JP7308722B2 - Conductive paste and stretchable wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive paste and a stretchable wiring board.

BACKGROUND ART In recent years, various developments have been made on materials used for wiring that constitutes a stretchable wiring board. As this type of technology, for example, the technology described in Patent Document 1 is known. According to the document, it is described that a binder rubber polymer and a conductive powder were mixed at a ratio of 2:8 (weight ratio), dispersed with a three-roll mill, and then the viscosity was adjusted with a solvent to obtain a conductive paste. (Paragraph 0037 of Patent Document 1). In the same document, irregular silver particles (SF-70, manufactured by Ferro Japan Co., Ltd., aspect ratio 5, density 10.5 g/cm ³ ) having an average particle size of about 1 to 5 μm are used as the conductive powder. Are listed.

JP 2015-55615 A

However, as a result of investigation by the present inventor, it was found that the conductive paste described in the above document has room for improvement in terms of conductive stability.

As a result of further investigation by the present inventors, the conductive resin film obtained from the conductive paste by using a scale-like metal powder having a predetermined characteristic for the conductive paste containing the conductive filler It was found that the conductivity stability can be improved, and that the conductivity stability can be stably evaluated by using the tap density and average particle diameter _D50 of the scale-like metal powder as indices.
As a result of intensive studies based on such knowledge, it was found that by adopting a scale-like metal powder index (tap density and average particle diameter D ₅₀ ) in an appropriate range, wiring using a conductive paste, etc. In the conductive resin film of No. 2, it was found that the conductive stability can be improved, and the present invention was completed.

According to the invention,
A conductive paste containing an elastomer composition containing silica particles (C), a conductive filler, and a solvent, and used for forming wiring constituting a stretchable wiring board,
The conductive filler contains scale-like metal powder (G),
The content of the conductive filler is 50 % by mass or more and 85% by mass or less with respect to the entire conductive paste, and the content of the silica particles (C) is the silica particles (C) and the conductive filler. 1% by mass or more and 20% by mass or less with respect to 100% by mass of the total amount of
The content of the scale-like metal powder (G) is 90% by mass or more in 100% by mass of the conductive filler,
The scale-like metal powder (G) has a tap density of 2.80 g/cm ³ or more and 4.50 g/cm ³ or less, an average particle diameter _D50 of 2.30 μm or more and 14.0 μm or less, and a ratio A conductive paste is provided having a surface area of 2.00 m ² /g or less.

Further, according to the present invention, there is provided an elastic wiring substrate comprising a substrate and wiring, wherein the wiring is made of the elastomer of the conductive paste.

ADVANTAGE OF THE INVENTION According to this invention, the stretchable wiring board using the electrically conductive paste which can implement|achieve the electrically conductive resin film excellent in electrical conductivity stability and the same is provided.

It is a sectional view showing an outline of an electronic device in this embodiment. 4A to 4C are cross-sectional views showing the outline of the manufacturing process of the electronic device according to the present embodiment; It is a figure which shows the relationship between "tap density" of a metal powder (G), "average particle diameter _D50 ", and "average value ( _Rtop100 )." It is a figure which shows the relationship between the "specific surface area" of metal powder (G), "average particle diameter _D50 ", and "average value ( _Rtop100 )."

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In addition, in this specification, unless otherwise specified, "-" represents from the above to the following.

The conductive paste of this embodiment can contain an elastomer composition, a conductive filler, and a solvent. In the conductive paste, the conductive filler has a tap density of 2.80 g/cm ³ or more and 4.50 g/cm ³ or less and an average particle size _D50 of 2.30 μm or more and 14.0 μm or less. of metal powder (G). Since such a conductive paste can realize a conductive resin film with excellent conductive stability, it can be used to form wiring that constitutes an elastic wiring board.

Since the conductive paste of the present embodiment is composed of a paste-like conductive resin composition containing a solvent, it has excellent coatability and film-forming properties on the substrate, and is also excellent in printability such as screen printing. ing. Therefore, the conductive paste of the present embodiment is suitable for use in forming wiring that constitutes an elastic wiring board, for example.

Each component of the conductive paste of this embodiment will be described below.

The conductive paste of this embodiment can contain an elastomer composition. As a result, even when an elastomer made of a conductive paste is used for wiring or the like, the elastomer can exhibit appropriate stretchability.

The elastomer composition is used to form the above elastomer, and for example, a thermosetting composition used to form one or more thermosetting elastomers selected from the group consisting of silicone rubber, urethane rubber, and fluororubber. It may contain an elastomer composition, preferably a silicone rubber-based curable composition.

(elastomer)
Silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber and the like can be used as the elastomer. Among these, the elastomer can include one or more thermosetting elastomers selected from the group consisting of silicone rubber, urethane rubber, and fluororubber. In addition, the elastomer can contain silicone rubber from the viewpoint of being chemically stable and having excellent mechanical strength.
The thermosetting elastomer can be composed of a cured product of a thermosetting elastomer composition. For example, the silicone rubber can be composed of a cured product of a silicone rubber-based curable composition. The thermoplastic elastomer can be composed of a dried thermoplastic elastomer. In this specification, the elastomer of the conductive paste means an elastomer formed by drying or curing the conductive paste.

A case where a silicone rubber-based curable composition is used as the silicone rubber, which is an example of the elastomer of the present embodiment, will be described below.

The silicone rubber-based curable composition of the present embodiment can contain a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber-based curable composition of the present embodiment.

The vinyl group-containing organopolysiloxane (A) can contain a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, and the vinyl groups serve as crosslinking points during curing.

The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it preferably has two or more vinyl groups in the molecule and is 15 mol % or less. , 0.01 to 12 mol %. As a result, the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) is optimized, and a network can be reliably formed with each component described later. In the present embodiment, "~" means including both numerical values.

In the present specification, the vinyl group content is the mol % of the vinyl group-containing siloxane units when the total units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mol %. . However, one vinyl group is considered to be one vinyl group-containing siloxane unit.

The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is, for example, preferably in the range of about 1,000 to 10,000, more preferably in the range of about 2,000 to 5,000. The degree of polymerization can be determined, for example, as a polystyrene-equivalent number-average polymerization degree (or number-average molecular weight) in GPC (gel permeation chromatography) using chloroform as a developing solvent.

Furthermore, the specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of about 0.9 to 1.1.

As the vinyl group-containing linear organopolysiloxane (A1), the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber can be improved by using those having the degree of polymerization and specific gravity within the ranges described above. can be improved.

