, number, etc. of the chain are not particularly limited. The chain-like silver particles may be either linked in a continuous chain or branched, with dendritic branching being preferred. Alternatively, the silver particles may be in the shape of a bunch of grapes, with numerous aggregates gathering together. The chain structure of the silver particles can be confirmed by scanning electron microscopy.

[0026] (crystallite size) The crystallite size of the silver particles obtained by powder X-ray diffraction measurement is 25 nm or more and 37 nm or less. This reduces the degree to which the conductivity of the conductive ink changes when it is expanded and when it is contracted, resulting in good conductivity stability.

[0027] The crystallite size of the silver particles is preferably 26 nm or more, and more preferably 27 nm or more. On the other hand, the crystallite size of the silver particles is preferably 36 nm or less, and more preferably 35 nm or less. By adjusting the crystallite size of the silver particles to the above lower limit or more, the conductivity of the silver particles can be improved. On the other hand, by setting the crystallite size of the silver particles to the above upper limit or less, deformation and fluctuation of the resin present between the silver particles can be suppressed, thereby reducing voids caused by deformation and fluctuation of the resin and making it easier to maintain good conductivity against elongation.

[0028] (tap density) In this embodiment, chain-like silver particles tend to be bulky because they are made up of numerous agglomerates that resemble a bunch of grapes. Therefore, the low tap density of silver particles means that the silver particles tend to be bulky and that the silver particles are chain-like. The tap density of the silver particles is preferably 1.3 g / cm 3 More preferably, it is 1.4 g / cm or more. 3 That's all. On the other hand, the tap density of the silver particles is preferably 1.6 g / cm 3 More preferably, it is 1.5 g / cm or less. 3 The following is the result. By setting the tap density of the silver particles to the above lower limit or more, the density of the silver particles in the conductive ink is increased, and the conductivity is easily improved. On the other hand, by setting the tap density of the silver particles to the above upper limit or less, the silver particles can be made to conform to expansion and contraction, and good conductivity stability can be obtained.

[0029] (specific surface area) The specific surface area of ​​the silver particles is preferably 3.5 m 2 / g or more, more preferably 3.6m 2 / g or more. On the other hand, the specific surface area of ​​the silver particles is preferably 5.5 m 2 / g or less, and more preferably 5.4m 2 / g or less. By setting the specific surface area of ​​the silver particles to the above lower limit or more, it is possible to suppress the generation of voids during expansion and contraction and improve the conductivity stability, while by setting the specific surface area of ​​the silver particles to the above upper limit or less, it is possible to suppress an increase in volume resistivity.

[0030] (Average particle size D50) The average particle size D50 of the silver particles is preferably 4.5 μm or more, and more preferably 4.6 μm or more. On the other hand, the average particle size D50 of the silver particles is preferably 6.5 μm or less, and more preferably 6.3 μm or less. By setting the average particle size D50 of the silver particles to the above lower limit or more, it is possible to improve the conductivity while maintaining good conductivity stability. On the other hand, by setting the average particle size D50 of the silver particles to the above upper limit or less, an increase in volume resistivity can be suppressed and good conductivity can be maintained.

[0031] Furthermore, in this embodiment, the ratio of the particle size (average particle size D50; μm) corresponding to a cumulative 50% of the volume-based cumulative fraction of the silver particles measured by the laser diffraction method to the crystallite size (nm) of the silver particles (average particle size D50 (μm) / crystallite size (nm)) is preferably 0.12 to 0.30, more preferably 0.13 to 0.25, and even more preferably 0.14 to 0.22. By setting this ratio (average particle size D50 (μm) / crystallite size (nm)) to the lower limit value or more, the generation of voids is suppressed and electrical conductivity stability is obtained. On the other hand, by setting the ratio (average particle size D50 (μm) / crystallite size (nm)) to the above upper limit or less, stable conductivity can be obtained.

[0032] In order to achieve silver particles with the above-mentioned crystallite size, specific surface area, tap density, and average particle size D50, it is important to select the type of silver particles, etc. For example, it is preferable to select multiple silver particles with different crystallite sizes or multiple silver particles with different specific surface areas, or to adjust the content of each type of silver particle.

[0033] The silver particles may also be a mixture containing silver particles (A1) with a crystallite size of 25 nm or more and 30 nm or less and silver particles (A2) with a crystallite size of more than 30 nm and 50 nm or less, which allows for precise control of the balance between conductivity and conformability, resulting in higher conductivity stability. Furthermore, by using silver particles with different crystallite sizes, the silver particles (A1) act to fill the gaps between the silver particles (A2) during elongation, complementing the contact points between the silver particles, making it easier to obtain good conductivity.