As the vinyl group-containing linear organopolysiloxane (A1), those having a structure represented by the following formula (1) are particularly preferred.

In formula (1), R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group of a combination thereof having 1 to 10 carbon atoms. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferred. The alkenyl group having 1 to 10 carbon atoms includes, for example, vinyl group, allyl group, butenyl group, etc. Among them, vinyl group is preferred. The aryl group having 1 to 10 carbon atoms includes, for example, a phenyl group.

R ² is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, or a hydrocarbon group combining these. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups and butenyl groups. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

R ³ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group combining these. The alkyl group having 1 to 8 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

Furthermore, examples of substituents for R ¹ and R ² in formula (1) include methyl group and vinyl group, and examples of substituents for R ³ include methyl group.

In formula (1), a plurality of R ¹ are independent of each other and may be different from each other or may be the same. Furthermore, the same applies to R ² and R ³ .

Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), m is an integer of 0 to 2000, and n is 1000 to 10000. is an integer of m is preferably 0-1000 and n is preferably 2000-5000.

Further, specific structures of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include, for example, those represented by the following formula (1-1).

In formula (1-1), R ¹ and R ² are each independently a methyl group or a vinyl group, and at least one is a vinyl group.

Furthermore, as the vinyl group-containing linear organopolysiloxane (A1), a first vinyl group-containing vinyl group having a vinyl group content of 2 or more vinyl groups in the molecule and not more than 0.4 mol% It contains a linear organopolysiloxane (A1-1) and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol%. It is preferable to have As crude rubber, which is a raw material of silicone rubber, a first vinyl group-containing linear organopolysiloxane (A1-1) having a general vinyl group content and a second vinyl group-containing linear organopolysiloxane having a high vinyl group content were used. By combining with the chain organopolysiloxane (A1-2), the vinyl groups can be unevenly distributed, and the crosslink density can be more effectively formed in the crosslink network of the silicone rubber. As a result, the tear strength of silicone rubber can be increased more effectively.

Specifically, as the vinyl group-containing linear organopolysiloxane (A1), for example, a unit in which R ¹ is a vinyl group and/or a unit in which R ² is a vinyl group in the above formula (1-1) , a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more in the molecule and containing 0.4 mol% or less, and a unit in which R ¹ is a vinyl group and / or R It is preferable to use a second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol % of units in which ² is a vinyl group.

The first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol %. The second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of 0.8 to 12 mol %.

Furthermore, when combining the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2), (A1-1) and (A1-2) is not particularly limited, but for example, the weight ratio of (A1-1):(A1-2) is preferably 50:50 to 95:5, and 80:20 to 90: 10 is more preferred.

The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may be used singly or in combination of two or more. good.

The vinyl group-containing organopolysiloxane (A) may also contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<<Organohydrogenpolysiloxane (B)>>
The silicone rubber-based curable composition of the present embodiment can contain an organohydrogenpolysiloxane (B).
Organohydrogenpolysiloxane (B) is classified into linear organohydrogenpolysiloxane (B1) having a linear structure and branched organohydrogenpolysiloxane (B2) having a branched structure. Either or both may be included.

The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure (≡Si—H) in which hydrogen is directly bonded to Si, and is the vinyl group-containing organopolysiloxane (A). It is a polymer that undergoes a hydrosilylation reaction with vinyl groups other than vinyl groups contained in other components of the silicone rubber-based curable composition, thereby cross-linking these components.

The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited.

The weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by polystyrene conversion in GPC (gel permeation chromatography) using chloroform as a developing solvent.

Also, the straight-chain organohydrogenpolysiloxane (B1) generally preferably does not have a vinyl group. Thereby, it is possible to accurately prevent the progress of the cross-linking reaction in the molecule of the linear organohydrogenpolysiloxane (B1).

As the linear organohydrogenpolysiloxane (B1) as described above, for example, one having a structure represented by the following formula (2) is preferably used.

In formula (2), R ⁴ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, a hydrocarbon group combining these groups, or a hydride group. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups and butenyl groups. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

R ⁵ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, a hydrocarbon group combining these, or a hydride group. Examples of the alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group and propyl group, with methyl group being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups and butenyl groups. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In formula (2), a plurality of R ⁴ are independent of each other and may be different from each other or may be the same. The same is true for ^R5 . However, at least two or more of the plurality of R ⁴ and R ⁵ are hydride groups.

R ⁶ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group combining these. The alkyl group having 1 to 8 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferred. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. A plurality of R ⁶ are independent from each other and may be different from each other or may be the same.

Examples of substituents for R ⁴ , R ⁵ and R ⁶ in formula (2) include methyl group and vinyl group, with methyl group being preferred from the viewpoint of preventing intramolecular cross-linking reaction.

Further, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), m is an integer of 2 to 150, and n is an integer of 2 to 150. is. Preferably, m is an integer from 2-100 and n is an integer from 2-100.

In addition, linear organohydrogenpolysiloxane (B1) may be used individually by 1 type, and may be used in combination of 2 or more types.

Since the branched organohydrogenpolysiloxane (B2) has a branched structure, it is a component that forms regions with a high crosslink density and greatly contributes to the formation of a loose and dense crosslink density structure in the silicone rubber system. Further, like the linear organohydrogenpolysiloxane (B1), it has a structure (≡Si—H) in which hydrogen is directly bonded to Si, and in addition to the vinyl group of the vinyl group-containing organopolysiloxane (A), silicone It is a polymer that undergoes a hydrosilylation reaction with the vinyl groups of the components blended in the rubber-based curable composition to crosslink these components.

Further, the branched organohydrogenpolysiloxane (B2) has a specific gravity in the range of 0.9 to 0.95.

Furthermore, it is generally preferred that the branched organohydrogenpolysiloxane (B2) does not have a vinyl group. Thereby, it is possible to accurately prevent the progress of the cross-linking reaction in the molecule of the branched organohydrogenpolysiloxane (B2).

As the branched organohydrogenpolysiloxane (B2), those represented by the following average compositional formula (c) are preferred.

Average composition formula (c)
(H _a (R ⁷ ) _3-a SiO _1/2 ) _m (SiO _4/2 ) _n
(In formula (c), R ⁷ is a monovalent organic group, a is an integer ranging from 1 to 3, m is the number of H _a (R ⁷ ) _3-a SiO _1/2 units, n is SiO _4/ is a number of ₂ units)

In formula (c), R ⁷ is a monovalent organic group, preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an aryl group, or a hydrocarbon group combining these. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si) and is an integer in the range of 1-3, preferably 1.

In formula (c), m is the number of H _a (R ⁷ ) _3-a SiO _1/2 units, and n is the number of SiO _4/2 units.

The branched organohydrogenpolysiloxane (B2) has a branched structure. The linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) differ in that their structures are linear or branched. The number of bound alkyl groups R (R/Si) is 1.8 to 2.1 for the linear organohydrogenpolysiloxane (B1) and 0.8 to 1 for the branched organohydrogenpolysiloxane (B2). .7 range.

Since the branched organohydrogenpolysiloxane (B2) has a branched structure, for example, when heated to 1000° C. at a heating rate of 10° C./min in a nitrogen atmosphere, the residual amount is 5% or more. becomes. On the other hand, since the straight-chain organohydrogenpolysiloxane (B1) is straight-chain, the amount of residue after heating under the above conditions is almost zero.

Specific examples of the branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3).

In formula (3), R ⁷ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, a hydrocarbon group combining these, or a hydrogen atom. The alkyl group having 1 to 8 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferred. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. Examples of the substituent of ^R7 include a methyl group and the like.

In formula (3), a plurality of R ⁷ are independent of each other and may be different from each other or may be the same.

In formula (3), "--O--Si.ident." represents that Si has a branched structure extending three-dimensionally.

The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more.

Moreover, in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2), the amount of hydrogen atoms (hydride groups) directly bonded to Si is not particularly limited. However, in the silicone rubber-based curable composition, linear organohydrogenpolysiloxane (B1) and branched organohydrogenpolysiloxane are The total amount of hydride groups in the siloxane (B2) is preferably from 0.5 to 5 mol, more preferably from 1 to 3.5 mol. As a result, a crosslinked network is reliably formed between the linear organohydrogenpolysiloxane (B1), the branched organohydrogenpolysiloxane (B2), and the vinyl group-containing linear organopolysiloxane (A1). can be made

In the present embodiment, the content of the elastomer composition in the conductive paste is preferably 1% by mass or more, more preferably 3% by mass or more, and 5% by mass with respect to the entire conductive paste. It is more preferable that it is above. In addition, the content of the elastomer composition in the conductive paste is preferably 25% by mass or less, more preferably 20% by mass or less, and 15% by mass or less with respect to the entire conductive paste. is more preferred.
By setting the content of the elastomer composition to the above lower limit or more, the elastomer of the conductive paste can have appropriate flexibility. Further, by setting the content of the elastomer composition to the above upper limit or less, the mechanical strength of the elastomer can be improved.

<<Silica particles (C)>>
The conductive paste of the present embodiment can contain silica particles (C), if necessary. Thereby, the hardness and mechanical strength of the elastomer formed from the conductive paste can be improved.

By containing silica particles in addition to the conductive filler, the conductive paste of the present embodiment can improve the mechanical strength and durability of the elastomer composed of the cured conductive paste and the like. By applying an elastomer made of such a conductive paste to a conductive resin film such as wiring constituting a stretchable wiring board, the mechanical strength and durability of the conductive resin film can be improved. As a result, it is possible to enhance the stretchable electrical properties of the stretchable wiring board including the wiring formed of the conductive paste of the present embodiment.

Silica particles (C) are not particularly limited, but for example, fumed silica, pyrogenic silica, precipitated silica and the like are used. These may be used alone or in combination of two or more.

The silica particles (C) preferably have a BET specific surface area of, for example, 50 to 400 m ² /g, more preferably 100 to 400 m ² /g. Also, the average primary particle size of the silica particles (C) is preferably, for example, 1 to 100 nm, more preferably about 5 to 20 nm.

By using silica particles (C) having a specific surface area and an average particle size within the above ranges, the hardness and mechanical strength of the silicone rubber formed can be improved, particularly the tensile strength can be improved.

In the present embodiment, the content of the silica particles (C) in the conductive paste is preferably 1% by mass or more, more preferably 2% by mass or more, relative to the entire conductive paste. It is more preferably 3% by mass or more. In addition, the content of the silica particles (C) in the conductive paste is preferably 15% by mass or less, more preferably 12% by mass or less, and 10% by mass with respect to the entire conductive paste. More preferably:
By making the content of the silica particles (C) equal to or higher than the above lower limit, the elastomer of the conductive paste can have an appropriate mechanical strength. Moreover, by setting the content of the silica particles (C) to the above upper limit or less, the elastomer can have appropriate conductive properties.

<<Silane coupling agent (D)>>
The silicone rubber-based curable composition of the present embodiment can contain a silane coupling agent (D).
Silane coupling agent (D) can have a hydrolyzable group. The hydrolyzable group is hydrolyzed with water to form a hydroxyl group, and the hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particle (C), thereby modifying the surface of the silica particle (C).

Moreover, this silane coupling agent (D) can contain a silane coupling agent having a hydrophobic group. As a result, the hydrophobic group is imparted to the surface of the silica particles (C), so that the cohesive force of the silica particles (C) in the silicone rubber-based curable composition and further in the silicone rubber is reduced (hydrogen aggregation due to bonding is reduced), and as a result, it is presumed that the dispersibility of the silica particles in the silicone rubber-based curable composition is improved. This increases the interface between the silica particles and the rubber matrix, increasing the reinforcing effect of the silica particles. Furthermore, it is presumed that the slipperiness of the silica particles in the matrix is improved when the rubber matrix is deformed. The improved dispersibility and slipperiness of the silica particles (C) improve the mechanical strength (for example, tensile strength and tear strength) of the silicone rubber due to the silica particles (C).

Furthermore, the silane coupling agent (D) can contain a silane coupling agent having a vinyl group. As a result, vinyl groups are introduced onto the surfaces of the silica particles (C). Therefore, during curing of the silicone rubber-based curable composition, that is, a hydrosilylation reaction occurs between the vinyl group of the vinyl group-containing organopolysiloxane (A) and the hydride group of the organohydrogenpolysiloxane (B). , When a network (crosslinked structure) is formed by these, the vinyl groups possessed by the silica particles (C) also participate in the hydrosilylation reaction with the hydride groups possessed by the organohydrogenpolysiloxane (B). Silica particles (C) also come to be taken in. As a result, it is possible to reduce the hardness and increase the modulus of the formed silicone rubber.