[0034] In this case, the crystallite size of the silver particles (A1) is more preferably 26 nm or more and 29 nm or less, and even more preferably 27 nm or more and 28 nm or less. The crystallite size of the silver particles (A2) is more preferably 35 nm or more and 45 nm or less, and even more preferably 39 nm or more and 41 nm or less.

[0035] The mass ratio of the silver particles (A1) to the silver particles (A2) (silver particles (A1):silver particles (A2)) is preferably 90:10 to 30:70, more preferably 80:20 to 40:60, and even more preferably 75:25 to 50:50.

[0036] In addition, silver particles have a specific surface area of ​​4m 2 / g, 6m 2 / g or less silver particles (B1) and a specific surface area of ​​2m 2 / g or more, 4m 2 / g or less of silver particles (B2). This allows for precise control of the balance between conductivity and conformability, resulting in higher conductivity stability.

[0037] In this case, the specific surface area of ​​the silver particles (B1) is more preferably 5.2 m 2 / g or more, 5.6m 2 / g or less. The specific surface area of ​​the silver particles (B2) is preferably 2.1 m 2 / g or more, 2.8m 2 / g or less, and more preferably 2.3m 2 / g or more, 2.5m 2 / g or less.

[0038] The mass ratio of the silver particles (B1) to the silver particles (B2) (silver particles (B1):silver particles (B2)) is preferably 90:10 to 30:70, more preferably 80:20 to 40:60, and even more preferably 75:25 to 50:50.

[0039] The content of silver particles is preferably 70% by mass or more and 90% by mass or less, more preferably 75% by mass or more and 85% by mass or less, and even more preferably 78% by mass or more and 82% by mass or less, based on the total amount (solid content) of the conductive ink. By setting the content of silver particles to the above lower limit or more, electrical continuity during elongation can be maintained, while by setting the content of silver particles to the above upper limit or less, cracking of the printed film during elongation can be suppressed.

[0040] [resin] The use of resin improves the handleability of the conductive ink, making it easier to obtain the desired printed matter, and also makes it possible to impart elasticity to the conductive ink.

[0041] The resin is not particularly limited as long as it has plasticity or elasticity, and any resin known as a conductive ink can be used. Specific examples include one or more resins selected from the group consisting of polyurethane resin, acrylic resin, polyamide resin, polyimide resin, silicone resin, and thermoplastic elastomer. Among these, acrylic resin is preferred.

[0042] (others) In addition to the silver particles and resin, the conductive ink of this embodiment may further contain known additives such as solvents, fillers, pigments, silane coupling agents, leveling agents, thixotropic agents, and antifoaming agents, depending on the application.

[0043] [Manufacturing method] The method for producing a conductive ink of this embodiment includes a step of mixing the silver particles, a resin, and other optional components. The silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement. Alternatively, silver particles (A1) having a crystallite size of 25 nm or more and 30 nm or less and silver particles (A2) having a crystallite size of more than 30 nm and 50 nm or less may be used and mixed with a resin. In addition, the above silver particles have a specific surface area of ​​4m 2 / g, 6m 2 / g or less silver particles (B1) and a specific surface area of ​​2m 2 / g or more, 4m 2 / g or less of silver particles (B2) may be used and mixed with the resin.

[0044] The mixing method is not particularly limited, and for example, the ingredients can be mixed in a known mixer such as a meteoric mixer, a dissolver, a bead mill, a Raikai mixer, a three-roll mill, a rotary mixer, or a twin-screw mixer.

[0045] [Characteristics, usage] The conductive ink of this embodiment provides good conductivity stability against expansion, contraction, and flexibility, and is therefore suitable for use in printing on substrates that have at least one of expansion and contraction properties and flexibility. As a printing method, screen printing is preferably used.

[0046] The substrate having at least one of the stretchability and flexibility is one that can be stretched and contracted, or bent or folded, in part or in whole. Among these, one that can be stretched, bent or folded repeatedly is preferred. Examples of the substrate include resin materials processed into films, sheets, fabrics, bands, fibers, woven fabrics, nonwoven fabrics, knitted fabrics, etc.; cross-linked rubber materials such as nitrile rubber, styrene rubber, chloroprene rubber, urethane rubber, butyl rubber, and natural rubber; paper; and various components having moving parts. Specific examples of the resin material include polyimide, polyethylene terephthalate (PET), polycarbonate, polyethylene naphthalate (PEN), polyketone, polyether ether ketone, thermoplastic polyurethane elastomer (TPU), and cycloolefin polymer.

[0047] <Conductive printed materials, conductors, electronic devices> Furthermore, by using the above-mentioned conductive ink, it is possible to obtain a conductive printed material, a conductor comprising a substrate having at least one of stretchability and flexibility and the above-mentioned conductive ink printed on the substrate, and an electronic device comprising a conductor. The conductive printed matter comprises at least a printed layer made of the conductive ink on a substrate. The substrate can be a substrate having at least one of the above-mentioned stretchability and flexibility. This provides good conductive stability.

[0048] In addition, the method for manufacturing a conductor of this embodiment includes a step of printing the above-mentioned conductive ink on a substrate having at least one of stretchability and flexibility, and a step of drying the printed film obtained by the printing to obtain a conductive film.

[0049] The conductive ink of this embodiment is not sintered, so it can conform well to substrates that are flexible and / or stretchable, and maintains its conductivity. This means it can also be applied to substrates with low heat resistance, increasing the degree of freedom in the design of conductive printed products. Drying is preferably carried out by heating and blowing air, and the heating temperature is preferably 80 to 150° C., and the heating time is preferably 10 to 120 minutes.

[0050] Examples of the printing method include one or more methods selected from screen printing, pad printing, stencil printing, screen offset printing, dispenser printing, gravure offset printing, reverse offset printing, and microcontact printing, and among these, screen printing is preferably used. In the screen printing method, for example, a fine mesh screen of 300 to 650 mesh can be used.

[0051] The thickness of the printed film is not particularly limited and may be adjusted appropriately depending on the desired conductivity, etc., but may be, for example, 0.5 μm to 20 μm, or 1 μm to 15 μm.

[0052] The conductor may be a product itself or may be used as a component, such as a wiring or electrode, or as an electromagnetic wave shielding layer or heat dissipation layer.

[0053] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. [Example]

[0054] Next, the present invention will be described in detail with reference to examples, but the content of the present invention is not limited to the examples.

[0055] <Examples and Comparative Examples> Conductive ink was prepared using the following raw materials and evaluated. [Raw materials] (silver particles) Silver particles 1 to 4 having the physical properties shown in Table 1 below were prepared.

[0056] [Table 1]

[0057] (binder resin) Binder resin 1: Acrylic block copolymer (MAM) "CLARITY (registered trademark)" (manufactured by Kuraray Co., Ltd.)

[0058] [Preparation of conductive ink] The binder resin was dissolved in butyl carbitol acetate to obtain the ratio (parts by mass) shown in Table 2, and the silver particles were added to the solution, which was then premixed in a planetary centrifugal mixer. The mixture was then further kneaded in a three-roll mill.

[0059] Furthermore, when the conductive inks were observed using a scanning electron microscope, it was confirmed that the silver particles in all conductive inks were in a chain form.

[0060] [evaluation] (volume resistivity) (i) Each of the obtained conductive inks was applied to a glass substrate (glass slide; 76 mm × 52 mm × 1.3 mm) by screen printing. After application, the substrate was heat-treated at 100°C for 30 minutes. The printed film had a thickness of 40 to 50 μm. The volume resistivity (Ω·cm) of the printed film was then measured by the four-probe method using a Loresta (Loresta-GP MCP-T610, manufactured by Nitto Seiko Analytech Co., Ltd.). The results are shown in Table 2.

[0061] (Conductive stability) (ii) Each of the obtained conductive inks was printed onto a polyurethane film (elastic substrate: ES85, manufactured by Okura Kogyo Co., Ltd., thickness 100 μm) in the shape of a No. 7 dumbbell test piece so that the thickness after drying would be 20 μm, and after printing, it was dried at 100 ° C for 80 minutes to obtain a printed film. The area where the printed film was formed was punched out with a punch, and this was used as a test piece (shaped like a No. 7 dumbbell test piece). A tensile test was performed on the test piece using a tensile tester (Stency, manufactured by Acroedge Co., Ltd.) connected to a resistance meter (RM3545, manufactured by Hioki E.E. Corporation), and the resistance value (Ω) of the test piece was measured. The tensile test consisted of repeating 100 cycles of 20% elongation at 50 mm / min followed by unloading at 50 mm / min. In each stretching cycle, the resistance value (Ω) fluctuation range (variable resistance value: ΔΩ) from the non-stretched state (unloaded state: initial resistance value) to the 20% stretched state (maximum resistance value) n (n is an integer between 1 and 100)) and measure the fluctuation range (variable resistance value: ΔΩ) during repeated expansion and contraction cycles. n (n is an integer of 1 to 100)) was evaluated. The first cycle was a preliminary tension to allow the test specimen to adapt to stretching. The results of the initial resistance (Ω), maximum resistance (Ω), and variable resistance (ΔΩ) at the second and 100th cycles are shown in Table 2. Furthermore, as an example, FIG. 1 shows a graph sequentially plotting the resistance values ​​measured at non-stretched and stretched states in the stretching cycle of the tensile test in the evaluation of the conductivity stability of Example 1, and FIG. 2 shows a graph sequentially plotting the resistance values ​​measured at non-stretched and stretched states in the stretching cycle of the tensile test in the evaluation of the conductivity stability of Comparative Example 2.