As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination.

Examples of the silane coupling agent (D) include those represented by the following formula (4).

_Yn -Si-(X) _4-n (4)
In the above formula (4), n represents an integer of 1-3. Y represents a functional group having a hydrophobic group, a hydrophilic group or a vinyl group, and when n is 1 it is a hydrophobic group, and when n is 2 or 3 at least one of It is a hydrophobic group. X represents a hydrolyzable group.

The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group having a combination thereof, and examples thereof include a methyl group, an ethyl group, a propyl group, a phenyl group, and the like. Methyl groups are preferred.

Moreover, the hydrophilic group includes, for example, a hydroxyl group, a sulfonic acid group, a carboxyl group, a carbonyl group, etc. Among them, a hydroxyl group is particularly preferable. The hydrophilic group may be contained as a functional group, but is preferably not contained from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Further, the hydrolyzable group includes an alkoxy group such as a methoxy group and an ethoxy group, a chloro group, a silazane group, and the like. Among them, a silazane group is preferable because of its high reactivity with the silica particles (C). A compound having a silazane group as a hydrolyzable group has two structures of (Y _n —Si—) in the above formula (4) due to its structural characteristics.

Specific examples of the silane coupling agent (D) represented by the above formula (4) include, for example, those having a hydrophobic group as a functional group, such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, Alkoxysilanes such as ethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; methyltrichlorosilane; chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane; hexamethyldisilazane; alkoxysilanes such as propylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane, vinylmethyldichlorosilane; Among them, hexamethyldisilazane is particularly preferable as one having a hydrophobic group, and divinyltetramethyldisilazane as one having a vinyl group, in view of the above description.

In the present embodiment, the lower limit of the content of the silane coupling agent (D) is preferably 1% by mass or more with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). It is more preferably at least 5% by mass, even more preferably at least 5% by mass. In addition, the upper limit of the content of the silane coupling agent (D) is preferably 100% by mass or less, and 80% by mass or less with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). It is more preferable that the content is 40% by mass or less.
By setting the content of the silane coupling agent (D) to the above lower limit or more, the elastomer of the conductive paste has appropriate adhesion to the substrate, and when silica particles (C) are used, the elastomer It can contribute to improvement in mechanical strength as a whole. Moreover, by setting the content of the silane coupling agent (D) to the above upper limit or less, the elastomer can have appropriate mechanical properties.

<<platinum or platinum compound (E)>>
The silicone rubber-based curable composition of this embodiment can contain platinum or a platinum compound (E).
Platinum or a platinum compound (E) is a catalytic component that acts as a catalyst during curing. The amount of platinum or platinum compound (E) added is a catalytic amount.

As the platinum or platinum compound (E), a known one can be used, for example, platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcohol solution of chloroplatinic acid, A complex salt of platinic acid and olefin, a complex salt of chloroplatinic acid and vinyl siloxane, and the like are included.

In addition, platinum or a platinum compound (E) may be used individually by 1 type, and may be used in combination of 2 or more type.

In the present embodiment, the content of platinum or platinum compound (E) in the conductive paste is preferably 0.0001% by mass or more, and 0.0002% by mass or more with respect to the entire conductive paste. more preferably 0.0003% by mass or more. In addition, the content of platinum or platinum compound (E) in the conductive paste is preferably 1% by mass or less, more preferably 0.5% by mass or less, relative to the entire conductive paste. , 0.1% by mass or less.
By setting the content of platinum or platinum compound (E) to the above lower limit or more, the conductive paste can be cured at an appropriate speed. Moreover, by making the content of platinum or platinum compound (E) equal to or less than the above upper limit value, it is possible to contribute to the reduction of the cost when producing the conductive paste.

<<Water (F)>>
Further, the silicone rubber-based curable composition of the present embodiment may contain water (F) in addition to the above components (A) to (E).

Water (F) is a component that functions as a dispersion medium for dispersing each component contained in the silicone rubber-based curable composition and contributes to the reaction between the silica particles (C) and the silane coupling agent (D). . Therefore, the silica particles (C) and the silane coupling agent (D) can be linked to each other more reliably in the silicone rubber, and uniform properties can be exhibited as a whole.

Furthermore, when water (F) is contained, its content can be appropriately set, specifically, for 100 parts by weight of the silane coupling agent (D), for example, 10 to 100 parts by weight and more preferably 30 to 70 parts by weight. This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

(other ingredients)
Furthermore, the silicone rubber-based curable composition of the present embodiment may further contain other components in addition to the above components (A) to (F). Other components include silica particles (C) such as diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, and mica. additives such as inorganic fillers, reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers.

(Conductive filler)
The conductive paste of this embodiment can contain a conductive filler. As this conductive filler, a known conductive material may be used, and the following metal powder (G) may be included. These may be used alone or in combination of two or more.

The conductive filler has a tap density of 2.80 g/cm ³ or more and 4.50 g/cm ³ or less, and an average particle size D ₅₀ of 2.30 μm or more and 14.0 μm or less. Metal powder (G) can be used. Thereby, the conductive stability in the conductive resin film obtained from the conductive paste can be improved during repeated stretching.

Further, the conductive filler further satisfies the condition B that the specific surface area is 0.50 m ² /g or more and 2.00 m ² /g or less and the average particle size _D50 is 2.30 μm or more and 10.0 μm or less. Scale-like metal powder (G) can be used. As a result, it is possible to realize a conductive resin film excellent in durability without deterioration in conductivity during stretching and releasing after repeated stretching tests.

The average particle diameter _D50 of the scale-like metal powder (G) is, for example, 2.30 μm or more and 14.0 μm or less, more preferably 2.30 μm or more and 10.0 μm or less, and still more preferably It is 3.00 μm or more and 9.40 μm or less.
The average particle size _D50 of the metal powder (G) is the 50% particle size measured with a laser diffraction particle size analyzer. It is the particle size at the point where the particle size is cumulatively 50% by mass from the smaller particle size in the volume-based particle size distribution.

The tap density of the scale-like metal powder (G) is, for example, 2.80 g/cm 3 or more and 4.50 g/cm ³ or less, preferably 3.20 g/cm ^{3 or} more and 4.05 g/cm 3 or more. ³ or less, more preferably 3.30 g/cm ³ or more and 4.00 g/cm ³ or less.
The tap density of the metal powder (G) is measured in accordance with ISO 3953-1985(E) "Metal powder - Method for measuring tap density".

The specific surface area of the scale-like metal powder (G) is, for example, 0.50 m ² /g or more and 2.00 m 2 /g or less, preferably 0.51 ^{m 2 /} g or more and 1.80 m ^{2 /} g. g or less, more preferably 0.52 m ² /g or more and 1.60 m ² /g or less.
The specific surface area of the metal powder (G) is the BET specific surface area measured using an automatic specific surface area measuring device.

As the metal powder (G), other than the scale-like metal powder (G) may be contained. The shape of the other metal powder (G) is not limited, but conventionally used shapes such as dendritic and spherical can be used.

The metal constituting the metal powder (G) is not particularly limited. or, alternatively, two or more of these.
Among these, the metal powder (G) preferably contains silver or copper, that is, contains silver powder or copper powder, because of its high conductivity and high availability.
These metal powders (G) may be coated with other kinds of metals.

In the present embodiment, the content of the conductive filler in the conductive paste is preferably 30% by mass or more, more preferably 40% by mass or more, and 50% by mass with respect to the entire conductive paste. % or more is more preferable. In addition, the content of the conductive filler in the conductive paste is preferably 85% by mass or less, more preferably 75% by mass or less, and 65% by mass or less with respect to the entire conductive paste. It is even more preferable to have
By setting the content of the conductive filler to the above lower limit or more, the elastomer of the conductive paste can have appropriate conductive properties. Also, by setting the content of the conductive filler to the above upper limit or less, the elastomer can have appropriate flexibility.

The content of the metal powder (G) is, for example, 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more with respect to 100% by mass of the conductive filler, On the other hand, it may be 100% by mass or less.

Further, the lower limit of the content of the silica particles (C) in the conductive paste of the present embodiment is, for example, 1% by mass or more with respect to 100% by mass of the total amount of the silica particles (C) and the conductive filler. , preferably 3% by mass or more, and more preferably 5% by mass or more. Thereby, the mechanical strength of the elastomer of the conductive paste can be improved. On the other hand, the upper limit of the content of the silica particles (C) in the conductive paste is, for example, 20% by mass or less with respect to 100% by mass of the total amount of the silica particles (C) and the conductive filler. , preferably 15% by mass or less, more preferably 10% by mass or less. Thereby, it is possible to achieve a balance between the stretchable electrical properties and the mechanical strength of the elastomer of the conductive paste.

(solvent)
The conductive paste of this embodiment contains a solvent. As this solvent, various known solvents can be used, and for example, a high boiling point solvent can be included. These may be used alone or in combination of two or more.

The lower limit of the boiling point of the high boiling point solvent is, for example, 100° C. or higher, preferably 130° C. or higher, and more preferably 150° C. or higher. As a result, the printing stability of screen printing or the like can be improved. On the other hand, the upper limit of the boiling point of the high boiling point solvent is not particularly limited, but may be, for example, 300° C. or lower, 290° C. or lower, or 280° C. or lower. As a result, excessive heat history during wiring formation can be suppressed, so damage to the underlying substrate and the shape of the wiring formed with the conductive paste can be maintained favorably.

The solvent of the present embodiment can be appropriately selected from the viewpoint of the solubility and boiling point of the elastomer composition. Aliphatic hydrocarbons, more preferably aliphatic hydrocarbons having 10 to 15 carbon atoms can be included.

Examples of the solvent of the present embodiment include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; benzene, toluene, ethylbenzene, and xylene. , trifluoromethylbenzene, aromatic hydrocarbons such as benzotrifluoride; diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, 1,4- ethers such as dioxane, 1,3-dioxane and tetrahydrofuran; haloalkanes such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane and 1,1,2-trichloroethane; Carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxides such as dimethylsulfoxide and diethylsulfoxide; These may be used alone or in combination of two or more.
The solvent used here may be appropriately selected from solvents capable of uniformly dissolving or dispersing the components in the conductive paste.

The lower limit of the viscosity of the conductive paste when measured at a room temperature of 25° C. and a shear rate of 20 [1/s] is, for example, 1 Pa·s or more, preferably 5 Pa·s or more, and more preferably 10 Pa·s. s or more. Thereby, the film formability can be improved. In addition, it is possible to improve shape retention even when forming a thick film. On the other hand, the upper limit of the viscosity of the conductive paste at room temperature of 25° C. is, for example, 100 Pa·s or less, preferably 90 Pa·s or less, and more preferably 80 Pa·s or less. Thereby, the printability of the conductive paste can be improved.

(Method for producing conductive paste)
A method for producing a conductive paste according to this embodiment will be described below.

The conductive paste of this embodiment can be manufactured, for example, through the steps shown below.

First, each component of the silicone rubber-based curable composition is uniformly mixed using any kneading device to prepare the silicone rubber-based curable composition.

[1] For example, a vinyl group-containing organopolysiloxane (A), silica particles (C), and a silane coupling agent (D) are weighed in predetermined amounts, and then kneaded with an arbitrary kneading device, A kneaded material containing these components (A), (C) and (D) is obtained.

The kneaded product is preferably obtained by previously kneading the vinyl group-containing organopolysiloxane (A) and the silane coupling agent (D), and then kneading (mixing) the silica particles (C). This further improves the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A).

Further, when obtaining this kneaded product, water (F) may be added to the kneaded product of each component (A), (C), and (D), if necessary. This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

Further, the kneading of the components (A), (C) and (D) is preferably carried out through a first step of heating at a first temperature and a second step of heating at a second temperature. As a result, in the first step, the surface of the silica particles (C) can be surface-treated with the coupling agent (D), and in the second step, the silica particles (C) and the coupling agent (D) By-products generated in the reaction can be reliably removed from the kneaded material. After that, if necessary, the component (A) may be added to the obtained kneaded product and further kneaded. This makes it possible to improve the familiarity of the components of the kneaded product.

The first temperature is preferably, for example, about 40 to 120.degree. C., and more preferably, for example, about 60 to 90.degree. The second temperature is, for example, preferably about 130 to 210.degree. C., more preferably about 160 to 180.degree.

Moreover, the atmosphere in the first step is preferably an inert atmosphere such as a nitrogen atmosphere, and the atmosphere in the second step is preferably a reduced-pressure atmosphere.

Furthermore, the time for the first step is preferably, for example, about 0.3 to 1.5 hours, more preferably about 0.5 to 1.2 hours. The time for the second step is, for example, preferably about 0.7 to 3.0 hours, more preferably about 1.0 to 2.0 hours.