[0062] (iii) The rate of increase A (%) of the variable resistance (ΔΩ) between the 2nd and 100th extension / contraction cycles was calculated using the following formula. The results are shown in Table 2. Increase rate A(%)=(ΔΩ 100 / ΔΩ2)×100 As an example, in the tensile test of Example 1, the fluctuation resistance value (fluctuation range) ΔΩ2 at the second stretching cycle and the fluctuation resistance value (fluctuation range) ΔΩ at the 100th stretching cycle are shown in FIG. 100 2 shows the fluctuation resistance value (fluctuation range) ΔΩ2 at the second stretching cycle and the fluctuation resistance value (fluctuation range) ΔΩ at the 100th stretching cycle in the tensile test of Comparative Example 2. 100 showed.

[0063] (Void observation) (iv) The cross section of the printed film of the test piece after 100 stretching cycles, which was used to evaluate the electrical conductivity stability, was observed using a scanning electron microscope (5000x magnification). Furthermore, the test piece was fixed in a 20% stretched state, and the cross section when cut parallel to the stretching direction was observed using a scanning electron microscope (5000x magnification). The results of these observations were evaluated according to the following criteria. ·standard Present: Voids were observed in at least one of the observations None: No voids were observed in any of the observations.

[0064] [Table 2]

Claims

1. A conductive ink containing silver particles and a resin, the conductive ink being used for printing on a substrate having at least one of flexibility and stretchability, The conductive ink, wherein the silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement.

2. The conductive ink according to claim 1, The tap density of the silver particles is 1.3 g / cm ３ Above, 1.6g / cm ３ The following is a conductive ink.

3. The conductive ink according to claim 1 or 2, The specific surface area of ​​the silver particles (BET method) is 3.5 m ２ / g or more, 5.5m ２ / g or less.

4. The conductive ink according to claim 1 or 2, The conductive ink has a particle size (average particle size D50) corresponding to a cumulative 50% of the volume-based integrated fraction of the silver particles as determined by a laser diffraction method of 4.5 μm or more and 6.5 μm or less.

5. The conductive ink according to claim 1 or 2, a ratio of a particle size (average particle size D50; μm) corresponding to a cumulative 50% cumulative volume-based integrated fraction of the silver particles as determined by a laser diffraction method to the crystallite size (nm) of the silver particles is 0.12 or more and 0.30 or less.

6. The conductive ink according to claim 1 or 2, The resin is a conductive ink containing one or more resins selected from the group consisting of polyurethane resin, polystyrene resin, acrylic resin, polycarbonate resin, polyamide resin, polyamideimide resin, and thermoplastic elastomer.

7. The conductive ink according to claim 1 or 2, The conductive ink, wherein the silver particles are a mixture containing silver particles (A1) having a crystallite size of 25 nm or more and 30 nm or less, and silver particles (A2) having a crystallite size of more than 30 nm and 50 nm or less.

8. The conductive ink according to claim 1 or 2, The silver particles have a specific surface area (BET method) of 4 m ２ / g over 6m ２ / g or less and silver particles (B1) having a specific surface area (BET method) of 2 m ２ / g or more, 4m ２ and silver particles (B2) having a molecular weight of 1000 or less per 1000g.

9. The conductive ink according to claim 1 or 2, A conductive ink, wherein the content of the silver particles is 70% by mass or more and 90% by mass or less with respect to the total amount (solid content) of the conductive ink.

10. The conductive ink according to claim 1 or 2, Conductive ink used in screen printing.

11. A conductive printed matter using the conductive ink according to claim 1 or 2.

12. A conductor comprising a substrate having at least one of flexibility and stretchability, and the conductive ink according to claim 1 or 2 printed on the substrate.

13. An electronic device comprising the electrical conductor of claim 12.

14. A method for producing a conductive ink that contains silver particles and a resin and is used for printing on a substrate that has at least one of flexibility and stretchability, comprising: mixing the silver particles with the resin, The method for producing a conductive ink, wherein the silver particles are chain-like and have a crystallite size of 25 nm or more and 37 nm or less as determined by powder X-ray diffraction measurement.

15. A method for producing the conductive ink according to claim 14, In the mixing step, a method for producing a conductive ink, comprising mixing the silver particles (A1) having a crystallite size of 25 nm or more and 30 nm or less, the silver particles (A2) having a crystallite size of more than 30 nm and 50 nm or less, and the resin.

16. A method for manufacturing a conductor, comprising: A step of printing the conductive ink according to claim 1 or 2 on a substrate having at least one of flexibility and stretchability; a step of drying the printed film obtained by the printing to obtain a conductive film; A method for producing a conductor, comprising:

17. 17. A method for manufacturing a conductor according to claim 16, comprising: A method for producing a conductor, wherein a screen printing method is used in the step of printing the conductive ink.

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