By setting the first step and the second step under the above conditions, the above effect can be obtained more significantly.

[2] Next, the organohydrogenpolysiloxane (B) and the platinum or platinum compound (E) are weighed in predetermined amounts, and then the kneaded product prepared in the above step [1] using any kneading device. Then, components (B) and (E) are kneaded to obtain a silicone rubber-based curable composition (elastomer composition).

When kneading the components (B) and (E), the kneaded product previously prepared in the above step [1] and the organohydrogenpolysiloxane (B) were prepared in the above step [1]. It is preferable to knead the kneaded material with platinum or the platinum compound (E), and then knead the respective kneaded materials. This ensures that each component (A) to (E) is contained in the silicone rubber-based curable composition without allowing the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) to proceed. can be distributed in

The temperature at which the components (B) and (E) are kneaded is preferably, for example, about 10 to 70°C, more preferably about 25 to 30°C, as the set temperature of the rolls.

Further, the kneading time is preferably about 5 minutes to 1 hour, more preferably about 10 to 40 minutes.

In the steps [1] and [2], the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) proceeds more accurately by setting the temperature within the above range. can be prevented or suppressed; In addition, by setting the kneading time within the above range in steps [1] and [2], each component (A) to (E) can be more reliably dispersed in the silicone rubber-based curable composition. can be done.

The kneading device used in steps [1] and [2] is not particularly limited, but for example, a kneader, two rolls, a Banbury mixer (continuous kneader), a pressure kneader, etc. can be used.

In step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded product. As a result, even if the temperature of the kneaded product is set to a relatively high temperature, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more accurately prevented or suppressed. be able to.

[3] Next, the elastomer composition (silicone rubber-based curable composition) obtained in step [2] is dissolved in a solvent, and metal powder (G) is added to obtain the conductive paste of the present embodiment. can be obtained.

[Use]
An example of the application of the conductive paste of this embodiment will be described below with reference to FIG. FIG. 1 shows a schematic cross-sectional view of an electronic device 100 having such wiring.

The electronic device 100 can include a wiring substrate 50 and an electronic component 60, as shown in FIG. The wiring board 50 is configured by providing the wiring 10 on the board 20 . As the substrate 20, an elastic insulating substrate can be used. On the other hand, the wiring 10 can be made of the conductive paste elastomer of the present embodiment (specifically, a cured product obtained by curing the conductive paste). The electronic component 60 may be configured to be electrically connected to the wiring 10 forming such an elastic wiring board (wiring board 50).

The conductive paste of the present embodiment can maintain the electrical properties of expansion and contraction when repeatedly expanded and contracted while increasing the mechanical strength of the resulting cured product, so it has excellent connection reliability and durability. The structure of the device 100 can be realized.
The electronic device 100 of this embodiment is used as, for example, a wearable device, and can be suitably used as a device that repeatedly expands and contracts in each direction.

Also, the substrate 20 that constitutes the electronic device 100 of the present embodiment is normally made of a flexible material.
As this material, the same material as the elastomer described above can be employed. Specifically, elastomers such as silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, and ethylene propylene rubber can be used, and this material can be appropriately selected according to the application. can. Further, the substrate 20 may be composed of a cured product of the silicone rubber-based curable composition described above.

Also, the substrate 20 can be made of an elastomer made of the elastomer composition described above. Moreover, this elastomer may be configured using an insulating paste containing an elastomer composition containing silica particles and a solvent. As this solvent, the same solvent species as those described above can be used, but among these, a solvent that exhibits solubility in the conductive paste or the conductive sheet that is a cured product of the conductive paste is used. be able to. As a specific solvent for the insulating paste, for example, a high boiling point solvent or the like can be used.

Further, the electronic component 60 may be appropriately selected from known components depending on the application. Specifically, semiconductor elements, and resistors and capacitors other than semiconductor elements can be used. Examples of semiconductor elements include transistors, diodes, LEDs, and capacitors. In the electronic device 100 of this embodiment, the electronic component 60 is electrically connected by the wiring 10 .

Further, the electronic device 100 of the present embodiment may be provided with a cover material 30 if necessary. By providing this cover material 30, it is possible to prevent the wiring 10 and the electronic component 60 from being damaged. The cover material 30 may be configured to cover the electronic component 60 and the wiring 10 on the substrate 20 .
Also, the cover material 30 can be made of the same material as the substrate 20 . Since the cover material 30 follows expansion and contraction of the substrate 20 and the wiring 10, the electronic device 100 as a whole can be expanded and contracted evenly, and the life of the electronic device 100 can be extended.

Next, an example of the manufacturing process of the electronic device 100 of this embodiment will be described with reference to FIG.
FIG. 2 is a cross-sectional view showing an outline of the manufacturing process of the electronic device 100 according to this embodiment.

First, as shown in FIG. 2A, a support 120 is placed on a workbench 110, and an insulating paste 130 is applied onto the support 120. Then, as shown in FIG. Various methods can be used as the coating method, and for example, a printing method such as a squeegee method using a squeegee 140 can be used. The coating of insulating paste 130 can then be dried to form an insulating layer 132 (a dry insulating sheet) on the support 120 . The drying conditions can be appropriately set according to the type and amount of the solvent in the insulating paste 130. For example, the drying temperature can be set to 150° C. to 180° C., and the drying time can be set to 1 minute to 30 minutes. can.

Subsequently, as shown in FIG. 2B, a mask 160 having a predetermined opening pattern shape is placed on the insulating layer 132 . Then, as shown in FIGS. 2B and 2C, a conductive paste 150 is applied onto the insulating layer 132 through a mask 160. Then, as shown in FIGS. As a coating method, the same technique as the coating method of the insulating paste 130 can be used, and for example, squeegee printing using a squeegee 140 may be used. Here, when the insulating paste 130 and the conductive paste 150 each contain a thermosetting elastomer composition, a conductive coating film (conductive layer 152) having a predetermined pattern shape is laminated on the dried insulating layer 132. Afterwards, these may be collectively cured. The curing treatment can be appropriately set according to the thermosetting elastomer composition. For example, the curing temperature can be 160° C. to 220° C., and the curing time can be 1 hour to 3 hours. After or before curing, the mask 160 can be removed as shown in FIG. 2(d). As a result, wiring, which is the cured product of the conductive layer 152 and has a predetermined pattern shape, can be formed on the substrate composed of the cured product of the insulating layer 132 .

Subsequently, as shown in FIG. 2(e), an insulating paste 170 is applied on the insulating layer 132 and the patterned conductive layer 152, and the insulating layer 172 is formed as shown in FIG. 2(f). can be formed. These steps may be repeated as appropriate. It is also possible to separate the support 120 from the insulating layer 132 .
As described above, the electronic device 100 shown in FIG. 2(f) can be obtained.

If an insulating sheet is used instead of the insulating paste, the process may start from the step shown in FIG. 2(b). That is, after an insulating sheet is placed on the support 120 and dried to a predetermined degree, the conductive paste 150 may be applied onto the insulating sheet through the mask 160 . Subsequent steps can be performed according to the steps described above. Thereby, it is possible to obtain the electronic device 100 shown in FIG.

It should be noted that the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

Materials used in Examples and Comparative Examples are as follows.

(Vinyl group-containing organopolysiloxane (A))
(A1-1): First vinyl group-containing linear organopolysiloxane: vinyl group content is 0.13 mol%, Mn = 227,734, Mw = 573,903, IV value (dl/g) = 0.89), and a vinyl group-containing dimethylpolysiloxane (structure represented by the above formula (1-1)) synthesized according to Synthesis Scheme 1 below.
(A1-2): Second vinyl group-containing linear organopolysiloxane: vinyl group content is 0.92 mol%, vinyl group-containing dimethylpolysiloxane synthesized according to the following synthesis scheme 2 (the above formula (1- 1) structure in which R ¹ and R ² are vinyl groups)

(Organohydrogenpolysiloxane (B))
(B): Organohydrogenpolysiloxane: “88466” manufactured by Momentive

(Silica particles (C))
(C): Silica fine particles (particle diameter 7 nm, specific surface area 300 m ² /g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL 300"

(Silane coupling agent (D))
(D): Hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)"

(Platinum or platinum compound (E))
(E): Platinum compound, PLATINUM DIVINYLTERAMETHYLDISILOXANE COMPLEX (in xylene) (manufactured by Gelest, trade name “SIP6831.2”)

(Water (F))
(F): pure water

(Additive)
(Reaction inhibitor 1): 1-ethynyl-1-cyclohexanol (manufactured by Tokyo Chemical Industry Co., Ltd.)

(Metal powder (G))
Table 1 shows the metal powders G1 to G10 used in each example and each comparative example.

The average particle size D ₅₀ , specific surface area, and tap density in Table 1 were measured as follows.
The average particle size _D50 of the metal powder (G) was the 50% particle size measured with a laser diffraction particle size analyzer (SALD-3000J, manufactured by Shimadzu Corporation). It is the particle size at the point where the particle size is cumulatively 50% by mass from the smaller particle size in the volume-based particle size distribution.
The specific surface area of the metal powder (G) was the BET specific surface area measured using an automatic specific surface area measuring device (manufactured by Shimadzu Corporation, product name: Flowsorb 2300).
The tap density of the metal powder (G) was measured in accordance with ISO 3953-1985(E) "Metal powder-Method for measuring tap density".

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis Scheme 1: Synthesis of First Vinyl Group-Containing Linear Organopolysiloxane (A1-1)]
A first vinyl group-containing linear organopolysiloxane (A1-1) was synthesized according to the following formula (7).
That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask having a cooling tube and a stirring blade, which was replaced with Ar gas, and the temperature was raised to 120° C. for 30 minutes. Stirred. At this time, an increase in viscosity was confirmed.
After that, the temperature was raised to 155° C. and stirring was continued for 3 hours. After 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added, and the mixture was further stirred at 155° C. for 4 hours.
Furthermore, after 4 hours, it was diluted with 250 mL of toluene and then washed with water three times. The washed organic layer was washed several times with 1.5 L of methanol for reprecipitation purification to separate the oligomer and polymer. The obtained polymer was dried under reduced pressure at 60° C. overnight to obtain the first vinyl group-containing linear organopolysiloxane (A1-1) (Mw=573,903, Mn=227,734). Also, the vinyl group content calculated by H-NMR spectrum measurement was 0.13 mol %.

[Synthesis Scheme 2: Synthesis of Second Vinyl Group-Containing Linear Organopolysiloxane (A1-2)]
In the above synthesis step (A1-1), 0.7 g (252 mmol) of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane was added to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane. A second vinyl group-containing linear organopolysiloxane (A1-2 ) was synthesized. Also, the vinyl group content calculated by H-NMR spectrum measurement was 0.92 mol %.

[Preparation of conductive paste]
(Preparation of silicone rubber-based curable composition 1)
A silicone rubber-based curable composition 1 was prepared as follows. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (F) is pre-kneaded in the proportions shown in Table 2 below, and then silica particles ( C) was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after the addition of the silica particles (C) includes a first step of kneading for 1 hour under a nitrogen atmosphere at 60 to 90° C. for the coupling reaction, and removal of the by-product (ammonia). For this purpose, a second step of kneading for 2 hours under a reduced pressure atmosphere at 160 to 180 ° C. is performed, followed by cooling, and the remaining 10% of the vinyl group-containing organopolysiloxane (A) is added twice. Add in portions and knead for 20 minutes.
Subsequently, organohydrogenpolysiloxane (B), platinum or platinum compound (E), and reaction inhibitor 1 were added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) in the proportions shown in Table 2 below. and kneaded with a roll to obtain a silicone rubber-based curable composition 1 (elastomer composition 1).

<Examples 1 to 4: Conductive pastes 1 to 4>
13.7 parts by weight of the obtained silicone rubber-based curable composition 1 (elastomer composition 1) was immersed in 31.8 parts by weight of tetradecane (solvent), and then stirred with a rotation/revolution mixer. Liquid conductive pastes 1 to 4 were obtained by adding 5 parts by weight of the metal powder (G) shown in Table 3 and kneading the mixture with a triple roll.

<Comparative Examples 1 to 6: Conductive pastes 5 to 10>
13.7 parts by weight of the obtained silicone rubber-based curable composition 1 (elastomer composition 1) was immersed in 31.8 parts by weight of tetradecane (solvent), and then stirred with a rotation/revolution mixer. Liquid conductive pastes 5 to 10 were obtained by adding 5 parts by weight of the metal powder (G) shown in Table 3 and then kneading the mixture with a triple roll.

[Evaluation of conductive paste]
The obtained conductive pastes 1 to 10 were evaluated according to the following evaluation items. Evaluation results are shown in Tables 3 and 4.

(Resistance value measurement)
The obtained silicone rubber-based curable composition 1 (elastomer composition 1) was cured at 170° C. for 120 minutes and molded into a sheet, which was made of silicone rubber and had a width of 2 cm×height of 500 μm×length of 5 cm. A "substrate" was produced.
Subsequently, using the conductive pastes 1 to 10 obtained in each example and each comparative example, a wiring pattern is drawn on the obtained "substrate", which is cured at 170 ° C. for 120 minutes, A test piece having a wiring pattern of width 500 μm×height 50 μm×length 30 mm was prepared.
For this test piece, using a DC voltage/current source/monitor (6241A) manufactured by ADC Co., Ltd., the resistance was measured while being stretched by 20% in 3 seconds, held for 10 seconds, and A test of releasing the extension and holding it for 10 seconds was performed 100 times.
Changes in this resistance value (Ω) were constantly monitored and analyzed for changes during this test.

"Average value of the peak top of the resistance value generated from the start of stretching from the 1st to the 100th time to the end of release (R _top100 )" is defined as the "maximum value of 100 times of 20% stretching (average value)", and "100th time The resistance value (R _ex100 ) at the end of the extension of 100 times of 20%" is set to "resistance in the state of stretching 100 times (average value)", and the "resistance value (R _re100 ) at the end of the release of the 100th extension" is set to "20 % elongation 100 times release state resistance (average value)". The resistance value (R _ex100 ) and the resistance value (R _re100 ) were measured for three samples, and the average value of the three values was used as the measured value.

Further, in the conductive pastes _{of each example and each comparative example, FIG .} , “specific surface area” and “average particle size D ₅₀ ” and “average value (R _top100 )” are shown in FIG.
Regarding the "average value (R _top100 )" in FIGS. 3 and 4, 10 to 99 Ω are indicated by "●", 100 to 999 Ω are indicated by "▴", 1000 to 9999 Ω are indicated by "x", and 10000 to 11000 Ω are indicated by "-".
The encircling line in FIG. 3 indicates that the metal powder (G) has a tap density of 2.80 g/cm ³ or more and 4.50 g/cm ³ or less and an average particle diameter _D50 of 2.30 μm or more and 14.0 μm or less. indicates the region where The enclosure line in FIG. 4 indicates that the metal powder (G) has a specific surface area of 0.50 m ² /g or more and 2.00 m ² /g or less and an average particle size _D50 of 2.30 μm or more and 10.0 μm or less. indicate the area.

It was found that the conductive pastes of Examples 1 to 4 can realize conductive resin films with excellent conductive stability because the maximum resistance value during repeated stretching tests is smaller than that of Comparative Examples 1 to 6. Therefore, it was found that the conductive pastes of Examples 1 to 4 are suitably used for devices that are repeatedly stretched, specifically stretchable wiring.
Among these, the conductive pastes of Examples 1, 2, and 4 are superior to the conductive paste of Example 3 in conductivity when stretched after repeated stretching tests and in conductivity when released from stretching. It was found that a conductive resin film having excellent properties can be realized.

10 wiring 20 substrate 30 cover material 50 wiring substrate 60 electronic component 100 electronic device 110 workbench 120 support 130 insulating paste 132 insulating layer 140 squeegee 150 conductive paste 152 conductive layer 160 mask 170 insulating paste 172 insulating layer

Claims (9)

A conductive paste containing an elastomer composition containing silica particles (C), a conductive filler, and a solvent, and used for forming wiring constituting a stretchable wiring board,
The conductive filler contains scale-like metal powder (G),
The content of the scale-like metal powder (G) is 50% by mass or more and 85% by mass or less with respect to the entire conductive paste, and the content of the silica particles (C) is the silica particles (C) and 1% by mass or more and 20% by mass or less with respect to 100% by mass of the total amount of the conductive filler,
The content of the scale-like metal powder (G) is 90% by mass or more in 100% by mass of the conductive filler,
The scale-like metal powder (G) has a tap density of 2.80 g/cm ³ or more and 4.50 g/cm ³ or less, an average particle diameter _D50 of 2.30 μm or more and 14.0 μm or less, and a ratio a surface area of 2.00 m ² /g or less ,
The average value of the maximum value of 100 times of 20% elongation, measured according to the following procedure, is 10 to 999 Ω.
conductive paste.
(procedure)
A substrate of width 2 cm×height 500 μm×length 5 cm made of silicone rubber is prepared.
Using the conductive paste, a wiring pattern is drawn on the substrate and cured at 170° C. for 120 minutes to prepare a test piece having a wiring pattern of width 500 μm×height 50 μm×length 30 mm.
Using a DC voltage/current source/monitor, the test piece is stretched 20% in the length direction for 3 seconds while measuring the resistance, held for 10 seconds, released from the stretch at 3 seconds, and held for 10 seconds. 100 times.
The average value of the peak tops of the resistance values of the test piece that occur from the start of the 1st to 100th extension to the end of the release is defined as the "average value of the 100 maximum values of 20% extension". The conductive paste according to claim 1,
A conductive paste, wherein the conductive filler contains scale-like metal powder (G) having a specific surface area of 0.50 m ² /g or more and an average particle size D ₅₀ of 2.30 μm or more and 10.0 μm or less. The conductive paste according to claim 1 or 2,
A conductive paste, wherein the elastomer composition comprises a thermosetting elastomer composition for forming one or more elastomers selected from the group consisting of silicone rubber, urethane rubber, and fluororubber. The conductive paste according to any one of claims 1 to 3 ,
A conductive paste, wherein the elastomer composition comprises a silicone rubber-based curable composition. The conductive paste according to claim 4 ,
A conductive paste, wherein the silicone rubber-based curable composition contains a vinyl group-containing organopolysiloxane (A). The conductive paste according to claim 4 or 5 ,
A conductive paste, wherein the silicone rubber-based curable composition further contains an organohydrogenpolysiloxane (B). The conductive paste according to any one of claims 4 to 6 ,
A conductive paste, wherein the silicone rubber-based curable composition further contains platinum or a platinum compound (E). The conductive paste according to any one of claims 1 to 7 ,
A conductive paste, wherein the content of the elastomer composition is 1% by mass or more and 25% by mass or less with respect to the entire conductive paste. An elastic wiring board comprising a substrate and wiring, wherein the wiring is composed of the conductive paste elastomer according to any one of claims 1 to 8 .

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